How can EarthCARE satellite observations help improve Greenland’s clouds in the regional climate model RACMO?

Clouds play an important role in Greenland’s surface mass balance, as they govern accumulation through precipitation and influence surface melt by altering the radiative balance. Therefore, correctly representing clouds in polar regional climate models is crucial for obtaining reliable surface mass balance estimates and projections. However, the complex, small-scale cloud microphysical processes involved in cloud formation, dissipation, and phase changes are often poorly represented in models. As in-situ observations of polar clouds are sparse, satellite observations can be an effective tool for evaluating and improving climate models. The new EarthCARE satellite, launched in May 2024, provides high-resolution co-located observations of the vertical structure of clouds and aerosols, and top-of-atmosphere radiation. Here, we show how these observations can be used to evaluate cloud representation in climate models by comparing them with output of the polar regional climate model RACMO (version 2.4p1).

We will present a comparison of over one year of multi-instrument EarthCARE observations of clouds and radiation for the Greenland region with model output that is co-located in time and space. We find that for clouds in all phases (solid, liquid, and mixed), RACMO tends to miss clouds at higher altitudes and underestimates water content for most locations and vertical levels. As a result, in RACMO, snowfall is less often generated at higher altitudes but more often at lower altitudes. However, the simulated snowfall rates are underestimated. Rainfall shows similar patterns, with rainfall modeled more frequently, but with lower rainfall rates. We will use these comparisons, along with EarthCARE’s radiation observations and retrieved cloud microphysical properties, to work towards improved cloud representation, surface radiation, and surface mass balance estimates in RACMO.