1. THE PUZZLING DIFFERENCE BETWEEN RADAR OBSERVATIONS OF STRATOCUMULUS AND AIRBORNE IN SITU DATA H. Russchenberg, O. Krasnov, S. Crewell, U. Loehnert, M. Quante, J. Meywerk, H. Klein Baltink Delft University of Technology – IRCTR, The Netherlands, Bonn University, Germany, Institute for Coastal Research GKSS, Germany, Royal Netherlands Meteorological Institute KNMI, The Netherlands University of Munich, Germany

2. Zsimulated > Zobserved observationsimulation Aircraft fssp observations

3. Zsimulated > Zobserved Balloon-borne fssp observations

4. Radiometer-constraint methods LWP from radiometer constrain the range of A and B Examples: Frisch (sets B = 2) Integrated profile technique (Loehnert, Crewell): includes cloud model

5. Frisch’s fittings Case study: September 23, 2001, Cabauw, NL, 8.00-10.00 The results of Frisch’s algorithm application Log-Normal DSD N=1000 - 2000 cm -3,  = 0.8 N=1000 - 2000 cm -3,  = 0.1

6. BBC2, 05.09.2001, 9:42-10:42 MICCY, GKSS 95 GHz radar, Frisch method

7. BBC1 : IPT Z-LWC

8. 1. The radars are not well calibrated. 2. The radar and aircraft are not collocated 3. Low-level boundary clouds are in the near-field of the antenna. 4. The variability of internal and external cloud strucutre is too large 5. The internal cloud dynamics is too small to cause incoherent scatter, and the radar reflectivity is partly caused by coherent scattering. Hypotheses

9. 1. System check 2. Radar intercomparison 3. Data analysis: comparison of aircraft data, radar data and in situ balloon data will be carefully analyzed with respect to the meteorological circumstances and the radar discrepancy 4. The radar discrepancy will be assessed as function of cloud base height. 5. The radar observations will be compared with high temporal resolution lidar data and video data to analyze the temporal variability. 6. A sensitivity study will be performed to assess the potential presence of coherent scatter in the radar signal Research actions

10. Radar intercomparison: 35 and 94 GHz

13. Difference observation-simulation vs cloud base

14. Effect of distance between aircraft and radar. simulationsobservations

15. Different meteorological circumstances Difference observation-simulation for BBC1 campaign (2 months)

16. radar reflectivity factors in high time resolution (0.06 sec)- 5, 30, and 60 second segments.

17. Impact of cloud inhomogeneity LWC height K=lwctop/lwcbase

18. Convergence to incoherency