A study of clouds in the high Arctic summer using ground-based measurements and satellite observations

Arctic clouds often consist of both water and ice particles and form at low altitudes. A previous evaluation of reanalyses data versus in-situ observations in the high Arctic has shown that the performance of the reanalysis was highly dependent on the way the formation and lifetime of Arctic clouds was described in the model. The result motivates a more detailed study of the characteristics of Arctic clouds using in-situ measurement data from the Arctic Summer Ocean Cloud Study (ASCOS) 2008 together with satellite observations from the remote sensing instrument MODIS onboard the Terra and Aqua satellites.

Some major research questions are: Can the satellite instrument see the optically thin clouds observed during ASCOS? In that case, how frequent are these clouds? Can the satellite observations tell us more about the cloud phase and the vertical and horizontal structure of the clouds? How do the clouds influence the radiative balance? How can they persist for so long?

Satellite data from CloudSat/CALIPSO are normally a useful complement to MODIS data. However, CloudSat/CALIPSO data are only available south of 82°N and ASCOS traveled up to 87°N. Nevertheless, we also utilize CloudSat/CALIPSO data further south over the North Atlantic Ocean for a statistical comparison with MODIS and ASCOS regarding the frequency and characteristics of Arctic mixed-phase clouds.