Transcript 080812Whistler_MtnMet_Romatschke.ppt

Regional, Seasonal, and Diurnal Variations
of Convection in the Himalayan Region
Ulrike Romatschke
University of Washington, University of Vienna
Socorro Medina, Robert A. Houze Jr.
University of Washington
13th Conference on Mountain Meteorology, 11-15 August 2008, Whistler, BC, Canada
Objectives
Use 3D reflectivity structure of precipitating
systems to document
 Regional variability
Role of topography
 Seasonal variability
Pre-monsoon vs. monsoon
 Diurnal variability
Ulrike Romatschke, University of Washington, University of Vienna
Data
 Tropical Rainfall Measurement Mission (TRMM)
Precipitation Radar (PR)
3D reflectivity
 1999 – 2006
Pre-monsoon: May
Monsoon: June – September
 NCEP reanalysis
Large-scale environment
Ulrike Romatschke, University of Washington, University of Vienna
Classification of radar echoes within
convective systems
 Deep Convective Cores
Convective 40 dBZ echo  10 km (vertical)
 Wide Convective Cores
Convective 40 dBZ area  1 000 km² (horizontal)
 Broad Stratiform Echoes
Stratiform area  50 000 km² (horizontal)
Ulrike Romatschke, University of Washington, University of Vienna
Deep Convective Cores
Deep Convective Cores
 Pre-monsoon (May)
 Monsoon (Jun-Sep)
Ulrike Romatschke, University of Washington, University of Vienna
 Pre-monsoon
 Monsoon
Specific
Humidity
Ulrike Romatschke, University of Washington, University of Vienna
Deep Convective Cores
 Monsoon Diurnal Cycle
00
03
06
09
12
15
18
21
Mean Solar Time
Ulrike Romatschke, University of Washington, University of Vienna
00
Wide Convective Cores
Wide Convective Cores
 Pre-monsoon (May)
 Monsoon (Jun-Sep)
Ulrike Romatschke, University of Washington, University of Vienna
Wide Convective Cores
 Monsoon Rain
Climatology
 Monsoon Wide
Convective Cores
Ulrike Romatschke, University of Washington, University of Vienna
Land Wide Convective Cores
00 – 12
MST
 Monsoon Diurnal Cycle
Evening
00
03
06
09
12
15
18
21
00
Mean Solar Time
Ulrike Romatschke, University of Washington, University of Vienna
12 – 00
MST
Wind composites for Wide Convective Cores
at the Himalayan foothills
1200 UTC (~ 1730 MST)
0000 UTC (~ 0530 MST)
Ulrike Romatschke, University of Washington, University of Vienna
Broad Stratiform Echoes
Broad Stratiform Echoes
 Monsoon Rain
Climatology
 Monsoon Broad
Stratiform Echoes
Ulrike Romatschke, University of Washington, University of Vienna
Conclusions
Monsoon
rainfall patterns strongly
influenced by convective systems of the
following
types Sea and Bay of
 Rain maximum
over Arabian
Bengal
Convective systems with Broad Stratiform Echoes
 Rain maximum over Himalayan foothills
Convective systems with Wide Convective Cores
occurring late night/early morning
 Severe convection maximum in northwestern
indentation region
Convective systems with Deep Convective Cores
Ulrike Romatschke, University of Washington, University of Vienna