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Slide 1 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting FY-3 satellite data tuning and assimilation Qifeng Lu National Satellite Meteorological.

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Presentation on theme: "Slide 1 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting FY-3 satellite data tuning and assimilation Qifeng Lu National Satellite Meteorological."— Presentation transcript:

1 Slide 1 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting FY-3 satellite data tuning and assimilation Qifeng Lu National Satellite Meteorological Center, CMA, Beijing ECMWF Thanks to all who contributed to this work

2 Slide 2 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting Outline Microwave sounding data in NWP and climate research: operational satellites from the US, Europe & China : Chinas FY-3A satellite: The Microwave Temperature Sounder (MWTS) Identifying and characterising MWTS biases using NWP fields: Passband shifts Radiometer non-linearities Improved Assimilation of MWTS Initial Assessment of FY-3B Summary and conclusion Next Steps: Early results from the evaluation of MSU and AMSUA from

3 Slide 3 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting US Europe China Microwave sounding data provides information on temperature and humidity which has been widely used in : Operational NWP data assimilation systems and; Climate research – to determine long term trends in atmospheric state The US has launched a series of polar satellites, dating back to 1978; Europe began to contribute in 2006 (MetOp-A) China began to contribute in 2008 (FY-3A) Operational Sounding Satellites

4 Slide 4 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting The importance of MW sounding data in NWP Largest positive impact (per system) is obtained from microwave temperature sounding data Forecast sensitivity to observations (FSO) Is an adjoint based technique for assessing the influence of observing systems on forecast accuracy (from C. Cardinali, ECMWF)

5 Slide 5 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting 5 ok Microwave Temperature Sounder (MWTS) 4 channel (~MSU) Microwave Humidity Sounder (MWHS) 5 channel (~MHS) Infrared Atmospheric Sounder (IRAS) 20 channels (~HIRS/3) Microwave Radiation Imager 10 channels (~AMSR-E) The FY-3A/B Instrument Suite

6 Slide 6 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting Approach involves a comparison of observations (OBS) with simulated observations based on short range (up to T+9 hour) forecast fields (First Guess, FG) and radiative transfer modelling FG departures FG is proxy for truth FG departures (OBS – FG) indicate error in the measurements or RT modelling High accuracy of the NWP fields results from the large & diverse range of observations assimilated (MW sounders, Advanced IR sounders, GPSRO, radiosondes … etc) Able to detect biases at ~0.1K level for temperature sounders (MWTS and IRAS), sensitivity slightly lower for MW humidity sounders & imagers (~0.5K) Similar work ongoing at NOAA/NCEP, UK Met Office and DWD Initial Data Quality Assessment at ECMWF: General Approach

7 Slide 7 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting Initial FY-3A Evaluation

8 Slide 8 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting Microwave Temperature Sounder Microwave Humidity Sounder Infrared Sounder Microwave Imager STDEV (first guess departures): measures the misfit between model & measurement (in T B space) FY-3A data quality is comparable with MetOp/Aqua equivalents Initial Data Quality Assessment at ECMWF: Comparison of FY-3A with MetOp & Aqua

9 Slide 9 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting Full System OSEs: Full System + FY-3A VASS suite (MWTS, MWHS, IRAS) T511, 3 month experiment positive impact from FY-3A The impact of the FY-3A data is : neutral in SH slightly positive in the NH Initial Data Quality Assessment at ECMWF: Assimilation Experiments

10 Slide 10 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting Characterising MWTS biases using NWP fields

11 Slide 11 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting Comparison of MWTS and AMSU-A Brightness Temperatures State dependent inter-satellite (MWTS vs AMSU-A) biases: Region 1 (tropics): MWTS TBs warm relative to AMSU-A Region 2 (high northern latitudes) : No significant bias Brightness temperature map from cycle Characterize the MWTS 1 2

12 Slide 12 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting Schematic of error terms

13 Slide 13 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting MWTS-2 MWTS-3MWTS-4 First Guess Departures (K),i.e., Observation minus Simulation Pre-launch measured passband Optimised passband from line-by-line modelling uncertainties of ~32-55 MHz detected and corrected Non-linearity corrected AMSU-A equivalent Characterising the FY-3A MWTS: Detecting and Correcting passband errors and Non-linearities

14 Slide 14 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting Characterising the FY-3A MWTS: Assessing corrections in the CMA-GRAPES model Pre-launch measured passband Optimised passband Optimised + non-linearity corrected the corrections, developed at ECMWF, improve the (OBS-GRAPES_MODEL) fits.

15 Slide 15 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting MWTS OSEs Forecast Verification: Z at 200, 500 and 700 hPa Improvement due to MWTS data Normalised differences in RMS Errors in Z, verified against own analysis 90% confidence intervals shown Small improvements in SH in going from: original data recalibrated (low weight) recalibrated (high weight) NH close to neutral with some benefit in recalibrated data PRELAUNCH_MWTS (full system + original MWTS data) HIOBSERR_MWTS (Full system + optimised MWTS with low weight) LOWOBSERR_MWTS (Full system + optimised MWTS with high weight)

16 Slide 16 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting MWTS: current status Ground system changes implemented at CMA, March 2011 STD of 0.2 K is normally monitored MetOp AMSU-A Ch. 9FY-3A MWTS-4

17 Slide 17 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting Initial FY-3B Evaluation

18 Slide 18 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting FY-3B MWTS FG Departure Channel 3: GHz Correction of passband measurement bias and radiometer non-linearity has been implemented in pre-processing at NSMC/CMA No significant problems with the MWTS-2 and -3 observations Cross scan bias is dominant & accounts for non-gaussian FG departures (corrected by variational bias correction scheme): After VarBC STDEV(O-FG) = 0.17 K

19 Slide 19 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting FY-3B MWTS FG Departure Channel 4: GHz Strong cross scan biases & regional biases detected Variational bias correction unable to significantly reduce these biases Work is ongoing to improve the correction of these anomalies

20 Slide 20 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting MWTS FG Departure

21 Slide 21 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting

22 Slide 22 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting

23 Slide 23 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting

24 Slide 24 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting Summary FY-3A data has been evaluated at ECMWF through a comparison with simulated radiances & full assimilation experiments in which FY-3A data is introduced in the ECMWF system. The study revealed, and corrected, biases in FY-3A MWTS related to : Uncertainties in the passband centre frequencies Radiometer non-linearities These corrections bring the MWTS data close to the quality of equivalent AMSU-A data & in assimilation experiments this MWTS data delivers improvements in forecast accuracy. The high value of NWP in Cal/Val of new satellite sensors has been clearly demonstrated – further improvements in FY-3A and FY-3B data are expected, and it is hoped NWP will again play a crucial role for FY-3C, …. FY-3G ! A powerful new general approach to diagnosing an important group of biases affecting microwave sounders has been developed. This work demonstrates the significant benefits of close collaboration between satellite agencies and NWP centres.

25 Slide 25 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting Next Steps: Initial results from an evaluation of MSU and AMSUA from 1978

26 Slide 26 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting MSU CH3 (54.96 GHz): NOAA-6 to NOAA-14 Frequency Shift / MHz STD(FG_DEP) Improvement in STD(FG_DEP) LbL modelling based on ERA-Interim fields 1 cycle per month: Blue dots represent FG_DEP after shift correction Colour dots before

27 Slide 27 The 4th THORPEX-Asia Science Workshop and 9th ARC Meeting Finally … Thanks ! We would also like to acknowledge the contribution of colleagues from across the world (from CMA, ECMWF, UK Met Office and others besides) who made this work possible And finally - thanks to the local organizing committee for their hospitality here in the wonderful city of Kunming !


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