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GV for Taiwan ’ s precipitation retrieval research. Wann-Jin Chen Chung Cheng Institute Technology of National Defense University, Taiwan. Outline. Introduction Estimates of Rainfall using TMI data over the Ocean during Mei-Yu and Typhoon season
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GV for Taiwan’s precipitation retrieval research Wann-Jin Chen Chung Cheng Institute Technology of National Defense University, Taiwan
Outline • Introduction • Estimates of Rainfall using TMI data over the Ocean during Mei-Yu and Typhoon season • Estimates of Rainfall using TMI data over the Land during Mei-Yu and Typhoon season • Ground Validation • Future work
Two Heavy rainfall Season • Mei-Yu (Meso-scale convective systems), occurred during May and June. • Typhoon occurred during August through October. • Many natural disasters in Taiwan areas caused by the two weather systems, so the following studies were focused on them.
Estimates of Rainfall using TMI data over the Oceanduring Mei-Yu season
Methodology Match-up with TMI_Tb and Rain Gauge
Typhoon SINLAKU GMS-2002-09-05_1400 TMI-2002-09-05_1407
Quantification Validation during Mei-Yu season 1998~2001 18 points R2= 0.812
Estimates of Rainfall using TMI data over the Oceanduring Typhoon season
Rainfall Rate (mm/hr) by Regression. #37769 (this study) Typhoon MINDULLE Rainfall Rate (mm/hr) by 2A12. Delta Rainfall Rate (mm/hr).
Validation R=0.74, RMS=3.75 mm/hr, Bias: 0.68 (1.24%) , Points=66 (CO:25, ST:41) CO :● Convective ST : + Stratiform Average Rain Rate of Rain Gauge : 4.9 mm/hr. Average Rain Rate of Estimated : 5.6 mm/hr.
Validation (2A12) R=0.45, RMS=5.76 mm/hr, Bias=2.52 (-0.29%), Points: 66
Estimates of Rainfall using TMI data over the Landduring Typhoon season
Data Collection The scan patterns and resolutions of TRMM sensors, including TMI, PR, and VIRS. The illustration is a scatter of ground rain gauge in Taiwan
Scattering Index over Land( SIL ) Equation • Developing Scattering Index over Land( SIL ) equation for Taiwan land area. • Using TRMM/TMI 19.35V, 21.3V and 85.5V GHz channel. • Under non-scattering atmosphere conditions, that identified weather as cloud-free on Taiwan region with GOES-9 IR images.
The Rainfall Retrievals over Land • The scatter diagrams of the SIL and Gauge Rain rate Gauge Rain rate (mm/hr) Sample:74 SIL(K) RR(rain rate) = 0.126 SIL 1.239
Validating the Accuracy of Estimated Rainfall over land _TyphoonAERE(sample:23)
Validating the Accuracy of Estimated Rainfall over land _TyphoonMINDULLE (sample:74)
Error analysis : time difference • Satellite rainfall retrievals have a good result when comparing with rain gauge with 10 min. later after satellite overpass for the Mei-Yu cases.
Over the land _ Mei-Yu Validating the Accuracy of Estimated Rainfall with QPESUMS Data ( -/+: before/after satellite overpass)
RMS June May ( -/+: before/after satellite overpass ; ‘0’: same time )
Correlation Coefficient June May ( -/+: before/after satellite overpass ; ‘0’: same time )
Gauge Rain rate(mm/hr) Gauge Rain rate(mm/hr) Estimated Rainfall (mm/hr) Estimated Rainfall (mm/hr) The scatter diagrams of the estimated rainfall and the Gauge Rain rate Correlation Coefficient :0.82 Correlation Coefficient :0.81 Rainfall Retrievals derived from LRCT(2005) (left), Ferraro (1994) (right) ( Black solid line is the regression line between Est.-RR and rain gauge RR, and the red solid line is for the equivalent values between them. )
Error analysis : terrain effect • Satellite rainfall retrieval underestimated on upsloping side of the mountain and overestimated on the downsloping side of the mountain.
lee side facing wind side
facing wind side lee side
Future works • Improve rain gauge QC. • Develope more algorithms for other weather systems in Taiwan area. • Use more passive microwave radiometer sensors, like AMSR, AMSU in our algorithm. • Compare satellite rainfall retrievals with those derived from ground-based radar.