【作者】 赵东；

【导师】 罗勇； 祝昌汉； 高歌；

【作者基本信息】 南京信息工程大学 ， 气候系统与全球变化， 2009， 博士

【摘要】 太阳能是地球系统几乎唯一的能量来源,对其长期变化和空间分布的研究历来是气候学研究的重要课题,同时也是可再生能源产业发展的重要前提。本文从1961-2007年中国太阳能长期变化的观测事实出发,结合主要的气象和环境要素,探讨了中国太阳能长期变化的成因,并考虑主要影响因子对辐射传输过程的影响,研制出了完全基于卫星资料的地表太阳能计算模型。主要结果如下:1)中国太阳能的长期变化存在明显的区域性和季节性。近50年来,我国太阳能总体下降趋势显著,其中尤以东、南部地区下降最为明显,同时也表现出较明显的“前期变暗”和“后期变亮”的特点,但其变化存在明显的“区域性”和“季节性”。就区域性而言,“变暗”是普遍的,但“变亮”主要发生在新疆北部、东北北部和南方大部;就季节性而言,“变暗期”四季的变化方向基本一致,只是变化幅度有不同,普遍表现为夏、冬季下降强于春、秋季:“变亮期”四季的变化方向差异较大,不同季节对“变亮”的贡献明显不同,“变亮”主要发生在春、夏季。2)不同地区导致太阳能下降的主要因素有明显差异,在人类活动较剧烈的东部地区,下降主要是由气溶胶的增多所致,表现为轻雾和（或）霾的增加,而在西部地区,则主要是由气候湿润化的大背景所致,表现为低云和水汽的增加。3)通过建立数学模型,将云对太阳能变化的作用从众多因素中分离出来,考察了云和环境因素对太阳能长期变化的作用差异。结果表明,云量和环境因素对中国太阳能的变化均有重要作用,但有明显的区域性和阶段性差异。环境因素对阳光削弱作用的增强（气溶胶增多,环境恶化）是绝大部分地区地表太阳能下降的共有原因,其中对于新疆和东南地区而言,“有效云量”的增加对此作用也较大（贡献率约为13%-35%）。自20世纪90年代初起,大部分地区太阳能的下降基本停止,一些地区甚至略有回升,但成因不尽相同:北疆和云南的回升主要缘于环境的好转（贡献率100%）:中南地区及四川盆地的回升主要缘于有效云量的减少（贡献率100%）:东北北部和东南地区的回升则是环境好转和有效云量减少共同作用的结果,且环境好转的贡献较大（对两个区域的贡献率分别达60%和80%）;南疆和西北地区东部下降趋势的减缓也主要是环境好转的结果。受“有效云量”增加的影响,西北地区中部、东北大部及华北平原的太阳能依然呈明显的下降趋势,其中对于华北平原而言,环境的持续恶化也是重要原因（贡献15.9%）。“夏、冬季下降强于春、秋季”是我国太阳能下降的普遍特点,这主要是由云量变化方向和变化强度的季节性差异导致。通过云的变化和环境因素的变化可以较好地解释中国太阳能的变化。4)通过能够引起光学视程障碍的天气现象日数分析了不同地区导致太阳能变化的主导环境因素。西部地区的环境状况表现为“前期恶化,后期好转”,且环境的恶化/好转均与烟幕和沙尘的增加/减少密切相关。轻雾和（或）霾是东、南部地区环境恶化的主导因子,且这些因子作用表现为持续的增强,因此环境状况并无好转。在地表太阳能计算中,必须考虑环境因素的作用。5)太阳能的变化伴随着辐射成分的变化。“变暗期”,直接辐射所占的比例减少;“变亮期”,直接辐射所占的比例也开始增加。6)对比介绍了主流太阳能计算模型,应用目前使用最广泛的日照百分率模型对中国的太阳能资源做了评估,并指出了发展新模型的必要性。结果表明,“高原大于平原,西部干旱区大于东部湿润区”是我国太阳能资源分布的基本态势,“强处更强,愈强愈稳”是资源时空变化的主要特征。与欧洲的太阳能利用发达的国家相比,中国的太阳能资源非常丰富,太阳能最少的四川盆地与欧洲一些国家相比,总辐射资源量并不逊色,未来在太阳能开发利用方面存在很大潜力。直射比的分布与太阳能资源本身的分布较为一致,在海拔较高或较干燥的地区,太阳辐射以直接辐射为主,在较湿润地区,以散射辐射为主,在开发利用太阳能时必须要考虑资源的辐射成分特点。实践证明,经验模型使用方便,在地形平坦、大气环境状况较单一的地区精度很高,但由于完全依赖于地面观测,在地形较复杂、或者大气环境状况区域性较强的地区,计算结果存在较大的不确定性,因此,有必要综合考虑地形、云及大气环境状况对辐射传输过程的影响发展新的计算模型,并指出卫星资料应用的必要性。7)借助Bird晴天辐射计算模型,以卫星探测的大气环境资料为输入,计算了晴天地表太阳辐射,数值实验结果表明,受地形和大气环境因素的作用,晴天太阳辐射的空间分布在很大程度上偏离了纬向分布,其中,以气溶胶的作用最为显著。8)应用卫星资料,考虑大气中各主要因素对辐射传输过程的影响,建立了新的地表太阳能计算模型,为解决中国地面太阳能数据的空间连续性问题提供了有效的手段。新模型对直接辐射、散射辐射和总辐射历年逐月值计算的平均相对误差（MAPE）分别为22.1%、18.3%和11.6%,均方根误差（RMSE）分别为13.20kWh.m^-2、12.85 kWh.m^-2和16.39 kWh.m^-2。计算结果可以较好地反映出天文、地理、气象和环境要素对地表太阳能分布的作用。该方法物理意义明显,输入资料获取方便,且计算效果较好,有利于实际应用和推广。绘制了中国太阳辐射各分量2005-2007年平均的年及四季的分布图。更多还原

【Abstract】 Solar energy is almost the unique energy source of the earth system,its long-term change and spatial distribution have always been the most important research subject of climatology, and also been the most important precondition for the development of renewable energy industry.Based on ground observed data sets of solar radiation,sunshine duration and related meteorological and environmental factors of China,this doctoral dissertation discussed the causes of the long-term change of solar energy deeply and systematically.Further more,a series of models for computing solar radiation arriving at earth surface were established by using satellite data,in which,the effect of cardinal meteorological and environmental factors on radiative transfer process were considered.The main achievements of this project were concluded as follows:1.In recent 50 years,the time series of solar energy over China exhibits obvious decreasing trend and with significant characters of ’dimming in prior period and brightening in later period’,but the change has apparent regional and seasonal features.On regional basis, the dimming is universal all over the country,especially in Eastern and Southern parts,but the brightening only occurred in some certain areas,namely North Xinjiang,North Area of Northeast China and most parts of Southern China.On seasonal basis,the decrease trend occurred almost in all seasons only with difference in change rate during dimming period, but the brightening only presented in some certain seasons,mainly in spring and summer, that is to say.different season has different contribution to the brightening in later period.2.Factors that lead to the decrease of solar energy are notably discrepant in different regions.Speaking generally,in east part wherein the human activity is more drastic,the decrease trend is mainly induced by the increase of aerosol particles,which primarily presented as the increase of haze and mist days.In west part,however,the decrease trend occurred mainly because the climate changes from dry to wet,which primarily presented as the increase of low cloud amount and water vapor.3.By establishing mathematical models,the impact of cloud and environmental factors upon the solar energy change is detected separately,wherefrom the different effects of the two types of factors were discussed.The result recommend that,both the cloud and environmental factors have important impacts on long-term solar energy change,but the dominant factor varies with the region in space and the stage in time domain.The enhancement of weakening effect of environmental factors on solar radiation（i.e., environmental deterioration） is the mutual reason that causes the decrease of solar energy in most areas,besides,the decreasing of effective cloud fraction is also a crucial cause for Xinjiang and southeast China（the contribution rate is about 13%-35%）.From early 1990’s, the decline trend ceased in most regions,even followed by a sight increase in some certain areas,but the causes are not the same.For the regions of North Xinjiang,and Yunnan,the brightening is mainly induced by the improvement of environmental quality（the contribution rate is about 100%）.For Central South China and Sichuan Basin,the decrease of effective cloud fraction is the dominant reason（the contribution rate is about I00%）.For North Area of Northeast China and Southeast China,the brightening is resulted from the combined impact of environmental factors and effective cloud fraction,and the former is more important（the contribution rate is about 60%and 80%for the two regions,respectively）. However,due to the influence of the increase of effective cloud fraction,the solar energy still shows remarkable declining trend in North China Plain,central part of Northwest China and most part of Northeast China,among which,continuous deterioration of environment also plays a certain role in North China Plain（the contribution rate is about 15.9%）.Furthermore, there exists a prominent and widespread signature that the descending rate of solar energy is faster in summer and winter than that in spring and autumn,and the study indicate that the feature hereof is ascribed mostly to the change of cloud.In one word,the long-term change of solar energy（i.e.,dimming,brightening） in China can be explained fairly well by means of cloud cover and environmental factors.4.By expressing environmental factors as various weather phenomenons which can lead to obstruction to vision,the dominate environmental factors were confirmed.The study comes to the results as follows:In West China,the environment status presents a feature of ’getting worse in prior period and getting better in later period’,and the deterioration （improvement） is closely related to the increase（decrease） of smokescreen and sand-dust weather days.Whereas in East China,the environment quality changes with little improvement for the sustaining increase of mist days and（or） haze days,the results hereof also suggest that the effect of environmental factors should have been considered in computing solar energy arriving at the earth surface.5.Change of Solar energy usually accompanies corresponding change of radiation components,i.e.,the proportion of direct radiation decreases in dimming stage and increases in brightening stage.6.Various current mainstream solar radiation models are simply recommended contrastively,on the basis of which,an assessment of solar energy over China was conducted based on dataset of monthly radiation and sunshine duration from 1961 to 2007 by means of most commonly used sunshine based models.The results recommend that:solar energy resource over plateau and west arid regions is richer than which over plain and east humid regions,and the energy is more stable over resource-richer places on the basis of annual change.The national averaged time series of solar direct and global radiation retrieved from sunshine duration showed an obvious decreasing trend from 1960s to 1980s,and at the begging of 1990s,the decline ceased,followed by a slight increase to some extent.The resources have been continuously getting stronger over some certain areas of energy-rich part during the past several decades.Compared with some European countries where the solar energy industry is well developed,China presents innate advantages of solar energy, even for Sichuan Basin.The distribution of the proportion of direct radiation is similar with resource itself,in high-elevation areas or dry areas,direct radiation is the predominant composition,whereas diffuse radiation is main composition in low-elevation areas or wet areas,this property should be considered in solar energy industry development.The practice has proved that even though the empirical models can easily turn sunshine duration to radiation by simple regression,but it requires the existence of radiation and sunshine duration data in the first place to produce the prediction equation,and the uncertainty increases with a distance between the location of interest and the measuring stations, especially in mountainous regions or areas with atmospheric environment changing violently in space.In view of this,it is necessary to take topography,meteorological and environmental factors into account.In order to achieve this goal,we propose an optimized calculation scheme on the basis of satellite data.7.By virtue of Bird Clear Sky Model,with the input of environmental factors detected by satellites,the solar radiation under clear sky is computed,the output from which indicates that the distribution of solar radiation is different from zonal distribution to a great extent in general cases due to the effects of atmospheric factors,among which aerosol is the most important one.8.A series of mathematical models for computing solar radiation arriving at the earth surface are established by using satellite data,in which,the effect of cardinal meteorological and environmental factors are considered.The MAPE（RMSE） value of direct radiation model,diffuse radiation model and global radiation model is 22.1%(13.20kWh.m^-2),18.3% (12.85 kWh.m^-2) and 11.6%(16.39 kWh.m^-2),separately.The calculated solar energy can reflect the influence of astronomical factors,geographical factors,meteorological factors and environmental factors fairly well.Utilizing satellite data absolutely and by means of the new models established above,the annual and seasonal value of solar radiation is mapped for China,which provides an effective method for solving the discontinuity problems of solar radiation data.更多还原