A Novel Thermodynamical Predictor of Tropical High‐Cloud Area Coverage: Estimated Anvil‐Outflow Stability

Abstract The stability at the lapse‐rate tropopause (LRT) was previously defined as the upper‐tropospheric stability (UTS and S UT ) but might underestimate the stability control on high‐level clouds, since there is little direct connection between convective processes and the thermal stratification at the LRT. Here, a novel estimated anvil‐outflow stability (EAS) based on the minimum stability in the upper troposphere is proposed. At the Manus site, the results show that small and large values of the LRT‐based UTS and S UT both correspond to strong divergence and frequent occurrence of high‐level ice clouds. In contrast, smaller EAS corresponds to stronger convective outflows to produce likely more high‐level ice clouds, with a strong negative correlation. In tropics, EAS better explains the geographic distribution of high‐level cloud coverage (HCC) and its temporal variations than UTS and S UT . With a strong linear correlation, EAS is likely a simple useful predictor of HCC.