Cloud Profiling at the Lindenberg Observatory

Transcription

1 Cloud Profiling at the Lindenberg Observatory Ulrich Görsdorf DWD,

2 Cloud Profiling with a Ka-Band radar at the Lindenberg Observatory Ulrich Görsdorf DWD,

3 MIRA 35.5 GHz (8 mm) Radar (Ka-Band) Coherent on receive Dual linear polarization TX: Magnetron, PEP 30 kw Cassegrain antenna with polarization filter Vertical range: km Vertical resolution: 30 m Averaging time: 10 s Sensitivity: -54 dbz (1 km, 10s) -45 dbz (10 km, 10s) Doppler moments in two RX channels

4 Calculation of moments for each range gate Signal power P = vh S ( v ) r vl Doppler velocity v vs( v) dv = vh r vl dv v l v h Spectral width σ 1 S vh 2 = ( v ) v vl 2 v S( v) r dv

5 Radar equation Backscattered power: P r σ = C 2 r 5 π η = 4 λ K 2 N i= 1 6 D i C - radar constant σ - radar cross section ( = η V) r - range between radar and target Volume reflectivity for particle scattering (Rayleigh-scattering), d << λ Reflectivity factor: Z = N i= 1 6 D i Lineare Depolarization Ratio (LDR) = λ - wave length K - complex refraction index D - diameter of droplets Unit dbz = 10 log ( Z / [mm 6/ m 3 ] P r of co - polarization channel P r of cross - polarization channel

6 Ci Ci 4h Plots (hourly updated) and 24h-Plots from previous day: Melting layer Insects Cb Special users Research institutes Radar meteorology Results of actual measurements 24h Plots of Cloudnet-products from previous day and archiv: Quicklooks Rain Sc

7 h top T top, p top h base T base, p base Temporal and vertical interpolation of 6-hourly radiosoundings

8 Metop-Validierung Arlindo Arriag und Xavier Calbet (Eumetsat): Comparison of cloud top pressure

9 Radar measurements for reliable cloud top estimation 8 October 2004, 12 UTC RS humidity profile ice saturation Height, m msl Humidity, %

10 Cloud fraction as function of height, April 2004 December Winter Autumn Summer Spring Year 8000 Height, m msl Frequency

11 Microphysical Parameters Liquid water content LWC 4 3 π LWC = r n( r) dr 3 ρ Z LWC relationship Combining Radar, Ceilometer, Radiometer Ice water content IWC Z IWC relationship + temperature Combining Radar - Lidar CLOUDNET (European Project investigating the impact of clouds on NWP, Illingworth et al., 2007) continuous application of algorithm at MOL Integrated Profiling Technique (IPT) Löhnert et al., 2004

12 Cloudnet retrieval algorithm Liquid water content (LWC), Ice water content (IWC) Radar Ceilometer Rain gauge Modell Targetclassification Calculation of adiabatic LWC - profile Calculation of cloud fraction Calculation of IWC -profile Scaling with radiometer-lwp LWC Radiometer MWP cloudfraction IWC

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14 Model evaluation

15 Model evaluation

16 Model evaluation Case study COSMO-EU

17 Summary MIRA36 powerful and reliable system for measurements of cloud parameters Estimation of cloud boundaries by combination with ceilometer measurements Retrieval of microphysical cloud parameters (LWC, IWC) by CLOUDNET -Algorithm and Integrated Profiling Technique Future work: - quality assessment and control (radar calibration) - test of new spectral based data processing techniques

18 Availability 2004: 83 % 2005: 95 % 2006: 98 % 2007: 92 %

19 Summary MIRA36 powerful and reliable system for measurements of cloud parameters Cloud base and cloud top even of optical thick and/or multilayer clouds can be derived (cloud base by combination with ceilometer measurements) Retrieval of microphysical cloud parameters (LWC, IWC) by CLOUDNET -Algorithm and Integrated Profiling Technique Future work: - quality assessment and control (radar calibration) - application and test of new spectral based data processing techniques - cloud statistics

20 Thank you for your attention

21 Überprüfung der Radarkonstanten C durch Vergleich der Reflektivitäten mit denen eines Mikroregenradars Reflektivität (MIRA), dbz y=0.992x für RR >1.0 mm/h RR < 1.0 mm/h RR < 0.7 mm/h RR < 0.4 mm/h RR <0.1 mm/h Reflektivität (MRR), dbz

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23 Ac

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25 Mikrophysikalische Wolkenparameter Liquid water content (LWC), Ice water content (IWC) Cloudnet Radar Ceilometer Modell Regensensor Targetklassifikation IPT Radiosonde Berechnung des LWC Profils (Z LWC) Berechnung des adiabatischen LWCprofils Berechnung des IWC Profils (Z IWC) MWP Optimal Estimation MWP Skalierung mit LWP von MWP LWC LWC LWC

26 Deutscher Wetterdienst

27 Operation principle Wolke halbe Pulslänge Transmitting of em pulses ausgesandter Puls mit Hydrometeoren angefülltes Messvolumen receiving of backscattered signals in the two polarization channels simultanuous processing of both channels and calculation of Dopplerspectrum radiale Distanz rückgestreuter Anteil des ausgesandten Pulses Öffnungswinkel Radar

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29 Adiabatic Adiabatic & scaled IPT

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