Distribution of seasonal rainfall in the East Asian monsoon region

Theoretical and Applied Climatology (Impact Factor: 1.74). 01/2002; 73(3):151-168. DOI: 10.1007/s00704-002-0679-3

ABSTRACT ¶This study deals with the climatological aspect of seasonal rainfall distribution in the East Asian monsoon region, which
includes China, Korea and Japan. Rainfall patterns in these three countries have been investigated, but little attention has
been paid to the linkages between them. This paper has contributed to the understanding of the inter-linkage of various sub-regions.
Three datasets are used. One consists of several hundred gauges from China and South Korea. The second is based on the Climate
Prediction Center (CPC) Merged Analysis of Precipitation (CMAP). The two sources of precipitation information are found to
be consistent. The third dataset is the NCEP/NCAR reanalysis 850-hPa winds.

The CMAP precipitation shows that the seasonal transition over East Asia from the boreal winter to the boreal summer monsoon
component occurs abruptly in mid-May. From late March to early May, the spring rainy season usually appears over South China
and the East China Sea, but it is not so pronounced in Japan. The summer monsoon rainy season over East Asia commonly begins
from mid-May to late May along longitudes of eastern China, the Korean Peninsula, and Japan. A strong quasi-20-day sub-seasonal
oscillation in the precipitation appears to be dominant during this rainy season. The end date of the summer monsoon rainy
season in eastern China and Japan occurs in late July, while the end date in the Korean Peninsula is around early August.
The autumn rainy season in the Korean Peninsula has a major range from mid-August to mid-September. In southern China, the
autumn rainy season prevails from late August to mid-October but a short autumn rainy season from late August to early September
is noted in the lower part of the Yangtze River. In Japan, the autumn rainy season is relatively longer from mid-September
to late October.

The sub-seasonal rainfall oscillation in Korea, eastern China and Japan are explained by, and comparable to, the 850-hPa circulation.
The strong westerly frontal zone can control the location of the Meiyu, the Changma, and the Baiu in East Asia. The reason that the seasonal sea surface temperature change in the northwestern Pacific plays a critical role
in the northward advance of the onset of the summer monsoon rainfall over East Asia is also discussed.

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    ABSTRACT: In this study, climate over Korea based on the Historical scenario induced by HadGEM2-AO is simulated by WRF. For this purpose, a system that can be used be for numerical integration over the Far East Asian area of the center of the Korean Peninsula with 12.5 km-horizontal resolution was set-up at "Haebit", the early portion of KMA Supercomputer Unit-3. Using the system, the downscaling experiments were conducted for the period 1979-2010. The simulated results of HadGEM2-AO and WRF are presented in terms of 2 m-temperature and precipitation during boreal summer and winter of Historical for the period 1981~2005, compared with observation. As for the mean 2 m-temperature, the general patterns of HadGEM2-AO and WRF are similar with observation although WRF showed lower values than observation due to the systematic bias. WRF reproduced a feature of the terrain-following characteristics reasonably well owing to the increased horizontal resolution. Both of the models simulated the observed precipitation pattern for DJF than JJA reasonably, while the rainfall over the Korean Peninsula in JJA is less than observation. HadGEM2-AO in DJF 2 m-temperature and JJA precipitation has warm and dry biases over the Korean Peninsula, respectively. WRF showed cold bias over JJA 2 m-temperature and wet bias over DJF precipitation. The larger bias in WRF was attributed to the addition of HadGEM2-AO's bias to WRF's systematic bias. Spatial correlation analysis revealed that HadGEM2-AO and WRF had above 0.8 correlation coefficients except for JJA precipitation. In the EOF analysis, both models results explained basically same phase changes and variation as observation. Despite the difference in mean and bias fields for both models, the variabilities of the two models were almost similar with observation in many respects, implying that the downscaled results can be effectively used for the study of regional climate around the Korean Peninsula.
    Atmosphere. 12/2013; 23(4).
  • Climate Research 12/2011; 50(2):141-159. · 2.71 Impact Factor
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    ABSTRACT: Rainfall is a complex phenomenon with high spatiotemporal variability. Identification of homogeneous rainfall zones to better analyse the rainfall intensity and extent is of vital significance for water resources management and mitigation of potential hazards from extreme events, i.e. droughts and floods. Appropriate zoning of homogeneous rainfall regions may give better understanding of rainfall patterns by resolving small scale variations. Although homogeneous rainfall zones have been established at country scale based on climatological mean behaviour, there has been little attempt to identify zones over broader scale with consistently homogeneous rainfall variability. This study employed K-means and Hierarchical clustering methods to establish homogeneous rainfall zones in the East Asia monsoon region (20°N–50°N, 103°E–149°E) using 30 years (1978–2007) monthly rainfall data at 0.5° grid resolution. Various cluster validation indices were used to assess the optimal number of homogeneous rainfall zones. The comparison of K-means and Hierarchical clustering showed that although both methods were able to define the homogeneous rainfall zones well with spatial contiguity, the K-means clustering outperformed the Hierarchical clustering in identifying more distinct zones with diverse rainfall characteristics. Mann-Kendall and linear regression tests were used for seasonal and annual rainfall trend analysis in the homogeneous rainfall zones. The study revealed that the region experiences distinct rainfall regimes over different zones. Furthermore, significant increasing and decreasing trends were observed over different zones with strong seasonal variation that indicate the aggravated stress of climate induced disasters, i.e. droughts and floods over the East Asia monsoon region.
    International Journal of Climatology 06/2014; · 3.40 Impact Factor


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