基于星载激光雷达ICESat-2的雪深监测方法研究

目前,被动微波数据是积雪深度反演的主要数据源,受其较粗空间分辨率的影响,反演雪深存在较大的不确定性。激光雷达由于其较高的测高精度,在雪深监测方面具有一定的潜力,基于星载激光雷达ICESat-2数据对北疆地区2018年10月至2019年9月积雪季的雪深进行了提取。由于很难获取ICESat-2轨迹点的雪深观测资料,因此首先利用地面雪深观测数据对目前流行的被动微波雪深反演产品进行验证,获取精度可靠的雪深产品并与发展的ICESat-2监测雪深数据产品进行对比。结果表明：AMSR2雪深产品在北疆地区误差较大,整体存在高估现象,中国雪深长时间序列雪深产品精度相对可靠,以作为对比ICESat-2模拟雪深的参考数据;ICESat-2雪深与中国雪深长时间序列雪深产品在空间上以及变化趋势方面吻合度较高,但ICESat-2雪深变化更加连续,说明ICESat-2激光雷达数据不但可以提取区域积雪的深度,对积雪深度的空间变化也比被动微波数据更加敏感,可以获取更加详细的积雪深度空间变化细节,为精细化的积雪深度空间分布提供数据支撑。     

Kinematic features of a bow echo in southern China observed with doppler radar

A bow echo is a type of mesoscale convective phenomenon that often induces extreme weather and appears with strong reflectivity on radar images. A strong bow echo that developed from a supercell was observed over Foshan City in southern China on 17 April 2011. The intense gusty winds and showers caused huge losses of property and severely affected human lives. This paper presents an analysis of this strong meso- n-scale convective system based on Doppler radar observations. The isolated bow echo exhibited a horizontal scale of about 80 km in terms of reflectivity above 40 dBZ, and a life span of 8 hours. The system originated from the merging of a couple of weakly organized cells in a shear line, and developed into an arch shape as it moved through the shear zone. Sufficient surface moisture supply ensured the convective instability and development of the bow echo. The low-altitude winds retrieved from single Doppler radar observations showed an obvious rear-inflow jet along the notch area. Different from the conventional definition, no book- end anticyclone was observed throughout the life cycle. Very strong slantwise updrafts and downdrafts were recognizable from the retrieved winds, even though the spatial scale of the bow echo was small. Strong winds and induced damage on the surface are considered to have been caused by the mid-level rear-inflow jet and intense convective downdrafts.     

On the Retrieval of Volcanic Sulfur Dioxide Emissions from GOME Backscatter Measurements

We focus on the retrieval of volcanic sulfur dioxide (SO₂) emissions from an analysis of atmospheric UV backscatter spectra obtained by the Global Ozone Monitoring Experiment (GOME) spectrometer on board the ESA European Remote Sensing Satellite (ERS-2). Here, the last major eruptions of Mt. Etna on Sicily (Italy) in July/August 2001 and October/November 2002 provided an excellent opportunity to study the retrieval of SO₂ columnar amounts from ground-based, LIDAR and satellite measurements. Our study shows that the bulk of emitted SO₂ was confined in the troposphere, mainly between 700 hPa and 400 hPa which is confirmed by trajectory analysis, by LIDAR observations and AVHRR observations. The area of influence of Mt. Etna eruptions ranges from the Western Saharan Desert to Greece and the near east states and even down to the basin of Tschad, Africa. Our analysis revealed that information about the plume height of volcanic eruptions and aerosol parameters is necessary for a reliable quantitative retrieval of SO₂ from space-borne sensor data at periods perturbed by volcanic eruptions.     

光谱波段宽度对森林叶片叶绿素含量反演的影响分析

随着传感器技术的发展,高光谱数据光谱的波段宽度逐渐变窄,如何从海量的光谱数据中找到最优的光谱波段反演叶绿素含量,成为研究的难点问题。本文在测量华中农业大学狮子山6种主要树种的光谱数据和叶绿素含量的基础上,利用叶绿素指数(CI)和回归方法反演叶绿素含量,并分析了波段宽度对反演叶绿素含量结果的影响,结果发现波段宽度会影响到叶绿素反演的精度,当波段宽度为30nm时,叶绿素含量与"红边"区域(700nm-730nm)和近红外区域(770nm-800nm)叶绿素指标(CI)间的线性关系较好,决定系数可达到77.62%,均方根误差为10.6ug/cm2。     

黑体辐射定律遥感教学改革设计与实践

普朗克黑体辐射定律是遥感类课程教学的重点和难点,本文以定律分析为核心,从数值模拟大气层顶太阳光谱辐照度曲线、卫星传感器光谱响应函数卷积计算、地物行星反射率计算及地表温度反演4个方面入手,对黑体辐射定律理论教学和实践教学内容进行优化设计和教学实现。实践证明,该教学改革不仅可以使学生更容易理解和掌握黑体辐射定律揭示的基本规律,而且以此为基础,能够使学生通过实践加深对地物两大特性(反射特性和热辐射特性)的理解,提高学生对遥感类课程的兴趣。     

电磁散射模型应用于单景高分辨率SAR影像建筑物高度反演的解算方法

首先,测量建筑物叠掩量,反演出建筑物高度初值;然后,在相邻建筑物下垫面粗糙度相关的假设下,对重组后的电磁散射模型进行基于拟模拟退火的参数解算,实现了模型中未知参数的求解以及建筑物高度的反演。将此方法应用于真实Radarsat-2SAR场景中3座建筑物高度的反演,取得了反演高度相对误差均小于10%的结果。     

不同时次地基微波辐射计反演产品评估

利用北京大型活动期间探空和微波辐射计资料,采用统计方法进行评价分析,目的是了解该型微波辐射计的性能。结果表明:①总体平均:对温度,有降水时误差变化范围大,无降水时相对比较小,比较平稳;无降水时比有降水时更接近于探空观测结果。对相对湿度,误差的变化与温度比较相似,但从相对误差的变化来看,有降水时比无降水时小。无降水时反演的相对湿度与探空的比较一致。②不同时次:对温度,无降水时统计量随高度的变化规律性比较明显,趋势一致;有降水时的规律相对较差。无降水时,20:00误差比较小,比较接近探空;14:00误差比较大。有降水时,各时次误差比无降水时大,反演的20:00温度变化曲线与探空最接近。对相对湿度,无降水时统计量随高度的变化规律性比较明显,趋势较一致;有降水时的规律性相对比较差。总体来看,降水对微波辐射计影响较大,反演的20:00的资料误差小一些,5000m高度上下误差变化比较大,与云层有关。     

测云方法研究进展

定性及定量云基础参量的观测(检测)结果,对提供未来天气变化趋势的依据有着非常重要的意义。对国内外学者多年来使用的各种测云方法得出的云空间分布等情况进行了综合评述。根据不同观测手段的特点,按空基遥感、地基遥感等方法加以区分,分别对上述测云方法逐个分析并相互比较,讨论各种测云方法的利弊,为今后使用这些方法开展的各种科学研究工作提供参考,并展望未来观测研究云的可能方向。     

测绘单位文书档案管理与应用系统开发研究

数字化、信息化是当今档案事业发展趋势,本文详细介绍我院档案信息化建设过程中关于文书档案管理系统的建设背景、设计开发过程、使用情况等;系统提供了入库、查询服务、查阅、打印等功能,设计的多条件模糊检索充分考虑了用户特点和需求,具有很强的实用性。本文同时提出个人关于档案建设的发展方向与趋势等看法。     

山区地形效应对微波辐射特征与土壤水分反演的影响—以青藏高原地区为例

采用星载微波辐射计AMSR-E的低频C波段(6.925GHz),改进了山区微波辐射传输方程,以中国青藏高原地区为例,研究山区可能产生的多种地形效应对微波辐射特征以及土壤水分反演的影响。结果表明,地形效应使得垂直极化亮温最多衰减达到16K,水平极化的亮温最大增强了18K,土壤水分在地形的影响下将被高估超过最大允许误差4%。最后,利用地形效应模拟模型计算的山区地表有效发射率,为山区土壤水分的反演提出了可行的地形校正方法。