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Christman Field Latest Observations
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Date Time
MST
Temp
°F
RH
%
DewPt
°F
Wind
mph
Dir
°
Gust
mph
Dir
°
Press
in Hg
Solar
W/m^2
Prec
in
2023-01-31 23:45 8.0 81.2 3.5 0.9 71 3.0 72 24.894 0.0 0.00
2023-01-31 23:40 9.4 78.7 4.1 2.7 204 3.9 230 24.892 0.0 0.00
2023-01-31 23:35 8.6 82.8 4.4 3.0 243 4.2 247 24.894 0.0 0.00
2023-01-31 23:30 8.9 78.5 3.6 2.6 228 3.3 198 24.894 0.0 0.00
2023-01-31 23:25 9.6 79.0 4.3 3.4 198 4.1 225 24.894 0.0 0.00
2023-01-31 23:20 9.8 76.9 4.1 2.2 216 2.9 209 24.894 0.0 0.00
2023-01-31 23:15 10.0 79.4 4.9 2.6 220 2.9 231 24.894 0.0 0.00
2023-01-31 23:10 9.3 79.6 4.3 3.1 220 4.4 249 24.894 0.0 0.00
2023-01-31 23:05 10.4 78.0 4.9 4.2 267 6.2 283 24.894 0.0 0.00
2023-01-31 23:00 9.2 80.0 4.3 3.3 264 4.7 264 24.893 0.0 0.00
2023-01-31 22:55 7.7 82.1 3.4 3.8 242 6.1 299 24.894 0.0 0.00
2023-01-31 22:50 6.1 81.9 1.8 3.7 315 6.8 313 24.894 0.0 0.00
2023-01-31 22:45 8.5 74.4 2.0 3.1 339 8.3 330 24.896 0.0 0.00
2023-01-31 22:40 9.3 76.1 3.3 4.2 333 7.4 333 24.900 0.0 0.00
2023-01-31 22:35 8.8 78.1 3.4 4.6 1 5.6 345 24.901 0.0 0.00
2023-01-31 22:30 10.8 76.4 4.8 2.3 288 3.2 288 24.900 0.0 0.00
2023-01-31 22:25 11.1 76.2 5.1 0.5 260 1.9 260 24.901 0.0 0.00
2023-01-31 22:20 11.5 75.5 5.2 2.1 217 3.1 261 24.898 0.0 0.00
2023-01-31 22:15 10.1 78.5 4.8 2.4 266 4.2 259 24.899 0.0 0.00
2023-01-31 22:10 10.6 78.0 5.1 2.2 216 4.9 244 24.900 0.0 0.00
2023-01-31 22:05 10.3 78.3 4.9 3.1 247 3.8 248 24.899 0.0 0.00
2023-01-31 22:00 9.5 80.2 4.6 4.5 219 5.5 255 24.897 0.0 0.00
2023-01-31 21:55 11.1 76.3 5.1 4.2 262 8.2 255 24.896 0.0 0.00
2023-01-31 21:50 9.0 86.9 5.9 5.5 251 8.9 253 24.898 0.0 0.00
2023-01-31 21:45 5.8 84.0 2.0 3.7 265 5.0 247 24.899 0.0 0.00
2023-01-31 21:40 6.2 83.5 2.2 3.5 259 4.4 247 24.897 0.0 0.00
2023-01-31 21:35 5.7 85.8 2.4 2.7 317 3.5 316 24.896 0.0 0.00
2023-01-31 21:30 5.3 84.5 1.7 3.1 299 4.3 261 24.899 0.1 0.00
2023-01-31 21:25 5.2 84.3 1.5 2.7 248 4.3 237 24.901 0.0 0.00
2023-01-31 21:20 5.3 82.4 1.1 1.8 249 3.2 249 24.899 0.0 0.00
Date Time
MST
Temp
°C
RH
%
DewPt
°C
Wind
m/s
Dir
°
Gust
m/s
Dir
°
Press
hPa
Solar
W/m^2
Prec
mm
2023-01-31 23:45 -13.3 81.2 -15.8 0.4 71 1.4 72 843.02 0.0 0.00
2023-01-31 23:40 -12.6 78.7 -15.5 1.2 204 1.7 230 842.96 0.0 0.00
2023-01-31 23:35 -13.0 82.8 -15.3 1.4 243 1.9 247 843.00 0.0 0.00
2023-01-31 23:30 -12.8 78.5 -15.8 1.1 228 1.5 198 843.01 0.0 0.00
2023-01-31 23:25 -12.5 79.0 -15.4 1.5 198 1.8 225 843.01 0.0 0.00
2023-01-31 23:20 -12.3 76.9 -15.5 1.0 216 1.3 209 843.00 0.0 0.00
2023-01-31 23:15 -12.2 79.4 -15.1 1.1 220 1.3 231 843.00 0.0 0.00
2023-01-31 23:10 -12.6 79.6 -15.4 1.4 220 2.0 249 843.01 0.0 0.00
2023-01-31 23:05 -12.0 78.0 -15.0 1.9 267 2.8 283 843.01 0.0 0.00
2023-01-31 23:00 -12.6 80.0 -15.4 1.5 264 2.1 264 842.99 0.0 0.00
2023-01-31 22:55 -13.5 82.1 -15.9 1.7 242 2.7 299 843.00 0.0 0.00
2023-01-31 22:50 -14.4 81.9 -16.8 1.6 315 3.1 313 843.01 0.0 0.00
2023-01-31 22:45 -13.1 74.4 -16.7 1.4 339 3.7 330 843.08 0.0 0.00
2023-01-31 22:40 -12.6 76.1 -15.9 1.9 333 3.3 333 843.20 0.0 0.00
2023-01-31 22:35 -12.9 78.1 -15.9 2.1 1 2.5 345 843.24 0.0 0.00
2023-01-31 22:30 -11.8 76.4 -15.1 1.0 288 1.4 288 843.19 0.0 0.00
2023-01-31 22:25 -11.6 76.2 -15.0 0.2 260 0.9 260 843.24 0.0 0.00
2023-01-31 22:20 -11.4 75.5 -14.9 1.0 217 1.4 261 843.16 0.0 0.00
2023-01-31 22:15 -12.2 78.5 -15.1 1.1 266 1.9 259 843.17 0.0 0.00
2023-01-31 22:10 -11.9 78.0 -15.0 1.0 216 2.2 244 843.20 0.0 0.00
2023-01-31 22:05 -12.0 78.3 -15.0 1.4 247 1.7 248 843.19 0.0 0.00
2023-01-31 22:00 -12.5 80.2 -15.2 2.0 219 2.5 255 843.12 0.0 0.00
2023-01-31 21:55 -11.6 76.3 -14.9 1.9 262 3.7 255 843.06 0.0 0.00
2023-01-31 21:50 -12.8 86.9 -14.5 2.5 251 4.0 253 843.13 0.0 0.00
2023-01-31 21:45 -14.6 84.0 -16.7 1.7 265 2.2 247 843.17 0.0 0.00
2023-01-31 21:40 -14.4 83.5 -16.5 1.5 259 2.0 247 843.12 0.0 0.00
2023-01-31 21:35 -14.6 85.8 -16.5 1.2 317 1.5 316 843.06 0.0 0.00
2023-01-31 21:30 -14.8 84.5 -16.8 1.4 299 1.9 261 843.18 0.1 0.00
2023-01-31 21:25 -14.9 84.3 -16.9 1.2 248 1.9 237 843.23 0.0 0.00
2023-01-31 21:20 -14.8 82.4 -17.2 0.8 249 1.4 249 843.16 0.0 0.00
CIRA

Cooperative Institute for Research in the Atmosphere

Pressure Perturbations in Cumulus Convection

January 20, 2017 11:15 am
ATS 101

Presented by: John Peters

Hosted by: Russ Schumacher

CSU Postdoctoral Fellow


Pressure perturbations are regions of anomalously low or high pressure in deep convection and play key roles in modulating the magnitude and distribution of vertical velocities within cumulus clouds. A cloud’s vertical momentum budget is primarily regulated by two pressure forces: Effective buoyancy pressure acceleration (EBPA), and dynamic pressure acceleration (DPA).

 

I will first discuss EBPA, which drives upward (downward) acceleration of air parcels if they are anomalously less (more) dense than their surrounding environments. I show that EBPA is dependent on (1) the temperature perturbation within an updraft, (2) the temperature immediately surrounding an updraft, and (3) the updraft’s width-to-height aspect ratio. A consequence of (3) is that wider and/or shallower clouds have weaker vertical velocities than narrower and/or deeper clouds, all else being equal. I will then discuss DPA. Dynamic pressure perturbations arise from spatial gradients in wind velocity and preserve approximate zero mass-flux convergence in the atmosphere. For a general, un-sheared updraft, DPA is oriented upward below the updraft’s level of maximum temperature perturbation, and downward above the updraft’s level of maximum temperature perturbation. This leads to a cloud’s maximum vertical velocity occurring near the middle troposphere, rather than near the tropopause (as parcel theory would suggest).

 

Are there ways that we can better understand EBPA and DPA and their impact on deep convection? To address this question, I will first discuss potential avenues for improving the representation of EBPA and DPA in cumulus parameterization. I will then address a specific example of how DPA constrains the predictability of supercell behavior in certain atmospheric environments. For supercells in vertical wind shear, DPA causes the supercell’s motion to deviate to the left or right of the mean tropospheric wind (this behavior is called “deviant motion”). I will use a series of sensitivity experiments to show that the character of DPA deviant supercell motion is highly sensitive to lower-tropospheric temperature and model grid spacing.