Modeling the surface-atmosphere coupling in the Moroccan semi-arid plains in the context of climate change

Morocco as many semi-arid Mediterranean and north African countries is facing strong pressure on water resources exacerbated by climate change. Assessing the representation and variability of the Moroccan climate by using the climate models is of major importance to strengthen the reliability of future scenarios and anticipate the water cycle evolutions.

The aim of this study is to evaluate and improve the representation of the surface-atmosphere coupling, and the boundary-layer dynamics over the Haouz plain by the IPSL-CM Earth System Model. The Haouz plain is one of the most important agricultural and touristic regions of Morocco. It is located in the Tensift watershed and limited with the Atlas mountains, and it has been equipped with a network of meteorological stations. We set a simulation configuration up with a model grid refined over the Haouz plain and with a nudging towards atmospheric reanalysis outside the plain, making it possible to concomitantly compare the model outputs with in-situ data. 

A first evaluation of the control simulation reveals an overall good agreement between the observed daily mean temperature and the simulated one despite some cold biases. Simulated near-surface relative humidity is generally low-biased (up to 20%) while precipitation is overestimated (up to 50% of observed daily precipitation). Those biases are further deciphered through a careful evaluation of the different terms of the surface energy and water budgets. Complementary analyses conditioned to the direction of the large scale flow also investigate how model’s performances over the plain depend on the representation of the orographic flow over the Atlas. This evaluation work is a preliminary and an important step to identify which and how LMDZ parameterizations have to be improved for semi-arid African regions.