A planetary-scale land-sea breeze circulation in East Asia and the western North Pacific

The diurnal wind variation over the East Asian continent is commonly considered to be a combination of a land-sea breeze near the coast and a mountain-valley breeze along the slopes of the Tibetan Plateau. The local land-sea breeze along the coastline typically spans < 100 km into the ocean. However, a detailed examination of the global reanalysis data suggests that this local land-sea breeze circulation apparently couples with the global-scale diurnal atmospheric pressure tide to produce a planetary-scale land-sea breeze with a spatial scale of similar to 1000 km over the western North Pacific. Computations of the momentum budget and equivalent potential temperatures indicate that the atmospheric diurnal tidal wave contributes the most to this circulation feature. A diagnosis of the water vapour budget further suggests that the convergence of water vapour flux, which is related to the convergence of low-level wind induced by the seasonal change of diurnal tidal wave, leads to different times of occurrence of maximum diurnal rainfall over East Asia between summer and winter. Copyright (C) 2010 Royal Meteorological Society