Defining Three Rainy Seasons and the Hydrological Summer Monsoon in Korea using Available Water Resources Index.

Abstract

A new scheme that can define three rainy seasons, and the hydrological summer monsoon in Korea, has been proposed, examined, and verified to be effective. In the scheme, the Available Water Resources Index (AWRI) that is the accumulated precipitation value in which daily reduction of water, and the duration of accumulation are taken into account quantitatively.With this scheme, the onset and ending dates of three rainy seasons are defined by such singularities as the smallest, the biggest, the minimum, and the maximum of the AWRI in a year. The intensities of these rainy seasons are defined by the value of the maximum AWRI, flood index, and drought index.The first rainy season (Bom-Changma) starts in early April, when the minimum value of the AWRI in a year appears, and when the mean southerly wind at 925 hPa level become stronger then that at the 500 hPa level, and ends at May 15. The second rainy season (Changma) starts in late June and ends at 16-20 July. The third rainy season (Kaul-Changma) starts at mid August, and ends at 3-5 September that has the maximum value of the AWRI in a year, and that is the last date of mean southerly wind at the 925 hPa level.Finally, the hydrological summer monsoon is proposed to be defined as the period of increasing water resources that is from the minimum to the maximum of the AWRI, from the onset of Bom-Changma till the end of Kaul-Changma. From a turning point of meridional wind system to the end of mean southerly wind in the low level atmosphere, and that is concurrent with the summer monsoon.

Spatial and temporal comparisons of droughts over Korea with East Asia

“…Most drought events in Korea are seasonally specific, mainly occurring from autumn to the next spring, and withdrawing when the moisture is replenished by the activation of summer monsoon systems (Byun and Lee, 2002). The 12-month SPI, used as a drought index in this study, does not take into account the seasonality of Korean drought.…”

Climate change: assessment and monitoring of meteorological and hydrological drought of Wadi El Hammam Basin (NW- Algeria)

“…To amend these disadvantages, [8] proposed Effective Drought Index (EDI), in its original form is computed with a daily time step using daily rainfall data. [10,13,15] have verified the merits of EDI in precipitation climatology, and their merits on drought monitoring have recognized by [11]. Effective precipitation (EP) that represents resources daily depletion of water is the base of concept EDI [14].…”

Introduction of East Asian Drought Monitoring System

“…Thus, the AWRI enables the water supplier and the water consumer to easily understand the amount of available water resources. See Byun and Lee (2002) for more detailed information.…”

“…The validity of these advantages has been proven in previous studies (Byun and Lee 2002;Yamaguchi and Shinoda 2002;Morid et al 2006b;Smakhtin and Hughes 2007;Akhtari et al 2008). In addition, the available water resources index (AWRI; Byun and Lee 2002), which is a hydrological index, and the precipitation data are provided in the same form. Researchers can easily calculate the drought index using PGI FORTRAN (0) as the scripting language.…”