Presentation is loading. Please wait.

Presentation is loading. Please wait.

COSMO General Meeting, Cracow, 15 – 19 Sept. 2008 Overview on Data Assimilation WG1 Overview 1 Developments at DWD

Similar presentations


Presentation on theme: "COSMO General Meeting, Cracow, 15 – 19 Sept. 2008 Overview on Data Assimilation WG1 Overview 1 Developments at DWD"— Presentation transcript:

1 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 1 Developments at DWD Deutscher Wetterdienst, D Offenbach, Germany Klaus Stephan:Latent Heat Nudging Mariella Tomassini:Integrated Water Vapour (IWV) from ground-based GPS Heinz-Werner Bitzer, Alexander Cress: Scatterometer Wind Martin Lange, Werner Wergen:Variational Soil Moisture Analysis (SMA)

2 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 2 DWD: Done: – revised definition of reference precipitation → reduced overestimation of precipitation during LHN – bright band detection inside COSMO model Outlook: – extend use of radar data to foreign radars – revise reference precipitation to account for (min.) radar beam height – better understand how (nature/) model develops convection (role of environment, (moisture) balance, …) Latent Heat Nudging Klaus Stephan (DWD)

3 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 3 Modified definition of the reference precipitation prognostic precipitation: generated precipitation reaches the ground with some delay:  wanted:an immediate information on how much precipitation the temperature increment has initialised already (refer this info to observed precip.) use of a ’reference precipitation’ RR ref : vertically averaged precipitation flux (temporal delay not completely eliminated) P early Z cloud z0z0 RR mo = 0 RR ref > 0 RR z 0 → k = ? old: first layer from above with P ≥ 0.1 mm/h new: first layer from above with P ≥ 0,4 * P max in the column aim: reduction of bias betw. model precip RR mo and reference precip RR ref z 0 new RR ref ≈ RR mo P mature

4 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 4 October 2007 RR mo RR ref negative bias of RR ref removed old new

5 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 5 October 2007 RR mo RR obs positive bias of RR mo reduced reduced overestimation of model precipitation (against radar)

6 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 6 assimilation (August 2007) 0.1 mm/h5.0 mm/h ETS FBI old new old reduced overestimation of strong precipitation, improved scores

7 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 7 free forecasts (00 & 12 UTC; 62 runs (August 2007) 0.1 mm/h5.0 mm/h ETS FBI no significant impact on free forecasts

8 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 8 Bright Band detection (inside COSMO model) Quelle: wikipedia H_zero: height of freezing level in the model H_radar: height of radar beam RR_RAD:hourly sum of precip. observed by radar H_zero H ̇ _radar Bright Band criteria: 1.H_zero – H_radar  [-300;600] RR_RAD(i,j) 2. > 8.5

9 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 9 Synop-Regnie Radar g.pts. with BB (≥1x/day) ASS, LHN, no BB detect. ASS with BB detection ASS without LHN

10 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 10 mean skill scores over 32 forecast (00 and 12 UTC) AUGUST 2006 threshold 0.1 mm/h ETSFBI ASS FORECAST ASS FORECAST LHN and prognostic precipitation shows impact of LHN refinements in 2005 / 06 (reference precip / LHN restricted to ‘cloudy layers’ / grid point search / limits) Stephan, K., S. Klink, C. Schraff, 2008: Assimilation of radar-derived rain rates into the convective-scale model COSMO-DE at DWD. Q. J. R. Meteorol. Soc., 134, 1315 – 1326.

11 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 11 IWV derived from observed TZD (with p, T from Synop or COSMO) Use of Integrated Water Vapour (IWV) from Ground-Based GPS Mariella Tomassini, Klaus Stephan, Christoph Schraff (DWD) (W.P. 1.2) q model q gps IWV gps < IWV mod pseudo-obs profile of specific humidity ‘quality weights’ for ( ~ 1 betw. 700 – 800 hPa) : IWV from 169 Sta. every 15 min. (verify well with RS92-humidity, except for 12-UTC dry bias of RS92 in summer) 1 – 13 June 2007, anticyclonic air-mass convection 21-h forecasts from 0, 6, 12, 18 UTC ass cycle comparison: ‘CNT’: like opr (with RS + LHN) ‘GPS’: CNT + GPS ‘noRSq: CNT – RS-humidity GPS assimilated like radiosonde humidity profiles, but with smaller horizontal influence ( ~120 km → ~ 50 km) Experiment

12 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview UTC Analysis 00 UTC 06 UTC Obs 18 UTC CNT NoRSq GPS daily cycle of: IWV CNT 00 GPS 00 CNT 12 GPS 12 → COSMO-DE too moist → 12-UTC RS dries → GPS dries except at 12-UTC

13 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 13 RS verification : BIAS (model - obs) + 0 h + 6 h CNT GPSNoRSq 00- UTC runs + 0 h + 6 h 12- UTC runs

14 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 14 Synop verification 00 UTC Forecast 06 UTC Forecast 12 UTC Forecast 18 UTC Forecast Correct Cloud Cover Percent : GPS oooo CNT ****

15 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 15 hourly mean of precipitation (forecasts compared to radar) Obs CNT GPS NoRSq 0.1 mm/h 2.0 mm/h 00 UTC runs 12 UTC runs 2.0 mm/h reduction of precip by GPS increase of precip without RS-q

16 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 16 radar verification – ETS 0.1 mm/h 1.0 mm/h 00 UTC runs 12 UTC runs CNT GPS NoRSq great improvement by GPS GPS: worse because too little strong precip in early evening

17 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 17 GPS IWV obs from GFZ have good quality → further comparison / assimilation with GPS data from ~ 1000 European stations (Eumetnet Project E-GVAP) main objects: data selection, extrapolation to 10 m, vertical + horizontal structure functions GPS data have shown 12-UTC dry bias of RS92 (in 2007) → validate new version of RS92 GPS data useful for verification of daily cycle of humidity in the model → test future development in data assimilation / physics with these data GPS IWV assimilation reduces overestimation of precip at night and has significant positive impact in first 8 hours of 0-UTC forecasts, but tends to suppress strong precip in afternoon → test again, when model physics improve daily cycle of precip, and test in winter GPS – IWV : Conclusions & Outlook

18 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview Assimilation of Scatterometer Wind Heinz-Werner Bitzer (MetBw), Alexander Cress, Christoph Schraff (DWD) nudging of scatterometer wind data as buoy observations technically implemented, taking into account all quality control / bias correction steps developed for use in GME idealised case studies: model rejects largest part of 10-m wind info unless mass field is explicitly balanced  derive surface pressure analysis correction in geostrophic balance with 10-m wind analysis increments (implies need to solve Poisson equation): implemented, model now accepts data use of ASCAT in addition to QuickScat implemented

19 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 19 Experiment 28 Feb – 9 March 2008, with QuickScat & ASCAT data with ASCAT / QuickScatno scatt pmsl (model – obs) too low too strong gradient COSMO-EU 9-h forecasts, valid for 6 March 2008, 9 UTC Assimilation of Scatterometer Wind Heinz-Werner Bitzer (MetBW), Alexander Cress, Christoph Schraff (DWD) (W.P. 1.5)

20 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 20 Assimilation of Scatterometer Wind 29 Feb 08, 0 UTC COSMO-EU ana with ASCAT/QuickScatCOSMO-EU ana, no scatt ECMWF analysis 29 Feb 08ASCAT 28 Feb 08, 21 UTC ± 1.5h 984 hPa max. 30 kn ~15 m/s 10-m wind [m/s]

21 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 21 aim:replace additional model runs by parameterized regressions to the determine the gradient of the cost function in the variational scheme (absolutely required for GME (long term dry drift), welcome for COSMO model) Soil Moisture Initialisation Martin Lange, Werner Wergen (DWD) (W.P.1.8.1) Cost function penalizes deviations from observations and initial soil moisture content Analysed soil moisture depends on T 2m forecast error and sensitivity  T 2m /  w current scheme: by additional model runs with slightly different w (k,0:00) new scheme: parameterised as a function of predicted latent heat flux at noon

22 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 22 Deutscher Wetterdienst T 2m (12 & 15 UTC) : good performance in summer, degredation in winter Bias T 2m on LM1 domain, avg 12:00, 15:00 RMSE T 2m on LM1 domain, avg 12:00, 15:00 comparison of parameterised SMA with operational SMA: experiment May – November 2006 no SMA opr. SMA param. SMA no SMA opr. SMA param. SMA

23 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 23 Deutscher Wetterdienst Small change in top layers, higher wetness in bottom layers soil moisture content RMS of SMA increments, at layer 4 (9-27cm) ( SMA incr. at layer 5 = 3 * (SMA incr. at layer 4) ) opr. SMA : top layer param. SMA: top layer opr. SMA : bottom layer param. SMA: bottom layer opr. SMA param. SMA small differences in upper layers (until Nov.) stronger moistening of lower layers (further reduces positive T 2m bias in summer) comparison of parameterised SMA with operational SMA: experiment May – November 2006 parameterised SMA : almost zero increments during winter, starting mid September

24 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 24 total differential: sensitivity of T 2m to w 2 → is different in operational and parameterised SMA in winter parameterised (in winter: near zero due to inactive plants) not parameterised, but how does it look like in the model (i.e. in the operational SMA)

25 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 25 8 cm 15 cm 60 cm 90 cm soil water content: Lindenberg observations 15 cm: reacts after 6 hours 5 – 7 Nov 2006 (2 days)15 Oct 2006 – 1 Jan 2007 (2.5 months) 30 cm: reacts after 4 days 45 cm: reacts after 2 weeks → expect model layer 27 – 81 cm to take about 1 week to react → expect model layer 9 – 27 cm to take few hours at most to react

26 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 26 soil water content: model at Lindenberg model layer 27 – 81 cm expected to take about 1 week to react → ok model layer 9 – 27 cm expected to take few hours at most to react → ok → gravitational drainage (sedimentation) appears roughly realistic in COSMO → soil moisture increments of operational SMA appear reasonable

27 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 27 → parameterised SMA for COSMO: operational in 2009 (spring (?): simple version, autumn: with gravitational drainage) Outlook → parameterise also can be derived analytically from Richards eq. used in COSMO (TERRA) parameterisation already exists in current version of param. SMA → parameterised SMA for GME: full experiment started, operational in spring 2009 → include RH 2m as additional obs (param. implemented, increments reasonable in first case) possible further extensions: Analyse the top 5 soil layers separately instead of 2 aggregated layers (DWD). Inclusion of precipitation analysis when good product is available (Suisse). Improvement of model error statistics (Italy). Note: SMA parameterisation needs some maintenance to account for future changes in the parameterisation of surface fluxes e.g. modification of root water uptake → cheap, efficient

28 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 28 analysisoperationalnew T2m diagnostics Deutscher Wetterdienst COSMO-EU : hours New T 2m diagnostics affects the whole PBL through SMA Bias T2m, C-EU on LM1-domain, avg12:00, 15:00Accumulated soil moisture increments Rmse T2m, C-EU on LM1-domain, avg12:00, 15:00 10 m 2250 m Dew point temperature Germany both runs done with operational version of SMA

29 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 29 Thank you for your attention

30 COSMO General Meeting, Cracow, 15 – 19 Sept Overview on Data Assimilation WG1 Overview 30 Advantages of NetCDF: widely used and portable a variety of software exists to plot, analyse and evaluate the data. DWD plans: envisaged set-up observation formats, pre- and post-processing can keep AOF as alternative data input as long as needed DWD switches to NetCDF on 17 Sept thereafter, DWD will no longer support AOF interface ~ 1 by 1 converter simple + portable applicable to WMO or non-WMO BUFR standard WMO templates, i.e. unique descriptors + dimensions of elements + code tables unique BUFR format for each obs type NetCDF 2 ODB monitoring NetCDF obs 3DVar NetCDF feedbac k COSMO model verification NWP section any kind of BUFR bufr 2 wmo_buf r WMO BUF R bufr2netcdf IT section SKY / archive Under discussion at DWD


Download ppt "COSMO General Meeting, Cracow, 15 – 19 Sept. 2008 Overview on Data Assimilation WG1 Overview 1 Developments at DWD"

Similar presentations


Ads by Google