Knowledge Resource Center for Ecological Environment in Arid Area
| 近年来中国地表太阳辐射时空变化及影响因素分析 | |
| 其他题名 | Analysis of Spatio-temporal Variation of Surface Downward Shortwave Radiation and Associated Effecting Factors over China in Recent Years |
| 吕宁 | |
| 出版年 | 2009 |
| 学位类型 | 博士 |
| 导师 | 刘纪远 ; 刘荣高 |
| 学位授予单位 | 中国科学院地理科学与资源研究所 |
| 中文摘要 | 地表太阳辐射是气候研究中的重要组成部分，它影响着大气圈、水圈和陆地圈层中的物质与能量交换，如碳循环、营养物质循环、水循环和热循环等。近几年，人们利用地面观测和卫星资料发现，自20世纪60年代到80年代末，各地区到达地面的太阳辐射普遍呈减少趋势（称之为变暗）。但从1990年前后开始，这种趋势在世界大多数地区发生了逆转，即到达地面的太阳辐射普遍开始增加（称之为变亮）。越来越多的研究结果表明地表太阳辐射不仅具有局地性，而且其原因也可能是很复杂的，云和气溶胶等因素的影响作用可能也是具有区域性的。中国现在面临全球变暖、平均气温距平变化与蒸发皿蒸发量变化趋势之间的不协调、中国地区平均云总量减少等问题，在这种气候变化的背景下，弄清中国地区地表太阳辐射能量究竟发生了什么样的变化，云或气溶胶究竟哪种因素在该变化中起主导作用等问题对于研究区域和全球气候变化具有重要的意义。\n中国观测太阳辐射的地面站点有限且分布不均匀，利用卫星遥感反演可以获得连续空间分布的地表太阳辐射信息。本文以GMS-5（Geostationary Meteorological Satellite）静止气象卫星为输入项，根据辐射传输理论和查找表法，引入大气水汽含量和地表高度参量来反演瞬时和每日的地表太阳辐射；在使用地面观测数据对反演数据精度充分验证的基础上，总结了中国地表太阳辐射在不同时段（月、季、年）、不同区域上的变化规律，阐明了1997～2003年期间中国地表太阳辐射变化的格局和过程；从云和气溶胶的短波辐射强迫入手，分别分析了云、气溶胶在地表太阳辐射变化的各个时期中的作用，通过能量闭合试验研究了近年来云和气溶胶在地表太阳辐射变化中究竟是如何影响地表太阳辐射的，谁在其中起主导作用。本文得到以下主要结论：\n1、静止气象卫星在大城市区域反演的地表太阳辐射普遍偏高于地面观测值，这种偏差很可能是由吸收性气溶胶造成的。敏感性试验表明水汽对到达地表的短波太阳辐射有着较强的吸收作用，而臭氧的影响则很小。地表太阳辐射的卫星反演对于辐射传输模型中设定的气溶胶类型非常敏感，对云类型的变化则不太敏感。高的地表反射率会增加地表太阳辐射的反演误差（ [6%~9%]）。NECP/NCAR再分析资料中的地表太阳辐射值整体偏高，特别是高原地区的地表太阳辐射明显高于卫星反演的地表太阳辐射，这可能是因为再分析资料在同化过程中过高估计了地表高程的影响。\n2、中国区域地表太阳辐射就全国范围来看，地表太阳辐射最大值出现在青藏高原，最小值出现在川黔地区，高值中心和低值中心都处于北纬22°～35°这一带。青藏高原地表太阳辐射高与其喜马拉雅山、昆仑山、巴颜喀拉山和唐古拉山等巨型山系阻挡暖湿气流，云量稀少，降水少，水汽含量低，大气透明度高等因素有关；四川盆地地表太阳辐射低与其地形封闭，又处在南北两股暖冷气流交汇处，阴霾天多造成大气低透明度，水汽难以输出，空气中污染气体也难以输出等因素有关。地表太阳辐射的年变幅主要与纬度有关，越向高纬变幅越明显。月际间地表太阳辐射分布更复杂，最大值出现时间受雨季影响很大，珠江、长江一带在主要雨季过后的7月,华北、东北分别在雨季前的6月及5月，西南地区则在季风雨季前的4～5月。年际间和季节间的地表太阳辐射变化较为规律，春天和夏天的时候地表太阳辐射值大，冬天最低。这种情况是由日长的年度周期和太阳高度角的变化造成的。夏季南部区的地表太阳辐射比北部区要小，这与南部区夏季云雨天气多、湿度大有关。东部沿海地区地表太阳辐射增加了8.65%（13.33W/m2），西藏高原地区地表太阳辐射减少了5.46%（11.22 W/m2），中国区域地表太阳辐射平均减少了0.87%（1.41 W/m2）。\n3）就全国而言，川黔地区的云辐射强迫最强，其次是长江中下游地区和青藏高原地区，华北地区较次，高原北侧的西北干旱区云辐射强迫最弱。在青藏高原东南部的孟加拉多云地区，短波云辐射强迫强烈，而高原北侧的柴达木盆地为明显低值区。云辐射强迫的这些区域特征与全国总云量和高原总云量的分布形式是一致的。东南沿海地区、四川中东部和柴达木盆地的云短波辐射强迫有逐年减少的趋势，而青藏高原西南部的云短波辐射强迫在逐年增强。云辐射强迫在中国有着明显的季节差异，春夏云辐射强迫作用强，秋冬云辐射强迫作用弱。北方区域的云辐射强迫通常较小，南方区域的云辐射强迫通常较大。在青藏高原的西南地区，存在着云辐射强迫增强且总云量增加的现象，这可能主要是因为高原西南地区受西南季风的影响增加了夏季的总云量。\n4）气溶胶直接辐射强迫区域分布格局与气溶胶的分布和来源有很密切的关系。南海气溶胶辐射强迫受海盐气溶胶影响，西北地区气溶胶辐射强迫与剧烈沙暴区活动有关，渤海湾地区的气溶胶辐射强迫则与京津地区的污染气体排放并输送到此的人类气溶胶密切关联。全国范围内，秋冬季节气溶胶辐射强迫略高于春夏。北方地区气溶胶直接辐射强迫春季最高、夏秋冬依次减弱，这说明北方地区气溶胶直接辐射强迫主要受春季的沙尘控制。高原区气溶胶直接辐射强迫在冬季最大，春秋季次之，夏季最小，存在明显的季节性震荡，这可能是由于对流层顶季节性抬升造成的。2001年、2002年各个区域的气溶胶辐射强迫都是个相对峰值，说明这期间频发的沙尘天气放大了沙尘气溶胶的辐射强迫。\n5）1997～2003年期间中国地表太阳辐射的减少主要是受到气溶胶辐射强迫增加和云辐射强迫减少的双重作用。气溶胶辐射强迫增加为负向反馈，减少了地表太阳辐射，云辐射强迫减少为正向反馈，增加了地表太阳辐射。但是由于2001和2002年频繁的沙尘暴放大了自然来源气溶胶的辐射效应，气溶胶辐射强迫变率超过了云辐射强迫变率的影响，使得总辐射强迫在逐渐增加，因此中国地表太阳辐射在逐渐减少。 |
| 英文摘要 | Shortwave solar radiation at the earth’s surface is of primary interest in climate research because it controls the total material and energy exchange between the atmosphere and the land/ocean surface, such as cycling of carbon, nutrient, hydrological and heat. In recent years from surface observational records and satellite observations, people find that a widespread decline trend in solar radiation at land surfaces has become apparent in many regions from 1960s up to 1990 (know as dimming), while a reverse trend has been observed in most places of the world since 1990s, which means solar radiation at surface begin to increase (known as brightening). A growing body of studies shows that not only the variation of surface downward shortwave radiation is localized, but its effecting factors are complicated. Among all factors, the dominant factors of cloud and aerosol may have the same regional feature. At present China is facing the problems from global warming, the unmatched changing trends between average temperature anomaly and pan evaporation, and the decreasing total cloudiness over China. In such a context of climate change, it is of great significance for regional and global climate change research to identify what kind of changing pattern appears over China, either cloud or aerosol is in the leading role of the changing. \nThe number of surface observational stations in China is quite finite and unevenly distributed. Alternatively, surface solar radiation can be retrieved from satellite with continuous spatial spread information. The main contents of this paper are: 1) presenting an operational scheme using radiative transfer model and lookup table approach that includes the water vapor absorption and surface altitude variation, to estimates diurnal variation of surface reaching shortwave flux and daily DSR over China from space using the GMS 5 visible band satellite data; 2) fully validating the accuracy of GMS-5 estimated daily DSR with ground-observations; 3) summarizing the variation rules of DSR over China presenting in different periods (monthly, seasonally, annually) and regions, illustrating the DSR changing pattern and course over China during the period from 1997 to 2003; 4) analyzing the roles of cloud and aerosol individually in each DSR changing period with radiative forcing of their own; 5) investigating how the cloud and/or aerosol impact DSR in recent years and which one plays the leading part through the radiation energy closure experiment. \nThe main conclusions of this paper are as follows:\n\t1. DSR estimated from GMS-5 over large cities is generally higher than ground-observed value. The positive errors over large cities can be attributed to aerosols with absorptive properties. Experiments in this study have demonstrated that column water vapor amount has a strong absorption impact on incident shortwave flux at the surface while the impact of ozone is quite small. The magnitude of downward flux variation will rise up to about 6% with one unit changes in water vapor amount. Clouds and water vapor amount have significant effects on DSR in addition to those from the surface elevation and sun-view geometry. DSR estimation is more sensitive to the selection of the aerosol types, but less to that of the cloud types. Uncertainty of bright surface reflectance leads to considerable DSR retrieval bias. The comparison with NCEP/NCAR 1 reanalysis DSR data shows that NCEP/NCAR reanalysis data may overestimate the daily DSR over the land because of surface height effect.\n2. From East to West DSR spatial distribution, DSR normally increases from East to West except Szechwan and Guizhou region. From South to North perspective, DSR in West region decreases with increasing latitude, while Yangtze River basin in East part has the lowest DSR; DSR increases from South to North, the maximum DSR is in North China, the second place in South China, DSR decreases till Northeast China. On the Nationwide, the maximum DSR is on Tibetan Plateau, the minimum value is over the Szechwan Basin. Both the extreme values are located on the belt between N22° to N35°. The annual variability of DSR mainly depends on latitude, the higher latitude is to, the larger varied value shows. The distribution of monthly DSR is more complicated, minimum DSR mostly occur in December, the maximum in the period of June to July which is controlled by the rainy season. DSR is big in spring and summer and low in winter. That is attributed to the annual cycle of daytime and variation of solar zenith angle. In addition, lower atmospheric transmittance magnifies the changes. During summer, DSR over Southern China is less than that of Northern China because of frequent cloud weather and high humidity. Absorption and reflection of solar radiation from the cloud and water vapor in the air significantly reduce the DSR reaching at surface.\n3. The strongest Cloud Radiative Forcing (CRF) appears over Szechwan and Guizhou region. The middle and lower reaches of Yangtze River and Tibetan Plateau take the second place. The minimum CRF is over arid areas in Northwestern China by the north side of Plateau. Tsaidam Basin is a significant low CRF region. These regional features of CRF are consisting with the spatial distribution of total cloud from Nationwide and Plateau. CRF over Southeastern coastal areas, central and east of Szechwan Basin and Tsaidam Basin has decreasing trend, while CRF over Southwestern Plateau increasing. There is a apparently CRF seasonal differences over China. CRF in spring and summer is strong, while weak in autumn and winter. Usually CRF over Northern China is low, but high in Southern China. Around the southwestern part of Tibetan Plateau, CRF increases meanwhile total cloud increases too. This phenomenon probably can be explained by summer southwest monsoon that increase the total cloud amount over Plateau.\n4. Spatial pattern of Aerosol direct radiative forcing (ARF) has a close relationship with aerosol distribution and its source: ARF over South China Sea is affected by sea salt aerosols; ARF over Northwestern region is related to severe sand storm; ARF over Bohai Sea Gulf region is attributed to the anthropogenic aerosols from pollutions emitted by the highly industrial cities of Beijing and Tianjin. On the Nationwide, ARF in autumn and winter is higher than spring and summer. The spring ARF in Northern China is the highest which may suggest that ARF over Northern China mainly dominated by dust and sand weather in spring. The ARF in Tibetan Plateau is maximum in winter, spring and autumn in sequence and minimum in summer. This clearly seasonal fluctuation may be caused by seasonal uplift of tropopause. The ARF in 2001 and 2002 over each region is a relative peak value which may imply that the frequent sand storms in those two years have strongly influeced DSR all over China.\n5. The reduction of DSR in the period from 1997 to 2003 is mainly forced by both the increment of ARF and decrement of CRF. Negative feedback from ARF increment decreases DSR, while positive feedback from CRF decrement increases DSR. The frequent sand storm in 2001 and 2002 magnify the radiative effects of natural aerosols. Because the variability of ARF exceeds the impact of CRF variability, total radiative forcing is increasing. Therefore, the DSR over China is decreasing. |
| 中文关键词 | 卫星遥感 ; 地表太阳辐射 ; 云 ; 气溶胶 ; 辐射强迫 |
| 英文关键词 | Satellite Remote Sensing Downward Shortwave Radiation Cloud Aerosol Radiative Forcing |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 地图学与地理信息系统 |
| 来源机构 | 中国科学院地理科学与资源研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/286741 |
| 推荐引用方式 GB/T 7714 | 吕宁. 近年来中国地表太阳辐射时空变化及影响因素分析[D]. 中国科学院地理科学与资源研究所,2009. |
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