288.15 K-323.15 K下氯化锂、硫酸锂溶液的密度及摩尔体积研究          下载免费PDF全文

马修臻  胡斌  高丹丹  李武  董亚萍 《盐湖研究》2017,25(4):32-32

用振荡管密度计测定了常压下,温度在288.15-323.15 K范围内不同离子强度的LiCl和 Li₂SO₄溶液的密度,计算了两种锂盐在不同温度下的表观摩尔体积,溶液的浓度范围分别为(0.1~18.9) mol·kg-1及(0.03~3.0)mol·kg-1。用Pitzer离子相互作用模型拟合了LiCl和Li₂SO₄不同温度下的的Pitzer单电解质体积参数,模型的计算值与实验值相吻合良好。  相似文献   

Exploring the performance of spatio-temporal assimilation in an urban cellular automata model     

Xuecao Li  Yuyu Zhou  Tengyun Hu  Lu Liang  Xiaoping Liu 《International journal of geographical information science》2017,31(11):2195-2215

Urban cellular automata (CA) models propagate and accumulate errors during the modeling process due to the model structure or stochastic processes involved. It is feasible to assimilate real-time observations into an urban CA model to reduce model uncertainties. However, the assimilation performance is sensitive to the spatio-temporal units in the assimilation algorithm, that is, spatial block size and window length (temporal interval). In this study, we coupled an assimilation model, an ensemble Kalman filter (EnKF) and a Logistic-CA model to simulate the urban dynamic in Beijing over a period of two decades. Our results indicate that the coupled EnKF-CA model outperforms the CA-alone counterpart by about 10% in terms of the figure of merit, which reflects the agreement of modeled pixels. We also find that the assimilation performance using a finer block (1 km) is better than that using a coarser block (5 km and 10 km) because of the better depiction of spatial heterogeneity using a finer block. Moreover, the improvement of intermediate outputs using the coupled EnKF-CA model is effective for a certain period (e.g. 5 years). This implies that a high-frequency assimilation may not significantly improve the model performance. The sensitivity analyses of spatio-temporal assimilation in the EnKF-CA model provide a better understanding of the assimilation mechanism that couples with land-use change models.  相似文献   

Performance of RegCM4 over Major River Basins in China     

Xuejie GAO  Ying SHI  Zhenyu HAN  Meili WANG  Jia WU  Dongfeng ZHANG  Ying XU  Filippo GIORGI 《大气科学进展》2017,34(4):441-455

A long-term simulation for the period 1990–2010 is conducted with the latest version of the International Centre for Theoretical Physics' Regional Climate Model(RegCM4), driven by ERA-Interim boundary conditions at a grid spacing of 25 km. The Community Land Model(CLM) is used to describe land surface processes, with updates in the surface parameters,including the land cover and surface emissivity. The simulation is compared against observations to evaluate the model performance in reproducing the present day climatology and interannual variability over the 10 main river basins in China,with focus on surface air temperature and precipitation. Temperature and precipitation from the ERA-Interim reanalysis are also considered in the model assessment. Results show that the model reproduces the present day climatology over China and its main river basins, with better performances in June–July–August compared to December–January–February(DJF).In DJF, we find a warm bias at high latitudes, underestimated precipitation in the south, and overestimated precipitation in the north. The model in general captures the observed interannual variability, with greater skill for temperature. We also find an underestimation of heavy precipitation events in eastern China, and an underestimation of consecutive dry days in northern China and the Tibetan Plateau. Similar biases for both mean climatology and extremes are found in the ERA-Interim reanalysis, indicating the difficulties for climate models in simulating extreme monsoon climate events over East Asia.  相似文献   

A New Infrared Atmospheric Sounding Interferometer Channel Selection and Assessment of Its Impact on Met Office NWP Forecasts     

Young-Chan NOH  Byung-Ju SOHN  Yoonjae KIM  Sangwon JOO  William BELL  Roger SAUNDERS 《大气科学进展》2017,34(11):1265-1281

A new set of Infrared Atmospheric Sounding Interferometer(IASI) channels was re-selected from 314 EUMETSAT channels.In selecting channels,we calculated the impact of the individually added channel on the improvement in the analysis outputs from a one-dimensional variational analysis(1D-Var) for the Unified Model(UM) data assimilation system at the Met Office,using the channel score index(CSI) as a figure of merit.Then,200 channels were selected in order by counting each individual channel's CSI contribution.Compared with the operationally used 183 channels for the UM at the Met Office,the new set shares 149 channels,while the other 51 channels are new.Also examined is the selection from the entropy reduction method with the same 1D-Var approach.Results suggest that channel selection can be made in a more objective fashion using the proposed CSI method.This is because the most important channels can be selected across the whole IASI observation spectrum.In the experimental trial runs using the UM global assimilation system,the new channels had an overall neutral impact in terms of improvement in forecasts,as compared with results from the operational channels.However,upper-tropospheric moist biases shown in the control run with operational channels were significantly reduced in the experimental trial with the newly selected channels.The reduction of moist biases was mainly due to the additional water vapor channels,which are sensitive to the upper-tropospheric water vapor.  相似文献   

基于数据同化技术的延河流域绿水模拟研究     

赵海根  杨胜天  周旭 《地理科学》2017,37(7):1112-1119

分别利用分布式时变增益水文模型（DTVGM）和分布式耗水过程模型（DEPM）对延河流域延安水文站以上区域进行水文过程模拟,并应用拓展卡尔曼滤波(EKF)算法对2个模型的绿水(实际蒸散发)模拟结果进行同化处理,从而优化了研究区的绿水量并得出绿水的空间分布规律。结果表明：在整个模拟期,DTVGM的月尺度效率系数（NSCE）达到了0.83,水量平衡相对误差为-1.97%,模型能够较好地模拟研究区的水文过程;DEPM的水量平衡相对误差为-1.81%,能较好地模拟流域的水量平衡;DTVGM和DEPM模拟的流域2010年平均绿水量分别为378.52 mm和375.55 mm,空间分布格局相似。与站点观测值比较,DTVGM和DEPM模拟绿水的NSCE分别是0.76和0.59,DEPM的结果具有更多的空间变化信息。同化结果表明EKF算法能综合优化2个模型的模拟结果,同化后DTVGM模拟研究区的平均绿水量为376.34 mm,NSCE为0.78;同化后研究区绿水标准差为40.37 mm,比同化前增加了7.79 mm,绿水空间分布体现了更多的空间变化信息,同时,空间分布时格局也更加合理。  相似文献   

Data assimilation of satellite-based actual evapotranspiration in a distributed hydrological model of a controlled water system     

《International Journal of Applied Earth Observation and Geoinformation》2017

Advances in earth observation (EO) and spatially distributed hydrological modelling provide an opportunity to improve modelling of controlled water systems. In a controlled water system human interference is high, which may lead to incorrect parameterisation in the model calibration phase. This paper analyses whether assimilation of EO actual evapotranspiration (ETa) data can improve discharge simulation with a spatially distributed hydrological model of a controlled water system. The EO ETa estimates are in the form of eight-day ETa composite maps derived from Terra/MODIS images using the ITA-MyWater algorithm. This algorithm is based on the surface energy balance method and is calibrated for this research for a low-lying reclamation area with a heavily controlled water system: the Rijnland area in the Netherlands. Data assimilation (DA) with the particle filter method is applied to assimilate the ETa maps into a spatially distributed hydrological model. The hydrological model and DA framework are applied using the open source software SIMGRO and PCRaster-Python respectively. The analysis is done for a period between July and October 2013 in which a high discharge peak followed a long dry-spell. The assimilation of EO ETa resulted in local differences in modelled ETa compared to simulation without data assimilation, while the area average ETa remained almost the same. The modelled cumulative discharge graphs, with and without DA, showed distinctive differences with the simulation, with DA better matching the measured cumulative discharge. The bias of simulated cumulative discharge to the observed data reduced from 14% to 4% when using DA of EO ETa. These results showed that assimilating EO ETa may not only be effective in the more common applications of soil moisture and crop-growth modelling, but also for improving discharge modelling of controlled water systems.  相似文献   

Forecast of wheat yield throughout the agricultural season using optical and radar satellite images     

《International Journal of Applied Earth Observation and Geoinformation》2017

The aim of this study is to estimate the capabilities of forecasting the yield of wheat using an artificial neural network combined with multi-temporal satellite data acquired at high spatial resolution throughout the agricultural season in the optical and/or microwave domains. Reflectance (acquired by Formosat-2, and Spot 4–5 in the green, red, and near infrared wavelength) and multi-configuration backscattering coefficients (acquired by TerraSAR-X and Radarsat-2 in the X- and C-bands, at co- (abbreviated HH and VV) and cross-polarization states (abbreviated HV and VH)) constitute the input variable of the artificial neural networks, which are trained and validated on the successively acquired images, providing yield forecast in near real-time conditions. The study is based on data collected over 32 fields of wheat distributed over a study area located in southwestern France, near Toulouse. Among the tested sensor configurations, several satellite data appear useful for the yield forecasting throughout the agricultural season (showing coefficient of determination (R²) larger than 0.60 and a root mean square error (RMSE) lower than 9.1 quintals by hectare (q ha⁻¹)): C_VH, C_HV, or the combined used of X_HH and C_HH, C_HH and C_HV, or green reflectance and C_HH. Nevertheless, the best accurate forecast (R² = 0.76 and RMSE = 7.0 q ha⁻¹) is obtained longtime before the harvest (on day 98, during the elongation of stems) using the combination of co- and cross-polarized backscattering coefficients acquired in the C-band (C_VV and C_VH). These results highlight the high interest of using synthetic aperture radar (SAR) data instead of optical ones to early forecast the yield before the harvest of wheat.  相似文献   

基于凸集投影的高分四号卫星影像超分辨率重建   总被引：1，自引：0，他引：1  

许丽娜  何鲁晓 《测绘学报》2017,46(8):1026-1033

基于凸集投影(projection on convex sets,POCS)对GF-4数据进行超分辨率重建处理。利用能量连续降减法构造参考帧以减少迭代次数,提高算法效率;利用Vandewalle配准法对图像块进行运动估计从而获取精确的运动参数有利于图像的分块处理。通过对GF-4真实数据进行试验与分析,表明超分图像结果的清晰度与序列影像帧数呈正相关;信噪比与帧数呈负相关。应用5帧数据进行超分重建,清晰度(平均梯度)从7.803提高到14.386;信噪比会略有下降,从3.411下降到3.336。试验表明该方法可以有效提高图像清晰度,增加图像细节信息,提升图像判别能力,扩展数据的应用范围。  相似文献   

雷达资料同化在局地强对流预报中的应用   总被引：4，自引：1，他引：3  

薛谌彬  陈娴  吴俞  徐星生  高勇 《大气科学》2017,41(4):673-690

采用ARPS模式的资料分析系统ADAS同化多普勒雷达径向速度和反射率因子资料,分析两者对初始场的改进作用,并应用于WRF中尺度模式中对2012年8月21日江西省一次局地强对流过程进行了模拟试验。分析结果表明:（1）ADAS同化系统能够利用雷达径向速度和反射率因子资料有效增加初始场中的中小尺度风场信息和云、水物质含量,并通过湿绝热或非绝热初始化对温度场、湿度场和风场进行调整,使初始场在动力和热力上达到平衡。（2）同化径向速度后对改善模式初始场的动力场有重要贡献,而对大气水凝物和降水的预报影响较小;同化反射率因子的主要作用是调整初始场中的水凝物场和热力场,有效缩短了模式的“ spin-up”时间,明显改进了定量降水预报;同时同化雷达径向速度和反射率因子后,初始场中快速调整出了中小尺度风场水平辐合、垂直运动以及合理的温、湿分布,对3小时内雨带形状、降水落区及定量降水的预报与实况更接近。（3）模拟试验表明,同时同化径向速度和反射率因子能成功模拟出本次对流单体风暴的中β尺度三维空间分布结构及其演变过程,中低层切变线的辐合抬升强迫作用是对流单体风暴组织、发展和维持的主要动力机制之一,对流凝结潜热加热在对流单体风暴的发生发展中发挥了重要作用。因此,雷达资料同化对提高临近数值天气预报的准确率以及对强对流天气系统的模拟能力具有重要意义。  相似文献   

Subseasonal Reversal of East Asian Surface Temperature Variability in Winter 2014/15     

Xinping XU  Fei LI  Shengping HE  Huijun WANG 《大气科学进展》2018,35(6):737-752

Although there has been a considerable amount of research conducted on the East Asian winter-mean climate, subseasonal surface air temperature(SAT) variability reversals in the early and late winter remain poorly understood. In this study,we focused on the recent winter of 2014/15, in which warmer anomalies dominated in January and February but colder conditions prevailed in December. Moreover, Arctic sea-ice cover(ASIC) in September–October 2014 was lower than normal,and warmer sea surface temperature(SST) anomalies occurred in the Ni ?no4 region in winter, together with a positive Pacific Decadal Oscillation(PDO|+) phase. Using observational data and CMIP5 historical simulations, we investigated the PDO|+ phase modulation upon the winter warm Ni ?no4 phase(autumn ASIC reduction) influence on the subseasonal SAT variability of East Asian winter. The results show that, under a PDO|+ phase modulation, warm Ni ?no4 SST anomalies are associated with a subseasonal delay of tropical surface heating and subsequent Hadley cell and Ferrel cell intensification in January–February, linking the tropical and midlatitude regions. Consistently, the East Asian jet stream(EAJS) is significantly decelerated in January–February and hence promotes the warm anomalies over East Asia. Under the PDO|+ phase,the decrease in ASIC is related to cold SST anomalies in the western North Pacific, which increase the meridional temperature gradient and generate an accelerated and westward-shifted EAJS in December. The westward extension of the EAJS is responsible for the eastward-propagating Rossby waves triggered by declining ASIC and thereby favors the connection between ASIC and cold conditions over East Asia.  相似文献