多源信息多尺度视角的南京市街道级人口模拟研究

人口是重要的社会和生态环境因素,掌握人口信息有利于资源配置和环境管理。本文以南京市的街道级行政区域作为基本对象单元,分别从市级、市郊级和城市化度3个尺度,人口总量和人口密度2个方面,使用NPP/VⅡRS夜间灯光数据、大数据中的关注点POI数据、Landsat 8卫星OLI影像的建筑用地指数IBI,进行了人口模拟研究。结果如下：①在市级层面,人口密度模拟效果优于人口总量的,POI数据模拟效果最佳,确定性系数为0.87,其次是建筑用地指数0.81,夜间灯光数0.77;②在市郊级层面,郊区的人口密度拟合效果优于市区的;③在城市化度方面,中度城市化的街道人口密度与NPP/VⅡRS的幂函数关系最佳,确定性系数为0.99,低度和高度城市化的街道人口密度与POI的对数关系拟合效果相对好些,确定性系数分别为0.65和0.44;中度和低度城市化街道的人口总量与3个因素数据的多元线性回归模型效果最佳,确定性系数分别为0.91和0.78。结果说明中度城市化街道的人口模拟效果最好。本文研究拓展了城市人口估算的广度和深度,可为相关工作提供思路上的借鉴。     

三种活跃火遥感产品（MODIS C6、VIIRS V1和VIIRS J1）一致性与差异性对比

MODIS C6、VIIRS V1和VIIRS J1是NASA火灾信息资源管理系统（FIRMS）2020年首次同步发布的三套全球活跃火遥感产品。鉴于卫星过赤道时间、空间分辨率、火情监测算法有别,分析MODIS和VIIRS不同活跃火产品监测结果一致性和差异性,对明确不同火产品的适用性至关重要。利用中南半岛同年活跃火矢量产品,通过GIS渔网（1 km）定量分析不同时间尺度（全年、旱/雨季和昼/夜）活跃火发生的频次与强度特征,横向对比了三套活跃火产品的一致性与差异。结果表明：① 中南半岛三套产品逐月发生频次一致性最高,逐日次之,逐时最低。全年“有火区”格网占比37.23%,其中VIIRS相应比重三倍于MODIS,且J1略高于V1。三套产品两两比较时,VIIRS V1/VIIRS J1组合总体一致性最高,VIIRS J1/MODIS C6组合一致性最低。② 三套产品旱季“有火区”占比、活跃火发生频次与强度均显著高于雨季,且VIIRS V1与J1活跃火发生强度空间分布一致性更高。旱季V1活跃火累积发生频次最高、发生强度更强;雨季J1相应频次最高,发生强度较强。③ 三套产品白天“有火区”占比、活跃火累积发生频次均高于夜间,发生强度空间分布一致性亦高于夜间,其中VIIRS V1与J1夜间一致性最高。且昼/夜V1活跃火累积发生频次和“有火区”占比均最高,但J1发生强度最强。④ VIIRS V1与J1监测精度更高,空间覆盖范围更广,且VIIRS V1更适用于旱季、白天和夜间活跃火相关研究,而VIIRS J1对雨季活跃火的探测水平更高,但MODIS C6的优势在于历史数据丰富。     

利用NPP/VIIRS微光数据反演夜间气溶胶光学厚度

大气气溶胶具有气候环境和健康效应,且具有明显的时空和昼夜变化特征。因此探测夜间气溶胶光学厚度（AOD）具有重要的意义。NPP/VIIRS上的昼夜通道DNB（Day Night Band）为夜间反演AOD提供了有效的数据。基于大气辐射传输理论对夜间AOD进行反演,首先,利用“背景合成法”获取夜间城市灯光真实辐射值;然后,利用改进的“消光法”反演夜间AOD。选取华北地区作为研究对象,获得了2016-03—2017-02新月日期的夜间城市灯光真实值,选择其中的2016年7月和10月的2次污染天气过程,反演了夜间AOD分布。通过北京、天津和郑州的太阳光度计地基观测结果和北京市环境质量监测站空气质量指数（AQI）对反演结果进行验证,结果表明反演结果和观测结果有较好的一致性,展示了卫星微光数据在夜间城市污染空间分布监测中的应用潜力。     

基于VIIRS数据的油气平台提取技术研究

油气平台作为海上油气资源勘探开发的主要设备之一,其数量与空间分布反映了一个区域油气资源的开发状况。普通光学影像易受天气状况影响,而雷达数据成本较高,这给油气平台的检测带来了一定的困难。由于油气平台作业过程中,需要灯光照明,同时伴气的燃烧也产生很强的灯光,因此可以通过检测灯光来实现油气平台的提取。针对VIIRS数据具有强夜间光探测能力,本文提出了一种卷积运算临界值法对海上油气平台进行提取。首先对2期不同时相的VIIRS数据进行卷积运算,对亮像元进行了增强处理,对背景像元进行弱化处理,从而明确区分疑似目标与背景,然后以0值为分界点,对疑似目标进行提取,最后利用油气平台相对静止的特性,通过邻域分析,实现油气平台的提取。结果表明,本文提出的卷积运算临界值法可以有效地提取油气平台,提取准确率约为85.4%,同时可以有效地减少由于经验阈值对提取结果造成的误差。     

Mapping impervious surface distribution in China using multi-source remotely sensed data

ABSTRACT

Impervious surface area (ISA) data are required for such studies as urban environmental modeling, hydrological modeling, and socioeconomic analysis, but updating these datasets in a large area remains a challenge due to the complex urban landscapes consisting of different materials and colors with various spatial patterns. This research explores the integration of multi-source remotely sensed data for mapping China’s ISA distribution at 30-m spatial resolution. The integration of Visible Infrared Imaging Radiometer Suite Day/Night Band (VIIRS DNB) and Moderate Resolution Imaging Spectroradiometer (MODIS) normalized difference vegetation index (NDVI) data were used to extract initial ISA with spatial resolution of 250 m using a thresholding approach. The Landsat-derived NDVI and Modified Normalized Difference Water Index (MNDWI) were used to remove vegetation and water areas from the mixed pixels that existed in the initial ISA data. The spectral signatures of these ISA data were further extracted from Landsat multispectral images and used to refine the ISA data using expert knowledge. The results indicate that the integration of multi-source data can successfully map ISA distribution with 30-m spatial resolution in China with producer’s and user’s accuracies of 83.1 and 91.9%, respectively. These ISA data are valuable for better management of urban landscapes and for use as an input in other studies such as socioeconomic and environmental modeling.     

Global mapping of urban built-up areas of year 2014 by combining MODIS multispectral data with VIIRS nighttime light data

An improved methodology for the extraction and mapping of urban built-up areas at a global scale is presented in this study. The Moderate Resolution Imaging Spectroradiometer (MODIS)-based multispectral data were combined with the Visible Infrared Imager Radiometer Suite (VIIRS)-based nighttime light (NTL) data for robust extraction and mapping of urban built-up areas. The MODIS-based newly proposed Urban Built-up Index (UBI) was combined with NTL data, and the resulting Enhanced UBI (EUBI) was used as a single master image for global extraction of urban built-up areas. Due to higher variation of the EUBI with respect to geographical regions, a region-specific threshold approach was used to extract urban built-up areas. This research provided 500-m-resolution global urban built-up map of year 2014. The resulted map was compared with three existing moderate-resolution global maps and one high-resolution map in the United States. The comparative analysis demonstrated finer details of the urban built-up cover estimated by the resultant map.     

中南半岛旱季VIIRS活跃火的空间特征与国别差异

热带是全球活跃火(active fire)的集中发生区,客观认识其空间特征、国别差异及其动态变化对评估区域生物质燃烧及其碳排放等具有重要意义。作为热带季风气候典型区,中南半岛旱季活跃火发生发展空间特征及其动态变化仍缺乏清晰认识。为此,论文利用可见光红外成像辐射仪(VIIRS) S-NPP 2012—2019年活跃火矢量数据,基于核密度与空间自相关评价了中南半岛及国别旱季尤其是其特征月份(2—4月)活跃火发生发展的密集程度、集聚特征及其动态变化。结果表明：① 中南半岛活跃火核密度低值区占比最大(79%),高值区最小(4%);柬埔寨、缅甸、老挝等经济落后国家的核密度均值明显高于泰国和越南;2012—2019年核密度高值区具有朝高海拔、向内陆与趋边境等分布特征,且柬埔寨东北部长居高值区。② 活跃火核密度中值区变化集中在1—4月,且多分布在低、高值区周围;高值区变化集中在2—4月,由柬埔寨东北部逐渐向缅甸东/西部、泰国西北部以及老挝北/南部转移。③ 半岛与5国活跃火核密度在旱季具有显著空间正相关性,空间集聚类型以“高—高”型和“低—低”型集聚为主,越南、柬埔寨等国局部自相关性强于泰国和老挝。     

Microphysical Properties of Convective Clouds in Summer over the Tibetan Plateau from SNPP/VIIRS Satellite Data

The Tibetan Plateau (TP) plays an important role in formation and development of the East Asian atmospheric circulation, climate variability, and disastrous weathers in China. Among the many topics on TP meteorology, it is critical to understand the microphysical characteristics of clouds over the TP;however, observations of the cloud microphysics in this area are insufficient mainly due to sparse stations and limited cloud physical data. The Visible Infrared Imaging Radiometer Suite (VⅡRS), onboard the Suomi National Polar-orbiting Partnership (SNPP) satellite, has an improved imaging spectroradiometer with 17 channels of 750-m moderate resolution and 5 channels of 375-m image resolution. The high-resolution instrument has an advantage for observing the small or initial convective clouds. Based on the methodologies that we proposed before for retrieving cloud microphysical properties from SNPP, an automated mapping software package named Automatic Mapping of Convective Clouds (AMCC) has been developed at the scale of satellite swath. The properties of convective clouds are retrieved by AMCC and their values are averaged over 0.33°×0.33° grids based on the SNPP/VⅡRS satellite data over the TP during the summers of 2013-17. The results show that:(1) the temperature of lifting condensation level (TLCL) at Naqu meteorological station and the cloud base temperature (Tb) retrieved from VⅡRS are linearly correlated, with a correlation coefficient of 0.87 and standard deviation (STD) of 3.0℃;(2) convective clouds over the TP have the following macro-and microphysical properties. First, the cloud base temperature (Tb) is about -5℃, the cloud base height above the ground (Hb) ranges between 1800 and 2200 m, and the cloud water content is low. Second, the cloud condensation nuclei concentration (NCCN) is between 200 and 400 mg-1 with 0.7% in maximum supersaturation (Smax);consequently, the condensation growth of water cloud droplet with less NCCN and higher Smax is fast. Third, because the precipitation initiation depth (D14) varies within 1500-2000 m and 500-1000 m at the Yarlung Zangbo River basin and southern Tibet, respectively, the clouds over these areas are more prone to precipitation. Fourth, mean height of the cloud top above sea level (Htop) is between 10 and 13 km, but the cloud depth (Dcld) is rather small, which is about 5000 m in southern TP and gradually reduces to 2500 m in northern TP. Fifth, the glaciation temperature (Tg) ranges from -30℃ in central and southern TP to -25℃ in northern TP, which, combined with the warmer Tg and the Tb less than 0℃, leads to the domination of ice process in the clouds;(3) the macro-and microphysical properties of convective clouds over the TP explain why rainfall there is frequent and lasts over a short time with small amount and large rain drops.     

Development of S-NPP VIIRS global surface type classification map using support vector machines

With the launch of the Joint Polar Satellite System (JPSS)/Suomi National Polar-orbiting Partnership (S-NPP) satellite in October 2011, many of the terrestrial remote sensing products generated from Moderate Resolution Imaging Spectroradiometer (MODIS), such as the global land cover map, have been inherited and expanded into the JPSS/S-NPP mission using the new Visible Infrared Imaging Radiometer Suite (VIIRS) data. In this study, an improved algorithm including the use of a new classifier support vector machines (SVM) classifier was proposed to produce VIIRS surface type maps. In addition to the new classification algorithm, a new post-processing strategy involving the use of new ancillary data to refine the classification output is implemented. As a result, the new global International Geosphere-Biosphere Programme (IGBP) map based on the 2014 VIIRS surface reflectance data was generated with a 78.5 ± 0.6% overall classification accuracy. The new map was compared to a previously delivered VIIRS surface type map, and to the MODIS land cover product. Validation results including the error matrix, overall accuracy, and the user’s and producer’s accuracy suggest the new global surface type map provides similar classification accuracy compared to the old VIIRS surface type map, with higher accuracy achieved in agricultural types.     

NPPVIIRS数据反演气溶胶光学厚度

利用NPP卫星的VIIRS传感器数据,基于暗像元法反演陆地气溶胶光学厚度AOD。首先,根据红外波段的归一化植被指数NDVI来对暗像元进行识别;然后,利用6S软件进行辐射传输计算构建查找表;最后,根据VIIRS数据从查找表插值得到AOD,并对其进行海拔校正。选取华北地区作为反演实验区,获得了2013年9月1日的气溶胶分布。利用AERONET北京站太阳光度计地基观测结果对反演结果对比验证,发现二者具有显著的相关性,相关系数达到0.7920。将2013年9月1日的MODIS AOD产品与本研究反演的AOD进行比对,发现二者分布趋势一致,相关系数为0.7059,相关性显著。反演结果表明,本文算法反演陆地AOD效果较好,为大气颗粒物环境监测提供了良好方法手段和数据源。