The Spatial and temporal distributions of NET(Net Effective Temperature) with a Function of Temperature, Humidity and Wind Speed in Korea* Inhye Heo**, Youngeun Choi***, and Won-Tae Kwon**** Abstract : This paper examined the possibility of NET application for a relative weather stress index in Korea. The characteristic of NET distribution used temperature, relative humidity, wind speed which forecasting at Korean Meteorological Administration were analyzed. Regional critical values of daily maximum NET of stress index for summer resembled the distribution of daily maximum temperature because were not impacted wind and humidity but temperature. Regional critical values of daily minimum NET of stress index for winter distributed variously compared with summer. The highland region and the northern region of Seoul were impacted of low temperature and coastal region which strong wind. The occurrences of stressful days did not vary in summer, but obviously increased in winter after mid-199s. Key Words : weather stress index, net effective temperature, daily maximum temperature, relative humidity, strong wind (Graduate Student, Department of Geography, Konkuk University) gracehih@konkuk.ac.kr. (Assistant Professor, Department of Geography, Konkuk University). (Director, Climate Research Laboratory, Meteorological Research Institute, Korea Meteorological Administration). 13
Fig. 1. The location of weather stations used for the study 14
Fig. 2. Change of NET as a function of wind speed and temperature for dry conditions (RH=3%) and wet conditions (RH=9%) 15
= Fig. 3. Monthly distribution of absolute daily maximum NET and daily minimum NET in Seoul (1991 ) Fig. 4. The same as Fig. 3 except for Jeju 16
Table 1. Difference of temperature, wind speed and relative humidity between January and February in Seoul and Jeju Temperature( C) Wind speed(m/s) Relative humidity(%) Time Seoul Jeju Time Jan Feb Diff. Jan Feb Diff. 3-3.3-1.7-1.6 5.6 5.4.2 6-4. -2.5-1.5 5.5 5.2.3 9-3.9-1.9-2. 5.8 6. -.2 12 -.4 2.1-2.5 7.1 7.7 -.6 15 1.5 4.1-2.6 7.4 8.2 -.8 18.1 2.9-2.8 6.6 7.3 -.7 21-1.3.9-2.2 6. 6.3 -.3 24-2.5 -.4-2. 5.7 5.8 -.1 3 1.8 2. -.3 4.4 4.3.2 6 1.8 1.8. 4.6 4.4.2 9 2.1 2.2 -.1 4.3 4.1.2 12 2.7 2.9 -.2 4.5 4.7 -.2 15 3.4 3.8 -.4 4.9 5. -.1 18 3.2 3.7 -.5 4.8 4.5.3 21 2.4 2.8 -.3 4.4 4.2.2 24 2.1 2.2 -.2 4.3 4.1.2 3 65.6 65.3.3 68.3 67.8.5 6 68.1 67.7.4 68.4 68.3.1 9 68.1 65.9 2.1 67.7 66.6 1.1 12 52.8 49.5 3.3 63. 61.1 1.9 15 45.1 41.9 3.2 61.9 59.1 2.8 18 5.2 46.4 3.9 63.8 61.4 2.3 21 57.9 56.4 1.5 65.7 65.3.3 24 62.9 61.5 1.5 66.8 67.5 -.7 17
days 25 Seoul Jeju 15 5 6 7 8 9 month Fig. 5. Monthly distribution of the number of days with NET 99% in warm season (1991~) days 3 25 Seoul Jeju 15 5 12 1 2 month Fig. 6. Monthly distribution of the number of days with NET 1% in cold season (1991~) 18
4 Wind chill index - Heat index 3 - -4-3 - - 3 4 5 Daily Min NET Daily Max NET Fig. 7. Correlation of NET with wind-chill index and heat index in Seoul (Left: winter daily minimum NET and wind-chill index, Right: summer daily maximum NET and heat index) 3 4 Wind chill index Heat index 3 - --3 - - 3 4 Daily Min NET Daily Max NET Fig. 8. The same as Fig. 7 except for Jeju 19
days Seoul Jeju 15 5 3 6 9 12 15 18 21 24 Hour of day Fig. 9. Diurnal variations of the occurrences of extreme WSI 97.5% in summer (1991~)
days Seoul Jeju 15 5 3 6 9 12 15 18 21 24 Hour of day Fig.. The same as Fig 9. except for WSI 2.5% in winter (1991~) Fig. 11. Spatial Distribution of daily maximum NET critical value in summer (1991~) 21
Table 2. Difference of temperature, wind speed and humidity of very stressful days in summer at two adjacent cities. ( C) Mean wind speed(m/s) Mean humidity(%) Gangneung 35.6 2.3 48.2 Sokcho 32.7 2.1 63.4 Difference 2.9.2-15.2 Busan 32.8 3.8 61.9 Ulsan 35.2 2.5 51.3 Difference -2.4 1.3.6 Fig. 12. Spatial distribution of daily maximum temperature in summer (1991~) Fig. 13. Spatial distribution of daily minimum NET critical value in winter(1991~) 22
Table 3. Difference of regional temperature, wind speed and humidity of strongly stressful days in winter at two adjacent cities ( C) Mean Temp.( C) Mean wind speed(m/s) Mean humidity(%) Wando -2.7.2 8. Tongyeong -4.4 5.6 47.1 Difference 1.7 4.6 32.9 Wuljin -6.7 6.8 57.6 Pohang -6.4 5.2 45.9 Difference -.3 1.6 11.7 days 5 summer winter sum 4 3 1991 1992 1993 1994 1995 1996 1997 1998 1999 year Fig. 14. Annual variations of the occurrences of extreme WSI for WSI 2.5% in winter and WSI?97.5% in summer 23
days winter 3 year moving average 15 5 1991 1992 1993 1994 1995 1996 1997 1998 1999 year Fig. 15. Trend of the occurrences of extreme WSI 2.5% in winter Table 4. Comparison normal mean temperature with strongly stressful year mean temperature in summer (unit: C) June July August 1994 19.4 26.8 26. Normal (1971~).8 24.4 25.1 Difference -1.4 2.4.9 24
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