南极瑞穗站辐射平衡及湍流通量特征

本文利用南极瑞穗站１９７９—１９８０年近地面层微气象及辐射平衡等观测资料，分析了春、夏、秋和冬季辐射平衡分量的日、年变化特征，采用空气动力学方法和廓线梯度迭代法计算了不同季节的动量通量、感热通量和由能量平衡方程得到的潜热通量的日变化特征，并对计算结果进行了比较。文中还对湍流热量交换系数、湍流动量交换系数与理查孙数的日变化关系进行了讨论。     

青藏高原东部多、少雪年地表能量和水分特征对比研究

青藏高原积雪对地表能量和水分交换有重要影响。本文通过选取青藏高原东部玛多、玛曲和垭口3个站点多雪年和少雪年的气象资料,对比分析了多雪年和少雪年的地表能量和土壤水热特征。结果表明：在地表辐射平衡方面,多雪年或积雪较多的时期可以反射掉较多的向上短波辐射。玛多站多雪年反射掉的向上短波辐射是少雪年的2.3倍,玛曲站主要积雪期（3-5月）中多雪时期比少雪时期多反射掉10.07 W·m^-2的向上短波辐射,垭口站多雪年的年平均向上短波辐射分别比两个少雪年高出37.49 W·m^-2和31.92 W·m^-2。多雪年或积雪较多的时期还可以减少向上长波辐射的发射。玛多站多雪年与少雪年向上长波辐射的差值在整个研究时段中基本为负,垭口站两个少雪年在当年12月初到次年1月和次年2月末到4月初这两个时段,积雪越深,向上长波辐射值越小。向上短波和向上长波辐射的差异使得多雪年的地表净辐射少于少雪年。不论多雪年还是少雪年,土壤热通量的值都很小,地表能量分配主要以感热通量和潜热通量为主。玛多站少雪年以感热通量为主且感热通量为正,但多雪年感热通量为负;玛曲站的...     

珠峰北坡地区地表辐射和能量季节变化的初步分析

对青藏高原地区地表能量的研究是一个十分重要的问题.利用中国科学院珠穆朗玛峰大气与环境综合观测研究站2006年5月至2007年4月一年的观测资料,分析了青藏高原珠峰地区的地表能量,即净辐射通量、感热通量、潜热通量和土壤热通量,得到了一些有关珠峰地区地表能量的结果,即太阳总辐射、大气长波辐射、地面长波辐射和净辐射呈现出明显的年变化特征,净辐射、感热通量、潜热通量和土壤热通量得到的日变化是很明显的.并且讨论了计算地表能量通量的方法及其优缺点.     

我国北方不同下垫面地表能量通量的变化特征

利用"中国干旱气象科学研究计划——我国北方干旱致灾过程及机理"的观测数据,分析塔中站、奈曼站、平凉站和锦州站2015年8—10月及定西站2016年8—10月地表能量通量变化特征。分析发现,不同下垫面辐射均表现出明显的日变化,相对于向下短波辐射和向下长波辐射,不同下垫面反射辐射和向上长波辐射差异更加明显。塔中站反射辐射和向上长波辐射最大,锦州站和平凉站相对较小。净辐射具有明显的日变化特征,和总辐射相位一致,农田净辐射日峰值相对较大。地表反照率3个月平均从大到小依次为塔中站(0. 27)、定西站(0. 19)、锦州站(0. 16)、奈曼站(0. 15)和平凉站(0. 14)。各站点感热通量和潜热通量均为单峰型,其中,奈曼站感热通量峰值最大(276 W·m~(-2)),平凉站潜热通量峰值最大。定西站和锦州站净辐射分配以感热通量为主,平凉站则以潜热通量为主。     

2008年夏季风期间西沙海域海-气通量交换及热量收支

2008年4—10月在中国南海西沙永兴岛近海进行了第4次海-气通量观测试验,获得了整个夏季风期间近海面层湍流脉动量及辐射、表层水温、波浪及距水面3.5、7.0、10.5m高度温、湿、风梯度观测资料,根据涡动相关法和COARE3.0法计算结果研究了2008年南海西南季风爆发、发展、中断、衰退包括暴雨、台风、冷空气影响等天气过程中海-气通量交换和热量收支变化。结果表明:(1)季风爆发前的晴天太阳总辐射强,而海洋失热量较小,热量净收支为较大正值,海面温度迅速升高。季风爆发期太阳总辐射仍然较强,大气长波辐射也有所增强,而海面长波辐射变化很小,故海面净辐射收支仍为正值;(2)季风活跃期特别是降水阶段感热通量增大,季风中断阶段变小;季风活跃期虽然潜热通量增大,由于太阳短波辐射没有减少,海洋净热量收支稍有盈余;中断阶段潜热通量、感热通量减少,海洋吸热大于季风活跃期;降水阶段由于太阳短波辐射减小,感热通量增大,海洋热量收支出现较大负值,海面温度很快降低。季风衰退期风力减弱,湿度减小,潜热通量减小,海洋热量收入又出现较大正值,海面温度回升;(3)台风影响过程中潜热通量随着风速增强迅速增大;感热通量因降水情况不同而有差异,晴天时减小,大雨时剧烈增大;由于太阳短波辐射减少、潜热通量剧增,海洋热量净收支出现负值,促使海面温度迅速降低;(4)动量通量主要与海表面风速有关;动量通量τ与风速V的关系可以表示为τ=0.00171v~2-0.003809v+0.02213。     

青藏高原积雪对陆面过程热量输送的影响研究

利用1979-2016年中国区域长时间序列逐日雪深资料,分析了青藏高原积雪深度与积雪日数的分布及变化特征,并将积雪期划分为三个阶段(积累期、鼎盛期和消融期),结合ERA-Interim月平均再分析资料,分析了积雪与地表热状况(气温、地表和土壤温度)和能量输送量(地表净短波辐射、地表净长波辐射、感热通量、潜热通量、地表热通量和土壤热通量)的相关关系,初步探讨了积雪在高原陆面过程中的作用。结果表明:研究时间范围内青藏高原积雪(深度和日数)主要呈减少趋势,仅在黄河源区及高原边缘地区为增加趋势,积雪鼎盛阶段(1-2月)的减少趋势最显著;高原积雪对地表主要起降温作用,深层土壤温度对积雪的响应存在滞后性,积雪的减少抑制了土壤向上的热量输送进而不利于冻土的发育;高原积雪与地表感热和地表热通量主要呈现负相关关系,潜热通量与积雪也呈负相关特征但比感热通量的相关性小。由于ERA-Interim资料对高原积雪深度的描述与本研究使用的卫星遥感积雪深度存在较大偏差(包括空间分布、气候倾向率、年际变化以及绝对大小等),导致本研究中积雪与地表热状况和热通量的相关度不高,需要通过陆面模式模拟做进一步探讨。     

河西走廊地-气之间感热交换的年变化与年际变化

本文利用1971～1980年河西走廊12站地面月半均气候资料,计算并分析了河西走廊地-气之间感热交换的时空变化特征。结果表明:河西走廊各站地面感热通量的年变化与地面净辐射能收支的年变化完全一致,此特点与高原不同;在该区内地面感热通量的年变化有明显的地域差异;功率谱分析发现,该区月平均地面感热通量有显著的准3年周期波动。     

典型干旱区陆面模式模拟检验

利用2000年9月至2001年8月"我国西北干旱区陆-气相互作用试验(NWC-ALIEX)"敦煌站的陆面过程观测资料,基于已有的参数化结果,模拟了敦煌主要陆面特征。结果表明:典型干旱区敦煌夏季感热通量与潜热通量差异显著,感热几乎是潜热的4倍,冬季二者都很小。模式对地表温度模拟较好,但高估了浅层土壤湿度峰值;对向上辐射模拟较好,但对净辐射的模拟存在较大偏差;同时高估了地表能量的峰值。模式结果表明参数化方案对干旱区陆面过程模式具有一定的改进作用。     

Estimation of the surface heat budget over the South China Sea

本文运用了南海观测资料去评估五个海表热通量格点资料,同时,也计算了这五种格点资料的海表热收支平衡。结果发现这些格点资料都低估了短波辐射和感热通量,但是潜热通量除了NOC2外都相对接近观测值。低估了短波辐射也表明了这些格点资料可能低估了海表热收支。五种格点资料的净热通量都是正值,表明海洋从大气中获得热量。综合比较来看的话,NOC1资料所得的海表热通量收支可能更接近于观测值,更合理。     

白洋淀水陆不均匀地区能量平衡特征分析

应用2005年9月在河北白洋淀地区进行的大气边界层综合观测实验资料, 对水陆不均匀地表条件下的白洋淀地区陆地的能量平衡特征进行了分析。结果表明: (1) 该地区存在能量不闭合现象。涡动相关法得到的感热、 潜热之和仅为有效能的75%, 其中涡动相关法得到的潜热通量为Bowen比法得到的潜热通量的70%, 而涡动相关法得到的感热通量为Bowen比法得到的感热通量的77% 。 (2) 地表潜热通量和感热通量随着净辐射的变化而变化。但潜热通量明显比感热通量大, 净辐射主要消耗于地表的水汽蒸发。 (3) 该地区白天的Bowen比平均在-0.4~0.4之间, 总体平均为0.131。受天气条件影响较大, 有明显的日变化, 午后15:00以后近地面层会出现逆温, Bowen比变为负值。 (4) 能量闭合程度有一定的日变化, 随着太阳高度角的增大而增大。     

Influence of snow cover changes on surface radiation and heat balance based on the WRF model

The snow cover extent in mid-high latitude areas of the Northern Hemisphere has significantly declined corresponding to the global warming, especially since the 1970s. Snow-climate feedbacks play a critical role in regulating the global radiation balance and influencing surface heat flux exchange. However, the degree to which snow cover changes affect the radiation budget and energy balance on a regional scale and the difference between snow-climate and land use/cover change (LUCC)-climate feedbacks have been rarely studied. In this paper, we selected Heilongjiang Basin, where the snow cover has changed obviously, as our study area and used the WRF model to simulate the influences of snow cover changes on the surface radiation budget and heat balance. In the scenario simulation, the localized surface parameter data improved the accuracy by 10 % compared with the control group. The spatial and temporal analysis of the surface variables showed that the net surface radiation, sensible heat flux, Bowen ratio, temperature and percentage of snow cover were negatively correlated and that the ground heat flux and latent heat flux were positively correlated with the percentage of snow cover. The spatial analysis also showed that a significant relationship existed between the surface variables and land cover types, which was not obviously as that for snow cover changes. Finally, six typical study areas were selected to quantitatively analyse the influence of land cover types beneath the snow cover on heat absorption and transfer, which showed that when the land was snow covered, the conversion of forest to farmland can dramatically influence the net radiation and other surface variables, whereas the snow-free land showed significantly reduced influence. Furthermore, compared with typical land cover changes, e.g., the conversion of forest into farmland, the influence of snow cover changes on net radiation and sensible heat flux were 60 % higher than that of land cover changes, indicating the importance of snow cover changes in the surface-atmospheric feedback system.     

The role of wintertime radiation in maintaining and destroying stable layers

Summary Strong stable layers are a common occurrence during western Colorado's winter. Analysis of radiosonde observations indicate wintertime boundary layer heights are near 500 m. The terrain in this region consists of mountains that rise approximately 1500–2000 m above the ground to the east, providing an effective blocking barrier. An experiment is described to observe upwelling and downwelling, longwave and shortwave radiative fluxes at two sites in western Colorado during January and February 1992, for combinations of clear, cloudy, snow covered, and bare ground periods. Analysis of the observations and the surface energy budget for typical Bowen ratios provides a better understanding of the role of radiation in maintaining and destroying stable layers.During the day, the surface received a net gain of energy from radiation, while at night there was a net loss. Over snow, the 24-hour net radiative flux was small and either positive or negative. Over bare soil, the 24-hour net radiative flux was positive but still small. There is little difference in the net radiative flux between clear and cloudy days; the reduction of the incident solar flux by clouds is nearly compensated by the hindering of the longwave cooling. The cumulative effects of the 24-hour net radiative flux were negative over snow early in the experiment. The 24-hour values shifted to near zero as the snow albedo decreased and were positive for bare ground.If the daytime net radiative flux is partitioned into sensible and latent heat flux using typical Bowen ratios, the daytime sensible heat available for destroying boundary layers is small for the low solar angles of the winter season. With a Bowen ratio of 0.5, the daytime sensible heat flux available is only 0.3 to 1.2 MJ m^–2 over a snow surface and 1.4 to 2.3 MJ m^–2 over soil. These heat fluxes will not build a deep enough boundary layer to break a typical wintertime inversion. The 24-hour sensible heat flux was negative at both sites for the entire experiment with this Bowen ratio.The radiation observations and the use of typical Bowen ratios lead to the conclusion that the net radiation will sustain or strengthen a stable atmosphere in the winter season in western Colorado. Analysis of the radiosonde observations confirm this result as the boundary layer depths were less than 500 m early in the experiment and grew to only 700 m later in the experiment.With 12 Figures     

An all-slope 24-hour summer energy budget regime along a climatic-latitudinal transect

A physically-based solar radiation transmission model and a slope energy budget model were available which used climatic observations, averaged over 10-deg north-south latitude bands. This made possible the systematic examination of the diurnally changing energy budget components of net radiation, conduction, sensible, and latent heat flux occurring at all slope angles (0 to 90 deg) and slope directions (south-, west-, and north-facing). The present analysis utilized two contrasting landscapes along a latitudinal transect of the east coast of the Americas (northern hemisphere). Among the results, the maximum net radiation for all slope angles and directions occurred at noon on a 40-deg, south-facing slope for latitude 60. Generally, latent and sensible heat fluxes were similar in trend and magnitude between latitudes 0 and 35. Poleward, sensible heat flux increased with advancing latitude at the expense of latent heat flux. A great diversity in net radiation, sensible, and latent heat flux was obtained between different slopes and their orientation at a paniculate latitude. In addition to hourly rates of the energy budget components, daily positive sums of net radiation, sensible, and latent heat flux were examined. It is assumed that the portrayed patterns are general enough to add to our increasing understanding of the contrasts possible in a real-world north-south transect.     

Simulation of snow processes beneath a boreal scots pine canopy

A physically-based multi-layer snow model Snow-Atmosphere-Soil-Transfer scheme(SAST)and a land surface model Biosphere-Atmosphere Transfer Scheme(BATS)were employed to investigate how boreal forests influence snow accumulation and ablation under the canopy.Mass balance and energetics of snow beneath a Scots pine canopy in Finland at different stages of the 2003-2004 and 2004 2005 snow seasons are analyzed.For the fairly dense Scots pine forest,drop-off of the canopy-intercepted snow contributes,in some cases,twice as much to the underlying snowpack as the direct throughfall of snow.During early winter snow melting,downward turbulent sensible and condensation heat fluxes play a dominant role together with downward net longwave radiation.In the final stage of snow ablation in middle spring,downward net all- wave radiation dominates the snow melting.Although the downward sensible heat flux is comparable to the net solar radiation during this period,evaporative cooling of the melting snow surface makes the turbulent heat flux weaker than net radiation.Sensitivities of snow processes to leaf area index(LAI)indicate that a denser canopy speeds up early winter snowmelt,but also suppresses melting later in the snow season. Higher LAI increases the interception of snowfall,therefore reduces snow accumulation under the canopy during the snow season;this effect and the enhancement of downward longwave radiation by denser foliage outweighs the increased attenuation of solar radiation,resulting in earlier snow ablation under a denser canopy.The difference in sensitivities to LAI in two snow seasons implies that the impact of canopy density on the underlying snowpack is modulated by interannual variations of climate regimes.     

Surface energy budget dynamics of short-rotation willow forest

Summary Knowledge of how energy budget components vary with time, vegetation type and stage of development and field size is important if we are to increase our understanding of the energy budget on a regional scale. The aim of this study was to quantify the seasonal and diurnal variation of energy budget components of a 2.6 ha short-rotation stand. Measurements were made using a thermometer interchange system for gradient and Bowen ratio estimations. Energy storage in soil, air and biomass was determined from temperature and humidity measurements. The partitioning of available energy between sensible and latent heat fluxes changed drastically at the beginning of the season. From the first half of May until the second half of June the maximum (noon) latent heat flux increased by a factor of 3, the total storage decreased by a factor of 2 and the sensible heat flux decreased by a factor of 4.5, while net radiation was unchanged. The vapour pressure deficit was similar during these periods but the leaf area index increased from about zero to three. On a mean monthly basis, the sensible heat flux was negative (directed towards the surface) from June to October, i.e., during most of the season. Heat was supplied to the atmosphere only at the beginning of the season for this type of short-rotation stand. Heat storage in air and biomass was significant on an hourly basis, especially in mornings and evenings when it could be of the same order as the net radiation. It was concluded that the development stage of the short-rotation stand had a large influence on how the energy was distributed between the convective fluxes. It was also concluded that storage in air and biomass had to be accounted for if precise estimates of energy balance on a shorter (hourly) time scale were required.With 5 Figures     

青藏高原地区大气顶净辐射与地表净辐射的关系

地表净辐射为地气系统净辐射与大气层净辐射之差。对大气层净辐射作不同的假定，可将地表净辐射与大气顶辐射收支之间的关系表示成不同的形式。本文利用１９８２年８月—１９８３年７月青藏高原地区地面辐射收支观测资料及同期ＮＯＡＡ－７辐射收支资料，用统计方法讨论了大气顶净辐射与地表净辐射之间的相关性，建立了两者之间的回归方程，并在此基础上分析了青藏高原地区月平均地表净辐射的时空分布特征。     

STUDY ON AIR-SEA HEAT EXCHANGE MECHANISM IN EL NINO AND LA NINA EVENTS

2°×2° mean monthly COADS grid data in 1974 and 1987 of E1 Nino and La Nina years are used to compute thesensible and latent heat fluxes,the net longwave radiation,the incident solar radiation and heat budget on the tropicalPacific surface(30°S—30°N).The difference of the heat budget between El Nino and La Nina mainly occurred on theequatorial ocean surface,especially the water area west of Ecuador and Peru.During El Nino,the sensible and latentheat exchange increased,the net longwave radiation and incident solar radiation decreased and the net gain(loss) of heatreduced(increased) on the ocean surface.During La Nina,the circumstances were opposite.Finally an ideal model ofair-sea heat exchange mechanism for the El Nino-La Nina cycle is summarized. Key words:El Nino,La Nina,air-sea heat exchange,COADS grid data     

巴丹吉林沙漠不同下垫面辐射特征和地表能量收支分析

利用2009年夏季在内蒙古自治区阿拉善右旗境内巴丹吉林沙漠开展的"巴丹吉林沙漠陆-气相互作用观测试验"所取得的资料,对比分析了典型晴天条件下,巴丹吉林沙漠两种不同下垫面的辐射平衡特征和地表能量收支的日变化规律。结果表明,不同下垫面地表反射率具有明显的差异,沙漠反射率为0.33,湖区沙生芦苇反射率为0.23,沙漠反射率大于沙生芦苇反射率。巴丹吉林沙漠两种典型下垫面上,各辐射分量均具有相似的日变化特征,即白天大、夜间小。两种下垫面上的净辐射日变化与峰值基本相同,日积分值均约为8MJ.m-2。由于下垫面性质不同,地表能量的分配也不相同。沙漠主要以感热通量为主,地表热流量其次,潜热通量很小可以忽略不计;湖区以潜热通量为主,感热通量和地表热流量次之。     

中国西天山季节性积雪热力特征分析

利用中国天山积雪雪崩站干、湿雪雪层内每隔5min一次的10层雪温数据,探讨了一次降雪过程后干、湿雪的雪层温度特征,对比分析了干、湿雪的雪面能量平衡方程中各分量的差异。结果表明:(1)整个冬半年积雪各层温度基本<0℃,雪温日变化振幅由雪面向下逐渐减小,积雪深层温度的波峰(谷)值稍滞后于积雪浅层温度极值1～2天。(2)湿雪冷中心的出现时间早于干雪,暖中心的出现时间晚于干雪,太阳辐射对湿雪的穿透深度大于干雪。(3)雪层温度振幅变化与能量吸收随雪深都呈指数衰减分布。积雪密度越大,吸收系数越小,穿透深度越大。(4)干雪雪面的感热通量和潜热通量几乎都为负值,积雪积累。湿雪雪面的潜热通量与感热通量方向相反,互相抵消,所以净辐射是导致湿雪消融的主要因素。