microphysical considerations in remote sensing of precipitation daniel rosenfeld, hebrew university...
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Microphysical Considerations in Remote Sensing of Precipitation
Daniel Rosenfeld, Hebrew University of Jerusalem, Israel andVincenzo Levizzani, ISAC-CNR, Bologna, Italy
Namibia, MSG 2003 09 07 11:57 2_4r_9
0.8 m
3.9r m
10.8 m
New geostationary multispectral capabilities allow us to retrieve cloud microstructure and precipitation forming processes
0 5 10 15 20 25 30 35
-40
-30
-20
-10
0
10
20
reff
T [
oC
]
m]
Glaciated
Mixed PhaseRainout
Coalescence
General
Diffusional growth
0 5 10 15 20 25 30 35
-40
-30
-20
-10
0
10
20
reff
T [
oC
]
m]
Glaciated
Mixed Phase
Rainout
Coalescence
Maritime
0 5 10 15 20 25 30 35
-40
-30
-20
-10
0
10
20
reff
T [
oC
]
m]
Glaciated
Mixed Phase
Coalescence
Continental - moderate
Diffusional growth
0 5 10 15 20 25 30 35
-40
-30
-20
-10
0
10
20
reff
T [
oC
]
m]
Glaciated
Mixed Phase
Continental - extreme
Diffusional growth
The classification scheme of convective clouds into microphysical zonesaccording to the shape of the temperature – effective radius relations
Note that in extremely continental clouds re at cloud base is very
small, the coalescence zone vanishes, mixed phase zone starts at T<-15oC, and the glaciation can occur at the most extreme situation at the height of homogeneous freezing temperature of –39oC. In contrast, maritime clouds start with large re
at their base, crossing the precipitation threshold of 14 m short distance above the base. The deep rainout zone is indicative of fully developed warm rain processes in the maritime clouds. The large droplets freeze at relatively high temperatures, resulting in a shallow mixed phase zone and a glaciation temperature reached near –10oC
Rosenfeld and Lensky, 1998
MSG 2004 08 26 15:12 2_4r_9
More vigorous and less maritime
Very maritime with warm rain
Extremely continental
Disdrometer measured DSD of continental and maritime rainfall, as microphysically classified by VIRS overpass. The DSD is averaged for the rainfall during +- 18 hours of the overpass time. The disdrometers are in Florida (Teflun B), Amazon (LBA), India (Madras) and Kwajalein.Application of TRMM Z-R shows a near unity bias in maritime clouds, but overestimates by a factor of 2 rainfall from continental clouds.
0.01
0.1
1
10
100
1000
0 1 2 3 4 5 6
Florida ContFlorida MarLBA ContLBA MarIndia ContIndia MarKwaj Mar
N [
mm
m-3
\ m
m h
r-1]
D [mm]
Rosenfeld and Woodley, Meteorological Monographs, 2003
Processes determining the Rain Drop Size Distribution
Equilibrium DSD: Z = 600 R; D0e = 1.75 mmHu and Srivastava (1995)
1
10
100
0 50 100 150 200
Time for reaching equilibrium DSDTime for main features of DSDe
Tim
e f
or
reac
hin
g e
qu
ilib
riu
m D
SD
[m
in]
R [mm h-1]
Lifetime of a falling element in a deep rainshaft
Impact of Cloud DSD on the evolution of Rain DSD
Maritime Cloud DSDCloud drop coalescenceDrizzleDrizzle coalescence RaindropsMore coalescence larger raindropsbreakup and equilibrium DSD•Approaching D0e from below
Continental Cloud DSDCloud drop accretiongraupel haillarge raindropsbreakup equilibrium DSD•Approaching D0e from above
Trends of D0 for convective maritime and continental clouds.Rain water content, W [g m-3] as a function of rain drop median mass diameter D0 [cm] and drop concentration NT [m-3] for R=30 mm h-1, For all Z-R’s.
102
103
104
105
0.5
1
1.5
2
2.5
3
0.05 0.1 0.15 0.2 0.25 0.3 0.35
NT(30) W(30)
NT(3
0) [
m-3
] W(30) [g
m-3]
D0(30) [cm]
DSD All, R=30 mm hr -1
ContinentalMaritime
Equilibrium
The variation of drop median mass diameter D0 with the liquid water content (W) and total drop concentration (NT) for R=10 and 30 mm hr-1 of convective rainfall in
maritime and continental regimes.
102
103
104
105
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0.05 0.1 0.15 0.2 0.25
NT(10) W(10)
NT(1
0) [
m-3
]
W(1
0) g m
-3
D0(10) [cm]
E
WarmOrographic
C o n v e c t i v e
MaritimeIntermediate
Continental
TropicalStratiform
Hurricane
DSD All, R=10 mm hr -1
102
103
104
105
0.5
1
1.5
2
2.5
3
0.05 0.1 0.15 0.2 0.25 0.3 0.35
NT(30) W(30)
NT(3
0) [
m-3
] W(30) [g
m-3]
D0(30) [cm]
DSD All, R=30 mm hr -1
E
C o n v e c t i v e
MaritimeIntermediate
Continental
TropicalStratiform
Hurricane
WarmOrographic
Summary: All Z-R classifications combined
Differences in rain DSD forming processes between Maritime and Continental Clouds:
In Maritime clouds there are:More Coalescence Rainout D0 < D0e Larger R(Z) Lower updrafts Smaller D0 Larger R(Z) Less evaporation Smaller D0 Larger R(Z)
In Continental clouds there are:Less Coalescence No Drizzle No small rain drops Hydrometeors start as graupel and hail D0 > D0e Smaller R(Z)Larger updrafts Larger D0 Smaller R(Z)More evaporation Larger D0 Smaller R(Z)
.
1. Swiss Locarno thunderstorms, continental (Joss and Waldvogel , 1970) 830 1.502. Arizona mountain thunderstorms (Foote 1966)
646 1.463. North Dakota, September.
429 1.594. Illinois thunderstorms, continental (Sims, 1964) 446 1.435. Oklahoma thunderstorms, moderate continental (Petrocchi and Banis, 1980) 316 1.366. Congo Squall line. Tropical continental (Sauvageot, 1994) 425 1.297. PurtoRico thunderstorms. Coastal, moderate maritime (Ulbrich et al., 1999). 261 1.438. Darwin Squalls. Coastal, tropical maritime (Maki et al., 2001) 232 1.389. Darwin Convective DSD. Coastal, tropical maritime (Tokay et al., 1995) 175 1.3710. COARE Convective DSD. Equatorial maritime (Tokay and Short, 1996). 139 1.4311. Marshall Trade wind cumulus. Warm rain maritime (Stout and Mueller, 1968) 126 1.4712. Marshall Showers. Equatorial maritime. (Stout and Mueller, 1968) 146 1.42E. Equilibrium DSD. 600 1.00
Z-R relations for rainfall from maritime and continental convective clouds. The rain intensities for 40 and 50 dBZ are plotted in the figure. Note the systematic increase of R for a given Z for the transition from continental to maritime clouds.
10
100
Lo
carn
o T
S
Ari
zon
a T
S
N.D
ako
ta S
ept
Illin
ois
TS
Okl
aho
ma
TS
Co
ng
o S
qu
all
Pu
rto
Ric
o T
S
Dar
win
Sq
ual
ls
Dar
win
Co
nv
DS
D
CO
AR
E C
on
v D
SD
Mar
shal
l Tra
de
Mar
shal
l Sh
ow
ers
Eq
uili
bri
um
DS
D
R(40 dBZ)
R(50 dBZ)
R [
mm
/ h
r]
Type:
R (Z) Convective: Continental - Maritime
1E1211109876543
1 2
MSG 2003 05 20 13:42 2_4r_9 Highly Continental SAHEL
Moderate Equatorial
MODIS Aerosol Optical Thickness, 2001
S. Nesbitt and E. ZipserS. Nesbitt and E. Zipser
ITCZ clouds cleaner Larger cloud drops Smaller raindrops and less and smaller ice aloft less PR and TMI over-estimate
S. Nesbitt and E. ZipserS. Nesbitt and E. Zipser
MODIS Aerosol Optical Thickness, 2001
ITCZ clouds cleaner Larger cloud drops Smaller raindrops and less and smaller ice aloft less PR and TMI over-estimate
MODIS Aerosol Optical Thickness, 2001
S. Nesbitt and E. ZipserS. Nesbitt and E. Zipser
ITCZ clouds cleaner Larger cloud drops Smaller raindrops and less and smaller ice aloft less PR and TMI over-estimate
MODIS Aerosol Optical Thickness, 2001
S. Nesbitt and E. ZipserS. Nesbitt and E. Zipser
ITCZ clouds cleaner Larger cloud drops Smaller raindrops and less and smaller ice aloft less PR and TMI over-estimate
SummaryA review of Z-R relations based on cloud physics RDSD forming processes revealed that Z-R behave systematically,producing larger R for the same Z when going from:Continental Maritime (X3)Maritime Orographic (X4)Stratiform Convective Maritime (X2)
OpportunitiesClassification criteria can be detected by:Satellite (cloud drop effective radius for continentality);Radar 3-D structure; Dynamics of orographic lifting.Potential for dynamic Z-R for space and ground based radars, accounting for systematic biases by factors of 2 to 4.Potential for guiding selection of PMW libraries
…RAINCLOUDS