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

Abstract

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.

Maintenance mechanisms for the early‐morning maximum summer rainfall over southeast China

“…The spatial resolution of GEOS5 is 0.667 • longitude × 0.5 • latitude (about 66.7 km in longitude × 50 km in latitude, a scale smaller than that of a typical local land-sea breeze ∼100 km) which provides a good depiction of the regional diurnal wind variation (Huang et al, 2010). The precipitation analysis uses the TRMM (Tropical Rainfall Measuring Mission; Simpson et al, 1996) 3G68 2B31 dataset because it uses both passive and active microwave data to produce the best rain estimate for TRMM (Haddad et al, 1997a(Haddad et al, , 1997b, which has been shown to resemble rain gauge observations, with a good representation of the diurnal rainfall variability (Hong et al, 2005;Zhou et al, 2008;Chen et al, 2009).…”

Future changes in propagating and non-propagating diurnal rainfall over East Asia

“…7a). The role of −∇·Q in contributing to the change of diurnal rainfall variation over southeast China was examined by Huang et al (2010) through the diagnosis of water vapor budget equation.…”

“…1) that features non-propagating (afternoon) diurnal rainfall (e.g., Huang et al 2010). The mechanisms responsible to such a regional difference in diurnal rainfall have been studied extensively (e.g., Wallace 1975;Oki and Musiake 1994;Yang and Slingo 2001;Nesbitt and Zipser 2003;Sorooshian et al 2002;Yu et al 2007a, b;Huang et al 2010;Huang and Wang 2014).…”

“…Earlier studies indicated that the solenoidal circulation between the Tibetan Plateau and its leeside lowlands contributes to the extent of the propagating diurnal rainfall over the Yangtze River (Wang et al 2004;Hirose and Nakamura 2005;Wang et al 2005;Huang et al 2010). There, the East Asian jet stream drives the diurnal convection initiated east of the Tibetan Plateau to propagate eastward (Wang et al 2004).…”

“…Using observational data, Huang et al (2010) showed that the change in diurnal rainfall over southeast China is mostly contributed by the changing −∇·Q rather than by evaporation or water vapor storage alone. An earlier study by Chen (2005) also demonstrated that moisture convergence is the major factor in maintaining the change of diurnal rainfall over the East Asian summer monsoon region 1 Here, (−∇ · Q) = −∇ · p 0 300hPa ⇀ Vqdp , where V denotes the horizontal wind, q is the specific humidity, and p is the pressure level.…”