Extreme Convection Near the Himalayas and Andes

1. Extreme Convection Near theHimalayas and Andes Robert A. Houze, Jr. Ulrike Romatschke, Socorro Medina, Kristen Rasmussen Dev Niyogi, Anil Kumar Gerald R. North Symposium, Texas A&M University, College Station, June 8, 2009

2. Sponsored in part by: NSF Award# ATM-0505739 NSF Award# ATM-0820586 NASA Award# NNX07AD59G

3. Data & Models TRMM PR 3D reflectivity Sample, 1998-2008 South Asia: March-April, 1999-2006 South America: December-February, 1998-2008 NCEP reanalysis Large-scale environment WRF model Simulation of representative cases

4. Himalayan Region

5. Snow/Ice Tundra Wetland Forest Irrigated crop Thar Desert Crop Ganges Delta Savanna Shrub/Grass Dryland/crop Grass Shrub Barren • Terrain gradients • Land-ocean contrast • Land cover differences

6. SFC SFC 500 hPa 200 hPa 500 hPa 200 hPa Wind & Moisture Climatology

7. Convective systems Convective component Stratiform component Extreme characteristic Contiguous convective echo 3D volume 40 dBZ Extreme characteristic Contiguous stratiform echoHorizontal area  50 000 km2 “Broad stratiform region” Top height  10 km “Deep convective core” Horizontal area  1 000 km2 “Wide convective core”

8. Examples Deep Convective Core Stratiform Wide Convective Core Convective BroadStratiformRegion

9. Pre-Monsoon Monsoon Deep Convective Cores Climatologyof ExtremeConvectiveFeatures Wide Convective Cores BroadStratiformRegions

10. May July Pre-Monsoon Monsoon Deep Convective Cores Climatologyof ExtremeConvectiveFeatures Wide Convective Cores TRMMRainfall BroadStratiformRegions

11. Pre-Monsoon Monsoon Deep Convective Cores Climatologyof ExtremeConvectiveFeatures Wide Convective Cores BroadStratiformRegions

12. Example of a wide convective core system in the western region

13. Backward trajectories (HYSPLIT/NCEP) 2.5 km 1.0 km Sawyer 1947Houze et a. 2007

14. Pakistan India Pakistan India ObservationsInfrared satellite temperature (shaded, K)and low-resolution terrain (black contours, km) WRF-simulationCloud top temperature (shaded, K)and terrain (black contours, m)

15. TRMM PR Observations WRF Simulation

16. WRF Simulation Mixing ratio CAPE

17. WRF Simulation Isochrones of integrated hydrometeor content Hydrometeor mixing ratio just after convection formed

18. Diurnal Variability in the Himalayan Region

19. Deep convective cores(mostly land) Wide convective cores:Land Wide convective cores:Ocean Broad stratiform regions:Ocean

20. Wide convective cores Nocturnal formation in Himalayan foothills

21. Composite windsWide convective core cases 1130 1730 Nocturnal downslope flow in Himalayan foothills 2330 0530

22. Andes Region

23. Regions of analysis Foothills North Foothills South La Plata Basin

24. Summer Season (DJF) Deep convective Cores Wide convective cores Broad stratiform regions Precip. climatology

25. Example of a Wide Convective Core

26. Wide Convective Case (37,901 km2 40 dBZ echo)

28. 0 UTC (20 LT on the previous day) 925 mb NCEP/NCAR Reanalysis Air Temperature and Vector Winds Time of TRMM Swath is 4:13 UTC (00:13 LT) 6 UTC (2 LT)

29. 500 mb Geopotential Height Anomaly for 11/12/2003 925 mb Geopotential Height Anomaly for 11/12/2003

30. Composite of NCEP Data For wide convective cores inSOUTH 500 mb geopotential height anomaly Surface pressure anomaly [mb] Surface winds (~02 LT)

31. Divergence Divergence 06 UTC ~02 LT 18 UTC ~14 LT 10 m s-1 Composites For wide convective cores inSOUTH 500 mb geopotential height anomaly Surface winds & divergence Divergence 06 UTC ~02 LT 18 UTC ~14 LT 10 m s-1

32. Region ofEastern HimalayasandBay of Bengal

33. Pre-Monsoon Monsoon RECALL Deep Convective Cores Climatologyof ExtremeConvectiveFeatures Wide Convective Cores BroadStratiformRegions

34. Example of a Bay of Bengal Case WRF simulation Surface wind Total Rain

35. TRMM PR WRF Simulation (a)

36. WRF Simulation

37. WRF Simulation

38. WRF Simulation Summary Black--850 mb wind vectors

39. WRF Simulation Summary Black--850 mb wind vectorsYellow--850 wind speed

40. WRF Simulation Summary Black--850 mb wind vectorsYellow--850 wind speedWhite--LH flux

41. WRF Simulation Summary Black--850 mb wind vectorsYellow--850 wind speedWhite--LH fluxBlue--Precipitable water

42. WRF Simulation Summary Black--850 mb wind vectorsYellow--850 wind speedWhite--LH fluxBlue--Precipitable waterRed--Precip

43. WRF Simulation Summary Black--850 mb wind vectorsYellow--850 wind speedWhite--LH fluxBlue--Precipitable waterRed--Precip White--850 mb height

44. WRF Simulation Summary Black--850 mb wind vectorsYellow--850 wind speedWhite--LH fluxBlue--Precipitable waterRed--Precip White--850 mb heightYellow--500 mb vertical velocity

45. WRF Simulation Summary Black--850 mb wind vectorsYellow--850 wind speedWhite--LH fluxBlue--Precipitable waterRed--Precip White--850 mb heightOrange--500 mb vertical velocityRed--Precip

46. Conclusions Deep convective cores • associated with daytime heating • rare over ocean • often in arid regions • low-level moist jet overrun by dry flow from high terrain Wide convective cores • both land and ocean • associated with systems that develop broad stratiform regions • affected by nocturnal downslope flow • line structures common in S. America, not in S. Asia Broad stratiform regions • most common over ocean and wetlands • likely later stage of MCS • over land--strongly reinforced by flow interaction with mountains • over ocean--weak diurnal cycle but max in midday over oceans

47. End