Impact of poleward heat and moisture transports on Arctic clouds and climate simulation

Many General Circulation Models (GCMs) have difficulty in simulating Arctic clouds and climate causing a large inter-model spread. In an attempt to address this issue, two Atmospheric Model Inter-comparison Project (AMIP) simulations from the Community Atmosphere Model version 5 (CAM5) and from the Seoul National University (SNU) Atmosphere Model version 0 (SAM0) with a Unified Convection Scheme (UNICON) are employed to examine the impact of poleward heat and moisture transports on the Arctic clouds and climate simulation. Over the Arctic, SAM0 simulates more cloud fraction and cloud liquid mass than CAM5, reducing the negative Arctic clouds biases in CAM5. The analysis of cloud water condensate rates indicates that this improvement is associated with an enhanced net condensation rate of water vapor into the liquid condensate of the Arctic low-level stratus, which in turn is driven by enhanced poleward transports of heat and moisture by mean meridional circulation and transient eddies. The reduced Arctic cloud biases lead to improved simulations of surface radiation fluxes and near-surface air temperature over the Arctic throughout the year. The association between the enhanced poleward transports of heat and moisture and more liquid clouds over the Arctic is also evident in the multi-models analysis. Our study indicates that the proper simulation of poleward heat and moisture transport is one of the key factors necessary for improving the simulations of Arctic clouds and climate.