A novel diagnostic technique to investigate cloud-controlling factors

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Abstract

[1] Cloud properties depend on the local meteorological conditions. This relation is quantified using a simple framework which expands on previous methodologies. This novel diagnostic technique is applied in order to understand and assess the relative contribution of various environmental factors to the observed interannual and seasonal variations in cloud properties. In this analysis framework, sea surface temperature, sea level pressure, and, to a lesser extent, the humidity field are the largest contributors to the interannual cloud anomalies in the equatorial Pacific. In addition, in contrast to previous studies, we find that the interannual variability of the ratio of shortwave to longwave cloud radiative effect (N) is independent of the tropopause temperature. Finally, we quantify the role of different factors which are thought to influence the seasonal cycle of the stratocumulus in the subtropics. Off the California coast, the lower tropospheric stability (LTS) better describes the seasonal low‒cloud amount changes than the estimated inversion strength (EIS). When the spatial variation in LTS (or EIS) and low‒cloud amount is considered within a season, a different relationship is found that depends on the season. The nonlinear relationships between environmental factors and cloud properties can, to a certain extent, be described within the novel framework proposed.

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