MODIS Winds Assimilation Impact Study with the CMC Operational Forecast System Réal Sarrazin Data Assimilation and Quality Control Canadian Meteorological Centre Meteorological Service of Canada Workshop on Short-to-Medium Range Regional NWP in the Arctic and Antarctic Fairbanks, Alaska, October 8-10, 2003 Environnement Canada Environment Canada Centre météorologique canadien Canadian Meteorological Centre

Observations

Satellite Winds Selection Procedure Geostationary Satellite winds: GOES-P / W / E, METEOSAT-7 / 5 Time window: within 90 minutes from analysis time Levels: VI below 700 hPa, WV above 400 hPa, IR all levels Wind speed: > 2.5 m/s Angle: < 55 deg. Land Mask: over ocean, over land south of 20°N and above 400 hPa quality indicator above threshold value: METEOSAT QI > 85, GOES-W / E: RFF 700 hPa extra-tropics tropics horizontal thinning: 1.5 X 1.5 deg. (priority: obs time, QI) Quality Control Background check done before the horizontal thinning during the analysis, Variational QC with asymetric condition for the AMVs

No SATWINDS experiments, 17 June 2002 to 31 July 2002 RMS of forecast Wind speed errors at 250 hPa e02cntrl: control, e02nosw: no AMVs, e02noto: no TOVS, e02nohu: no HUMSAT, e02nosat: no satellites

No SATWINDS experiments, 17 June 2002 to 31 July 2002 anomaly correlation GZ 500 hPa

MODIS Winds Assimilation Impact Trial Data obtained by ftp from CIMSS in near real time Assimilation Period: 18 July 2003 to 23 August 2003, same cut-off time as for the operational observations, T+6 at 06/18UTC, T+9 at 00/12UTC Evaluation Period: 5 weeks from 20 July to 23 August 2003, 6-day Forecast twice per day at 00 and 12 UTC, from the analyses of the assimialtion cycle. verification scores against radiosonde observations and against analyses.

RFF quality indicator versus “observation minus first guess” statistics for High level MODIS winds, infrared channel (using the control first-guess). Plotted are the RMSVD, average wind speed, wind speed bias and number of observations per 0.01 bin. The average model wind speed is slightly higher in the Arctic But the RMSVD values are lower than the Antarctic A NRMSVD gives higher values for the Antarctic WV winds (not shown) exhibit similar characteristics Period: 20 July – 08 August 2003 Arctic above, Antarctic below

The characteristics of the statistics are similar to those of GOES winds Including the shift of the distribution toward higher RFF values (and lower mean wind speed) for lower levels winds IR channel, statistics stratified in 3 layers, Arctic Region

QI quality indicator versus “observation minus first guess” statistics for High level MODIS winds, infrared channel (using the control first-guess). Plotted are the RMSVD, average wind speed, wind speed bias and number of observations per 0.01 bin. RMSVD values are almost constant, values for the Antarctic are higher Average wind speed increases with increasing QI values so NRMSVD increases Arctic above, Antarctic below, Period: 20 July – 08 August 2003

Satellite Winds Selection Procedure MODIS winds: Terra / Aqua Time window: within 90 minutes from analysis time Levels: IR above 700, WV above 550 hPa Wind speed: > 2.5 m/s Land Mask: over ocean, over land above 400 hPa quality indicator above threshold value: RFF < horizontal density thinning: average of ~180 km (priority: obs time, qi) Quality Control Background check done before the horizontal thinning during the analysis, Variational QC with asymetric condition for the AMVs (no observation height reassignment)

Example of AMVs distribution for one analysis, 28 august 12UTC

MODIS Winds trial, period: 20 July 2003 to 23 August hour Forecasts Verification against radiosondes, N of 60°N, Arctic RMS: solid lines Bias: dashed lines Control: blue lines MODIS: red lines There is a small negative impact (increased rms) on the errors of the forecasts in the Arctic UU: east-west wind component UV: wind speed GZ: geopotential heights TT: temperature

MODIS Winds trial, period: 20 July 2003 to 23 August hour Forecasts Verification against radiosondes, S of 60°S, Antarctic RMS: solid lines Bias: dashed lines Control: blue lines MODIS: red lines There is a negative impact on the errors of the forecasts in the Antarctic UU: east-west wind component UV: wind speed GZ: geopotential heights TT: temperature

MODIS Winds trial, period: 20 July 2003 to 23 August hour Forecasts Verification against radiosondes, Northern Extratropics RMS: solid lines Bias: dashed lines Control: blue lines MODIS: red lines There is little impact on the errors of the forecasts in the Northern Hemisphere UU: east-west wind component UV: wind speed GZ: geopotential heights TT: temperature

MODIS Winds trial, period: 20 July 2003 to 23 August hour Forecasts Verification against radiosondes, Southern Extratropics RMS: solid lines Bias: dashed lines Control: blue lines MODIS: red lines There is a small negative impact on the errors of the forecasts in the Southern Hemisphere UU: east-west wind component UV: wind speed GZ: geopotential heights TT: temperature

MODIS Winds trial, period: 20 July 2003 to 23 August 2003 Forecasts Verification against analyses, Anomaly correlation, N of 60°N and S of 60°S

MODIS Winds trial, period: 20 July 2003 to 23 August 2003 Forecasts Verification against analyses, Anomaly correlation, extratropics

MODIS Winds trial, period: 20 July 2003 to 23 August 2003 Forecasts Verification against analyses, Wind Speed errors RMS, N of 60°N and S of 60°S

Conclusion For this first relatively short trial, Verifications of the forecasts against radiosondes show a small negative impact from the MODIS winds, especially for the Antarctic Verifications of the forecasts against analyses show mixed results generally negative but with some positive impacts on winds speeds forecast quality at mid levels Longer trials are necessary before implementation