ERA-Interim和NCEP/NCAR再分析数据气温和气压值在中天山山区适用性分析

利用在天山山区海拔超过1 500 m的气象站的逐日气温和气压数据与同期经过水平方向和垂直方向插值后ERA-Interim和NCEP/NCAR两套再分析数据进行回归分析,研究再分析数据在天山山区不同季节的适用性,并验证再分析数据偏差与气候区的一致性。结果表明:从整体上,ERA-Interim数据气压和气温的可信度优于NCEP/NCAR数据,但在局部存在差异。两套再分析数据的偏差与气候分区、高程和季节相关。中天山山区再分析数据气温偏差呈现暖偏差,而天山南坡呈现冷偏差。两套再分析数据的气温偏差在高山带呈现暖偏差,在中山带呈现冷偏差。春秋两季气温的偏差小于夏冬两季。气压的偏差在夏季低于其他三季。而偏差可能会导致以再分析数据为驱动的气候模式结果的偏差。     

气温数据栅格化中的几个具体问题

用地理信息系统软件ARC／INFO及4种空间插值方法，对中国617个气象站30年平均气温数据和1961年平均气温数据的栅格化试验发现，克立格插值方法的精度最高，反距离权重法次之，样条插值法的精度第三，趋势面插值方法的精度最低。利用多年平均气温数据和年平均气温的距平值进行气温数据的栅格化，虽然可以减少分析和计算量，但栅格化结果的精度比利用年平均气温数据直接进行栅格化的精度要低。气象站的实际高程与气象站经纬度对应的数字高程(DEM)上的高程不完全一致，但气温数据的栅格化完全依赖于DEM，用气象站实际高程建模进行气温数据栅格化的精度比用与气象站经纬度对应的DEM上的高程建模进行气温数据栅格化的精度要高。     

基于机器学习的气温要素空间插值

掌握近地表气温的空间分布对于科学理解生态环境变化和陆地-大气热力学相互作用机理等至关重要,然而气象观测站在地理空间上分布不均,为区域的气温插值带来了挑战。本文以全国711个气象站点的月平均气温为基础数据,分析了气温与经度、纬度和高程的相关性,利用随机森林、支持向量机、高斯过程回归三种机器学习方法,对中国陆地区域的气温进行了空间插值,并与反距离权重、普通克里金以及ANUSPLIN等传统的插值方法以及全球土地数据同化系统（Global Land Data Assimilation System,GLDAS）气温数据产品进行对比。结果表明：（1）在整个中国陆地区域,利用机器学习进行气温插值的精度明显高于传统的反距离权重和普通克里金插值,并且机器学习方法明显提高了夏季的气温插值精度（R2）;(2)在三种机器学习方法中,高斯过程回归表现最好,支持向量机次之,然后是随机森林,ANUSPLIN具有较高的插值精度,但是整体低于高斯过程回归模型;（3）在气象站点稀少且分布不均匀的青藏高原地区,三种机器学习方法插值精度明显高于反距离权重和普通克里金方法,且整体优于ANUSPLIN的结果,尤其是在夏季,机器...     

基于ANUSPLIN的京津冀区域逐日气温格点数据集建立方法研究

为建立一个高精度、高空间分辨率的逐日气温格点数据集,满足公共气象服务对于精确信息及实时信息的需要,利用2018年6—8月京津冀区域以及临近省区共3 974个国家级及区域气象观测站质控后的逐日气温资料,采用ANUSPLIN软件对逐日气温数据进行空间内插,得到了京津冀区域逐日气温格点数据集（0.01°×0.01°）,并分别利用反距离权重插值法、普通克里金插值法、样条函数法对逐日气温数据进行空间插值,采用相关系数（Corr）、平均绝对误差（MAE）、平均相对误差（MRE）等作为评估指标来检验插值精度。结果表明：1）ANUSPLIN软件满足了空间插值对精度及曲面平滑度的要求,能直观体现京津冀区域气温由北向南递增的空间分布特征;2）4种插值方法中,基于ANUSPLIN软件的插值结果最优,相关系数平均达0.97,其样本误差在1 ℃之内占比为90.59%,MAE为0.46 ℃,MRE为1.81%;3）插值误差较大的区域位于冀北高原、燕山丘陵及太行山脉一带,高海拔、低站点密度等是造成插值误差的主要原因。基于ANUSPLIN插值方法建立的逐日气温格点数据集具有分辨率高、空间插值误差小的优势,ANUSPLIN对气温的空间分布具有较好的预测能力。     

基于DEM的气温空间插值方法比较

基于2007—2016年新疆105个气象观测站月平均气温数据,利用GIS技术提取数字高程模型(DEM)中的经度、纬度、坡度、坡向和高程,分析气温与各地形要素之间的关系,选取普通克里金、协同克里金、多元线性回归3种空间插值方法,分别对天山以北和天山以南的气温进行插值,并通过误差分析和相关性分析对插值精度进行对比检验。结果表明:无论是天山以北还是天山以南区域,普通克里金方法更适用于夏季,协同克里金方法则更适用于冬季,多元线性回归法的整体插值精度最低。因天山南北气候差异因素,普通克里金法和协同克里金法在天山以北的插值精度优于天山以南。同时受季节特征影响,天山以北4—9月普通克里金法最优,10月至次年3月协同克里金法最优;天山以南3—9月普通克里金法最优,10月至次年2月协同克里金法最优。     

基于DEM修订的新疆区域气温空间插值精度优化研究

为研究新疆地区气温的空间变异性,以新疆66个国家气象台站1981—2010年月平均气温和30 m空间分辨率DEM数据为基础,采用传统插值法、基于DEM多元线性回归插值和基于DEM修正的空间插值方法对新疆区域气温数据进行栅格化,并分析年平均气温与海拔的相关关系。通过采用反距离权重法(IDW),普通克里格法(Kriging),样条函数法(Spline)和趋势面分析法(Trend)4种空间插值方法对气象要素进行直接插值、气温多元回归模型残差结果插值、基于DEM修正插值对比分析。通过针对插值方法进行基于MAE和RMSIE的交叉验证,结果表明传统插值方法、基于多元线性回归和基于DEM修正4种空间插值精度均为IDWKrigingSplineTrend。反距离权重(IDW)空间插值方法最优,基于DEM修正IDW插值、基于多元线性回归IDW插值与传统IDW插值精度分别是0.039、0.477、1.038,插值结果客观的表达了新疆区域气温随空间梯度的变化趋势。     

中国地面气温和降水网格化数据精度比较

采用2013年国家气象信息中心逐日的839个中国基准、基本气象站,2419个国家级地面气象站,3万个逐小时中国地面站气温和降水数据,利用ANUSPLIN、SHERPAD和OI插值方法进行网格化,比较了日尺度上不同方法插值不同站网密度站点数据的精度。结果表明:台站点数量多的插值结果,对降水或气温描述的准确性高,相关性随站点密度增加而增大,均方根误差随站点密度增加而减少。不同方法得出的相关性、均方根误差随季节变化明显,且差异较大,并具有月尺度变化特征。夏季站点数量相同的不同插值结果,降水场的相关系数、RMSE等评分指标均优于年平均,气温的相关系数则低于年平均。降水场的评估指标时间序列不确定性更大,波动范围大于气温。国家气象信息中心制作的基于气候背景场OI插值的2419站降水场和考虑高程ANUSPLIN插值的2419站气温的综合评价较好。     

近57年我国气温格点数据集的建立和质量评估

在普通克里金插值方法的基础上, 引入高程因子并充分考虑插值的边界效应, 对1951:2007年我国气温站点资料进行空间结构分析和插值, 得到我国地面气温日、月、年平均值1°×1°格点数据集。数据集的质量评估结果表明:高程在我国区域气温空间结构分析和插值中起着重要作用, 高程资料的引入有效提高了大部分高山地区的插值效果; 相比站点资料, 所建立的格点数据集在描述我国年平均气温以及季节平均气温分布时更为合理, 突出了温度场的大尺度特征; 数据集反映出了我国年平均气温变化趋势主要的空间差异; 数据集较好地反映了我国年平均气温变化状况, 1951- 2007年气温变暖幅度约为1.6 ℃, 增温速率0.28 ℃/10 a, 比全球或半球同期平均增温速率明显偏高, 且气温增暖主要发生在最近的20余年之内。另外, 格点数据集显示, 1998—2007年是1951年以来最暖的10年, 其中2006年全国平均气温距平接近2000年之前的历史最高年份1998年, 而2007年全国平均气温距平值超过1998年, 达到1951年以来的历史最高值1.3 ℃, 为最暖的一年。     

高山区多时间尺度Anusplin气温插值精度对比分析

以中国地形起伏较大的横断山区为研究区,利用研究区内51个国家气象站点1960-2014年气温数据,以高程为协变量,采用Anusplin对不同时间分辨率(年代、年均、季节、月、日)的气温数据分布进行空间插值。通过气象站点交叉验证,结合绝对误差(平均绝对误差和均方根误差)和相对误差(平均相对误差)等量化指标,对比分析各个时间尺度气温数据的插值精度。结果表明:(1)夏季插值的绝对精度和相对精度最优,年代、年均和秋季气温插值的绝对精度水平相近,春季次之,冬季气温插值的绝对精度和相对精度最差。(2)在区域气候变化趋势方面,各个时间尺度气温插值数据的变化趋势和变化率与观测值结果一致。(3)年内各月均温和各月内日均温插值结果的相对精度和绝对精度在夏季月份精度最佳,在冬季月份精度最差,且各月内日均温插值结果在绝对精度和相对精度方面均低于各月均温插值结果的精度水平。分析显示,利用Anusplin的山区气温插值,气温海拔梯度性的优劣是造成不同时间尺度气温插值精度水平不一致的主要原因。     

基于DEM的江苏气温空间插值研究

以江苏省及周边39个常规气象站点1957—2001年的月平均气温数据和90 m空间分辨率的DEM数据为基础,采用基于DEM的多元线性回归插值方法,分析多年平均气温与海拔、坡度和坡向等地形因子的相关关系,建立适合该区域的多元回归空间插值模型.同时与反距离权重法(IDW)和克里格(Kriging)插值法等传统方法的计算结果进行对比,并用交叉验证方法比较5种插值方法的精度.结果表明:该研究区各月气温递减率在 0.5~0.9 ℃/(100 m) 左右;基于DEM的多元线性回归空间插值方法(MLR)无论从插值效果还是误差精度上,均优于其他传统插值方法.插值结果客观地表达了气温与各地形要素的相关性,反映了气温的空间变异性.     

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