1. NIDHEESH P. V.
SREEKUMAR E. B.
SARATH E V.
Dept. of Physics, Sreekrishna College, Guruvayur
Project Supervisor
Dr. R. Vishnu

2. Objective
 To study the vertical structure of atmosphere.
 Familiarize with the Radiosonde instrument and data.
 To understand the vertical profiles of temperature, RH
and dew point temperature of atmosphere during two
contrast period (rainy and non-rainy).
 Familiarize with thermodynamic diagram, Skew-T Log-
P.

3. Introduction
 The primary purpose of the upper air sounding is to analyze and describe the
current weather pattern.
 Vertical profiles of atmosphere are the core of global weather observing system
that provides inputs to numerical weather forecast models.
 There are nearly 1000 radiosonde stations world wide that made an average of
1209 soundings each day in support of weather forecasting.
 This atmospheric profile data can be used to determine and predict the
atmospheric conditions and severe atmospheric events like heavy rains,
cyclones, thunderstorms etc
 Upper air sounding data measured from Chennai, downloaded from the web
site of University of Vyoming, is used for the study.

4. Rainfall data over Chennai during post monsoon
period 2015
Source:
India Meteorological Department
In South India, flood resulted from heavy rainfall generated by the annual northeast
monsoon in November–December 2015, the city of Chennai particularly hard-hit.
On November 2015, during the annual cyclone season, a low pressure area consolidated into
a depression and slowly intensified into a deep depression before crossing the coast of Tamil
Nadu. the following day. Because of land interaction, the system weakened into a well-
marked low pressure area over north Tamil Nadu on 10 November. The system brought very
heavy rainfall over the coastal and the north interior districts of Tamil Nadu

5. Radiosonde
 Radiosonde is an instrument used to measure
atmospheric parameters
 It has sensors to measure atmospheric pressure,
temperature, relative humidity
 They provide valuable data for meteorologists to make
forecasts and predict storms, and data for research

6. Radiosonde instrument and its setup

7. Vertical temperature profile of atmosphere

8. Vertical profiles of temperature, dew point temperature and RH on
rainy (16/11/2016) and non rainy (22/12/2016) day

9. Comparison of atmospheric profiles during rainy and non rainy days
Variation in Rainy day
 On this day the Td is close to T in
the whole troposphere represents
a very humid saturated
atmosphere.
 The available water vapor in the
atmosphere gets condensed to
form water droplets and falls
down as precipitation.
Variation in non Rainy days
 Td and RH are less in non rainy
day
 Near to surface T and Td are
close and RH is ~90% and
decreases with height,
 The increase in temperature with
height is referred to as an
inversion. Sometimes, as in this
case, a stable layer exists, this
stable layer is saturated,
indicating a layer of cloud.

10. Skew-T Log-P Diagram
 A Skew-T Log-P diagram is one of four
thermodynamic diagrams commonly used in weather
analysis and forecasting.
 A large number of meteorological variables, indices,
and atmospheric conditions can be found directly or
through simple analytical procedures, which are very
helpful in predicting atmospheric stability.

11. Skew-T log-P diagram on rainy day (16 Nov, 2015)

12. Skew-T log-P diagramon non rainy (22 Dec, 2015)

13. Conclusion
 High moisture content through out the troposphere was
observed during the heavy rainy day
 The temperature profile line and due temperature profile
lines were close together suggesting heavy cloud and
rains.
 stable days the temperature and dew point temperature
profiles were widely separated.
 This atmospheric profile data can be used to determine
and predict the atmospheric conditions heavy rains,
cyclones, thunderstorms etc.

14. Reference
 http://kiwi.atmos.colostate.edu/group/todd/Extras_fil
es/Skew-T-Manual.pdf
 http://curry.eas.gatech.edu/Courses/6140/ency/Chapt
er1/Ency_Atmos/Radiosondes.pdf
 http://weather.uwyo.edu/upperair/sounding.html