Interpretation of the Transient Variations in the Time Series of Precipitation Amounts in Seoul, Korea. Part I: Diurnal Variation

Abstract

Characteristics of temporal variations of precipitation for Seoul, Korea, have been examined using a 220-yr record. Precipitation records from modern rain gauges were used for 1908?96 together with the traditional Korean rain gauge precipitations for 1777?1907. The precipitation time series was partitioned into three precipitation regimes: wet period 1 (WP1; 1783?1883), the dry period (DP; 1884?1910), and wet period 2 (WP2; 1911?96). The basic features of the records were examined, and the diurnal variations derived from hourly precipitation were investigated. There were similarities between the statistical characteristics of the time series for WP1 and WP2, but the DP showed many statistical characteristics different from WP1 and WP2. Diurnal cycles derived from the hourly precipitation rates in Seoul are generally consistent with previous observations in maritime areas, but some differences are apparent between the two WPs and the DP in the mean diurnal cycle and its seasonal variation. The WPs show similar characteristics of diurnal cycle with a peak near 0600 LST and a broad evening minimum around 1900?2400 LST during most of the years. The amplitude of the normalized diurnal cycle increases as precipitation intensity increases, and the timing for the morning peak is slightly earlier for the intense precipitation than for the light and moderate precipitation. In contrast, the morning maximum does not manifest itself clearly during the dry period. The diurnal cycle is seen in all seasons. The morning peak during Changma (the rainy season over Korea) results mainly from intense precipitation events, which are confined to a shorter period of the day than light or moderate precipitation.