Understanding the spring cloud onset over the Arctic sea-ice

Abstract. Using 13 years of space-based lidar cloud observations over the Arctic sea-ice, we show that the low cloud cover increases from 34 % to 71 % between 7 April and 7 May, mainly due to the increase of liquid-containing clouds below 1 km altitude. This study assesses the relative roles of moisture transport from the mid-latitudes and the spring warming driven by the seasonal increase of solar radiation in setting this transition called “spring cloud onset”. We highlight that daily moisture