1. The COSMO-LEPS cloud problem over the Alpine region
André Walser
MeteoSwiss
COSMO General Meeting, Moscow, 6-10 September 2010

2. Typical summer case…
COSMO-LEPS median
COSMO-7
Observations
 many members with a too small diurnal cycle in 2m temperature
 COSMO-LEPS predicts clearly more clouds than COSMO-7
 large spread in deterministic case

3. SYNOP verif T_2M Europe JJA2010
lead-time +(25-48)h
~1K
Observations
COSMO-LEPS ensemble mean
COSMO-7
00 UTC
00 UTC

4. SYNOP verif T_2M CH JJA2010 ~2K Observations COSMO-LEPS ensemble mean
lead-time +(25-48)h
~2K
Observations
COSMO-LEPS ensemble mean
COSMO-7
00 UTC
00 UTC

5. SYNOP verif CLCT CH JJA2010 20 Mean Error COSMO-LEPS ensemble mean
lead-time +(25-48)h
Mean Error
COSMO-LEPS ensemble mean
COSMO-7
-20
00 UTC
00 UTC

6. SYNOP verif CLCT Europe JJA2010
COSMO-LEPS ensemble mean of CLCT: Mean error

7. June 24 case
COSMO-LEPS median
COSMO-7
Observations

8. June UTC: A sunny day...

9. June 24 15 UTC:COSMO-LEPS Total cloud cover (CLCT)
Low-level cloud cover (CLCL)
member 7
member 7

10. Low level clouds (CLCL)

11. Low level clouds (CLCL)

12. Member configuration itype_conv=1 turlen=150 pat_len=500 crsmin=50
rat_sea=40
rlam_heat=0.1
turlen=500
pat_len=2000
rat_sea=20
rlam_heat=1
turlen=1000
pat_len=5000
rat_sea=1
rlam_heat=5
itype_conv=0
crsmin=150
crsmin=200

13. Member configuration itype_conv=1 turlen=150 pat_len=500 crsmin=50
rat_sea=40
rlam_heat=0.1
turlen=500
pat_len=2000
rat_sea=20
rlam_heat=1
turlen=1000
pat_len=5000
rat_sea=1
rlam_heat=5
itype_conv=0
crsmin=150
crsmin=200

14. COSMO-7 Kain-Fritsch test-suite (1)
Impact on CLCT (4 weeks in summer 2010):
Tiedtke
Kain-Fritsch
~10-15 % higher, but mainly for high cloud cover cases
V.Stauch

15. COSMO-7 Kain-Fritsch test-suite (2)
SYNOP verif T_2M Switzerland (lead-time +(01-24)h):
00 UTC
Observations
Tiedtke
Kain-Fritsch
IFS

16. COSMO-7 Kain-Fritsch test-suite (3)
Overestimation of cloud cover for northern Europe (but not for Switzerland)
Impact on diurnal cycle of 2m temperature for Switzerland very small
 For entire results see talk about comparison of Tiedtke, Kain-Fritsch and IFS convection schemes in WG3
 Results suggest that Kain-Fritsch alone cannot explain the COSMO-LEPS cloud problem

17. June case: Too moist boundary layer
COSMO-LEPS TD_2M and Zurich SYNOP station
[oC]
Kain-Fritsch members
Tiedtke members

18. SYNOP verif TD_2M CH JJA2010 3 Mean Error COSMO-LEPS ensemble mean
COSMO-LEPS ensemble mean
COSMO-7 -3
00 UTC
00 UTC

19. SYNOP verif TD_2M Europe JJA2010
COSMO-LEPS ensemble mean of TD_2M: Mean error

20. Soil moisture: typical summer case
COSMO-LEPS member initial conditions
COSMO-7 initial conditions
[mm]
level 1 (0-1cm)
 wet Alpine region in COSMO-LEPS

21. COSMO-LEPS member initial conditions COSMO-7 initial conditions
Soil moisture: typical summer case
COSMO-LEPS member initial conditions
COSMO-7 initial conditions
[mm]
level 2 (1-3cm)
 wet Alpine region in COSMO-LEPS

22. COSMO-LEPS member initial conditions COSMO-7 initial conditions
Soil moisture: typical summer case
COSMO-LEPS member initial conditions
COSMO-7 initial conditions
[mm]
level 3 (3-9cm)
 wet Alpine region in COSMO-LEPS

23. COSMO-LEPS member initial conditions COSMO-7 initial conditions
Soil moisture: typical summer case
COSMO-LEPS member initial conditions
COSMO-7 initial conditions
[mm]
level 4 (9-27cm)
 wet Alpine region in COSMO-LEPS

24. Conclusions
Cloud problem in COSMO-LEPS seems to be caused by Kain-Fritsch together with a too moist boundary layer
Has dramatic impact on 2m temperature
Too moist boundary layer is caused by a too moist soil
 Soil merge (COSMO-EU or assimilation cycle) should be introduced as soon as possible
If not possible before spring 2011, skip Kain-Fritsch
When problems with IFS convection scheme are solved ( WG3 talk) consider to use it
 Soil moisture should be added to COSMO-LEPS output