Chong Bum Lee

Distribution and long-term trends in various fog types over South Korea

This study analyzed the spatial and temporal distributions of various fog types over South Korea. Six types of fogs were identified using a classification algorithm based on simple conceptual models of fog formation. The algorithm was applied to a 25-year record of meteorological observations. The most common fog types were radiation fog, prevailing at inland stations, and precipitation fog at coastal and island stations. Declining temporal trends in the frequency of fog events ranging between 2.1 and 10.9 fog events per decade were found at eight inland and two coastal stations. Long-term trends for each fog type show that the decrease in the frequency of fog events is mainly due to a decrease in the frequency of radiation fogs ranging between 1.1 and 8.5 fog events per decade. To identify the potential factors related to the decrease in radiation fog events, the temporal trends in annual mean nocturnal maximal cooling rates and annual mean nocturnal specific humidity during nights with clear sky and clam winds were examined. The results show that the decrease in the frequency of radiation fog events is associated mainly with the pattern of urbanization occurring during the past two decades.

Estimation of evapotranspiration over northeast Asia using modis products and MM5 FDDA data

Evapotranspiraiton (ET) is significant and necessary to understand the hydrological cycle and to assess water resource at any region. The Moderate Resolution Imaging Spectroradiometer (MODIS) offers promising techniques to monitor regional or global ET patterns. Under cloudy conditions, however, some pixels contain missing data that hamper the continuous monitoring of ET. In this study, MODIS atmospheric and land products were used ET estimates under clear and partial clear sky condition, and atmospheric data produced by the Four-Dimensional Data Assimilation (FDDA) between MODIS products and the Fifth Generation Meso-scale Meteorological Model (MM5) and MODIS land products were used ET estimates under cloudy sky condition. MODIS ET under clear and cloudy sky conditions showed a good agreement with nine flux tower observations in Northeast Asia. These results indicate that MODIS can be applied to monitor ET with reasonable accuracy.