Stefan Klink Data Assimilation Section [email protected]
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Transcript of Stefan Klink Data Assimilation Section [email protected]
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08.10.2003 - 1 -Joint SRNWP/COST-717 WG-3 session, Lisbon
Stefan Klink
Data Assimilation Section
Early results with rainfall assimilation at DWD
RADVOR-OP, supported by LAWA
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08.10.2003 - 2 -Joint SRNWP/COST-717 WG-3 session, Lisbon
Early results with rainfall assimilation at DWD
Radar data
Real case study– Humidity adjustment– Filtering of vertical profiles– Influence of convective parameterisation scheme– Influence of mesh size
Summary
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08.10.2003 - 3 -Joint SRNWP/COST-717 WG-3 session, Lisbon
Radar data
Input data currently used
• radar reflectivity at the ground (int. Composite: Germany and surrounding countries)
• pixel size: 4km 4km
• time resolution: 15 minutes (data from volume scan)
• conversion: reflectivity to precipitation rate by simple Z-R-relation
• problems: clutter, only 7 reflectivity classes
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08.10.2003 - 4 -Joint SRNWP/COST-717 WG-3 session, Lisbon
Radar data
„new“ radar data
• input data: reflectivities from precipitation scan, mesh: 1km 1°, time resolution: 5 minutes
• correction of orographic attenuation
• variable Z-R-relation
• compositing
• still incomplete clutter correction
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08.10.2003 - 5 -Joint SRNWP/COST-717 WG-3 session, Lisbon
Real case study: experimental setup
• Convective event on 28. Aug. 2002 over western Germany
• LM runs on the operational domain:– mesh size 7 km
• LM runs on an experimental domain:– covering almost Germany– mesh size 2.8 km
• convective parameterisation scheme switched off
• laterally driven by GME
• 6h Nudging + LHN starting at 6 UTC– adjustment of humidity during LHN
• 6h free forecast starting at 12 UTC
operational domain (7 km)
experimental domain (2.8 km)
evaluation domain
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08.10.2003 - 6 -Joint SRNWP/COST-717 WG-3 session, Lisbon
Real case study: humidity adjustment
• Increased heating increase q to reach f=100% over nudging timescale
• Reduced heating decrease q (maintain f)
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08.10.2003 - 7 -Joint SRNWP/COST-717 WG-3 session, Lisbon
Real case study: humidity adjustment
LM runs on the experimental domain: – mesh size 2.8 km
• without humidity adjustment during LHN
• with humidity adjustment during LHN
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08.10.2003 - 8 -Joint SRNWP/COST-717 WG-3 session, Lisbon
Real case study: humidity adjustment
Hourly sums of modeled and radar-observed precipitation in mm/h
• Nudging 08-09 UTC
• Nudging11-12 UTC
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08.10.2003 - 9 -Joint SRNWP/COST-717 WG-3 session, Lisbon
Real case study: humidity adjustment
• free forecast14-15 UTC
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08.10.2003 - 10 -Joint SRNWP/COST-717 WG-3 session, Lisbon
Real case study: filtering of vertical profiles
vertical cross section W-E, t = 11 UTC, with humidity adjustment specific cloud liquid water content in g/kg
no filtering filtering
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08.10.2003 - 11 -Joint SRNWP/COST-717 WG-3 session, Lisbon
Real case study: influence of convective parameterisation scheme
LM runs on the operational domain: – mesh size 7 km– no adjustment of humidity during LHN
• without convective parameterisation scheme
• with convective parameterisation scheme
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08.10.2003 - 12 -Joint SRNWP/COST-717 WG-3 session, Lisbon
Real case study: influence of convective parameterisation scheme
Hourly sums of modeled and radar-observed precipitation in mm/h
• Nudging 08-09 UTC
• Nudging 09-10 UTC
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08.10.2003 - 13 -Joint SRNWP/COST-717 WG-3 session, Lisbon
Real case study: influence of convective parameterisation scheme
• Nudging
11-12 UTC
• free forecast
12-13 UTC
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08.10.2003 - 14 -Joint SRNWP/COST-717 WG-3 session, Lisbon
Real case study: influence of convective parameterisation scheme
• free forecast
14-15 UTC
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08.10.2003 - 15 -Joint SRNWP/COST-717 WG-3 session, Lisbon
Case Studies: comparison: mesh sizes 7 km and 2.8 km
LM runs:
• CTRL 7 km:– mesh size 7km (operational domain)
• LHN 7 km: – mesh size 7 km (operational domain)
• LHN 2.8 km:– mesh size 2.8 km (smaller model domain)
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08.10.2003 - 16 -Joint SRNWP/COST-717 WG-3 session, Lisbon
Case Studies: comparison: mesh sizes 7 km and 2.8 km
Hourly sums of modeled and radar-observed precipitation in mm/h
• Nudging06- 07 UTC
• Nudging 08-09 UTC
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08.10.2003 - 17 -Joint SRNWP/COST-717 WG-3 session, Lisbon
Case Studies: comparison: mesh sizes 7 km and 2.8 km
• Nudging
11-12 UTC
• free forecast
12-13 UTC
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08.10.2003 - 18 -Joint SRNWP/COST-717 WG-3 session, Lisbon
Case Studies: comparison: mesh sizes 7 km and 2.8 km
• free forecast
14-15 UTC
• free forecast
17-18 UTC
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08.10.2003 - 19 -Joint SRNWP/COST-717 WG-3 session, Lisbon
Summary
• Results:
– adjustment of humidity supports the assimilation of precipitation and leads to more exact free forecasts
– explicit simulation of convection produces more realistic patterns and amounts of precipitation than the corresponding model run with a parameterisation scheme
– model with 2.8 km mesh size shows potential for further improvements of precipitation forecast
– sporadical occurrence of spurious precipitation
– influence of the assimilation lasts for several hours
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08.10.2003 - 20 -Joint SRNWP/COST-717 WG-3 session, Lisbon
Summary
• Future work:
– numerical problems with noisy profiles of latent heat (2 z-structures)
– quality of radar data
– improvements to extend the influence of assimilation during free model run
– prognostic precipitation