1. S
Analysis of Convectively Coupled Equatorial
Kelvin Waves in a GCM with a Modified
Entrainment Profile
Raymond Ruiz
Dept. of Physical and Mathematical Sciences at North Carolina State University, Raleigh, NC
Walter Hannah, & Dr. Eric Maloney
Dept. of Atmospheric Sciences, Colorado State University, Fort Collins, CO
3. Convectively Coupled Kelvin Waves
S Eastward propagating waves
S C= √gH,
S H is equivalent Depth
S Major weather producer in the tropics
S Not well represented in Global Climate Models
4. Entrainment
S Entrainment
S Turbulent flow captures non-
turbulent flow
S Mixing more environmental
air, diluting, less potent
S Allows for representation of
Shallow Convection
http://www.cmmap.org/images/learn/clouds/entrainment.jpg
5. Model and Parameterizations
S Observational- NOAA interpolated
OLR data used from 1980-2011
S NCAR Community Atmosphere Model
5 (CAM5).
S Control- Entrainment known as the
Relaxed Arakawa and Schubert
(RAS)
S Total Precip. Mm/day
S Experiment- Entrainment in
model is being increased(λ)
S Total Precip. Mm/day
6. Methods
S Energy as a function of frequency and wavenumber
S Kelvin wave filtering process
S All season variance plots in order to obtain area of greatest signal
S Wave regression with multiple variables, horizontal structure, latitude
vs. longitude
S Wave lagged regression for cross section overview, time vs. height
7. Wheeler and Kiladis et al.
S Function of frequency vs. Zonal
wave number
S Theoretical curves vs. Power
S Tells us propagation speeds
and wave cycle
14. Summary
S Slower propagation speeds
S Linear, coherent propagation signal
S More pronounced vertical structure
S General improvements, causes for improvements require
further research.
This scientist, Montson, developed simplified shallow water wave equations, and they can then be used to model CCKW in the athmosphere. One of these equations used to show propagation of KW is c=
Where H changes based on convection. The more convection, the less H thus reducing Speed. Dry kelvin waves propagate faster than when coupled with convection.
It is important to then improve the way convection is treated within clouds in order to get a better model representation. A key method within cloud convection parameterization is the process of entrainment.
OLR allows us to see top of clouds. We can See the difference between lower and higher clouds. OLR serves as an approximation of precipitation. Assume there is precipitation under areas of higher clouds.
Next - Ran CAM5, Control entrainment line obtained by previous studies. Then added entrainment as experimental run
Regression Technique allows us to focus and analyze on the area of strongest KW signal (120E) and we can also then see the behavior of dynamical variables around this area of greatest signal.
Lagged regression allows us to analyzed not only the propagation of the wave but also evolution of the wave, again centered in area and time of greatest signal.
Waves around the circumference of the earth. Equivalent Lines of 12.5, 25, and 50. Average propagation of Kelvin waves are around 6-10 days sometimes greater.
Put Experiment in.
Both The experiment and control show a stronger variance east of that of the observation.. Reasons for this are unknown but, 120 E was then used in order to get greatest model results
UPPER LEVEL WINDS EASTERLY WINDS in low and westerly in lower level in low
Upper level westerly in High And lower level easterly in high
YOU THEN HAVE LOWER LEVEL CONVERGENCE. Lower heights then goes towards the convergence.
First of all, OLR is negative, therefore the OLR has inversed colors shaded differently from that of model precipitation
850mb are overlaid over the OLR index signal(showed in first panel) and Total Precipitation signal(showed by the last two panels)
You can see lower level westerly in the surface indicated by low, and then lower level easterlies near area of suppress convection.
Control shows a smaller, tighter area of max convection and an area of large compressed convection.
Experiment shows a generally closer pattern to obs. view. Experiment also does a very good job with reducing random area of suppressed convection.
Propagation of the wave. Time on the y axis(-15 to 15) and latitude in the x. Strongest signal in day 0. Note eastward propagation of signal. 850 mb zonal winds are overlaid indicating convergence near the area of greatest contour grandniece. In the experiment, you can see a more coherent signal closer to that of observation. It expands the signal and lacks the tightness seen in the control indicating larger time range.. This represents one of the improvements seen.
Allows us to see cross sectional view of the evolution of the wave. Height versus time. Different variables. Looking for WESTWARD tilted profile. You need to have indications of shallow convection before reaching maximum deep convection. Moisture is clearer in experiment when compared to that of the control. You are also able to a clearer signal of convergence in the surface and divergence aloft indicated by the color contours.
