复杂地形对计算地表太阳短波辐射的影响

首先利用数字高程数据(DEM)、大气辐射传输模式6S以及野外观测资料计算了复杂地形(青藏高原)上地表入射太阳辐射,然后计算不考虑地形产生的地表辐射的计算误差,对误差进行归一化后得到相对辐射误差.结果显示,相对辐射误差的标准差(即相对地表辐射计算误差绝对值的统计平均值) Se随太阳天顶角的增加呈指数增长,随高度标准差的增加几乎呈线性增长,随数字高程数据的分辨率(或卫星资料的分辨率)降低而降低.利用分步拟合方法拟合了Se随太阳天顶角、高度标准差和数字高程分辨率的变化.利用拟合方程可以计算任意地形条件下,不同分辨率的卫星(或数字高程)资料在不同太阳天顶角情况下,不考虑地形复杂性产生的平均地表入射太阳辐射的计算误差,结果表明,使用中分辨率的卫星(如MODIS)资料计算地表太阳净辐射时,需要考虑地形复杂性.     

两种反演地表净太阳辐射的参数化模式在北京地区的比较

地表净太阳辐射(NSSR)在地表辐射平衡、地-气能量交换、天气预报、气候变化和太阳能利用等研究方面具有重要的作用.利用卫星遥感技术能在广大的空间区域内快速地获取地表净太阳辐射的分布情况,特别是在无人观测的极地和海洋区域.本文基于CERES/SSF卫星数据,分别采用两种地表净太阳辐射(NSSR)的卫星反演参数化模式--Li模式与Masuda模式计算了北京市上甸子地区2005年1、4、7和10月的NSSR,并将反演结果与上甸子大气本底站的实测结果进行了对比分析,并对两种模式进行了修正以更好地反演北京地区的地表净太阳辐射.结果显示:Li模式和Masuda模式反演结果与实测结果间的平均绝对误差在晴空条件下分别为62.2和50.8W/m2,在云天条件下分别为82.1和71.8 W/m2;Li模式相对于Masuda模式具有偏大的趋势,在晴天和云天条件下两者的平均绝对偏差分别为11.5和10.2 W/m2;对Li模式和Masuda模式进行线性拟合回归后能有效减小反演过程中的系统性偏差,修改后的Li模式和Masuda模式在所有天空状况下反演的月平均NSSR值与观测值问的平均绝对误差分别为-1.8和-3.4 W/m2,均方根误差分别为19.6和26.0 W/m2.     

利用TOVS资料计算我国东南地区的太阳直接辐射和散射辐射

根据多次散射理论--离散纵标法，将极轨卫星产品资料（TOVS资料）作为初始资料，利用中分辨率大气传输模式MODTRAN3分别计算出晴空和有云情况下5个层次的观测波段的太阳直接辐射和散射辐射，与国家一级探空探测的大气温、湿廓线计算出的辐射值进行比较。发现晴空状况下基本一致，有云时存在一定误差，表明由卫星的TOVS资料估算我国东部地区的晴空辐射资料，可以弥补我国辐射资料的不足。     

敦煌地区晴空散射辐射影响因子的统计特征

利用敦煌地区1981—1983年全年及1984年与1985年1～2月的日射观测资料,统计分析了敦煌地区晴空下散射辐射与太阳高度角、大气柱气溶胶垂直光学厚度等影响因子的关系,用最小二乘法拟合得到了相应的函数关系式。拟合结果表明：晴空下散射辐射与太阳高度角符合幂函数关系;晴空下散射辐射随大气柱气溶胶光学厚度线性增长。     

青藏高原纳木错站地表反照率观测与MODIS资料的对比分析

利用中国科学院纳木错多圈层相互作用综合观测研究站内太阳光度计观测的大气气溶胶光学厚度和整层气柱水汽总量,作为大气辐射传输模式的输入参数,模拟计算了2007年5月—2008年8月无雪期晴空条件下,正午时段该站的太阳总辐射和散射辐射,得到两者的比例S。基于MODIS发布的MCD43B3产品中的短波段黑空和白空反照率以及比例S,计算得到实际大气条件下地表反照率的卫星反演值,进而与地面观测值进行对比分析。结果显示,两者没有显著差别,可以满足气候模式对地表反照率绝对偏差为0.02的精度要求,且均方根偏差约为0.0156,最大偏差为0.046。雨季纳木错站的土壤含水量增加,使得该站晴空时观测的5 min平均地表反照率呈线性下降。     

青藏高原北部及其邻近地区太阳加热率和大气红外冷却率

利用中分辨率辐射计算模式(MODTRAN3)和青藏高原北部及其邻近地区格尔木、哈密、酒泉三站的探空资料，对各站点夏季太阳直接辐射、向下总辐射和净辐射进行了计算，并进一步计算了大气的太阳加热率和红外冷却率。分析了青藏高原北部及其邻近地区的加热率和冷却率的一些特点。结果表明，青藏高原北部及其邻近地区加热率在llkm高度附近有最小值，夏季红外冷却率在llkm高度附近取得最大值，太阳天顶角的变化对太阳加热率有较强的影响。     

长波区间太阳辐射对气候模拟的影响

长波区间的太阳辐射在气候模式中往往被忽略。利用国家气候中心BCC_AGCM2.0.1大气环流模式,采用矩阵算子辐射传输算法,研究了长波区间太阳辐射对气候模式辐射通量和温度模拟结果的影响。结果表明,以ISCCP和CERES辐射资料为标准,考虑长波区间太阳辐射后,长波区间晴空大气地表向下辐射通量平均误差减小2.05 W/m2,均方根误差减少1.29 W/m2;长波区间晴空大气模式顶向上辐射通量平均误差减小0.70 W/m2,均方根误差减小0.21 W/m2;长波区间有云大气地表向下辐射通量平均误差减小1.38 W/m2,均方根误差减小1.03 W/m2;长波区间有云大气模式顶向上辐射通量平均误差减小0.99 W/m2,均方根误差减小0.30 W/m2。以ECMWF再分析资料为标准,考虑长波区间太阳辐射后,赤道地区上对流层—下平流层区域温度的冷偏差得到改善,对流层顶温度平均误差减小0.27 K,均方根误差减小0.25 K。     

用卫星资料探讨有云情况下的地面辐射收支

对晴空和有云情况进行了研究，用辐射理论导出了这两种情况下卫星测值和地表太阳总辐射、净辐射的关系，将卫星测值与地面辐射观测站的实测值进行拟合，建立了几种利用卫星测值估算地面太阳总辐射和净辐射的模式，经研究比较选出几种最佳模式。据此利用卫星资料估算晴空和有云情况下的太阳总辐射和净辐射，以弥补我国辐射测站稀少，资料短缺的不足。     

利用卫星资料研究云对地面净辐射的影响

采用2002年1月、2月、7月、8月每日8～16时(北京时间)的GMS-5卫星云图资料以及相同时次的漠河和郑州两个辐射站的地面净辐射资料，通过读取红外1、红外2、水汽和可见光云图上的卫星计数值，并将卫星计数值按照GMS-5定标表转换成亮度温度和反射率，最终形成一套利用卫星资料研究云对地面净辐射影响的数据集。采用统计的方法将地面净辐射与影响地面净辐射的各因子：太阳天顶角、地面及云面反射率等有关因子进行拟合，发现地面净辐射与这些因子之间有很好的相关性，特别在引入卫星红外通道亮温值减水汽通道亮温值这一因子后，在有云状况下，拟合的相关系数有较明显的提高，原因可能是这一因子包含了云分类的信息，这一方法的提出为利用卫星资料研究云对地面净辐射的影响提出了一个新的思路。     

敦煌荒漠戈壁地区裸土地表反照率参数化研究

利用敦煌站观测资料,选取其中观测资料完整且连续性好的7个年份每年5～10月的地表净辐射四分量和土壤湿度资料,分析研究了敦煌荒漠戈壁地区裸土地表反照率与太阳高度角和表层土壤含水量之间的关系,结果表明:地表反照率与太阳高度角呈e指数关系,随太阳高度角的增大而减小,当太阳高度角大于40°时,地表反照率趋于稳定。表层土壤含水量的增大可导致地表反照率的减小,地表反照率与5 cm深土壤湿度呈线性关系。另外,建立了敦煌荒漠戈壁地区裸土地表反照率与太阳高度角和表层土壤含水量之间的双因子参数化公式,提出了一种更加适合该地区的地表反照率参数方案,并且选取2002年6～9月的实测资料对拟合的参数化公式进行模拟验证。本文所提出的地表反照率参数化方案能够很好地再现该地区裸土地表反照率的“U”型日变化特征,可准确地模拟出地表反照率的动态变化趋势。基于此参数化方案计算得到的地表反射辐射与实测值基本一致。     

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.     

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.     

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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.     

Information for Authors

正AIMS AND SCOPE Atmospheric and Oceanic Science Letters (AOSL) publishes short research letters on all disciplines of the atmosphere sciences