Eun-Ha Sohn

COMS-Based Retrieval of Daily Actual Evapotranspiration over Korea

Evapotranspiration (ET) from the land surface is an important hydrometeorological factor in the exchange of energy between the atmosphere and land surface. The accurate quantification for management of water resources and understanding of climate change are crucial, requiring continuous temporal and spatial monitoring. The objective of this study is to apply and estimate daily actual ET using semiempirical method, B-method, which is based on surface energy balance over heterogeneous area, Korea. To estimate daily ET, we used geostationary meteorological satellite data (Communication, Ocean and Meteorological Satellite, COMS) and polar-orbiting satellite data (Systeme Pour ľObservation de la Terre, SPOT). Estimated daily ET using only satellite data was relatively accurate and reflects land surface characteristics. It had high periodicity and spatial resolution over a wide area on clear-sky days. The daily ET was overestimated by about 1 mm/day at the two flux tower measurements sites, but the simulated seasonal variation and pattern were in good agreement with flux tower measurements. In the mixed forest, the root-mean-square error (RMSE) was 0.94 mm/day and the bias was 1.05 mm/day, while, in the rice paddy, RMSE was 1.12 mm/day and bias was 1.21 mm/day.

Operational Technique in Typhoon Wind Radii Using Satellite Microwave Remote Sensor Data

In this paper, the system will be introduced and explain for the practical techniques might consider and use the typhoon wind radii on near real-time using satellite microwave remote sensor data. The system is created to use Typhoon weather forecast and validation of radii of 15 and 25 m/s (around 30 and 50 kts) gale-force wind over the ocean using satellite data. Korean Meteorological Administration (KMA) is receiving Defense Meteorological Satellite Program (DMSP), AQUA, and QuikSCAT data directly or indirectly via File Transfer Protocol (FTP) over the Global Telecommunication System (GTS) and process the wind speed. Also it receives Satellite Report (SAREP) which reports the position of the center of typhoon and it will be used for radius calculation. The system will calculate the radii of 15 and 25 m/s winds for four quadrants and also plot the each directional winds according to the distance from the center of the typhoon. It will run every 6 hours from the beginning of tropical depression to touch down to the land. With this system, 2006-2007 typhoon cases are processed to compare with the Regional Specialized Meteorological Center (RSMC) - Tokyo Typhoon Center best track and KMA forecasted data as well as the track errors.

Current status of the Terra/MODIS data utilization in KMA: derivation of SST

The direct broadcast Terra/MODIS data has been utilized in Korea Meteorological Administration (KMA) since February 2001. This study introduces utilizations of this data, especially for the derivation of sea surface temperature (SST). For an operational production of the MODIS SST, we have derived a new set of MCSST coefficients by using a simple cloud mask algorithm and by assumption of NOAA daily SST as a true SST. The current NASA’s PFSST and new MCSST algorithms are analyzed by using the collocated buoy observations in the East Asia region. Although the number of collocated data was limited, both algorithms have high correlation with the buoy SST, but somewhat bigger bias and RMS difference than we expected. And PFSST uniformly underestimated the SST. Through more analyzing the archived and future-received data, we plan to derive better MCSST coefficients and apply to MODIS data of Aqua. To use the MODIS cloud mask algorithm to get better SST coefficients is going to be prepared.