Extratropical Lapse Rates in Very Hot Climates

Middle latitude eddies redistribute heat across the planet, pushing warm tropical air poleward on one side and bringing cold polar air equatorward on the other. At the same time they redistribute heat vertically, stabilizing atmospheric lapse rates in the process. The interplay between convective processes and the stabilizing effects of these large-scale systems remains debated, and the purpose of this study is to examine how the frequency and distribution of nearly moist adiabatic lapse rates varies with climate. We use output from NCAR's Community Atmospheric Model 3 at T42 resolution (see Caballero and Huber (2010) for further details) in which carbon dioxide levels vary over a wide range: from 1990 levels of 355 ppm to 8960 ppm. We assess the spatial and temporal climatology of tropospheric lapse rates, which evolves as the influence of middle latitude eddies declines in progressively warmer climate states. The increasing prominence of middle latitude lapse rates nearly neutral with respect to deep moist convective processes also causes an expansion of regions where tropical cyclones are possible in the hottest state.