COSMO General Meeting, Rome, Italy, 5-9 September 2011 Status of the implementation of the tile approach into the COSMO model COLOBOC meeting 5 September 2011 Ekaterina Machulskaya German Weather Service, Offenbach am Main, Germany

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 ns_snow ns_stat User-defined parameters: ns_stat: number of static surface types ns_snow: number of those static surface types which 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 list is 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 ) (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, UTC day, 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, UTC day, UTC

Tiled Surface Scheme within the 3d COSMO model: results

COSMO General Meeting, Rome, Italy, 5-9 September … Experiment is set up, results are monitored Conclusions

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