Impact study with observations assimilated over North America and the North Pacific Oceanat MSC

Stéphane Laroche and Réal Sarrazin

Environment Canada

4th Workshop on the impact of various observing systems on NWPGeneva, Switzerland, 19-21 May 2008

Main objectives

• Estimate the current value of radiosonde and aircraft data available over North America, as well as the impact of satellite data over the North Pacific Ocean

• Examine the propagation of the impacts over the North

American continent and the adjacent Atlantic Ocean

• Assess the sensitivity of the results with respect to the analysis scheme the resolution of the forecast model the weather regime

Network Variables Thinningradiosondes/dropsondes U, V, T, (T-Td), ps 28 levels

Surface reports

(SYNOPS, SHIPS, BUOYS)

T, (T-Td), ps,

(U, V over water)

1 report/6h

Aircraft

(BUFR, AIREP, AMDAR, ADS)U, V, T 1o x 1o x 50 hPa

ATOVS

NOAA 15-16-17-18, AQUA

Ocean Land

AMSU-A ch 4-10 ch 6-10

AMSU-B ch 2-5 ch 3-4

250 km x 250 km

Water vapor channel

GOES 11-12IM3

(6.7 )

2o x 2o

AMV

(Meteosat 5-7-8, GOES 11-12, MTSAT-1R)

U,V

(IR, WV, VI channels)

1.5o x 1.5o

MODIS

(Aqua, Terra)U,V 1.5o x 1.5o

Wind Profilers

(NOAA Network)U,V (750 m) Vertical

Data assimilation and forecast systems

Observations assimilated in the control experiments (Jan. and Feb. 2007)

- Analysis schemes: 4D-Var (6h window) and 3D-Var (FGAT)- Inner loop resolution: T108 (~180 km)- Outer loop resolutions: 100 km and 33 km

- Latest upgrade (2008) also includes AIRS, QuikSCAT and SSM/I data

Experiment Data typedenied

Region wheredata are denied

Data assimilation

scheme

Horizontal resolution of the forecast model

AI.NA.4D.LO Aircraft North America 4D-Var 100 km

AD.NA.4D.LO Ascent/Descent AI North America 4D-Var 100 km

RA.NA.4D.LO Radiosonde North America 4D-Var 100 km

ST.PA.4D.LO Satellite North Pacific 4D-Var 100 km

CT.4D.LO None - 4D-Var 100 km

AI.NA.3D.LO Aircraft North America 3D-Var 100 km

RA.NA.3D.LO Radiosonde North America 3D-Var 100 km

ST.PA.3D.LO Satellite North Pacific 3D-Var 100 km

CT.3D.LO None - 3D-Var 100 km

RA.WD.4D.LO Radiosonde World 4D-Var 100 km

RA.WD.3D.LO Radiosonde World 3D-Var 100 km

AI.NA.4D.HI Aircraft North America 4D-Var 33 km

AI.NA.3D.HI Aircraft North America 3D-Var 33 km

CT.4D.HI None - 4D-Var 33 km

CT.3D.HI None - 3D-Var 33 km

Observing System Experiments

North America Z500 RMSE for the control experiments and latest upgrade of the MSC global analysis-forecast system

Data denial and verification regions

Aircraft reports assimilated during January and February 2007and radiosonde stations (black dots)

Impact of radiosondes over North America(4D-Var / 100 km)

RMSE differences for Z500

Impact of aircraft data over North America(4D-Var / 100 km)

RMSE differences for Z500

Impact of satellite data over the North Pacific Ocean(4D-Var / 100 km)

RMSE differences for Z500

Impact of satellite data over the North Pacific Ocean(4D-Var / 100 km)

RMSE differences for U250

FIs for Z500 over regions of North America and North Atlantic

Radiosonde data denied over North America

Aircraft reports denied over North America

Ascent/Decent Aircraft reports denied over North America

Satellite data denied over the North Pacific Ocean

FIs for U250 over regions of North America and North Atlantic

Radiosonde data denied over North America

Aircraft reports denied over North America

Ascent/Decent Aircraft reports denied over North America

Satellite data denied over the North Pacific Ocean

Comparison of FIs for Z500 from 4D-Var and 3D-Var

Radiosonde data denied over North America

Aircraft reports denied over North America

Satellite data denied over the North Pacific Ocean

4D-Var 3D-Var

12h

48h

3D-Var 4D-Var

Impact of satellite data over the North Pacific OceanZ500

Impact of satellite data over the North Pacific OceanU250

12h

48h

3D-Var 4D-Var

24h

72h

Denial over North America Denial over the globe

Impact of global and local (North America) data-denialsZ500 RMSE differences for radiosonde data

4D-Var / 100 km

Radiosonde data denied over North America

4D-Var 3D-Var

Radiosonde data denied over the globe

Impact of global and local (North America) data-denialsZ500 RMSE differences for radiosonde data

Sensitivity to analysis scheme and model horizontal resolution 24h Z500 RMSE differences for aircraft data denied over North America

100 km

33 km

3D-Var 4D-Var

Sensitivity to analysis scheme and model horizontal resolutionFIs for Z500

3D-Var / 100 km aircraft data denied over NA

4D-Var / 33 km aircraft data denied over NA

3D-Var / 33 km aircraft data denied over NA

4D-Var / 100 km aircraft data denied over NA

4D-Var

3D-Var

Sensitivity to analysis scheme and model horizontal resolutionFIs for U250

3D-Var / 100 km aircraft data denied over NA

4D-Var / 33 km aircraft data denied over NA

3D-Var / 33 km aircraft data denied over NA

4D-Var / 100 km aircraft data denied over NA

4D-Var

3D-Var

Sensitivity to analysis scheme and model horizontal resolutionRMSE for Z500 and U250 over the United States

Z500 U250

100 km

33 km

Sensitivity to analysis scheme and model horizontal resolutionRMSE for Z500 and U250 over the United States

Z500 U250

100 km

33 km

Effect of the weather regime on the impacts

Z500Anomaly

Z50048h

RMSE diff.

January February

Effect of the weather regime on the FIs

January February

Radiosonde data over North America

Aircraft reports over North America

Satellite data over the North Pacific Ocean

Conclusions (1)• Summary of the impact results over North America for January and

February 2007:

The quality of the forecast over the Canadian Arctic heavily relies on the radiosonde network, even though surface stations and MODIS winds are assimilated.

Over the eastern part of the North American continent, the radiosonde and aircraft data are still the main contributors to the forecast skill at short forecast ranges, but beyond 48h the impact of satellite data available over the North Pacific Ocean may be greater depending on the weather regime.

The primary source of forecast improvements over the western North America is provided by the satellite data over the North Pacific Ocean, even at short forecast ranges.

Conclusions (2)• The impact of the radiosonde network over northern Canada is more

important in the 3D-Var context. Moreover, this impact is further enhanced when radiosonde data are omitted over the globe. Therefore, 4D-Var seems superior to 3D-Var to exploit the fewer observations available over northern Canada and is less sensitive to the removal of data outside that region.

• However, for the experiments in which the satellite data over the North Pacific Ocean, the impact with 3D-Var is not systematically larger than with 4D-Var: the short-range impact over the United States is more important in the 4D-Var context.

• We also found that the short-range impact is smaller in 4D-Var than in 3D-Var for Z500, but it is the opposite for U250. Further work is needed to explain why the impact variations are not the same for these fields when comparing 4D-Var and 3D-Var results.

• Overall, the impact results are less sensitive to the change of resolution of the forecast model than to the change of data assimilation scheme.

Conclusions (3)• The weather regime that prevails during the period under

investigation (i.e. January and February 2007) had a noticeable effect, especially on the propagation of the impact from the satellite data over the North Pacific Ocean at longer forecast ranges.

• As indicated by the variability of the results from the various sensitivity tests, the forecast impact over a given region may change by 5 to 15% depending on the analysis scheme, the forecast resolution, or the weather regime that prevails during the period investigated.

4th Workshop on the impact of various observing systems on NWPGeneva, Switzerland, 19-21 May 2008

Thank you for your attention!