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Problems modeling CAPs

Problems modeling CAPs. Clouds Type (ice or liquid) Extent Duration. Stability profile Too weak/diffuse of capping inversion Too deep of mixed layers. Winds Too strong in surface layer Over-dispersive, end CAP too soon. Land surface Snow cover and albedo mis -specified.

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Problems modeling CAPs

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  1. Problems modeling CAPs • Clouds • Type (ice • or liquid) • Extent • Duration • Stability profile • Too weak/diffuse of capping inversion • Too deep of mixed layers • Winds • Too strong in surface layer • Over-dispersive, end CAP too soon • Land surface • Snow cover and albedomis-specified Proposed possible modeling ‘fixes’ Further testing to determine best model parameterizations for CAP cases Further edits to Microphysics code (more rapid ice nucleation) Possible edits to boundary-layer scheme or turn boundary-layer scheme off Changing model vertical and horizontal resolution Snow physics model

  2. Modeling Plans Meteorology. The Weather Research and Forecasting (WRF) model is the industry standard for Simulating the atmosphere, but it has only rarely been used tosimulate winter Inversion conditions. We will improve the model by: • Improving simulation of snowfall, snow depth, melt rates, and snow albedo; and • Determining optimal model configuration for simulation of vertical atmospheric structure, low cloud formation, and surface flow by performing detailed comparisons of iterative model runs against available measurements.

  3. Proposed WRF model refinement/testing procedure: • Test existing WRF PBL/Microphysics schemes for both clear and cloudy CAP • Test impact of vertical and horizontal model resolution on CAP simulations • Further testing on appropriate snow cover /albedo treatment in WRF

  4. Stability Profiles • Test various vertical and horizontal resolutions for *several* cases (both cloudy and clear) CAPs to determine impact • Test multiple PBL/Microphysics schemes • Simulated stability profile inherently linked to land surface, PBL, and cloud parameterization schemes

  5. Does Resolution Matter in Uintah Basin? • In Salt Lake Valley, better results modeling CAPs using large-eddy simulation (ΔX ~ 200 m) than mesoscale model (ΔX ~ 1333 m). • LES computationally expensive • Plan: Compare evolution of LES simulation of 1-6 Feb 2013 with Neemann et al. 2014 simulation.

  6. COARSE ΔX 1335 m LES ΔX 250 m OBSERVATIONS

  7. Parameterization Scheme Sensitivity Studies for Clouds • Plan: Test sensitivity of cloud production/evolution in a CLEAR CAP and ICE CLOUD CAP to • PBL/Microphysics schemes (two are nonlinearly coupled). • Initial conditions • Examples: New Thompson microphysics with prescribed aerosols, test new MYNN PBL fog scheme

  8. Development of low clouds and fog… Nov 28 2103 Nov25 2013

  9. AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND JUNCTION CO 944 PM MST SAT NOV 30 2013 .UPDATE... ISSUED AT 940 PM MST SAT NOV 30 2013 HAVE ADJUSTED AREAS OF FOG FOR TONIGHT THROUGH SUNDAY WITH FOG MAINLY IN THE VALLEY BOTTOMS AND ALONG THE SLOPES OF THE WESTERN MOUNTAINS. SOUNDINGS OVER THE LAST 36HRS AT GJT SHOW THE STRATUS LAYER NEAR 7500FT SO HAVE ADDED FOG TO THE SLOPES DEFINED BY 7-8KFT. THE NEW NAM IS NOT RECOGNIZING THE BOUNDARY LAYERFOGSO ITS FORECAST TEMPS ARE TOO HIGH FOR THE WESTERN VALLEY SITES. AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE ALBUQUERQUE NM 325 PM MST SUN DEC 1 2013... MAIN FORECAST CHALLENGE IN THE SHORT-TERM CONTINUES TO BE NAILING DOWN WHEN THE PERSISTENT LOW CLOUD DECK OVER NW AND WEST CENTRAL NM WILL SCOUR OUT OF THE AREA. THE VAST MAJORITY OF MODEL GUIDANCE DID NOT SHOW THESE CLOUDS CONTINUING TO PLAGUE THE AREA TODAY BUT ALAS THEY ARE STILL HOLDING STRONG. THE RUC13 WAS THE BEST TO HOLD ONTO SATURATION IN THE NEAR SURFACE LAYER AND INDICATIONS ARE THAT IT WILL CONTINUE TONIGHT AND EARLY MONDAY. WINDS ALOFT AND EVEN AT THE SURFACE ARE INCREASING HOWEVER IT IS POSSIBLE THE THICK/PERSISTENT LOW CLOUD DECK IS FEEDING BACK TO STRENGTHEN LOW LEVEL INVERSIONS AND KEEP A VERY SHALLOW BOUNDARY LAYER DECOUPLED.

  10. NAM 12Z 1 Dec F000 GJT GFS 12Z 1 Dec F000 GJT

  11. University of Utah Task: Try to Get the Clouds Right! • Neemann et al. 2014 looked at impact of cloud microphyics on 1-6 Feb 2013 CAP • Ice clouds keep CAP colder with less mixing than liquid clouds

  12. Microphysics Sensitivity 0600 UTC 5 Feb 2013 BASE 0.2 0.2 0.30 Longwave from Clouds (W m-2) Integrated Clouds (mm) Cloud Water (g kg-1) 120 100 0.1 0.1 0.20 80 60 0.1 40 0 0 0.30 120 20 Longwave from Clouds (W m-2) Cloud Ice (g kg-1) Integrated Clouds (mm) 0 100 0 0.20 80 60 0.1 40 20 0 0 FULL

  13. Microphysics Sensitivity 20 Mean BASE - FULL Difference 15 °C W m-2 2-m Temperature Longwave Radiation from Clouds 10 5 0 2 • Mean temperature in basin ~1.5 °C higher in BASE simulation • Related to additional longwave radiation from clouds of 7-20 W m-2 • Greater coverage of stratus in BASE vs. ice fog in FULL leads to large differences where stratus is present but ice fog isn’t 1.5 1 0.5 0 -0.5 -5

  14. University of Utah Task: Snow physics evaluation • For this study, implementation of Neemann et al. 2014 procedure. • Idealized elevation-dependent relationship based on in-situ observations • USU has applied to Jan 2013 case with improved results. • Plan to apply to 1-2 more cases (March 2013 high insolation case and entire Jan 2013 CAP) • Initial work toward incorporating more sophisticated snow physics model

  15. WRF Modifications • Idealized snow cover in Uintah Basin and mountains • Snow albedo changes • Edited VEGPARM.TBL Snow Depth Snow Water Equivalent • Allows model to achieve high albedos measured in basin Photos: Erik Crosman

  16. Albedo Changes Original Modified 0.81 - 0.82 0.62 - 0.65 • 0.82 is average albedo measured at Horsepool during 2013 Uintah Basin Winter Ozone Study

  17. NAM and Prescribed Snow Cover m 1 • Snow cover difference in primary model simulations • Depth/SWE prescribed by elevation • Based on observations available in Uintah Basin and surrounding mountains 0.9 0.8 0.7 0.6 NAM 0.5 0.4 0.3 0.2 0.1 NONE FULL/BASE 0

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