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 PMM Science Team Meeting, Salt Lake City, October 28, 2009

2. 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”

3. Data & Models TRMM PR 3D reflectivity Sample, 1998-2008 South Asia: June-September, 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 200 hPa 500 hPa Monsoon SeasonWind & Moisture Climatology

7. Monsoon Season Climatologyof ExtremeConvectiveFeatures Deep Convective Cores

8. Wide Convective Cores July BroadStratiformRegions Monsoon Season Climatologyof ExtremeConvectiveFeatures Deep Convective Cores TRMMRainfall

9. Monsoon Season Climatologyof ExtremeConvectiveFeatures Deep Convective Cores Wide Convective Cores BroadStratiformRegions

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

11. Backward trajectories (HYSPLIT/NCEP) 2.5 km 1.0 km

12. TRMM PR Observations WRF Simulation

13. WRF Simulation Mixing ratio CAPE

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

15. Diurnal Variability in the Himalayan Region

16. Deep convective cores(mostly land) Wide convective cores:Land

17. Wide convective cores Nocturnal formation in Himalayan foothills

18. Composite windsWide convective core cases Nocturnal downslope flow in Himalayan foothills 1730 0530 0530 1730

19. Andes Region

20. Regions of analysis Foothills South La Plata Basin

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

22. Example of a Wide Convective Core

23. 12 November 2003 • Multiple tornado reports • Tennis ball sized hail reports • Gusts of 135+ mph winds reported • In Buenos Aires, ~70 mm rain recorded in 9 hours • Approximately 30% of affected cities lost power • 14 fatalities

24. Wide Convective Case 12 November 2003 Time of TRMM Swat 4:13 UTC (00:13 LT)

25. 0 UTC (20 LT on the previous day) Wide Convective Case 12 November 2003 925 mb NCEP/NCAR Reanalysis Temperature & Winds 2 h after TRMM overpass 6 UTC (2 LT)

26. Wide Convective Case of 12 November 2003 500 mb height anomaly Surface pressure anomaly

27. Composite for Wide Convective Wide Core Cases in South Region 500 mb height anomaly Surface pressure anomaly [mb] Surface wind (~02 LT)

28. Divergence Divergence 06 UTC ~02 LT 18 UTC ~14 LT 10 m s-1 Composite for Wide Convective Core Cases in South Region Surface wind & divergence Divergence 06 UTC ~02 LT 18 UTC ~14 LT 10 m s-1

29. Conclusions Deep convective cores • over land only • associated with daytime heating • often in arid regions Wide convective cores • over both land and ocean • affected by nocturnal downslope flow • line structures common in S. America, not in S. Asia • low-level moist jet overrun by dry flow from high terrain • triggered over foothills Broad stratiform regions • most common over ocean and wetlands • absent in arid regions • correspond to climatological rain areas

30. End

31. Sponsored by: NASA Award# NNX07AD59G