Global liquid and ice cloud properties variability from DSCOVR/EPIC observations

Abstract:

Daytime cloud coverage evolution is pivotal for the accurate determination of the energy balance of the atmosphere. Yet, polar-orbiting satellites are unable to capture it and geosynchronous satellites only provide measurements for specific regions of the Earth. Up to date, daytime changes in cloud fraction have been determined either with ISCCP or with General Circulation Models, providing contrasting results in many situations. Here we show that the Level 2 cloud products of the Earth Polychromatic Imaging Camera (EPIC) onboard DSCOVR satellite mission present an unparalleled opportunity for examining the changing daytime global coverage. DSCOVR is located at the Lagrange point L1, 1.6x10⁶ km from Earth toward Sun, capturing the whole globe at once every one or two hours. In this study, we use four years of data to present evidence that, for the majority of the Earth, the amount of clouds increases in the morning and afternoon with clearer skies at noon. We divide our study into liquid and ice clouds and investigate the seasonal differences on a global scale. Furthermore, we examine the daytime evolution of related cloud properties such as effective height and optical thickness, showing that those parameters also evolve throughout the day.