荒漠下垫面陆面过程和大气边界层相互作用敏感性实验

建立了一个研究荒漠下垫面陆面物理过程与大气边界层相互作用的模式. 模拟了荒漠下垫面的土壤环境物理、地面热量通量、蒸发、蒸散及大气边界层结构特征.并对主要的环境物理参数进行了敏感性实验.结果表明,本模式能合理地模拟荒漠下垫面地表热量平衡、土壤体积含水量、地表植被蒸发散阻抗、地表水汽通量日变化和湍流交换系数、湍流动能、位温和比湿廓线等.该模式还可进一步应用于研究区域陆面物理过程与大气边界层相互作用机制,及与中尺度大气模式耦合用于区域环境生态和气候的研究.     

水体对湍流交换系数的影响*

本文根据边界层理论,计算水体附近湍流交换系数的变化。计算结果表明:白天整个水体上的湍流交换系数都比陆面上同高度的要小,并且有二个低值中心:一个靠近水面,另一个在约100m高度;夜间靠近水面的那层空气的湍流交换系数仍较小,但其上方的湍流交换系数要比陆面上大。水面上的湍流交换系数日变化小于陆面上,特别是靠近水面那层空气日变幅很小。同时指出:水陆间粗糙度的差异和稳定度的差异控制着水陆湍流交换系数的差异;前者是稳定的;后者有周期性的变化。     

城市化过程中下垫面改变对大气环境的影响

城市化发展,特别是下垫面特征的改变,对大气环境的外强迫是当前大气环境领域研究的热点问题。下垫面特征变化导致不同尺度气象场发生变化,而气象条件又决定着大气污染物的迁移转化。为了深入探讨这个问题,文章首先从3个方面总结了相关研究：1）城市气候的基本特征及其形成的内在机制;2）不同尺度下的城市污染气象学特征;3）定量描述城市下垫面地-气作用模式的相关进展。之后进一步综述了利用数值模式方法模拟城市化过程中下垫面变迁对大气环境（包括气象条件及空气质量）影响方面的研究进展。最后利用中尺度大气模式WRF/Chem和过程分析方法研究了中国东部地区城市下垫面扩张对臭氧（O3）和一氧化碳（CO）空间分布的影响。模拟结果显示：在人为源排放不变的情况下,城市下垫面扩张使得近地面和1~3 km高处的O3,以及距地面1~2 km高处的CO体积分数增大;但近地CO体积分数下降。     

荒漠区粗糙度长度的确定及在模式中的应用

利用2005年进行的“绿洲系统能量与水分循环补充观测试验”第3阶段的观测资料计算了金塔试验区内戈壁和沙漠的动力学和热力学粗糙度长度,沙漠和戈壁的动力粗糙度长度分别为1.81×10-3m和1.64×10-3 m,与黑河试验结果基本一致,均为沙漠的动力粗糙度大于戈壁。试验区内沙漠和戈壁的热力粗糙度长度分别是0.28×10-3 m和0.62×10-3 m。将计算得到的粗糙度长度代入Noah陆面模式,模拟的戈壁、沙漠上的地表温度和感热通量同观测值较为一致,优于原粗糙度长度的模拟结果,大大提高了该模式在沙漠、戈壁特殊区域的模拟能力,有利于将耦合了Noah模式的中尺度模式更好地应用到绿洲系统的研究中。     

黄土高原不同气候区裸地水、热特征对比

为了更好地理解陆地表面水、热通量的空间差异,利用2009年和2010年1月黄土高原陆面过程观测试验（LOPEX）的陆面过程资料,对比分析了不同气候区主要地表水、热通量特征。结果表明：半干旱区的定西在近地层气象要素、土壤湿度、动量通量、地表能量及CO2通量等主要陆面特征物理量与半湿润区的平凉、庆阳差异明显;气候背景相接近的平凉、庆阳的主要陆面特征量比较接近。虽然地形、地势、海拔、下垫面影响因子也是影响陆面特征的重要因素,但是气候背景差异愈明显,陆面特征差异也愈大,即一个地区的气候背景是陆面过程特征的主要决定因子,对陆面特征产生综合影响,而地形、地貌只对一个或几个陆面物理量有影响。     

城市地表热通量遥感反演及与土地类型的关系(英文)

Using ASTER(Advanced Spaceborne Thermal Emission and Reflection Radiome-ter) infrared remote sensing data we inversed the parameters of urban surface heat fluxes applying the PCACA model and theoretical position algorithm,and then we analyzed the in-fluence of different land use types on the surface heat fluxes and energy balance.In this study,Kumagaya,a city in Saitama Prefecture,Japan,was selected as the experimental area.The result shows that the PCACA model is feasible for the surface heat fluxes estimation in urban areas because this model requires less parameters in the procedure of heat fluxes estimation in urban areas with complicated surface structure and can decrease the uncertainty.And we found that different land-use types have indicated the height heterogeneity on the surface heat fluxes significantly.The magnitudes of Bowen ratio in descending order are industrial,residential,transportation,institutional,dry farmland,green space,and water body.Under the same meteorological condition,there are distinct characteristics and regional differences in Bowen ratios among different surface covers,indicating higher sensible heat flux and lower latent heat flux in the urban construction land,while lower sensible heat flux and higher latent heat flux in the vegetation-covered area,the outskirt of the urban area.The increase of urban impervious surface area caused by the urban sprawl can enlarge the sensible heat flux and the Bowen ratio,so that it causes the increasing of urban surface temperature and air tem-perature,which is the mechanism of the so-called heat island effect.     

Characteristics of land-atmosphere energy and turbulent fluxes over the plateau steppe in central Tibetan Plateau

The land-atmosphere energy and turbulence exchange is key to understanding land surface processes on the Tibetan Plateau(TP). Using observed data for Aug. 4 to Dec. 3, 2012 from the Bujiao observation point(BJ) of the Nagqu Plateau Climate and Environment Station(NPCE-BJ), different characteristics of the energy flux during the Asian summer monsoon(ASM) season and post-monsoon period were analyzed. This study outlines the impact of the ASM on energy fluxes in the central TP. It also demonstrates that the surface energy closure rate during the ASM season is higher than that of the post-monsoon period. Footprint modeling shows the distribution of data quality assessments(QA) and quality controls(QC) surrounding the observation point. The measured turbulent flux data at the NPCE-BJ site were highly representative of the target land-use type. The target surface contributed more to the fluxes under unstable conditions than under stable conditions. The main wind directions(180° and 210°) with the highest data density showed flux contributions reaching 100%, even under stable conditions. The lowest flux contributions were found in sectors with low data density, e.g., 90.4% in the 360° sector under stable conditions during the ASM season. Lastly, a surface energy water balance(SEWAB) model was used to gap-fill any absent or corrected turbulence data. The potential simulation error was also explored in this study. The Nash-Sutcliffe model efficiency coefficients(NSEs) of the observed fluxes with the SEWAB model runs were 0.78 for sensible heat flux and 0.63 for latent heat flux during the ASM season, but unrealistic values of-0.9 for latent heat flux during the post-monsoon period.     

沙漠下垫面地面温度及能量收支的BATS模式参数化改进

利用陆面过程模式BATS,引入地表发射率及两种大气发射率参数化方案,同时引入不同的地表粗糙度参数化方案,对比各种参数化方案对沙漠下垫面地面温度及能量收支的模拟状况。结果表明：采用Van Bavel等发展的地表发射率及Chung等发展的大气发射率方案可以明显改进地面温度及向上长波辐射的模拟,Chung等方案在夜间与正午的模拟效果更好,减小了1 ℃左右的地面温度模拟偏差,减小了10 W·m^-2左右的向上长波辐射模拟偏差。晴天地面温度及向上长波辐射的模拟结果优于阴天。利用Zhang等发展的裸土粗糙度参数化方案也会提高模式对地表感热通量模拟的准确性。     

基于DEM的月球雨海地区粗糙度研究

月球表面粗糙度是揭示月表地貌形态空间分异特征的重要指标,并在一定程度上映射月表地貌的形成与演化机理。运用基于中国“嫦娥一号”卫星获取的DEM数据,提取月球雨海地区的月表粗糙度,并在月球正面地质图数据辅助下,分析月表粗糙度分布特征及其与地质单元岩性以及地质年龄的关系。结果显示:月球雨海地区的粗糙度与地质单元岩性存在较强相关关系,且随着地质年龄的增长,玄武岩单元的粗糙度呈现增大的趋势。此外,在小于7 km的尺度范围内,雨海地区受持续撞击作用的影响,Hurst指数分布在0.7~0.9之间,地形较为粗糙;在更大尺度上,由于受到火山熔岩流充填机制的控制,Hurst指数不断减小,地形不断趋于平缓。     

土地利用类型转换对地表能量平衡和气候的影响——基于SiB2模型的模拟结果

利用SiB2 模型对中国东北地区农田、草地和森林3 种土地利用类型的地表能量平衡过程展开研究,分析不同土地利用类型对生物地球物理参数（反照率和粗糙度）、能量平衡（净辐射、潜热和显热）和气候（冠层温度）的影响。结果表明：①模型模拟的地表能量平衡与实测数据的年变化动态相似（R²>0.42）,差值保持在±30 W/m²,温度在±4 ℃。②利用相同气象数据模拟不同土地利用类型通过生物地球物理过程对地表能量平衡和气候的影响,发现森林吸收的净辐射最高且主要用于潜热分配,农田的净辐射最低且主要用于显热分配,草地净辐射和能量分配居中。③生态系统获得的净辐射主要受反照率的影响,净辐射分配受叶面积指数的调节。④冠层温度（℃）受反照率和净辐射在潜热和显热间分配的相对重要性的影响：年平均值为森林（7.7）>农田（7.64）>草地（6.67）。⑤降水对模拟结果有显著影响,是森林模拟差异的主要原因。在不同土地利用类型中,降水增加土壤水分,净辐射更多分配到潜热,较少分配到显热,降低冠层温度。     

戈壁风蚀面与植被覆盖面地表性质粗糙度长度的确定

以Monin-Obukhov相似性理论为基础, 利用量纲分析法分别推导出不同层结稳定度下确定戈壁风蚀面与植被覆盖面空气动力学参数的物理模型, 并利用该模型研究了粗糙度长度与粗糙元性质, 流经近地层流体特征以及大气层结稳定度之间的关系。得出以下结论: 戈壁风蚀面上空气动力学粗糙度长度与砾石粒径、高度、覆盖度、自由风速、摩擦速度以及大气层结稳定度有关; 植被覆盖面空气动力学粗糙度长度取决于植被类型、植被高度、覆盖度、零平面位移高度、自由风速、摩擦速度以及大气层结稳定度。     

南极中山站附近冰盖近地面层湍流参数的观测研究

利用2007/2008年中国第24次南极考察队在南极中山站附近冰盖上观测试验获得的湍流脉动及相关资料,对原始资料通过坐标旋转订正后,应用涡动相关法计算分析了冰盖近地面层的湍流强度(I)、稳定度参数(z/L)、摩擦速度(u*)、拖曳系数(Cd)、地表粗糙度(z0)及动量通量(τ)和感热通量(H),并与空气动力学方法的计算结果进行对比。结果表明,Louis方案能够较好地模拟近地面层湍流通量;在平均状态下,全天雪面以感热形式从大气获得净的能量;近中性层结下地表粗糙度z0为4.54×10-4m,拖曳系数Cd=1.7×10-3,在非中性条件下,稳定度越小Cd越大,反之,则稳定度越大Cd越小。     

Winter estimation of surface roughness length over eastern Qinghai-Tibetan Plateau

Based on the Monin-Obukhov similarity theory, a scheme was developed to calculate surface roughness length. Surface roughness length over the eastern Qinghai-Tibetan Plateau during the winter season was then estimated using the scheme and eddy covariance measurement data. Comparisons of estimated and measured wind speeds show that the scheme is feasible to calculate surface roughness length. The estimated roughness lengths at the measurement site during unfrozen,frozen and melted periods are 3.23×10-3, 2.27×10-3 and 1.92×10-3 m, respectively. Surface roughness length demonstrates a deceasing trend with time during the winter season. Thereby, setting the roughness length to be a constant value in numerical models could lead to certain degree of simulation errors. The variation of surface roughness length may be caused by the change in land surface characteristic.     

Estimation of ground heat flux and its impact on the surface energy budget for a semi-arid grassland

Three approaches, i.e., the harmonic analysis (HA) technique, the thermal diffusion equation and correction (TDEC) method, and the calorimetric method used to estimate ground heat flux, are evaluated by using observations from the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) in July, 2008. The calorimetric method, which involves soil heat flux measurement with an HFP01SC self-calibrating heat flux plate buried at a depth of 5 cm and heat storage in the soil between the plate and the surface, is here called the ITHP approach. The results show good linear relationships between the soil heat fluxes measured with the HFP01SC heat flux plate and those calculated with the HA technique and the TDEC method, respectively, at a depth of 5 cm. The soil heat fluxes calculated with the latter two methods well follow the phase measured with the HFP01SC heat flux plate. The magnitudes of the soil heat flux calculated with the HA technique and the TDEC method are close to each other, and they are about 2 percent and 6 percent larger than the measured soil heat flux, respectively, which mainly occur during the nighttime. Moreover, the ground heat fluxes calculated with the TDEC method and the HA technique are highly correlated with each other (R² = 0.97), and their difference is only about 1 percent. The TDEC-calculated ground heat flux also has a good linear relationship with the ITHP-calculated ground heat flux (R² = 0.99), but their difference is larger (about 9 percent). Furthermore, compared to the HFP01SC direct measurements at a depth of 5 cm, the ground heat flux calculated with the HA technique, the TDEC method, and the ITHP approach can improve the surface energy budget closure by about 6 percent, 7 percent, and 6 percent at SACOL site, respectively. Therefore, the contribution of ground heat flux to the surface energy budget is very important for the semi-arid grassland over the Loess Plateau in China. Using turbulent heat fluxes with common corrections, soil heat storage between the surface and the heat flux plate can improve the surface energy budget closure by about 6 to 7 percent, resulting in a closure of 82 to 83 percent at the SACOL site.     

作物需水量研究进展的回顾与展望

国内外有关作物需水研究的进展情况和相关估算方法,包括研究内容、定量估算方法和数学预测方法,通过其分析论述了各方法的主要原理、特点及局限性,并指出了日前作物需水研究领域存在的主要问题是在非均一下垫面条件下,植被与环境以及植被间的相互作用要比均一下垫面复杂得多。目前的计算模式存在着许多假设,普适性不够,难以推广应用,今后需进一步研究的课题与采取的研究思路主要是改进蒸散计算方法。最后简要介绍了一种利用遥感蒸散模型率定通用陆面模式CoLM来估算区域陆面蒸散量以及陆地耗水量的思路。     

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。     

科尔沁沙地梯级生态带水热通量变化特征及气候学足迹

荒漠化地区水热通量变化特征和气候学足迹对理解干旱、半干旱区气候变化及水分循环具有重要意义。以科尔沁沙地一条梯级生态带为研究区,运用2017年3-12月大孔径闪烁仪和自动气象站数据对研究区不同时间尺度水热通量和通量源区的动态变化特征进行分析。结果表明：水热通量日变化特征明显,各分支能量占比不同。晴天近地表能量各项分支曲线均呈显著单峰状,多云天水热通量变化无显著规律;水热通量季节变化显著,夏季显热通量值小于春季、秋季和冬季,潜热通量夏季最大,其次为春季和秋季,冬季最小;小时尺度和日尺度上源区变化较大;季节尺度上,源区面积春季 > 秋季 > 夏季,季节尺度间源区差异较小时尺度和日尺度降低;结合梯级生态带内下垫面类型看,生长季源区以光径中段的玉米农田占比最大,沙丘和草甸下垫面次之,光径内小型湖泊所占源区比例较小。不同月份各下垫面类型占比略有不同。     

基于遥感的区域热环境分析

为研究城市及其周边区域大范围热环境变化,以秦岭山脉南坡和北坡为例,采用遥感数据反演地表温度、植被指数和地表通量,不仅从传统地表温度参数理解区域热环境问题,还着重分析了秦岭两侧地表通量空间分布格局.研究表明,秦岭山脉南坡与北坡气候、地形和地表覆被状况的差异导致地表温度和热通量等热环境均存在显著差异.北坡的西安和咸阳市平均地表温度比其他行政区显著偏高,而在南坡植被覆盖较好的周至县境内,地表温度平均值则显著下降;裸地和居民地的地表温度平均值较高,而潜热通量和蒸散发平均值则较低.遥感估算区域热通量和蒸散发信息与地表温度同样是区域热环境研究中不可忽视的重要表征变量之一,而大范围区域热环境变化对于研究城市热岛效应的形成机制具有重要推动作用.     

基于GIS空间分析技术的新月形沙丘表面输沙率模型研究

 输沙率研究是风沙物理学与风沙工程学的重要内容。为了尝试GIS空间分析技术在新月形沙丘表面不同部位输沙率分布及模型建立中的应用,选取塔克拉玛干沙漠腹地典型孤立新月形沙丘,对其表面进行粒度采样和风速采样,并对沙丘表面的五个典型部位进行输沙率的采集。经过对风速数据归一化处理之后,根据粒度和风速采样特点,分别应用克里格方法和反距离方法对粒度和风速样点插值,得到新月形沙丘表面栅格形式的粒径分布和风速分布图。利用3种常用输沙率模型分别对沙丘表面5个典型部位进行输沙率计算,并与实测值进行对比。选取拟合优度最佳的Srensen模型,整合粒径和风速分布图,利用地图代数方法对沙丘表面输沙率分布进行计算,得到栅格形式的沙丘表面输沙率分布图。利用GIS的空间分析技术研究沙丘表面的输沙率分布,克服了传统定点观测的诸多不足。     

Spatial Patterns in Surface Energy Balance Components Derived from Remotely Sensed Data

A relatively simple modeling approach for estimating spatially distributed surface energy fluxes was applied to two small watersheds, one in a semi‐arid climate region and one in a sub‐humid region. This approach utilized a combination of ground‐based meteorological data and remotely sensed data to estimate ‘instantaneous’ surface energy fluxes at the time of the satellite or aircraft overpasses. The spatial resolution in the watershed grid cells, which was on the order of 100‐400 km, was selected to be compatible with ground measurements used for validation. The model estimates of surface energy fluxes compared well with ground‐based measurements of surface flux (typically within approximately 40 Wm^?2). The model accuracy may be slightly less for bare soil surfaces due to an overestimation of the soil heat flux. In addition to demonstrating the feasibility of computing spatially distributed values of surface energy fluxes, these maps were used to qualitatively infer the dominant factors controlling the energy fluxes for the time period shortly following precipitation events in the basins. For the semi‐arid watershed, values of sensible heat flux varied considerably over the watershed and displayed a pattern very similar to that of the spatially variable cumulative precipitation for at least one to eight days prior to the image acquisition. Due to the large fraction of exposed bare soil in a semi‐arid ecosystem, even very small precipitation events had a strong influence on the pattern of sensible heat fluxes observed shortly after the event (less than 24 hours). For the sub‐humid watershed, the fluxes tended to be more uniform across the watershed, and were influenced by a combination of precipitation total and land cover type.