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 ~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.