Federal Department of Home Affairs FDHA Federal Office of Meteorology and Climatology MeteoSwiss Sensitivity studies for the Swiss test cases LM User Seminar, 8 March 2007, Langen S. Dierer MeteoSwiss

2 Swiss cases S. Dierer Selection of test cases Based on operational forecasts for Switzerland 2005 Selection of 24h area mean of precipitation less than 50% or more than 200% of the measured area mean precipitation (ANETZ verification) about 52 days, more or less the same number per season Excluding days with very light or localized precipitation resulting in 21 days (7 winter, 4 spring, 6 summer and 4 autumn) Selection based on weather situation and kind of error, excluding cases with the „same error“ on different days List of 8 days Simulation with the reference version change of model version (LM 3.19) change of boundary values (IFS/GME) 4 cases change significantly, 4 remain similar Final list: 2.2.; 22.3.; 12.7.;

3 Swiss cases S. Dierer Description of test case Northerly flow at 500 hPa occluded front in the northern part Mainly stratiform Overestimation of mean and maximum precipitation Overestimation at northern slopes of the mountains Typical for situations with northerly flow

4 Swiss cases S. Dierer 24h area mean precipitation for micro1 12 micro2 13 micro3 14 conmod 15 conkfb 16 conoff 17 rlam01 18 rlam50 19 sto sto sea01 22 sea40 O ctrl 1 wso80 2 Wso120 3 Qv090 4 Qv110 5 dt20 6 lfsl3 7 Rksl3 8 rkbott 9 rktp 10 oro

5 Swiss cases S. Dierer 24h maximum precipitation for micro1 12 micro2 13 micro3 14 conmod 15 conkfb 16 conoff 17 rlam01 18 rlam50 19 sto sto sea01 22 sea40 O ctrl 1 wso80 2 Wso120 3 Qv090 4 Qv110 5 dt20 6 lfsl3 7 Rksl3 8 rkbott 9 rktp 10 oro

6 Swiss cases S. Dierer Description of test case southwesterly flow at 500 hPa warm front in the northern part Stratiform Overestimation of mean precipitation (region too large) Overestimation in the eastern part of CH

7 Swiss cases S. Dierer 24h area mean precipitation for micro1 12 micro2 13 micro3 14 conmod 15 conkfb 16 conoff 17 rlam01 18 rlam50 19 sto sto sea01 22 sea40 O ctrl 1 wso80 2 Wso120 3 Qv090 4 Qv110 5 dt20 6 lfsl3 7 Rksl3 8 rkbott 9 rktp 10 oro

8 Swiss cases S. Dierer 24h maximum precipitation for micro1 12 micro2 13 micro3 14 conmod 15 conkfb 16 conoff 17 rlam01 18 rlam50 19 sto sto sea01 22 sea40 O ctrl 1 wso80 2 Wso120 3 Qv090 4 Qv110 5 dt20 6 lfsl3 7 Rksl3 8 rkbott 9 rktp 10 oro

9 Swiss cases S. Dierer Description of test case Northeasterly flow at 500 hPa convective Error in mean and maximum precipitation, maximum too low Observed: strong thunderstorms in the southern part of CH, simulated less intense convective precipitation in the eastern part of CH

10 Swiss cases S. Dierer 24h mean precipitation for micro1 12 micro2 13 micro3 14 conmod 15 conkfb 16 conoff 17 rlam01 18 rlam50 19 sto sto sea01 22 sea40 O ctrl 1 wso80 2 Wso120 3 Qv090 4 Qv110 5 dt20 6 lfsl3 7 Rksl3 8 rkbott 9 rktp 10 oro

11 Swiss cases S. Dierer 24h maximum precipitation for micro1 12 micro2 13 micro3 14 conmod 15 conkfb 16 conoff 17 rlam01 18 rlam50 19 sto sto sea01 22 sea40 O ctrl 1 wso80 2 Wso120 3 Qv090 4 Qv110 5 dt20 6 lfsl3 7 Rksl3 8 rkbott 9 rktp 10 oro

12 Swiss cases S. Dierer Description of test case Northwesterly flow at 500 hPa Mainly stratiform with convective part Overestimation of mean and maximum precipitation Overestimation at the northern slopes of the mountains Typical for situations with northwesterly flow Similar to

13 Swiss cases S. Dierer 24h area mean precipitation for micro1 12 micro2 13 micro3 14 conmod 15 conkfb 16 conoff 17 rlam01 18 rlam50 19 sto sto sea01 22 sea40 O ctrl 1 wso80 2 Wso120 3 Qv090 4 Qv110 5 dt20 6 lfsl3 7 Rksl3 8 rkbott 9 rktp 10 oro

14 Swiss cases S. Dierer 24h maximum precipitation for micro1 12 micro2 13 micro3 14 conmod 15 conkfb 16 conoff 17 rlam01 18 rlam50 19 sto sto sea01 22 sea40 O ctrl 1 wso80 2 Wso120 3 Qv090 4 Qv110 5 dt20 6 lfsl3 7 Rksl3 8 rkbott 9 rktp 10 oro

15 Swiss cases S. Dierer CTRL versus QV90 (Exp. 3),

16 Swiss cases S. Dierer CTRL versus QV90 (Exp. 3),

17 Swiss cases S. Dierer CTRL versus QV90 (Exp. 3),

18 Swiss cases S. Dierer CTRL versus RKsl3 (Exp. 7),

19 Swiss cases S. Dierer CTRL versus RKsl3 (Exp. 7),

20 Swiss cases S. Dierer Summary 1 Stratiform and mainly stratiform cases Reduction of initial humidity causes strong reduction of precipitation except for the case of : about 13%, homogeneous : about 33%, homogeneous (most important) Change from Leapfrog to Runge-Kutta most important change for and (about 20% reduction), small reduction (about 8%) for Reduction seems to act quite homogeneous Micro2 reduces mean precipitation in case (about 20%), micro3 no effect for Changes of and not as similar as expected : QV90 and RKs : RKs, micro2, KFB and conoff

21 Swiss cases S. Dierer Summary 2 Convective case Reduction of initial humidity causes strong reduction of precipitation : about 45%, also changing structure (most important) Change from Leapfrog to Runge-Kutta has no effect for Micro2 reduces mean precipitation in case (about 20%), micro3 similar effect

22 Swiss cases S. Dierer Summary 3 Smaller effects Reduced time step causes smaller effects (5-10% - 3 reductions, 1 increase) Reduced vertical exchange reduces precipitation amount by about 5-10% In two of the cases Runge-Kutta with semi-Lagrange tricubic advection gives unrealistic high maximum values Next steps: ANETZ verification for cases with changes Check against radio soundings if humidity is O.K. understand changes (e.g. reduction of mean precipitation due to Runge-Kutta or decreased vertical exchange and changes due to decreased time step)

23 Swiss cases S. Dierer CTRL versus RKbott (Exp. 8),

24 Swiss cases S. Dierer CTRL versus RKtp (Exp. 9),

25 Swiss cases S. Dierer CTRL versus micro2 (Exp. 12),

26 Swiss cases S. Dierer CTRL versus RLAM50 (Exp. 18),

27 Swiss cases S. Dierer CTRL versus DT20 (Exp. 5),

28 Swiss cases S. Dierer CTRL versus RLAM50 (Exp. 18),

29 Swiss cases S. Dierer CTRL versus RKtp (Exp. 9),

30 Swiss cases S. Dierer CTRL versus micro1 (Exp. 11),

31 Swiss cases S. Dierer CTRL versus micro2 (Exp. 12),

32 Swiss cases S. Dierer CTRL versus micro3 (Exp. 13),

33 Swiss cases S. Dierer CTRL versus conmod (Exp. 14),

34 Swiss cases S. Dierer CTRL versus KFB (Exp. 15),

35 Swiss cases S. Dierer CTRL versus RKbott (Exp. 8),

36 Swiss cases S. Dierer CTRL versus RKtp (Exp. 9),

37 Swiss cases S. Dierer CTRL versus micro2 (Exp. 12),

38 Swiss cases S. Dierer CTRL versus KFB (Exp. 15),