玉米大豆生长中后期遥感辨识的指示性特征研究

玉米和大豆是两种主要的粮食作物,及时准确地监测两者的种植面积对于产量预测和市场价格的制定具有重要的意义。利用遥感技术探究在生长季中后期能有效区分玉米和大豆的指示性特征集,为在不同实验区进行推广应用和提前玉米和大豆种植面积信息发布的时间提供技术支撑。文章以玉米和大豆为研究对象,以黑龙江和安徽省两个典型种植区为实验区,以高分一号影像为数据源,计算多种植被指数特征和两种纹理特征,同时利用特征优选方法评价特征间的相对重要性,并结合随机森林分类算法分析特征个数对精度的影响,得到不同试验区区分两者的最佳特征子集。随后根据不同实验区最佳特征子集的共同点和差异,遴选出对玉米和大豆中后期区分的遥感指示性识别特征集,并设计实验方案验证其有效性和稳定性。实验表明：在玉米和大豆生长中后期存在具有高效辨识两者的遥感特征集,能有效和稳定地增强两者的遥感识别能力;在不同实验区,基于特征优选方法可以选择出区分玉米和大豆的最佳分类特征子集,得到两者最优的识别效果,比仅仅使用原始波段特征的分类精度提升了近10个百分点,总体分类精度能够平均达到97%,Kappa系数0.96,玉米和大豆的单类分类精度平均超过95%;在不同的种植区,利用玉米和大豆的指示性特征集可以得到几乎与优选出的最佳特征子集同样的分类精度和制图效果,且具有稳定性和有效性,较最佳特征集更具推广使用意义。指示性特征集包含6种：植被指数中的比值植被指数（RVI）,差值植被指数（DVI）,转换型植被指数（TVI）,改进型叶绿素吸收比率指数（MCARI）和灰度共生矩阵（GLCM）纹理特征中的二阶矩（the Second Moment）和熵（Entropy）。     

2017年浙江临安MS4.2地震前后香泉地震台水氡异常特征分析

1 研究背景 已有研究表明,在中强及以上地震前,在震中距一定范围内分布的氡测点通常会出现氡异常,表明氡测项映震效果较好(廖丽霞,2008;孙凤霞等,2016).虽然诸多地震预报研究涉及水氡测项映震前兆机理分析及方法探索,但对于水氡动态变化异常分析及判断,尚缺少有效实例.因此,本文就2017年4月12日浙江临安MS 4.2地震前安徽香泉地震台水氡测值异常变化进行探讨,以期准确捕捉前兆异常信息,提升地震分析预报能力.     

东北地区湿度梯度下的表土植硅体的空间分布规律

植硅体的现代过程研究是恢复古环境的基础,探讨表土植硅体分布及组合特征对环境因子的响应尤为重要。沿中国东北地区年均温为4 ℃等温线采集70块表土样品,研究了单一温度因素控制下表土植硅体的空间分布规律,以期获得不同类型植硅体对降水的响应。研究结果表明:所有表土样品中植硅体丰富且数量较多,主要有棒型、尖型、块状、扇型、扁平状、短鞍型、帽型、哑铃型、齿型、三棱柱型、导管型、硅质突起、硅化气孔、弓型和多面表皮植硅体;且主要以短细胞、棒型、尖型为主,其平均百分含量之和高达80.77%,块状、扁平状、扇型次之,其他类型的植硅体含量较少。方差分析结果表明:棒型、三棱柱型、硅质突起、哑铃型和扁平状在大兴安岭、松嫩平原和长白山之间存在显著性差异,且棒型、三棱柱型、硅质突起的百分含量与年降水量具有极显著的正相关性,哑铃型的百分含量与年降水量具有极显著的负相关性。总之,年均温为4 ℃等温线上70块表土样品中植硅体类型基本相同,但不同类型植硅体的百分含量存在差异,说明本研究区域内表土植硅体组合特征对降水的响应较为敏感。     

An optimized baseflow separation method for assessment of seasonal and spatial variability of baseflow and the driving factors

Baseflow is an important component of river or streamflow. It plays a vital role in water utilization and management. An improved Eckhardt recursive digital filter(IERDF) is proposed in this study. The key filter parameter and maximum baseflow index(BFImax) were estimated using the minimum smoothing method to improve baseflow estimation accuracy. The generally considered BFImax of 0.80, 0.50 and 0.25 according to the drainage basin's predominant geological characteristics often leads to significant errors in the regions that have complex subsurface and hydrologic conditions. The IERDF improved baseflow estimation accuracy by avoiding arbitrary parameter values. The proposed method was applied for baseflow separation in the upstream of Yitong River, a tributary of the Second Songhua River, and its performance was evaluated by comparing the results obtained using isotope-tracer data. The performance of IERDF was also compared with nine baseflow separation techniques belonging to filter, BFI and HYSEP methods. The IERDF was also applied for baseflow separation and calculation of rainfall infiltration recharge coefficient at different locations along the Second Songhua River's mainstream for the period 2000–2016. The results showed that the minimum smoothing method significantly improved BFImax estimation accuracy. The baseflow process line obtained using IEDRF method was consistent with that obtained using isotope 18 O. The IERDF estimated baseflow also showed stability and reliability when applied in the mainstream of the Second Songhua River. The BFI alone in the river showed an increase from the upstream to the downstream. The proportion of baseflow to total flow showed a decrease with time. The intra-annual variability of BFI was different at different locations of the river due to varying climatic conditions and subsurface characteristics. The highest BFI was observed at the middle reaches of the river in summer due to a water surplus from power generation. The research provided valuable information on baseflow characteristics and runoff mode determination, which can be used for water resources assessment and optimization of economic activity distribution in the region.     

陕西省HFRS疫情时空分异特征及影响要素研究

肾综合征出血热（HFRS）主要是由鼠类携带传播汉坦病毒而引起的一类自然疫源性传染病,严重危害着人类健康。陕西省是我国HFRS疫情最严重的省份之一,发病率居全国前列,研究其疫情时空分异和影响要素对指导当地疫情防控具有重要意义。本研究基于2005—2017年县区尺度HFRS发病率数据,采用空间自相关、热点分析等方法分析陕西省疫情时空分异特征,并利用地理探测器探究影响疫情的主要自然环境和社会经济要素。结果表明：2005—2017年陕西省HFRS发病率明显高于全国水平,同时呈现明显的时间波动和空间聚集,平原面积占比、建设用地面积占比、人口密度等因素可以解释约20%的HFRS疫情空间分异;关中平原聚集了陕西省90%以上的高发病县区,其疫情亦呈现明显的空间分异性,主要受降水量、 NDVI、土地利用类型等因素的影响。由此可知,高发病县区聚集、且自然环境和社会经济条件明显不同的关中平原是陕西省HFRS疫情流行的关键地区。因此,建议陕西省HFRS疫情防控应当重点关注降水量、植被状况以及土地利用类型,特别是在土地城镇化水平较高、人口密度较大的关中平原进行有效的防控干预。     

Investigating the Changes in Air Pollutant Emissions over the Beijing-Tianjin-Hebei Region in February from 2014 to 2019 through an Inverse Emission Method

In recent years, China has implemented several measures to improve air quality. The Beijing-Tianjin-Hebei(BTH)region is one area that has suffered from the most serious air pollution in China and has undergone huge changes in air quality in the past few years. How to scientifically assess these change processes remain the key issue in further improving the air quality over this region in the future. To evaluate the changes in major air pollutant emissions over this region, this paper employs ens...     

2015年10月4日佛山龙卷过程的观测分析

受1522号台风彩虹外围螺旋云带影响,2015年10月4日15时28分—16时（北京时）广东佛山出现了EF3级强龙卷并造成严重灾害。为了综合分析龙卷发生的多尺度环境背景场和龙卷的结构及强度变化等特点,进行了灾情调研,航拍龙卷灾情路径,走访龙卷目击者,确认龙卷路径及灾情级别,再结合多渠道获取的龙卷视频照片等资料以及观测资料进行分析研究,结果表明:（1）产生此次龙卷的超级单体存在于台风彩虹外围螺旋云带内;龙卷向西北偏北方向移动,触地时长为32 min,受灾路径长度为31.7 km,最大受灾直径为577 m,平均速度约为60 km/h,具有“移动速度快,影响范围广,破坏力强”的特点,其移动速度快慢似与超级单体强度和地面的粗糙度有关。（2）佛山地区中高层受偏南气流控制,水汽充足,地面有弱冷空气;珠三角喇叭口地形有利于气流的辐合与局地涡旋的产生;抬升凝结高度低,风垂直切变大,有利于龙卷的生成。（3）地面自动气象站气象要素表现出受龙卷环流影响的特征。3 s极大风速的大值带和3 s最低气压的低值带以及1 h累计降水大值中心呈现出与龙卷走向一致的东南—西北向带状分布;龙卷到来时其周围自动气象站气温和气压明显降低,风速明显增大,风向明显改变;降水在龙卷靠近前5—10分钟就开始明显增大,其大值中心位于龙卷路径的西侧。龙卷离开后气压比龙卷来临前有所升高,但气温较前降低。（4）龙卷出现在钩状回波前进方向的右后侧;降水大值区与雷达组合反射率大值区基本一致。地面风场的辐合中心与龙卷触地的位置基本一致,并且钩状回波的入流区与地面偏东风区相对应。龙卷风暴单体发展高度在4 km左右,具有低重心对流的特点。其前部存在回波悬垂,一条很窄的向西北倾斜的回波大值带可能与龙卷漏斗云墙有关。对应径向速度剖面图上为一条向西北倾斜的正、负速度交界区,构成一个逆时针旋转的涡旋带,切向剖面图上存在较强的辐合。（5）龙卷发展过程中伴随着龙卷风暴顶和风暴底的逐渐下降以及单体质心的下降,中气旋与龙卷涡旋特征的顶和底也随之逐渐下降。龙卷风涡旋特征的顶高和底高都略低于中气旋,并在龙卷触地时降至最低。龙卷涡旋的切变值远大于中气旋的切变值,且在龙卷强度最强时最大。      

日极端气温的主客观预报能力评估及多模式集成网格释用

精细格点天气预报是我国未来几年天气预报业务发展重点。利用ECMWF、GRAPES等业务数值模式和广东站点观测资料,对日极端气温的主客观预报能力进行了多角度综合评估。统计结果表明,T_(max)、T_(min)的主客观预报误差均存在明显季节差异,在系统误差相对平稳的夏半年主观预报具有较明显订正能力,模式预报呈现一定流依赖特征,温度越高(低),负(正)偏差越明显;主客观预报误差空间分布均受地形影响,随着时效延长误差总体增幅不大,主观订正能力也较稳定。根据以上评估特征和网格预报特点,研究开发了一套多模式动态集成网格释用技术方案(McGF)。结果表明,相比单个模式的预报和主观预报,McGF较明显提升了T_(max)的预报技巧;T_(min)的模式预报偏差总体较T_(max)偏小,McGF提升幅度相对较小;网格释用后的广东区域预报能较合理反映气温空间和强度特征,较周边未经释用区域明显更优。     

Geochemical characterization of loess-paleosol sequences: Comparison between the upper reaches of the Hanjiang and Weihe river valleys,China

This paper aims to compare the geochemical characteristics of loess-paleosol sequences in the upper reaches of the Hanjiang and Weihe river valleyswhich are located in the semi-humid temperate zone and humid subtropical zonerespectively. The Mituosi(MTS) profile in the upper reaches of the Hanjiang River valley and the Yaohecun(YHC) profile in the Weihe River valley were selected for this comparative research. The stratigraphic characteristicscompositionchemical weathering intensityleaching rates of Ca and Namobility of major elementsand transport features of Na and Fe were analyzed with respect to depth and compared between the two profiles. This study reached the following conclusions.(1) The composition of the loess-paleosol sequences in two regions are quite similar to the average composition of the upper continental crust(UCC)indicating that the loess in the two regions came from multiple sources and was mixed well. Thereforethe loess in the two regions is considered aeolian loess.(2) Compared with the loess-paleosol sequence in the Weihe River valleythe loess-paleosol sequence in the upper reaches of the Hanjiang River valley features a darker color; a higher chemical index of alteration(CIA) value; higher leaching rates of Na and Ca; higher migration ratio(relative to K) of AlSiMgand Na; and lower migration ratio of Fe and Ca. This evidence indicates that the loess-paleosol sequence in the humid subtropical environment experienced stronger chemical weathering intensity than the loess-paleosol sequence in the semi-humid temperate zone.(3) Both the YHC profile and MTS profile record a period of climate deterioration at 6000–5000 a BP. The period punctuated the mid-Holocene Climatic Optimum(8500–3100 a BP) in the study area.     

大气环境污染优化控制的实际问题

讨论了大气环境污染优化控制理论和应用中的几个实际问题以及可以采用的一些分析和解决实际问题的方法,包括系统化分析方法、数据库的设计与实现、实用空气质量模式、优化控制问题的数学描述和求解、污染物方程及其伴随方程的线形规划求解等,同时给出了在大气环境容量规划和总量控制研究中的实现步骤。