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CARPE DIEM WP 7: FMI Progress Report. Jarmo Koistinen, Heikki Pohjola Finnish Meteorological Institute. Area 1/WP3: Development of a variational assimilation scheme for doppler winds (FMI + SMHI, responsible persons at FMI Heikki Järvinen, Kirsti Salonen)
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CARPE DIEMWP 7: FMI Progress Report Jarmo Koistinen, Heikki Pohjola Finnish Meteorological Institute
Area 1/WP3: Development of a variational assimilation scheme for doppler winds (FMI +SMHI, responsible persons at FMI Heikki Järvinen, Kirsti Salonen) • Area 2/WP7: Advanced surface precipitation estimate from radars and a NWP model (HIRLAM) (Jarmo Koistinen, Heikki Pohjola) • Objective: Improve the accuracy and quality of operational real time precipitation measurements
WP 7.3 Vertical reflectivity profile correction applying radars and NWP • New order: 7.3 started first and continues during the whole 36 months. WPs 7.1-7.2 started later and feed 7.3. • Operational method has been created and validated (preliminary presentations at ERAD and AMS Radar Conferences, Heikki’s MSc), a final paper should be written. Remaining problem: OP i.e. WP 7.2. • Results applied in the GPM-project validation planning
Measured vertical profile of reflectivity • 7 C-band radars • every 15 minutes • layer thickness 200 m • range 2 - 40 km • max bin count 5000 / layer 1(2)
Statistics of VPR from March 2001 to August 2003 (556 471 profiles) 1(2)
Climatological profiles based on precipitation profiles March 2001 to August 2003
VPR correction 1(2)
Validation of the VPR correction with overlapping radars • Precipitation profile measured at Radar 2 • > 50 measurement bins in the same location diagnosed as precipitation (max. 10020) • Difference in those bins (Rad 2 – Rad 1) tells under/over estimation at the distance Rad 2 • Average bias and standard deviation calculated for distances 141 km, 180 km, 193 km, 198 km and 219 km. Measurement area 5 – 15 km 1(2)
Radar pair Anjalankoski-Vantaa (Vantaa-Anjalankoski) Feb – May 2003, distance 141 km
Radar pair Korppoo-Vantaa (Vantaa-Korppoo) Feb – May 2003, distance 180 km
Radar pair Ikaalinen-Vantaa (Vantaa-Ikaalinen) Feb – May 2003, distance 193 km
Radar pair Ikaalinen-Korppoo (Korppoo-Ikaalinen) Feb – May 2003, distance 198 km
Radar pair Kuopio-Utajärvi (Utajärvi-Kuopio) Feb – May 2003, distance 219 km
Radar pair Vantaa-Ikaalinen (Ikaalinen-Vantaa) Jun – Aug 2003, distance 193 km • Calibration difference on Vantaa (+ 2-3 dB) and lowest elavation angle 0.8 instead of 0.4 on Ikaalinen because of technical reason (-2 dB)
Correction with different measurement angles Snow profile Rain profile with bright band 2 dB
Nordrad Quality Assurance project • Calibration difference for radar pair Vantaa Ikaalinen, period Jun – Aug 2003
WP 7.1: Attenuation correction based on 3D water phase diagnosis from NWP model quantities • Deliverables: • Large attenuation statistics for rain-only (assumed in most existing radar systems) and variable water phase statistics • Improvement in surface precipitation • Overestimation of attenuation in hail avoided by applying a hail algorithm
Calculation of attenuation • Simple one: all precipitation is liquid, k(dB/km)=1.12*10-4 Ze0.62 • Advanced one: freezing level height fixed at each radar, obtained from NWP and VPR, attenuation calculated separately in each water phase layer • We are testing Doppler data from elevation angle 90 degrees in the polar volume scans to improve the radar-based detection of freezing level • Formula: rain (see above), dry snow (in Battan), bright band ?
WP 7.2 Elimination of overhanging precipitation (OP) from surface estimates Altostratus: present in 15 % of all VPR in Finland in 2001
Diagnosis of OP in the network • Apply precipitation base height field from the radar network • Apply (an idea so far): nowcast movement of theVPR, measured above the radars with the analysed motion vector field (operationally available) • Apply precipitating layers from NWP. First step: compare model profiles from HIRLAM with VPR from radars. Available quantities e.g. RH, and cloud condensate mixing ratio.
Overhanging precipitation 9.3. 2002 at Anjalankoski radar 1(2)
24 h accumulated precipitation Nov 8, 2002, 23 UTC No VPR correction No VPR correction 1(2)
24 h accumulated precipitation Nov 7, 2002, 14 UTC No VPR correction With VPR correction 1(2)