Reviews and syntheses: Influences of landscape structure and land uses on local toregional climate and air quality

Abstract. The atmosphere and the land surface interact in multiple ways, for instance though the radiative-energy balance, the water cycle or the emission-deposition of natural and anthropogenic compounds. By modifying the land surface, land-use and land-cover changes (LULCCs) and land management changes (LMCs) alter the physical, chemical and biological processes of the biosphere and therefore all land-atmosphere interactions, from local to global scales. Through socio-economic drivers and regulatory policies adopted at different levels (local, regional, national or supranational), human activities strongly interfere in the land-atmosphere interactions, at those activities lead to a patchwork of natural, semi-natural, agricultural, urban and semi-urban areas. In this context, urban and peri-urban areas are of particular attention since land transformation can lead to important environmental impacts and affect the health and life of millions of people. The objectives of this review is to synthesize the existing experimental and modelling works that investigate physical, chemical and/or biogeochemical interactions between land surface and the atmosphere mainly in urban or peri-urban landscapes at regional and local scales. In the context of LULCCs, the importance of land-atmosphere interactions for climate and air quality have been analysed in many studies published over the last years, with a large range of spatial and temporal scales investigated. The conclusions from such a synthesis is first that (i) the description of land-use and land-management (e.g. areas concerned, type of crops, whether or not they are irrigated, quantity of fertilizers used and actual seasonality of application), including surface properties and emission sources, is inexistent (or very poor) in global and even more in regional climate models. Not taking into account these characteristics may bias the regional projections used for impact studies. (ii) Land-atmosphere interactions are often specific to the case study analysed; therefore, in this perspective, one can hardly propose general solutions or recommendations. (iii) Adaptation strategies, proposed after the evaluation of climatic impacts on the targeted resource have been derived, but are often biased as they do not account for feedbacks on local/regional climate. (iv) There is space for considering atmospheric chemistry, through land-atmosphere interactions, as a decision parameter for land-management, helping to maintain air quality and supporting ecosystem functioning. (v) There is a lack of an integrated tool, which includes the many different processes of importance in an operational model, to test different land use or land management scenarios at the scale of a territory.