Kazumasa Aonashi (MRI/JMA)Kazumasa Aonashi (MRI/JMA)Takuji Kubota (Osaka Pref. Univ.)Takuji Kubota (Osaka Pref. Univ.)

Nobuhiro Takahashi (NICT)Nobuhiro Takahashi (NICT)

3rd IPWG3rd IPWG 　　WorkshopWorkshop

Oct.24, 2006

　

Developnemt of Passive Microwave Developnemt of Passive Microwave Precipitation Retrieval Algorithm Precipitation Retrieval Algorithm

Towards the GPM EraTowards the GPM Era

Satellite Microwave Radiometers

TRMMTMIPR

AquaAMSR-E

DMSPSSM/I

ADEOS-IIAMSR

MWRs with window channels

GPM （Global Precipitation

Measurement:）（ 2013～）

3hourly Observation

Main SatelliteDPRGMI

Constellation Sat MWRs (8?)

Passive Microwave Precipitation RetrievalPassive Microwave Precipitation Retrieval

GSMaP Retrieval AlgorithmGSMaP Retrieval AlgorithmGlobal Satellite Mapping of Precipitation Project started in 2003. Leader: Prof. Ken’ich Okamoto (Osaka Pref. Univ.)Funded by JST/CREST The goal is to produce accurate precip map using mainly satellite microwave radiometer.Passive microwave precip retrieval algorithm is based on Aonashi and Liu (2000).

OutlineOutline

IntroductionIntroduction

GSMaP MW Retrieval AlgorithmGSMaP MW Retrieval Algorithm

Retrieval Algorithm (V4.7.2)Retrieval Algorithm (V4.7.2)

Validation using radar and gauge dataValidation using radar and gauge data

Improvement of the Scattering partImprovement of the Scattering part

GSMaP MW Retrieval AlgorithGSMaP MW Retrieval Algorithmm

Retrieval Algorithm (V4.7.2)Retrieval Algorithm (V4.7.2)

GSMaP Precip Retrieval AlgorithmGSMaP Precip Retrieval Algorithm

Over Land:Over Land:

Scattering by frozen parScattering by frozen particles ticles

(TBs at 37 & 85GHz)(TBs at 37 & 85GHz)

Over Ocean:Over Ocean: Scattering (37 & 85GHz) Scattering (37 & 85GHz)

++ Radiation from RainRadiation from Rain (TBs at 10 & 19 GHz)(TBs at 10 & 19 GHz)

ObservedTBs

Precip.

FLHPrecip ProfilesDSDinhomogeneity

Look-up

Table

Forward calculationRetrievalCalculation

Passive microwave precipitation retrievalPassive microwave precipitation retrieval

parameters

Forward CalculationForward Calculation

Liu’s RTM (1998) is used to calculate TLiu’s RTM (1998) is used to calculate TBs Bs

Mixed-phase precip is parameterized wiMixed-phase precip is parameterized with Takahashi & Awaka (2005).th Takahashi & Awaka (2005).

Parameters (FLH, precip profiles) are giParameters (FLH, precip profiles) are given as the a priori information.ven as the a priori information.

Nishitsuji Model (N model)Nishitsuji Model (N model)

On the basis of the filed experiment, the following parameters are modeledVolume liquid water fraction （ Pw)shape parameter of the dielectric constant (U)DSD parameter (B) is a function of Pw Density ρ=√PwFall velocity Magono-Nakamura(1965) for snow and Foot and Du Toit for rain

0 0.5 1

1

0.5

0100 102 104 106

PW

Dis

tan

ce b

elo

w B

B (

km)

U

U

PW

UP

UP

UP

U a

aa

i

ii

w

ww

s

s

1111

cm)in radius :(a )( 10)( 130

mmmNDN Ba

Pw and U profile Relationship between B and Pw

Implicitly including break-up/coalescence processes

10–3 10–2 10–1 100

20

40

PW

B B

Lookup table (TB-R) for variable Lookup table (TB-R) for variable Freezing Level Height (FLH)Freezing Level Height (FLH)

Melting layer model shows slightly better representation than rain only model.

Procedure:Rain rate from PR is integrated within TMI’s 10 GHz footprint weighted by the antenna pattern.

Forward CalculationForward Calculation

Liu’s RTM (1998) is used to calculate TLiu’s RTM (1998) is used to calculate TBs Bs

Mixed-phase precip is parameterized wiMixed-phase precip is parameterized with Takahashi & Awaka (2005).th Takahashi & Awaka (2005).

Parameters (FLH, precip profiles) are giParameters (FLH, precip profiles) are given as the a priori information.ven as the a priori information.

Classification of types

Profile for each Types

Database for types

2.5 deg. gridSeasonal8types（ Sea 3, Land 5）

Database for Profile

For precip. types surface precip.

Precipitation profiles for Type 1 0.5, 1, 2, 3, 4, 6, 8, 10, 15, 20, 30, 40, 60, 80, 120, 160, 200 mm/h

Precip [mm/h]

Hei

ght　

（km）

Type-1

Parameters used in the Algorithm:Parameters used in the Algorithm:Precipitation Types and Profiles (TRMM PR)Precipitation Types and Profiles (TRMM PR)

Atmospheric variables (FLH, SSW, SST) are derived from the Global Analysis data of JMA

Parameters used in the Algorithm:Parameters used in the Algorithm:Atmospheric variables (GANAL)Atmospheric variables (GANAL)

ObservedTBs

Precip.

FLHPrecip ProfilesDSDinhomogeneity

Look-up

Table

Forward calculation

RetrievalCalculation

To find the optimal precipitation that giTo find the optimal precipitation that gives RTM-calculated TBs fitting best witves RTM-calculated TBs fitting best with the observed TBs.h the observed TBs.

Basic Idea of the Retrieval AlgorithmBasic Idea of the Retrieval Algorithm

parameters

Precipitation Retrival Algorithm

Screening of Precip Areas

Scatter-based Precip Estimation

First-guess of over-sea Precipitation

Minimization of Σ(TBc-TBo)**2

Observed TBs

rain37 PCT37+LUTrain85 PCT85+LUT

rain flag

rain10V TB10V+LUT (sigma)

rain19V TB19V+LUT (sigma)

Retrivals

LOOK-UP TABLE(LUT)

sigma (inhomogeneity)

Comparison withComparison with

PR.2A25PR.2A25

Ground radar Ground radar

(Okinawa, (Okinawa, KWAJ)KWAJ)

GPCC (rain GPCC (rain gauge)gauge)

Validation using Radar & gaugesValidation using Radar & gauges

Relative Error with PR (1998-2004)Relative Error with PR (1998-2004)Error=100 × |TMI – PR|/PR %

Average over （ 1998～ 2004）

LAND OCEANTropic Mid Tropic Mid

GSMaP(V4.6)

9.3% 10.6% 6.6% 13.5%

GSMaP(V4.7)

7.5% 6.2% 8.9% 8.2%

GSMaP(V4.7.2)

9.5% 7.3% 6.4% 9.8%

GPROF 45.1% 16.2% 7.2% 5.5%

Tropic（ 15S～ 15N）

Mid（ <15S or > 15N）

Zonal Mean Precip over Ocean(1998Zonal Mean Precip over Ocean(1998 ～～ 2004) 2004) PR3G68, GPROF.v6, GSMaP.v4.7.2 PR3G68, GPROF.v6, GSMaP.v4.7.2

3G68 V6 PRGPROF V6 TMIGSMaP V4.7GSMaP V4.7.2

3G68 V6 PRGPROF V6 TMIGSMaP V4.7GSMaP V4.7.2

3G68 V6 PRGPROF V6 TMIGSMaP V4.7GSMaP V4.7.2

3G68 V6 PRGPROF V6 TMIGSMaP V4.7GSMaP V4.7.2

Zonal Mean Precip over Land (1998Zonal Mean Precip over Land (1998 ～～ 2004) 2004) PR3G68, GPROF.v6, GSMaP.v4.7.2 PR3G68, GPROF.v6, GSMaP.v4.7.2

3G68 V6 PRGPROF V6 TMIGSMaP V4.7GSMaP V4.7.2

3G68 V6 PRGPROF V6 TMIGSMaP V4.7GSMaP V4.7.2

3G68 V6 PRGPROF V6 TMIGSMaP V4.7GSMaP V4.7.2

3G68 V6 PRGPROF V6 TMIGSMaP V4.7GSMaP V4.7.2

Comparison with ground-based radar Comparison with ground-based radar

Corretation ： 0.79 （ No:253 ）RMSE ： 1.46 mm/hr

Correlation： 0.65（ No:1139）RMSE： 1.78 mm/hr

COBRA(Okinawa) KWAJ

Integrated 6-hour Microwave radiometer Integrated 6-hour Microwave radiometer Precipitation MapPrecipitation Map

(TMI+AMSR+AMSR-E+F13,F14,F15 SSM/I; Jul., 2003)(TMI+AMSR+AMSR-E+F13,F14,F15 SSM/I; Jul., 2003)

MissingValues

Comparison with GPCC dataComparison with GPCC dataGSMaP_MWR ： monthly mean preciptation (1x1 deg)

GPCC Monthly Precipitation (Monitoring) Product （ Rudolf et al. 2006 ）：

Correlation： 0.80（ Number： 5974)

Improvement of the Scattering Improvement of the Scattering partpart

Retrieval Algorithm (V5.1)Retrieval Algorithm (V5.1)

(rainsurf/rain.4.7.2).vs.stdlgpr and Toplev (rainsurf/rain.4.7.2).vs.stdlgpr and Toplev over Tropical Land, July, 1998over Tropical Land, July, 1998

STDLGPR(inhomo)

Precip. Top level

Scattering part (V5.1)Scattering part (V5.1)

Dual-frequency (37,85GHz)

Retrieval of rain37 uses parameters from rain85

Horizontal inhomogeneity

Precipitation top level

PCT85 vs Precip. topSigma85 vs STDLGPR

Comparison with PR 3G68 over Land Comparison with PR 3G68 over Land (July, 1998)(July, 1998)

V4.7.2 V5.1

SummarySummary

GSMaP passive microwave precipitation retrieval algorithm.The retrieved precipitation agreed well with PR, radar data over ocean.The over-land algorithm underestimated the strong precipitation.Introduction of the retrieved inhomogeneity alleviated the underestimation.

END

Thank you.