碩士 / 臺灣大學 / 大氣科學研究所 / 96 / The decline of downward solar irradiance (DSI) by Cloud and aerosol is one of the important processes on earth climate radiation budget. In this study, we used the measurements of shortwave DSI and cloud (amounts and types) in a highland area with 15 km × 45 km area and 700 m to 2700 m altitude variation at Taiwan, to estimate the monthly and yearly SSCRF through the DSI deviation between clear-sky cases and cloudy-sky cases. The observed cloud amounts at Son-moon-Lake, Ali-shan, Yu-shan weather stations in our research area were studied first. We found there existed several reasonable phenomena including (1) the inverse trend of cloud amounts and weather stations’ altitude, (2) more cloud amounts in summer than in winter, and (3) similar monthly cloud amounts variations among these stations. Furthermore, we also analyzed the correlation between month-average cloud amounts (from observer) and sunshine duration ratio record (from instrument). It showed that the coefficient of negative correlation R is over -0.97 and the linear regressions at these stations are similar to each other. The linear regression slope, which is explained as DSI decline effect of per cloud amount, was smaller in winter than in summer.
In order to build up the baseline of SSCRF (surface solar cloud radiative forcing) computation in this study, twenty-five DSI cases under whole daily clear-sky at Ali-shan station were selected and processed. Then we got the monthly mean SSCRF with a range of -64.7 Wm-2 to -170.4 Wm-2, and the monthly mean SSCRF per cloud amount with a range of -64.7 Wm-2 to -170.4 Wm-2. These results are compatible to the works done by Chou and Zhao (1997) and Gautier and Landsfeld(1997）.
For discussing the hourly DSI variation with cloud amount and cloud types, forty-nine cases of the cloudy-sky days which had the same Julian days to the SSCRF baseline cases were diagnosed. The factors of cloud multi-layer overlapping and environment shade were excluded carefully, and we found the SSCRF of cumulus is about -20.6 Wm-2 to -118.1 Wm-2, the SSCRF of stratocumulus is about -22.2 Wm-2 to -75.3 Wm-2 , and SSCRF of stratus has the magnitude between -28.1 Wm-2 to -94.7 Wm-2.
This study also chose 11 clear-sky cases from the complete DSI operated by NTU experimental forest, to compute the vertical gradient of DSI at noon time. From sixty-six cases, they showed that the 7.5 ％ vertical decrease per 1000 m on DSI agreed with the result 7-10 ％ from Alpine intense observations (Zheng, 1995). The most clean and clear-sky case on March 6, 2005 provided the lowest 2.65 Wm-2 per 100 m, and this amount is close to the observation result at Germany west-southern highland area by Iziomon and Mayer (2002).
| Identifer | oai:union.ndltd.org:TW/096NTU05022001 |
| Date | January 2008 |
| Creators | Lee-Jen Chou, 周立人 |
| Contributors | Po-Hsiung Lin, 林博雄 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 86 |
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