precipitation in the mediterranean region observed with trmm microwave data

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M. Kästner, The 2004 EUMETSAT Meteorological Satellite Conference, Prague, Czech Republic, 2 June 2004

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Precipitation in the Mediterranean region observed with TRMM microwave data

Martina Kästner & Jörg Steinwagner

German Aerospace Center

Applied Remote Sensing Cluster

Oberpfaffenhofen, Germany

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TRMM - Tropical Rainfall Measuring Mission

TRMM (Dec. 1997 – present) – NASA, NASDA

PRPrecipitation Radar

TMITRMM microwaveImager

VIRSVisible infrared Scanner

CERESClouds and Earth‘sRadiant system

LISLightning imagingsensor

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TRMM

TRMM = Tropical Rainfall Measuring Mission

orbit in 400 km altitude

inclination 35°

PR = precipitation radar TMI = TRMM Microwave Imager

Frequency 13.8 GHz 10.7, 19.4, 21.3, 37.0, 85.5 GHz

Swath 250 km 880 km Horiz. resolution 5 km 5 to 70 km Vert. resolution 250 m Sensitivity 0.7 mm/h

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TRMM TMI brightness temperatures

Spain

North Africa

19 h

19 v

85 v

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Synoptic situation on 10 Nov 2001

trough > cut-off low > cyclogenesis

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common area: 15W ... 20E, 30N ... 60Ncommon grid, common period, common format

40°

60°

50°

40°

30°

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Retrieval 1 yes no

yes hits misses

no false correctalarms negativesO

bser

ved

Retrieval 1 Retrieval 2

Falsealarms

Hits

Misses

Correct negatives

categorical statistics

contingency table

Ret

rieva

l 2

accuracy, bias sc., false alarm rate, probability of detection, threat sc., equivalent threat sc., Hansen-Kuipers- , Heidke skill score

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Intercomparisons

rain gauge

PMW

IR

combined MW/IR

mesoscale model

neural network

radar

common grid (~28 km): ¼ deg lat x ¼ deg lon

PMW vs. PMW

PMW vs. combined MW/IR

PMW vs. BOLAM

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Intercomparison: PMW vs. PMW - different retrievals

visual inspection - subjective - all shown gridded precips are from 10 Nov. 2001, 03 UTCshown statistics are from all data (08 to 12 Nov. 2001)

FDA_bham (TMI) (Ch. Kidd, 1998)frequency differencealgorithm

Spain

North Africa

PATER (P. Bauer, 2001)PR Adjusted TMI Estimation of Rainfall

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statistics (8-12 Nov 2001)

N = 3.353 PATER PATERrain no rain

FDA rain 84 297FDA no rain 299 2673

accuracy = 0.82bias score = 1.00

PATER

FD

A

similar quality, PATER-RR tend to higher valuesstatistics driven by correct negatives

PMW vs. PMW

the best example

PATER

FD

A

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Combined (MW+IR) vs. PMW

MW + IR combined(J. Turk)

MW : PATER (P. Bauer)

MW : FDA_bham (Ch. Kidd)

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model BOLAM vs. PMW

MWBOLAM(A. Buzzi)

MW : PATER (P. Bauer)

MW : FDA_bham (Ch. Kidd)

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retrieval 1 retrieval 2

Falsealarms

Hits

Misses

Correct negatives

categorical statistics

N = 67 834

hits = 9 %misses = 15 %false alarms = 14 %corr. negatives = 62 %

accuracy = 0.71bias sc. = 0.96far = 0.61pod = 0.38ts = 0.24ets = 0.11hk = 0.19hss = 0.71

summary of all intercomparisons 0.25° grid

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Application: monthly mean precipitation

Nov 2002

Jan 2003

Mar 2003

May 2003

PATER algorithm(PMW)0.25° resolution~ 28 km

0 20 40 60 80 100 mm/month

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Conclusion

Over the Mediterranean heavy rainfall events occur several times a year

Need of improved weather forecasting of heavy rainfall

Need of rainfall data from over the sea -> satellites

Intercomparison of different satellite rainfall algorithms incl. model data,common grid = 0.25° (~28 km)

PMW techniques are directly related to 3-D structure of hydrometeors, but low revisit time; performance better over oceans than over land

IR techniques are widely used, but the physical relation of cloud top temperature and rain rate is weak; advantage: high revisit time

Combined techniques PMW and IR – TRMM 3B42, Turk, PERSIANN, etc.

Application of PATER PMW satellite rain retrieval:winter rain over the southern Mediterranean Seaand adjacent North Atlantic in high spatial resolution;seasonal changes in monthly mean precipitation

Step towards highly resolved precip climatology over sea

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RR comparison - 1DD – 9-13 November 2001

r = 0.71n = 146

Results

Bauer approach PATERPR + TMI (AMW + PMW)

Validation with 1DD GPCC data:r = 0.71 (n=146)

Assessment: PIP-3 (Adler, 2002)best: r = 0.75

FAR – min detectable RR for PATER:17 mm/d = 0.7 mm/h = 0.05 g/m³ lwc

Outlook

Combination IR +MWbetter cloud models

precipitation in the mediterranean region observed with trmm microwave data

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