Comparisons of a Chemical Transport Model with a Four-Year (April to September) Analysis of Fine- and Coarse-Mode Aerosol Optical Depth Retrievals Over the Canadian Arctic

We compared April to September retrievals of total, fine-mode (sub-micron), and coarse-mode (super-micron) aerosol optical depth (AOD) from the Aerosol Robotic Network (AERONET) with simulations from a global three-dimensional chemical transport model, the Goddard Earth Observing System (GEOS-Chem), across five Arctic stations and a four-year sampling period. It was determined that the AOD histograms of both the retrievals and the simulations were better represented by a lognormal distribution and that the successful simulation of this empirical feature as well as its consequences (including a better model versus retrieval coefficient of determination in log-log AOD space) represented a general indicator of model evaluation success. Seasonal (monthly averaged) AOD retrievals were sensitive to the way in which the averaging was performed; this was ascribed to the presence of highly variable fine-mode smoke in the western Arctic. The retrieved and modelled station-by-station fine-mode AOD averages showed a peak in April/May that decreased over the summer, while the model underestimated the fine-mode AOD by an average of about 0.004 (～6%). Both the retrievals and simulations showed seasonal coarse-mode AOD variations with a peak in April/May that was attributed to Asian and/or Saharan dust. The model's success in capturing such weak seasonal events helps to confirm the relevance of the separation of the fine and coarse modes and the general validity of model estimates in the Arctic.     

光纤时间传递系统中时钟驯服模块的设计和实现

提出了一种基于光纤时间传递系统的时钟驯服模块设计方案。介绍了系统硬件的组成。在对信道特性和压控晶振进行理论和实验分析的基础上,设计实现了适用于光纤信道特性的卡尔曼滤波算法以及驯服流程控制程序。实验测试表明：该模块能结合恒温晶振短期稳定度好和光纤时间传递系统秒脉冲长期稳定度好的优点,时间传递的精度优于0．25ns（1σ）,输出的秒脉冲的长期稳定度优于10^-14。     

区域优化Peterson模型的气溶胶光学厚度估算分析

气溶胶光学厚度作为描述气溶胶光学特性的重要参数之一, 被广泛应用于空气质量监测及辐射传输模型的大气订正等研究中。卫星遥感可快速反演获取大范围气溶胶信息, 但其产品通常因云覆盖或暗目标算法等原因而存在空间覆盖率较低的问题, 且产品时相受限于卫星过境时间。水平能见度作为描述气溶胶光学特性的另一重要参数, 由分布广泛的气象台站一日8 次固定时间多次发布。建立水平能见度与气溶胶光学厚度的转换关系, 可实现对卫星反演气溶胶光学厚度的有益补充。本文利用2001-2009 年的MODIS气溶胶光学厚度产品与中国华东地区71 个气象台站的水平能见度数据, 对描述两者转换关系的Peterson 模型进行区域优化。采用分区域高斯曲线拟合的方法, 对影响转换精度的主要参数气溶胶标高随时间变化规律开展研究和模拟。利用2010 年数据对优化模型进行精度及区域适用性验证。结果表明, 优化后模型的气溶胶光学厚度估算均方根误差为0.31, 低于原模型误差;精度基本上与单站点优化模型一致, 但在实用性方面优于单站点优化模型。     

Optical identification of the source IGR J08390-4833 from the INTEGRAL all-sky survey

Results of the optical identification of the hard X-ray source IGR J08390-4833 recently discovered in the INTEGRAL all-sky survey are presented. We show that the source is most likely a cataclysmic variable, i.e., an accreting white dwarf in a binary. Analysis of its optical light curve clearly reveals intrinsic variability on timescales of the order of an hour or longer. However, the short time of the source’s optical observations does not allow a definitive conclusion about the periodicity of the detected variability to be reached. Further optical and X-ray observations are required for a more accurate classification of the source.     

沙尘源区与下游地区沙尘期间气溶胶光学特性分析

为了解沙尘传输过程中气溶胶粒子光学性质的变化,利用2001-2008年中国北方4个站点沙尘期间的数据资料,比较分析了沙尘源区与下游地区气溶胶光学特性的差异。结果表明,沙尘期间大量粗粒子对总消光具有强烈贡献,沙尘源区和下游地区粗粒子消光分别占总消光的85.2%和65.8%。沙尘期间沙尘源区与下游地区均表现出较高的气溶胶光学厚度;而源区的Angstrom波长指数明显低于下游地区,当沙尘暴出现时会下降到零甚至负值。沙尘源区与下游区气溶胶体积尺度谱以粗模态峰为主模态峰。在波长440~1 020 nm时,气溶胶单次散射反照率随波长增大而增大,源区与下游地区的单次散射反照率分别达到0.95和0.92。沙尘源区气溶胶的不对称因子大于下游地区,4个波段的平均不对称因子分别为0.73和0.70。     

城市气溶胶光学厚度空间格局特征多指标综合分析

本文以厦门市为例,基于MODIS影像反演的大气气溶胶光学厚度（AOD）,利用空间自相关和景观格局指数从数量、形态和结构方面综合分析了2014年各月份（5月和9月除外）AOD时空格局变化。结果表明,研究区AOD具有明显的时空分布差异,林地上空的AOD处于较低等级,建设用地上空AOD大部分处于中高等级;AOD在春夏季较大,在秋冬季较小。AOD分布存在显著正空间自相关性,而且主要存在高高（HH）、低低（LL）、高低（HL）3种聚集模式。低低聚集模式主要分布在厦门市的北部山区;高高（HH）和高低（HL）模式主要分布在本岛东北部新城和本岛外各新城的城区。在景观格局指数方面,从秋冬季节到春夏季节期间,研究区气溶胶光学厚度高等级斑块增加,景观结构趋于复杂,景观异质性增加。对AOD时空格局变化进行多指标综合分析可以更加深入、细致、全面地刻画气溶胶的变化规律,有助于精确评估气溶胶对环境、气候等的影响,为城市可持续发展提供决策支持。     

Recent Trends in Satellite-Derived Chlorophyll and Aerosol Optical Depth Together with Simulated Dimethylsulfide in the Eastern China Marginal Seas

The biogenic compound dimethylsulfide(DMS)produced by a range of marine biota is the major natural source of re-duced sulfur to the atmosphere and plays a major role in the formation and evolution of aerosols,potentially affecting climate.The spatio-temporal distribution of satellite-derived chlorophyll_a(CHL)and aerosol optical depth(AOD)for the recent years(2011-2019)in the Eastern China Marginal Seas(ECMS)(25°-40°N,120°-130°E)are studied.The seasonal CHL peaks occurred during late April and the CHL distribution displays a clear zonal gradient.Elevated CHL was also observed along the northern and western coastlines during summer and winter seasons.Trend analysis shows that mean CHL decreases by about 10%over the 9-year study period,while AOD was higher in south and lower in north during summertime.A genetic algorithm technique is used to calibrate the key model parameters and simulations are carried out for 2015,a year when field data was available.Our simulation results show that DMS seawater concentration ranges from 1.56 to 5.88 nmol L^?1 with a mean value of 2.76 nmol L^?1.DMS sea-air flux ranges from 2.66 to 5.00mmol m^?2 d^?1 with mean of 3.80mmol m^?2 d^?1.Positive correlations of about 0.5 between CHL and AOD were found in the study region,with higher correlations along the coasts of Jiangsu and Zhejiang Provinces.The elevated CHL concentration along the west coast is correlated with increased sea-water concentrations of DMS in the region.Our results suggest a possible influ-ence of DMS-derived aerosol in the local ECMS atmosphere,especially along the western coastline of ECMS.     

基于灰度共生矩阵的Grove山地区冰裂隙探测

冰裂隙是内陆冰盖野外考察最危险因素之一。冰裂隙的识别保证了野外科学考察安全路线的选择,同时为研究冰体的运动提供了参考信息。本文基于SPOT5光学影像,利用灰度共生矩阵对东南极Grove山地区冰裂隙进行初步识别,并结合野外考察导航路线对结果进行分析,为野外考察提供参考。     

河套盆地西山咀凸起区湖相地层的发现及其测年

在位于河套盆地内部的西山咀凸起区发现了典型的湖滩岩、湖蚀平台和一套较完整的湖相沉积地层。基于海拔高程的推断,地貌和地层沉积记录指示西山咀地区曾经存在过一个海拔达到1080 m上下的古湖面。完整的沉积地层反映西山咀凸起区经历了深湖相-滨湖相-冲洪积相-风成堆积的演变过程。光释光测年结果表明,在距今65 ka 前后,“吉兰泰-河套”古大湖在西山咀地区曾经连通;但在距今约50~30 ka 湖面再没有上涨。这一研究表明：在MIS 3 阶段某一时期,该地区的古湖面发生衰退。随后,再没有发育高于“吉兰泰-河套”古大湖最高湖面的湖泊。     

Optical processing of structural contour maps

Optical processing is a fast, easy, economical, and reliable method of quantifying map patterns. A reduced transparency of a zebra-like pattern, obtained by blackening in alternate contour bands of a map, is used as input to an optical system of a laser source and objective lens to produce Fourier transforms. By sampling the intensity distribution across the transform, information about the spatial frequency (periodicity) and orientation in the original map can be inferred. Parameters used for comparing the map images are the values of intensity distribution in the transform. These intensities are normalized and subjected to comparison using various similarity methods. Cross-multiplication of the intensities is suggested as a measure of vectorial comparison of the orientations. By plotting the directional intensities into a polar coordinate system, rose diagrams are prepared for visual comparison. Optically derived parameters are independent of scale and other restrictive and limiting requirements as demanded in techniques of map analyses based on numerically derived parameters. The technique can be used in analyzing other pictorial data including aerial photographs, rock-fabric diagrams, and thin sections.