Transcript 091028SaltLakeCity_PMMSciTeamMtgV06_Houze.ppt

Extreme Convection Near the
Himalayas 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
Convective systems
Convective component
Stratiform component
Extreme characteristic
Extreme characteristic
Contiguous convective echo
3D volume 40 dBZ
Contiguous stratiform echo
Horizontal area  50 000 km2
“Broad stratiform region”
Top height  10 km
“Deep convective core”
Horizontal area  1 000 km2
“Wide convective core”
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
Himalayan Region
•Terrain gradients
• Land-ocean contrast
• Land cover differences
Snow/Ice
Thar Desert
Ganges Delta
Tundra
Wetland
Forest
Irrigated crop
Crop
Savanna
Shrub/Grass
Dryland/crop
Grass
Shrub
Barren
Monsoon
Season
Wind &
Moisture
Climatology
SFC
500 hPa
200 hPa
Monsoon
Season
Climatology
of Extreme
Convective
Features
Deep
Convective
Cores
Monsoon
Season
Climatology
of Extreme
Convective
Features
Deep
Convective
Cores
Wide
JulyConvective
Cores
TRMM
Rainfall
Broad
Stratiform
Regions
Monsoon
Season
Climatology
of Extreme
Convective
Features
Deep
Convective
Cores
Wide
Convective
Cores
Broad
Stratiform
Regions
Example of a wide convective core
system in the western region
Backward trajectories (HYSPLIT/NCEP)
2.5 km
1.0 km
TRMM PR Observations
WRF Simulation
WRF Simulation
Mixing ratio
CAPE
WRF Simulation
Isochrones of
integrated
hydrometeor
content
Hydrometeor
mixing ratio just
after convection
formed
Diurnal Variability in the Himalayan
Region
Deep
convective
cores
(mostly land)
Wide
convective
cores:
Land
Wide convective cores
Nocturnal
formation in
Himalayan
foothills
Composite winds
Wide convective core cases
1730
0530
0530
1730
Nocturnal
downslope
flow in
Himalayan
foothills
Andes Region
Regions of analysis
QuickTime™ and a
decompressor
are needed to see this picture.
Foothills
South
La Plata
Basin
Summer Season (DJF)
Deep
convective
Cores
Wide
convective
cores
Broad
stratiform
regions
Precip.
climatology
Example of a Wide Convective Core
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
Wide Convective Case
12 November 2003
Time of TRMM Swat
4:13 UTC (00:13 LT)
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)
Wide Convective Case of 12 November 2003
500 mb height anomaly
Surface pressure anomaly
Composite
for Wide Convective Wide Core Cases in South Region
500 mb
height
anomaly
Surface
pressure
anomaly
[mb]
Surface wind (~02 LT)
QuickTime™ and a
decompressor
are needed to see this picture.
Composite
for Wide Convective Core Cases in South Region
Surface wind
& divergence
Divergence
Divergence
06 UTC
~02 LT
18 UTC
~14 LT
10 m s-1
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
End
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