Status of AIRS Data at Met Office A. Collard , R. Saunders, J. - PowerPoint PPT Presentation

Status of AIRS Data at Met Office A. Collard , R. Saunders, J. Cameron, Y. Takeuchi, P. Rayer and B. Harris n Data monitoring n Cloud detection n Bias tuning n Data assimilation plans AIRS Net Meeting, 24 th February 2003

Data monitoring n BUFR radiance data are compared with 6hr forecast fields from the Met Office global model n Results from these comparisons are placed on our monitoring pages (password protected) n Plots updated at 8Z each day n Maps of O-B for all 324 channels for clear fovs n Selected spectra and O-B spectra n The plots show time series of past 3 months – % rejections from 1DVar q/c checks – Observed-Background mean and st. dev. AIRS Net Meeting, 26 Feb 03

Monitoring web page Available to the AIRS team in mid-December via password protected page on Met Office site. AIRS Net Meeting, 26 Feb 03

Time series of observations Global Observations: 4/5th Dec 2002 21Z-3Z AMSU CO 2 Rejects caused by H 2 O Channel 2357 O 3 CO 2 AIRS Net Meeting, 26 Feb 03

Tartan Plots: O-B clear mean bias Global Observations AMSU 1&2 CO 2 H 2 O O 3 CO 2 AIRS Net Meeting, 26 Feb 03

20-70N O-B st. dev plots Stratosphere 20-70S 20N-20S Water vapour AIRS Net Meeting, 26 Feb 03

Day & Night spectra AIRS Net Meeting, 26 Feb 03

Ocean skin to bulk temperature model validation with ATSR n Night time satellite/buoy June 1995 – June 1997, n=1243 matchups ATSR-2 – buoy skin effect Fairall model skin effect n Spatial match to within 1/6 degree/temporal match within 1 hour n Fairall model for skin effect n Can “convert” satellite skin SST to bulk using model! Horrocks et al., JGR, in press AIRS Net Meeting, 26 Feb 03

Bias tuning for AIRS Predictors being investigated n Scan angle n Model T skin n Model Thickness 850-300 hPa n Model Thickness 200-50 hPa n Simulated brightness temperature n Model total column water n Model Lapse rate convolved with Jacobian AIRS Net Meeting, 26 Feb 03

Example of HIRS-12 bias tuning Corrected biases Uncorrected biases AIRS Net Meeting, 26 Feb 03

Cloud detection methodology Cloud detection AIRS Net Meeting, 26 Feb 03

PCA cloud detection Attempt to determine the probability of having cloud in the field of view given the observed radiances and the NWP background profile obsb () =D- yxyy 112bbbobs Ln{(|,)} ~(){()()}()Constcloud. JP - D=-++D- T T 1 J ( y ) S ( y ) - = D D y T 1 1 ( ) UX U ( y ) - - = D D 11 ()/ NNTjjiiiij yUX == =D ÂÂ is the i th component of y D AIRS Net Meeting, 26 Feb 03

Cloud detection: Results from simulated dataset PCA3 PCA2 PCA01 PCA01 Red is clear Green is liquid water cloud Blue is ice cloud AIRS Net Meeting, 26 Feb 03

Cloud detection: Validation PCA scheme VAR scheme Blue Jc<2 Blue Jc<.94 Green Jc>2 Green Jc>.94 Red Jc>20 Red Jc>20 AIRS Net Meeting, 26 Feb 03

Assimilation trials n Once initial bias tuning has been finalised will start assimilation trials in March (as planned). n Period will be October-November 2002, several poorly forecast and well forecast storms during this period. n Control will be current operations which includes: – ATOVS (HIRS/AMSU-A/AMSU-B) – SeaWinds – SSM/I winds n Plan to report on results of trials by August 03 n Met Office relocation will delay possible operational use of AIRS until 2004 AIRS Net Meeting, 26 Feb 03

Summary n AIRS continues to perform well and O-B stats are stable and as expected. See web pages. n Cloud detection (clear FOV) schemes using VAR+PCA investigated. VAR scheme used for initial trials. n Radiance bias correction is being implemented n We hope to begin assimilation trials in March. AIRS Net Meeting, 26 Feb 03