cosmo general meeting, rome, italy, 5-9 september 2011 status of the implementation of the tile...

COSMO General Meeting, Rome, Italy, 5-9 September 2011

Status of the implementation of the tile approach

into the COSMO model

COLOBOC meeting5 September 2011

Ekaterina Machulskaya

German Weather Service, Offenbach am Main, Germany

(ekaterina.machulskaya@dwd.de)

COSMO General Meeting, Rome, Italy, 5-9 September 2011

Tile and mosaic approaches (recall)

Tiled surface scheme within full-fledged COSMO model: implementation, set up of experiments

Some results

Conclusions and outlook

Outline

Tile and mosaic approaches

from (Ament, …)

Tiled Surface Scheme within the 3d COSMO model

Mosaic approach implemented by Felix Ament into the COSMO version 4.7 →

either mosaic or tile approach in the version 4.16, with a user-specified number of tiles or sub-grid mosaic pixels

surface type 1

surface type 2

surface type 3

surface type 4

snow-free

snow-free

snow snow

ns_snow

ns_stat

User-defined parameters:

ns_stat: number of static surface types

ns_snow:number of those static surface typeswhich can have snow as a separate tile

→ derived parameter nsubs(total number of tiles/pixels):nsubs = (ns_stat - ns_snow) · 1 + ns_snow · 2

Tiled Surface Scheme within the 3d COSMO model

Examples of set up:

Mosaic: without snow tiles with snow tiles

Without sub-grid refinement: ns_stat = 0, ns_snow = 0

ns_stat = N, ns_snow = 0

ns_stat = N, ns_snow = N

Tiles: only two tiles “snow/no snow” general case

ns_stat = 1, ns_snow = 1

ns_stat = N, ns_snow = M ≤ N

Tiled Surface Scheme within the 3d COSMO model

Details of the realization of the tiles structure should be encapsulated!

TYPE tile {

LOGICAL :: snow_tile ! is it a snow tile?LOGICAL :: snowfree_tile ! is it a snow-free tile (a counterpart to a snow tile)?INTEGER :: conjunct ! = index of the counterpart (if it is a snow or snow-

free tile)}

TYPE (tile), ALLOCATABLE :: ctile(:) ! vector of nsubs tiles

Example of the code:

IF(ctile(n)% snow_tile) THEN …

ELSEIF(ctile(n)% snowfree_tile) THEN …

ELSE …

END IF

Extension of the attribute listis possible and easy

Tiled Surface Scheme within the 3d COSMO model

• Number of tiles should not be large (computational efficiency!) Surface types with the largest difference of thermal inertia should be chosen,

now: lake/land

• Grid-scale lakes (lake fraction > 0.5) are already treated within the COSMO with FLake model;

there are, however, numerous subgrid-scale water bodies (lake fraction < 0.5) which are ignored:

lake fraction

Tiled Surface Scheme within the 3d COSMO model: set up

Parallel experiment 8330 is set up (COSMO-EU domain, V4_16, running since 01.04.2011)

(The information about lake fraction is available within the COSMO model – no additional software to generate external parameters is needed, thanks to Uli Schaettler for this idea!)

For sub-grid lakes (lake fraction < 0.5)

• lake depth is set to 10 m• on the zero time step, the cold start is performed: lake surface temperature = MAX( land surface temperature, freezing

point ) lake bottom temperature = +4°C (temperature of maximal water density) mixing depth = 8 m ice depth = 0 m shape factor C_T = 0.5 (default)

with 2 tiles: lake/land (ns_stat = 2, ns_snow = 0)

Tiled Surface Scheme within the 3d COSMO model: results

Difference in surface temperature between lake tile and land tile

night, 30.04.2011 00 UTC

day, 30.04.2011 12 UTC

Tiled Surface Scheme within the 3d COSMO model: results

Difference in surface temperature between experiment with tile approach (mean over two tiles) and control experiment

night, 30.04.2011 00 UTC

day, 30.04.2011 12 UTC

Tiled Surface Scheme within the 3d COSMO model: results

Tiled Surface Scheme within the 3d COSMO model: results

COSMO General Meeting, Rome, Italy, 5-9 September 2011.

…

Experiment is set up, results are monitored

Conclusions

COSMO General Meeting, Rome, Italy, 5-9 September 2011.

Thanks to Jochen Förstner, Thomas Hanisch, Jürgen Helmert, Dmitrii Mironov and Bodo Ritter!

Thank you for your attention!

Tiled Surface Scheme within the 3d COSMO model: results

Routine COSMO-EU and COSMO-DE

April 2011 May 2011