北上台风暴雨过程涡散场的能量收支和转换特征

利用辐散风和旋转风的动能收支方程,对北方一次北上台风倒槽暴雨过程暴雨区内的涡散场能量收支和转换进行了计算.结果表明:暴雨区内动能的增加是暴雨增幅的一个主要原因.暴雨发展时,就旋转风动能(K_R)而言,旋转风动能通量(HFR)辐合是主要能源,而旋转风的动能产生项(GR)是主要能汇;就辐散风动能(K_D)而言,辐散风的动能产生项(GD)是主要能源,辐散风动能通量(HFD)辐散是主要能汇;总动能水平通量(HF)提供的辐合主要表现于对流层中、低层,这就使得低层辐合加强,上升运动加强,有利于暴雨的增幅.在暴雨过程中次网格尺度效应由能源转变为能汇,在暴雨发展之时能汇减小;能量的转换项C(K_D,K_R)总为正值,在转换项中,地转效应项的贡献很大.说明暴雨过程能量均由K_D向K_R转换,也就是说有效位能经K_D向K_R转换,充分说明了在整个暴雨过程中,尽管辐散风动能变化(∂K_D/∂t)很小,但是它在其中充当“桥梁”作用,C(K_D,K_R)在暴雨发展时达到最大,此时能量转换最为旺盛;对流层低层辐散风动能向旋转风动能的转换是暴雨产生和发展的重要条件.此次暴雨过程,在暴雨区内表现为斜压不稳定和正压稳定共存的特征,其发展过程是系统斜压不稳定增长,正压稳定性减弱的过程,暴雨增幅的另一个重要原因就是暴雨区内低层斜压的发展.     

台风区和外围暴雨区的旋转风、散度风动能收支

用完全的散度风(v_D)和旋转风(v_R)动能收支方程对8116台风和8407台风以及8116台风与其外围暴雨区的关系作了讨论。结果表明:台风区的有效位能通过散度风动能(K_D)转换为旋转风动能(K_R).台风向区域外部输出动能,在暴雨区上空通过涡度、散度场相互作用的转换机制由K_R向K_D转换,散度风加大触发对流发展产生暴雨,这可能是台风与其外围暴雨联系的一种能量过程。     

京津冀地区GNSS ZTD时序分析及对厄尔尼诺事件的响应

京津冀地区夏季暴雨频发,水汽是影响暴雨形成的关键要素之一.本文利用中国大陆构造环境监测网络（CMONOC）京津冀地区GNSS（全球导航卫星系统）观测资料,开展GNSS天顶对流层总延迟（ZTD）时序分析及对厄尔尼诺事件的响应研究.利用快速傅里叶变换与小波变换方法从频域和时域开展GNSS ZTD时序分析,并对GNSS ZTD不同周期时序与东部型指数（I_EP）、中部型指数（I_CP）进行比较,分析I_EP、I_CP对GNSS ZTD周期变化的影响.研究发现：GNSS ZTD异常时段与厄尔尼诺事件存在对应关系.东部型指数（I_EP）与GNSS ZTD呈正相关;中部型指数（I_CP）与GNSS ZTD呈显著负相关.在东部型厄尔尼诺事件的影响下,GNSS ZTD的季节性周期增大,月周期和半月周期减小;在中部型厄尔尼诺事件的影响下,GNSS ZTD的季节性周期、月周期、半月周期都减小.研究结果可为掌握区域GNSS ZTD预测变化规律提供参考,并为利用水汽感知厄尔尼诺事件提供可行性基础.     

锋生切变型强对流概念模型在浙江中西部“3·21”过程中的应用探究

利用ECMWF 0.25°×0.25°再分析资料,对照浙中西的强对流概念模型,对2019年3月21日发生在浙江中西部地区(简称"浙中西")的一次雷暴大风为主的强对流过程(简称"3·21"过程)进行诊断分析、经验总结。结果表明:该过程符合浙中西锋生切变型的强对流概念模型,出现该过程的环境条件是700 hPa西南急流脉动、850 hPa偏北和偏南两支气流强烈发展、地面低压倒槽和低层湿舌增强;探空曲线表现为上干下湿,对流层中层有明显的干侵入,大风指数I_w、对流有效位能 (Convective Available Potential Energy, CAPE)和500 hPa以下垂直风切变异常偏强形成动力强迫;对比不同强对流天气有不同的预报着眼点,设定阈值或可提高预报警报效率,如雷暴大风天气大风指数I_w > 18.5 m·s^-1、CAPE> 1 700 J·kg^-1、500 hPa的相对湿度小于46 %,冰雹天气则0 ℃层、-20 ℃层高度低于4.6 km和7.6 km且850 hPa与500 hPa气层温差高于26 ℃等,深刻理解该类强对流概念模型,是做好此类致灾性强对流潜势预报的关键点。     

CRA40在中国地区GNSS水汽反演中的适用性评估与分析

基于中国气象局发布的CRA40气象再分析资料,计算地基GNSS水汽反演中涉及气压、气温、大气水汽加权平均温度（T_m）、天顶对流层总延迟（ZTD）等关键参数,并分别以地面气象站（气压、气温）、无线电探空测站（T_m）以及地基GNSS测站（ZTD）为参考,对这些参数在中国地区的精度和可靠性开展了系统的评估.计算结果与欧洲中期天气预报中心（ECWMF）最新一代ERA5产品的计算结果进行比较,结果表明：基于CRA40计算的测站处气压和ZTD的平均RMS（均方根）分别为0.91 hPa和13.5 mm,略差于ERA5;计算的测站处气温和T_m平均RMS分别为2.67 K和1.47 K,略优于ERA5.三类参数（气压、气温、ZTD）的日变化总体趋势与实际观测符合较好.     

冬季东亚大槽强度年际变化及其与中国气候联系的再分析

利用NCEP/NCAR再分析资料以及国家气象局整编的中国160站逐月降水和气温资料,定义了一个北半球冬季500hPa东亚大槽强度指数(I_EAT),并分析了该指数所反映的冬季东亚大槽强度的年际变化规律及其与同期中国冬季降水、气温的关系.结果表明:I_EAT指数反映了对流层中层冬季亚洲大陆高压脊与西北太平洋上空的低压槽系统之间的平均经向风强度,且能够较好地反映冬季东亚大槽的强度.东亚大槽的强度在20世纪80年代之前相对较弱,并存在2-3年和准4年的年际变化周期.冬季东亚大槽强弱变化可能与源自地中海地区的罗斯贝波动能量沿亚洲急流东传有关,且这种西风带中的扰动具有准正压结构.I_EAT指数与青藏高原东部地区的冬季降水和气温相关显着.当I_EAT指数为正(负),东亚大槽偏强(弱),对应着中国华中地区以及华东大部分地区冬季总降水量偏少(多),且华中地区冬季平均气温偏高(低).进一步研究发现,在东亚大槽偏强年,华中地区冬季平均气温异常升高主要是由于异常非绝热加热和下沉运动导致的异常动力增温所致.这些研究结果有助于更好地理解由于东亚大槽强度的变化而导致的中国冬季气候变化特征及其原因.     

FEATURES OF ENERGY BUDGET AND CONVERSION OF DEVELOPED AND UNDEVELOPED TROPICAL CYCLONE

With two cases of local tropical disturbances in both developed and undeveloped phases, contributions to the genesis and development by kinetic formation and transfer from divergent and nondivergent winds are studied using energy budget equations. Computations are done of conversion kinetic energy between the two types of winds. The result indicates that the subgrid scale effect is the principal source of kinetic energy for a tropical cyclone to grow into a typhoon; the cumulus convection plays a dominant role, in company of relatively weaker contributions on vdrious phases of the life cycle by convergence of fluxes of divergent and nondivergent winds as well as the formation of kinetic energy by the former wind. It is also suggested that the conversion of kinetic energy between the divergent and nondivergent winds C(K_x, K_ψ)is increasing with the development of disturbance mainly due to the contribution by C₁=f^▽Χ^▽ψ. The disturbance is shown in the distribution of C(K_x, K_ψ) to increase in a favorable anticyclonic outflow corresponding to the upper level where the conversion becomes negative in developing and mature phases while the wind velocity increases with enhanced conversion fr0m K_x to K_ψ the lower level in association with the growth of the disturbance. In addition,geopotential energy P converts to kinetic energy of the divergent wind in every stage from formation to mature of the disturbance by means of C(P, K_x), the maximum appearing on the middle and upper layers of the troposphere.The intensity of C(P, K_x) is consistently in phase with variation of C(K_x, K_ψ).     

ECAP等环境参数在强对流天气分析中的应用

引入大气热力学变量密度温度T_ρ,采取与实际大气较为相符的可逆饱和湿绝热抬升过程,利用MM5V3.5模式输出资料,计算了对流有效位能E_CAP。在此基础上,介绍了能量螺旋度指数I_EH。分析了2003年7月江淮梅雨暴雨等强对流天气发生过程中对流有效位能E_CAP及能量螺旋度指数I_EH的量值变化。结果表明:E_CAP、I_EH等参数对强风暴的发生发展有一定的指示作用,值得在业务工作中推广应用。     

55年呼和浩特气候变化及成因分析

用计算多年滑动平均值、距平百分率、洪涝指数(I_f)、干旱指数(I_d）、降水间隔平均差(S)的方法,对呼和浩特地区1951—2005年汛期（6—8月〉的旱涝等级、多雨期和少雨期进行分析，研究55年汛期旱涝变化特征和年际特点。分析结果表明：(1)该地区汛期旱涝有大致以3?5年的周期交替出现，具有较明显的年代际特征。（2)55年中连续干旱和连续雨涝的年数基本平衡，但发生连续干旱的程度要高于连续雨涝；通过相关分析得知：北半球500hPa高度场、副高、SSTA与本区汛期降水相关密切，是形成汛期旱涝变化的重要因素,可作为该地区汛期降水领测的指示因子。     

苏南两次回流天气过程形势特征和降水相态分析

利用常规观测资料、0.25°×0.25° FNL资料、微波辐射计资料和风廓线雷达资料，对发生在苏南的两次回流天气过程的环流特征、大气层结特征等进行分析。结果表明：高纬度地区500 hPa是两槽一脊的环流形势，近地面层持续受东北风影响，西南暖湿气流在底层冷垫上爬升，是回流降雪天气形势；从东北平原回流南下的冷空气湿度小，在降水中只起到了"冷垫"的作用。中低层西南暖湿气流差异导致两次降雪强度存在差异；近地面层的降温在雨和雪的区分判别上影响更大，统计2012—2022年初苏南地区8个降雪个例发现，苏南地区，满足T₈₅₀≤-4 ℃，T₉₂₅≤-3 ℃，T_{1 000}≤1 ℃，T_{2 m}≤2 ℃这样的温度阈值条件时开始雨转降雪；当1 515 gpm≤H_700-850≤1 575 gpm，1 289 gpm≤H_{850-1 000}≤1 317 gpm时，相态易由雨转雪。中低层西南气流、底层东北风的加强，2 000 m左右高度风场的转变，短波槽（或切变线）触发了不稳定能量的释放，导致降雪发生；当中低层西南气流减弱转为西北气流后，大气水汽含量降低，降雪结束。     

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.     

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.     

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.     

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.