1. Studying the Arctic Stratiform Clouds Using Four Different Microphysics Schemes Ping Du, Prof. Eric Girard

2. The Arctic cloud, especially the mixed-phas cloud, which is dominant in the lower level, plays a key role in the Arctic climate, and due to its very complicated characteristics, it is challenging for the climate model,specific for the microphysics scheme, to represent the Arctic cloud properly. In the current GEMCLIM model the single-moment microphysics schemes (Sundqvist and Kong&Yau schemes) are developed mostly for the low latitude clouds, which can not produce the complex Arctic cloud processed very well. Beside these schemes we introduce other 2 more advanced schemes (Milbrandt&Yau and Mossison schemes), which are 2- moment schemes and consider the cloud and precipitation formation, cloud dynamics and thermodynamics in more details. Fixing the domain we use the four schemes to do the simulations during the Surface Heat and Energy Budget of the Arctic observation (SHEBA) period, and compare the cloud properies, such as, Liquid water path (LWP), Liquid Water Content (LWC) and Ice Water Content (IWC) to the observation data, furthermore, to evaluate the features of the four different schemes.

3. Premier results: On May 19th, a very thin mixed-phase cloud was present early in the day and slowly dissipated at the end of the day. The temperature of the cloud was between -5ºC and - 10ºC. Liquid dominates ice in this cloud. Most schemes underestimate the LWC and IWC observed by the aircraft, except for Sun that overestimates the IWC. The vertical structure of the cloud is however well captured by all schemes except for the second maximum above, which was observed only a few hours and rapidly dissipated. Sun—Sundgvist scheme Kyau---Kong&Yau scheme Mil----Milbrandt&Yau scheme Morr---Morrison scheme

4. On May 30th, the cloud was thicker (3000 m) and warmer with temperature varying between -5ºCand 0ºC. Again, Sun overestimates the IWC and underestimates the LWC. It appears that the phase partitioning, which depends on temperature, is not appropriate for these Arctic clouds. Morr substantially overestimates the LWC and LWP. This positive bias is not in agreement with previous results for the M- PACE case and will have to be further investigated. The IWC is well captured by Morr and Mil and substantially overestimated by Kyau.. The vertical structure of the cloud is not well captured by all schemes except for Morr. On the other hand, Mil is the only scheme reproducing the layer-like structure of LWC. Other days of the SHEBA field experiment will also be simulated to further evaluate the microphysics schemes.