Robert Houze

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Deep Convection in the Asian Monsoon
Robert Houze University of Washington (with
contributions from B. Smull D. Wilton)
Summer
Winter
Presented at Texas A M, 31 March 2005
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July-August 1000 mb wind
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December 1000 mb wind
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July-August 200 mb wind
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December 200 mb wind
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December Precipitation
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Rest of Talk

• Monsoon convection over oceans
• Winter MONEX (1978)
• Summer MONEX (1979)
• JASMINE (1999)
• Monsoon convection over land, near mountains
• TRMM (2002-2003)

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Winter MONEX
December1978January1979
Johnson Houze 1987
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WINTER MONEXDiurnal variation of high cloudiness
near Borneo
Bintulu
S. CHINA SEA
BORNEO
December 1978
08 LST
20 LST
14 LST
02 LST
Houze et al. 1981
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Radar Obs. of WINTER MONEX Borneo cloud system
BORNEO
S. CHINA SEA
Bintulu
Houze et al. 1981
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Diurnal gravity wave generation of mesoscale
convection over coastal South America
Mapes et al. 2003
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Summer Monsoon
Summer MONEX (1979)
JASMINE (1999)
1999
Johnson Houze 1987
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Location of Ship during JASMINE on-station time
NOAA ShipRonald H. Brown
Bay of Bengal
Equator
60E
100E
Webster et al. 2002
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Percent High Cloudiness in the Summer
Monsoon May-September 1999
lt 235 K
lt 210 K
300 mb wind sfc pressure
850 mb wind
Zuidema 2002
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Diurnal cycle, mean percent high cloudiness, 1999
Cloud Top lt 210 K
Zuidema 2002
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Location of cloud systems by horizontal dimension
May-September 1999
CloudTop lt 210 K
Zuidema 2002
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South Asian Topography
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JASMINE Mesoscale Convective Systems Defined
tracked by 218 K infrared threshold
Zuidema 2002
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JASMINE 1999, Ship Track Satellite Data 85-90 E
Ship Track
Webster et al. 2002
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IR Temperature
0830 LST
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IR Temperature
1130 LST
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IR Temperature
1430 LST
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IR Temperature
1730 LST
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IR Temperature
2030 LST
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IR Temperature
2030 LST
Ship radar
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JASMINE 1999 Ship Radar Data
2345 LST 22 May 99
0215 LST 23 May 99
0615 LST 23 May 99
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JASMINE 1999 Ship Radar Data
Reflectivity
Reflectivity
Doppler Radial Velocity
22 May 1999 2300 LST
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JASMINE 1999 Ship Radar Data
Reflectivity
Reflectivity
Doppler Radial Velocity
22 May 1999 2143 LST
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23 May 1999 0650 LST
JASMINE Ship RadarData
TRMM PrecipitationRadar Swath
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TRMM Precipitation Radar shows extensive
stratiform structure
23 May 1999 0650 LST
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SUMMER MONEX 6 July 1979
850 mb wind
Houze Churchill 1987
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Houze Churchill 1987
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SUMMER MONEX Microphysics, All P3 flights, 3-8
July 1979
-25
Columns
Plates Dendrites
Aggregates Drops
Columns
-20
Dendrites
-15
Flight Level Temperature (deg C)
-10


Plates
Aggregates
Needles
-5
0
Melting
Drops
Relative Frequency of Occurrence
Houze Churchill 1987
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Summary of Oceanic Monsoon Convection
1978
1999

• Oceanic deep convection in both winter summer
  monsoons occurs in deep, broad mesoscale
  convective systems (MCSs)
• MCSs often form over ocean and propagate seaward,
  apparently gravity waves forced by diurnal
  heating over high terrain
• MCSs have a discrete component of
  propagationconsistent with wavelike behavior
• Radars (on land, ship, aircraft satellite) show
  broad areas of stratiform precipitation in mature
  maritime MCSs
• Microphysical imagery from aircraft show
  extensive ice particle growth by deposition
  aggregation, consistent with stratiform
  precipitation

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TRMM Observations of Convection over Land in the
Himalayan Region2002-2003
TRMM
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TRMM Precipitation Radar Data Set Used in This
Study

• June-September 2002, 2003
• 1648 Overpasses over Himalayan region
• Data specially processed at University of
  Washington
• Cartesianized to facilitate analysis in Mountain
  Zebra
• This dataset optimized to analyze vertical
  structure of echoes

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TRMM Satellite Instrumentation
l 2 cm
Important! PR measures 3D structure of radar
echoes
Kummerow et al, 1998
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Idealized Horizontal Pattern of the Radar Echo
Pattern in a Mesoscale Convective System
Radar reflectivity
Echo type
Plan View
Houze 1997
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Conceptual Model of Vertical Structure
Convective Rain Elements
Houze 1997
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Conceptual Model of Vertical Structure
Stratiform Rain Elements
Houze 1997
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To study the vertical structure of convective
regions we define 3D echo cores

• The TRMM Precipitation Radar data are provided in
  bins 5 km in the horizontal and 0.25 km in
  the vertical
• Echo cores are formed by contiguous bins (in 3D
  space) of reflectivity values which exceed the
  threshold of 40 dBZ.

3D radar echo bounded by 40 dBZ contour
echocore
land
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Deep Convection Core 14 June 2002, 0859 UTC
deep convection cores are those for which the
maximum heights of the 40 dBZ core are greater
than 10 km
4 km level
30N
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Height (km)
8
28N
0
55
110
Distance (km)
74E
76E
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Analysis Subregions
N
Arabian Sea
Bay of Bengal
INDIA
E
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Normalized Frequency Distribution of 40 dBZ
Convective Echo Core Heights
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Lightning Frequency Based on TRMM Satellite
Observations
Barros et al. 2004
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Wide Convection Core 22 July 2002, 1309 UTC
wide convection cores are those for which the
area of the 40 dBZ core are greater than 1,000
km2, corresponding to a dimension of
approximately 30km
4 km level
34N
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30N
Height (km)
8
72E
76E
0
120
240
Distance (km)
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Cumulative Distribution of Convective Core Breadth
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Analysis of stratiform echo regions

• Used TRMM algorithm for separating echoes into
  stratiform convective regions
• Two criteria

Existence of bright band
Lack of intense echo cores
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Broad Stratiform Case 5 June 2003, 1347 UTC
broad stratiform cases are those for which the
area classified by the TRMM algorithm as
stratiform precipitation is greater than about
50,000 km2, corresponding to a dimension of
approximately 225 km
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Cumulative Distribution Functionfor Stratiform
Precipitation Areas
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TRMM Satellite Instrumentation
l 2 cm
Important! PR measures 3D structure of radar
echoes
Kummerow et al, 1998
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Contoured Frequency by Altitude Diagram
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Reflectivity Statistics by Sub-Region, Rain-Type,
Altitude
Convective

• Convection is stronger deeper in west
• Stratiform more pronounced in east

Stratiform
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Locations of Intense Convective Cases and Wide
Stratiform Cases
Concavities lead to concentration of intense
convection in NW and stratiform systems in NE
N
E
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Terrain Elevation Categories
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Reflectivity Statistics by Subtending Terrain
Lowland
Foothills
Convection is slightly deeper stronger over the
lowlands than the foothills
Mountain
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Wide Area of Convection Case 1309 UTC 22 July
200200 UTC Soundings
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Wide Area of Convection Case 1309 UTC 22 July
200212 UTC Soundings
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Broad Stratiform Case 1347 UTC 5 June 2003 12
UTC Soundings
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Summary of Himalayan Region Convection
As seen by TRMM2002-2003

• 40 dBZ cores
• most intense occur at border of moist flow
  downslope dry flow
• deepest broadest in NW continental regime
• can reach 17 km Þ graupel lofted to high levels,
  electrification
• concentrated near mountains, esp. NW concavity of
  the Himalayas
• strongest over lowlands foothills
• Large stratiform echoes
• larger more frequent in NE maritime regime
• concentrated near mountains, esp in the NE
  concavity

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Conclusions
TRMM

• Over oceans
• Deep, broad mesoscale convective systems
• Often diurnally forced by heating over land
• Gravity waves implicated
• Deposition aggregation dominant microphysics in
  stratiform regions
• Over land
• More cellularless likely to form MCSs with large
  stratiform regions
• Convection intensegraupel lofted to high levels,
  electrification
• Stratiform regionscan be larger where maritime
  flow intrudes over land
• Near over mountains
• Convection most frequent close to mountains
• Convection strongest just upstream of mountains,
  over foothills
• Intense convection occurs at border of moist flow
  downslope dry flow

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THE END Thanks for your attention
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WINTER MONEXDiurnal variation of high cloudiness
near Borneo
Bintulu
S. CHINA SEA
BORNEO
December 1978
08 LST
20 LST
14 LST
02 LST
Houze et al. 1981
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Diurnal cycle, mean percent high cloudiness, 1999
lt235 K
lt210 K
Zuidema 2002
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Stratiform precipitation shown by the Bintulu
Radar
Churchill Houze 1984
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WINTER MONEX Time series of high cloudiness seen
by satellite
SOUTH CHINA SEA
BORNEO
December 1978
Houze et al. 1981
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SUMMER MONEX 8 July 1979
850 mb wind
Houze Churchill 1987
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Microphysics
SUMMER MONEX 8 July 1979 NOAA P3 Aircraft
20N
Radar
20N
16N
16N
82E
86E
82E
86E
Houze Churchill 1987
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Thunderstorm over India
low echo centroid (coalescence riming)
Maheshwari Mathur 1968
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Colorado Rockies Big Thompson Storm 1976
low echo centroid
Caracena et al. 1979
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Contoured Frequency by Altitude Diagrams
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Contoured Frequency by Altitude Diagrams
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Contoured Frequency by Altitude Diagrams
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Contoured Frequency by Altitude Diagrams
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Contoured Frequency by Altitude Diagram
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Reflectivity by Sub-Region
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Reflectivity Related to Rain Rate
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20-year Alpine Autumn Precipitation Climatology
(rain gauge analysis by Frei and Schaer 1998)