Trends and Sensitivities of Low‐Cloud Cover and Top Height From Spaceborne Lidar Observations

Low clouds effectively cool the Earth by reflecting incoming solar radiation. Detecting low-level clouds with passive satellite sensors can be ambiguous, whereas active remote sensing instruments directly measure cloud-top height. Here, we analyze 14 years of spaceborne lidar observations to assess trends in the occurrence of low-level clouds and their cloud-top height. We find that spatial trend patterns in low-level cloud cover and low-level cloud top height are negatively correlated, that is, regions with a decrease in low-cloud cover tend to show an increase in cloud-top height. We find that spatial trend patterns can be well explained by sea-surface temperature (SST) and estimated inversion strength. Low-level clouds in climatological stratocumulus regions are particularly sensitive to changes in SST (−3.4 to −3.7 % K$^{−1}$ in cloud cover and 50 mK$^{−1}$ in cloud-top height) and estimated inversion strength (3.3 % K$^{−1}$ in cloud cover and −69 mK$^{−1}$ in cloud-top height).