南极中山站至Dome A考察断面湍流参数特征近地层湍流参数特征

利用南极中山站至Dome A考察断面上3个自动气象站2005～2007年的观测资料和2008年夏季在中山站附近冰盖获取的湍流观测资料,应用空气动力学方法和涡动相关法计算分析了中山站至Dome A断面上近地层各种湍流参数(感热通量,潜热通量,湍流温度、湿度和速度尺度,地表粗糙度,大气稳定度及动量输送系数)的季节变化、日变...     

The effects of small water bodies on the atmospheric heat and water budgets over the MacKenzie River Basin

The effects of small water bodies or lakes on the surface sensible and latent heat fluxes and the transport of heat and water vapour in the atmospheric boundary layer (ABL) over the Mackenzie River Basin (MRB) are studied from two cases, which occurred on 2 and 8 June 1999 during the warm season. The synoptic condition for the cases is representative of about 33% of the synoptic situation over the MRB. The two events are simulated using the Canadian mesoscale compressible community (MC2) model. A one‐way nesting grid approach is employed with the highest resolution of 100 m over a domain of 100 km². Experiments were conducted with (LAKE) and without (NOLAKE) the presence of small water bodies, whose size distribution is obtained through an inversion algorithm using information of their linear dimension determined from aircraft measurement of surface temperature during MAGS (the Mackenzie GEWEX (Global Energy and Water Cycle Experiment) Study) in 1999. The water bodies are assumed to be distributed randomly in space with a fractional area coverage of 10% over the MRB. The results show that, in the presence of lakes, the domain‐averaged surface sensible heat flux on 2 June 1999 (8 June 1999) decreases by 9·3% (6·6%). The surface latent heat flux is enhanced by 18·2% (81·5%). Low‐level temperature advection and the lake surface temperature affect the air–land/lake temperature contrast, which in turn controls the sensible heat flux. In the absence of lakes the surface wind speed impacts the latent heat flux, but in the presence of lakes the moisture availability and the atmospheric surface layer stability control the latent heat flux. The enhancement is smaller on 2 June 1999 as a result of a stable surface layer caused by the presence of colder lake temperatures. The domain‐averaged apparent heat source and moisture sink due to turbulent transports were also computed. The results show that, when lakes are present, heating and drying occur in the lowest 100 m from the surface. Above 100 m and within the ABL, there was apparent cooling. However, the apparent moistening profiles reveal that lakes tend to moisten the ABL through transfer of moisture from the lowest 50–100 m layer. Copyright © 2004 John Wiley & Sons, Ltd.     

不同强度冷空气对太湖水热交换的定量影响

作为冷季主要的天气事件，冷空气过境会改变湖泊上方的气团性质，对湖泊的水热通量产生影响，进而影响湖泊的生物物理和化学过程.以亚热带大型浅水湖泊——太湖为研究对象，基于2012-2017年5个冷季（11月-翌年3月）的太湖中尺度通量网观测数据，量化不同强度冷空气（寒潮、强冷空气和较强冷空气）对太湖水热通量的影响.结果表明：在5个冷季中，寒潮、强冷空气和较强冷空气发生的总次数分别为4、11和33次，累积持续天数分别为14、31和78天.冷空气过境显著增强太湖的水热通量，3种冷空气过境使太湖的感热通量分别增至无冷空气时的10.3、6.0和4.3倍，潜热通量分别增至无冷空气时的4.0、2.1和2.7倍.虽然冷空气影响天数仅占冷季天数的16.4%，但对整个冷季的潜热和感热通量贡献分别为34.9%和51.7%，以较强冷空气贡献最大.冷空气影响时，水-气界面的温度梯度是太湖感热通量的主控因子，而潜热通量的主控因子为风速.与深水湖泊相比，太湖等浅水湖泊对冷空气过境的响应更快，寒潮过境时尤为明显.     

鄱阳湖夏季水热通量特征及环境要素影响分析

气候变化加速了全球水文循环过程,然而,气候变化如何影响水体蒸发及其水热通量交换仍然不清楚.基于涡度相关系统观测鄱阳湖水体水热通量过程,在小时和日尺度分析了水热通量的变化规律及其主要影响因子.研究表明,潜热通量日变化波动剧烈,大部分为正值,变化范围在-50~580 W/m2之间.而感热通量数值较小,变化范围在-50~50 W/m2之间.8月份潜热通量和感热通量均呈波动下降趋势,均值分别为167.4和15.9 W/m2.8月份日平均潜热通量和感热通量之和大于净辐射,这是由于这一时段储存在水体中的热量释放并补充潜热通量和感热通量.小时尺度上潜热通量日变化在相位上与净辐射无显著相关性,而与风速显著相关.在日尺度变化趋势上,8月份日平均潜热通量仍主要受到风速和水温的影响,感热通量则主要受到风速和饱和水汽压差的影响.     

Spatial distribution of surface energy fluxes over the Loess Plateau in China and its relationship with climate and the environment

China's Loess Plateau is located at the edge of the Asian summer monsoon in a transition zone of climate and ecology. In the Loess Plateau, climate and environments change along with space, which has an obvious impact on the spatial distribution of surface energy fluxes. Because of scarce land-surface observation sites and short observation time in this area, previous studies have failed to fully understand the land-surface energy balance characteristics over the entire the Loess Plateau and their effect mechanisms. In this paper, we first test the simulation ability of the Community Land Model(CLM) model by comparing its simulated data with observed data. Based on the simulation data for the Loess Plateau over the past thirty years, we then analyze the spatial distribution of surface energy fluxes and compare the pattern differences between the area averages for the driest year and wettest year. Furthermore, we analyze the relationship between the spatial distribution of the components of the surface energy balance with longitude, latitude, altitude, precipitation and temperature. The main results are as follows: the spatial distribution of surface energy fluxes are significantly different, with the surface net radiation and sensible heat flux increasing from south to north and latent heat flux and soil heat flux decreasing from southeast to northwest. The sensible heat flux at the driest point is nearly twice as high as that at the wettest point, whereas the latent heat flux and soil heat flux at the driest point are half as much as that at the wettest point. The impact of variations of annual precipitation on the components of the surface energy balance is also obvious, and the maximum magnitude of the changes to the sensible heat flux and latent heat flux is nearly 30%. To a certain extent, geographical factors(including longitude, latitude, and altitude) and climate factors(including temperature and precipitation) affect the surface energy fluxes. However, the surface net radiation is more closely related to latitude and altitude, sensible heat flux is more closely related to the monsoon rainfall and latitude, and latent heat flux and soil heat flux are more closely related to the monsoon rainfall.     

Distribution of ~(226)Ra in the Arctic Ocean and the Bering Sea and its hydrologic implications

The Arctic Ocean, the northernmost parts of the earth, covers the total surface area of 14.79 million square kilometers and amounts to only about 4% of global ocean surface area. Although its surface area is the smallest in the four major oceans, the Arct…     

北冰洋及其邻近海域极昼期间大气边界层结构特征试验研究

1年7-月中国"雪龙"号破冰船首航北极科学考察期间,利用TMT(系留式气象塔)大气边界层探测系统,对北冰洋及其邻近海域不同下垫面进行较长时间的连续多次观测. 观测到的大气边界层廓线,其中包括比湿廓线的多层、逆湿结构(逆湿强度最强为0.7g/(10m·kg));风向、风速廓线的切变结构(风向切变为1.1°/m,风速切变为0.11(m·s^-1)/m. 特别是持续数日、厚达几百米、其平均逆温强度有时高达1.4℃/10m的逆温结构,这种北冰洋海域特有的大气边界层结构,与地球气候系统中其他圈层的大气边界层结构有明显差别. 据此,提出了对该海域大气-海冰-海洋间动量、感热和潜热等湍流通量垂直交换以及热量平衡等有重要影响的大气逆温的屏障过程. 这为研究北极地区对全球气候影响、模拟北极地区现代气候和未来气候等提供一条新的思路. 此外,文中还给出该海域不同下垫面稳定大气边界层的高度.     

巢湖对冬季陆面辐射和热量过程的影响

从物理气候学的观点出发,分析了湖泊对水体和陆地辐射平衡和热量平衡各分量的影响。以巢湖地区冬季观测资料为例,揭示了在晴稳天气湖陆风环流对陆面显热输送的影响,以及在冷平流天气,湖泊对上下风方陆面显热输送的影响。     

非均匀灌溉棉田能量平衡特征研究

运用国际能量平衡实验(EBEX-2000)的湍流、净辐射和土壤观测资料,运用涡动相关法分析了非均匀灌溉引起的热内边界层发展条件下近地层感热、潜热通量特征,并对有无灌溉两种条件下的能量闭合度进行了对比分析.在计算感热、潜热通量过程中,分别将Schotanus订正和Webb订正纳入了考虑范围,研究了两种订正方法对计算湍流热通量的影响.研究结果发现,由于非均匀灌溉生成的热内边界层使得近地层感热通量受到抑制,潜热通量出现波动,该现象在8.7 m比2.7 m 更为显著.非均匀灌溉导致的热内边界层的存在使得近地层能量闭合度偏低,能量平衡比率约为0.65;而没有热内边界层存在时,近地层能量平衡比率约为0.70.本实验中,Schotanus订正使得感热通量显著减小,其订正量日平均值约为-8 W/m²,占净辐射的近4%;Webb订正量日平均值约为2 W/m²,对能量平衡的影响较小.     

CLM4-LISSS模型对太湖多时间尺度水热通量模拟性能的评估

湖泊模型为数值天气预报模型提供热量通量、水汽通量和动量通量等下边界条件,但是不同时间尺度上湖泊水热通量变化的控制因子不同,因此有必要对湖泊模型进行多时间尺度上的离线评估.本文利用2012-2016年太湖中尺度通量网避风港站的气象资料和辐射数据驱动CLM4-LISSS模型(Community Land Model version 4-Lake,Ice,Snow and Sediment Simulator),并与涡度相关观测(Eddy Covariance,EC)结果进行对比,以年平均潜热通量模拟结果最佳为目标调整了模式中的消光系数、粗糙度长度方案,研究了该模型从半小时到年尺度上对湖表温度和水热通量的模拟性能.结果表明:模型对湖表温度的模拟在各时间尺度上均比较理想,但是模拟的日较差较小;从半小时到年尺度上潜热通量的变化趋势都能被很好地模拟出来,但在季节尺度上,潜热通量的模拟出现了秋冬季偏高、春夏季偏低的情况,季节变化模拟不准确.湖表温度和潜热通量模拟偏差的原因可能是消光系数的参数化方案.相比之下,感热通量尽管年际变化趋势的模拟值与观测值一致,但是从半小时到年尺度均被高估.特别地,冷锋过境期间,模型能较好地模拟出潜热通量和感热通量的变化趋势,但对于高风速条件下的感热通量模拟效果不佳.本文的研究结果能为湖泊模式的应用与发展提供有用信息.     

Water and heat fluxes above a lowland dipterocarp forest in Peninsular Malaysia

We measured the fluxes of sensible and latent heat between a low‐land dipterocarp forest in Peninsular Malaysia and the atmosphere. No clear seasonal or interannual changes in latent heat flux were found from 2003 to 2005, while sensible heat flux sometimes fluctuated depending on the fluctuation of incoming radiation between wet and dry seasons. The evapotranspiration rates averaged for the period between 2003 and 2005 were 2·77 and 3·61 mm day^?1 using eddy covariance data without and with an energy balance correction, respectively. Average precipitation was 4·74 mm day^?1. Midday surface conductance decreased with an increasing atmospheric water vapour pressure deficit and thus restricted the excess water loss on sunny days in the dry season. However, the relationship between the surface conductance and vapour pressure deficit did not significantly decline with an increase in volumetric soil water content even during a period of extremely low rainfall. Copyright © 2009 John Wiley & Sons, Ltd.     

A land surface model incorporated with soil freeze/thaw and its application in GAME/Tibet

Land surface process is of great importance in global climate change, moisture and heat exchange in the interface of the earth and atmosphere, human impacts on the environment and eco- system, etc. Soil freeze/thaw plays an important role in cold land surface processes. In this work the diurnal freeze/thaw effects on energy partition in the context of GAME/Tibet are studied. A sophisti- cated land surface model is developed, the particular aspect of which is its physical consideration of soil freeze/thaw and vapor flux. The simultaneous water and heat transfer soil sub-model not only reflects the water flow from unfrozen zone to frozen fringe in freezing/thawing soil, but also demon- strates the change of moisture and temperature field induced by vapor flux from high temperature zone to low temperature zone, which makes the model applicable for various circumstances. The modified Picard numerical method is employed to help with the water balance and convergence of the numerical scheme. Finally, the model is applied to analyze the diurnal energy and water cycle char- acteristics over the Tibetan Plateau using the Game/Tibet datasets observed in May and July of 1998. Heat and energy transfer simulation shows that: (i) There exists a negative feedback mechanism between soil freeze/thaw and soil temperature/ground heat flux; (ii) during freezing period all three heat fluxes do not vary apparently, in spite of the fact that the negative soil temperature is higher than that not considering soil freeze; (iii) during thawing period, ground heat flux increases, and sensible heat flux decreases, but latent heat flux does not change much; and (iv) during freezing period, soil temperature decreases, though ground heat flux increases.     

基于双温度差分双源模型的遥感方法反演四川汶川地区的潜热通量

研究表明,在很多地震前都出现了潜热通量异常。文中基于Modis遥感数据,结合研究区(四川省汶川地区)的高光谱数据及地面观测的气象数据,利用一种简化的双层模型(双温度差分双源模型)反演显热通量,并通过地表能量平衡方程计算研究区的潜热通量。还探讨了该模型的特点,并对龙门山断裂带通过地区进行了潜热通量的遥感反演,发现在2008年5月12日汶川MS8.0地震前48h内,研究区内的震中地区、龙门山断裂周边地区潜热通量值出现了明显的高值,5月12日中午12时7分沿龙门山断裂带潜热通量值达到300～400W/m2,可能是汶川8.0级地震前的异常反应     

The problem of transfer of radionuclide pollution by sea ice

The problem of the radioactive pollution of the ice cover is discussed in this paper. An estimation of the possible transport of the radionuclides by drifting ice from the Kara Sea into the Arctic Ocean is presented. The conclusion about the importance of the contribution of drifting ice to the contamination of the Greenland coastal water is based on the comparison of estimates of the multiyear export of radioactive drifting ice from the Kara Sea with the observed concentrations of the radionuclides in the Greenland coastal water.     

Energy balance closure at ChinaFLUX sites

Network of eddy covariance observation is measuring long-term carbon and water fluxes in contrasting ecosystems and climates. As one important reference of independently evaluating scalar flux estimates from eddy covariance, energy balance closure is used widely in study of carbon and water fluxes. Energy balance closure in ChinaFLUX was evaluated by statistical regression of turbulent energy fluxes (sensible and latent heat) against available energy (net radiation, soil heat flux, canopy heat storage) and the energy balance ratio (EBR) and the frequency distribution of relative errors of energy balance (δ). The trends of diurnal and seasonal variation of energy balance in ChinaFLUX were analyzed. The results indicated that the imbalance was prevalent in all observation sites, but there were little differences among sites because of the properties variation of sites. The imbalance was greater during nocturnal periods than daytime and closure was improved with friction velocity intensifying. Generally the results suggested that estimates of the scalar turbulent fluxes of sensible and latent heat were underestimated and/or that available energy was overestimated. Finally, we discussed certain factors that are contributed to the imbalance of energy, such as systematic errors associated with the sampling mismatch, systematic instrument bias, neglected energy sinks, low and high frequency loss of turbulent fluxes and advection of heat and water vapor.     

TOGA-COARE IOP期间的海气通量观测结果

在TOGA－COAREIOP期间用涡度相关法对海气热通量进行了船载直接观测．对垂直风速、温度和湿度湍流脉动观测数据的谱分析显示它们在高频区基本满足"－2／3次方律"．对船体简谐震荡影响的讨论从理论上证明该影响在热通量计算中可被忽略．根据以此方法得到的通量求出了中性层结条件下感热和潜热的整体输送系数分别为2．25×10^－3和1．26×10^－3．对海气边界层特性的分析表明该海域的近海层主要呈中性或弱不稳定层结．海气通量的变化与背景环流形势密切相关,潜热通量主要受海面风场强度的影响,而感热通量变化除了风场的影响外,层结变化也是一个重要因素．用整体输送法计算TOGA－COAREIOP期间以及TOGA期间8个航次的通量结果而得到的Bowen比约为0．1,显示潜热通量是暖池大气的主要热源．     

2002年南海季风爆发前后西沙海区海-气通量交换及其变化

利用2002年4月24日至6月20日在西沙海区进行的第三次南海海-气通量观测试验资料,采用涡相关法和TOGA COARE25b版本通量计算方案,计算了西南季风爆发前后海洋-大气间的通量交换,讨论了辐射、动量、感热通量、潜热通量、海洋热量净收支的时间变化特征及其与气象要素变化的关系.结果表明：西南季风爆发前后,太阳短波辐射、海面净辐射、潜热通量和海洋热量净收支变化特别强烈;通量变化受不同环境要素的影响：感热通量与海-气温差呈正相关关系,与气温呈明显的负相关关系.潜热通量与风速、海-气温差及海面水温均有正相关关系,其中与风速的关系最密切.动量通量（τ）主要随风速变化,它与风速（V）的关系可以表示为τ=000185V2-000559V+001248.     

Estimation of seasonal crop water consumption in a vineyard using Bowen ratio‐energy balance method

Information about seasonal crop water consumption is useful to develop the appropriate irrigation scheme. Measurements of energy balance components using the Bowen ratio method were made for a complete growing season at a vineyard in the arid region of northwest China. Vine in the experiment was furrow‐irrigated using a trellis system. The measured evapotranspiration was compared with estimates using the soil water balance method. It is shown that the Bowen ratio method provided accurate estimates of evapotranspiration from the vineyard and this requires that the Bowen ratio system is appropriately installed. The energy balance components showed typical diurnal pattern with peaks that occurred around the midday, except for the ground heat flux which delayed its peak by 2–3 h. The sensible heat flux was greater than the latent heat flux and followed the net radiation closely. The ratio of the latent heat flux to net radiation was low in the early growing season and increased over time. Under the limited irrigation experienced in the vineyard, the latent heat flux was controlled by available soil moisture and the total evapotranspiration in the growing season was 253 mm. The seasonal progression of the crop coefficient is similar to that reported in the literature, with the maximum occurring during the month of September. The crop coefficient can be estimated as a non‐linear function of day of year (DOY) and used to estimate evapotranspiration from vineyards in the region. Copyright © 2007 John Wiley & Sons, Ltd.     

Evaluation of energy balance closure adjustment methods by independent evapotranspiration estimates from lysimeters and hydrological simulations

Non‐closure of the surface energy balance is a frequently observed phenomenon of hydrometeorological field measurements, when using the eddy‐covariance method, which can be ascribed to an underestimation of the turbulent fluxes. Several approaches have been proposed in order to adjust the measured fluxes for this apparent systematic error. However, there are uncertainties about partitioning of the energy balance residual between the sensible and latent heat flux and whether such a correction should be applied on 30‐min data or longer time scales. The data for this study originate from two grassland sites in southern Germany, where measurements from weighable lysimeters are available as reference. The adjusted evapotranspiration rates are also compared with joint energy and water balance simulations using a physically based distributed hydrological model. We evaluate two adjustment methods: the first one preserves the Bowen ratio and the correction factor is determined on a daily basis. The second one attributes a smaller portion of the residual energy to the latent heat flux than to the sensible heat flux for closing the energy balance for every 30‐min flux integration interval. Both methods lead to an improved agreement of the eddy‐covariance based fluxes with the independent lysimeter estimates and the physically based model simulations. The first method results in a better comparability of evapotranspiration rates, and the second method leads to a smaller overall bias. These results are similar between both sites despite considerable differences in terrain complexity and grassland management. Moreover, we found that a daily adjustment factor leads to less scatter than a complete partitioning of the residual for every half‐hour time interval. The vertical temperature gradient in the surface layer and friction velocity were identified as important predictors for a potential future parameterisation of the energy balance residual.