Robert Wood(1), Chris Bretherton(1), Peter Caldwell(1), Martin Kohler(2)
1. University of Washington, Seattle, WA, USA
2. ECMWF, Reading, UK
Evidence is presented for a continental influence upon marine boundary layer clouds over the remote SE Pacific Ocean. Previous studies have shown an enhanced diurnal cycle of low clouds over the SE Pacific compared to their NE Pacific counterparts. Here we present evidence that supports a mechanism of diurnally modulated heating over the Andes generating a deep gravity wave that propagates over the SE Pacific with a phase speed of 30-50 m/s. The wave causes a diurnal cycle of lower tropospheric subsidence, even at distances greater than 1000 km from land, that can be as important as entrainment and shortwave radiative absorption at driving the diurnal cycle of marine boundary layer cloud and boundary layer properties. Climatological consequences for the earth's radiative balance are discussed.