不同植被LAI的MODIS反演及其在青藏高原东部的应用

应用Terra和Aqua卫星的MODIS资料和三维叶分布模式,结合MODIS陆地植被覆盖产品数据,估算了6种生物群落的LAI,并与我国西北地区叶面积仪观测结果进行了对比和分析。结果表明,从两颗卫星连续8天的观测资料可以估算出LAI,反演结果的相对误差基本在±20%以内,平均相对误差为13.7%,说明该方法可以反演实际植被的LAI;根据植被类型的差异,建立了6种生物群落LAI与NDVI的指数关系,相关性较好;青藏高原东部的LAI时间变化有不一致性的特征,反映了不同生物群落的生物学特性的差异;不同季节的LAI变化在空间上有很大差异,说明本研究区域西部冷、干和高原东部相对暖、湿的复杂气候特征。     

利用ASTER数据估算2002年4月阿克苏地表特征和植被参数

利用ASTER卫星可见光和短波红外波段数据,估算了2002年4月12日阿克苏地区地表特征参数(地表温度T、地表反射率α)和植被参数(归一化植被指数NDVI、修正的土壤调整植被指数MSA-VI、植被覆盖度Pv和叶面积指数LAI等)。结果表明,各种植被参数在沙漠地区较小,而在绿洲中的值较大。同时本文认为ASTER遥感数据有较高的地面分辨率,利用它可以更好地反映地表的植被参数及地表特征参数状况;还指出了ASTER卫星数据在沙漠绿洲中的适用性。     

基于NOAA AVHRR NDVI的西藏拉萨地区植被季节变化

根据每周的NOAA全球植被指数(GLOBAL VEGETATION NDVI,GVI),分析了西藏拉萨地区1985-1999年GVI的变化趋势及其与降水、气温等主要气候要素的相关性,并选择沿91°E和30°N两条区域内典型的样本带,进一步分析了这两个样本带上基于1 km分辨率NOAA NDVI反映的地表植被随季节的变化情况.研究表明,1985-1999年长时间序列的NOAA GVI反映了拉萨地区以天然植被为主的植被覆盖的生长特点,包括季节和年际变化.自20世纪80年代中期到90年代末拉萨地区以天然植被为主的植被覆盖状况有所好转;拉萨地区NDVI值对降水的变化很敏感,月平均NDVI和月降水总量之间存在明显的相关,其相关系数达0.75,而与温度的相关系数为0.63.     

基于植被生长规律的陕西省植被遥感分类

植被类型的差异除了可表现为光谱差异外,还可表现为植被生长规律的差异。植被生长以年为周期,在这个生长周期内不同植被类型有着各自的生繁衰枯的物候节律,表现出不同的生长规律。归一化植被指数NDVI是植被生长状况的敏感指示器,一年内的NDVI所构成的NDVI的时间序列曲线是表征植被生长规律的理想方法,因此利用NDVI时间序列进行植被分类是完全可行的。利用2004年全年的MODIS资料,选取距离星下点周围1000 km以内完全包含陕西省行政区域的晴空(包括部分晴空)250 m分辨率资料计算NDVI,采用NDVI多时相最大值合成法(MVC),生成了一年的月合成NDVI数据集产品,应用ISODATA算法进行非监督动态聚类。在地理信息系统的支持下,结合以往的植被类型、土地利用、种植制度区划、电子地图等辅助地理信息数据,对分类结果进行了解译和验证,并分析了各类植被类型的NDVI时间序列曲线。表明分类结果能客观地反映植被分布的地域性;各类NDVI曲线之间差别显著,有着明显的可分性,它们如实地刻画了各种植被的生长规律,并能区分植被生长规律的细微差异。     

黄河源区植被变化趋势及其对气候变化的响应过程研究

利用1982～2001年NOAA/AVHRR(美国大气海洋局卫星/甚高分辨率辐射计)NDVI(归一化植被指数)资料、2000～2008年EOS/MODIS(地球观测系统卫星/中等分辨率成像光谱仪)NDVI资料以及1982～2008年黄河源区的玛多、玛曲和兴海气象台站逐月气温和降水资料,分析了黄河源区玛多、玛曲和兴海地区...     

利用卫星遥感资料估算区域尺度空气温度

空气温度是地球大气系统能量和水分循环的关键参数,气象台站观测的空气温度是单点观测的,空间代表性较差,在区域尺度模型中应用还存在一些问题,作者提出了一个从卫星遥感资料直接反演空气温度的新方法。基于NOAAAVHRR资料反演的地表温度(Land Surface Temperature,T_(LS))和地面观测的空气温度(Air Temperature,T_a)的相关关系,建立了稀疏植被区域不同高程范围的空气温度遥感估算统计方法;基于NDVI和T_(LS)的梯形空间特征关系,建立了在中、高植被覆盖区域的空气温度遥感估算物理方法。经检验,稀疏植被区域空气温度反演绝对误差在1.5～1.8℃之间,中、高植被覆盖区域空气温度反演平均绝对误差为1.61℃,表明作者提出的空气温度遥感反演方法是可行的。     

西北地区陆地生态系统植被状态参数业务化遥感研究

植被指数(NDVI)和叶面积指数(LAI)是两个非常重要的陆地生态系统植被状态参数.我们首先利用最大值(MVC)合成方法使用先进遥感数据如MODIS、AVHRR3等得到旬合成植被指数(NDVI),然后利用最新的经验方法针对不同的陆地生态系统类型反演得到叶面积指数,重点研究了我国沙尘暴发生频率较高的我国西北地区植被覆被状态及其变化情况.植被指数能够反映区域,乃至全球范围植被年季状态,用于监测陆地生态系统植物光合作用活动及其变化.植被指数作为一个基础参数能够用于计算反演更高级别的陆地生态系统状态参数.叶面积指数直接影响植被的光合作用,蒸腾作用的变化和陆面过程的能量平衡状态.在沙尘暴预测研究中使用的起沙过程模型需要将叶面积指数作为一个关键输入变量,另外,绝大多数生态过程模型模拟碳、水循环时也都需要将叶面积指数作为一个非常重要的输入变量.我们总结了最新的叶面积指数经验反演方法,针对6钟不同的陆地生态系统类型应用不同经验模型计算得到了叶面积指数.     

巴里坤植被覆盖动态变化及气象因素分析

利用2003-2010年5-10月巴里坤250 m分辨率的EOS-MODIS卫星影像数据,通过预处理、几何校正、NDVI计算以及最大值合成,并计算植被盖度,依照盖度值将地表植被总盖度划分为高、中、低覆盖三类,得到连续8 a巴里坤植被盖度的动态变化:植被总盖度在16%～44%范围内波动,2007年植被盖度相对较高,200...     

基于地理信息系统技术的土壤质地分类特征提取与数据融合

根据不同来源不同比例尺的土壤质地分布图资料(比例尺为1∶1400万,范围为中国境内)、土壤发生学分类的土壤类型分布图资料(比例尺为1∶400万,范围为中国境内)以及土壤诊断学分类的土壤类型分布图资料(比例尺为1∶500万,范围为(5～65°N,60～150°E)提取其相同的特征,借助于地理信息系统(GIS)技术,将几份土壤分类资料进行数据融合、转换得到可供集成沙尘天气数值预报系统中风沙模式使用,且符合美国农业部(USDA)土壤质地分类标准的资料.     

NPP-VIIRS卫星在西藏植被监测中的应用研究

基于GIS空间分析和数学统计方法,利用TERRA、AQUA和NPP-VIIRS卫星数据反演了西藏日土县植被归一化指数（Normalized Difference Vegetation Index,NDVI）,并对不同卫星传感器反演结果的一致性进行了检验评估。结果表明:NPP-VIIRS卫星反演的NDVI值略大于TERRA和AQUA的反演值,其估算结果与MODIS卫星估算值存在较好的相关性。NPP-VIIRS卫星可以用于西藏高原植被长势监测工作,为西藏生态文明高地建设提供更加丰富的遥感数据支撑。      

CHARACTERISTICS AND TRENDS OF CLIMATIC EXTREMES IN CHINA DURING 1959–2014

The spatial and temporal variations of daily maximum temperature(Tmax), daily minimum temperature(Tmin), daily maximum precipitation(Pmax) and daily maximum wind speed(WSmax) were examined in China using Mann-Kendall test and linear regression method. The results indicated that for China as a whole, Tmax, Tmin and Pmax had significant increasing trends at rates of 0.15℃ per decade, 0.45℃ per decade and 0.58 mm per decade,respectively, while WSmax had decreased significantly at 1.18 m·s~(-1) per decade during 1959—2014. In all regions of China, Tmin increased and WSmax decreased significantly. Spatially, Tmax increased significantly at most of the stations in South China(SC), northwestern North China(NC), northeastern Northeast China(NEC), eastern Northwest China(NWC) and eastern Southwest China(SWC), and the increasing trends were significant in NC, SC, NWC and SWC on the regional average. Tmin increased significantly at most of the stations in China, with notable increase in NEC, northern and southeastern NC and northwestern and eastern NWC. Pmax showed no significant trend at most of the stations in China, and on the regional average it decreased significantly in NC but increased in SC, NWC and the mid-lower Yangtze River valley(YR). WSmax decreased significantly at the vast majority of stations in China, with remarkable decrease in northern NC, northern and central YR, central and southern SC and in parts of central NEC and western NWC. With global climate change and rapidly economic development, China has become more vulnerable to climatic extremes and meteorological disasters, so more strategies of mitigation and/or adaptation of climatic extremes,such as environmentally-friendly and low-cost energy production systems and the enhancement of engineering defense measures are necessary for government and social publics.     

LOW-FREQUENCY CIRCULATION AND EXTENDED-RANGE FORECAST IN CONNECTION WITH AUTUMN EXTREME HEAVY RAINFALL PROCESS IN HAINAN

Observed daily precipitation data from the National Meteorological Observatory in Hainan province and daily data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis-2 dataset from 1981 to 2014 are used to analyze the relationship between Hainan extreme heavy rainfall processes in autumn (referred to as EHRPs) and 10–30 d low-frequency circulation. Based on the key low-frequency signals and the NCEP Climate Forecast System Version 2 (CFSv2) model forecasting products, a dynamical-statistical method is established for the extended-range forecast of EHRPs. The results suggest that EHRPs have a close relationship with the 10–30 d low-frequency oscillation of 850 hPa zonal wind over Hainan Island and to its north, and that they basically occur during the trough phase of the low-frequency oscillation of zonal wind. The latitudinal propagation of the low-frequency wave train in the middle-high latitudes and the meridional propagation of the low-frequency wave train along the coast of East Asia contribute to the ‘north high (cold), south low (warm)’ pattern near Hainan Island, which results in the zonal wind over Hainan Island and to its north reaching its trough, consequently leading to EHRPs. Considering the link between low-frequency circulation and EHRPs, a low-frequency wave train index (LWTI) is defined and adopted to forecast EHRPs by using NCEP CFSv2 forecasting products. EHRPs are predicted to occur during peak phases of LWTI with value larger than 1 for three or more consecutive forecast days. Hindcast experiments for EHRPs in 2015–2016 indicate that EHRPs can be predicted 8–24 d in advance, with an average period of validity of 16.7 d.     

AN ATTRIBUTION ANALYSIS OF CHANGES IN POTENTIAL EVAPOTRANSPIRATION IN THE BEIJING–TIANJIN–HEBEI REGION UNDER CLIMATE CHANGE

Based on the measurements obtained at 64 national meteorological stations in the Beijing–Tianjin–Hebei (BTH) region between 1970 and 2013, the potential evapotranspiration (ET0) in this region was estimated using the Penman–Monteith equation and its sensitivity to maximum temperature (Tmax), minimum temperature (Tmin), wind speed (Vw), net radiation (Rn) and water vapor pressure (Pwv) was analyzed, respectively. The results are shown as follows. (1) The climatic elements in the BTH region underwent significant changes in the study period. Vw and Rn decreased significantly, whereas Tmin, Tmax and Pwv increased considerably. (2) In the BTH region, ET0 also exhibited a significant decreasing trend, and the sensitivity of ET0 to the climatic elements exhibited seasonal characteristics. Of all the climatic elements, ET0 was most sensitive to Pwv in the fall and winter and Rn in the spring and summer. On the annual scale, ET0 was most sensitive to Pwv, followed by Rn, Vw, Tmax and Tmin. In addition, the sensitivity coefficient of ET0 with respect to Pwv had a negative value for all the areas, indicating that increases in Pwv can prevent ET0 from increasing. (3) The sensitivity of ET0 to Tmin and Tmax was significantly lower than its sensitivity to other climatic elements. However, increases in temperature can lead to changes in Pwv and Rn. The temperature should be considered the key intrinsic climatic element that has caused the "evaporation paradox" phenomenon in the BTH region.     

ANALYSIS OF “BIMODAL PATTERN” STORM ACTIVITY CHARACTERISTICS OF THE BAY OF BENGAL

Storms that occur at the Bay of Bengal (BoB) are of a bimodal pattern, which is different from that of the other sea areas. By using the NCEP, SST and JTWC data, the causes of the bimodal pattern storm activity of the BoB are diagnosed and analyzed in this paper. The result shows that the seasonal variation of general atmosphere circulation in East Asia has a regulating and controlling impact on the BoB storm activity, and the “bimodal period” of the storm activity corresponds exactly to the seasonal conversion period of atmospheric circulation. The minor wind speed of shear spring and autumn contributed to the storm, which was a crucial factor for the generation and occurrence of the “bimodal pattern” storm activity in the BoB. The analysis on sea surface temperature (SST) shows that the SSTs of all the year around in the BoB area meet the conditions required for the generation of tropical cyclones (TCs). However, the SSTs in the central area of the bay are higher than that of the surrounding areas in spring and autumn, which facilitates the occurrence of a “two-peak” storm activity pattern. The genesis potential index (GPI) quantifies and reflects the environmental conditions for the generation of the BoB storms. For GPI, the intense low-level vortex disturbance in the troposphere and high-humidity atmosphere are the sufficient conditions for storms, while large maximum wind velocity of the ground vortex radius and small vertical wind shear are the necessary conditions of storms.     

Revisiting the Concentration Observations and Source Apportionment of Atmospheric Ammonia

正While China’s Air Pollution Prevention and Control Action Plan on particulate matter since 2013 has reduced sulfate significantly, aerosol ammonium nitrate remains high in East China. As the high nitrate abundances are strongly linked with ammonia, reducing ammonia emissions is becoming increasingly important to improve the air quality of China. Although satellite data provide evidence of substantial increases in atmospheric ammonia concentrations over major agricultural regions, long-term surface observation of ammonia concentrations are sparse. In addition, there is still no consensus on     

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正AIMS AND SCOPE Atmospheric and Oceanic Science Letters (AOSL) publishes short research letters on all disciplines of the atmosphere sciences and physical oceanography. Contributions from all over the world are welcome.SUBMISSIONAll submitted     

A Brief Introduction to Marine Meteorological Science Experiment Base at Bohe Town,Maoming City,Guangdong Province

<正>With the support of specialized funds for national science institutions,the Guangzhou Institute of Tropical and Marine Meteorology,China Meteorological Administration set up in October 2008 an experiment base for marine meteorology and a number of observation systems for the coastal boundary layer,air-sea flux,marine environmental elements,and basic meteorological elements at Bohe town,Maoming city,Guangdong province,in the northern part of the South China Sea.     

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AIMS AND SCOPE
Atmospheric and Oceanic Science Letters （AOSL） publishes short research letters on all disciplines of the atmosphere sciences and physical oceanography. Contributions from all over the world are welcome.     

Information for Authors

AIMS AND SCOPE Atmospheric and Oceanic Science Letters （AOSL） pub- lishes short research letters on all disciplines of the atmos- phere sciences and physical oceanography. Contributions from all over the world are welcome.