Daytime Variability of Cloud Fraction From DSCOVR/EPIC Observations

The location of the Earth Polychromatic Imaging Camera (EPIC) aboard the Deep Space Climate Observatory (DSCOVR) offers a global view of the Earth and captures its atmosphere at different locations and time of the day. In this paper, we take advantage of that unique feature to study the daytime variability of cloud fraction in a seasonal and zonal context. We observe that the ensemble behavior over ocean has a distinctive convex shape, with higher cloud fractions at early morning and late afternoon, while no such pattern is seen over land. Unique perspectives are obtained by analyzing the cloud fraction of the globe as a whole and separately for each hemisphere, and by studying the effect of the viewing zenith angle on cloud fraction retrievals. Plain Language Summary Images from the Earth Polychromatic Imaging Camera instrument aboard the Deep Space Climate Observatory satellite are unique compared to those from other satellites since the left edge of the image corresponds to sunrise, the right edge to sunset, and the middle to noon. That capability of capturing different parts of the day in a single picture allows us to study the daytime behavior of cloud fraction in new ways. When conducting separate analysis over ocean and land, we find that cloud fraction over ocean is generally higher in the early morning and late afternoon and minimum during the central hours of the day. However, the behavior over land is generally flat with only a very slight increase in the afternoon.