共查询到18条相似文献，搜索用时 125 毫秒
1.
地表能量不平衡问题是近40年一直困扰微气象学界的重要难题.本文利用黄土高原定西干旱气象与生态环境试验站的相关数据,通过将湍流分解为相干结构部分和非相干结构部分,在涡动相关法中引入相干结构(Coherent structure,简称为CS)的贡献,探讨了CS在地表能量平衡中的作用.研究发现：(1)CS出现频次高,间歇性显著,在30 min平均时间中出现的数目为38个,出现时间与未出现时间分别占40%和60%左右;(2)CS对通量影响显著,引入CS贡献后,白天垂直动量通量、感热、潜热和湍流通量(感热与潜热之和)等4个通量计算的准确性均获得显著提高,分别提高达26%(0.01 m2·s-2)、24%(25.33 W·m-2)、31%(6.23 W·m-2)和30%(31.66 W·m-2).而不考虑CS的传统方法对这4个通量低估达19%、22%、21%和23%;(3)CS对4个通量的贡献分别为36%、41%、33%和50%;(4)传统方法得到的地表能量平衡闭合率EBR只有0.76、能... 相似文献
2.
水库或湖泊的热分层结构是其动力与环境过程的重要研究方面,虽然很多学者针对水体分层结构和演变机理开展了大量研究,但水体通过水-气界面与大气进行热交换的过程,各气象因子的贡献机理等研究成果还很缺乏。本文基于三峡水库香溪河库湾2019年3月-2020年2月期间的水温、水位及气象等监测数据,针对水-气界面热交换过程如何影响水温垂向结构及表层水体湍流混合作用开展研究。结果表明,(1)香溪河水体年内呈高温期分层、低温期混合的基本特征,高温期混合层深度小于8 m,低温期混合层深度超过30 m。(2)太阳短波辐射是香溪河水体的主要热源,潜热通量和长波辐射是香溪河水体的主要冷源,感热通量贡献极小。(3)香溪河平均风速较弱,约为1.6 m/s,主要通过增强潜热和感热通量的方式影响水体垂向稳定性结构特征,其机械扰动作用较弱。(4)表层水体湍能通量在高温期较低(10-7m3/s3量级),此时水体处于分层状态,风应力大概率主导表层水体湍流发育;低温期表层水体湍能通量较高(10-6 m3/s3<... 相似文献
3.
鄱阳湖夏季水热通量特征及环境要素影响分析 总被引：2，自引：2，他引：0
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. 相似文献
4.
利用三维非静力中尺度模式ARPS,对白洋淀地区水陆非均匀下垫面上大气边界层结构及其变动进行了模拟研究.结果表明,晴天弱背景下,白洋淀地区陆地大气比湿高于水域的情况发生在白天大部分时间内,是普遍存在的一种现象,该现象首先出现在近地层,然后不断向高空延伸,与水陆两种不同的下垫面特征密切相关.由于水陆下垫面的差异,导致水域感热和潜热通量全天较小,变化平稳,而陆地日间感热和潜热通量较大,且潜热高于感热.水陆两地近地层湍流运动状态存在较大差异,湍流输送在水陆比湿空间变动过程中起决定性作用.形成的局地环流同样影响着水陆比湿的空间变动,主要表现在环流上下支对近地层湍流发展以及水汽的垂直输送的影响.陆地上空水汽主要来源于土壤植被的蒸发蒸腾,而来自水域的仅占很少一部分. 相似文献
5.
大量近地层观测试验表明,利用涡动相关法观测的湍流通量小于近地层可利用能量,即近地层能量是不闭合的,这种不闭合度一般为20%甚至更高.而陆面过程模式是基于地气间能量平衡建立,并且模式中的湍流边界层参数化方案通常根据实际观测的湍流通量来确定,因此能量不闭合必将对陆面过程模式造成一定的影响.本文利用2007年春季SACOL站的近地层观测资料,依据能量守恒将能量不闭合中的残余能量通过波文比分配到观测的湍流通量中,即修正涡动相关法观测的湍流通量使得近地层能量达到平衡;之后分别利用观测和修正的湍流通量,建立了能量不闭合和闭合情形下的湍流参数化方案,借助陆面过程模式SHAW,通过数值模拟和对比分析方法考察近地层能量闭合度对陆面过程模式的影响.研究结果表明近地层能量闭合对陆面过程模式有显著的影响:在陆面过程数值模拟中,当应用近地层能量不闭合的湍流通量形成的湍流参数化方案时,陆面过程模式会明显高估地表长波辐射及土壤温度;但当应用修正湍流通量使得近地层能量达到闭合形成的湍流参数化方案后,在不改变任何地表土壤物理生化属性的情况下,陆面过程模式能较好地模拟地表长波辐射和土壤温度. 相似文献
6.
玉米生育期地表能量平衡的多时间尺度特征分析及不平衡原因的探索 总被引：4，自引：0，他引：4
能量不闭合是几乎所有地表通量观测研究中存在的问题．在能量平衡估算中,人们往往关注有效能量（感热和潜热之和）系统低于可利用能量（净辐射与土壤热通量之差）的统计结果,而忽视了有效能量大于可利用能量的“过闭合”样本存在及其对整体能量闭合率的贡献．利用2004年华北玉米生育期的观测资料,探讨了能量分量的时间同步性,认为各能量分量与净辐射的时间不同步是导致“过闭合”现象系统出现的原因．将有效能量位相提前半小时与可利用能量进行相关分析,有效减少了能量比率大于1和小于0．5的样本,提高了不同尺度的能量利用率．多种时间尺度的能量分配与转化规律分析显示,潜热在不同时间尺度上都是主要的能量消耗方式,能量闭合差随玉米的生长不断增大,长达7旬的时间超过感热,表明热量储存和光合耗能在玉米生育期能量平衡中具有重要作用． 相似文献
7.
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． 相似文献
8.
在2000年6-7月新疆阜康地区野外观测资料和美国宇航局Goddard地球观测系统资料同化系统计算相应时间能量收支基础上分析了夏季我国西部干旱地区辐射特征和能量收支。新疆阜康地区观测的夏季中午平均吸收辐射为664W/m^2左右，反照率为17%，夜间长波净辐射值为60W/m^2左右。模式计算的相应地区的辐射特征与观测结果相当接近。模式计算结果表明，夏季新疆、甘肃西部、内蒙一带为感热通量高值区，其最大值在华北、东北地区，其值可达300W/m^2。广大西北地区潜热通量都很低，其高值区在华东、华南、西藏东部和四川一带，最大值可达250-300W/m^2。 相似文献
9.
源区划分和质量过滤提高湖面涡动相关通量数据可靠性的同时,却降低了通量时间序列的连续性.为此,本文基于TensorFlow机器学习框架构建了一种超宽人工神经网络(ANN)模型.在选择输入ANN模型的特征变量信息时,我们采取了尽可能获取湍流输送过程中热力、动力学同步观测背景强迫信息的原则.通过ANN模型模拟通量的插补,本文实现了通量时间序列连续性的优化,插补后的羊卓雍错湖面通量数据的时间覆盖率从不足0.40提升至超过0.98.基于10次折叠交叉验证的ANN模型通量模拟性能检验则表明,各个检验组之间ANN模型的模拟误差波动较小,这显示出了较好的稳健性.具体地讲,感热通量、潜热通量和水汽通量原始观测平均值分别约为18.8 W/m~2、81.5 W/m~2和1.84 mmol/(s·m~2),10组交叉验证的插补感热通量、潜热通量和水汽通量平均绝对误差分别为5.4 W/m~2、15.7 W/m~2和0.35 mmol/(s·m~2).这表明本文所探索的ANN建模结构和同步观测变量筛选原则可更充分地利用观测点局地同步观测信息估算通量强度,有效地优化湍流通量数据的时间连续性,从而提升通量数据的可分析性. 相似文献
10.
地表土壤热通量是地表能量平衡的重要组成部分,对地表蒸散发的估算至关重要.利用土壤温湿度廓线观测资料基于热扩散方程计算地表土壤热通量,并通过冻土融化前后土壤液态水含量变化估算土壤含冰量,分析了土壤含冰量对土壤热通量的影响,旨在分析黑河流域典型下垫面(高山草地、农田和森林)地表土壤热通量的时空变化特征.研究结果表明:(1)黑河流域不同下垫面的地表土壤热通量有明显的日变化差异,日最大值时刻提前净辐射通量几分钟至几小时不等,这与土壤质地、湿度、热属性和植被覆盖度有关;(2)净辐射通量有显著的季节变化,一般夏季达最大值,冬季最小,地表土壤热通量也有明显的季节变化,但并不总是与净辐射通量变化保持一致,春季达最大值,夏季由于植被覆盖的原因反而降低;(3)地表土壤热通量占净辐射通量的比例因季节及下垫面不同而有差异,1月份月平均比值分别为:阿柔25.6%、盈科22.9%和关滩4.3%,7月份月平均比值分别为:阿柔2.3%、盈科1.6%和关滩0.3%;(4)冬季考虑了冰的热容量使得土壤热容量增加,土壤热存储增加,从而由热扩散方程计算的地表土壤热通量增加,使得能量平衡闭合率提高了4.3%. 相似文献
11.
《中国科学D辑(英文版)》2006,(Z2)
In order to discuss the values and daily variation characteristics of heat storage fluxes in a tropical seasonal rain forest in Xishuangbanna, the sensible and latent heat storage flux within air column, canopy heat storage flux, energy storage by photosynthesis and ground heat storage above the soil heat flux plate, as well as the ratios of these heat storage fluxes to the net radiation in the cool-dry, hot-dry and rainy season were compared and analyzed based on the observation data of carbon fluxes, meteorological factors and biomass within this tropical seasonal rain forest from January 2003 to December 2004. The findings showed that heat storage terms ranged significantly in the daytime and weakly in the nighttime, and the absolute values of sensible and latent heat storage fluxes were obviously greater than other heat storage terms in all seasons. In addition, the absolute values of total heat storage fluxes reached the peak in the hot-dry season, then were higher in the rainy season, and reached the minimum in the cool-dry season. The ratios of heat storage fluxes to net radiation generally decreased with time in the daytime, moreover, the sensible and latent heat storage dominated a considerable fraction of net radiation, while other heat storage contents occupied a smaller fraction of the net radiation and the peak value was not above 3.5%. In the daytime, the ratios of the total heat storage to net radiation were greater and differences in these ratios were distinct among seasons before 12:00, and then they became lower and differences were small among seasons after 12:00. The energy closure was improved when the storage terms were considered in the energy balance, which indicated that heat storage terms should not been neglected. The energy closure of tropical seasonal rain forest was not very well due to effects of many factors. The results would help us to further understand energy transfer and mass exchange between tropical forest and atmosphere. Moreover, they would supply a research basis for studying energy closure at other places. 相似文献
12.
Energy balance closure at ChinaFLUX sites 总被引：1，自引：0，他引：1
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. 相似文献
13.
Yuichiro Nakai Tomoki Sakamoto Tomomi Terajima Kenzo Kitamura Tomoki Shirai 《水文研究》1999,13(4):515-529
To evaluate the interactive effects of snow and forest on turbulent fluxes between the forest surface and the atmosphere, the surface energy balance above a forest was measured by the eddy correlation method during the winter of 1995–1996. The forest was a young coniferous plantation comprised of spruce and fir. The study site, in Sapporo, northern Japan, had heavy and frequent snowfalls and the canopy was frequently covered with snow during the study period. A comparison of the observed energy balance above the forest for periods with and without a snow‐covered canopy and an analysis using a single‐source model gave the following results: during daytime when the canopy was covered with snow, the upward latent heat flux was large, about 80% of the net radiation, and the sensible heat flux was positive but small. On the other hand, during daytime when the canopy was dry and free from snow, the sensible heat flux was dominant and the latent heat flux was minor, about 10% of the net radiation. To explain this difference of energy partition between snow‐covered and snow‐free conditions, not only differences in temperature but also differences in the bulk transfer coefficients for latent heat flux were necessary in the model. Therefore, the high evaporation rate from the snow‐covered canopy can be attributed largely to the high moisture availability of the canopy surface. Evaporation from the forest during a 60‐day period in midwinter was estimated on a daily basis as net radiation minus sensible heat flux. The overall average evaporation during the 60‐day period was 0·6 mm day−1, which is larger than that from open snow fields. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
14.
Land surface energy fluxes are required in many environmental studies, including hydrology, agronomy and meteorology. Surface energy balance models simulate microscale energy exchange processes between the ground surface and the atmospheric layer near ground level. Spatial variability of energy fluxes limits point measurements to be used for larger areas. Remote sensing provides the basis for spatial mapping of energy fluxes. Remote‐sensing‐based surface energy flux‐mapping was conducted using seven Landsat images from 1997 to 2002 at four contiguous crop fields located in Polk County, northwestern Minnesota. Spatially distributed surface energy fluxes were estimated and mapped at 30 m pixel level from Landsat Thematic Mapper and Enhanced Thematic Mapper images and weather information. Net radiation was determined using the surface energy balance algorithm for land (SEBAL) procedure. Applying the two‐source energy balance (TSEB) model, the surface temperature and the latent and sensible heat fluxes were partitioned into vegetation and soil components and estimated at the pixel level. Yield data for wheat and soybean from 1997 to 2002 were mapped and compared with latent heat (evapotranspiration) for four of the fields at pixel level. The spatial distribution and the relation of latent heat flux and Bowen ratio (ratio of sensible heat to latent heat) to crop yield were studied. The root‐mean‐square error and the mean absolute percentage of error between the observed and predicted energy fluxes were between 7 and 22 W m−2 and 12 and 24% respectively. Results show that latent heat flux and Bowen ratio were correlated (positive and negative) to the yield data. Wheat and soybean yields were predicted using latent heat flux with mean R2 = 0·67 and 0·70 respectively, average residual means of −4·2 bushels/acre and 0·11 bushels/acre respectively, and average residual standard deviations of 16·2 bushels/acre and 16·6 bushels/acre respectively (1 bushel/acre ≈ 0·087 m3 ha−1). The flux estimation procedure from the SEBAL‐TSEB model was useful and applicable to agricultural fields. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
15.
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. 相似文献
16.
Sensitivity of model parameterizations for simulated latent heat flux at the snow surface for complex mountain sites 总被引：1，自引：0，他引：1 
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下载免费PDF全文 The snowcover energy balance is typically dominated by net radiation and sensible and latent heat fluxes. Validation of the two latter components is rare and often difficult to undertake at complex mountain sites. Latent heat flux, the focus of this paper, is the primary coupling mechanism between the snow surface and the atmosphere. It accounts for the critical exchange of mass (sublimation or condensation), along with the associated snowcover energy loss or gain. Measured and modelled latent heat fluxes at a wind‐exposed and wind‐sheltered site were compared to evaluate variability in model parameters. A well‐tested and well‐validated snowcover energy balance model, Snobal, was selected for this comparison because of previously successful applications of the model at these sites and because of the adjustability of the parameters specific to latent heat transfer within the model. Simulated latent heat flux and snow water equivalent (SWE) were not sensitive to different formulations of the stability profile functions associated with heat transfer calculations. The model parameters of snow surface roughness length and active snow layer thickness were used to improve latent heat flux simulations while retaining accuracy in the simulation of the SWE at an exposed and sheltered study site. Optimal parameters for simulated latent heat flux and SWE were found at the exposed site with a shorter roughness length and thicker active layer, and at the sheltered site with a longer roughness length and thinner active layer. These findings were linked to physical characteristics of the study sites and will allow for adoption into other snow models that use similar parameters. Physical characteristics of wind exposure and cover could also be used to distribute critical parameters in a spatially distributed modelling domain and aid in parameter selection for application to other watersheds where detailed information is not available. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
17.
Observational estimation of heat budgets on drifting ice and open water over the Arctic Ocean 总被引：9，自引：0，他引：9
It is of major scientific interests to determine the parameters of momentum, heat and vapor exchange in the planetary boundary layer in order to study the effects of ocean-ice-atmosphere interactions and their feedback mechanisms on global climate[1]. Lin… 相似文献
18.
Spatial distribution of surface energy fluxes over the Loess Plateau in China and its relationship with climate and the environment 总被引：1，自引：0，他引：1
Qiang Zhang Liang Zhang Jing Huang LiYang Zhang WenYu Wang Sha Sha 《中国科学:地球科学(英文版)》2014,57(9):2135-2147
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. 相似文献