Monitoring Agricultural Drought in South Korea - Monitoring and Predicting Agricultural Drought: A Global Study - page 392

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drought, respectively. A severe drought with EDI of -2.1 and AWRI of 100
mm is seen in the central area. Figure 30.4 shows the variation in drought
days (EDI less than -1.5) for a 25-year period (1974-98). It is evident from
figure 30.4 that severe droughts occurred in 1978, 1982, 1988, and 1994.

E mpirical Orthogonal Function

Figure 30.5 shows the empirical orthogonal function (EOF) analysis of the
EDI. The first eigen mode explained only 55.9% of the total variance. Most
parts of the peninsula show a positive value, with a center over southern
in land area. Its time series shows four negative peaks near pentad (5-day
pe riod) number 13, 26, 44, and 61 that coincide with the four drought
pe riods in early March, middle May, early August, and October, as shown
by Byun and Han (1994) and Byun and Lee (2002). The second eigen mode
in cludes 13.5% of the total variance shown by east-west contours. The
ti me series shows drought concentration at mid-September. The third eigen
m ode shows 7.9% of the total variance with the meridional contours. In the
ea stern part of the peninsula, with negative values in contours, the drought
occurs from March till July, as shown by positive values in time series.

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Line
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-1.3
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Norm
PgEn

G rowing Degree Days

Th e Rural Development Administration (RDA) provides agricultural
w eather information to public on a Web site ( http://weather.rda.go.kr/).
Th e daily, monthly, and yearly data in time and space are available for
te mperature, humidity, radiation, wind speed, precipitation, and so on.

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Figure 30.4 Yearly frequency, i.e. the number of drought days, of drought index (EDI <
-1 .5) based on data for 60 weather stations across Korea.