Microphysical Considerations in Remote Sensing of Precipitation Daniel Rosenfeld, Hebrew University of Jerusalem, Israel and Vincenzo Levizzani, ISAC-CNR,

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

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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

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105

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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


102

103

104

105

0.5

1

1.5

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2.5

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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]


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










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

Documents

Microphysical Considerations in Remote Sensing of Precipitation Daniel Rosenfeld, Hebrew University of Jerusalem, Israel and Vincenzo Levizzani, ISAC-CNR,