IV WMO Impact Workshop 2008

IV WMO Impact Workshop 2008 Alexander Cress

Global impact studies at the Deutscher Wetterdienst (DWD)Alexander Cress, Reinhold Hess Detlef Pingel Andreas Rhodin Heinz Werner Bitzer

German Weather Service , Offenbach am Main, GermanyEmail: [email protected]

• Introduction

• Impact of satellite sounding data from ATOVS radiances

• Quality and impact of radio occultation data

• General impact of atmospheric motion vector winds

• Impact of MTSAT-1R AMV wind vectors

• Use of direct broadcasting MODIS winds

• Use and impact of scatterometer data (ASCAT)

• Summary and Outlook

Global Model GME

• Operational NWP Model of DWD

• gridpoint model, hexagonal triangular grid

• 40 km mesh size, 36870 grid points/layer

• 40 layers (hyprid, sigma/pressure)

• prognostic variables: ps, u, v, T, qv, qc, qi, o3

• intermitient data assimilation (OI, 3-hourly) -> 3DVAR (PSAS) system

• incremental digital filter initialization (P.Lynch)

• At 00 UTC and 12 UTC: forecasts for 174 hours

• At 18 UTC: forecasts for 48 hours

IV WMO IMPACT WORKSHOP 2008 Alexander Cress


Assimilation of IFS Pseudo Temps

Profiles of IFS/4D-Var Analyses (temperature, humidity and wind)as Temps for OI/GME

use of humidity profiles only above 700 hPa

Assimilation one time per day for 0 UTCinto Main Analysis only

Data Coverage

(operational since Dec 17 2003)


Use of Satellite Radiances (ATOVS)

• AMSU-A of NOAA 15, 16, 18 and AQUA (on top of pseudo-temps) METOP/AMSU-A in trial run

• 1D-Var retrievals assimilated by OI as SATEMS (geopotential thicknesses)(only 1D-Var analysis increments assimilated)

• Tuning of background and observation errors for 1D-Var

• Assimilation with reduced resolution (120km, previously 60 km)with neutral impact

• Use of IFS forecasts above GME model top (10 hPa) for RTTOVstudies with statistical linear regression from stratospheric channels

• Direct Use of ATOVS radiances in 3D-VAR

AIRS/IASI:

• monitoring, cloud detection, bias correction, trial runs, etc. available

• work deferred for personal resources


Use of AMSU-A auf NOAA-15, 16, 18 und AQUA – since 5.7.2007

IV WMO Impact Workshop 2008

500 hPA ANOC, 0 UTC, for Routine, 4638 (Pseudo+1D-VAR)

1D-Var (with PT) further improves compared to Routine (with PT) for 0 UTC

Alexander Cress

IV WMO Impact Workshop 2008

Improvement of GME forecasts with tuned error statistics:

Red: old R and B, Blue: tuned R and B

Tuning of Covariance Matrices B and R for 1D-Var

Alexander Cress


Anomaly correlation coefficient of geopotential height in 500 hPa2007051400 – 2007053100 (18 forecasts)


Anomaly correlationcoefficient for 500 hPa2008030112 – 2008032612 (26 forecasts)

NH SH

Use of AMSU-A Data from METOPUse of AMSU-A Data from METOP

Reinhold HessDWD, Offenbach

Offenbach, 2007


Use of AMSU-A auf NOAA-15, 16, 18 und AQUA – since 5.7.2007


Use of AMSU-A auf NOAA-15, 16, 18, AQUA und METOP-A (seit 21.11.07)


Bias correction of Metop-1: Without Bias correction


Bias correction of Metop-1: after Bugfix in scanangle correction


Use of METOP: clear positive benefit of 500hPa ANOC in SH, minor impact for EUR at 00 UTC


Use of METOP: small positive impact of the 500hPa ANOC in NH and EUR for 12 UTC

Parallelroutine: clear positive impact for all areas (00 UTC)

Measurement geometry of Radio Occultation

Use of Radio Occultation data

• A electromagnetic signal, transmitted by a GPS satellite, is delayed due to the presence of free electrons in the ionosphere an the refractivity of the atmosphere

• The refractivity is directly linked to horizontal and vertical variation of temperature, pressure and water vapour

• The refraction of the GPS signal corresponds to a shift in its phase, recorded at the receiving LEO satellite. Additionally, the signal path undergoes a bending in the atmosphere, resulting in a bending angle

• Relative geometry of the GPS and LEO and the Earth changes during the occultation event, the signal path intersects the atmosphere vertically, thus providing a vertical profile of bending angle.

• Observation error can be derived from the signal-noise-ratio of the amplitude of the signal

• Observed quantity to be assimilated can be bending angle (DWD) or refractivity (Met Office) profiles

• Benefits: High vertical resolution, independence of cloud conditions, lack of fundamental biases, uniform global coverage


AMV Impact Experiment

• Following an initiative by Mary Forsythe and Lars Peter Riishojgaard

• Data denial experiment with 3DVAR

• No use of geostationary and polar AMV wind vectors

• Winter period (12th Dez. 2007 – 12th January 2008)

• 00 UTC and 12 UTC forecasts


00 UTC

12 UTC

Anomaly correlation coefficient for the Geopotential Height in 500 hPa20071212 - 20080112

CrtlCrtll without AMVs


RMSV Wind Vector in 200 hPa2007121212 - 2008011212

NH SH

TR

RoutineRoutine without AMVs


Analysis and forecast impact of MTSAT-1R

• Usage• extratropics over oceans; tropics over oceans and land

• IR between 1000 and 700 hPa and above 400 hPa• QI > 85

• WVcloudy above 400 hPa• QI > 85

• WVclear is not used• VIS below 700 hPa

• QI > 85

• FG check: asymmetric to remove negative OBS-FG bias

• Thinning: 1 wind per pre-defined thinning box (200 km;15 vertical layers). data selection by highest noFirst Guess QI in a box

• One month analysis and forecast experiment (June/July 2007)


OBS – FG Statistics for MTSAT-1R for July 2007> 400 hPa QI > 80

IR WVcloudy


CrtlCrtl plus MTSAT-1R



NH SH

EU

Anomaly correlation coefficentDate: 2007060912 - 2007070912


Direct Broadcast MODIS Winds

• Motivation and Usage

MODIS polar winds are not available in time to be used in operational(main) run. Only available in update run

Direct broadcasting winds from Tromso, McMurdo ~ 100 minutes earlier

Provide only partial coverage and only Terra can be received in the NH

At DWD, no MODIS winds could be used in the main runs. Using DB winds, some polar winds can be used also in the main run. Additionally, more polar winds can be used in the update cycle runs

Monitoring results show same quality as conventional MODIS winds

Experimental use of DB polar winds in the same way as conventional MODIS winds

Experiment: 23 days in November 2007

Read SCATT (25 km BUFR data)Data from data base or file or ECMWF MARS System

Pre SCATT- read in original Bufr- data selection within analyses time window- eliminates overlapping orbits- computes KNMI rain flag; data flaging- computes direction check; data flagging- computes bias correction- data selection based on quality control - thinning- output options: Bufr; netCDF, ascii

OI - Analyses- (u/v) most likely wind- coded as Pseudo-Buoy (Bufr)

3DVAR - Analyses- (u/v) more than one wind- coded as Bufr/netCDF

Offline Monitoring- colloc. with GME -FG/Ana- analyses of data quality

Use of scatterometer data at DWD

• 10 m wind vectors (most likely wind)

• QuikScat and ASCAT

• Global and regional

• Use of multiple wind solutions (planned)

• Experiments with OI and 3DVAR



Scatterometer Data Coverage2008022500 +/- 1.5 H

ASCAT (red) QuikScat (blue)


CrtlCrtl plus ASCAT

CrtlCrtl plus ASCAT

Anomaly correlation coefficient for sea level pressurePeriod: 2007070812 – 2007080812

Northern Hemisphere Southern Hemisphere

IV WMO IMPACT Workshop 2008 Alexander Cress

AN

OC

CrtlCrtl plus ASCAT

Time series of anomaly correlation coefficient for EuropeMean sea level pressure VV=72h

Start of the forecasts 00 UTC


Summary I

• Satellite sounding data from TOVS radiances are most important data source

• AMSU-A radiance data from Metop A are very import for NWP in Europe

• AMV wind vectors are still a valuable observation source for NWP at DWD

• Quality information of the AMV’s are very important

• Positive impact of MODIS winds and MTSAT-1R after height assignment correction

• Direct broadcast MODIS winds very helpful to get polar winds into main forecast run (short cut-off)


Summary II

• ASCAT wind observations smaller bias than QuikScat. No bias correction

• Scatterometer data have positive impact of single analyses/forecast

• General small positive impact on forecast quality for both hemispheres predominantly on the Southern Hemisphere

• Small structures are difficult to analyses due to broad scale error correlation functions

• Radio occultation is a new and promising data source for NWP

• Bending angles are assimilated at DWD. Benefit: High vertical resolution, independence of cloud conditions, near uniform global coverage and lack of biases

• Impact on Southern Hemisphere half the impact of AMSU A radiances


Outlook

• 3D-VAR (PSAS) assimilation system will become operational in summer 2008

• New computer platform at DWD (IBM -> NEC 9X)

• Use of AMSU-B and MHS sounding profiles

• Use of sounding profiles from the IASI instrument onboard of Metop

• Use of wind profiler and VAD winds (USA, Europe, Japan)

• New scatterometer from India (ISCAT) should become available

• Investigate the impact of AVHRR polar wind vectors and AMV wind vectors from the Chinese satellite Fenyun

• Use of lidar wind profiles from the ADM space mission of ESA

IV WMO Impact Workshop 2008

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