均匀裸土地表土壤热通量计算方法对比及对能量闭合的影响

利用"内蒙古微气象观测蒸发试验"的观测资料,对6种地表土壤热通量计算方法(Plate Cal法、TDEC法、谐波法、热传导对流法、振幅法和相位法)进行比较,检验了6种方法在不同干湿地表状况下的适用性,并研究了6种方法计算地表土壤热通量的差异以及对地表能量闭合度的影响。结果表明:一般情况下,Plate Cal法计算的2 cm土壤热通量与观测值最接近,计算结果的均方差为6.9 W/m2。在不同干湿地表状况下,干燥和降水条件下适合使用Plate Cal法,计算结果的均方差分别为14.0 W/m2和30.1 W/m2;湿润条件下适合使用谐波法,计算结果的均方差为21.4 W/m2。6种方法计算的地表土壤热通量存在明显差别,最大相差178.6 W/m2,不同方法计算地表土壤热通量的最大差值超过25 W/m2的时次占样本的96.3%。不同方法计算地表土壤热通量的差异对地表能量闭合度的大小有明显影响,但不影响近地层能量闭合度随湍流混合增强而增大的规律。     

土壤热异常对地表能量平衡影响初探

将来自土壤深部的热通量引入off line的陆面过程模式 (NCAR—LSM ) ,通过长达 2a的数值试验对比分析了它对各层次土壤温度和地表能量平衡的影响。　　在土壤底部引入 5W /m2 的热通量使底层土壤显著升温 ,但升温随着接近表层而迅速衰减。积分 3个月后 ,由地下进入地表的热流量增幅可达 1W/m2 以上 ,并持续增大到 5W /m2 ,地表最大升温约 0 .5K ,同时地表感热、蒸发潜热及长波辐射通量均有 1W /m2 左右的正异常 ;若将土壤热传导系数放大一个量级以加速热量交换 ,则地表升温提高到 1K以上 ,长波辐射增加 3W /m2 以上 ,超过了气溶胶全球平均的辐射效应。结果表明 :一定量值的土壤热异常对地表能量平衡和短期气候变化 (10 -1～ 10 1a)有着不可忽略的影响。同时 ,深入的资料分析、完善的陆面过程模式以及它与大气模式的耦合试验也是亟待进行的相关工作。     

土壤热异常影响地表能量平衡的个例分析和数值模拟

The statistical relationship between soil thermal anomaly and short-term climate change is presented based on a typical case study. Furthermore, possible physical mechanisms behind the relationship are revealed through using an off-line land surface model with a reasonable soil thermal forcing at the bottom of the soil layer.In the first experiment, the given heat flux is 5 W m-2 at the bottom of the soil layer (in depth of 6.3 m)for 3 months, while only a positive ground temperature anomaly of 0.06℃ can be found compared to the control run. The anomaly, however, could reach 0.65℃ if the soil thermal conductivity was one order of magnitude larger. It could be even as large as 0.81℃ assuming the heat flux at bottom is 10 W m-2. Meanwhile, an increase of about 10 W m-2 was detected both for heat flux in soil and sensible heat on land surface, which is not neglectable to the short-term climate change. The results show that considerable response in land surface energy budget could be expected when the soil thermal forcing reaches a certain spatial-tem poral scale. Therefore, land surface models should not ignore the upward heat flux from the bottom of the soil layer. Moreover, integration for a longer period of time and coupled land-atmosphere model are also necessary for the better understanding of this issue.     

西北干旱区荒漠戈壁陆面过程的数值模拟

首先利用“中国西北干旱区陆 气相互作用试验”2 0 0 0年 5～ 6月在甘肃敦煌进行的陆 气相互作用野外试验的观测资料 ,确定了西北干旱区荒漠戈壁的陆面过程参数 ,并用这些参数改进了已有的陆面过程模式。然后用该陆面过程模式对敦煌陆 气相互作用野外试验荒漠戈壁上的大气感热通量、潜热通量、摩擦速度以及净辐射、地表和土壤温度、土壤水份等重要陆面变量进行了模拟 ,结果表明 ,模拟值与观测值非常接近 ,这说明改进后的模式对干旱区陆面过程有较强的模拟能力     

江苏省人为热排放现状及未来变化趋势分析

依据1990~2013年江苏省能源消费统计资料和1990、1995、2000、2005、2010年的人口空间分布数据,估计江苏省人为热排放量、探讨其时空分布特征并预测其未来变化趋势。研究结果表明,20多年来江苏省的人为热排放量持续增长,从1990年全省平均的0.59 W/m~2增加到2013年的2.85 W/m~2。排放的空间分布也不均匀,总体上江苏南部地区的排放通量高于江苏北部。近些年江苏省的人为热排放已成为区域问题,高值区已连接成片,2010年江苏省大部分地区的人为热排放高于2.5 W/m~2,南部主要城市排放通量大于10 W/m~2、北部城市也多大于5 W/m~2。江苏各城市的城区人为热排放通量稳步增长,2002年后增长加速、增量最高可达到2 W m~(-2) a~(-1)。在2030年和2050年江苏省的平均人为热排放通量将分别达到5.7 W/m~2和9.1 W/m~2,可能对中国东部的气候和大气环境产生重要影响。     

An error analysis of profile flux,stability, and roughness length measurements made in the marine atmospheric surface layer

An analytical error analysis of profile-derived fluxes of heat, moisture, and momentum, along with stability and roughness length, is performed using the accuracies of the constituent temperature, humidity, and wind speed measurements. Five experiments, representing more than two thirds of the existing marine profile data presently contained in the literature, are compared. Much of the profile data examined was used to develop the transfer coefficients presently employed by a large number of competing bulk aerodynamic flux schemes. Depending upon the experiment, typical profile-method measurement errors were found to range from 15 to 35% for a sensible heat flux of ± 10 W m^-2, from 15 to 105% for a latent heat flux of ± 100 W m^-2, from 10 to 40% for a stress of 0.05 N m^-2, from 15 to 60% for a Monin-Obukhov stability of ± 0.05, and from 25 to 100% for a roughness length of 2 × 10^-4 m. Smaller magnitude flux values were found to contain typical errors as large as 100% for sensible heat flux, 300% for latent heat flux, and 60% for stress.     

Linking the Atmospheric Boundary Layer to the Amundsen Gulf Sea-Ice Cover: A Mesoscale to Synoptic-Scale Perspective from Winter to Summer 2008

The link between the sea-ice cover of the Amundsen Gulf and the overlying atmospheric boundary layer was explored on a weekly timestep from winter to summer 2008. The total sea-ice cover was around 97% (3% leads) from 7 January to 21 April. From 28 April to 12 May, the total sea-ice cover approached 100%. From May 19, the total sea-ice declined rapidly to its July minimum of 3%. During the winter, a turbulent internal boundary layer (IBL), attributed to the upward flux of sensible heat (mean = 46 W m⁻²), was present in most of the mean daily potential temperature profiles. The mean latent heat flux was 1.7 Wm⁻². A turbulent IBL was also present in most of the mean daily profiles for early spring. Surface fluxes were not estimated. During late spring and early summer, a stable IBL, attributed to the downward flux of sensible heat (mean = −19 W m⁻²), was present in most of the potential temperature profiles. Both downward and upward fluxes of latent heat occurred in this period (means = −3.3 and 1.1 W m⁻²). The sensible heat flux estimates are consistent with the results of others; however, the latent heat flux estimates may be too small due to condensation/deposition within the IBL. The unconsolidated nature of the pack ice in the Amundsen Gulf, and the low sea-surface temperatures following break-up, were critical factors controlling the presence and type of IBL.     

Influence of atmospheric relative humidity on ultraviolet flux and aerosol direct radiative forcing: Observation and simulation

The atmospheric aerosols can absorb moisture from the environment due to their hydrophilicity and thus affect atmospheric radiation fluxes. In this article, the ultraviolet radiation and relative humidity (RH) data from ground observations and a radiative transfer model were used to examine the influence of RH on ultraviolet radiation flux and aerosol direct radiative forcing under the clear-sky conditions. The results show that RH has a significant influence on ultraviolet radiation because of aerosol hygroscopicity. The relationship between attenuation rate and RH can be fitted logarithmically and all of the R² of the 4 sets of samples are high, i.e. 0.87, 0.96, 0.9, and 0.9, respectively. When the RH is 60%, 70%, 80% and 90%, the mean aerosol direct radiative forcing in ultraviolet is ?4.22W m^?2, ?4.5W m^?2, ?4.82W m^?2 and ?5.4W m^?2, respectively. For the selected polluted air samples the growth factor for computing aerosol direct radiative forcing in the ultraviolet for the RH of 80% varies from 1.19 to 1.53, with an average of 1.31.     

青藏高原湿地土壤冻结、融化期间的陆面过程特征

利用青藏高原中部玉树隆宝湿地2015年7月-2016年7月的观测资料,分析了土壤冻结、融化前后土壤温、湿度和地表能量收支特征,结果表明：冻土持续时期为12月至次年4月,深层土壤的冻结较浅层土壤滞后,融化过程快于冻结过程,5-40 cm土壤全部冻结历时51 d,全部融化历时19 d。土壤体积含水量年变化幅度达0.6 m³/m³。冻结过程5-40 cm土壤体积含水量下降,融化过程5-10 cm土壤体积含水量升高。土壤冻结之后,感热通量白天的值升高,潜热通量白天的值降低,净辐射和土壤热通量均降低,土壤热通量日变化幅度增大。土壤融化之后,潜热通量、净辐射和土壤热通量白天的值升高。地表反照率、鲍恩比、土壤热导率和土壤热扩散率冻结后增大融化后减小,土壤热容量冻结后减小融化后增大。     

Radiative surface temperature and energy balance of a wheat canopy

The sensible heat loss from a stand of winter wheat was calculated from radiometric measurements of crop surface temperature, measurements of air temperature, and an atmospheric resistance to momentum transfer; corresponding latent heat flux was obtained through the energy balance equation. These estimates of sensible and latent heat were compared with fluxes from the Bowen Ratio method. When radiative temperature was derived using a measured canopy emissivity of 0.98, calculations of sensible heat flux were systematically 50–100 W m^-2 less than Bowen Ratio values. The two techniques agreed more closely when an apparent emissivity of 0.96 was used with an apparent reflectivity of 0.03. The mean difference between the estimates of latent heat flux was then -16 ± 32 W m^-2.The surface temperature method showed less systematic error in comparison with the Bowen Ratio values than did estimates using the aerodynamic method.On leave from: University of Nottingham, School of Agriculture, Loughborough LE12 5RD.     

Airborne Investigation Of Arctic Boundary-Layer Fronts Over The Marginal Ice Zone Of The Davis Strait

Three aircraft-based studies of boundary-layer fronts (BLFs) werecarried out during the experiment KABEG in April 1997near the sea-ice edge over the Davis Strait. The zone of strongestcross-front horizontal gradients showed a typical length scaleof 20 km, while the along-front scale was observed to beseveral hundreds of kilometres.The observed BLFs were stronger than the few previously reportedcases. Horizontal gradients of potential temperature and specifichumidity ranged up to 3 K or 0.25 g kg^-1over 20 km, respectively.Low-level winds were around 15 m s^-1 parallel to the ice edge.The capping inversion sloped from between250 and 400 m over sea ice to between 400 and 700 m over ocean.For two BLF cases turbulent fluxes and energy budgets are calculated.Turbulent energy fluxes show a factor 2 to 3 contrast acrossthe ice edge and range from 15 to 50 W m^-2 over sea iceand from 50 to 100 W m^-1 over open ocean.The mean boundary-layer energy budgets are dominated bycold, dry horizontal advection, which is exceededby vertical heat flux convergence.The momentum budgets are dominated by pressure gradient force,Coriolis force and momentum flux divergence.     

Evaluation of Mediterranean Sea water and heat budgets simulated by an ensemble of high resolution regional climate models

Air-sea heat and freshwater water fluxes in the Mediterranean Sea play a crucial role in dense water formation. Here, we compare estimates of Mediterranean Sea heat and water budgets from a range of observational datasets and discuss the main differences between them. Taking into account the closure hypothesis at the Gibraltar Strait, we have built several observational estimates of water and heat budgets by combination of their different observational components. We provide then three estimates for water budget and one for heat budget that satisfy the closure hypothesis. We then use these observational estimates to assess the ability of an ensemble of ERA40-driven high resolution (25 km) Regional Climate Models (RCMs) from the FP6-EU ENSEMBLES database, to simulate the various components, and net values, of the water and heat budgets. Most of the RCM Mediterranean basin means are within the range spanned by the observational estimates of the different budget components, though in some cases the RCMs have a tendency to overestimate the latent heat flux (or evaporation) with respect to observations. The RCMs do not show significant improvements of the total water budget estimates comparing to ERA40. Moreover, given the large spread found in observational estimates of precipitation over the sea, it is difficult to draw conclusions on the performance of RCM for the freshwater budget and this underlines the need for better precipitation observations. The original ERA40 value for the basin mean net heat flux is ?15 W/m² which is 10 W/m² less than the value of ?5 W/m² inferred from the transport measurements at Gibraltar Strait. The ensemble of heat budget values estimated from the models show that most of RCMs do not achieve heat budget closure. However, the ensemble mean value for the net heat flux is ?7 ± 21 W/m², which is close to the Gibraltar value, although the spread between the RCMs is large. Since the RCMs are forced by the same boundary conditions (ERA40 and sea surface temperatures) and have the same horizontal resolution and spatial domain, the reason for the large spread must reside in the physical parameterizations. To conclude, improvements are urgently required to physical parameterizations in state-of-the-art regional climate models, to reduce the large spread found in our analysis and to obtain better water and heat budget estimates over the Mediterranean Sea.     

TropFlux: air-sea fluxes for the global tropical oceans—description and evaluation

In this paper, we evaluate several timely, daily air-sea heat flux products (NCEP, NCEP2, ERA-Interim and OAFlux/ISCCP) against observations and present the newly developed TropFlux product. This new product uses bias-corrected ERA-interim and ISCCP data as input parameters to compute air-sea fluxes from the COARE v3.0 algorithm. Wind speed is corrected for mesoscale gustiness. Surface net shortwave radiation is based on corrected ISCCP data. We extend the shortwave radiation time series by using “near real-time” SWR estimated from outgoing longwave radiation. All products reproduce consistent intraseasonal surface net heat flux variations associated with the Madden-Julian Oscillation in the Indian Ocean, but display more disparate interannual heat flux variations associated with El Ni?o in the eastern Pacific. They also exhibit marked differences in mean values and seasonal cycle. Comparison with global tropical moored buoy array data, I-COADS and fully independent mooring data sets shows that the two NCEP products display lowest correlation to mooring turbulent fluxes and significant biases. ERA-interim data captures well temporal variability, but with significant biases. OAFlux and TropFlux perform best. All products have issues in reproducing observed longwave radiation. Shortwave flux is much better captured by ISCCP data than by any of the re-analyses. Our “near real-time” shortwave radiation performs better than most re-analyses, but tends to underestimate variability over the cold tongues of the Atlantic and Pacific. Compared to independent mooring data, NCEP and NCEP2 net heat fluxes display ~0.78 correlation and >65?W?m^?2 rms-difference, ERA-I performs better (~0.86 correlation and ~48?W?m^?2) while OAFlux and TropFlux perform best (~0.9 correlation and ~43?W?m^?2). TropFlux hence provides a useful option for studying flux variability associated with ocean–atmosphere interactions, oceanic heat budgets and climate fluctuations in the tropics.     

麻多高寒湿地冻结过程中土壤热通量变化特征分析

准确量化高寒湿地下垫面冻结过程中土壤热通量的变化特征,对认识高寒湿地—大气间水热交换过程有重要的科学意义。本文利用中国科学院麻多气候与环境综合观测站2014年5月至2015年5月的观测资料,分析了下垫面冻结过程中土壤热通量变化特征,探讨了冻结潜热对土壤热通量的贡献。基于温度积分计算土壤热通量的算法,指出在计算冻结过程中的土壤热通量时,需要同时考虑土壤热通量板以上的土壤热贮存及热通量板以上的冻结潜热。研究表明:（1）冻结锋面形成后,锋面所在深度土壤体积含水量迅速降低,锋面以下土壤热通量接近于零,土壤液态水开始冻结,冻结潜热向上穿过热通量板所在土壤层;降水下渗土壤后冻结所释放的潜热能使次日凌晨5 cm深度土壤热通量接近于零。（2）季节性冻结期,凌晨气温较高时穿过5 cm土壤层的向上土壤热通量很小,可能是由表层土壤发生了日冻融循环所致。土壤水释放的冻结潜热使土壤温度波动减弱并维持在冰点附近。高寒湿地下垫面仅在很浅的表层发生日冻融循环,无法通过5 cm土壤温度资料判断下垫面循环出现日期。（3）加入冻结潜热项,土壤热通量的计算值与实测值之间的均方根误差将会从11.5 W m-2下降到6.2 W m-2。以上研究结果对认识寒区陆面过程有重要的贡献。     

THE ENERGY BUDGETS UNDER DIFFERENT SYNOPTIC CONDITIONS OVER HUAIHE RIVER BASIN DURING HUBEX FIELD OBSERVATION PERIODS IN 1999*

In different synoptic conditions and at different time scales,the analysis of the energy budgets by Bowen Ratio Method and Bulk Schemes over Huaihe River Basin during the field observation periods of HUBEX in 1999 shows that,(1) the averaged latent heat flux is an order of magnitude more than the averaged sensible heat flux during the observation period:(2) the variation of totalcloud amount is out of phase with the terms of energy budgets except for the downward longwave radiation which maybe is related to the cloud's height and class:(3) the values of sensible and latent heat fluxes are small during rain episodes,but thereafter,the values become high and then up to maximum.It is similar to the other terms of the energy budgets except for the downward longwave radiation.The diurnal variation of energy budgets indicates that the daytime precipitation exerts great influence to the energy budgets,but the nighttime precipitation makes little influence;(4) the variation of the latent heat flux is in phase with the evaporation,which indicates that the latent heat flux calculated by bulk schemes is reliable:(5) the means of the sensible and latent heat flux and momentum flux by bulk schemes for the time period from May to August are,respectively,30.71W/m².116.81W/m².2.86×10^-2N/m² in 1998 and 30.28W/m²,107.35W/m²,2.74×10^-2N/m² in 1999.The values of these two years are similar.During summer in 1999 the magnitude and activity of sensible heat flux are strongest in June and those of the latent heat flux are in August.     

A comparison of solar radiative flux above clouds from MODIS with BALTIMOS regional climate model simulations

A comparison study for the solar radiative flux above clouds is presented between the regional climate model system BALTEX integrated model system (BALTIMOS) and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite observations. For MODIS, an algorithm has been developed to retrieve reflected shortwave fluxes over clouds. The study area is the Baltic Sea catchment area during an 11-month period from February to December 2002. The intercomparison focuses on the variations of the daily and seasonal cycle and the spatial distributions. We found good agreement between the observed and the simulated data with a bias of the temporal mean of 13.6 W/m² and a bias of the spatial mean of 35.5 W/m². For summer months, BALTIMOS overestimates the solar flux with up to 90 W/m² (20%). This might be explained by the insufficient representation of cirrus clouds in the regional climate model.     

Divergence of turbulent fluxes in the surface layer: case of a coastal city

This study quantifies the processes that take place in the layer between the mean building height and the measurement level of an energy balance micrometeorological tower located in the dense old core of a coastal European city. The contributions of storage, vertical advection, horizontal advection and radiative divergence for heat are evaluated with the available measurements and with a three-dimensional, high-resolution meteorological simulation that had been evaluated against observations. The study focused on a summer period characterized by sea-breeze flows that affect the city. In this specific configuration, it appears that the horizontal advection is the dominant term. During the afternoon when the sea breeze is well established, correction of the sensible heat flux with horizontal heat advection increases the measured sensible heat flux up to 100 W m⁻². For latent heat flux, the horizontal moisture advection converted to equivalent latent heat flux suggests a decrease of 50 W m⁻². The simulation reproduces well the temporal evolution and magnitude of these terms.     

A cold air outbreak near Spitsbergen in springtime — Boundary-layer modification and cloud development

A moderate cold air outbreak from the Arctic ice over the warm West-Spitsbergen current on 15 and 16 May 1988 during the field experiment ARKTIS '88 is analysed using data from four aircraft and one research vessel.The downstream development of cloud coverage appears to depend sensitively on the moisture content above the inversion. The cloud amount determines the energy balance at the sea surface. Under daytime conditions and little cloud cover, energy is added to the ocean in spite of sensible and latent heat losses.The downstream temperature increase in the boundary layer is controlled by sensible heat flux and by longwave radiation cooling. The entrainment sensible heat flux is the dominating term in the region near the ice edge. The downstream moisture increase is controlled by surface evaporation. Condensation processes play no significant role.On 16 May 1988 cloud streets near the ice edge changed to closed cloud meanders in the downstream direction. The aspect ratio increased from 3 to around 10 over a distance of 200 km. In the cloud street region, the dynamical generation of turbulent kinetic energy due to wind shear at the tilted inversion was larger than the thermal generation.Cloud droplet concentration, mean droplet radius and liquid water content increased linearly with height. The maximum liquid water content was only 0.1 g/kg near the top of a 400 m thick closed cloud and clearly below the adiabatic value. The net longwave radiation flux decreased by 50 W/m² at cloud top and increased by 13 W/m² at cloud base.     

Estimation of the Anthropogenic Heat Release Distribution in China from 1992 to 2009

Stable light data from Defense Meteorological Satellite Program (DMSP)/Operational Linescan System (OLS) satellites and authoritative energy consumption data distributed by National Bureau of Statistics of China were applied to estimating the distribution of anthropogenic heat release in China from 1992 to 2009. A strong linear relationship was found between DMSP/OLS digital number data and anthropogenic heat flux density (AHFD). The results indicate that anthropogenic heat release in China was geographically concentrated and was fundamentally correlated with economic activities. The anthropogenic heat release in economically developed areas in northern, eastern, and southern China was much larger than other regions, whereas it was very small in northwestern and southwestern China. The mean AHFD in China increased from 0.07 W m-2 in 1978 to 0.28 W m-2 in 2008. The results indicate that in the anthropogenic heat-concentrated regions of Beijing, the Yangtze River Delta, and the Pearl River Delta, the AHFD levels were much higher than the average. The effect of aggravating anthropogenic heat release on climate change deserves further investigation.     

Modelling soil heat flux

A mathematical model to calculate soil heat flux in three steps is presented. In the first, an hourly air temperature based on the average daily temperature, using Fourier series coefficients is estimated. The estimated hourly air temperature constitutes an input variable for the second step of the model. In the second step, heat transfer principles, using the thermal properties of the soil in order to obtain a soil temperature profile in a 1-m-depth soil stratum, is applied. Finally, the results of the second stage are used to numerically calculate hourly heat flux in the soil. Correlation coefficients between observed and calculated hourly temperature values over the three summer months were 0.98, 0.97 and 0.96. Correlation coefficient for the entire study period between observed and estimated soil heat-flux values was 0.92 with a mean square error of 19.8 W m^–2.