gerb thermal flux regional bias: detection and correction by comparison with ceres

17
GIST, 27-29/4/2005 GERB thermal flux regional bias: detection and correction by comparison with CERES S. Dewitte Royal Meteorological Institute of Belgium

Upload: lilian

Post on 06-Feb-2016

36 views

Category:

Documents


0 download

DESCRIPTION

GERB thermal flux regional bias: detection and correction by comparison with CERES. S. Dewitte Royal Meteorological Institute of Belgium. Overview. Methodology Night time GERB CERES comparison Day time GERB CERES comparison MS5 MS7 comparison Validation ADM corrections. Methodology. - PowerPoint PPT Presentation

TRANSCRIPT

Page 1: GERB thermal flux regional bias: detection and correction by comparison with CERES

GIST, 27-29/4/2005

GERB thermal flux regional bias: detection and correction by comparison with CERES

S. Dewitte

Royal Meteorological Institute of Belgium

Page 2: GERB thermal flux regional bias: detection and correction by comparison with CERES

GIST, 27-29/4/2005

Overview

Methodology Night time GERB CERES comparison Day time GERB CERES comparison MS5 MS7 comparison Validation ADM corrections

Page 3: GERB thermal flux regional bias: detection and correction by comparison with CERES

GIST, 27-29/4/2005

Methodology Radiative flux at the top of the atmosphere: F (W/m2) Satellite observations: radiances L (W/m2sr) Satellite viewing zenith angle vz

F = L (vz) / R(vz)

GERB: fixed vz

Validation GERB fluxes: comparison with CERES fluxes with variable vz

Page 4: GERB thermal flux regional bias: detection and correction by comparison with CERES

GIST, 27-29/4/2005

Used data GERB: ARG fluxes, SEVIRI as imager,

Version 2 CERES FM3: RAPS or GERB mode or

special scan, use of inflight calibration 1-6/2004 use of night and day data for thermal fluxes CERES data is colocated to nearest GERB

ARG pixel

Page 5: GERB thermal flux regional bias: detection and correction by comparison with CERES

GIST, 27-29/4/2005

Regional difference – night time

Page 6: GERB thermal flux regional bias: detection and correction by comparison with CERES

GIST, 27-29/4/2005

GERB – CERES difference fit

Impose linear variation with vz :f(vz)=(52.5°- vz)/ 52.5°

Fit difference as function of GERB flux:Fgerb-Fceres=a(Fgerb). f(vz)+b(Fgerb)

a(Fgerb) = GERB nadir error

Corrected GERB flux = Fgerb - a(Fgerb) . f(vz)

Page 7: GERB thermal flux regional bias: detection and correction by comparison with CERES

GIST, 27-29/4/2005

Difference versus flux – night time

Page 8: GERB thermal flux regional bias: detection and correction by comparison with CERES

GIST, 27-29/4/2005

All scenes – night time

Before correction After correction

Page 9: GERB thermal flux regional bias: detection and correction by comparison with CERES

GIST, 27-29/4/2005

Daytime LW comparison

Page 10: GERB thermal flux regional bias: detection and correction by comparison with CERES

GIST, 27-29/4/2005

Day and night time LW nadir error

Page 11: GERB thermal flux regional bias: detection and correction by comparison with CERES

GIST, 27-29/4/2005

MS7 – MS5 difference fit

OLR estimate from MS5: Fms5

OLR estimate from MS7: Fms7

Comparison for July 2004 Fit difference as function of MS7 flux:

Fms7-Fms5=a(Fms7). f(vz,ms7)-b(Fms7).f(vz,ms5)+c(Fms7)

a(Fms7) = MS7 nadir error b(Fms7) = MS5 nadir error

Page 12: GERB thermal flux regional bias: detection and correction by comparison with CERES

GIST, 27-29/4/2005

Page 13: GERB thermal flux regional bias: detection and correction by comparison with CERES

GIST, 27-29/4/2005

Page 14: GERB thermal flux regional bias: detection and correction by comparison with CERES

GIST, 27-29/4/2005

Page 15: GERB thermal flux regional bias: detection and correction by comparison with CERES

GIST, 27-29/4/2005

Without correction

Cold cloud correction

Page 16: GERB thermal flux regional bias: detection and correction by comparison with CERES

GIST, 27-29/4/2005

Full correction

Page 17: GERB thermal flux regional bias: detection and correction by comparison with CERES

GIST, 27-29/4/2005

Conclusions Theoretical thermal ADM errors are

identified from comparsions of– Night time GERB / CERES FM3 – Day time GERB / CERES FM3 – MS5 / MS7

The remaining differences are– within +/- 15 W/m2 over hot desert– within +/- 5 W/m2 elsewhere