Post on 19-Jan-2018
description
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