地形对安阳天气变化的影响

安阳位于太行山东侧,受太行山影响,西路冷空气影响时不易产生降水,东路冷空气由于受地形抬升影响,常产生降水。由于下沉增温作用,西路冷空气影响时降温不明显;由于太行山的阻挡作用,东路冷空气影响时,降温持续,如有降雪,则会出现连续低温天气。此外,安阳东、西风较少,偏南风最多,偏北风次之。     

一次东北冷涡暴雨过程的数值模拟试验

利用MM5非静力模式成功地模拟了1998年8月8－9日一次东北冷涡切变型暴雨过程。发现本次过程中，低涡西北象限的强降水中心的产生是由于高层形成的强辐散，切变降水的产生由于偏南急流与偏东急流的交汇，切变带上升运动层明显低于低涡。同时，通过对比试验发现，偏南急流是本次过程主要水汽输送带。且对切变降水影响较大。偏南急流区水汽的减弱对系统（低涡、切变）的降水强弱有直接影响；西路冷空气加强主要使大气斜压作用增强导致低涡强度及降水增强；东路冷空气主要通过阻挡偏南气流形成抬升从而主要影响切变强度和降水。阻高则通过对上游低值系统的阻挡影响其位置和强度进而影响过程降水。     

一次晚春降水相态变化特征及成因

应用常规观测资料、自动站资料、雷达资料及1°×1°NCEP再分析资料,对2013年4月19日河北省一次晚春回流降水相态变化特征及成因进行了分析。结果表明:河北中南部地区相继受东西2股冷空气影响,前期东路冷空气从850 hPa以下入侵,之后西路冷空气随700 hPa高空槽东移加剧了中南部地区的降温,使大范围降水出现相态变化;地面温度对本次降水过程的雨雪相变指示性不大,但地面气压的变化早于地面温度,对预报具有一定的指示意义;700 hPa低空急流对中空暖层的形成起决定作用,当暖层消失,降水相态完全转为降雪,925 hPa上-2℃温度特征线与降雪区对应较好,通过温度的垂直结构来辨别相态更为可靠;雷达回波的0℃层亮带出现高度在4.7 km左右,其高度的快速降低与降水相态转变时间一致。     

关中初夏一次连阴雨过程的天气学特征分析

对2007—06—16—22陕西关中连阴雨天气过程的天气动力学分析,认为：500hPa乌拉尔山稳定的长波脊和东北到鄂霍茨克附近的长波脊、贝湖低槽和高原上低值系统的维持是造成陕西连阴雨的主要天气系统;中低层青藏高原东南侧到河套有西南气流发展并维持,为阴雨天气提供充沛的水汽和能量;700hPa切变线是连阴雨期间降水形成的动力和辐合机制;当关中处于高能舌和湿舌区时,降水明显;地面上四川到陕西有倒槽生成时,对应的降水强度大。当东路冷空气减弱消失只有西路冷空气影响时,相应的降水也减小。     

河西走廊中西部干旱区极端暴雨个例分析

利用常规、自动气象观测站资料、卫星资料及NCEP 1°×1°再分析资料,对2012年6月4 5日河西走廊中西部干旱区极端暴雨天气过程的影响系统配置、中尺度特征、水汽输送、不稳定能量等方面进行了诊断分析。结果表明:此次暴雨发生在地面冷锋过境后,降温冷凝作用明显,对流层高层存在强抽吸作用,中层高原低涡受其下游弱脊阻挡较长时间维持在暴雨区上空,低层存在切变线,高低空系统的耦合提供了中尺度对流系统发生、发展的有利条件;水汽主要来自对流层中低层东、西两路及高层南路三支水汽输送通道,西路水汽输送强度最大,东路水汽输送受小高压影响显著,暴雨开始后6 h才完整建立,暴雨中心整层大气可降水量达到了该地区夏季平均值的两倍多;通过降温、增湿作用近地面出现对流不稳定能量,自由对流高度较低;涡旋云系的冷空气侵入处,不断激发出6个β中尺度的对流单体,暴雨中心玉门两次受其中4个单体的影响,产生短时强降水。     

北京一次冬季极端降水过程中相态转换预报的误差分析

应用多种常规和非常规观测气象资料以及再分析资料对2020年2月13日夜间至14日白天北京地区一次极端雨雪过程的成因进行了分析,并重点探讨了模式降水相态预报的误差及其原因。结果表明:（1）本次降水过程中,低涡系统深厚,强度异常强,移速慢,影响时间长,导致北京地区部分站点降水持续12 h左右。异常偏强的东南风急流向北京西部山前输送水汽,配合与急流相伴的较强低空风切变形成的对称不稳定,产生高降水率的斜升对流降水。较长的降水时间以及冬季夜间罕见的高降水率共同造成了此次极端日降水。（2）北京凌晨0℃层高度和地面气温下降缓慢,北京西部处于两股冷空气间的暖舌中,冷空气从东路入侵造成北京东部降温时间较西部早,且降温辐度较大,导致0℃层高度呈西高东低形势,故转雪时间东部早于西部。（3）模式预报的东路冷空气较观测偏强偏早,降水的对流性也显著弱于观测,导致其预报的凌晨地面气温较观测低,0℃层高度下降过快,从而过早预报转雪时间,高估了降雪量和积雪深度,利用非常规温度观测对模式温度廓线预报误差进行检验,可为订正模式相态转化时间预报偏差提供依据。      

华北一次冷空气回流路径对降水相态的影响分析

针对2018年4月3-5日东北冷空气回流到京津冀地区造成复杂相态降水过程典型华北回流天气个例，利用ERA5再分析资料和MICAPS地面资料，详细分析了冷空气路径、形态、对降水范围及相态的影响等。分析表明：回流冷空气对京津冀地区的影响，可分为4个阶段，即低层冷舌侵入、沿山堆积扩散、增强维持、变性消散阶段。在低层冷舌侵入阶段，冷空气以冷舌形式经东北、渤海侵入京津冀地区，冷舌在不同高度位置不同；冷舌在垂直方向位于干、湿过渡区，降水粒子经冷舌下方干区蒸发，造成阴天无降水天气。在沿山堆积扩散阶段，低层冷空气遇太行山堆积并向南北以扇形形式扩散，较高层次冷空气西边界扩散至太行山山区；燕山南部、太行山东部存在深厚湿层，且温度较低，出现降雪；距离山脉较近的平原地区出现雨夹雪或雪；距离山脉较远的平原地区无降水。在增强维持阶段，冷空气强度达到最强，范围达到最大；深厚湿层从太行山、燕山向平原扩展，降水范围扩大，降水相态主要取决于近地面温度。在冷空气变性消散阶段，较高层次回暖先于较低层次，冷空气变性消失，降水趋于结束。     

“2003．3．4”强寒潮天气过程分析

从环流背景、冷空气、低空急流和数值预报应用等方面对四川盆地2003年3月上旬发生的一次强降温天气过程进行了分析，探讨了降水对降温的影响。从中得出强降温的发生不仅与冷空气的强度有关，而且低空急流的存在对降温的幅度也起着十分重要的作用。并且指出，在数值预报中低层为负变高的情况下。对冷空气入侵而带来的增压作用应该有个新的认识。     

1991～2004年不同环流背景下南宁市降水化学成分变化特征的研究

利用1991～2004年广西南宁市降水化学成分资料，结合NCEP／NCAR再分析资料，分析了不同大气环流背景下南宁市降水化学成分的变化特征。结果表明，南宁市的酸雨属硫酸型，酸雨的形成与大气环流密切相关，影响南宁市酸雨的大气环流主要是高空槽锋面，其次是高压后部和热带气旋，受高空槽锋面特别是东路冷空气影响时，出现酸雨的频率最高，pH值最小，雨水中SO4^2-明显增多，热带气旋降水时，雨水酸度最轻，离子浓度甚至比高空槽锋面影响低2～3倍。     

一次强降温过程中温度与降水分布及成因分析

2011年3月13-15日,冷空气入侵重庆地区引起了一次区域性强降温天气.过程显著降温区域位于重庆中西部地区,而大降水区域位于重庆中东部地区.分析表明,这种降温降雨分布特征的形成,主要是由于冷空气侵入四川盆地的路径结合地形引起的.高空横槽转竖引导槽后冷空气向南爆发,冷空气南下至河套地区后,在地形的作用下,分西北和东北两条路径侵入四川盆地,其中西北路径为主要路径,由西北路径进入盆地的冷空气,结合重庆的特殊地形,引起了盆地内重庆中西部地区的显著降温;两条路径中的冷空气在川东地区相遇后有弱锢囚锋生成,锢囚锋出现的时间与位置与大降水出现的时间与落区基本一致,诊断分析显示,锢囚锋所在区域对应着较强上升运动区和水汽辐合的大值区.锢囚锋可能是重庆中东部地区大降水产生的主要原因.     

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.