Effects of Diurnal Variations of Outgoing Longwave Radiation Over the Tropical Oceans

Several current problems in atmospheric radiation over the tropical oceans may have at least partial solutions as effects of diurnal variations of outgoing longwave radiation (OLR). At issue are explanations for the following: a) excessively large amplitudes (in relation to theory) of the diurnal thermal tides over the tropical oceans (Braswell and Lindzen 1998); b) reported observations of excessively large direct atmospheric absorption of incident broadband solar radiation, which conflict with prior work and concurrent, collocated narrowband measurements centered in the visible spectrum (Cess et al. 1998); and c) the observed morning intensity maximum of the deepest, most intense tropical convective systems (Hall and Vonder Haar 1999; Gray and Jacobson 1977). The present lack of diurnally resolved broadband satellite OLR observations of sufficient accuracy and temporal resolution has been a restraint on our approach to these issues. Nevertheless, beginning with the morning maxim of intense tropical convection, we discuss each of these problems and show evidence of common links to OLR-related processes.