| Excessive dose of solar UV radiation can cause erythema on human skin,severe cases can even cause skin cancers.The solar UV radiation that can cause the human skin erythema phenomenon is called solar erythemal UV radiation,which is a physical quantity obtained by coupling solar UV radiation and solar erythema action spectrum.In this paper,the solar ultraviolet spectra of Nyingchi,Lhasa,Xigaze and Tingri in Tibet have been observed in situ for 12 years,and the solar ultraviolet spectra of Nyingchi,Lhasa,Xigaze and Ali have been observed in situ.Based on these measured data,the paper systematically analyzed the variation of ultraviolet radiation of solar erythema on the ground in four regions of Tibet(Nyingchi,Lhasa,Xigaze and Tingri),and summarized the temporal and spatial distribution characteristics of ultraviolet radiation of solar erythema on the ground in Tibet.This is the first time for the world to observe and study the solar erythemal UV on the ground of Tibet in such a large scope and for a long time.In this paper,the daily variation,annual variation and sunny day characteristics of solar erythema in Tibet are analyzed and studied.It can be summarized as follows:the variation of the solar erythemal UV on the ground of Tibet presents a parabola shape with the time of the day,and reaches the highest value around noon.The height of the curve changed with the month of the year,and it was the highest in summer and the lowest in winter.On absolutely cloudless days,the parabola changes evenly and smoothly,and once clouds appear above the detector,the curve will show significant fluctuations.Therefore,the smoothness of the curve of the solar erythemal UV on the ground can be used as a direct basis to judge the weather of the day.Under sunny conditions,the average daily total dose of solar erythemal UV on the ground in the four regions was 2184J/m~2 in Nyingchi,2943J/m~2 in Lhasa,3852J/m~2 in Xigaze,and3949J/m~2 in Tingri.Thus,it is determined that among the four regions in Tibet,the intensity of solar erythemal UV on the ground at Tingri is the highest,followed by Xigaze,Lhasa,and Nyingchi.In addition,this paper analyzed the surface solar spectrum and the surface solar erythera ultraviolet radiation of the rare high temperature in Lhasa on that day,and found that the highest temperature in history was June 24,2019,there was indeed solar erythemal UV on the ground radiation intensity,and the surface solar spectral intensity increased.Due to the two days of different weather conditions(cloudy and sunny),the specific increase rate is not clear.Secondly,the paper provides a global perspective for the study of the temporal and spatial variation of the solar erythemal UV on the ground of Tibet by analyzing the daily total dose of the solar erythemal UV on the ground in four regions of Tibet,and reflects the overall situation of ultraviolet radiation in the local solar erythema UV.The results showed that the variation trend of the solar erythemal UV on the ground dose of ground solar erythera in Nyingchi and Tingri was the most stable,and almost no maximum value appeared,indicating that Nyingchi and Tingri were the most stable areas of ground solar erythera UV in Tibet.In Lhasa,the maximum value appeared from2008 to 2014.Xigaze has the most obvious image disturbance and is the most unstable area.Over the entire observation period,the daily total dose of the solar erythemal UV on the ground in Nyingchi decreased slightly after 2014(compared to 2009-2012).It is proved that in recent years,the intensity of solar erythemal UV on the ground in Nyingchi area has decreased,and the ecological environment in this area has become more and more livable.The average daily total dose range of ground solar erythera UV in four regions was:Nyingchi1000-5000J/m~2,Lhasa 1000-8000J/m~2,Xigaze 100000J/m~2,Tingri 2000-10000J/m~2.During the observation period,the maximum daily surface solar erythea UV dose was 7185J/m~2 in Nyingchi,14260J/m~2 in Lhasa,and17050J/m~2 in Xigaze,and 11190J/m~2 in Tingri.The intensity of solar erythema UV represents the damage degree of the sun's ultraviolet to human skin,and the maximum dose rate reflects the maximum damage degree.Therefore,this paper studies the maximum daily dose rate of solar erythema UV on the ground,which is directly related to our skin protection and avoiding the maximum damage caused by the sun's UV.The results showed that the variation trend of the daily maximum dose rate of the solar erythema UV was still a parabola with the change of seasons,and reached the maximum value in June and July,and the lowest value in January and December of the same year.The maximum dose rate of Nyingchi has decreased since 2014(compared to 2009-2012),which also proves the superiority of Nyingchi in natural environment.The daily maximum dose rate of the solar erythemal UV on the ground in Lhasa was relatively stable from 2008 to 2020,except for some maximum values in 2013and 2014,which are the most dangerous years for human skin.The average range of the maximum daily dose rate of ground solar erythera UV in the four regions was as follows:Nyingchi 100-350m W/m~2,Lhasa 100-400m W/m~2,Xigaze 100-400m W/m~2,Tingri-100m W/m~2.During the observation period,the maximum daily dose rate of solar erythea UV was 456.5m W/m~2 in Nyingchi,687.5m W/m~2 in Lhasa,962m W/m~2 in Xigaze,and 1218m W/m~2 in Tingri.The ultraviolet index is the most direct and widely understood way to reflect the damage degree of the sun's ultraviolet to human skin,so the paper analyzes the average range of the maximum UV index in four regions:Nyingchi 4-14,Lhasa 5-18,Xigaze 5-18 and Tingri 6-21.According to the World Health Organization(WHO),the UV index above 11 is super high,so we can conclude that Tibet is indeed a region with super high UV radiation.We suggest that skin protection should be done well in any weather.Finally,the influencing factors of solar erythema UV on the ground are analyzed,which are mainly cloud and ozone concentration.In terms of the impact of clouds on the solar erythemal UV on the ground,through the study of the solar erythemal UV on the ground on January 8 and 9,2016 and April 3 and 4,2018 in Lhasa,,determine the solar erythemal UV on the ground and sensitive correlation between clouds,specific to the clouds on the solar erythemal UV on the ground exists weakness and strengthen two kinds of effects.In the examples listed in this paper,the attenuation rate is up to 90% and the enhancement rate is up to 15%.So on cloudy days,perhaps the solar erythemal UV on the ground is stronger and more dangerous to human skin.By analyzing the variation of ozone concentration in Lhasa,it can be concluded that ozone concentration is the highest in spring. |
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