%0 Journal Article
%T ENSO surface shortwave radiation forcing over the tropical Pacific
%A K. G. Pavlakis
%A N. Hatzianastassiou
%A C. Matsoukas
%A A. Fotiadi
%A I. Vardavas
%J Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD)
%D 2008
%I Copernicus Publications
%X We have studied the spatial and temporal variation of the downward shortwave radiation (DSR) at the surface of the Earth during ENSO events for a 21-year period over the tropical and subtropical Pacific Ocean (40∼ S每40∼ N, 90∼ E每75∼ W). The fluxes were computed using a deterministic model for atmospheric radiation transfer, along with satellite data from the ISCCP-D2 database, reanalysis data from NCEP/NCAR for the key atmospheric and surface input parameters, and aerosol parameters from GADS (acronyms explained in main text). A clear anti-correlation was found between the downward shortwave radiation anomaly (DSR-A) time-series, in the region 7∼ S每5∼ N 160∼ E每160∼ W located west of the Ni o-3.4 region, and the Ni o-3.4 index time-series. In this region where the highest in absolute value DSR anomalies are observed, the mean DSR anomaly values range from  45 Wm 2 during El Ni o episodes to +40 Wm 2 during La Ni a events. Within the Ni o-3.4 region no significant DSR anomalies are observed during the cold ENSO phase in contrast to the warm ENSO phase. A high correlation was also found over the western Pacific (10∼ S每5∼ N, 120每140∼ E), where the mean DSR anomaly values range from +20 Wm 2 to  20 Wm 2 during El Ni o and La Ni a episodes, respectively. There is also convincing evidence that the time series of the mean downward shortwave radiation anomaly in the off-equatorial western Pacific region 7每15∼ N 150每170∼ E, precedes the Ni o-3.4 index time-series by about 7 months and the pattern of this anomaly is indicative of ENSO operating through the mechanism of the western Pacific oscillator. Thus, the downward shortwave radiation anomaly is a complementary index to the SST anomaly for the study of ENSO events and can be used to assess whether or not El Ni o or La Ni a conditions prevail.
%U http://www.atmos-chem-phys.net/8/5565/2008/acp-8-5565-2008.html