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气候暖干化对西北四省(区)农业种植结构的影响及调整方案 总被引：1，自引：0，他引：1
利用陕、甘、宁、青四省(区)141个气象站1961-2008年的气象要素值计算和分析得出,暖干化是西北四省(区)现代气候变化的基本特征。年平均气温表现为一致的增温趋势,每10年增温0.27℃,1996年是突变年。年降水量自1961年以来呈持续下降趋势,1986年是转折年,1987-2008年年平均降水量比1961-1986年平均减少20～40mm。以黄河为界,黄河以东降水量呈减少趋势,每10年减少10～40mm;黄河以西呈增多趋势,每10年增加10mm左右,减少的幅度明显高于增加的幅度。进入21世纪,气候暖干化的势头有所减缓。在分析不同区域自然资源特点和气候暖干化及其对农作物影响特征的基础上,运用系统规划理论,采用气候生态相似原理,提出了陕、甘、宁、青四省(区)13个不同地域农业种植结构调整方案。为了加快农业结构调整进程,使农业结构调整方案收到明显的生态、社会和经济效益,提出了四个方面的保障措施。 相似文献
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Minzhong?WangEmail author Hu?Ming Zheng?Ruan Lianhui?Gao Di?Yang 《Theoretical and Applied Climatology》2018,131(3-4):927-935
With the aim to achieve quantitative monitoring of sand-dust storms in real time, wind-profiling radar is applied to monitor and study the process of four sand-dust storms in the Tazhong area of the Taklimakan Desert. Through evaluation and analysis of the spatial-temporal distribution of reflectivity factor, it is found that reflectivity factor ranges from 2 to 18 dBz under sand-dust storm weather. Using echo power spectrum of radar vertical beams, sand-dust particle spectrum and sand-dust mass concentration at the altitude of 600 ～ 1500 m are retrieved. This study shows that sand-dust mass concentration reaches 700?μg/m3 under blowing sand weather, 2000?μg/m3 under sand-dust storm weather, and 400?μg/m3 under floating dust weather. The following equations are established to represent the relationship between the reflectivity factor and sand-dust mass concentration: Z?=?20713.5?M 0.995 under floating dust weather, Z?=?22988.3?M 1.006 under blowing sand weather, and Z?=?24584.2?M 1.013 under sand-dust storm weather. The retrieval results from this paper are almost consistent with previous monitoring results achieved by former researchers; thus, it is implied that wind-profiling radar can be used as a new reference device to quantitatively monitor sand-dust storms. 相似文献
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Analysis of the Microphysical Properties of a Stratiform Rain Event Using an L-Band Profiler Radar 总被引：2，自引：0，他引：2 
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下载免费PDF全文 This paper investigates spatial and temporal distributions of the microphysical properties of precipitating stratiform clouds based on Doppler spectra of rain particles observed by an L-band profiler radar.The retrieval of raindrop size distributions（RSDs） is accomplished through eliminating vertical air motion and isolating the terminal fall velocity of raindrops in the observed Doppler velocity spectrum.The microphysical properties of raindrops in a broad stratiform region with weak convective cells are studied using data collected from a 1320-MHz wind profiler radar in Huayin,Shaanxi Province on 14 May 2009.RSDs and gamma function parameters are retrieved at altitudes between 700 and 3000 m above the surface,below a melting layer.It is found that the altitude of the maximum number of raindrops was closely related to the surface rain rate.The maximum number of large drops was observed at lower altitudes earlier in the precipitation event but at higher altitudes in later periods,suggesting decreases in the numbers of large and medium size raindrops.These decreases may have been caused by the breakup of larger drops and evaporation of smaller drops as they fell.The number of medium size drops decreased with increasing altitude.The relationship between reflectivity and liquid water content during this precipitation event was Z = 1.69×10~4M~（1.5）,and the relationship between reflectivity and rain intensity was Z = 256I~（1.4）. 相似文献
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The distribution and variability of surface soil moisture at regional scales is still poorly understood in the Loess Plateau of China. Spatial and temporal dynamics of surface soil moisture is important due to its impact on vegetation growth and its potential feedback to atmospheric and hydrologic processes. In this study, we analyzed surface soil moisture dynamics and the impacts of precipitation and evapotranspiration on surface soil moisture using remote sensing data during the growing season in 2011 for the Loess Plateau, which contain surface soil moisture, precipitation, vegetation index and evapotranspiration. Results indicate that the areas with low surface soil moisture are mainly located in the semi-arid region. Under dry surface soil moisture, evapotranspiration temporal persistence has a higher positive correlation (0.537) with surface soil moisture temporal persistence, and evapotranspiration is very sensitive to surface soil moisture. But under wet surface soil moisture regime, surface soil moisture temporal persistence has a higher negative correlation (?0.621) with evapotranspiration temporal persistence. Correlation of surface soil moisture and monthly precipitation, evapotranspiration and vegetation index illustrated that precipitation was a significant factor influencing surface soil moisture spatial variance. The correlation coefficients between monthly surface soil moisture and precipitation was varied in different climatic regions, which was 0.304 in arid, 0.364 in semi-arid, 0.490 in transitional and 0.300 in semi-humid regions. Surface soil moisture is more sensitive to precipitation, evapotranspiration, in transitional regions between dry and wet climates. 相似文献
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Numerous land surface models exist for predicting water and energy fluxes in the terrestrial environment. These land surface models have different conceptualizations (i.e., process or physics based), together with structural differences in representing spatial variability, alternate empirical methods, mathematical formulations and computational approach. These inherent differences in modeling approach, and associated variations in outputs make it difficult to compare and contrast land surface models in a straight-forward manner. While model intercomparison studies have been undertaken in the past, leading to significant progress on the improvement of land surface models, additional framework towards identification of model weakness is needed. Given that land surface models are increasingly being integrated with satellite based estimates to improve their prediction skill, it is practical to undertake model intercomparison on the basis of soil moisture data assimilation. Consequently, this study compares two land surface models: the Joint UK Land Environment Simulator (JULES) and the Community Atmosphere Biosphere Land Exchange (CABLE) for soil moisture estimation and associated assessment of model uncertainty. A retrieved soil moisture data set from the Soil Moisture and Ocean Salinity (SMOS) mission was assimilated into both models, with their updated estimates validated against in-situ soil moisture in the Yanco area, Australia. The findings show that the updated estimates from both models generally provided a more accurate estimate of soil moisture than the open loop estimate based on calibration alone. Moreover, the JULES output was found to provide a slightly better estimate of soil moisture than the CABLE output at both near-surface and deeper soil layers. An assessment of the updated membership in decision space also showed that the JULES model had a relatively stable, less sensitive, and more highly convergent internal dynamics than the CABLE model. 相似文献
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Associations between the autumn Arctic sea ice concentrations (SICs) and North American winter precipitation were examined using singular value decomposition. The results show that a reduced SIC in the majority of the Arctic is accompanied by dry conditions over the Great Plains, the southern United States, Mexico, eastern Alaska, and southeastern Greenland, and by wet conditions over the majority of Canada, the northeastern United States, and the majority of Greenland. Atmospheric circulation anomalies associated with the SIC variability show a wave train structure that is persistent from autumn to winter and is responsible for the covariability between the autumn Arctic SICs and North American winter precipitation. This relationship suggests a potential long-term outlook for the North American winter precipitation. 相似文献
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Hong Haoyuan Shahabi Himan Shirzadi Ataollah Chen Wei Chapi Kamran Ahmad Baharin Bin Roodposhti Majid Shadman Yari Hesar Arastoo Tian Yingying Tien Bui Dieu 《Natural Hazards》2019,96(1):173-212
Natural Hazards - The aim of this research is to investigate multi-criteria decision making [spatial multi-criteria evaluation (SMCE)], bivariate statistical methods [frequency ratio (FR), index of... 相似文献
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利用1979～2018年四川盆地134站夏季降水观测资料、ERA-Interim再分析资料以及英国气象局哈德莱中心的海表温度及海冰资料,对比分析了四川盆地夏季降水异常主模态及其同期大气环流和前期海温海冰演变特征的差异,以探讨其形成机制及前期预测信号。结果表明:四川盆地夏季降水存在两类优势空间模态:全区一致型和东西反相型,在20世纪80年代多出现东西反相型,90年代到21世纪初以一致型为主,进入21世纪10年代后又多表现为东西反相型。不同模态所对应的大气环流和海温海冰的演变具有明显差异,全区一致型降水分布受低纬系统影响显著,在500 hPa高度场上主要表现为西太平洋副热带高压的位置及强度异常;850 hPa风场为辐合或辐散特征,受到来自孟加拉湾、南海、西太平洋三条水汽通道的共同影响,其中与南海水汽通道的相关性最高,一致型降水多/少年水汽在盆地区域南北边界为同收/同支;环流可能受到前期ENSO事件衰减的显著影响。东西反相型降水分布受中高纬环流的影响较大,在500 hPa高度场上的特征类似于极地欧亚型（POL）遥相关;水汽在区域南北边界为一收一支,西多东少型为南收北支,而西少东多型为北收南支,与西太平洋水汽通道关系显著;环流可能受到前期北极海冰异常的影响。 相似文献
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Daily rainwater samples collected at Lijiang in 2009 were analyzed for pH, electrical conductivity, major ion (SO4 2?, Cl?, NO3 ?, Na+, Ca2+, Mg2+, and NH4 +) concentrations, and δ18O. The rainwater was alkaline with the volume-weighted mean pH of 6.34 (range: 5.71 to 7.11). Ion concentrations and δ18O during the pre-monsoon period were higher than in the monsoon. Air mass trajectories indicated that water vapor from South Asia was polluted with biomass burning emissions during the pre-monsoon. Precipitation during the monsoon was mainly transported by flow from the Bay of Bengal, and it showed high sea salt ion concentrations. Some precipitation brought by southwest monsoon originated from Burma; it was characterized by low δ18O and low sea salt, indicating that the water vapor from the region was mainly recycled monsoon precipitation. Water vapor from South China contained large quantities of SO4 2?, NO3 ?, and NH4 +. Throughout the study, Ca2+ was the main neutralizing agent. Positive matrix factorization analysis indicated that crustal dust sources contributed the following percentages of the ions Ca2+ 85 %, Mg2+ 75 %, K+ 61 %, NO3 ? 32 % and SO4 2? 21 %. Anthropogenic sources accounted for 79 %, 68 %, and 76 % of the SO4 2?, NO3 ? and NH4 +, respectively; and approximately 93 %, 99 %, and 37 % of the Cl?, Na+, and K+ were from a sea salt source. 相似文献