Global summer monsoon rainy seasons

Abstract

ABSTRACT:A concise and objective definition of monsoon rainy season characteristics is proposed for worldwide monsoon regions. The result highlights six major summer monsoon rainy season domains and the mean dates of the local onset, peak and withdrawal phases of the summer monsoon rainy season. The onset phases occur progressively later poleward in the continental domains but primarily eastward in the oceanic monsoon regions. The rainy season retreats equatorward over the continental and oceanic monsoon regions. The length of the rainy season decreases poleward and shorter rainy season can also be found over the outskirts of warm water. Some exceptions exist in terms of the characteristics of rainy season, e.g. the westward advance of rainy season over North Africa and an apparently prolonged rainy season in the Korean peninsula. The results here are basically compatible with those obtained in previous studies on regional monsoons.A definition of the seasonal wind overturning is proposed. Combining rainfall and winds, we stratify the global monsoon into strong and weak categories. The strong monsoons are typically in the regions with both concentration of summer rainfall and annual reversal of low-level winds, while the weak monsoon features only a contrasting wet-dry season. Seemingly, some mid-latitude regions with wind reversals are not monsoonal because of the reversals being opposite to the monsoon overturning and the rainfall patterns being more or less Mediterranean.The comparison between the monsoon domains derived from Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP) and the 40-year European Centre for Medium-Range Weather Forecasts Re-Analysis (ERA-40), the Japanese 25-year Reanalysis (JRA-25) and National Centers for Environmental Prediction (NCEP) datasets show good capabilities of the reanalyses in demarcation of the major monsoon rainy season domains in the tropics and subtropics. But the reanalyses are less realistic in the mid-latitudes of Eurasia and North America. The result here provides the simple yet objective definitions of monsoon domain, onset, peak and withdrawal which are useful for validation of GCMs.

Paleogene monsoons across India and South China: Drivers of biotic change

“…However the criteria for recognising monsoon climates in these studies fall far short of the those used in the meteorological definitions proposed by Zhang and Wang (2008).…”

“…Zhang and Wang (2008) recognised six major summer monsoon rainy season domains characterised by the mean dates of the local onset, peak and withdrawal of the rainy season, coupled with wind parameters. The thresholds for these meteorological parameters were in part chosen to differentiate what here we will refer to as 'enhanced' monsoon climates from rainfall seasonality associated with latitudinal migrations of the Inter-tropical Convergence Zone (ITCZ), which we will call 'ITCZ monsoons'.…”

The Formation of a Surface Anticyclone over the Yellow and East China Seas in Spring

“…The southerlies in the western Yellow Sea are replaced by northwesterly winds, and the westerlies advance southward to occupy the Bohai-Yellow Seas, confirming the effect of the thermal wind induced by the coastal temperature contrast in the control run. Without the seas but with the ESKF, the surface wind field exhibits the typical East Asian winter monsoon pattern: northwesterlies north of 30 • N and northeasterlies south of 30 • N (Zhang and Wang 2008;Tao and Chen 1987). In the NoYS run, an anticyclonic circulation develops over the cool SST between the new model coastline and the ESKF, again in support of the land-sea contrast effect.…”

“…The Asian monsoon system is at a transitional stage in April. The Yellow-East China Sea anticyclone (YESA) brings the southerly flow to the northwestern Yellow Sea far before the onset of the East Asian summer monsoon, which is in June after the South China Sea monsoon breaks out in mid-May (Tao and Chen 1987;Huang 1998;Wang and LinHo 2002;Zhang and Wang 2008). At Qingdao station (Fig.…”

Decadal-Scale Variation of South Asian Summer Monsoon Onset and Its Relationship with the Pacific Decadal Oscillation

“…Their criterion for determining the summer monsoon onset date is that the reconstructed precipitation data exceeds 5 mm day 21 above the climatological January (July) mean in the Northern (Southern) Hemisphere. This simple and objective method enables discussion of the characteristics of global monsoon rainy seasons (Zhang and Wang 2008). The India Meteorological Department (IMD) annually determines the date of the summer monsoon onset over Kerala, a state in southwestern India.…”