MM5 sensitivity to boundary conditions and domain configuration for climate studies over Southern Spain

An analysis of MM5 response to varying boundary conditions and domain configurations is presented in order to determine their influence on results in terms of temperature and precipitation in the South of Spain. Three different driving datasets have been used - ERA40 Reanalysis from ECMWF, NNRP from NCEP/NCAR and ECHAM5 from Max Planck Institute for Meteorology - with a frequency of 6 hours for all of them. Impacts of domain configuration, size and number of domains, on the model performance have been studied. Every simulation has been designed containing two domains with a resolution of 10 km and 30 km that slightly varied in their size and location. The target 10km-resolution domain covers a region of approximately 800 km by 600 km. The 30km-resolution domain comprises the whole of the Iberian Peninsula. A third parent 90km-resolution domain is included in some of the integrations, covering most of Europe and a big portion of the Northern Atlantic Ocean.

Several simulations have been performed using various physics options for PBL and microphysics. Cumulus (Grell), radiation (RRTM) and soil model (Noah-LSM) selections are based on previous examinations of their performance over the region. Because of the fact that the examination is focused on climate studies, a 10 year period is selected for every run (1990-1999).

Monthly mean of temperature and monthly accumulated precipitation computed from MM5 runs have been compared with CRU TS1.2 dataset and observational data. Station data is considered as a background truth to compare with, whereas CRU TS1.2 permits a direct comparison grid to grid that minimize local differences that are introduced when directly comparing with observational data.

Noticeable differences have been found for both the boundary conditions and the domain disposition selected, particularly for precipitation. This analysis permits to determine an appropriate choice of these parameters and therefore, optimise the MM5 configuration in these terms for the climate studies over Southern Spain.