Recent developments at DWD

[email protected] Radial Velocity, OPERA, LHN for COSMO-EUCOSMO GM, Sibiu, 2 September 2013 1

Recent developments at DWD

[email protected] Deutscher Wetterdienst, D-63067 Offenbach, Germany

based on experiments / plots by Klaus Stephan

• Direct Nudging of Radar Radial Velocity Data

• Status of OPERA

• Latent Heat Nudging for COSMO-EU


nudging of radar radial velocity:methodology

pre-processing , done twice (first use time, obs time) for each radar scan

1. at each observation point:

• correct observed radial wind for sedimentation speed of the hydrometeors

• calculate observation increment of radial wind component (at obs point)

(requires: - bi-linear interpolation of model horizontal wind to obs point- project model horizontal wind to radial direction )

• re-folding aliased measurements (according to quality flags of the obs)

• exclude all increments > ± 5 m/s



2. at certain model grid points (i,j) (e.g. every 20 km lat / lon) :create vertical profiles of pseudo obs (of radial velocity, as a kind of superobbing)

• assign all obs increments (at obs points)within ±1° (azimuth) and ±10 km (range)horizontally to this model grid point

• pseudo obs (of radial velocity)= radial comp. of model wind+ obs increment (at model level)

(i,j)range

20 km 2°(i,j)

model g. pts.

• get obs increments at model levelsas weighted average of increments at obs points(weights depends on height differences)

verticalcross

section



umod

vmod

upseudo

vpseudo

Radar

modelgrid pt.

pseudo observation in radial wind

current model horizontal wind

current model radial wind

current increment in radial wind

current target wind

azimuth processing in nudging at each time step : horizontalplain • project current model wind to radial direction

• current observation increment= pseudo observation of radial velocity - model radial velocity

• increment : - physically: radial velocity

- formally: wind vector, always

in radial direction ! treat like radiosonde wind increment in nudging scheme


nudging of radar radial velocity:results shown last year

control

nudge vr

0-UTC runsTSS

FF-10m RMSE

FF-10m bias, all sta. sta. < 100 m

sta. > 800 m300m < sta < 800m

100m < sta < 300m

These differences were due to

different external parameters !


nudging of radar radial velocity:verification against radar precipitation

1 – 27 May 2012

assimilation

threshold: 0.1 mm / h

control (COSMO-DE setup, with LHN)use of radial velocity added

FBI

ETS


threshold:0.1 mm / h

FSS, 11 g.pts. (30 km)

12-UTC forecast

runs

nudging of radar radial velocity:verif. vs. radar precipitation (1 – 27 May 2012)

00-UTC forecast

runs

ETS

control (C-DE setup, with LHN)use of radial velocity added


threshold:5.0 mm / h

FSS, 11 g.pts. (30 km)

nudging of radar radial velocity:verif. vs. radar precipitation (1 – 27 May 2012)

00-UTC forecast

runs

ETScontrol (C-DE setup, with LHN)

use of radial velocity added

12-UTC forecast

runs


nudging of radar radial velocity: summary

• nudging of radar radial velocity implemented

• still code problems with reproducibility (some error rel. to MPI communication)

• experiment May 2012 with additional use of vr (control with LHN !) :

small positive impact on (mainly strong) precipitation otherwise neutral no show cases with strong positive impact

• next: fix reproducibility problem, clean up code, check and improve efficiency include in official COSMO version, add few more tests, make it operational


Status of OPERA

• currently 27 member states with about 160 radar stations

• OPERA Phase 4 : spring 2013 – 2018 • Programme manager Elena Saltikoff (FMI)• User Group established (total 11 p. from NWP, hydrology, biology)

• three 2-D composites are available every 15 minutes:

• current rain rate, sum over last hour, current maximum reflectivity

• Phillipe Lopez (ECMWF) found out:

• quality has increased in 2013 (with Baltrad QC) but is still not sufficient everywhere

• best quality over UK, France, Poland and Germany

• underestimation over southern Europe

• underestimation in snow cases

• lots of spurious ground echoes

• software transforming it to COSMO grids available (Stephan)

[email protected] Radial Velocity, OPERA, LHN for COSMO-EUCOSMO GM, Sibiu, 2 September 2013

ODC composite

12 Aug 2013, 15 UTC

Status of OPERA

[email protected] Radial Velocity, OPERA, LHN for COSMO-EUCOSMO GM, Sibiu, 2 September 2013 Ref-Talk 19.09. 2012 Radial Wind Assimilation

Status of OPERA

‘EY composite: Input for LHN at DWD,

4 different storm-dep. Z-R relationships

OPERA DC composite (C-DE domain):

1 Z-R relationship

differences particularly for low precip rates; (erroneous spaital alignment ?)

12 Aug.2013

15 UTC


Status of OPERA

• 3-D reflectivity and radial wind:

• reflectivity sent by almost all member states,

radial wind only by few(but increasing)

(Courtesy Hidde Leijnse, * indicates max. number)

• HIRLAM already gets access to volume data, but possible also for other consortia

• dissemination of volume data to member states planned for end of 2014 (to be decided: with or without quality information ?)

• discussion about meta data / quality issues are ongoing(e.g. to distinguish ‘zero echo’ – ‘no data’ (compare with raw data))


Latent Heat Nudging for COSMO-EU

Motivation

•Reanalysis Project of HErZ would like to use LHN also on its larger domainconfiguration (COSMO-CORDEX, x = 7km)

•Does it work ?

Is there a negative interaction between LHN and the deep convection scheme ?

Experiments

•2 periods: Summer: August 2012 (incl. convective cases)

Winter: 1 Nov. – 15 Dec. 2012 (incl. snow cases)

•operational COSMO-EU setup (Cosmo V4_27, tk?min=0.4)

•operational LHN setup except: • no blacklist information used• no bright band detection• LHN within first 25 minutes of forecast (will be ~ 2.5h in operational run)


• same data as for COSMO-DE,

currently•17 German Doppler radar stations

quality controlled•2 Dutch stations•2 Belgian stations•9 France stations•3 Swiss stations•2 Czech stationssoon extended by 2 Polish stations

• every 5 minutes

• future: can be extended by OPERA composite outside COSMO-DE domain

LHN for COSMO-EU:radar data coverage


hourly precipitation at 2 Aug. 2012, 00 UTC + 4h

Radar Control (rout) LHN Experiment

LHN for COSMO-EU:case study


12 UTCLHNROUT

LHN for COSMO-EU:SYNOP verification, summer: positive


00 UTCLHNROUT

LHN for COSMO-EU:SYNOP verification, winter: slightly positive


Experiment ControlBIAS RMSE

LHN for COSMO-EU:TEMP verification, summer / winter: neutral


Assimilation 0.1 mm/hAssimilation 0.1 mm/h

LHNROUT

LHN for COSMO-EU:Verification against radar precip (summer)


12 UTC 0.1 mm/h 12 UTC 2.0 mm/h

00 UTC 2.0 mm/h00 UTC 0.1 mm/h


• LHN in COSMO-EU is beneficial; forecast impact:

• Summer:

• precipitation improved (esp. convective cases)

• most surface parameters improved

• Winter:

• most surface parameter slightly improved

• impact on precipitation and low stratus neutral

• Work started to extend data coverage using OPERA radar composite

LHN for COSMO-EU:Summary



nudging of radar radial velocity:verification against radar precipitation

1 – 27 May 2012

precipitation against radar

FSS , 11 g.pts. (30 km)

threshold : 2 mm / h

control (COSMO-DE setup, with LHN)

use of radial velocity added

assimilation

00-UTC forecast runs 12-UTC forecast runs


nudging of radar radial velocity:example

radial velocity at lowest elevation (0.5°) of radar site Feldberg (30 Jan. 2012, 21 UTC).

observation

Azimuth

Ran

ge

(in m

)

model (COSMO-DE)

observation increment

Azimuth

Ran

ge

(in m

)

southwesterly wind above 2500 m a.s.l.

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Recent developments at DWD

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