塔克拉玛干沙漠腹地辐射平衡和反照率变化特征

辐射平衡直接影响地气系统物质和能量交换,辐射平衡研究极其重要。本研究使用了2006年8月至2011年12月位于塔克拉玛干沙漠腹地塔中的塔克拉玛干沙漠大气环境观测试验站地表辐射和反照率观测资料,分析了辐射平衡和地表反照率季节变化和年变化以及各种典型天气下日变化的特征,并与其他地区进行了对比。结果表明：沙漠腹地辐射平衡各分量最小值均出现在1月,各分量最大值出现时间不一致,其中短波辐射5月最大,长波辐射7月最大,而净辐射最大值在6月。各辐射分量夏季最大,冬季最小;总辐射四季平均日变化极值低于青藏高原,与黑河戈壁相差不大;反射辐射春季与夏季、秋季与冬季差值较小。短波辐射和净辐射各季日峰值出现在12：00,长波辐射各季日峰值出现时间比短波辐射滞后1～3 h。大气长波辐射各季日振幅较小,约为地面长波辐射的1/5～1/4,且地面长波辐射各季日变化为不对称分布;长波辐射各季日最小值都出现在日出前1 h。多云、浮尘和沙尘暴天气辐射平衡日变化不规则,云量和沙尘对辐射各分量影响明显;沙尘暴日,大气长波辐射峰值可增加18%,而总辐射、反射辐射、地面长波辐射和净辐射峰值分别衰减了57.8%、54.0%、55.8%和21.9%。地表反照率3月最大（0.30）,7月最小（0.25）,平均值为0.27;夏季小,冬季大;晴天早晨和傍晚大,沙尘暴日最大。     

冰川下垫面对夏季云结构和云水含量的影响——以祁连山区疏勒南山为例

云水含量和云结构参量是天气预报、高山区水循环过程分析的基础.基于2012—2015年夏季CloudSat卫星遥感资料的2B-CLDCLASS、2B-GEOPROF和2B-GEOPROF-LIDAR,结合中国第二次冰川编目数据及气象资料,对祁连山地区疏勒南山冰川区与非冰川区云水含量和云类型特征进行分析.结果 表明:(1)...     

甘肃一次副高内部极端强降水可预报性思考

传统认为副高内部下沉运动,抑制对流运动的发生,但是甘肃河东隔几年就会出现一次副高内部的强降水过程,而全球业务模式对此类强降水预报能力较弱,导致副高内部的强降水天气预报难度很大。利用多种常规和非常规观测资料,对2016年8月22日甘肃副高内部的一次极端强降水过程进行分析,以期发现一些可用预报指标,结果表明:青藏高压东北部辐散区和近地面层的中尺度辐合线的叠置,有利于形成强烈的上升运动,是强降水发生的天气背景条件。环境场极高的水汽含量,异常厚的暖云层,和小的垂直风切变有利于形成极大的降水效率,是强降水的增强条件。通过对各种中尺度观测资料的分析,发现一些对强降水预报预警有指示作用的因子:(1)对流云团冷云盖中心区域运动前方逐时云顶亮温(TBB)梯度最大处对应地面降水最强降水。(2)闪电总次数峰值后1~2h,且闪电带变的很有组织时,对应地面最强降水时段。(3)造成强降水的对流单体的雷达回波表现出低质心暖云降水的特征。(4)在组合反射率(CR)、垂直液态水含量(VIL)最大值出现后30~40 min,最强雨强出现。     

CLOUD BAND MORPHOMETRY: AN ALTERNATIVE APPROACH TO SATELLITE IMAGE ANALYSIS

This research assesses the use of Cold Front Cloud Band (CFCB) morphometry as an indicator of the characteristics of air masses at cold fronts. Measurements of the configuration of the CFCB (i.e., length, width, length/width ratio, and radius of curvature) are made using GOES/SMS satellite imagery. CFCB height and air mass characteristics of temperature, specific humidity, 500 mb wind velocity, and 500 mb vorticity are derived from NWS surface and upper air charts. Nonparametric correlations are utilized to relate CFCB morphometric variables to the selected characteristics of maritime tropical (mT) and continental polar (cP) air masses as they meet to form cold fronts over the eastern United States.

CFCB-Air Mass relationships resulting in higher correlations are examined through two series of interpretive tests. The stronger correlations imply a direct relationship between CFCB height and 500 mb vorticity and between CFCB length and cP specific humidity; and inverse relationships between both the CFCB length/width ratio and mT specific humidity and between CFCB radius of curvature and 500 mb vorticity. Preliminary investigation suggests that the cloud band morphometric approach to weather satellite image interpretation is a viable point of departure for future research.     

京津冀夏季强降水下冰云宏微观特征

根据Aqua MODIS 2级云产品和Cloudsat的2级产品资料,结合降水数据和MODIS L1B级辐射率数据,对发生在京津冀地区夏季的三次强降水过程中冰云的宏微观物理量的特征进行分析,并探究这些物理量和降水强度的关系。结果表明：在水平分布中,强降水过程中降水强度高值区内云相为冰云,冰云云顶高度在8~17 km,冰云粒子有效半径、冰云光学厚度、冰水路径分别最高可达60 μm、 150、 5 000 g?m^-2;冰云光学厚度、冰水路径、冰云云顶高度随降水强度增大而增大。在垂直分布中,冰云主要分布在3.5 km以上,发生强降水站点的冰云为深对流云,冰云粒子有效半径、冰水含量、冰云粒子数浓度分别最高可达150 μm、 3 000 mg?m^-3 、 500 L^-1;冰云粒子有效半径高值区存在于云层中下部,且随高度上升而减小,冰云粒子数浓度高值区存在于云层中上部,且随高度上升而增加,冰水含量高值区则存在于云层中部;冰云粒子有效半径、冰水含量、冰云粒子数浓度在9 km以上随降水强度增大而增大。     

Influences of agricultural phenology dynamic on land surface biophysical process and climate feedback

Response and feedback of land surface process to climate change is one of the research priorities in the field of geoscience. The current study paid more attention to the impacts of global change on land surface process, but the feedback of land surface process to climate change has been poorly understood. It is becoming more and more meaningful under the framework of Earth system science to understand systematically the relationships between agricultural phenology dynamic and biophysical process, as well as the feedback on climate. In this paper, we summarized the research progress in this field, including the fact of agricultural phenology change, parameterization of phenology dynamic in land surface progress model, the influence of agricultural phenology dynamic on biophysical process, as well as its feedback on climate. The results showed that the agriculture phenophase, represented by the key phenological phases such as sowing, flowering and maturity, had shifted significantly due to the impacts of climate change and agronomic management. The digital expressions of land surface dynamic process, as well as the biophysical process and atmospheric process, were improved by coupling phenology dynamic in land surface model. The agricultural phenology dynamic had influenced net radiation, latent heat, sensible heat, albedo, temperature, precipitation, circulation, playing an important role in the surface energy partitioning and climate feedback. Considering the importance of agricultural phenology dynamic in land surface biophysical process and climate feedback, the following research priorities should be stressed: (1) the interactions between climate change and land surface phenology dynamic; (2) the relations between agricultural phenology dynamic and land surface reflectivity at different spectrums; (3) the contributions of crop physiology characteristic changes to land surface biophysical process; (4) the regional differences of climate feedbacks from phenology dynamic in different climate zones. This review is helpful to accelerate understanding of the role of agricultural phenology dynamic in land surface process and climate feedback.     

农业物候动态对地表生物物理过程及气候的反馈研究进展

地表过程对全球变化的响应和反馈是地球系统科学研究的核心课题之一,目前的研究多关注全球变化对地表过程的影响,而地表动态过程对地表生物物理过程及气候的反馈研究较少。系统认识地表物候动态对生物物理过程及气候的反馈对深化地球系统科学研究有着重要的意义。本文从农业物候动态的事实、农业物候动态在陆面过程模型中的参数化表达、农业物候动态对地表生物物理过程及气候的反馈等方面进行综述,发现在气候变化和管理措施影响下,以种植期和灌浆期为代表的农业物候期发生了显著的规律性变化;耦合农业物候动态,改善了模型对地表动态过程、生物物理过程和大气过程的数字化表达;农业物候变化对地表净辐射、潜热、感热、反照率和气温、降水、环流等过程产生了影响,并表现出以地表能量分配为主的气候反馈机理。针对农业物候动态对地表生物物理过程及气候效应的时空重要性,需要继续开展以下方面的工作：① 加强全球变化对地表物候动态的影响及其反馈的综合研究;② 不同光谱波段地表反射率与农业物候动态的关系研究;③ 农业物候动态引起的作物生理学特征变化在地表生物物理过程中的贡献;④ 重视不同气候区物候动态对气候反馈效应的差异。     

基于 MODIS 和 CloudSat 的京津冀降水冰云季节分布特征

利用 2008 年 9 月~2016 年 8 月 Aqua MODIS 和 CloudSat 卫星数据,筛选出京津冀地区的降水 冰云,同时将其分为 4 个区域讨论,得到关于该地区降水冰云 4 个季节的分布特征,为该地区的人 工影响天气提供依据。结果表明：京津冀整个地区的降水冰云在夏季的发生率都较高,且发生率 有上升的趋势。从整个地区看来,京津冀地区的降水冰云的云顶高度在冬季最低、夏季最高,云顶 温度的最小值在冬季最高、夏季最低;京津冀地区的降水冰云在春夏秋 3 季均以单层云为主,而在 冬季则以双层云为主;京津冀地区的降水冰云的类型按春夏秋冬分别为 7 种、7 种、6 种和 5 种,且在 夏季该地区的降水冰云以深对流云为主（占 48.3%）,而其他季节以雨层云为主;京津冀地区降水冰 云微物理量（包括冰水含量、粒子数浓度、粒子有效半径）主要分布高度分别为 0~13.5 km（春季）、 3.5~17.0 km（夏季）、1.0~14.0 km（秋季）、0~11.0 km（冬季）。冰水含量、粒子有效半径和粒子数浓度 的分布高度和最大值均在夏季最高,但粒子有效半径在秋季最低,冰水含量和粒子数浓度在冬季 最低。这 3 种微物理量随高度的分布特征夏季在京津冀各分区较为一致,都呈单峰结构,在其他季 节差异较大。     

Intra-annual variability of satellite observed surface albedo associated with typical land cover types in China

Surface albedo is a primary causative variable associated with the process of surface energy exchange. Numerous studies have examined diurnal variation of surface albedo at a regional scale; however, few studies have analyzed the intra-annual variations of surface albedo in concurrence with different land cover types. In this study, we amalgamated surface albedo product data (MCD43) from 2001 to 2008, land-use data (in 2000 and 2008) and land cover data (in 2000); quantitative analyses of surface albedo variation pertaining to diverse land cover types and the effect of the presence/absence of ground snow were undertaken. Results indicate that intra-annual surface albedo values exhibit flat Gaussian or triangular distributions depending upon land cover types. During snow-free periods, satellite observed surface albedo associated with the non-growing season was lower than that associated with the growing season. Satellite observed surface albedo during the presence of ground snow period was 2-4 times higher than that observed during snow-free periods. Surface albedo reference values in typical land cover types have been calculated; notably, grassland, cropland and built-up land were associated with higher surface albedo reference values than barren while ground snow was present. Irrespective of land cover types, the lowest surface albedo reference values were associated with forested areas. Proposed reference values may prove extremely useful in diverse research areas, including ecological modeling, land surface process modeling and radiation energy balance applications.     

层状云微物理属性垂直分布的季节变化——以新疆地区为例

利用CloudSat卫星资料2B-CLDCLASS和2B-CWC-RVOD数据集,分别揭示了层云与层积云的云粒子等效半径、数浓度及含水量等微物理属性的垂直分布特征及其季节变化规律。结果表明：层云所在的云层高度比层积云高,特别是春季,层云可以延伸到11.0 km处,而层积云云层所在高度最高出现在夏季,最高延伸到8.5 km处。层云中的冰水分布在1.0~11.0 km,液态水分布在0~9.0 km,而层积云的冰水和液态水均分布在0~9.0 km。层云与层积云的冰粒子等效半径、水云粒子数浓度、液态水含量呈现随云层高度的增加而减小的趋势,冰粒子数浓度随云层高度增加呈增大趋势,冰水含量呈峰值分布,峰值出现在6~10 km范围内。各季节层积云粒子等效半径、粒子数浓度及水含量的最大值均大于层云的对应值,从这方面看,层积云更适合作人工增水对象。     

云南滇中地区强对流雷达回波统计分析

为了更好地开展强对流监测、预警和开展人工防雹作业指挥工作,通过对2006年至2012年昆明多普勒雷达观测的1148幅回波和234个降雹过程进行了收集和整理,从人工防雹作业指挥判别雹云的角度,对雷达回波的强度、高度和VIL等要素进行了统计分析。统计分析表明,云南滇中地区强对流发展强度强、高度高;虽然仅通过VIL跃升值难以判别强对流云体能否产生降雹,但冰雹云发展存在明显的VIL跃升,进而得出了强对流云体的VIL跃升值(前后两回波的VIL差值)是否超过35kg/m^2,可以作为强对流云体能否产生降雹的指标这一结论。     

西苕溪流域不同土地类型下氮元素输移过程

以西苕溪流域为研究对象,选择最有代表性的5种土地类型,模拟天然大暴雨,通过3次重复实验研究不同形态氮素随暴雨径流及径流沉积物的迁移过程,估算氮素在流域内不同土地利用/土地覆被条件下的损失率。研究结果表明,在相同的降雨条件下,氮素的流失速率和流失量随土地利用/土地覆被类型的不同表现出明显差异,地表径流水相总氮的流失量桑林最大,水田最小。水相不同形态的氮素流失量亦有所不同,悬浮颗粒态氮占地表径流水相总氮的70 %~90 %,水相溶解态氮的流失量以松林为最高,竹林、桑林和水田接近而且较低,不同类型的水相溶解态氮也随土地利用类型的不同表现出各自的特征。各土地类型单位面积、表层10 cm土壤氮素流失高达4.66~9.40 g·m-2,其中随径流沉积物相迁移的氮素占绝大部分(90 % 以上)。估算出的各土地利用类型总氮流失速率,地表径流水相为2.68~14.48 mg·m-2·min-1,径流沉积物相高达100.01~172.67 mg·m-2·min-1。     

An overview of the spatial patterns of land surface processes over arid and semiarid regions

With data from the project Collaborative Observation of Semi-arid/Arid Regions in North China, collected during July and September 2008, the spatial patterns of land surface processes over arid and semiarid regions have been investigated based on the ordinary Kriging interpolation approach. Generally, for the radiation processes, downward and upward short-wave radiation have a uniformly increasing trend with latitude, but the spatial patterns of long-wave radiation present notable regional differences: both upward and downward long-wave radiation increase with latitude in the west of North China, while in the east they vary inversely with latitude, suggesting surface temperature and clouds respectively have feedbacks to the long-wave radiation in the west and east of North China. The surface net radiation basically has a negative latitudinal trend. Long-wave radiation budget plays an important role in the spatial pattern of surface net radiation, particularly in the east of North China, although short-wave radiation budget largely determines the magnitude of surface net radiation. For the energy processes, latent and sensible heat flux varies conversely with latitude: more available land surface energy is consumed by evaporating soil water at lower latitudes while more is used for heating the atmosphere at higher latitudes. A soil heat flux maximum and minimum are found in Loess Plateau and Qinghai Plateau respectively, and a maximum is seen in the northeast China.     

20世纪末中国中东部耕地扩张对表面气温影响的模拟

利用WRF模式,通过4个21年（1980-2000年）的模拟实验,研究了20世纪末中国中东部耕地扩张对表面气温的影响。控制实验分析发现WRF模式能够捕捉温度场的空间格局,模拟与观测的季节平均温度场的相关系数为0.91~0.99（P < 0.001）,但模拟温度比观测温度系统性偏低2~3 ℃。控制实验与敏感实验对比分析发现,东北区和中部区的毁林和毁草开荒具有降温效应,冬季平均降幅约为-0.41 ℃,居四季之首,主要是由地表反照率增加,净短波辐射减少,感热通量随之减少所致;东南区的毁林开荒具有升温效应,夏季温度升幅最大,平均升幅为0.14 ℃,主要原因是地表粗糙度减小,湍流减弱,热量在近地层集聚,难以扩散。农业扩张的升、降温效应主要出现在局地,对区域温度变化的影响甚微,一方面是因为农业扩张占区域面积份数甚小,另一方面是因为升、降温效应在区域平均过程中相互抵消。     

近50 a西安太阳辐射变化特征及相关影响因子分析

 根据常规气象观测资料以及MODIS卫星气溶胶产品,分析了西安近50 a总辐射变化特征及其相关影响因子。结果表明：西安地区1961-2005年总辐射变化经历了“持续”、“变暗”、“变亮”、“再变暗”4个阶段,西安总辐射的变化幅度较全国平均变化幅度大,其“变亮”过程开始于1985年,较全国平均时间略早;西安4个季节总辐射总体均呈现出下降趋势,其变化幅度存在一定差异。通过对云量、气溶胶、水汽压、相对湿度等影响因子的分析,水汽压和相对湿度对总辐射变化影响不明显,总云量和气溶胶的变化对西安总辐射的变化存在较显著的影响,春、夏季总辐射的变化主要受云量和气溶胶直接辐射强迫的共同影响,其中总云量的变化在一定程度上决定了总辐射变化的振幅,城市发展所导致的气溶胶增加所产生的直接辐射强迫作用可能决定了总辐射的总体下降趋势;秋、冬季节的总辐射下降趋势主要与气溶胶的直接辐射强迫有关。     

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。     

土地覆被变化过程中叶面积指数与降水量对地表能量平衡的贡献——基于SiB2的模拟结果

土地覆被变化过程中,叶面积指数（LAI）是地表能量平衡重要的影响因素,且与降水等多种因素存在交互作用。以2003 年中国东北地区农田、森林和草地三种覆被类型和三种LAI月变化过程为研究对象,着重分离出土地覆被变化过程中LAI对地表能量平衡的作用,认清覆被和LAI 变化对地表能量平衡的相对作用。利用SiB2 模型研究不同降水条件下土地覆被和LAI 变化对地表能量平衡的影响。结果表明：① 覆被变化对净辐射的影响最大,年均14.5W·m^-2左右。② LAI 主要改变净辐射对潜热和显热的分配,对农田和草地而言,LAI 增加明显提高（减小）潜热（显热）分配比例;对森林而言,LAI对潜热和显热分配的影响较弱。③ 降水对净辐射的分配起重要作用,降水增加,潜热增加。④ 表层土壤水分受降水和LAI 调控,与潜热有相反的变化趋势。     

Radiative forcing over China due to albedo change caused by land cover change during 1990–2010

Land cover change affects surface radiation budget and energy balance by chang- ing surface albedo and further impacts the regional and global climate. In this article, high spatial and temporal resolution satellite products were used to analyze the driving mechanism for surface albedo change caused by land cover change during 1990-2010. In addition, the annual-scale radiative forcing caused by surface albedo changes in China＇s 50 ecological regions were calculated to reveal the biophysical mechanisms of land cover change affecting climate change at regional scale. Our results showed that the national land cover changes were mainly caused by land reclamation, grassland desertification and urbanization in past 20 years, which were almost induced by anthropogenic activities. Grassland and forest area decreased by 0.60% and 0.11%, respectively. The area of urban and farmland increased by 0.60% and 0.19%, respectively. The mean radiative forcing caused by land cover changes during 1990-2010 was 0.062 W/m2 in China, indicating a warming climate effect. However, spatial heterogeneity of radiative forcing was huge among different ecological regions. Farmland conversing to urban construction land, the main type of land cover change for the urban and suburban agricultural ecological region in Beijing-Tianjin-Tangshan region, caused an albedo reduction by 0.00456 and a maximum positive radiative forcing of 0.863 WIm2, which was presented as warming climate effects. Grassland and forest conversing to farmland, the main type of land cover change for the temperate humid agricultural and wetland ecological region in Sanjiang Plain, caused an albedo increase by 0.00152 and a maximum negative radiative forcing of 0.184 W/m2, implying cooling climate effects.     

近10 年我国地表比辐射率的时空变化

基于Terra-MODIS L3 级产品MOD11C3,得到2001-2010 年10 年我国地表比辐射率时空数据集。结果表明,我国地表比辐射率最小的区域是西北沙漠地带,该区域比辐射率一年四季变化不大、分布范围固定。东北地区和北疆地区、青藏高原地区、长江中下游和华东华南地区等区域比辐射率变化明显。冬季,东北地区、北疆地区地表比辐射率比较大。青藏高原地区11 月-次年3 月维持在一个中低比辐射率水平,其他月份比辐射率则呈现增大趋势。长江中下游、华东、华南和四川盆地地区的比辐射率7-10 月减小,其中8 月份面积达到最大。低比辐射率区(0.6163~0.9638)、中低比辐射率区(0.9639~0.9709)、中比辐射率区(0.9710~0.9724)所占面积都不大,分别维持在20%、10%、20%左右;中高比辐射率区(0.9725~0.9738) 所占范围最大,达到我国陆地面积的40%~50%,且变化十分明显,表现出明显的波峰、波谷变化,春季和秋季是波峰、夏季和冬季是波谷;高比辐射率区(0.9739~0.9999) 面积变化也很明显,冬季是一个明显的波峰,面积可达10%,而其他季节则维持在1%、2%以下。我国地表比辐射率时空分布与温度之间呈现一定的相关关系,比辐射率越高、气温越低。     

基于卫星资料的气溶胶对冰云影响及分布特征分析

通过利用2010年1月—2016年12月CALIOP(the Cloud-aerosol lidar with orthogonal polariz-ation)冰云和气溶胶3级月平均产品和MODIS(Moderate-resolution imaging spectroradiometer)大气3级日平均产品研究气溶...