Kazumasa Aonashi (MRI/JMA) Takuji Kubota (Osaka Pref. Univ.) Nobuhiro Takahashi (NICT) 3rd IPWG Workshop Oct.24, 2006 Developnemt of Passive Microwave Precipitation Retrieval Algorithm Towards the GPM Era

Satellite Microwave Radiometers TRMM TMI PR Aqua AMSR-E DMSP SSM/I ADEOS-II AMSR MWRs with window channels GPM （ Global Precipitation Measurement: ） （ 2013 ～） 3hourly Observation Main Satellite DPR GMI Constellation Sat MWRs (8?)

Passive Microwave Precipitation Retrieval GSMaP Retrieval Algorithm Global Satellite Mapping of Precipitation Project started in 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).

Outline Introduction GSMaP MW Retrieval Algorithm Retrieval Algorithm (V4.7.2) Validation using radar and gauge data Improvement of the Scattering part Improvement of the Scattering part

GSMaP MW Retrieval Algorithm Retrieval Algorithm (V4.7.2)

GSMaP Precip Retrieval Algorithm GSMaP Precip Retrieval Algorithm Over Land: Scattering by frozen particles Scattering by frozen particles (TBs at 37 & 85GHz) (TBs at 37 & 85GHz) Over Ocean: Scattering (37 & 85GHz) + Scattering (37 & 85GHz) + Radiation from Rain Radiation from Rain (TBs at 10 & 19 GHz) (TBs at 10 & 19 GHz)

Observed TBs Precip. FLH Precip Profiles DSD inhomogeneity Look-up Table Forward calculation Retrieval Calculation Passive microwave precipitation retrieval parameters

Forward Calculation Liu’s RTM (1998) is used to calculate TBs Mixed-phase precip is parameterized with Takahashi & Awaka (2005). Parameters (FLH, precip profiles) are given as the a priori information.

Nishitsuji Model (N model) On the basis of the filed experiment, the following parameters are modeled Volume liquid water fraction （ Pw) shape parameter of the dielectric constant (U) DSD parameter (B) is a function of Pw Density ρ=√Pw Fall velocity Magono-Nakamura(1965) for snow and Foot and Du Toit for rain Pw and U profileRelationship between B and Pw Implicitly including break-up/coalescence processes B

Lookup table (TB-R) for variable 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 Calculation Liu’s RTM (1998) is used to calculate TBs Mixed-phase precip is parameterized with Takahashi & Awaka (2005). Parameters (FLH, precip profiles) are given as the a priori information.

Classification of types Profile for each Types Database for types 2.5 deg. grid Seasonal 8types （ 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] Height （ km ） Type-1 Parameters used in the Algorithm: 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: Atmospheric variables (GANAL)

Observed TBs Precip. FLH Precip Profiles DSD inhomogeneity Look-up Table Forward calculation Retrieval Calculation To find the optimal precipitation that gives RTM-calculated TBs fitting best with the observed TBs. Basic 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 +LUT rain85  PCT85+LUT rain flag rain10V  TB10V+LUT (sigma) rain19V  TB19V+LUT (sigma) Retrivals LOOK-UP TABLE (LUT) sigma (inhomogeneity)

Rain85 & Rain.v4.7.2 vs Rainsurf over Tropical land, July, 1998 Rain85 W85*Rain85+W37*Rain37

Comparison with PR.2A25 PR.2A25 Ground radar Ground radar (Okinawa, KWAJ) (Okinawa, KWAJ) GPCC (rain gauge) GPCC (rain gauge) Validation using Radar & gauges

Relative Error with PR ( ) Error=100 × |TMI – PR|/PR % Average over （ 1998 ～ 2004 ） LANDOCEAN Tropic MidTropic 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% GPROF45.1%16.2%7.2%5.5% Tropic （ 15S ～ 15N ） Mid （ 15N ）

Zonal Mean Precip over Ocean(1998 ～ 2004) PR3G68, GPROF.v6, GSMaP.v G68 V6 PR GPROF V6 TMI GSMaP V4.7 GSMaP V G68 V6 PR GPROF V6 TMI GSMaP V4.7 GSMaP V G68 V6 PR GPROF V6 TMI GSMaP V4.7 GSMaP V G68 V6 PR GPROF V6 TMI GSMaP V4.7 GSMaP V4.7.2

Zonal Mean Precip over Land (1998 ～ 2004) PR3G68, GPROF.v6, GSMaP.v G68 V6 PR GPROF V6 TMI GSMaP V4.7 GSMaP V G68 V6 PR GPROF V6 TMI GSMaP V4.7 GSMaP V G68 V6 PR GPROF V6 TMI GSMaP V4.7 GSMaP V G68 V6 PR GPROF V6 TMI GSMaP V4.7 GSMaP V4.7.2

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

Comparison with GPCC data GSMaP_MWR ： monthly mean preciptation (1x1 deg) GPCC Monthly Precipitation (Monitoring) Product （ Rudolf et al ）： Correlation ： 0.80 （ Number ： 5974)

Improvement of the Scattering part Retrieval Algorithm (V5.1)

(rainsurf/rain.4.7.2).vs.stdlgpr and Toplev over Tropical Land, July, 1998 STDLGPR (inhomo) Precip. Top level

Scattering part (V5.1) Dual-frequency (37,85GHz) Retrieval of rain37 uses parameters from rain85 Horizontal inhomogeneity Precipitation top level PCT85 vs Precip. top Sigma85 vs STDLGPR

Comparison with PR 3G68 over Land (July, 1998) V4.7.2V5.1

Comparison with PR 3G68 over Ocean (July, 1998) V4.7.2 V5.1

Summary 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.