Variability of Warm-Season Cloud Episodes over East Asia Based on GMS Infrared Brightness Temperature Observations

Abstract

The present study has used the Geostationary Meteorological Satellite (GMS) IR brightness temperature observations to investigate the regional and intraseasonal variability of east Asian warm-season cloud/precipitation episodes (in distance–time space) due to land–sea contrast and latitudinal effects. The data period was May–August 1998–2001, and harmonic analysis was employed as the major tool for analysis. The full domain of study (20°–40°N, 95°–145°E) was divided into northern and southern zones, and into eastern and western sectors, and statistics of episodes in each subregion were derived and compared. For latitudinal effects, episodes were found to be significantly larger in span and duration in northern (30°–40°N) than in southern (20°–30°N) zones. In the northern zone, the propagation characteristics were also stronger and remain evident even in midsummer, while episodes south of 30°N reversed in direction and traveled westward in July and August. For land–sea contrast, the May–August transition over land (western sector, 95°–120°E) was mainly characterized by an increase in diurnal activities, while that over ocean (eastern sector, 120°–145°E) was characterized by decreased overall activities instead. Over the land itself, significant regional variability also existed, with strongest diurnal signals over the eastern Tibetan Plateau near 100°E, and increased diurnal activities over mountain areas in southeastern China since June. Between the two bands, near 107°E, semidiurnal signals were relatively strong and became dominant in June. This double-peaked structure in the diurnal cycle resulted from overlying signals of convection propagating eastward off the plateau with those induced locally in late afternoon, and the phenomenon was more evident in May–June. Over the ocean, on the other hand, both diurnal and semidiurnal waves had small amplitudes, and the regional variability was much weaker. For intraseasonal transition, the number of large episodes was reduced from May through July, as was mean propagation speed. In August, however, some larger events started to reappear over east Asia.

Impacts of the mountain–plains solenoid and cold pool dynamics on the diurnal variation of warm-season precipitation over northern China

“…The third step consists of plains and hills with a mean elevation of less than 500 m. Due to the strong heating effect of the Tibetan Plateau on the regional weather and climate, most studies on the diurnal cycle of precipitation focus on the Tibetan Plateau and the adjacent lee regions with lower terrain. These studies found that the diurnal precipitation peak usually begins over the Tibetan Plateau in the early afternoon and then propagates eastward (Asai et al, 1998;Wang et al, 2004Wang et al, , 2005Fujinami et al, 2005;Yu et al, 2007a;Zhou et al, 2008;Chen et al, 2009a, b;Xu and Zipser 2011;Bao et al, 2011). The plateaus and mountains of the second step also have an important influence on the local diurnal variation of precipitation: because they are much higher than the plains of the third step, the differential solar heating rate between these two steps yields a temperature gradient that can give rise to the MPS circulation.…”

“…Under the influences of both the eastern Asia monsoon climate (Tao and Chen, 1987) and complex topography, there are clear seasonal and regional changes in the diurnal cycle of precipitation over eastern Asia. Recent studies have investigated the diurnal variation of precipitation over eastern Asia, including different regions of China (Ohsawa et al, 2001;Wang et al, 2004Wang et al, , 2005Hirose and Nakamura, 2005;Yu et al, 2007a, b;Li et al, 2008;Xu et al, 2009;Huang et al, 2010;He and Zhang, 2010, hereafter referred to as HZ10; Bao et al, 2011;Sun and Zhang, 2012).…”

“…Several recent studies have focused on the diurnal cycle of precipitation over the large mountains and adjacent plains/basins (e.g., Carbone et al, 2002;Wang et al, 2004Wang et al, , 2005Yu et al, 2007a, b;Fitzjarrald et al, 2008;Laing et al, 2008;Levizzani et al, 2010;Huang et al, 2010;HZ10;Bao et al, 2011;Sun and Zhang, 2012). Most of these studies have found that the diurnal cycle of precipitation is strongly associated with the thermally driven regional mountain-plains solenoid (MPS) circulation, with the diurnal precipitation peaks initiating on the top or lee of6966 Xinghua Bao and Fuqing Zhang: Impacts of the mountain-plains solenoid and cold pool dynamics plains during the night.…”

Diurnal Variation of Rainfall Associated with Tropical Depression in South China and its Relationship to Land-Sea Contrast and Topography

“…Regional and/or seasonal differences of diurnal rainfall patterns not only occur in China [8,[18][19][20], but also exist in other regions of the world, like in Japan [21], island regions in Asia [22,23], the Asian monsoon region [10][11][12], marine continental islands [24,25], northwest South America [26], the United States Great Plains [27], the Andes in South America [28,29], Africa [30] and even the global tropics [31,32]. The convective rainfall maximum late at night or in the early-morning hours over oceans can be explained by radiation-convection interaction theory [33,34].…”

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

“…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).…”