Latent and Sensible Energy Flux Over Deforested Land Surfaces in the Eastern Amazon and Northern Thailand

Land cover change may impact watershed hydrology and regional climate by altering land-atmosphere exchanges of energy and water. Conversion of forest to pasture has previously been shown to decrease the rate of evaporation (including transpiration) because of reduced aerodynamic roughness, less canopy rainfall interception and greater canopy resistance during dry periods. However, less is known about the effects of forest replacement land covers other than pasture. In this study, field measurements of meteorological processes, stomatal resistance, and Leaf Area Index (LAI) were taken over various deforested land surfaces in the eastern Amazon Basin and in northern Thailand. Based on these measurements, evaporation and sensible heat flux were estimated over each site. Results show the degree to which different land covers replacing tropical forest affect energy partitioning. In comparison with forest, non-irrigated, actively and recently cultivated sites had sharply lower rates of evaporation. Secondary vegetation generally had higher rates of evaporation than actively or recently used sites. The proportion of energy used for evaporation increased rapidly with age in secondary vegetation. Evaporation rates at sites eight and 25 years after abandonment in the Thailand study area were enhanced by positive sensible energy advection from nearby cultivated areas, and were similar to those of primary forest. Differences in dry season evaporation rates of 3-, 8- and 25-year secondary vegetation are explained, in part, by the differences in canopy resistance. Minimum canopy resistance was 223, 61 and 58 s m ⁻¹ , respectively at the 3-, 8- and 25-year sites.     

绿洲荒漠过渡带夏季晴天地表辐射和能量平衡及小气候特征

利用张掖试验基地2006年6月24日至7月17日的加密观测资料,系统分析了夏季典型晴天张掖绿洲荒漠过渡带地表辐射收支和地表能量平衡特征及小气候特征。结果表明:夏季晴天绿洲荒漠过渡带总辐射值还是比较大的,并且净辐射值也很大,这说明绿洲荒漠过渡带地表具有比较充足的可利用热能,为加热大气和土壤提供了必要的热能条件。在地表能量分配中,晴天绿洲荒漠过渡区主要用于大气运动引起的感热交换,其次是土壤交换,用于水蒸发相变的能量相对较小。近地层空气温度和湿度的变化刚好相反。气温白天随高度的增加而递增,夜晚随高度的增加而递减。近地层大气温度变化要比地表温度缓慢。白天土壤辐射增温,越接近地表增温越快,夜间辐射冷却,地表温度下降最为明显。近地层水平风速在白天较大,夜间逐渐减小。在绿洲荒漠过渡带全天以上升气流为主,水平风速随高度增加明显递增。     

藏北高原D110点不同季节土壤温度的日变化特征

利用１９９８年ＧＡＭＥ－Ｔｉｂｅｔ加强观测期间取得的一个年周期的土壤温度资料,对藏北高原Ｄ１１０点土壤温度日变化特征的月际变化进行了分析。结果表明,在夏半年（５－９）月土壤温度存在明显的日变化,且基本上按正弦曲线变化,但相位随深度的增加而滞后;冬半年土壤温度尽管也存在日变化,但变幅较小。     

中国西部局地蒸发水汽贡献率探讨

利用降水、湖水同位素数据并结合相关模型,对我国西部地区的二次蒸发效应以及不同类型水汽对区域降水的贡献率进行了定量的讨论,研究得到以下结论：①夏季风期间,天山-阿勒泰地区所受到的二次蒸发效应较为明显;而青藏高原地区,水体蒸发水汽的向上补给则是影响该区域在全年任何时段下氢氧同位素值发生变化的主要因素.②天山-阿勒泰地区在全年任何时段下均存在二次蒸发效应,且夏季风时的作用程度明显强烈,蒸发比值介于13%~20%,均值为16.7%,远远大于冬季风时的均值4.3%.③青藏高原地区不论是在夏季风还是冬季风期间,上风向水汽对区域降水的贡献率最大,所占比重基本大于50%,贡献率最小的是水体蒸发产生的水汽,其值普遍小于10%;而蒸腾作用产生水汽的贡献率介于两者之间.     

京津唐地区水面蒸发估算及其分布特征

本文根据官厅蒸发站20米²蒸发池的观测资料与气象要素特征值之间关系,建立道尔顿类型的水面蒸发计算模式,计算了京津唐地区60个气象站的年、月蒸发值,并绘制年、季(典型月分)的蒸发分布图。     

塔克拉玛干沙漠腹地地表辐射与能量平衡

利用2013年塔克拉玛干沙漠塔中流动沙面地表辐射、土壤热通量、土壤温湿度和湍流通量观测资料,分析了沙漠腹地地表辐射和能量收支特征及闭合状况。结果表明：除潜热通量外,其余地表辐射各分量和能量平衡分量的月平均日变化结果整体均表现为标准的单峰型日循环形态,其中R_s↓与R_s↑变化同步,R_l↑、R_l↓滞后R_s↓0.5 ~ 1 h。各分量均表现出夏季高、春秋季次之、冬季低的季节波动性。干旱和极低的植被覆盖造成沙漠腹地全年潜热通量始终较为微弱,约占净辐射的2.8%,感热通量成为能量的主要消耗形式,约占净辐射的49%。偶尔的降水会刺激潜热通量突然增加。地表反照率相对较高且稳定,日变化呈早晚大、正午小的“U”型趋势,并具有明显的冬季高、夏季低的季节波动性,年均值0.28,月均值0.25~0.32。能量残差各月的日变化也均呈单峰曲线,日出后和日落前能量闭合程度最佳,并出现过闭合现象,全年夏季小,春秋季次之,冬季较大,月平均日峰值5.1~99.9 W·m^-2。土壤表层热储存是影响该地区能量平衡的重要因子之一,考虑表层土壤热存储后,地表能量闭合率达75.3%,能量闭合率夏季 > 春季 > 秋季 > 冬季,白天相比夜间有大幅提升。     

黄河流域旱涝年夏季蒸发计算及其变化

根据我国北方的热量平衡观测资料,地立了计算感热—潜热比的经验模式,用于计算黄河流域旱涝年(1972、1975、1986、1988年)及一般年(1971、1974、1985、1987年)夏季陆面蒸发,并分析其变化特点以及与旱涝的关系。     

Characteristics of freshly deposited sand and finer sediments along an island-braided, gravel-bed river: The roles of water, wind and trees

Over the past two decades there has been a growing interest in the geomorphological mosaic along large floodplain rivers where channel dynamics are seen to drive habitat-patch creation and turnover and to contribute to high biological diversity. This has required a new perspective on fluvial geomorphology that focuses on biological scales of space and time. This study examines the spatial pattern of surface fine sediment accumulations along a reach of a large gravel-bed river, the Tagliamento River in NE Italy; an area with a moist Mediterranean climate and seasonal flow regime. The study investigates changes in sediment characteristics during the summer low-flow period between April and September. Focussing on five areas representing a gradient from open, bar-braided to wooded island-braided morphologies, the paper demonstrates the importance of riparian vegetation and aeolian–fluvial interactions.Significant contrasts in particle size distributions and organic content of freshly deposited sand and finer sediments were found between sampling areas, geomorphological settings, and sampling dates. In particular, wooded floodplain and established islands supported consistently finer sediment deposits than both open bar surfaces and the lee of pioneer islands, and in September significantly finer sediments were also found in deposits located in the lee of pioneer islands than on open bar surfaces. Overall, the September samples had a greater variability in particle size characteristics than those obtained from the same sites in April, with a general coarsening of the D₅ (φ) (i.e., the coarse tail of the particle size distribution). Also in September, crusts of fine sediment (30 μm < D₅₀ < 64 μm) had formed on the surface of some of the open bar and pioneer island deposits within the more open sampling areas along the study reach. These crusts possessed similar particle size characteristics to aeolian crusts found in more arid environments. They were significantly finer than April samples and September subcrust samples obtained from the same sites and had similar particle size characteristics to some samples taken from wooded floodplain, established island surfaces and the lee of pioneer islands that were not crusted.Local climatological and river level data confirm significant wind and rainfall events during a period of consistently low river levels between the April and September sampling periods. These support deflation, deposition and rain wash of finer sediment during the summer, with windblown sediments being deposited on bar surfaces and in the lee of pioneer islands where wood and young trees provide foci for accelerated sedimentation and island growth as well as on marginal floodplains and established islands. We conclude that along braided rivers in moist settings but with a distinct dry season, aeolian reworking of sediment deposits may have a more important role in driving habitat dynamics than previously considered.     

巴丹吉林沙漠典型湖泊湖气界面水一热交换特征

利用2012年8月-2013年7月在巴丹吉林沙漠腹地典型湖泊上用涡动相关系统观测的湍流资料,分析了湍流方差统计特征、微气象特征,计算了湍流热通量和湖泊蒸发量,初步结论为：①湖面上局地环流复杂,湍流三维风速的标准差与稳定度(Z/L)之间满足1/3次律。②湖面辐射分量具有明显季节变化和日变化特征,结冰期和非结冰期能量分配不同,冬季湖泊将储存的能量向大气传递;潜热通量和感热通量季节变化存在差异,但均有明显的昼夜变化特征。③湖气界面的感热通量在不同的月份也存在差异,感热以湖泊向大气传递为主;潜热通量夏半年远大于冬半年,在一天中6:00-8:00时处于最低值,15:00-16:00时达到峰值,在冬季会出现潜热向下输送现象。感热通量和潜热通量日变化呈负相关,湖面有效能量主要分配给潜热,湖泊同周围环境以水汽交换为主。④湖面平均蒸发速率为3.97 mm/d,累计蒸发量为1450±10 mm/a,同期的蒸发量是降水量的20多倍,湖泊主要靠地下水补给。这些结论可为进一步研究巴丹吉林沙漠腹地湖泊群的水循环及补给来源提供参考。     

西沙赵述岛地表蒸散发实验

蒸散是岛礁水循环过程中的重要组成部分,对保护珊瑚岛礁生态有重要意义.2018年6月27日-2018年8月8日利用自制的微型蒸渗仪及蒸发皿,在中国西沙群岛赵述岛开展了野外蒸散观测实验,获得了岛礁砂壤土裸地雨后实际蒸发速率,以及不同下垫面及钙质砂质地情形下潜在蒸散特征.其中,砂壤土裸地实际蒸发观测表明,雨后第2日至第4日平...     

河北省近40年蒸发皿蒸发量变化特征及影响因素初探

利用河北省区域1963-2003年50个站蒸发皿蒸发量资料,分析了蒸发量变化及影响因素。结果表明:近40年来河北省区域平均年和四季蒸发量变化,由60、70年代偏多转为80、90年代偏少,转折年均在70年代末和80年代初。春、夏季蒸发量减少趋势明显,分别为-31.3、-27.4mm/10 a,年蒸发量的减少主要是由春、夏季减少所致;对蒸发量的空间分析表明,区域内94%的站点呈减少趋势,70%站点减少趋势显著,减少速率最大区域在冀中南部东部区域,减少速率在-100mm/10 a以上;蒸发量变化与各要素相关分析表明,蒸发量变化与日照时数、低云量、气温日较差相关显著,而日照时数、低云量、气温日较差与太阳辐射大小关系密切,因此,太阳辐射是影响蒸发量变化的主要因素,同时平均风速的减少对蒸发量的减少也起着重要作用。     

Influence of vegetation canopies on solar potential in urban environments

Solar energy is clearly a promising option among the many available sources of renewable energy, and its market has seen outstanding growth. Careful evaluation to determine suitable locations for photovoltaic installations is needed, however, as their efficiency is highly dependent on exposure to sun. Especially in urban environments, quantifying the shadows cast by other buildings and vegetation canopies may be essential. In the present study, we used light detection and ranging (LiDAR) data and geographic information systems (GIS) to assess the influence of shading vegetation on solar irradiation estimates in five European towns. The fraction of annual solar irradiation lost to shading by existing vegetation ranged between 3% and 11%. The fraction lost was higher in winter and lower in summer. Due to greater incoming solar radiation in summer, however, more than 50% of annual loss was accounted for in summer. We suggest that at the broad scale of whole cities the influence of vegetation on rooftop solar potential estimates is negligible (especially in densely populated areas). Analyses which do not consider vegetation because of data availability nevertheless provide valuable insight into localities' solar potential.     

塔克拉玛干沙漠不同下垫面太阳总辐射比较

本文运用统计学方法,分析并比较了塔克拉玛干沙漠绿洲-沙漠过渡带（肖塘、哈德）与沙漠腹地（塔中）总辐射的气候学特征。结果表明：沙漠腹地（塔中）总辐射年总量高于绿洲-沙漠过渡带（肖塘、哈德）,塔中、肖塘和哈德年总量分别为6 515.0 MJ·m^-2、5 666.4 MJ·m^-2和5 774.5 MJ·m^-2。春、夏、秋、冬四季变化幅度,塔中高于肖塘和哈德,肖塘与哈德相近;3个观测点均为夏季最大、冬季最小、春季高于秋季。塔中月总量最大值出现时间（6月）早于肖塘和哈德（7月）,最小值均在12月;塔中月总量最大值比肖塘和哈德分别高99.4 MJ·m^-2和81.9 MJ·m^-2。平均日变化表现为早晚小、正午12：00最大。沙尘暴天气下总辐射被明显削弱,日变化波动大。肖塘、哈德和塔中沙尘暴日的峰值分别减少40.3%、56.2%和53.0%;日总量分别减少41.6%、57.8%和61.2%。沙尘暴日的后续天气仍受到沙尘的明显影响,只有当整个沙尘天气过程结束其日变化曲线才恢复。沙尘天气日,小时平均值>500 W·m^-2的总辐射明显被削弱,主要向低值区集中,分布在高值区的概率减少。总辐射与太阳高度角的变化一致,相同太阳高度角下晴天总辐射高于沙尘天。     

策勒绿洲沙漠过渡带小气候的空间差异

对策勒2011年1—12月4个不同下垫面的风速、温度、湿度、光合有效辐射的月差异进行分析,同时选取夏季晴天天气作为背景,比较沙尘暴、扬沙、浮尘、阴雨天时4个下垫面气象要素的差异。结果标明:与流沙地相比,绿洲-沙漠过渡带半固定沙地、固定沙地、绿洲内部2.0 m高处的6月平均风速依次减少了25.22%、27.93%、65.27%,12月绿洲内部0.5 m高处平均气温分别高于流沙地、半固定沙地、固定沙地1.39 ℃、1.21 ℃、2.70 ℃。5—10月4个下垫面之间温、湿度差异较春、冬季显著,7月流沙前沿2.0 m高处平均气温分别比半固定沙地、固定沙地、绿洲内部高0.35 ℃、1.61 ℃、3.75 ℃。沙尘暴天气下4个下垫面之间的风速差值依次小于扬沙、浮尘、阴雨、晴天天气下;在浮尘和晴天天气下,气温从流沙前沿到绿洲内部逐渐减低,相对湿度逐渐增加;沙尘暴和阴雨天气下各下垫面的气温和相对湿度无明显差异,扬沙天气下各下垫面之间温、湿度差异大于阴天天气,但小于浮尘和晴天天气;4个下垫面之间的光合有效辐射（PAR）在沙尘暴天气下差异最为明显,浮尘和阴雨天气下4个下垫面之间的PAR接近,晴天天气下各点PAR明显大于扬沙天气下,且各下垫面之间差异大于扬沙天气下的差异。     

海南岛橡胶林辐射通量特征

热带橡胶人工林作为我国热带地区最重要的生态系统,在森林辐射研究中扮演着重要角色。随着橡胶林在我国热带地区大面积地种植,对其生态效应的质疑也在增加,有必要对其辐射通量进行研究。基于海南岛橡胶林2010年1 a的辐射观测数据,分析了其时序变化和分配等规律。结果表明：研究区橡胶林的太阳总辐射（DR）、反射辐射（UR）和净辐射（NR）通量日变化呈典型的单峰曲线,大气逆辐射（DLR）、森林长波辐射（ULR）、长波有效辐射（Ln）呈波浪形;各辐射总量除Ln 外,均为雨季大于旱季;海南岛橡胶林DR年总量为5 356.99 MJ/m2,NR、UR和Ln占其比例分别为67%、15%和18%;NR通量分配率日变化呈倒“U”型曲线,Ln和UR通量分配率则呈“U”型曲线。另外,文章还研究了各辐射通量间的关系。2010年全年反射率均值为14.18%,全年DLR与ULR之比为92.89%,净辐射NR与太阳总辐射DR关系最为密切。     

我国太阳能分布的非线性回归模式

本文通过非线性拟合,给出我国太阳总辐射Q和直接辐射S＇的年值和月值分布的计算公式,年值公式适用于任一地点,月值公式适用于任一月分和任一地点,简化了计算程序。验证结果表明,用这些公式拟合实测Q的累年平均年值和月值的相对误差66站平均分别为4%和5%,拟合实测S＇的累年平均年值和月值的相对误差55站平均分别为6%和10%。因此可用这些公式估算无实测辐射资料地点的上述辐射量。     

玉溪市太阳能光伏电站发展前景分析

玉溪市太阳能光伏电站发展具备地理位置、气候特点、太阳辐射、用电需求等优势,不利的方面主要有地形和成本因素,但随着玉溪对能源的需求量日益增加,太阳能开发利用不仅是电力供应的新途径,而且是实现环境、经济、社会统一发展的清洁能源。建设光伏电站,科学选址非常重要。玉溪市共筛选到符合条件的场址13个,场址均为荒山、荒地、石漠化地或低产坡地,整体坡向为"北高南低",周围无高山阻挡,地势开阔,地下无矿产资源,无军事敏感设施,交通条件和电网接入条件较便利。预计项目建设总面积897.3 hm2(13 190亩),装机容量343 MW,总投资约76.35亿元,年发电量6.174×108 kW.h,年收益可达81 651.15万元。     

红河流域气温和蒸发量时空变化分析

使用研究区44个气象站1960-2000年的逐月20cm蒸发皿蒸发量、气温的实测资料,分析了红河流域气温和蒸发量的时空变化特征。结果表明：（1）红河流域年均气温呈上升的趋势,1960-2000年间年均气温上升了约0．52℃;其中20世纪60年代和70年代气温变化不大,80年代和90年代急剧上升;季节上以夏季上升趋势最为显著,气候倾向率为0．14℃／10a。（2）红河流域年均蒸发量呈下降的趋势,40年间下降了约45．52mm;其中60年代和70年代相差不大,80年代急剧下降,到90年代有所上升;季节上以春季和夏季下降趋势显著,气候倾向率分别为-1.63mm／10a和-7．63mm／10a。（3）年均气温和蒸发量变化的趋势具有明显的空间分布差异。全流域气温的气候倾向率在-0．21℃／10a-0．35℃／10a,主要的增温区域分布在李仙江和藤条江地区。蒸发量的气候倾向率在-48mm／10a～11mm／10a,蒸发量明显减少区域主要分布在李仙江下游的江城、元江流域的楚雄、元阳、河口和盘龙河流域的文山地区。     

互补相关蒸散发理论与应用研究

本文提出和建立了一个计算蒸散发能力和饱和湿润表面蒸散发量的经验公式,并把互补相关模型应用到湖北省十六个流域,江汉平原水网区和东湖的蒸散发估计。模型的计算值同水量估计值以及蒸发的研究和计算提供了另一条简便易行的途径。     

Radiation balance and the response of albedo to environmental factors above two alpine ecosystems in the eastern Tibetan Plateau

Understanding the energy balance on the Tibetan Plateau is important for better prediction of global climate change. To characterize the energy balance on the Plateau, we examined the radiation balance and the response of albedo to environmental factors above an alpine meadow and an alpine wetland surfaces in the eastern Tibetan Plateau, using 2014 data. Although our two sites belong to the same climatic background, and are close geographically, the annual incident solar radiation at the alpine meadow site(6,447 MJ/(m2·a)) was about 1.1 times that at the alpine wetland site(6,012 MJ/(m2·a)),due to differences in the cloudiness between our two sites. The alpine meadow and the alpine wetland emitted about 38%and 42%, respectively, of annual incident solar radiation back into atmosphere in the form of net longwave radiation; and they reflected about 22% and 18%, respectively, of the annual incident solar radiation back into atmosphere in the form of shortwave radiation. The annual net radiation was 2,648 and 2,544 MJ/(m2·a) for the alpine meadow site and the alpine wetland site, respectively, accounting for only about 40% of the annual incident solar radiation, significantly lower than the global mean. At 30-min scales, surface albedo exponentially decreases with the increase of the solar elevation angle; and it linearly decreases with the increase of soil-water content for our two sites. But those relationships are significantly influenced by cloudiness and are site-specific.