A model to observation approach to evaluating cloud microphysical parameterisations using polarimetric radar

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1 A model to observation approach to evaluating cloud microphysical parameterisations using polarimetric radar Monika Pfeifer G. Craig, M. Hagen, C. Keil

2 Polarisation Doppler Radar POLDIRAD Rain Graupel Hail 2

3 Synthetic Polarimetric Radar: SynPolRad? Reflectivity, LDR, ZDR Polar Coordinates Specific water content of hydrometeors Model Grid 3

4 Synthetic Polarimetric Radar: SynPolRad? Reflectivity, LDR, ZDR Polar Coordinates Specific water content of hydrometeors Model Grid Polarimetric Radar Forward Operator: SynPolRad Reflectivity, LDR, ZDR, Model Grid Synthetic Reflectivity, LDR, ZDR, Model Grid 4

5 Link Mesoscale Model - SynPolRad Output parameters of the mesoscale model Bulk water quantities of cloud ice and water, rain, snow and graupel Assumptions of the NWP model (density, For everyhydrometeor type type) Assumed Free Sensitivity Studies DSD Parameters Tuning of the free parameters against the hydrometeor DSD classification Waterportion in Falling behaviour scheme (Höller Density 1994) Shape (Do, No) melting ice (canting angle) Input parameters of SynPolRad Reflectivity Dielectric Constant LDR, ZDR 5

6 Case Study : 5th of July 2005 Comparison of 6 LMK runs: (dx = 2.8 km) 2 different versions, and 3 different microphysical paramet. Schemes: 2 component scheme (rain, snow) 3 component scheme (rain, snow, graupel) Thompson (rain, snow, graupel) 6

7 8 UTC 2 PPI Observations LMK 2 comp. LMK: 3 comp. LMK: Thompson Scheme 7

8 8 UTC: 2 PPI Scan - Mean over azimuth angles Poldirad Thompson Thompson-N LMK, 3 comp LMK-N, 3 comp LMK, 2 comp LMK-N, 2 comp Poldirad Thompson Thompson-N LMK, 3 comp LMK-N, 3 comp LMK, 2 comp LMK-N, 2 comp Reflectivity [dbz] ZDR [db] 8

9 6 UTC : 2 PPI Scan - Mean over azimuth angles For all schemes: Poldirad Thompson Thompson-N LMK, 3 comp LMK-N, 3 comp LMK, 2 comp LMK-N, 2 comp ZDR is too small for the simulated reflectivity. Poldirad Thompson Thompson-N LMK, 3 comp LMK-N, 3 comp LMK, 2 comp LMK-N, 2 comp The slope of the DSD is too steep; there are not enough large drops present. Reflectivity ZDR 9

10 1 PPI 10 UTC Observations LMK:2-comp. LMK 3 comp. LMK: Thompson 10

11 0.157 omparison: 3-comp. - Thompson scheme Mixing Ratio [g/kg]:

12 Case Study: 12th August 2004, 15 to 20 UTC LMK 3.16: 2 component 3 component Thompson MesoNH 12

13 MK 3.17: 9:00 UTC Observation MesoNH LMK, 2 comp. LMK, 3 comp. LMK, Thompson 13

14 RHI Reflectivity Observation 19:23 UTC MesoNH LMK: 2 comp. LMK:3 comp. LMK:Thompson 14

15 Hydrometeor Classification Observation 19:23 UTC LMK :2 comp. LMK :3 comp. LMK: Thompson MesoNH LMK 19 UTC 3 comp. 15

16 Conclusion and Outlook Polarimetric Radar together with the polarimetric radar forward operator SynPolRad provide a novel tool to validate cloud microphysics. Stratiform case study: The DSD of rain is not represented well in the sense that large drops are underestimated. Differences between the Thompson and LMK schemes in rain can be traced back to the cloud ice. Convective case study: The number of ice hydrometeors and the assumptions regarding density and DSD are essential for the representation of convective events. Outlook: Long term evaluation within the project QUEST (Poster by Crewell et al.) Expansion of SynPolRad to cloud radar Model intercomparison including LMK, MM5, MesoNH,??? 16

17 8 UTC: 2 PPI Scan - Mean over azimuth angles Poldirad Thompson Thompson-N LMK, 3 comp LMK-N, 3 comp LMK, 2 comp LMK-N, 2 comp Poldirad Thompson Thompson-N LMK, 3 comp LMK-N, 3 comp LMK, 2 comp LMK-N, 2 comp Reflectivity [dbz] LDR [db] ZDR [db] 17

18 Beam Propagation 18

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