南中国海10 m风和海面动态粗糙度特征研究

根据海面粗糙度(z_0)与海面10 m风速的关系,本文提出一种适用于海上10 m风速求解算法。通过和ERA-Interim风速比较,发现用这种动态z_0法订正的风速比固定z_0法更接近ERA-Interim风速,相关性更好。基于这种动态z_0法,利用南中国海两个海上平台站的资料,计算得到近4年逐时10 m风速及对应的动态粗糙度。分析发现风速主要集中在3~13 m·s~(-1),4—9月平均风速较小,从10月到次年3月平均风速较大。从风速日变化来看,14—17时风速达到最小;06一09时达到最大。另外,z_0有明显的季节变化和日变化,与风速变化一致。分析了台风韦森特中心过境时,气象要素的变化说明订正后的风速及z0_0符合实际观测值。     

塔克拉玛干沙漠北缘近地层气象要素变化特征

利用塔克拉玛干沙漠北缘哈德自动气象站2011年1~12月近地面层气象要素梯度观测资料,分析了该地区近地层风速、气温和相对湿度的日变化规律及四季廓线特征,并计算了哈德观测点大气稳定度和中性条件下的地表粗糙度。结果表明,哈德地区近地层0.5~10 m高度范围内气温、相对湿度和风速都呈现出明显的日变化特征。其中,风速为白天高、夜晚低,中午15:00各层风速均达到最大,凌晨04:00降至最低,其日变化幅度为1.1~1.7 m/s;14:00~15:00各层气温均为最大值,最低气温出现在05:00~06:00,昼夜温差大,最大温差为0.5 m处的16.5℃,下午17:00至次日09:00有逆温存在;相对湿度日变化在25%~55%之间,其变化规律与风速、气温的相反,凌晨06:00最大,下午15:00最低。哈德地区四季近地层风、温、湿廓线变化规律明显,14:00四季风速都呈指数形式增长,其中0.5~2 m间低层风速变化明显大于2~10 m间高层的变化;春、夏季气温主要以指数形式增长,冬季以线性增长为主,四季都有逆温存在;冬季的相对湿度明显大于其它季节。另外,哈德地区全年以东北风为主,2 m与10 m高度的主导风向一致,风频稍有差别。中性层结大气条件下的空气动力学粗糙度范围为1.42×10-11~1.7×10-3m,平均值为4.2×10-5m。     

复杂地形条件下零平面位移和空气动力学粗糙度的计算——以珠海南亚热带常绿阔叶林地区为例

空气动力学粗糙度和零平面位移是影响陆面过程的重要参数。以往对空气动力学粗糙度和零平面位移的计算往往针对均一程度较高的下垫面。以珠海南亚热带常绿阔叶林地区为例,探索了复杂地形下垫面空气动力学粗糙度和零平面位移的计算。用拟合法和粗糙元法计算了该地区下垫面的空气动力学粗糙度和零平面位移,并分析了两种方法的误差来源。计算结果表明,拟合法在这种复杂地形下的计算准确度并不理想,由于这种方法的代表范围较小,易受到周边地形影响而使测量结果不符合对数廓线的形式,从而得不到准确的结果。与拟合法相比,粗糙元法可以给出所计算下垫面的具体范围。粗糙元法计算结果的代表范围比拟合法大得多,因此,粗糙元法比拟合法更加能够反映的是该区域下垫面空气动力学粗糙度和零平面位移的总体情况。另外,粗糙元法可以计算那些因为风速资料不足无法用风速廓线直接加以计算的区域的空气动力学粗糙度和零平面位移。根据拟合法的计算结果,冬季315~45°范围内,z_0=2.96 m,d=22.48 m;45~135°范围内,z_0=1.26 m,d=8.81 m。春夏季315~45°范围内,z_0=3.90 m,d=27.00 m;45~135°范围内,z_0=1.51 m,d=14.83 m。根据粗糙元法的计算结果,东南西北四个方向1 km×1 km范围内z_0分别为0.94 m、1.28 m、1.30 m、2.08 m;d分别为13.87 m、18.79 m、19.12 m、30.61 m。     

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。     

非均一地形近地层风速廓线特点及粗糙度的研究

在中性大气层结条件下,利用35 m铁塔上五层不同高度处的有效风速,分析得到了非均一地形近地面层风速廓线特点及由粗糙元所决定的粗糙度。结果表明:(1)近地面层风速廓线一般符合对数风速廓线模式,其相关系数均大于0.985,标准偏差为0.04左右;(2)粗糙度的值为1.25 m。但由于外界流体运动状态改变可引起粗糙度出现起伏,其变化范围较大,一般在0.038～4.903 m,与风速之间的相关系数为-0.953。     

乌鲁木齐风廓线雷达探测能力评估

利用乌鲁木齐市2011年12月—2013年3月CFL-03风廓线雷达的风探测数据与同期的常规探空数据,对风廓线雷达探测数据的可靠性和探测能力给予了评估。结果表明,受乌鲁木齐四季不同的气候背景影响,风廓线雷达的数据获取率在夏季最高,在冬季最低,80%的数据获取率等值线在夏季、冬季各自达到的高度分别为4500 m和1980 m;240 m以下风廓线雷达探测的风速误差较大,240 m以上风廓线雷达四季探测的风速普遍小于实况,误差在-1~0 m/s之间的出现频率最高,介于28.8%~31.8%,且最大频率在四季出现的高度有所差异,总体来看夏季风速误差相对较小;风向误差总体在-22.5°~0°之间的出现频率最高,且随着高度增加频率增加;风廓线雷达对风速的探测能力优于风向,二者与实况的相关系数各自为0.9左右和0.6~0.8;通过对长时间序列的风速、风向资料的比较,说明风廓线雷达能够较为准确地反映冬季天气过程的演变,且能够较为精细地刻画夏季短时强降水天气过程中高低空气流的变化特点。在综合考虑低空地物回波、探测盲区因素以及高空气球探空飘移等多种因素影响的情况下,可见风廓线雷达对乌鲁木齐大气环境和天气过程拥有较可靠的监测能力。     

边界层风场对深圳秋冬季灰霾天气的影响

为研究边界层风场对深圳秋冬季灰霾天气的影响,统计分析2011—2014年秋冬季深圳石岩边界层风廓线雷达各层风向风速数据和深圳国家基本气象站数据,结果表明:(1)秋冬季节边界层(1 500 m以下)风力越小灰霾出现的概率越大。(2)秋冬季400~1 500 m层风速与灰霾天气关系最密切,有霾时该层平均风速在4 m·s-1左右;无霾时平均风速明显加大到6 m·s-1。(3)秋冬季边界层为较弱的偏北方向风时易导致灰霾天气,而较强的偏南方向风有利于霾的消散。     

风廓线雷达与L波段探空雷达测风资料的对比

为了探讨风廓线雷达资料的可用性,对2013年9月—2015年10月青岛站和济南站的风廓线雷达与L波段探空雷达测风数据进行相关、误差及有效样本比率分析。结果表明:(1)济南站和青岛站绝大多数高度层00:00和12:00风廓线雷达与L波段探空雷达的水平风速显著正相关,通过α=0.05及以上信度检验;(2)济南站00:00和12:00,晴天1.5 km以上及雨天0.64 km以上大多高度层风廓线雷达的水平风速比L波段探空雷达偏小约2 m·s~(-1),且当风廓线雷达与L波段探空雷达水平风向差≤20°时,有效样本比率基本在70%以上,资料质量很高;(3)青岛站00:00和12:00,6.48 km以下大多高度层风廓线雷达探测的水平风速比L波段探空雷达偏小2~4 m·s~(-1),水平风速资料可用,但当2部雷达风向差≤20°时,有效样本比率仅为20%,海陆风及2种仪器的布设距离是水平风向差异的主要原因。     

浙江北部近海边界层风廓线特征分析

利用2010年12月至2014年5月宁波近海凉帽山370m高塔气象梯度风观测和浙江北部沿海自动气象站测风资料,对浙江北部近海风速垂直廓线进行分析,结果发现:受地形影响,偏南、偏北风时塔基风速一般比上一层风速大。不同天气系统影响下近地边界层风廓线不同,南风型320m以下风速基本遵从对数律。热带气旋影响型和北风型时风廓线可分为3段,常通量层内基本满足对数律,该层向上一段高度热带气旋影响型风速变化不大,北风型反而减小,再往上风速又继续增大。北风型风廓线的这种3段结构表现比热带气旋影响型更为清楚,约80~109m风速出现相对极大值,200~250m间存在风速极小值。满足对数律的近地边界层内小风比大风具有更好的拟合优度。浙江北部沿海自动气象站测风资料不同风型统计分析与高塔风廓线表现基本一致。     

渤海西岸空气动力学粗糙度特征分析

利用2009年12月至2010年11月渤海西岸大港风能塔观测得到的风速、风向和温度梯度资料,计算了风能塔周围空气动力学粗糙度Z0。对比分析了风廓线法和风速标准差法的计算结果,讨论了风速标准差法的适用性以及下垫面空间非均一性对粗糙度的影响。结果表明：风能塔三个主风向上的平均粗糙长度为：0.1319m(N),0.0386m(SE)和0.0182m(SW)。通过严格条件限制,利用风速标准差法可以得到与风廓线法相同的计算效果。同一方位上,利用10-30 m资料计算得到的粗糙度长度的季节差异相对较小,而50-70 m的计算结果差异相对较大。在相同高度上,粗糙度长度计算结果亦存在明显季节差异,反映了随季节变化的植被对地表粗糙度的影响。     

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.