辽宁地区主要断裂活动性和地震危险性评估     

曹凤娟  贾丽华  李梦莹  王松阳 《地震地磁观测与研究》2021,42(2):143-144

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2007-2019年太湖藻型和草型湖区叶绿素a变化特征及影响因子     

吴东浩  贾更华  吴浩云 《湖泊科学》2021,33(5):1364-1375

基于太湖31个站点的逐月监测数据,分析了2007-2019年太湖藻型湖区和草型湖区的叶绿素a变化特征,并分析研究不同环境因子对不同类型湖区叶绿素a的影响.结果表明,近年来太湖不同类型湖区的总磷浓度和叶绿素a浓度变化基本一致,均呈波动上升趋势.不同类型湖区的总磷浓度拐点均为2015年,叶绿素a浓度拐点均为2016年.最低月平均水温、前冬积温、年平均水温、年均风速与藻型湖区和草型湖区叶绿素a浓度均呈显著相关.沉水植物分布面积与草型湖区叶绿素a浓度之间呈显著相关.湖西区年内和年度降雨剧烈变化,湖西区年降雨量与不同类型湖区当年叶绿素a浓度的关系不明显,5日极端降雨量与不同类型湖区下年度叶绿素a浓度均呈显著正相关.太湖蓝藻水华强度在短期内可能仍会处于较高水平,迫切需要高度重视高温时段太湖蓝藻打捞处置工作,保障饮用水安全;同时,要进一步加强湖西区强降雨期间的非点源污染防控措施研究,推动入湖污染通量稳步降低,并探索东西山之间及东茭咀附近水域沉水植物生态修复技术,降低风浪扰动作用,尽快恢复相关重要水域的沉水植物.  相似文献   

基于遥感影像的建筑物空间分布方法在地震灾害损失预评估中的应用     

朱达邈  王东明 《震灾防御技术》2021,16(3):510-518

房屋建筑数据是地震重点危险区预评估工作的基础,需基于获取到的房屋建筑信息开展人员伤亡、经济损失、救援物资需求等预评估工作。历年地震重点危险区预评估工作能够通过现场调查得到的房屋建筑信息占比极小,仅能进行抽样调查。因此,为批量完成危险区内全部房屋建筑损失估算,需基于遥感影像获取房屋建筑矢量数据,并建立数据库。为实现全国地震重点危险区预评估工作中大批量建筑物矢量化数据的快速获取,本文采用基于遥感影像的建筑物空间分布数据批量获取方法,得到地震重点危险区内建筑物空间矢量数据,结合现场抽样调查得到的建筑物属性信息,建立地震重点危险区建筑物空间分布数据库,进而为地震重点危险区灾害损失预评估工作提供数据基础。本文采用的方法可广泛应用于地震重点危险区房屋建筑信息获取工作中,可提高工作效率,降低工作成本,提升预评估工作的科学性和准确性。  相似文献   

青藏高原东北侧7月少雨流型的研究     

王金花  马镜娴  谢金南 《高原气象》2004,23(6):875-883

根据青藏高原东北侧9个代表站1951—2000年历年7月的降水量资料,确定了5个多、少雨年。再用NCEP／NCAR再分析格点资料,分别求出850,700,600,500,200,100,70,50和30hPa共计9个层次上多、少雨年份7月月平均合成位势高度场。计算了500hPa合成高度场与其余各个层次合成高度场流型的相似性度量以及各个层次的东亚北风指数。结果表明：20世纪80年代提出的1300hPa层次上高原东北侧“西正东负”少雨流型的特征在850～70hPa整层大气中仍然存在。同时．7月少雨流型与平流层低层70,50hPa前期环流特征之间也存在联系,这些结果可供西北干旱形成研究和干旱预测业务参考。  相似文献   

The Venusian induced magnetosphere: A case study of plasma and magnetic field measurements on the Venus Express mission     

E. Kallio  T.L. Zhang  R. Jarvinen  P. Janhunen  J.-A. Sauvaud  J.-J. Thocaven  H. Andersson  K. Brinkfeldt  M. Holmström  M. Yamauchi  W. Baumjohann  A.J. Coates  D.O. Kataria  K.C. Hsieh  M. Grande  T. Säles  P. Riihelä  N. Krupp  J.G. Luhmann  S. Orsini  A. Mura  M. Maggi  P. Brandt  K. Szego  R.A. Frahm  J.R. Sharber  P. Bochsler 《Planetary and Space Science》2008,56(6):796-801

Plasma and magnetic field measurements made onboard the Venus Express on June 1, 2006, are analyzed and compared with predictions of a global model. It is shown that in the orbit studied, the plasma and magnetic field observations obtained near the North Pole under solar minimum conditions were qualitatively and, in many cases also, quantitatively in agreement with the general picture obtained using a global numerical quasi-neutral hybrid model of the solar wind interaction (HYB-Venus). In instances where the orbit of Venus Express crossed a boundary referred to as the magnetic pileup boundary (MPB), field line tracing supports the suggestion that the MPB separates the region that is magnetically connected to the fluctuating magnetosheath field from a region that is magnetically connected to the induced magnetotail lobes.  相似文献   

The magnetic field near Mars: A comparison between a hybrid model, Mars Global Surveyor and Mars Express observations     

H. Frilund  M. Yamauchi  P. Janhunen  J.-A. Sauvaud 《Planetary and Space Science》2008,56(6):828-831

Mars Express (MEX) does not carry its own magnetometer which complicates interpretation of ASPERA-3/MEX ion measurements. The direction of the interplanetary magnetic field (IMF) is especially important because it, among other things, determines the direction of the convective electric field and orientation of the cross tail current sheet and tail lobes. In this paper we present a case study to show the properties of the magnetic field near Mars in a quasi-neutral hybrid (QNH) model at the orbits where the Mars Global Surveyor (MGS) has made measurements, present a method to derive the IMF clock angle by comparing fields in a hybrid model and the direction of the magnetic field measured by MGS by deriving the IMF clock angle. We also use H⁺ ring velocity distribution observations upstream of the bow shock measured by the IMA/ASPERA-3 instrument on board MEX spacecraft. These observations are used to indirectly provide the orientation of the IMF. We use a QNH model (HYB-Mars) where ions are modeled as particles while electrons form a mass-less charge neutralizing fluid. We found that the direct MGS and non-direct IMA observations of the orientation magnetic field vectors in non-crustal magnetic field regions are consistent with the global magnetic field draping pattern predicted by the global model.  相似文献   

Variations of the magnetic field near Mars caused by magnetic crustal anomalies     

R.A. Frahm  E. Kallio  A. Fedorov 《Planetary and Space Science》2008,56(6):856-860

The possible avenues for photoelectron transport were determined during southern hemisphere winter at Mars by using a mapping analysis of the theoretical magnetic field. Magnetic field line tracing was performed by superposing two magnetic field models: (1) magnetic field derived from a three-dimensional (3D) self-consistent quasi-neutral hybrid model which does not contain the Martian crustal magnetic anomalies and (2) a 3D map of the magnetic field associated with the magnetic anomalies based on Mars Global Surveyor magnetic field measurements. It was found that magnetic field lines connected to the nightside of the planet are mainly channeled within the optical shadow of the magnetotail whereas magnetic field lines connected to the dayside of the planet are observed to form the remainder of the magnetosphere. The simulation suggests that the crustal anomalies create “a magnetic shield” by decreasing the region near Mars which is magnetically connected to the Martian magnetosphere. The rotation of Mars causes periodic changes in magnetic connectivity, but not to qualitative changes in the overall magnetic field draping around Mars.  相似文献   

Dependence of the Characteristics of Solar Wind Discontinuities and Shocks with Heliolatitude and Radial Distance     

A. Dickson Benjamin  S. R. Prabhakaran Nayar 《Solar physics》2008,252(1):195-207

The distribution of the shocks in the heliosphere and their characteristic variations are investigated using Ulysses observations. The jumps in solar wind velocity, IMF magnitude, and proton density across the shocks and discontinuities are evaluated and used to characterize them. The distribution of these discontinuities with respect to heliolatitude ± 80° and with radial distance 1 to 5 AU are analyzed during solar minimum and solar maximum to understand their global behavior. It is noticed that the jumps in solar wind parameters associated with shocks and discontinuities are more prominent during the second orbit of Ulysses, which coincided with the maximum phase of solar activity.  相似文献   

Spatially distributed modelling of soil erosion and sediment yield at regional scales in Spain   总被引：4，自引：0，他引：4  

Joris de Vente  Jean Poesen  Gert Verstraeten  Anton Van Rompaey  Gerard Govers 《Global and Planetary Change》2008,60(3-4):393-415

Initiated by the need to quantify erosion rates and the impacts of global changes on erosion, several attempts have been made to apply erosion models at regional scales. However, these models have often been directed towards on-site soil erosion estimates, emphasising sheet and rill erosion processes, and disregarding gully erosion, channel erosion and sediment transport. These models are therefore of limited use for the assessment of sediment yield, off-site impacts of erosion, and for the development of environmental management to control these impacts at regional scale. This study analyses and compares three spatially distributed models for the prediction of soil erosion and/or sediment yield at regional scales: the WATEM-SEDEM model that is based on the empirical Revised Universal Soil Loss Equation (RUSLE) in combination with a sediment transport equation, the physics-based Pan European Soil Erosion Risk Assessment model (PESERA), and a newly developed Spatially Distributed Scoring model (SPADS). The three models were applied to 61 Spanish drainage basins and model predictions were evaluated against data on measured reservoir sedimentation rates. Global data sets on land use, climate, elevation and soil characteristics were used as model input for WATEM-SEDEM and SPADS, whereas published soil erosion estimates of PESERA at 1 km² resolution were used directly. SPADS and WATEM-SEDEM provided best results after separate calibration for basins with a Sediment Delivery Ratio (SDR) higher than 5% and those with an SDR lower than 5%. In this way, SPADS explained 67% of variation in sediment yield, while WATEM-SEDEM explained 48% of the variation. PESERA represents a promising alternative to the use of empirical models at the regional scale as it can be applied to very diverse environments with little calibration. However, PESERA provides soil erosion rates and not sediment yield estimates. For most basins PESERA soil erosion rates vary between fifty and close to zero percent of total sediment yield. Two major factors may explain this discrepancy between modelled soil erosion rates and measured sediment yield. First, it may be that PESERA underestimates soil erosion under Mediterranean conditions, although PESERA soil erosion rates are of the same order of magnitude as erosion rates measured in erosion plot studies. Second, gully-, river channel erosion and sediment transport processes may be much more important than sheet- and rill erosion for regional scale sediment yield in these environments. These issues therefore require further attention in future model development. Although spatially lumped models provide better predictions of sediment yield at the basin scale, and while validation of the predicted spatial patterns of sources and sinks of sediment requires further research, spatially distributed models are expected to be of value to support management decisions regarding the assessment of on-site and off-site impacts of erosion at the regional scale.  相似文献   

全新世时期北京-张家口地区与黄土高原地区风成系统的差异   总被引：7，自引：3，他引：4  

秦小光  吴金水  蔡炳贵  顾兆炎  刘东生 《第四纪研究》2004,24(4):430-436

近年来,中国北方的沙尘暴对北京地区的影响越来越受到人们的重视,从地质记录上分析研究北京—张家口地区沙尘暴的粉尘来源对确定重点治理区、改善北京地区的大气环境质量具有积极意义。黄土是地质时期沙尘暴形成的风成沉积物,其粒径分布蕴含了粉尘搬运过程中的大气环境信息,本文利用黄土-古土壤沉积的粒径分布特征,分析了北京—张家口地区和黄土高原地区风成系统的差异,并根据粉尘动力学原理,结合遥感信息揭示的地面风蚀痕迹,探讨了北京—张家口地区黄土粉尘的主要来源,指出北京—张家口地区和黄土高原地区分属不同的风成系统,有不同的粉尘源区和不同的大气动力条件。北京—张家口地区大气动力强度大,粉尘源区近,粉尘主要来自阴山以北的内蒙古苏尼特右旗—二连浩特方向,与浑善达克沙地关系不大,也与黄土高原地区主要粉尘物源区不同  相似文献