MODIS Winds Assimilation Impact Studywith the CMC Operational Forecast System

Réal SarrazinData Assimilation and Quality Control

Canadian Meteorological CentreMeteorological Service of Canada

Workshop on Short-to-Medium Range Regional NWPin the Arctic and Antarctic

Fairbanks, Alaska, October 8-10, 2003

Environnement Canada Environment CanadaCentre météorologique canadien Canadian Meteorological Centre

Environment CanadaCanadian Meteorological Centre

Environnement CanadaCentre météorologique canadien

CMC Data Assimilation Cycles06 UTC 12 UTC 18 UTC 00 UTC

48 hReg Fcst

Global and Regional Data Assimilation Cycles on model

levels at CMC

OBST + 6h

Global Analysis

6 hGlo Fcst

Global Analysis

6 hGlo Fcst

Global Analysis

6 hGlo Fcst

Global Analysis

6 hGlo Fcst

6 hGlo Fcst

Global Analysis

OBST + 6h

OBST + 9h

OBST + 9h

OBST + 9h

6 hReg Fcst

Regional Analysis

6 hReg Fcst

Regional Analysis

OBST + 1h40

48 hReg Fcst

6 hReg Fcst

Regional Analysis

6 hReg Fcst

Regional Analysis

OBST + 1h40

OBST + 5h30

OBST + 5h30

Global Analysis

Global Analysis

OBST + 3h

240 hGlo Fcst

OBST + 3h

Global Analysis

OBST + 3h

240 hGlo Fcst

144 hGlo Fcst

00 UTC

Observations

Upper air soundings radiosonde pilot dropsonde

land stations ships aircraft

temperature moisture winds pressure

Surface observations synoptic

land stations ships fixed buoys drifting buoys

temperature moisture pressure winds

Satellite NOAA ATOVS amsu-a & amsu-b

circumpolar radiance

GOES imager geostationary radiance

AMVs geostationary (METEOSAT & GOES)

winds

circumpolar (Terra & Aqua)

winds

Aircrafts ACARS/AMDAR AIREP

temperature winds

Satellite Winds Selection ProcedureGeostationary 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 <400 401-700 >700 hPa extra-tropics 65 70 75

tropics 70 75 80

•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 2002RMS 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 2002anomaly 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 forHigh level MODIS winds, infrared channel (using the control first-guess).Plotted are the RMSVD, average wind speed, wind speed biasand 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 forHigh level MODIS winds, infrared channel (using the control first-guess).Plotted are the RMSVD, average wind speed, wind speed biasand 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 <400 401-700 65 70

•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 200324-hour Forecasts Verification against radiosondes, N of 60°N, Arctic

RMS: solid linesBias: dashed lines

Control: blue linesMODIS: red lines

There is a small negativeimpact (increased rms) on the errors of theforecasts in the Arctic

UU: east-west wind componentUV: wind speedGZ: geopotential heightsTT: temperature

MODIS Winds trial, period: 20 July 2003 to 23 August 200324-hour Forecasts Verification against radiosondes, S of 60°S, Antarctic

RMS: solid linesBias: dashed lines

Control: blue linesMODIS: red lines

There is a negativeimpact on the errors of theforecasts in the Antarctic

UU: east-west wind componentUV: wind speedGZ: geopotential heightsTT: temperature

MODIS Winds trial, period: 20 July 2003 to 23 August 200324-hour Forecasts Verification against radiosondes, Northern Extratropics

RMS: solid linesBias: dashed lines

Control: blue linesMODIS: red lines

There is little impacton the errors of theforecasts in the NorthernHemisphere

UU: east-west wind componentUV: wind speedGZ: geopotential heightsTT: temperature

MODIS Winds trial, period: 20 July 2003 to 23 August 200324-hour Forecasts Verification against radiosondes, Southern Extratropics

RMS: solid linesBias: dashed lines

Control: blue linesMODIS: red lines

There is a small negativeimpact on the errors of theforecasts in the SouthernHemisphere

UU: east-west wind componentUV: wind speedGZ: geopotential heightsTT: temperature

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

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

MODIS Winds trial, period: 20 July 2003 to 23 August 2003Forecasts 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 negativeimpact 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 qualityat mid levels

Longer trials are necessary before implementation