Quantifying the relationships between precipitation and atmospheric radiative cooling on a range of scales

Monday, 15 December 2014
Alexandra C Naegele and David A Randall, Colorado State University, Atmospheric Science, Fort Collins, CO, United States
In the global energy budget, the radiative cooling of the atmosphere is approximately balanced by latent heating; this implies a positive temporal correlation between the globally averaged atmospheric radiative cooling rate (ARC) and the globally averaged precipitation rate. The high clouds associated with precipitating weather systems tend to reduce the ARC, and so act to damp fluctuations of the global hydrologic cycle. In contrast, on the regional scale, high clouds cause the precipitation rate and the ARC to be negatively correlated in both space and time. The radiative warming associated with the high clouds promotes regional-scale rising motion and so feeds back to enhance the regional precipitation rate. We have used precipitation data from the Global Precipitation Climatology Project and radiative flux data (used to calculate the ARC) from the Clouds and the Earth’s Radiant Energy System (CERES) project to investigate the relationships between the ARC and the precipitation rate on a range of spatial and temporal scales. Results show that the ARC and the precipitation rate are positively correlated globally and in middle and high latitudes, and negatively correlated in the tropics.