Atmospheric Chemistry and Physics

Abstract. A cloud resolving model (CRM) is used to inves-tigate the formation of orographic cirrus clouds in the cur-rent and future climate. The formation of cirrus clouds de-pends on a variety of dynamical and thermodynamical pro-cesses, which act on different scales. First, the capability of the CRM in realistically simulating orographic cirrus clouds has been tested by comparing the simulated results to aircraft measurements of an orographic cirrus cloud. The influence of a warmer climate on the microphysical and optical proper-ties of cirrus clouds has been investigated by initializing the CRM with vertical profiles of horizontal wind, potential tem-perature and equivalent potential temperature, respectively. The vertical profiles are extracted from IPCC A1B simula-tions for the current climate and for the period 2090–2099 for two regions representative for North and South America