Robert Houze
University of Washington
(with contributions from B. Smull & D. Wilton)
Winter
Summer
Presented at: PNNL 18 July 2005
July-August 1000 mb wind
December 1000 mb wind
July-August 200 mb wind
December 200 mb wind
July-August Precipitation
December Precipitation
Rest of Talk
Monsoon convection over oceans
Winter MONEX (1978)
Summer MONEX (1979)
JASMINE (1999)
Monsoon convection over land, near mountains
TRMM (2002-2003)
December
1978
January
1979
Johnson & Houze 1987
WINTER MONEX
Diurnal variation of high cloudiness near Borneo
Bintulu
S. CHINA
SEA
December
1978
BORNEO
08 LST
20 LST
14 LST
02 LST
Houze et al. 1981
Radar Obs. of WINTER MONEX Borneo cloud system
BORNEO
S. CHINA SEA
Bintulu
Stratiform
Precipitation
Houze et al.
1981
Diurnal gravity wave generation of mesoscale
convection over coastal South America
Pacific
Andes
South America
Pacific
Andes
South America
Mapes et al. 2003
Summer MONEX (1979)
JASMINE (1999)
1999
Johnson & Houze 1987
Location of Ship during JASMINE on-station time
NOAA Ship
Ronald H. Brown
Bay of Bengal
Equator
60E
100E
Webster et al. 2002
Percent High Cloudiness in the Summer Monsoon
May-September 1999
< 235 K
850 mb wind
< 210 K
300 mb wind & sfc pressure
Zuidema 2002
Location of cloud systems by horizontal dimension
May-September 1999
Cloud
Top
< 210 K
r < 85 km
r = 85-140 km
r = 140-210 km
r > 210 km
Zuidema 2002
Diurnal cycle, mean percent high cloudiness, 1999
Cloud Top < 210 K
Zuidema 2002
South Asian Topography
JASMINE Mesoscale Convective Systems
Defined & tracked by 218 K infrared threshold
Zuidema 2002
JASMINE 1999, Ship Track & Satellite Data
85-90 E
Ship
Track
Webster et al. 2002
IR Temperature
08:30 LST
IR Temperature
11:30 LST
IR Temperature
14:30 LST
IR Temperature
17:30 LST
IR Temperature
20:30 LST
IR Temperature
20:30 LST
Ship radar
JASMINE 1999
Ship Radar Data
2345 LST 22 May 99
0215 LST 23 May 99
0615 LST 23 May 99
JASMINE 1999
Ship Radar Data
Reflectivity
Reflectivity
Doppler Radial Velocity
22 May 1999
2300 LST
JASMINE 1999
Ship Radar Data
Reflectivity
Reflectivity
Doppler Radial Velocity
22 May 1999
2143 LST
23 May 1999 0650 LST
JASMINE
Ship Radar
Data
TRMM
Precipitation
Radar Swath
TRMM Precipitation Radar shows extensive stratiform structure
23 May 1999 0650 LST
Cloud Radar on ship shows cirrus anvil extension
TRMM PR
Cloud Radar
Cloud Radar
TRMM PR
SUMMER MONEX
6 July 1979
850 mb wind
Houze & Churchill 1987
Microphysics
SUMMER MONEX
6 July 1979
20N
NOAA P3 Aircraft
Radar
20N
14N
14N
88E
92E
88E
92E
Houze & Churchill 1987
Flight Level Temperature (deg C)
SUMMER MONEX
Microphysics, All P3 flights, 3-8 July 1979
-25
-20
Columns
Plates &
Dendrites
Columns
Aggregates &
Drops
Dendrites
-15
-10
Plates
-5
0
Needles
*
*
Melting
Aggregates
Drops
Relative Frequency of Occurrence
Houze & Churchill 1987
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 propagation—consistent 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
TRMM Observations of Convection over Land
in the Himalayan Region
2002-2003
TRMM
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
TRMM Satellite Instrumentation
l = 2 cm
Important! PR
measures 3D
structure of radar
echoes
Kummerow et al, 1998
Idealized Horizontal Pattern of the Radar Echo
Pattern in a Mesoscale Convective System
Radar reflectivity
Echo type
Plan View
Houze 1997
Conceptual Model of Vertical Structure
“Convective” Rain Elements
Houze 1997
Conceptual Model of Vertical Structure
“Stratiform ” Rain Elements
Houze 1997
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.
echo
core
3D radar echo bounded
by 40 dBZ contour
“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
Height (km)
16
28N
8
0
74E
76E
55
Distance (km)
110
Analysis Subregions
°N
Western
Subregion
Central
Subregion
Arabian
Sea
INDIA
Eastern
Subregion
Bay of
Bengal
°E
Normalized Frequency Distribution
of 40 dBZ Convective Echo Core Heights
In western region-graupel particles
lofted to great
heights by strong
updrafts
Lightning Frequency Based on TRMM Satellite
Observations
Lightning
evidently results
from graupel
particles lofted to
great heights—in
NW region
Barros et al. 2004
“Wide Convection” Core: 22 July 2002, 13:09 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
Height (km)
16
30N
72E
76E
8
0
120
Distance (km)
240
Cumulative Distribution of Convective Core Breadth
In western
region—wide
convective areas
more frequent
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
“Broad Stratiform” Case: 5 June 2003, 13:47 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
Echo
Classified
4.5 km
level as
Stratiform
30N
28N
4.5 Section
km level
Cross
30N
Height (km)
16
8
0
22N
24N
94E92E
100E
98E
22N
288
Distance (km)
92E
576
100E
Cumulative Distribution Function
for Stratiform Precipitation Areas
In western
region—wide
stratiform areas
less frequent
TRMM Satellite Instrumentation
l = 2 cm
Important! PR
measures 3D
structure of radar
echoes
Kummerow et al, 1998
Contoured Frequency by Altitude Diagram
All data
1648 overpasses
Relative
frequency of
occurrence
Stratiform
Convective
Reflectivity Statistics by Sub-Region, Rain-Type, & Altitude
Convection is
stronger &
deeper in west
Stratiform more
pronounced in
east
Terrain Elevation Categories
°N
°E
Lowland 0-300 m, Foothills 300-3000 m, Mountain >3000 km
Mountain
Foothills
Lowland
Reflectivity Statistics by Subtending Terrain
Convection is
slightly deeper &
stronger over the
lowlands than
the foothills
Locations of Intense Convective Cases and Wide Stratiform
Cases
Intense Convective
°N
Wide Stratiform
Concentration in
concavities:
• West--Intense
convection
• East--Stratiform
systems
°E
Wide Area of Convection Case: 1309 UTC 22 July 2002
00 UTC Soundings
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
Convection intense—rimed particles lofted to 17+ km, electrification
 Stratif. regions—larger where unmodified maritime flow extends over land
Near & over mountains
Convection most frequent close to mountains, esp. in concavities
Convection strongest just upstream of mountains, & over foothills
Intense convection occurs at boundary of moist flow & downslope dry flow
THE END
Thanks for your attention