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Vulnerability Assessment of Potential Occurrence of Stratospheric
Intrusion in United States through Topographic
and Meteorological Characteristics
Project Report
ENV6932: Global Air Pollutants
Kalaivanan Murthy
8545-1118
STRUCTURE
The ‘author’ in this paper refers to the author of this document.
The author has not plotted any ‘original’ graphical representation, hence the document does not
contain any graphics except for elevation profile. It is attached in appendix and not in any of
main sections because the author has not fully researched about topology impacts.
It is recommended to refer glossary if the reader finds any difficulty in understanding
meteorology terms in this document. The glossary is authors own interpretation from definitions
from multiple sources.
As a prerequisite, the author would like to say that the boundaries between troposphere,
tropopause and stratosphere are not perfectly spherical. They experience fast moving winds and
thermal circulations which makes the boundary surface undulated.
The author would also like to say that, in the context of weather system, literally ‘nothing’ can be
more severe than two air masses of different temperatures. It should also be noted that it will not
‘mix’ easily.
It was only after 1950, scientists started studying upper-level frontogenesis using potential
vorticity as a representative quantity. The forerunners of this concept were Edward
Kleinschmidt, Richard J. Reed and Edwin M. Danielsen. Their findings were helpful for this
work.
Few additional reports were very helpful. The report titled ‘Atmospheric Ozone 1985’ (Chapter-
5) by National Aeronautics and Space Administration has a detailed documentation on
Stratospheric Tropospheric Exchange. The compilation and summary work by M.A. Shapiro and
Daniel Keyser titled ‘Fronts, Jetstreams and the Tropopause’ (1990) was helpful to understand
the dynamics of upper troposphere.
The author would like to acknowledge this work to above scientists and other pioneers who
made significant contributions in this field.
LIST OF CONTENTS
1. Abstract
2. Introduction
3. Importance of this study
4. Methodology and Literature review
5. Results
6. Discussion
7. References
8. Acknowledgement
9. Annexure-1: topology factor
10. Glossary
1
ABSTRACT
Stratospheric Intrusions are episodic events that diffuses stratospheric air mass to troposphere
thus increasing tropospheric ozone concentration since ozone is high in stratosphere. It is caused
when tropospheric folds lose stability and diffuses stratospheric air mass. Characteristics of
stratospheric air mass strikingly differs from tropospheric air mass. One such character is
potential vorticity which depends on potential temperature of air mass and earth’s spin. By
analyzing this magnitude a model can be generated which can project the likelihood of such
occurrence. This likelihood varies with time but time variability is not accounted here. The study
area considered is United States. It is split into grids of finite area and potential vorticity is
computed for each grid. The likelihood factor for each grid can be estimated and probability of
such occurrences for future time can be formulated.
INTRODUCTION
Stratosphere. Stratosphere is a part of atmosphere that extends roughly from 10 km to 50 km
above the ground. It is approximately 40 km thick. It has two distinctive features: a very high
ozone concentration and vertical static stability. Stratosphere has 90% of atmospheric ozone. Its
concentration varies by over two orders in twenty kilometers and reaches as high as 12,000 ppb
at higher altitudes. (source: NOAA[1]
). It is because of this ozone, high energy ultraviolet rays
(UV-B and UV-C) from sun are filtered from reaching the troposphere and planetary boundary
layer. The amount of ozone increases with height up to 32 km (from ground) and then decreases.
As the ozone absorbs ultraviolet radiation, it gets hotter and thus, in stratosphere, temperature
increases proportionally with height. Due to this temperature inversion there is no vertical
movement of air and thus static stability is observed in stratosphere. In the paper by Lin et al.
(2012)[2]
, it says that stratosphere also has small amounts of carbon monoxide and it is dryer
compared to troposphere.
Troposphere. Below the stratosphere lies troposphere, the part of atmosphere that supports many
life forms on earth. Ground-level ozone mixing ratios range from 20 ppb to 60 ppb[3]
, which is
very less compared to stratosphere. As ozone is detrimental to all life forms, regulations are
imposed on its ambient concentration. World Health Organization[4]
advises to limit 8h average
concentration to 100 µg/m3
(mixing ratio of 50 ppb approximately). US National Ambient Air
Quality Standards[5]
limits its 8h average concentration to 70 ppb. It can be noted that the
2
regulations at ground level are less than a hundred parts per billion while stratosphere has
thousand parts per billion. But the exchange of gases between them is very rare because of the
presence of the boundary layer called tropopause. The reason is tropopause has a positive
adiabatic lapse rate while the layer beneath, the troposphere, has negative adiabatic lapse rate.
The magnitude of lapse rate is also very low for the updraft (upward vertical movement of air) to
take place.
Tropopause. The tropopause lies at an altitude of 8 km in poles to 18 km in equator[6]
. In pressure
terms it corresponds to 450 mb and 100 mb respectively. The striking features across tropopause
are: ozone mixing ratio reduces by an order in magnitude across the boundary from stratosphere
to troposphere. For instance, the mixing ratio at tropopause is 250 ppb[7]
. Few kilometers above
the mixing ratio is 500 ppb and few kilometers below the mixing ratio is 50 ppb. However these
values fluctuate. Ideally, the contrast will be higher without absence of any exchange of air mass
between stratosphere and troposphere.
Stratospheric Tropospheric Exchange. Despite the presence of tropopause, exchange of air and
air-borne particles between stratosphere and troposphere is not uncommon. Such an exchange of
air mass between stratosphere and troposphere is known as stratospheric tropospheric exchange.
That encompasses two process: the transport of air from stratosphere to troposphere and the
transport of air from troposphere to stratosphere. The former happens in extratropical region and
is called as stratospheric intrusion. The latter happens predominantly in tropical region.
Stratospheric Intrusion. Stratospheric Intrusion is the phenomenon of diffusion of stratospheric
air mass into troposphere as a result of collapse of tropopause fold. The term stratospheric
tropospheric transport is also used to denote the one way irreversible movement of air from
stratosphere to troposphere (Lefohn et al. 2011[8]
). As noted above, due to high levels of ozone in
stratosphere, transport of air from stratosphere to troposphere elevates ground-level ozone
concentration. It is more frequently observed in late winter and early spring.
IMPORTANCE OF THIS STUDY
Impact of Ozone. As noted above, due to presence of excessive ozone in stratosphere, any
transport of air from stratosphere to troposphere elevates the ground-level ozone concentration.
Author Lin et al. (2012) states that a stratospheric intrusion can elevate the maximum daily 8h
3
average ozone by 20-40 ppb in parts of Western United States. Anenberg (2010)[12]
estimates the
likely health burden for increases in ozone, and it is evident that a 10 ppb increase results in 4%
increase in health burden.
Ozone Enhancement Events in Past. In the past it was noticed that ozone enhancement was not
always due to stratospheric intrusions. It can happen due to, but not limited to, any of these:
excessive anthropogenic emissions, wildfires, malfunctioning of monitoring systems, extreme
weather events and intercontinental transport. Some of the instances are reported in this
document. The Department of Environmental Quality, Wyoming[9]
has reported one such event.
On July 14, 2012 enhanced ozone concentration was observed in Boulder and Big Piney (state of
Colorado, United States). To confirm that it is due to stratospheric intrusion, and not due to any
other incident, evidences were collected to support the four required tests A-D under 40 CFR
50.14 (3)(iii) including quality insurance of monitoring systems. Then it was confirmed to be due
to stratospheric intrusion. Another event was noted by National Research Council[10]
. On April
25, 2004 enhancements in ozone concentrations was observed at Mt. Bachelor (state of Oregon,
United States). However from the analysis of tracer compounds, this was found to be as a result
of long range transport from Asia and not due to stratospheric intrusion.
Regulation Policies. Since high concentrations of ozone are undesirable it is necessary to identify
the source in the event of ozone enhancement. Predicting where and when stratospheric
intrusions occur helps to understand the problem better. Ozone enhancements can also hint about
other possibilities like excessive nitrogen dioxide from anthropogenic source, excessive hydroxyl
ion concentration from biogenic source or a possibility due to long range transport mentioned
earlier. Another event is noted by Seinfeld (2012)[3]
. On September 13, 1955 Los Angeles
recorded an hourly average mixing ratio of 680 ppb, the highest in the history of North America.
But this was a result of severe smog. Ozone enhancements can also introduce statistically
significant outliers to the observed data where treatment becomes difficult. An article by Lin et
al. (2012), states that EPA formed a team to study stratospheric intrusions using a combination of
models, surface observations and satellite data. In addition, predicting stratospheric intrusion can
help Environmental Protection Agency (EPA) make amendments to Exceptional Events Rule,
2007.
METHODOLOGY and LITERATURE REVIEW
4
Modeling of a stratospheric intrusion consists of two parts: predicting tropopause folds from jet
streams (meteorology), and identifying the transported air using radiosonde (remote sensing). As
noted, the former is meteorology part–understanding the formation of upper-level fronts, jet
streams and tropopause folds–and latter is remote sensing part.
Stratospheric intrusion events that has already occurred are detected using radiosondes and other
sounding instruments. In this document, the author’s vision is to ‘predict’ an intrusion. ‘Forecast’
is a precise term. In a brief literature review conducted by author there were many discussions on
observed intrusion events i.e., analysis made after an intrusion has occurred. Prediction or
forecasting of an intrusion event lies wholly with the changes in weather systems at upper-level
tropopause. Stratospheric air mass has following features: high potential vorticity, less humidity
and high radioactivity. This is in contrast with tropospheric air mass. However to predict an
intrusion the processes at upper-level troposphere has to be understood; precisely, the conditions
that lead to formation of tropopause fold and conditions that destabilizes the fold.
First, the author would like to discuss about formation of frontogenesis in upper-level
troposphere. In 1950, it became apparent that transport across tropopause can be found by
change in potential vorticity. Ertel (1942) defined the equation for potential vorticity and is given
as;
(𝜁 𝑝 + 𝑓)
𝜕𝜃
𝜕𝑝
+ 𝐾
𝜕𝑉2
𝜕𝑝
∇ 𝑝 𝜃 = 𝑃
where 𝜁 𝑝 is vorticity, 𝑓 is Coriolis parameter, 𝑉2 is horizontal wind vector, K is unit vertical
vector, ∇𝜃 is three dimensional potential temperature gradient. The subscript p mean
measurements are made at constant pressure. The first term in equation is partial potential
vorticity, and P is the absolute potential vorticity. This equation relates the absolute potential
vorticity to thermal stability (𝜕𝜃/𝜕𝑝), vertical wind shear and horizontal potential-temperature
gradient, thus, providing a means to explain frontogenesis to observable thermal and wind
parameters[11]
. It is to be noted that when fronts are assumed to be zero-order discontinuous
surface instead of first-order discontinuous zone, the second part vanishes. This is reason why
many studies ignores the second part.
5
The author interprets the above equation as a means to find if an air mass is a part of
frontogenesis. Stratospheric air mass has a higher potential vorticity. It also has higher potential
temperature, however its change acros stratospheric-tropospheric boundary is not large and sharp
like potential vorticity. But stratospheric air mass has higher vertical gradient of potential
temperature than troposphere, and hence, it has higher thermal stability.
There were arguments if fronts were to be considered as zone with sharp temperature contrasts
(zero-order discontinuity) or as a zone with a temperature (first-order discontinuity). In the
former case it is called as frontal surface (also called as hyperbaroclinic zone) and in the latter
case it is called as frontal zone. Studies show frontal ‘zone’ that has first order discontinuities in
potential temperature is more accepted theory[15]
.
Another important point to be questioned here is estimating the stability of tropopause fold. This
is equally important as predicting a tropopause fold. One way to assess the stability is by
checking the sign (or direction) of two quantities: (𝜁 𝑝 + 𝑓) - which measures the stability of air
mass subject to horizontal displacement, and (𝜕𝜃/𝜕𝑝) - which measures the stability of air mass
subject to vertical displacement. If both quantities are positive the tropopause fold is said to be
stable. If any of the quantities is negative the fold loses stability and diffuses the air mass into
troposphere[7]
.
RESULTS
As on date, the numerical computation and results was not fully performed. Hence the author
does not wish to publish it without robust proofing.
In order to model such an event three things are necessary: the causation of the event, collection
of relevant data and establishing a model relating both. The first part–the causation–is science. It
is how well the scientific community understood the process which is expressed by a
mathematical relation connecting the dependent quantity (response) and independent variables
(explanatory) such as temperature, pressure etc. The second part–collecting data–is accomplished
by radiosonde network across study area. However limitations arise. The functional capability of
measuring instrument at cold conditions has to be thoroughly studied. However, it is also
important how the measuring instruments respond to short-wave radiation themselves. The final
part–modeling–takes into account the associated uncertainty, seasonal adjustment (such as trend,
6
seasonal, cyclical, irregular components), outliers etc. An important condition to be accounted
here is level of significance. This is set from the past observed events.
The radiosonde data can be obtained from National Oceanic and Atmospheric Administration[13]
or other sources such as University of Wyoming[14]
. Prior to using data for analysis data-
inspection and data-validation must be performed.
DISCUSSION
The numerical modeling is not fully performed to initiate a discussion. However, in this section
the author tries to discuss the assumptions under which an ideal model will be formulated.
However, the model can be made robust to address following assumptions.
Adiabatic Assumption. This is the most important assumption of all. In the above discussion it is
said that potential temperature is conserved when stratospheric air mass diffuses into
troposphere. This conservation of potential temperature is true only in adiabatic process. Air
mass in atmosphere may not always be adiabatic. When air mass is heated by radiation or
conduction it undergoes diabatic heat transfer. In such process potential temperature is not
conserved. However it can be neglected because air mainly contains diatomic molecules which
are poor radiators and absorbers of visible and infrared waves. Triatomic molecules like ozone,
and aerosols like black carbon react to these waves and hence radiates heat. However this is
usually omitted due to their negligible concentration in air mass. (Reference: Global Ozone
Research, & Monitoring Project, 1985). The author is not very clear about how conservation of
potential vorticity is related to conservation of potential temperature.
Null Viscosity Assumption. The conservation of potential vorticity also holds true only for
inviscid fluid. Air has negligible viscosity but the author does not have sufficient evidence to
assert this assumption true for ‘air mass’ too.
Invertibility Property. In addition to the property of conservation, potential temperature is said to
be invertible. The author is not clearly convinced what it means and its significance.
Diabatic Heat due to Cloud Formation. The air mass in frontal zone has water vapor. At higher
altitudes and at colder temperature the gaseous vapor condenses to form clouds where latent heat
energy is released.
7
The Nitric Oxide Excess. In another scenario if stratospheric intrusion occurs when nitric oxide
is abundant in atmosphere, the ozone enhancement cannot be observed because the reaction
between nitric oxide and ozone is almost spontaneous. Thus it masks the ozone enhancement due
to stratospheric intrusion and it cannot be fully captured.
The Potential Vorticity Approximation. The absolute potential vorticity is expressed as shown in
the equation above. An approximate method to calculate it is available in many literatures which
is also used instead of the exact method to reduce complexity. The approximate method and its
limitations are not discussed here.
8
REFERENCES
Following sources were used as a references.
[1]
Ozone in our Atmosphere:http://www.esrl.noaa.gov/csd/assessments/ozone/2002/qandas1.pdf,
Earth Systems Research Laboratory, National Oceanic and Atmospheric Administration.
[2]
Lin, M., A. M. Fiore, O. R. Cooper, L. W. Horowitz, A. O. Langford, H. Levy II, B. J.
Johnson, V. Naik, S. J. Oltmans, and C. J. Senff (2012), Springtime high surface ozone events
over the western United States: Quantifying the role of stratospheric intrusions, J. Geophys.
Res., 117, D00V22, doi:10.1029/2012JD018151.
[3]
Seinfeld, J. H., & Pandis, S. N. (2012). Atmospheric chemistry and physics: from air pollution
to climate change. John Wiley & Sons. (Chapter-6)
[4]
World Health Organization. (2006). WHO Air quality guidelines for particulate matter, ozone,
nitrogen dioxide and sulfur dioxide: global update 2005: summary of risk assessment.
[5]
National Ambient Air Quality Standards, Environmental Protection Agency:
https://www.epa.gov/criteria-air-pollutants/naaqs-table.
[6]
National Research Council (US). Committee on the Significance of International Transport of
Air Pollutants. (2010). Global Sources of Local Pollution: An Assessment of Long-Range
Transport of Key Air Pollutants to and from the United States. National Academies Press.
(Appendix B.)
[7]
Global Ozone Research, & Monitoring Project. (1985). Atmospheric ozone, 1985: assessment
of our understanding of the processes controlling its present distribution and change (Vol. 1,
Chapter-5). National Aeronautics and Space Administration.
[8]
Lefohn, A. S., Wernli, H., Shadwick, D., Limbach, S., Oltmans, S. J., & Shapiro, M. (2011).
The importance of stratospheric–tropospheric transport in affecting surface ozone concentrations
in the western and northern tier of the United States. Atmospheric Environment, 45(28), 4845-
4857.
[9]
Department of Environmental Quality/Air Quality Division, State of Wyoming (2014).
Exceptional Events Demonstration Package for the Environmental Protection Agency:
https://www.epa.gov/sites/production/ files/2015-
05/documents/june_14_2012_bigpiney_boulder_si_package.pdf
[10]
National Research Council (US). Committee on the Significance of International Transport of
Air Pollutants. (2010). Global Sources of Local Pollution: An Assessment of Long-Range
Transport of Key Air Pollutants to and from the United States. National Academies Press.
(Appendix B.)
[11]
Reed, R. J. (1955). A Study of a Characteristic Type of Upper-Level Frontogenesis. Journal
of Meteorology, 12(3), 226-237.
9
[12]
Anenberg, S. C., Horowitz, L. W., Tong, D. Q., & West, J. J. (2010). An estimate of the
global burden of anthropogenic ozone and fine particulate matter on premature human mortality
using atmospheric modeling. Environmental health perspectives, 118(9), 1189.
[13]
NOAA/ESRL Radiosonde Database, http://esrl.noaa.gov/raobs/
[14]
University of Wyoming, Wyoming Weather Lab,
http://weather.uwyo.edu/upperair/sounding.html
[15]
Shapiro, M. A., & Keyser, D. A. (1990). Fronts, jet streams, and the tropopause. US
Department of Commerce, National Oceanic and Atmospheric Administration, Environmental
Research Laboratories, Wave Propagation Laboratory.
ACKNOWLEDGEMENT
The author acknowledges this work to the course ENV6932: Global Air Pollutants: its content,
design and delivery.
10
Annexure-I: TOPOLOGY FACTOR
Topology plays a major role in atmospheric circulation and weather systems. That said a too
broad concept, however, the author has tried to explain it in brief. Mountainous region that
stretch several kilometers can affect the weather systems due to temperature inversion in valleys
and surface-level wind disturbances that subsequently affect the transport of particulate matter.
This affects the radiation distribution. However this is not a prime reason. It is because the major
drivers of stratospheric intrusion such as jet streams are synoptic weather systems while the
above factor is probably a mesoscale mechanism.
A brief literature overview of stratospheric intrusion in Europe says that many such events are
observed in Alps mountain region which extends over several hundred kilometers. However at
this moment the author is not fully convinced with the reason, hence the topological effects are
not mathematically accounted in this document.
The elevation profile of study area (United States) is graphically represented here. ESRI ArcGIS
version 10.3.1 was used to plot the raster dataset. The latitude and longitude were not shown in
the plot.
11
GLOSSARY
Except few terms, all are authors own interpretation. The author has tried best to conserve the true
meaning and its significance.
Absolute Vorticity. It is a measure of the degree of spin an air mass is subjected.
Mathematically, it is the sum of curl of velocity and twice the angular momentum of earth. This
quantity is a vector.
Air Mass. The author uses this term to represent the combined mass of air including gaseous
pollutants and aerosols.
Atmospheric Sounding. “An atmospheric sounding is a measurement of vertical distribution of
physical properties of the atmospheric column such as pressure, temperature, wind speed and
wind direction (thus deriving wind shear), liquid water content, ozone concentration, pollution,
and other properties. Such measurements are performed in a variety of ways including remote
sensing and in situ observations.” – Wikipedia.
Concentration. It is used to express the fraction of gaseous pollutant in atmosphere in terms of
mass of pollutant per unit volume of air mixture. Unlike mixing ratios, concentration value
(g/m3
) remain constant against temperature variation. (Please check definition for mixing ratios
too.)
Cut-off Low. It is a cyclone formed when fast currents of jet stream detach from their
meandering path between two troughs.
Extratropical and Tropical Cyclone. “Extra-tropical cyclone is a storm system that primarily
gets its energy from the horizontal temperature contrasts that exist in the atmosphere. Tropical
cyclones, in contrast, typically have little or no temperature differences across the storm at the
surface, and their winds are derived from the release of energy due to cloud/rain formation from
the warm moist air of the tropics. Extra-tropical cyclones have their strongest winds near the
tropopause, while tropical cyclones have their strongest winds near the earth's surface. Often, a
tropical cyclone will transform into an extra-tropical cyclone as it recurves poleward and to the
east. Occasionally, an extra-tropical cyclone will lose its frontal features, develop convection
near the center of the storm and transform into a full-fledged tropical cyclone.” – Hurricane
Research Division, NOAA. These are also known as baroclinic or mid-latitude cyclones.
Frontogenesis / Frontal Zone / Baroclinic zone. The zone of separation between warm and
cold fronts. It is a transition zone of finite width and thickness. From authors understanding,
these three terms have same meaning.
Geostrophic and Ageostrophic winds. Geostrophic winds have Coriolis force balanced by
equal and opposite pressure gradient force. In contrast, ageostrophic winds have any one of these
quantities dominant. These two terminologies applies to all fluids. This nomenclature and
principle is applicable to all fluids.
12
Hypergradient Zone. The zone where potential temperature and wind velocity drastically
changes across a finite width. In meteorology such zone occurs between wedges of warm and
cold front.
Isentropic Potential Vorticity (IPV). Generally speaking, in this context (tropopause), there is
no difference between potential vorticity and IPV. The term ‘isentropic’ is added before because
to highlight the property that air masses conserve potential temperature in adiabatic process.
(This similar to usage of terms such as conservative kinetic or conservative potential energy.)
Isentropic Surface. It is an imaginary contour surface of constant potential temperature.
Jet Streams. They are fast moving air currents flowing around earth at high altitudes (8-15 km)
and in eastward direction. There are three primary jet streams in each hemisphere: arctic, polar
and subtropical. Arctic jet-streams are observed at 70° N/S latitudes. Polar jet-streams are
observed at 45° N/S latitudes. Sub-tropical jet streams are observed at 25° N/S latitudes. The
height of occurrence increases in this order: arctic, polar and subtropical. (Source: A compilation
from National Geographic and NOAA.)
Mixing Ratio. It is used to represent the amount of gaseous pollutant in atmosphere in terms of
volume fraction. It translates to amount of the pollutant expressed in volume parts per million
parts of total air mixture. It is similar but not same as concentration since mixing ratio depends
on volume, and volume varies with temperature unless pollutant and air mixture has same
expansion ratio. For an ideal gas, ppm also means molar fraction factored by one-millionth. It is
also expressed as parts per billion.
Potential Temperature. The equivalent temperature of an air mass when it is brought down to
1000 mb pressure (ground level) adiabatically.
Potential Vorticity. It is the absolute vorticity subject to three-dimensional gradient of potential
temperature. It is a dot product of three dimensional gradient of potential temperature scaled by
specific volume and absolute vorticity. Essentially it is a scalar and usually expressed in potential
vorticity unit (1 PVU = 10-6
K m2
kg-1
s-1
).
Radiosonde. It is an instrument (telemetry) suspended by balloon in atmosphere which can
measure these variables: altitude, pressure, temperature and relative humidity. (Please check
definition for rawinsonde also.)
Rawinsonde. It is a special type of radiosonde where its location can be tracked. Thus it can
measure wind speed and direction (zonal and meridional) in addition to radiosonde quantities. It
is a portmanteau of three names: radar + wind + radiosonde.
13
Upper-level. This is not a standalone term. It is widely used before the names such as
frontogenesis and troposphere. This term denotes a region or processes happening in troposphere
in higher altitude that is in the vicinity of tropopause. The corollary to this term is surface-level.
14
ENV 6932: Manuscript Evaluation Form*
Author: Kalaivanan Murthy
Reviewer: Erick Martinez Score: 80 of 100
*Form modified from http://escholarship.org/uc/item/1200h325
1) Title. ( 0 of 1 pts.) Effective & sensible? No title yet
2) Abstract. ( 5 of 7 pts.)
(a.) Well written?
(b.) All components present? (introductory sentence, hypothesis/research question,
methods, results, conclusions, implications) results, conclusion, implications not clearly defined
Notes:
3) Introduction. (7 of 8 pts.)
(a.) Hypothesis/research question clear and presented well?
(b.) Is background information sufficient to support pretense for study? Yes, very detailed
(c.) Is information cited correctly? Some concepts may need a citation
Notes:
4) Methods. (4 of 5 pts.)
Is sufficient information presented to clearly understand how the study was conducted? What was done
for the study and what was taken from other work? Formatted correctly?
Notes: Methods still seem to represent some concepts that should be included in the introduction.
5) Results. (6 of 10 pts.)
a) Is description of results presently clearly?
not yet
b) Are figures correct?
no figures
c) Are tables correct?
no tables
d) Is sufficient and the appropriate data presented to address the hypothesis/research question?
Foundation for results laid out however require more depth
e) Formatted correctly?
Notes:
6) Discussion. (7 of 12 pts.)
a) Does the discussion follow a logical order?
not exactly, logical, but separate concepts
b) Do discussion topics relate to the hypothesis?
yes, several
c) Are the conclusions logical and supported by the data? Not yet
d) Are implications of the study presented?
not yet
e) Is the study summarized in the concluding paragraph? Not yet
f) Is there a “take-home” message? yes
Notes:
7) References. (2 of 5 pts.)
a) Are there at least 20 citations of which at least 10 are peer-reviewed? Not yet
b) Are they used correctly?
yes
c) Are they formatted correctly?
yes
d) Are they cited within the text of the paper? Not all
Notes:
8) Overall. (1 of 2 pts.)
(a.) Are grammatical errors minimized? (spelling, sentence structure etc) (b.) Is it well written and easy
to follow?
(c.) Is it formatted like a scientific manuscript?
Notes: some grammatical improvements.

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Vulnerability Assessment of Potential Occurrence of Stratospheric Intrusion in United States

  • 1. Vulnerability Assessment of Potential Occurrence of Stratospheric Intrusion in United States through Topographic and Meteorological Characteristics Project Report ENV6932: Global Air Pollutants Kalaivanan Murthy 8545-1118
  • 2. STRUCTURE The ‘author’ in this paper refers to the author of this document. The author has not plotted any ‘original’ graphical representation, hence the document does not contain any graphics except for elevation profile. It is attached in appendix and not in any of main sections because the author has not fully researched about topology impacts. It is recommended to refer glossary if the reader finds any difficulty in understanding meteorology terms in this document. The glossary is authors own interpretation from definitions from multiple sources. As a prerequisite, the author would like to say that the boundaries between troposphere, tropopause and stratosphere are not perfectly spherical. They experience fast moving winds and thermal circulations which makes the boundary surface undulated. The author would also like to say that, in the context of weather system, literally ‘nothing’ can be more severe than two air masses of different temperatures. It should also be noted that it will not ‘mix’ easily. It was only after 1950, scientists started studying upper-level frontogenesis using potential vorticity as a representative quantity. The forerunners of this concept were Edward Kleinschmidt, Richard J. Reed and Edwin M. Danielsen. Their findings were helpful for this work. Few additional reports were very helpful. The report titled ‘Atmospheric Ozone 1985’ (Chapter- 5) by National Aeronautics and Space Administration has a detailed documentation on Stratospheric Tropospheric Exchange. The compilation and summary work by M.A. Shapiro and Daniel Keyser titled ‘Fronts, Jetstreams and the Tropopause’ (1990) was helpful to understand the dynamics of upper troposphere. The author would like to acknowledge this work to above scientists and other pioneers who made significant contributions in this field. LIST OF CONTENTS 1. Abstract 2. Introduction 3. Importance of this study 4. Methodology and Literature review 5. Results 6. Discussion 7. References 8. Acknowledgement 9. Annexure-1: topology factor 10. Glossary 1
  • 3. ABSTRACT Stratospheric Intrusions are episodic events that diffuses stratospheric air mass to troposphere thus increasing tropospheric ozone concentration since ozone is high in stratosphere. It is caused when tropospheric folds lose stability and diffuses stratospheric air mass. Characteristics of stratospheric air mass strikingly differs from tropospheric air mass. One such character is potential vorticity which depends on potential temperature of air mass and earth’s spin. By analyzing this magnitude a model can be generated which can project the likelihood of such occurrence. This likelihood varies with time but time variability is not accounted here. The study area considered is United States. It is split into grids of finite area and potential vorticity is computed for each grid. The likelihood factor for each grid can be estimated and probability of such occurrences for future time can be formulated. INTRODUCTION Stratosphere. Stratosphere is a part of atmosphere that extends roughly from 10 km to 50 km above the ground. It is approximately 40 km thick. It has two distinctive features: a very high ozone concentration and vertical static stability. Stratosphere has 90% of atmospheric ozone. Its concentration varies by over two orders in twenty kilometers and reaches as high as 12,000 ppb at higher altitudes. (source: NOAA[1] ). It is because of this ozone, high energy ultraviolet rays (UV-B and UV-C) from sun are filtered from reaching the troposphere and planetary boundary layer. The amount of ozone increases with height up to 32 km (from ground) and then decreases. As the ozone absorbs ultraviolet radiation, it gets hotter and thus, in stratosphere, temperature increases proportionally with height. Due to this temperature inversion there is no vertical movement of air and thus static stability is observed in stratosphere. In the paper by Lin et al. (2012)[2] , it says that stratosphere also has small amounts of carbon monoxide and it is dryer compared to troposphere. Troposphere. Below the stratosphere lies troposphere, the part of atmosphere that supports many life forms on earth. Ground-level ozone mixing ratios range from 20 ppb to 60 ppb[3] , which is very less compared to stratosphere. As ozone is detrimental to all life forms, regulations are imposed on its ambient concentration. World Health Organization[4] advises to limit 8h average concentration to 100 µg/m3 (mixing ratio of 50 ppb approximately). US National Ambient Air Quality Standards[5] limits its 8h average concentration to 70 ppb. It can be noted that the 2
  • 4. regulations at ground level are less than a hundred parts per billion while stratosphere has thousand parts per billion. But the exchange of gases between them is very rare because of the presence of the boundary layer called tropopause. The reason is tropopause has a positive adiabatic lapse rate while the layer beneath, the troposphere, has negative adiabatic lapse rate. The magnitude of lapse rate is also very low for the updraft (upward vertical movement of air) to take place. Tropopause. The tropopause lies at an altitude of 8 km in poles to 18 km in equator[6] . In pressure terms it corresponds to 450 mb and 100 mb respectively. The striking features across tropopause are: ozone mixing ratio reduces by an order in magnitude across the boundary from stratosphere to troposphere. For instance, the mixing ratio at tropopause is 250 ppb[7] . Few kilometers above the mixing ratio is 500 ppb and few kilometers below the mixing ratio is 50 ppb. However these values fluctuate. Ideally, the contrast will be higher without absence of any exchange of air mass between stratosphere and troposphere. Stratospheric Tropospheric Exchange. Despite the presence of tropopause, exchange of air and air-borne particles between stratosphere and troposphere is not uncommon. Such an exchange of air mass between stratosphere and troposphere is known as stratospheric tropospheric exchange. That encompasses two process: the transport of air from stratosphere to troposphere and the transport of air from troposphere to stratosphere. The former happens in extratropical region and is called as stratospheric intrusion. The latter happens predominantly in tropical region. Stratospheric Intrusion. Stratospheric Intrusion is the phenomenon of diffusion of stratospheric air mass into troposphere as a result of collapse of tropopause fold. The term stratospheric tropospheric transport is also used to denote the one way irreversible movement of air from stratosphere to troposphere (Lefohn et al. 2011[8] ). As noted above, due to high levels of ozone in stratosphere, transport of air from stratosphere to troposphere elevates ground-level ozone concentration. It is more frequently observed in late winter and early spring. IMPORTANCE OF THIS STUDY Impact of Ozone. As noted above, due to presence of excessive ozone in stratosphere, any transport of air from stratosphere to troposphere elevates the ground-level ozone concentration. Author Lin et al. (2012) states that a stratospheric intrusion can elevate the maximum daily 8h 3
  • 5. average ozone by 20-40 ppb in parts of Western United States. Anenberg (2010)[12] estimates the likely health burden for increases in ozone, and it is evident that a 10 ppb increase results in 4% increase in health burden. Ozone Enhancement Events in Past. In the past it was noticed that ozone enhancement was not always due to stratospheric intrusions. It can happen due to, but not limited to, any of these: excessive anthropogenic emissions, wildfires, malfunctioning of monitoring systems, extreme weather events and intercontinental transport. Some of the instances are reported in this document. The Department of Environmental Quality, Wyoming[9] has reported one such event. On July 14, 2012 enhanced ozone concentration was observed in Boulder and Big Piney (state of Colorado, United States). To confirm that it is due to stratospheric intrusion, and not due to any other incident, evidences were collected to support the four required tests A-D under 40 CFR 50.14 (3)(iii) including quality insurance of monitoring systems. Then it was confirmed to be due to stratospheric intrusion. Another event was noted by National Research Council[10] . On April 25, 2004 enhancements in ozone concentrations was observed at Mt. Bachelor (state of Oregon, United States). However from the analysis of tracer compounds, this was found to be as a result of long range transport from Asia and not due to stratospheric intrusion. Regulation Policies. Since high concentrations of ozone are undesirable it is necessary to identify the source in the event of ozone enhancement. Predicting where and when stratospheric intrusions occur helps to understand the problem better. Ozone enhancements can also hint about other possibilities like excessive nitrogen dioxide from anthropogenic source, excessive hydroxyl ion concentration from biogenic source or a possibility due to long range transport mentioned earlier. Another event is noted by Seinfeld (2012)[3] . On September 13, 1955 Los Angeles recorded an hourly average mixing ratio of 680 ppb, the highest in the history of North America. But this was a result of severe smog. Ozone enhancements can also introduce statistically significant outliers to the observed data where treatment becomes difficult. An article by Lin et al. (2012), states that EPA formed a team to study stratospheric intrusions using a combination of models, surface observations and satellite data. In addition, predicting stratospheric intrusion can help Environmental Protection Agency (EPA) make amendments to Exceptional Events Rule, 2007. METHODOLOGY and LITERATURE REVIEW 4
  • 6. Modeling of a stratospheric intrusion consists of two parts: predicting tropopause folds from jet streams (meteorology), and identifying the transported air using radiosonde (remote sensing). As noted, the former is meteorology part–understanding the formation of upper-level fronts, jet streams and tropopause folds–and latter is remote sensing part. Stratospheric intrusion events that has already occurred are detected using radiosondes and other sounding instruments. In this document, the author’s vision is to ‘predict’ an intrusion. ‘Forecast’ is a precise term. In a brief literature review conducted by author there were many discussions on observed intrusion events i.e., analysis made after an intrusion has occurred. Prediction or forecasting of an intrusion event lies wholly with the changes in weather systems at upper-level tropopause. Stratospheric air mass has following features: high potential vorticity, less humidity and high radioactivity. This is in contrast with tropospheric air mass. However to predict an intrusion the processes at upper-level troposphere has to be understood; precisely, the conditions that lead to formation of tropopause fold and conditions that destabilizes the fold. First, the author would like to discuss about formation of frontogenesis in upper-level troposphere. In 1950, it became apparent that transport across tropopause can be found by change in potential vorticity. Ertel (1942) defined the equation for potential vorticity and is given as; (𝜁 𝑝 + 𝑓) 𝜕𝜃 𝜕𝑝 + 𝐾 𝜕𝑉2 𝜕𝑝 ∇ 𝑝 𝜃 = 𝑃 where 𝜁 𝑝 is vorticity, 𝑓 is Coriolis parameter, 𝑉2 is horizontal wind vector, K is unit vertical vector, ∇𝜃 is three dimensional potential temperature gradient. The subscript p mean measurements are made at constant pressure. The first term in equation is partial potential vorticity, and P is the absolute potential vorticity. This equation relates the absolute potential vorticity to thermal stability (𝜕𝜃/𝜕𝑝), vertical wind shear and horizontal potential-temperature gradient, thus, providing a means to explain frontogenesis to observable thermal and wind parameters[11] . It is to be noted that when fronts are assumed to be zero-order discontinuous surface instead of first-order discontinuous zone, the second part vanishes. This is reason why many studies ignores the second part. 5
  • 7. The author interprets the above equation as a means to find if an air mass is a part of frontogenesis. Stratospheric air mass has a higher potential vorticity. It also has higher potential temperature, however its change acros stratospheric-tropospheric boundary is not large and sharp like potential vorticity. But stratospheric air mass has higher vertical gradient of potential temperature than troposphere, and hence, it has higher thermal stability. There were arguments if fronts were to be considered as zone with sharp temperature contrasts (zero-order discontinuity) or as a zone with a temperature (first-order discontinuity). In the former case it is called as frontal surface (also called as hyperbaroclinic zone) and in the latter case it is called as frontal zone. Studies show frontal ‘zone’ that has first order discontinuities in potential temperature is more accepted theory[15] . Another important point to be questioned here is estimating the stability of tropopause fold. This is equally important as predicting a tropopause fold. One way to assess the stability is by checking the sign (or direction) of two quantities: (𝜁 𝑝 + 𝑓) - which measures the stability of air mass subject to horizontal displacement, and (𝜕𝜃/𝜕𝑝) - which measures the stability of air mass subject to vertical displacement. If both quantities are positive the tropopause fold is said to be stable. If any of the quantities is negative the fold loses stability and diffuses the air mass into troposphere[7] . RESULTS As on date, the numerical computation and results was not fully performed. Hence the author does not wish to publish it without robust proofing. In order to model such an event three things are necessary: the causation of the event, collection of relevant data and establishing a model relating both. The first part–the causation–is science. It is how well the scientific community understood the process which is expressed by a mathematical relation connecting the dependent quantity (response) and independent variables (explanatory) such as temperature, pressure etc. The second part–collecting data–is accomplished by radiosonde network across study area. However limitations arise. The functional capability of measuring instrument at cold conditions has to be thoroughly studied. However, it is also important how the measuring instruments respond to short-wave radiation themselves. The final part–modeling–takes into account the associated uncertainty, seasonal adjustment (such as trend, 6
  • 8. seasonal, cyclical, irregular components), outliers etc. An important condition to be accounted here is level of significance. This is set from the past observed events. The radiosonde data can be obtained from National Oceanic and Atmospheric Administration[13] or other sources such as University of Wyoming[14] . Prior to using data for analysis data- inspection and data-validation must be performed. DISCUSSION The numerical modeling is not fully performed to initiate a discussion. However, in this section the author tries to discuss the assumptions under which an ideal model will be formulated. However, the model can be made robust to address following assumptions. Adiabatic Assumption. This is the most important assumption of all. In the above discussion it is said that potential temperature is conserved when stratospheric air mass diffuses into troposphere. This conservation of potential temperature is true only in adiabatic process. Air mass in atmosphere may not always be adiabatic. When air mass is heated by radiation or conduction it undergoes diabatic heat transfer. In such process potential temperature is not conserved. However it can be neglected because air mainly contains diatomic molecules which are poor radiators and absorbers of visible and infrared waves. Triatomic molecules like ozone, and aerosols like black carbon react to these waves and hence radiates heat. However this is usually omitted due to their negligible concentration in air mass. (Reference: Global Ozone Research, & Monitoring Project, 1985). The author is not very clear about how conservation of potential vorticity is related to conservation of potential temperature. Null Viscosity Assumption. The conservation of potential vorticity also holds true only for inviscid fluid. Air has negligible viscosity but the author does not have sufficient evidence to assert this assumption true for ‘air mass’ too. Invertibility Property. In addition to the property of conservation, potential temperature is said to be invertible. The author is not clearly convinced what it means and its significance. Diabatic Heat due to Cloud Formation. The air mass in frontal zone has water vapor. At higher altitudes and at colder temperature the gaseous vapor condenses to form clouds where latent heat energy is released. 7
  • 9. The Nitric Oxide Excess. In another scenario if stratospheric intrusion occurs when nitric oxide is abundant in atmosphere, the ozone enhancement cannot be observed because the reaction between nitric oxide and ozone is almost spontaneous. Thus it masks the ozone enhancement due to stratospheric intrusion and it cannot be fully captured. The Potential Vorticity Approximation. The absolute potential vorticity is expressed as shown in the equation above. An approximate method to calculate it is available in many literatures which is also used instead of the exact method to reduce complexity. The approximate method and its limitations are not discussed here. 8
  • 10. REFERENCES Following sources were used as a references. [1] Ozone in our Atmosphere:http://www.esrl.noaa.gov/csd/assessments/ozone/2002/qandas1.pdf, Earth Systems Research Laboratory, National Oceanic and Atmospheric Administration. [2] Lin, M., A. M. Fiore, O. R. Cooper, L. W. Horowitz, A. O. Langford, H. Levy II, B. J. Johnson, V. Naik, S. J. Oltmans, and C. J. Senff (2012), Springtime high surface ozone events over the western United States: Quantifying the role of stratospheric intrusions, J. Geophys. Res., 117, D00V22, doi:10.1029/2012JD018151. [3] Seinfeld, J. H., & Pandis, S. N. (2012). Atmospheric chemistry and physics: from air pollution to climate change. John Wiley & Sons. (Chapter-6) [4] World Health Organization. (2006). WHO Air quality guidelines for particulate matter, ozone, nitrogen dioxide and sulfur dioxide: global update 2005: summary of risk assessment. [5] National Ambient Air Quality Standards, Environmental Protection Agency: https://www.epa.gov/criteria-air-pollutants/naaqs-table. [6] National Research Council (US). Committee on the Significance of International Transport of Air Pollutants. (2010). Global Sources of Local Pollution: An Assessment of Long-Range Transport of Key Air Pollutants to and from the United States. National Academies Press. (Appendix B.) [7] Global Ozone Research, & Monitoring Project. (1985). Atmospheric ozone, 1985: assessment of our understanding of the processes controlling its present distribution and change (Vol. 1, Chapter-5). National Aeronautics and Space Administration. [8] Lefohn, A. S., Wernli, H., Shadwick, D., Limbach, S., Oltmans, S. J., & Shapiro, M. (2011). The importance of stratospheric–tropospheric transport in affecting surface ozone concentrations in the western and northern tier of the United States. Atmospheric Environment, 45(28), 4845- 4857. [9] Department of Environmental Quality/Air Quality Division, State of Wyoming (2014). Exceptional Events Demonstration Package for the Environmental Protection Agency: https://www.epa.gov/sites/production/ files/2015- 05/documents/june_14_2012_bigpiney_boulder_si_package.pdf [10] National Research Council (US). Committee on the Significance of International Transport of Air Pollutants. (2010). Global Sources of Local Pollution: An Assessment of Long-Range Transport of Key Air Pollutants to and from the United States. National Academies Press. (Appendix B.) [11] Reed, R. J. (1955). A Study of a Characteristic Type of Upper-Level Frontogenesis. Journal of Meteorology, 12(3), 226-237. 9
  • 11. [12] Anenberg, S. C., Horowitz, L. W., Tong, D. Q., & West, J. J. (2010). An estimate of the global burden of anthropogenic ozone and fine particulate matter on premature human mortality using atmospheric modeling. Environmental health perspectives, 118(9), 1189. [13] NOAA/ESRL Radiosonde Database, http://esrl.noaa.gov/raobs/ [14] University of Wyoming, Wyoming Weather Lab, http://weather.uwyo.edu/upperair/sounding.html [15] Shapiro, M. A., & Keyser, D. A. (1990). Fronts, jet streams, and the tropopause. US Department of Commerce, National Oceanic and Atmospheric Administration, Environmental Research Laboratories, Wave Propagation Laboratory. ACKNOWLEDGEMENT The author acknowledges this work to the course ENV6932: Global Air Pollutants: its content, design and delivery. 10
  • 12. Annexure-I: TOPOLOGY FACTOR Topology plays a major role in atmospheric circulation and weather systems. That said a too broad concept, however, the author has tried to explain it in brief. Mountainous region that stretch several kilometers can affect the weather systems due to temperature inversion in valleys and surface-level wind disturbances that subsequently affect the transport of particulate matter. This affects the radiation distribution. However this is not a prime reason. It is because the major drivers of stratospheric intrusion such as jet streams are synoptic weather systems while the above factor is probably a mesoscale mechanism. A brief literature overview of stratospheric intrusion in Europe says that many such events are observed in Alps mountain region which extends over several hundred kilometers. However at this moment the author is not fully convinced with the reason, hence the topological effects are not mathematically accounted in this document. The elevation profile of study area (United States) is graphically represented here. ESRI ArcGIS version 10.3.1 was used to plot the raster dataset. The latitude and longitude were not shown in the plot. 11
  • 13. GLOSSARY Except few terms, all are authors own interpretation. The author has tried best to conserve the true meaning and its significance. Absolute Vorticity. It is a measure of the degree of spin an air mass is subjected. Mathematically, it is the sum of curl of velocity and twice the angular momentum of earth. This quantity is a vector. Air Mass. The author uses this term to represent the combined mass of air including gaseous pollutants and aerosols. Atmospheric Sounding. “An atmospheric sounding is a measurement of vertical distribution of physical properties of the atmospheric column such as pressure, temperature, wind speed and wind direction (thus deriving wind shear), liquid water content, ozone concentration, pollution, and other properties. Such measurements are performed in a variety of ways including remote sensing and in situ observations.” – Wikipedia. Concentration. It is used to express the fraction of gaseous pollutant in atmosphere in terms of mass of pollutant per unit volume of air mixture. Unlike mixing ratios, concentration value (g/m3 ) remain constant against temperature variation. (Please check definition for mixing ratios too.) Cut-off Low. It is a cyclone formed when fast currents of jet stream detach from their meandering path between two troughs. Extratropical and Tropical Cyclone. “Extra-tropical cyclone is a storm system that primarily gets its energy from the horizontal temperature contrasts that exist in the atmosphere. Tropical cyclones, in contrast, typically have little or no temperature differences across the storm at the surface, and their winds are derived from the release of energy due to cloud/rain formation from the warm moist air of the tropics. Extra-tropical cyclones have their strongest winds near the tropopause, while tropical cyclones have their strongest winds near the earth's surface. Often, a tropical cyclone will transform into an extra-tropical cyclone as it recurves poleward and to the east. Occasionally, an extra-tropical cyclone will lose its frontal features, develop convection near the center of the storm and transform into a full-fledged tropical cyclone.” – Hurricane Research Division, NOAA. These are also known as baroclinic or mid-latitude cyclones. Frontogenesis / Frontal Zone / Baroclinic zone. The zone of separation between warm and cold fronts. It is a transition zone of finite width and thickness. From authors understanding, these three terms have same meaning. Geostrophic and Ageostrophic winds. Geostrophic winds have Coriolis force balanced by equal and opposite pressure gradient force. In contrast, ageostrophic winds have any one of these quantities dominant. These two terminologies applies to all fluids. This nomenclature and principle is applicable to all fluids. 12
  • 14. Hypergradient Zone. The zone where potential temperature and wind velocity drastically changes across a finite width. In meteorology such zone occurs between wedges of warm and cold front. Isentropic Potential Vorticity (IPV). Generally speaking, in this context (tropopause), there is no difference between potential vorticity and IPV. The term ‘isentropic’ is added before because to highlight the property that air masses conserve potential temperature in adiabatic process. (This similar to usage of terms such as conservative kinetic or conservative potential energy.) Isentropic Surface. It is an imaginary contour surface of constant potential temperature. Jet Streams. They are fast moving air currents flowing around earth at high altitudes (8-15 km) and in eastward direction. There are three primary jet streams in each hemisphere: arctic, polar and subtropical. Arctic jet-streams are observed at 70° N/S latitudes. Polar jet-streams are observed at 45° N/S latitudes. Sub-tropical jet streams are observed at 25° N/S latitudes. The height of occurrence increases in this order: arctic, polar and subtropical. (Source: A compilation from National Geographic and NOAA.) Mixing Ratio. It is used to represent the amount of gaseous pollutant in atmosphere in terms of volume fraction. It translates to amount of the pollutant expressed in volume parts per million parts of total air mixture. It is similar but not same as concentration since mixing ratio depends on volume, and volume varies with temperature unless pollutant and air mixture has same expansion ratio. For an ideal gas, ppm also means molar fraction factored by one-millionth. It is also expressed as parts per billion. Potential Temperature. The equivalent temperature of an air mass when it is brought down to 1000 mb pressure (ground level) adiabatically. Potential Vorticity. It is the absolute vorticity subject to three-dimensional gradient of potential temperature. It is a dot product of three dimensional gradient of potential temperature scaled by specific volume and absolute vorticity. Essentially it is a scalar and usually expressed in potential vorticity unit (1 PVU = 10-6 K m2 kg-1 s-1 ). Radiosonde. It is an instrument (telemetry) suspended by balloon in atmosphere which can measure these variables: altitude, pressure, temperature and relative humidity. (Please check definition for rawinsonde also.) Rawinsonde. It is a special type of radiosonde where its location can be tracked. Thus it can measure wind speed and direction (zonal and meridional) in addition to radiosonde quantities. It is a portmanteau of three names: radar + wind + radiosonde. 13
  • 15. Upper-level. This is not a standalone term. It is widely used before the names such as frontogenesis and troposphere. This term denotes a region or processes happening in troposphere in higher altitude that is in the vicinity of tropopause. The corollary to this term is surface-level. 14
  • 16. ENV 6932: Manuscript Evaluation Form* Author: Kalaivanan Murthy Reviewer: Erick Martinez Score: 80 of 100 *Form modified from http://escholarship.org/uc/item/1200h325 1) Title. ( 0 of 1 pts.) Effective & sensible? No title yet 2) Abstract. ( 5 of 7 pts.) (a.) Well written?
(b.) All components present? (introductory sentence, hypothesis/research question, methods, results, conclusions, implications) results, conclusion, implications not clearly defined Notes: 3) Introduction. (7 of 8 pts.) (a.) Hypothesis/research question clear and presented well? (b.) Is background information sufficient to support pretense for study? Yes, very detailed (c.) Is information cited correctly? Some concepts may need a citation Notes: 4) Methods. (4 of 5 pts.) Is sufficient information presented to clearly understand how the study was conducted? What was done for the study and what was taken from other work? Formatted correctly? Notes: Methods still seem to represent some concepts that should be included in the introduction. 5) Results. (6 of 10 pts.) a) Is description of results presently clearly?
not yet b) Are figures correct?
no figures c) Are tables correct?
no tables d) Is sufficient and the appropriate data presented to address the hypothesis/research question? Foundation for results laid out however require more depth e) Formatted correctly? Notes: 6) Discussion. (7 of 12 pts.) a) Does the discussion follow a logical order?
not exactly, logical, but separate concepts
  • 17. b) Do discussion topics relate to the hypothesis?
yes, several c) Are the conclusions logical and supported by the data? Not yet d) Are implications of the study presented?
not yet e) Is the study summarized in the concluding paragraph? Not yet f) Is there a “take-home” message? yes Notes: 7) References. (2 of 5 pts.) a) Are there at least 20 citations of which at least 10 are peer-reviewed? Not yet b) Are they used correctly?
yes c) Are they formatted correctly?
yes d) Are they cited within the text of the paper? Not all Notes: 8) Overall. (1 of 2 pts.) (a.) Are grammatical errors minimized? (spelling, sentence structure etc) (b.) Is it well written and easy to follow?
(c.) Is it formatted like a scientific manuscript? Notes: some grammatical improvements.