The observed variation in cloud-induced longwave radiation in response to sea surface temperature over the Pacific warm pool from MTSAT-1R imagery

This study investigated variations in outgoing longwave radiation (OLR) in response to changes in sea surface temperature (SST) over the Pacific warm pool area (20 degrees N-20 degrees S, 130 degrees E-170 degrees W). OLR values were obtained from recent (January 2008-June 2010) geostationary window channel imagery at hourly resolution, which resolves processes associated with tropical convective clouds. We used linear regression analysis with the domain-averaged OLR and SST anomalies (i.e., Delta OLR, Delta SST; deviations from their 90-day moving averages). Results show that the regression slope appears to be significant only with SST least-affected by cloud radiative forcing, for which SST needs to be obtained as daily average over cloud-free regions (Delta SSTclear). The estimated value of Delta OLR/Delta SSTclear is 15.72 W m(-2) K-1, indicating the presence of strong outgoing longwave radiation in response to surface warming. This atmospheric cooling effect is found to be primarily associated with reduced areal coverage of clouds (-14.4% K-1). Citation: Cho, H., C.-H. Ho, and Y.-S. Choi (2012), The observed variation in cloud-induced longwave radiation in response to sea surface temperature over the Pacific warm pool from MTSAT-1R imagery, Geophys. Res. Lett., 39, L18802, doi:10.1029/2012GL052700.