不同天气条件下脉冲激光风廓线仪测风性能

将2012年5月21日-8月16日广东省湛江市东海岛气象观测站内脉冲激光风廓线仪WINDCUBE V2与气象站内的100 m测风塔进行同步观测试验,在经过观测数据同步性调整、有效性检验和代表性样本筛选基础上,分大小风和有无降雨天气过程,对杯式测风仪、超声风速仪与激光风廓线仪的同步测风数据进行比较,结果显示:脉冲激光风廓线仪与杯式测风仪测量水平风参数的相关性较好,10 min平均风速、风向的线性拟合度均大于0.99,3 s阵风风速的拟合度大于0.96,湍流强度的拟合度大于0.67,风速标准差的拟合度大于0.79;大风情况下,激光风廓线仪对风参数的测量效果更佳。无降雨情况下,激光风廓线仪的测量效果较降雨时略好,10 min降水量小于15 mm的降雨对这款激光风廓线仪的风速、风向、湍流强度、3 s阵风风速的测量没有显著影响,对风速标准差有一定影响。当水平风速增大和有降雨时,激光风廓线仪对垂直速度的测量效果欠佳。该对比分析可为激光风廓线仪观测数据的可靠性提供参考。     

深圳气象梯度塔与测风激光雷达观测对比分析

为了更好的了解WindView 10多普勒风廓线激光雷达的准确性,2017年7月在深圳石岩气象综合观测基地进行了一次成功的风速风向观测对比试验(时间为2017年7月20—30日),利用356 m气象梯度塔与测风激光雷达测得的风数据进行了不同时次和不同高度(40、80、100和150 m)的对比,结果表明:梯度塔和雷达在300 m以下高度范围内风速风向的观测结果比较一致,各层风速风向结果的标准差、最小最大值、均值、中位数都非常接近。风速的均值偏差最小为-0.000 09 m/s,标准差偏差最小为0.002 63 m/s,风向均值偏差最小为0.169 83°,标准差偏差最小为-1.304 83°。4层高度风速风向的相关系数都很高,风速的相关系数普遍在0.95以上,风向由于360°的过零问题导致相关系数较低,但也普遍大于0.75。同时,激光雷达测得的风速均值普遍小于梯度塔,风向均值在低层小于梯度塔,在高层则偏大。验证结果表明,该型多普勒测风激光雷达是一款观测结果可靠的低层大气风廓线测量仪器。     

基于测风塔实测台风威马逊登陆过程的强风特性分析

利用广东省徐闻县西连镇90 m测风塔在1409号超强台风威马逊登陆期间获取的具备完整的台风代表性的观测数据以及处于台风外围的广东省茂名市博贺镇100 m测风塔的观测数据,对台风威马逊的近地层强风特性进行了分析,西连测风塔结果表明:风速时程曲线呈明显的"M"型分布特征,台风中心经过测风塔前后,风向沿逆时针方向大幅偏转约170°。风速随高度增加而增大,风速廓线较好地符合对数和幂指数律;台风过境前后,各强风区的风速廓线幂指数和粗糙长度呈先减小后增大的特点;粗糙陆地下垫面的风速廓线幂指数和粗糙长度较大。湍流强度和阵风系数在前外围强风区或后外围强风区较大,在前眼壁强风区或后眼壁强风区较小,湍流强度和阵风系数随高度增加而减小,基本符合指数为负值的幂指数律;粗糙下垫面对湍流强度和阵风系数有增大的作用。外围强风区和眼壁强风区的10 min风向变率变化较为平稳,而在眼区变动较为剧烈,在眼区,当风速达到最低值或次低值时,10 min风向变率幅值达到最大值。博贺测风塔结果表明其总体上与西连测风塔台风前外围和前眼壁强风区的情形相似。     

新型多普勒测风激光雷达Windcube的风参数观测与验证

2007年12月11～14日,中国科学院大气物理研究所与法国Leosphere公司在该研究所位于北京市北三环和北四环之间的325 m气象塔试验场内联合开展了一次测风激光雷达Windcube的外场演示试验.Windcube观测数据随后与325 m气象塔上的风杯风速仪测得的风速资料进行了对比,结果是:由两种手段获得的所有6...     

不同季节天气条件下风廓线雷达测风精度分析

采用建瓯风廓线雷达(CFL-06)观测资料,分析不同季节天气条件下风廓线雷达的测风精度,同时还选取了永安风廓线雷达(CFL-03)数据进行了对比分析。结果表明,四个季节在探测高度低于4 km时,获得的对称波束水平风分量差值的平均值很小,且小于0.5m·s~(-1),标准差值也比较一致,且小于10 m·s~(-1),探测精度均较好。当探测高度超过4 km后,春、冬两季对称波束水平风分量差值的平均值和标准差值开始增大,在7.1 km高度平均值和标准差值达到最大,分别为9 m·s~(-1)和28 m·s~(-1),夏、秋两季探测精度高于春、冬两季的。在探测高度低于4 km时,不同季节4种方法计算的垂直速度基本一致,以春季大气最为均匀,其次是冬季的,夏、秋两季的最差。在探测高度超过5 km后,春、冬两季4种方法计算的垂直速度偏差增加较快,最大分别为0.9 m·s~(-1)和1.0 m·s~(-1),夏季4种方法计算的垂直速度偏差较小。夏、冬季水平风向和风速测量精度优于春、秋两季的,秋季测量精度最低,水平风速标准差值在0.0～1.5 m·s~(-1)和水平风向标准差值在0～15°范围内所占比例分别只有51.6%和54.0%。总的来说,风向和风速测量精度普遍不高,需要进一步改进算法,减少计算误差,提高探测性能。     

台风莫拉克 (0908) 影响期间近地层风特性

通过对台风莫拉克 (0908) 影响范围内的33座测风塔观测资料的分析可知:台风莫拉克越靠近陆地,风场的非对称性越明显,其行进方向的左侧测风塔风向呈逆时针旋转,右侧测风塔风向顺时针旋转。在远离台风莫拉克的地方风向稳定,湍流强度变化较平稳;在台风莫拉克登陆点附近,风向、风速和湍流强度均会出现突变。台风莫拉克影响期间,湍流强度与风速的关系未出现IEC标准曲线那样随风速增大稳定减小,其I₁₅达B级和A级及以上的平均湍流强度会在风速7~17 m·s-1形成一个峰值;无论南风或北风,风速越大,各层湍流强度差异趋于减小,同等风速、高度的湍流强度偏南大风均大于偏北大风。位于台风莫拉克登陆点北侧测风塔湍流强度随风速的增加先减小后增大,最终各高度全部超过IEC标准A级曲线,而位于南侧测风塔湍流强度随风速的变化比北侧小,并随风速增大趋于标准A级曲线;另外北侧测风塔湍流强度大于南侧,且各高度偏北大风湍流强度之间的差异比南侧相应风向明显,表明北侧垂直方向的扰动更强。台风莫拉克阵风系数为1.2~1.7,其随高度变化与地形有关,一般情况下随高度升高而减小,在复杂地形条件下不符合随高度升高减小的规律。     

IEC的风机选型参数估算方法在中国的适用性研究

国际电工委员会编制的《风力发电机组设计要求》(IEC 61400-1)推荐了针对风电机组安全等级评估的极端风速和湍流强度特征值估算方法,因其简单便捷,在风电领域被广泛采用。利用全国风能资源专业观测网的193座测风塔观测数据,对IEC推荐的极端风速计算方法与我国规范推荐的基于极值I型概率分布方法进行比较,发现两种方法计算的193座塔70 m高度层50年一遇10 min平均最大风速,仅有7座测风塔较为一致,差异在±1%;IEC推荐方法的计算结果多数偏小,其中偏小10%以上的测风塔有121座,偏小30%以上的有44座测风塔,而偏大10%以上的只有9座测风塔;IEC方法计算的极值风速大幅度偏小的测风塔主要分布在台风影响的东南沿海地区,偏差较小的测风塔主要分布在西北和华北地形平缓区域,但同时偏大10%以上的测风塔也多分布在这一地区。以目前行业领域普遍采用的以15 m·s~(-1)风速的平均湍流强度作为风电机组选型指标,与严格按照规范,以15 m·s~(-1)风速段所有样本湍流强度的90%分位数处的值作为指标进行风电机组等级确定作对比,发现193座塔中有46座塔的选型是不安全的,甚至相差两个等级。     

强台风海鸥登陆期间近地层风特性分析

利用位于海南文昌市的90 m测风塔观测的强台风海鸥多层测风数据,分析了台风海鸥登陆期间近地层风场时空特征、湍流强度、垂直风切变及阵风因子等风场特性,分析结果表明:台风海鸥登陆期间,近地层各高度风速呈现"M"型双峰特征,最大风速出现在台风后风圈;台风过境前后,风向旋转了180°;近地层风速随高度升高而增大,各高度风速垂直切变符合对数和指数规律;粗糙度长度、风廓线幂指数、湍流强度、阵风系数等风场特性与风速呈负相关关系,随着风速的增加而降低;从台风外围至台风眼,粗糙度长度随风速呈现"增大-减小-增大"特征;台风眼内部风速垂直切变剧烈,前后风圈的风速垂直切变较弱;强风区湍流强度较弱,弱风区湍流强度较强;台风风圈的湍流强度随高度增加而减小,台风眼内湍流强度随高度先减小再增加;台风影响各阶段阵风系数随高度升高而减小,各高度层阵风系数遵循指数定律;阵风系数随风速的增大而减小,当风速达到一定强度时,阵风系数随风速变化不明显。     

西昌发射场L波段雷达、风廓线雷达与GPS测风对比分析

对西昌发射场L波段雷达、风廓线雷达和GPS测风数据进行对比分析,对不同季节、不同风速条件、不同高度下的风向和风速数据进行相关性分析,结果表明:发射场干季风速数据相关性较高,风向数据相关性较低,雨季风速数据相关性较低,风向数据相关性较高;随风速变大,L波段雷达和GPS测风的数据相关性越来越高,二者与风廓线雷达测风数据的相关性明显变低;在各高度层风向相关性均较高,在低层风速相关性较低,在中高层风速相关性较高。      

L波段雷达系统不同测风方法计算结果分析

根据广东阳江探空站L波段雷达系统观测的测风资料分析,测风记录用综合探测雷达测风方法与无斜距（或高度替代）测风方法计算的测风量得风层的结果,少数情况下会出现与理论值不相符的现象,两种测风方法计算的结果,有时会超出高空气象观测仪器总体测量准确度要求允许的误差范围。在雷达的仰角小于30°时,量得风层的风速小于3 m/s时,两种测风方法计算量得风层的风速基本相同（误差在允许范围内）,但风向有的相差较大,超出测量准确度要求允许的误差范围。当雷达仰角小于15°,量得风层的风速大于30 m/s时,两种测风方法计算量得风层的风向比较接近,但量得风层的风速有的却相差较大,超出测量准确度要求允许的误差范围。     

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.     

Could the Recent Taal Volcano Eruption Trigger an El Ni?o and Lead to Eurasian Warming?

正The Taal Volcano in Luzon is one of the most active and dangerous volcanoes of the Philippines. A recent eruption occurred on 12 January 2020(Fig. 1a), and this volcano is still active with the occurrence of volcanic earthquakes. The eruption has become a deep concern worldwide, not only for its damage on local society, but also for potential hazardous consequences on the Earth's climate and environment.     

VARIABILITY OF INTER-ANNUAL RELATIONSHIP BETWEEN INDIAN OCEAN DIPOLE AND HUAXI REGION’S AUTUMN PRECIPITATION

The moving-window correlation analysis was applied to investigate the relationship between autumn Indian Ocean Dipole (IOD) events and the synchronous autumn precipitation in Huaxi region, based on the daily precipitation, sea surface temperature (SST) and atmospheric circulation data from 1960 to 2012. The correlation curves of IOD and the early modulation of Huaxi region’s autumn precipitation indicated a mutational site appeared in the 1970s. During 1960 to 1979, when the IOD was in positive phase in autumn, the circulations changed from a “W” shape to an ”M” shape at 500 hPa in Asia middle-high latitude region. Cold flux got into the Sichuan province with Northwest flow, the positive anomaly of the water vapor flux transported from Western Pacific to Huaxi region strengthened, caused precipitation increase in east Huaxi region. During 1980 to 1999, when the IOD in autumn was positive phase, the atmospheric circulation presented a “W” shape at 500 hPa, the positive anomaly of the water vapor flux transported from Bay of Bengal to Huaxi region strengthened, caused precipitation ascend in west Huaxi region. In summary, the Indian Ocean changed from cold phase to warm phase since the 1970s, caused the instability of the inter-annual relationship between the IOD and the autumn rainfall in Huaxi 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.     

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.     

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     

全球贸易隐含碳变化及其影响分析

基于最新的GTAP8 (Global Trade Analysis Project）数据库,使用投入产出法,分析了2004年到2007年全球贸易变化下南北集团贸易隐含碳变化及对全球碳排放的影响。结果显示,随着发展中国家进出口规模扩张,全球贸易隐含碳流向的重心逐渐向发展中国家转移。2004年到2007年,发达国家高端设备制造业和服务业出口以及发展中国家资源、能源密集型行业及中低端制造业出口的趋势加强,该过程的生产转移导致全球碳排放增长4.15亿t,占研究时段全球贸易隐含碳增量的63%。未来发展中国家的出口隐含碳比重还将进一步提高。贸易变化带来的南北集团隐含碳流动变化对全球应对气候变化行动的影响日益突出,发达国家对此负有重要责任。     

COMPARATIVE ANALYSIS OF VARIOUS DATA OF AIR–SEA TEMPERATURE DIFFERENCE AND ITS VARIATION ACROSS SOUTH CHINA SEA IN THE PAST 35 YEARS

Using the International Comprehensive Ocean-Atmosphere Data Set(ICOADS) and ERA-Interim data, spatial distributions of air-sea temperature difference(ASTD) in the South China Sea(SCS) for the past 35 years are compared,and variations of spatial and temporal distributions of ASTD in this region are addressed using empirical orthogonal function decomposition and wavelet analysis methods. The results indicate that both ICOADS and ERA-Interim data can reflect actual distribution characteristics of ASTD in the SCS, but values of ASTD from the ERA-Interim data are smaller than those of the ICOADS data in the same region. In addition, the ASTD characteristics from the ERA-Interim data are not obvious inshore. A seesaw-type, north-south distribution of ASTD is dominant in the SCS; i.e., a positive peak in the south is associated with a negative peak in the north in November, and a negative peak in the south is accompanied by a positive peak in the north during April and May. Interannual ASTD variations in summer or autumn are decreasing. There is a seesaw-type distribution of ASTD between Beibu Bay and most of the SCS in summer, and the center of large values is in the Nansha Islands area in autumn. The ASTD in the SCS has a strong quasi-3a oscillation period in all seasons, and a quasi-11 a period in winter and spring. The ASTD is positively correlated with the Nio3.4 index in summer and autumn but negatively correlated in spring and winter.     

Retrieval of outgoing longwave radiation from COMS narrowband infrared imagery

Hourly outgoing longwave radiation(OLR) from the geostationary satellite Communication Oceanography Meteorological Satellite(COMS) has been retrieved since June 2010. The COMS OLR retrieval algorithms are based on regression analyses of radiative transfer simulations for spectral functions of COMS infrared channels. This study documents the accuracies of OLRs for future climate applications by making an intercomparison of four OLRs from one single-channel algorithm(OLR12.0using the 12.0 μm channel) and three multiple-channel algorithms(OLR10.8+12.0using the 10.8 and 12.0 μm channels; OLR6.7+10.8using the 6.7 and 10.8 μm channels; and OLR All using the 6.7, 10.8, and 12.0 μm channels). The COMS OLRs from these algorithms were validated with direct measurements of OLR from a broadband radiometer of the Clouds and Earth's Radiant Energy System(CERES) over the full COMS field of view [roughly(50°S–50°N, 70°–170°E)] during April 2011.Validation results show that the root-mean-square errors of COMS OLRs are 5–7 W m-2, which indicates good agreement with CERES OLR over the vast domain. OLR6.7+10.8and OLR All have much smaller errors(～ 6 W m-2) than OLR12.0and OLR10.8+12.0(～ 8 W m-2). Moreover, the small errors of OLR6.7+10.8and OLR All are systematic and can be readily reduced through additional mean bias correction and/or radiance calibration. These results indicate a noteworthy role of the6.7 μm water vapor absorption channel in improving the accuracy of the OLRs. The dependence of the accuracy of COMS OLRs on various surface, atmospheric, and observational conditions is also discussed.