Cloud‐radiative driving of the Madden‐Julian oscillation as seen by the A‐Train

Abstract

AbstractCloud and water vapor radiative heating anomalies associated with convection may be an effective source of moist static energy driving the Madden‐Julian Oscillation (MJO). In this paper 5 years of radiative heating profiles derived from CloudSat radar and Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation data are analyzed to document radiative heating anomalies during the MJO. Atmospheric shortwave absorption and surface longwave radiation anomalies are of opposite sign and 10–20% as large as top‐of‐atmosphere outgoing longwave radiation (OLR) anomalies, confirming that OLR provides a useful estimate of the total column radiative heating anomaly. Positive anomalies generally peak about 1 week before the MJO peak and are smallest over the Indian Ocean. Anomalies over the Maritime Continent are strongest and coincident with the MJO peak. Shortwave heating profile anomalies are weaker than longwave anomalies in the active region of the MJO but generally of opposite sign; thus, shortwave heating damps the longwave destabilization of the lower troposphere. The exception is the onset phase of the MJO, where shortwave and longwave heating anomalies due to thin cirrus are both positive in the upper troposphere and exert a stabilizing influence. Specific humidity anomalies in the middle troposphere reach 0.5 g kg−1, but the associated clear‐sky heating anomaly is small. Radiative enhancement of column moist static energy becomes significant as precipitation increases before the MJO peak and remains high after the MJO peak as precipitation begins to decline. Elevated radiative heating after the peak may contribute to destabilizing the MJO.