Characteristic Differences of Rainfall and Cloud-to-Ground Lightning Activity over South Korea during the Summer Monsoon Season

Abstract

In this paper the characteristic variations of cloud-to-ground (CG) lightning and total precipitation during the Korean summer monsoon (June?August) season have been extensively analyzed for different climate regimes. The data used in this study consist of the monthly CG lightning flash count as detected by the lightning detection network installed at the Korean Meteorological Administration (KMA) and the monthly precipitation data from 23 meteorological observatories spread over the Korean peninsula for a period of 10 yr from 1988 to 1997. Temporal and spatial scales of 1 month and 102 km2, respectively, were considered to determine the seasonal values of rain yield or rain volume per CG flash (defined as the ratio of total precipitation to CG flash count over a common area). Seasonal values of rain yield have been compared with that of monthly values separately. The results of variation of the rain yield during the different months constituting the monsoon season are also presented. Results show that the variation of rain yield for the monsoon season closely resembles that of July indicating that July, rather than the other two monsoon months, dominates the overall monsoon pattern. The maximum values of rain yield are observed in the east coast of the Korean peninsula, particularly in the region east of Tae-back Mountain, with a mean value of 3 ? 105 m3 fl?1 while the minimum value is seen in the west of Tae-back Mountain, with an average value of 8 ? 104 m3 fl?1. The method for separating convective rain designed on broad heterogeneity similar to the Petersen and Rutledge method shows on average 82% of the total rainfall is convective in nature at the west coast stations, 53% is convective at the middle of the peninsula, and 46% is convective at the east coast stations. Maximum convective rain occurred at Kanghwa in the northwest, while the minimum was seen at Ulsan in the southeast. The correlation coefficient between the total precipitation and CG lightning during the summer monsoon season is 0.54, which is not very high since in most cases total precipitation persists longer than CG lightning. This may be due to the occasional development of mesoscale convective systems (MCSs), which produce light stratiform precipitation during their dissipation stage or might have been contaminated by the upslope precipitation or by nonlightning producing frontal precipitation. This low correlation coefficient could also be due to the episodic presence of warm rain convection or a ?low-echo centroid? precipitation system.