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1.
雪冰反照率能够改变冰川表面能量收支平衡,是影响冰川消融的重要因素之一。利用祁连山地区冰川面积矢量数据、MODIS逐日积雪反照率、气温和降水以及冰川物质平衡等数据,探讨了祁连山典型冰川区雪冰反照率特征及其对冰川物质平衡的影响。结果表明：祁连山地区冰川多年平均反照率为0.532,冰川区面积大小与其多年平均反照率之间呈显著正相关（R2=0.16,P<0.05,N=91）,即冰川面积缩减1 km2,对应的平均反照率下降0.0025。祁连山老虎沟12号冰川反照率在夏季有明显的海拔效应,且强于其他时段,达到0.047?（100m）-1。典型冰川年均物质平衡量与冰川表面夏季（6—8月）平均反照率之间存在显著的正相关关系,老虎沟12号冰川和七一冰川决定系数R2分别达到了0.48（P<0.05）和0.66（P <0.05）。冰川表面夏季平均反照率这一指标能够较好地衡量青藏高原北部祁连山地区冰川物质平衡的变化。 相似文献
2.
冰川表面能量平衡模型建立了冰川与大气之间的联系。为探讨不同天气条件对冰川能量收支的影响, 利用祁连山老虎沟12号冰川海拔4 550 m处的气象资料（2011年8月24日 - 9月6日）, 结合能量平衡模型, 分析了不同天气条件下的能量收支变化特征。结果表明： 受云量影响, 晴天条件下向下短波辐射（318.3 W·m-2）是多云条件下的1.5倍, 是阴天条件下的3倍。三种天气条件下的向下长波辐射, 晴天（215.4 W·m-2）<多云（267.4 W·m-2）<阴天（291.6 W·m-2）。受固态降水的影响, 阴天条件下冰川反照率（0.50）是晴天时的2倍多。而三种天气下的最大消融耗热, 晴天（739.6 W·m-2）>多云（582.8 W·m-2）>阴天（324.5 W·m-2）。在能量收入项中, 净短波辐射是主要来源（98%）, 但是受天气条件影响, 能量支出各项所占比例有明显差异; 在三种天气条件下, 净长波辐射所占比例分别为35%、 31%和23%, 消融耗热所占比例分别为62%、 64%和75%, 潜热通量所占比例相差不大。 相似文献
3.
唐古拉山冬克玛底冰川反照率变化特征研究 总被引：11，自引：10，他引：1
根据夏季消融期成像的Landsat TM影像和2000-2009年间的MOD10A1数据资料, 分析了唐古拉山区冬克玛底冰川反照率的时空变化特征. 结果表明: 受空间尺度效应和现有反演方法的影响, 由遥感反演的反照率资料在数值上存在一定的误差, 但基本上能够反映冰川反照率的时空变化特征. 从空间分布上来看, 该冰川反照率随海拔升高呈增大趋势, 其中在平衡线附近的变化最为显著; 受地形因素的影响, 在同一海拔带内部也存在着较大的差异. 从年内变化上来看, 该冰川反照率日际变化波动较大, 且具有明显的季节变化特征. 从年际变化上来看, 自2000年以来该冰川年均反照率的变化波动较大, 总体呈微弱下降的趋势, 这主要与年降雪和冰面污化程度有关; 不考虑降雪对冰面反照率的影响, 2000-2009年间该冰川在消融期的反照率呈逐年减小的趋势, 变化速率约为-0.0083·a-1, 其原因在于夏季气温的升高和冰面污化程度的加大. 相似文献
4.
夏季消融期祁连山“七一”冰川反照率初步研究 总被引：4，自引：3，他引：1
根据2006年夏季"七一"冰川自动气象站和光谱仪的反照率资料, 分析了夏季"七一"冰川反照率的时、空变化特征. 结果表明: 夏季"七一"冰川反照率的日际变化受气温影响明显, 冰川上、下部位反照率差值动态变化并具有一定的日变化特征. 冰川表层积雪随着变质作用的增强, 其光谱反射率不断下降, 其中紫外和红橙光波段反照率降幅较大(尤其是紫外波段), 在紫蓝波段降幅相对较小. 晴天时, 雪面上紫外及可见光波段反照率日变化幅度要比在冰面上的变幅大, 日变化曲线在雪面时也不对称. 冰面上各波段反照率日变化较平缓, 曲线则都比较对称. 无论在雪面还是冰面, 近红外波段反照率日变化曲线均比较对称. 冰川上全波段反照率的日变化曲线形式趋同于可见光波段反照率的日变化曲线. 同时, 文中还初步分析了反照率和积雪密度, 积雪污化浓度之间的关系, 以及反照率变化对径流的影响. 相似文献
5.
在2017 - 2018年冬季使用无人机对乌梁素海湖冰的冰面裂缝进行了航拍, 采用改进的自适应阈值分割方法进行图像二值化处理, 提取了冰裂缝的密度和分形维数。分析结果显示： 在固定区域的冰裂缝分形维数在1.35 ~ 1.50间变化, 冰裂缝数量随时间增加, 其分形维数也随之线性增大; 在冰生长期间, 冰厚度与冰裂缝分形维数也呈现出明显的线性关系（相关系数R2=0.75）。冰面不同区域的冰裂缝密度和分形维数在0.017 ~ 0.079、 1.38 ~ 1.64间变化, 且两者之间存在显著的对数相关性（相关系数R2>0.96）, 不同日期航拍数据拟合结果近似相等, 说明冰裂缝密度越大, 对应的分形维数越大。作为表征冰面形态特征的一种物理指标, 建立得到的冰裂缝分形维数与冰厚、 裂缝密度的相关关系, 对未来利用冰面裂缝形态监测冰层的生消过程可提供科学的参考。 相似文献
6.
青藏高原唐古拉山多年冻土区夏、秋季节总辐射和地表反照率特征分析 总被引：2，自引：2，他引：0
根据青藏高原唐古拉山多年冻土区2005年6月24日~10月16日的总辐射、分光辐射和分光反照率观测资料,利用总辐射和大气层顶太阳辐射的比值——日有效透射率Teff,用聚类分析法将资料划分为晴天、多云和阴天三类天气,分析了该地区夏、秋季节总辐射、分光辐射比例和分光反照率的日变化和季节变化规律.结果表明,夏季总辐射与大气层顶的差值和日际变化幅度最大,秋季以后这种差值和日际变化幅度减小.天空状况对分光辐射比例和地表反照率均有影响,表现为近红外辐射比例晴天比阴天大,可见光比例晴天比阴天小,各波段反照率晴天均比阴天大.反照率在夏季最低,秋季较高,反照率的日变化有依存分光辐射比例的关系,这大致可以解释地表反照率依存太阳高度角而变化的现象.无积雪地面反照率近红外波段大于可见光波段,地表有积雪时,反照率明显不同,其可见光波段反照率大于近红外波段反照率.功率谱分析表明,日有效透射率Teff存在着2~3 d的周期,它是该地区天气系统活动影响太阳辐射收入的一个反映,指示出唐古拉山地区天气系统亦有2~3 d的周期性. 相似文献
7.
天山乌鲁木齐河源1号冰川消融期反照率特征 总被引：2，自引：2，他引：0
消融期冰川反照率特征研究对于深入理解冰川消融过程及其对气候变化的响应机理具有重要意义。利用Landsat卫星影像反演反照率数据,MODIS逐日反照率产品数据以及野外观测反照率数据,分析了天山乌鲁木齐河源1号冰川2016年消融期（5—8月）反照率时空变化特征。研究表明：消融早期,冰川反照率空间变化不明显;消融中后期,总体上呈现随海拔的升高而增大的趋势,在平衡线附近增速最快。消融期冰川反照率整体呈下降趋势,而且在6—7月份变化最为剧烈。平衡线附近反照率时间变化尤其显著,积累区次之,消融区最弱。冰川反照率的时空变化主要由冰面特征决定。气温和固态降水是其驱动因素。冰川反照率随气温的升高而降低,但固态降水会打破其随气温的变化趋势,引起反照率的增加。污化物显著降低冰面反照率,尤其在可见光波段（380~760 nm）。此外,即使冰面特征相对均一,反照率还呈现随太阳入射角的增大而增大的趋势,主要由冰川局部地形（坡度与坡向）差异所致。 相似文献
8.
9.
天山南坡科其卡尔巴契冰川度日因子变化特征研究 总被引：14，自引：7，他引：7
度日模型是估算冰川消融的一种简单而有效的方法.根据科其卡尔巴契冰川2003年的观测资料,分析了该冰川度日因子的空间变化规律及其影响因素.研究表明:各高度上的度日因子,介于2.0～9.7mm·℃-1·d-1之间变化,平均值为5.7mm·℃-1·d-1,与青藏高原各冰川及其它地区冰川相比较小;随着海拔的增高,度日因子随之递增;随平均气温的升高而随之递减.由于冰面状况复杂,度日因子变化幅度较大,裸冰区的度日因子明显大于表碛覆盖区.人为测量误差、反照率、地形等对度日因子的影响也不容忽视. 相似文献
10.
利用2010年6-7月鄂陵湖野外试验的近地层观测数据,分析了在不同天气条件下黄河源鄂陵湖地区辐射分量、地表能量分量、土壤温度和反照率的变化特征. 结果表明：不同天气条件下,辐射和地表能量各分量日变化差异较大,晴天、阴天和雨天的地表反照率依次递减,平均反照率约为0.21;观测期内,平均辐射贡献从大到小依次为向上长波、向下长波、向下短波、向上短波,日积分值分别为31.4 MJ·m-2、25.6 MJ·m-2、22.4 MJ·m-2、4.2 MJ·m-2,净辐射(12.5 MJ·m-2)占向下短波辐射的55.7%;平均地表能量和土壤温度的变化幅度较晴天小,感热、潜热、0 cm土壤热通量的平均日积分值分别占净辐射的21.2%、43.1%、8.2%;平均土壤温度变化幅度随深度增加逐渐减小,浅层土壤温度峰值较晴天低2 ℃,深层土壤温度相差不大. 云和降水的扰动削弱了向下短波辐射,导致平均感热通量和0 cm土壤热通量的峰值比晴天小,而平均潜热通量的峰值大于晴天. 由于湖泊水体巨大的热容量和水分供应,鄂陵湖地区的气温日较差较小,地表温度变化幅度变小,附近地表温度升高缓慢. 鄂陵湖区的地表能量平衡中,潜热通量占主导,感热和地表土壤热通量次之. 研究结果有助于理解气候变化背景下黄河源区湖泊的能量水分循环过程,为促进该地区光热资源的合理利用和畜牧业的可持续发展提供数据支持. 相似文献
11.
G. S. Meena 《Journal of Earth System Science》2010,119(3):249-257
The zenith sky scattered light spectra were carried out using zenith sky UV-visible spectrometer in clear and cloudy sky conditions
during May-November 2000 over the tropical station Pune (18°32′N, 73°51′E). These scattered spectra are obtained in the spectral
range 462–498 nm between 75° and 92° solar zenith angles (SZAs). The slant column densities (SCDs) as well as total column
densities (TCDs) of NO2, O3, H2O and O4 are derived with different SZAs in clear and cloudy sky conditions. The large enhancements and reductions in TCDs of the
above gases are observed in thick cumulonimbus (Cb) clouds and thin high cirrus (Ci) clouds, respectively, compared to clear
sky conditions. The enhancements in TCDs of O3 appear to be due to photon diffusion, multiple Mie-scattering and multiple reflections between layered clouds or isolated
patches of optically thick clouds. The reductions in TCDs due to optically thin clouds are noticed during the above period.
The variations in TCDs of O3 measured under cloudy sky are discussed with total cloud cover (octas) of different types of clouds such as low clouds (C
L
), medium clouds (C
M
) and high clouds (C
H
) during May-November 2000. The variations in TCDs of O3 measured in cloudy sky conditions are found to be well matched with cloud sensitive parameter colour index (CI) and found
to be in good correlation. The TCDcloudy are derived using airmass factors (AMFs) computed without considering cloud cover and CI in radiative transfer (RT) model,
whereas TCDmodel are derived using AMFs computed with considering cloud cover, cloud height and CI in RT model. The TCDmodel is the column density of illuminated cloudy effect. A good agreement is observed between TCDmodel, TCDDob and TCDGOME. 相似文献
12.
陇中黄土高原夏季陆面辐射和热量特征研究 总被引：4，自引：1，他引：3
利用兰州大学半干旱气候与环境观测站(SACOL)的观测资料,分析了陇中黄土高原夏季陆面辐射和热量收支的特征.通过研究不同典型天气条件对陆面过程微气象特征的影响,发现地表反射率在晴天会出现早晨偏大的不对称结构;晴天与多云天气相比不平衡量较大,而阴天时的阵性降水会使局地能量收支出现不平衡.利用最小二乘法(OLS)线性回归得到的夏季平均不闭合度是19.6%.在半干旱区云和降水对辐射和能量收支的影响不容忽视,达到约25%的削弱程度,比极端干旱的敦煌荒漠区要大,又进一步证明了半干旱区夏季的平均气候特征与云量较多的多云天气(5≤Mean total cloud amount<8)接近.另外,7月日平均波恩比最大是4.1,平均是1.95,比极端干旱区的敦煌波恩比小1个数量级,说明榆中所处的黄土高原半干旱区比敦煌所处的极端干旱区在气候上要湿润很多. 相似文献
13.
Evaporation and energy balance estimates over a large inland lake in the Tibet-Himalaya 总被引：2，自引：1，他引：1
The process of evaporation from the lake surface is one of the main mechanisms in the energy and water budgets of the lake
hydrologic cycle, and an essential component of the water balance especially for inland lakes. In this study, using routine
meteorological data as input, a one-layer potential evaporation model was employed to simulate evaporation and energy fluxes
over Lake Yamdrok Yumco, the largest high-elevation inland lake in the mountain area of the Tibet-Himalaya in China. Then,
the calculation results were compared with the measured values from a big pan evaporator of 20 m2 near the lake. The results show that the average annual input radiation flux R
↓ is 128.2 W m−2, the lake storage heat flux G is 19.4 W m−2, the sensible heat flux H is 20.4 W m−2 and the latent heat flux lE is 107.8 W m−2. The R
↓ and G exhibit similar seasonal variations. The lE reaches a maximum in October, lagging nearly 4 months behind the R
↓ and the G, which indicates the large heat capacity of the lake. The simulated annual evaporation ranges from 1,113.2 to 1,429.1 mm
and its mean value is 1,252.5 mm during 1961–2005. The simulated annual evaporation is in good agreement with the measured
value, and the measured average lake temperature is as expected when compared with the measured lake surface temperature. 相似文献
14.
A method for determining the thickness of the stellar disk of a galaxy from a photometric image of the galaxy in the plane of the sky is proposed and justified. The method can be applied to determine the thickness of plane-parallel exponential disks with an arbitrary, radius-independent, luminosity distribution perpendicular to the plane of the disk J(r, z) = exp(-r/h)f(z). A special feature and advantage of the method is that it enables determination of the thicknesses of disks viewed at arbitrary angles to the plane of the sky (but not strictly edge-on or face-on). The key idea of the method is finding the true inclinations of galaxies viewed at arbitrary angles not from their isophotes, but instead from the azimuthal distribution of the exponential parameter h. The difference between the inclination determined in the traditional way using the isophotes and the true inclination enables estimation of the thickness of the disk. The effectiveness of the method for determining the inclinations of plane-parallel disks is confirmed using a sample of model isothermal galactic disks: I(r, z) = I0 exp(-r/h)sech2(z/z0). The inclinations of the planes of the model galaxies to the line of sight and the relative thicknesses in the model sample vary arbitrarily, making it possible to determine the limits of applicability of the method: z0/h < 0.7 and 10° <i < 75°.A sample of 44 piecewise-exponential disks of galaxies of the southern sky clusters is used to illustrate the application of the technique to observational data. Comparing the distribution of inclinations calculated using the new method and the traditional isophote method shows that the new method yields a more uniform distribution of inclinations to the plane of the sky for the sample galaxies. The derived average disk thicknesses and the disk-thickness distributions are consistent with statistical estimates and observational data from the literature for samples of galaxies viewed edge-on
相似文献15.
Chenour Mohammadi Manuchehr Farajzadeh Yousef Ghavidel Rahimi Abbasali Aliakbar Bidokhti 《Arabian Journal of Geosciences》2018,11(13):360
Station recording air temperature (Ta) has limited spatial coverage, especially in unpopulated areas. Since temperature can change greatly both spatially and temporally, stations data are often inadequate for meteorology and subsequently climatology studies. Time series of moderate-resolution imaging spectroradiometer (MODIS) land surface temperature (Ts) and normalized difference vegetation index (NDVI) products, combined with digital elevation model (DEM), albedo from Era-Interim and meteorological data from 2006 to 2015, were used to estimate daily mean air temperature over Iran. Geographically weighted regression was applied to compare univariate and multivariate model accuracy. In the first model, which only interfered with land surface temperature (LST), the results indicate a weak performance with coefficient of determination up to 91% and RMSE of 1.08 to 2.9 °C. The mean accuracy of a four-variable model (which used LST, elevation, slope, NDVI) slightly increased (6.6% of the univariate model accuracy) when compared to univariate model. RMSE dropped by 19% of the first model. By addition albedo in the third model, the coefficient of determination increased significantly. This increase was 32% of the univariate model and 23.75% of the 4-variable model accuracy. The statistical comparison between the three models revealed that there is significant improvement in air estimation by applying the geographically weighted regression (GWR) method with interfering LST, NDVI, elevation, slope, and albedo with mean absolute RMSE of 0.62 °C and mean absolute R2 of 0.99. In order to better illustrate the third model, t values were spatially mapped at 0.05 level. 相似文献
16.
Modifications in vegetation cover and surface albedo during rapid urbanization: a case study from South China 总被引：1，自引：0，他引：1
The green vegetation fraction (GVF) and surface albedo are important land surface parameters often used for validation of climate and land surface models that are influenced largely by environmental gradients and human activities. In this study, fine resolution GVF and albedo values derived from Landsat Thematic Mapper/Enhanced Thematic Mapper Plus images from 1990 to 2000 were used to examine the relationship of both GVF and albedo values to the spatial gradients of parameters related to dramatic urbanization in the Greater Guangzhou metropolitan area, Guangdong Province, in South China. Moderate resolution GVF and albedo datasets derived from the MODIS Collection 5 product were used to analyze the seasonal variation of GVF and albedo with rapid urban expansion from 2001 to 2007. The results show that the shortwave albedo had a clear declining trend from the urban center to natural land in 1990. However, no obvious trend in shortwave albedo change was observed along urban–rural gradients caused by the expansion of low-albedo urban buildings and more heterogeneous land cover patterns in 2000. A threshold of GVF (~0.21) was estimated for determining the change of albedo associated with vegetation fraction. Vegetation cover modified by urban expansion changed surface reflectance and influenced the surface energy balance. It is suggested that a large portion of energy absorbed in an urban area is likely to be converted to thermal energy that heating up is near the surface and emitted as longwave radiation. 相似文献
17.
K. Gopala Reddy G. Bharathi A. Ravi Kumar M. V. Subrahmanyam K. Muni Krishna 《Journal of Earth System Science》2003,112(2):267-281
Time series measurements of radiative fluxes were made onboard INS Sagardhwani (SD) in the south Bay of Bengal near DS3 (13‡N
and 87‡E) during the BOBMEX field experiment. An inter-comparison experiment conducted at DS3 showed that the radiative fluxes
measured by Kipp and Zonen, Albedo meter and net Pyrgeometer onboard SD and by Eppley radiometers onboard ORV Sagar Kanya
(SK) are well matched. It may be mentioned that the measurements showed consistency and good agreement between SD and SK ships,
even though no Gimbal mounting was used for radiation instruments onboard SD.
The main aim of the experiment was collection of high quality radiation data during the monsoon period, which can give an
insight into the nature of the ocean-atmosphere coupling. The data on the four radiative fluxes collected on SD are averaged
at 5 minute intervals and then hourly and daily averages have been computed. The hourly shortwave albedo and the atmospheric
transmission factor are also computed and the variation of albedo in relation to the solar altitude and the transmissivity
factor (TF) are studied. The mean albedo over the south Bay of Bengal under clear, partly cloudy and overcast skies are found
to be 0.05, 0.07 and 0.2 respectively. 相似文献
18.
Runoff and sediment yield modeling using SWAT model: case of Wadi Hatab basin,central Tunisia 总被引：1，自引：0，他引：1
This study presents an application of the model Soil and Water Assessment Tool (SWAT) to simulate daily and monthly water flow and sediment fluxes in the Wadi Hatab watershed (2200 km2) located in central Tunisia. The study basin is characterized by a significant climatic contrast, abrupt topography, and soil fragility, resulting thereby in flash floods and important water erosion rates. This alarming situation requires urgent interventions in order to preserve water and soil resources, implying the need for a decision tool for proper integrated management of the watershed. The model was calibrated and validated based on a comparison of simulated and observed flow rates at the basin outlet (hydrometric station Khanguet Zazia), during the periods 1987–1988 and 1989–1990, respectively. The comparison was based not only on visual inspection of the agreement between observed and simulated time series, but also on statistical parameters. Indeed, for the daily time step application, the Nash—Sutcliffe efficiency (NSE) values were 0.52 and 0.61, and the coefficient of determination (R2) was 0.54 and 0.61 for calibration and validation, respectively. As for the monthly time-step application, the obtained NSE values were 0.67 and 0.89 while R2 values were 0.83 and 0.87 for calibration and validation, respectively. This clearly shows the reasonably good agreement between simulated and observed flow rates. In terms of erosion, the model gave sediment yield values ??of 1.15 and 5.37 t/ha/year during the periods of calibration and validation, respectively. 相似文献
19.
The present study focused on detecting variations in trophic relationships among blue crab (Callinectes sapidus) consumers according to water quality along two estuaries in North Carolina. Stable isotope (δ15N and δ13C) analyses of particulate organic matter and bivalve(Rangia cuneata andCorbicula fluminea) food sources were examined in combination with an Isosource mixing model. Results suggest that blue crab δ13C values increased significantly with increasing salinity from upper to lower sites along the Neuse River estuary (NRE; R2
= 0.87, p < 0.01) and Alligator River estuary (R2 = 0.92, p < 0.01). There was a positive relationship between blue crab δ15N values and nitrate concentrations for the NRE (R2 = 0.48, p = 0.12). This study found that blue crab δ13C values increased with salinity from upper to lower regions along both estuaries. Results suggest that blue crab production
may have used alternative food sources that were isotopically (δ13C) depleted, especially in the upper NRE, and enriched sources in the mid to lower regions of both estuaries. Consumers sampled
from the upper NRE may be influenced by higher nitrogen input from urban land use and municipal wastewater. 相似文献