西藏日食太阳辐射观测研究

日食现象会对地球太阳辐射、大气气象以及人类活动等造成相应的影响。2020年6月21日（夏至）在西藏发生了一次日食现象，西藏阿里日环食最大食分达到了0.995，拉萨地区日偏食食分也高达0.953。两地日食均发生在当地正午前后。本研究利用罕见的日食出现机会，对西藏阿里和拉萨日食过程中的太阳光谱、太阳总辐射和太阳紫外线变化特征进行了同步观测研究。观测表明阿里日环食在当地正午（北京时间14:41分）前后持续了约3小时27分钟；拉萨日食出现时间比阿里滞后约26 min，持续时间比阿里短3分28秒。实地观测表明在日食期间，阿里光谱观测中最强单色（476.6 nm）光峰值从初亏（13:01分）时刻的1 669.234 mW·m-2·nm-1陡然衰减到食甚（14:44分）时刻的61.936 mW·m-2·nm-1，损失约96.0%；相应时刻太阳总辐射强度从1 221.217 W·m-2衰减到56.086 W·m-2，也损失约95.4%。拉萨日食期间最强单色（476.6 nm）光峰值从初亏（13:27分）时刻的1 563.876 mW·m-2·nm-1亏损到食甚（15:13分）时刻的26.391 mW·m-2·nm-1，亏损约98.3%；相应时刻太阳总辐射强度从1 605.663 W·m-2衰减到28.169 W·m-2，也亏损约98.2%。观测研究发现拉萨太阳紫外线B剂量率从初亏的60.8 W·m-2减弱到食甚的0.9 W·m-2值，减弱了98.5%。该次日食对西藏地面各种太阳辐射强度造成95%以上能量损失。

Solar Radiation Observation During a Solar Eclipse in Tibet

Solar eclipses cause corresponding impacts on the earth’s solar radiation, meteorology and human activities. A Solar eclipse occurred on June 21(summer solstice), 2020, in Tibet, the maximum magnitude of the annular eclipse was reached 0.995 in Ngari, and the maximum magnitude of 0.953 for the partial eclipse in Lhasa, Tibet. The eclipses for both locations occurred around the local noons. We, by taking the rare opportunity for appearing the solar eclipse, observed the solar spectra, global solar irradiance and solar UV radiation measured by the RAMSES solar spectrometers made in Germany, the CMP11global solar radiometers by Holland and the NILU-UV solar ultraviolet detectors made in Norway, respectively during the solar eclipse in Tibet. The observations show that the annular eclipse lasted about 3 hours 27 minutes. Around the local noon (Beijing time 14:41) in Ngari. The eclipse in Lhasa was 26 minutes behind Ngari and lasted about 3 minutes and 28 seconds shorter than Ngari. The observation showed that the peak value of strongest monochromatic (476.6 nm) light for Ngari’s spectra decreased sharply from 1 669.234 mW·m-2·nm-1 at the first contact phase (13:01 min) to 61.936 mW·m-2·nm-1 at the maximum phase (14:44 min), with a loss of about 96.0%. Simultaneously, the global solar irradiance decreased from 1 221.217 to 56.086 W·m-2, and the loss was about 95.4% for Ngari. The peak value of the strongest monochromatic (476.6 nm) light during the solar eclipse in Lhasa decreased from 1 563.876 mW·m-2·nm-1 at the first contact phase (13:27) to 26.391 mW·m-2·nm-1 at the maximum phase of the eclipse (15:13), the deficit was about 98.3%, the global solar irradiance decreased from 1 605.663 to 28.169 W·m-2 for the above corresponding time, and the net loss was about 98.2% too. We observed that the dose rates for solar UVB in Lhasa were also decreased about 98.5% for the value of 60.8 W·m-2 at the first contact phase to 0.9 W·m-2 at the maximum phase of the eclipse. The current solar eclipse caused more than 95% energy loss to Tibet’s surface solar radiation intensity.