한국 전역의 지표 홍반 자외선 복사의 계절기후

Abstract

We have examined monthly and seasonal means of clear-sky noon and daily erythemal ultraviolet-B(EUV-B, 280-320 nm) (1994-2000), and UV-A(320-400 nm) irradiance (1996-1998) measured at Yonsei University, Seoul (37.57oN, 126.98oE), with UV-A and B-Biometers (Solar Light Model 501). The erythemally weighted daily UV exposure(EUV, 280-400 nm) data(1979-1999) estimated using stratospheric ozone amounts and reflectivity measured from Nimbus-7 and Earth Probe/TOMS(Total Ozone Mapping Spectrometer) are also analyzed to investigate seasonal and regional characteristics over the Korean Peninsula. Monthly mean diurnal variation of clear-sky EUV-B irradiance at Seoul shows a peak of 179.8 mWm-2 around local noon in August. Annual mean value of daily EUV-B irradiance is 1.6kJm-2 with a maximum(2.7 kJm-2) in June and a minimum(0.5 kJm-2) in December. And the annual mean UV-A is 153.4 kJm-2 with maximum of 226.1 kJm-2 in May and minimum 71.2 kJm-2 in December. During this measurement period, extreme values are recorded with 308.7 mWm-2(13 July 1994) for clear-sky noon, 6.2 kJm-2(13 July 1994) for daily EUV-B and 378.6 kJm-2(17 July 1998) for daily UV-A. We have also noted that annual mean EUV-B irradiance appears 1% of the UV-A value with monthly variations ranging from 0.6%(January) to 1.3%(June～August). It is found from the ratios that the UV-B is only weakly sensitive to cloud changes compared to EUV-A. All over the Korean Peninsula, all-sky daily EUV-B irradiance is distributed from 4.4 to 3.6kJm-2 in summer and the value is relatively high (around 4.0 kJm-2) along the west and south coastal zones but low (about 2.4 kJm-2) in the land area. Such distributions are attributed by the solar zenith angle (SZA), cloudiness, and total ozone. The daily EUV-B isolines are in the ranges from 4.4 to 3.6kJm-2 in spring and from 2.4 to 1.5kJm-2 in autumn, and they are almost paralleled with latitudes. These distributions are mainly caused by the stronger influence of SZA than those of other factors. In winter the EUV-B ranges from 1.1kJm-2 to 0.7kJm-2 over the whole area. The gradient of the isoline with lattitude is the lowest of the seasons. The ratios of clear-sky noon time EUV-B, daily EUV-B and UV-A to TOMS-EUV are also analyzed for their estimates all over Korean Peninsula. And comparison of erythemally weighted UV irradiance and unweighted value have been performed to estimate unweighted UV irradiance. Such information will be very important to evaluate the UV index for prevention of skin cancer and ecosystem damages, and to understand UV climatology over Korea.