1 / 17

Assimilation of Radar Information in the Alpine Model of MeteoSwiss

Assimilation of Radar Information in the Alpine Model of MeteoSwiss. Daniel Leuenberger and Andrea Rossa MeteoS wiss. Introduction. Radar information is gaining importance in mesoscale data assimilation Latent Heat Nudging (LHN): Assimilation method for precipitation information

jaser
Download Presentation

Assimilation of Radar Information in the Alpine Model of MeteoSwiss

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Assimilation of Radar Information in the Alpine Model of MeteoSwiss Daniel Leuenberger and Andrea Rossa MeteoSwiss

  2. Introduction • Radar information is gaining importance in mesoscale data assimilation • Latent Heat Nudging (LHN): Assimilation method for precipitation information • Trigger model precipitation where radar detects precipitation (heating), supress it elsewhere (cooling) • 4DDA, yet computationally very efficient • Conceptionally simple • Assimilation of non-prognostic variables not straight forward • Heuristic approach of weighting observations and model Daniel.Leuenberger@MeteoSwiss.ch SRNWP – COST-717 Lisbon, 8.October 2003

  3. Radar Quality Map Radar Observations • Swiss radar network: 3 C-Band Doppler Radars • Best estimate of surface rain: preprocessed (e.g. clutter reduction, vertical profile corrections) • Resolution: 2 x 2 km2, 5 min Daniel.Leuenberger@MeteoSwiss.ch SRNWP – COST-717 Lisbon, 8.October 2003

  4. Real Case Study • Case • System of severe convection over Switzerland • Triggered around 22h30 UTC over the Massif Central • Development ahead of weak cold front • Moderately unstable environment as observed by the Swiss radiosonde Payerne at 00UTC (CAPE ~250 J/kg) • Strong wind shear (~ 30 m/s at 6000m) • Simulations • Operational Alpine Model (aLMo) of MeteoSwiss (Dx=7km) • Convection Parametrization • Started 21.8.00 00 UTC from GME of DWD • CTRL (no forcing) • LHN during 6h • LHN+ during 3h, free forecast afterwards Daniel.Leuenberger@MeteoSwiss.ch SRNWP – COST-717 Lisbon, 8.October 2003

  5. Hourly Sums of Precipitation: Forcing during 6h CTRL LHN Radar 02 01 03 04 05 06 Case Study of the 21.8.2000 Storm Daniel.Leuenberger@MeteoSwiss.ch SRNWP – COST-717 Lisbon, 8.October 2003

  6. Hourly Sums of Precipitation: Forcing during 3h CTRL LHN+ Radar 02 01 03 04 05 06 1h Free Forecast 2h Free Forecast 3h Free Forecast Case Study of the 21.8.2000 Storm Daniel.Leuenberger@MeteoSwiss.ch SRNWP – COST-717 Lisbon, 8.October 2003

  7. Findings I • Model is able to assimilate radar observations • Good impact in analysis, sfc winds in line with observations • Some impact in free forecast up to 03h • Model loses information quickly, i.e. storm dies too early • Why is the model not able to maintain storm? • Environment not representative? • Model resolution ? • Try to find reasons by means of idealized simulations Daniel.Leuenberger@MeteoSwiss.ch SRNWP – COST-717 Lisbon, 8.October 2003

  8. KW profile KW sounding Payerne sounding Payerne profile wind shear Idealized Simulations • Setup • Environment from Payerne sounding of 21.8.00 00UTC • Fine mesh (Dx = 1km), no CPS, no soil model, no radiation • Trigger convection with warm bubble: No storm development • Klemp Wilhelmson Environment • Large amount of CAPE (~ 1200 J/kg) • Moderate wind shear • Favorable for splitting supercell storms Daniel.Leuenberger@MeteoSwiss.ch SRNWP – COST-717 Lisbon, 8.October 2003

  9. OSSE Setup • Reference run • Convection initiated with warm bubble • Model sfc rain serves as „artificial radar observations“ • LHN Analysis • Same environment as reference run • No warm bubble initiation • LHN during 3h (artificial rain rates from reference run) • LHN Forecast • LHN during first 30, 60 min • Free run afterwards Daniel.Leuenberger@MeteoSwiss.ch SRNWP – COST-717 Lisbon, 8.October 2003

  10. Dt = 10min linear interpolation Dt = 1min Insertion Frequency of Precipitation Input • LHN linearly interpolates between subsequent observations • Examine relevance of insertion frequency Dt to LHN Analysis Daniel.Leuenberger@MeteoSwiss.ch SRNWP – COST-717 Lisbon, 8.October 2003

  11. Dt= 10min “OBS“ Dt= 1min Dt= 4min LHN Analysis (LHN during 3h) Daniel.Leuenberger@MeteoSwiss.ch SRNWP – COST-717 Lisbon, 8.October 2003

  12. Domain Sum of LH Nudging Increment Daniel.Leuenberger@MeteoSwiss.ch SRNWP – COST-717 Lisbon, 8.October 2003

  13. LHN Forecast (Dt= 1min) Analysis (LHN during 3h) “OBS“ Daniel.Leuenberger@MeteoSwiss.ch SRNWP – COST-717 Lisbon, 8.October 2003 Free forecast after 30 min Free forecast after 1h

  14. Analysis (LHN during 3h) Free forecast after 1h Dx = 2km Dx = 5km Sensitivity to Horizontal Grid Spacing Daniel.Leuenberger@MeteoSwiss.ch SRNWP – COST-717 Lisbon, 8.October 2003

  15. Findings II • LHN capable of analysing and initiating supercell storm • Good temporal sampling of the observed phenomena is important • Representative large-/mesoscale environment important • Even a poorly resolved forcing is able to initiate and maintain storm evolution in appropriate environment • Supercell storm very stable dynamics: are findings ‚portable‘ to other situations? Daniel.Leuenberger@MeteoSwiss.ch SRNWP – COST-717 Lisbon, 8.October 2003

  16. Outlook • Real-case study • Reduction of grid-size to 2km • Study impact of errors in radar data • More cases • Idealized OSSE • Sensitivity of vertical forcing distribution • Assimilation of model 3D latent heating fields • Assimilation of horizontal winds • Consider case which is less driven by dynamics Daniel.Leuenberger@MeteoSwiss.ch SRNWP – COST-717 Lisbon, 8.October 2003

  17. Thank you for your attention ! Daniel.Leuenberger@MeteoSwiss.ch SRNWP – COST-717 Lisbon, 8.October 2003

More Related