Netherlands Polar Data Center

Abstract

The performance of a regional atmospheric climate model (RACMO) with a horizontal resolution of 55 km x 55 km is evaluated using measured temperature and humidity profiles. Parameterisations of the physical processes are taken from the ECHAM4 general circulation model (GCM). Sea-surface temperatures and sea-ice mask in the model are prescribed from observations. The model is forced by re-analyses of the European Centre for Medium-range Weather Forecasts (ECMWF) at the lateral boundaries. We compared simulations forJanuary 1993 with boundary-layer profiles measured at the Swedish research station Svea (Dronning Maud Land, Antarctica) and with radiosonde measurements made at the Georg von Neumayer (GvN) and South Polar stations for the same period. This comparison was performed in order to study some model characteristics before the model is used for mass-balance calculations. The vertical temperature gradient at Svea during the night is overestimated by RACMO, but corresponds much more closely to the observations than do the ECMWF re-analyses. In the re-analyses a decoupling of the lowest model layer from the higher atmosphere occurs. The differences between the absolute temperatures at the GvN and SP stations and the absolute temperatures at the model gridpoints corresponding most closely to these sites are less than 5°C. The humidity profiles indicate that the model generally underestimates the turbulent transport of moisture from the surface to higher levels.

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