slide1
Download
Skip this Video
Download Presentation
COSMO_2005

Loading in 2 Seconds...

play fullscreen
1 / 5

COSMO_2005 - PowerPoint PPT Presentation


  • 88 Views
  • Uploaded on

COSMO General Meeting Zürich, 20 - 23 September 2005. Report on Workpackage 3.5.1. Validation of boundary layer clouds Test results with the minimum vertical diffusion coefficient set to zero. Erdmann Heise German Weather Service. COSMO_2005. Page 1 (5). DWD 15 Sep 2005.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' COSMO_2005 ' - dillon-arnold


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

COSMO General Meeting

Zürich, 20 - 23 September 2005

Report on Workpackage 3.5.1

Validation of boundary layer clouds

Test results with the minimum vertical

diffusion coefficient set to zero

Erdmann Heise

German Weather Service

COSMO_2005

Page 1 (5)

DWD 15 Sep 2005

slide2

Workpackage 3.5.1

Validation of boundary layer clouds

  • There is a long lasting problem of LM to rapidly dissolve low level
  • stratus or stratocumulus in late autumn and in winter.
  • According to earlier experiments by Dmitrii Mironov the problem
  • might be fixed by setting back the minimum value of the vertical diffusion
  • coefficient to zero.
  • This coefficient was introduced some years ago to avoid long lasting
  • overcast situations over water areas. Following a reduction of evaporation
  • over water in April 2004 this minimum vertical diffusion might turn up
  • to be unnecessary.
  • The effect of a zero minimum vertical diffusion was tested in a parallel
  • experiment for the period 1 October 2004 to 31 December 2004.

COSMO_2005

Page 2 (5)

DWD 15 Sep 2005

slide3

Workpackage 3.5.1

Validation of boundary layer clouds

The case of 11 Novem-

berg led to vehement

complains of the fore-

casters. Whereas Ger-

many was mainly

covered by low clouds,

the operational LM-

forecast showed a

mainly cloudless sky

(left hand part). With

the minimum vertical

diffusion coefficient

set to zero the forecast

was improved consid-

erably (right hand part).

COSMO_2005

Page 3 (5)

DWD 15 Sep 2005

slide4

Workpackage 3.5.1

Validation of boundary layer clouds

The verification results are shown

for December 2004 in the opposite

Table as an example. There are large

improvements in cloud cover

prediction, negligible changes for

2m temperature and dew point,

but drastic degradations in

precipitation and gusts. The results

for November look similar. In

October the frequency of overcast

situations is overpredicted in the

experiment, but temperature and

dew point predictions improve a

little and there is no drastic degra-

dation for precipitation and gusts.

COSMO_2005

Page 4 (5)

DWD 15 Sep 2005

slide5

Workpackage 3.5.1

Validation of boundary layer clouds

On average the results of the objective verification are disappointing,

but they still wait for a thorough evaluation. The reason for the degradation

of precipitation prediction and of the gust diagnosis is not yet understood.

There are connections to WP 3.10.1 (cure overestimation of low precipi-

tation in winter) and to WP 3.5.2 (testing sub-grid scale cloudiness

approaches). Connections are also obvious to the two proposed projects

‘Tackle deficiencies in precipitation forecasts’ and ‘Generalised moist

PBL scheme’.

An Interim Report on the results is available.

COSMO_2005

Page 5 (5)

DWD 15 Sep 2005

ad