GPM卫星降水产品在台风极端降水过程的误差评估

以雨量站观测数据为基准,利用相关系数(CC)、相对偏差(RB)、均方根误差(RMSE)以及分级评分指标(探测率POD、误报率FAR、临界成功指数CSI),对全球降水计划GPM多卫星融合产品4. 4版本准实时产品IMERG_ER(简称IMERG)在2017年接连登陆广东的3个台风"天鸽"、"帕卡"和"玛娃"极端降水过程性能进行评估。广东省内"天鸽"、"帕卡"和"玛娃"的CC分别为0. 80,0. 68和0. 47,RB为-12. 00%,-47. 06%和-29. 10%,RMSE达33. 00,40. 03和26. 40 mm。雨区的CC分别为0. 59,0. 48和0. 33,RB为2. 21%,-43. 58%和-25. 94%,RMSE为44. 34,51. 04和40. 64 mm。IM ERG低估了"天鸽"、"帕卡"、"玛娃"的总体降水强度,主要源自于对雨区的低估。从散点分布来看,IMERG高估了强降水,低估了弱降水的强度,对极端强降水的估测能力存在较大的不稳定性。降水量时序变化特征表明,IMERG较好体现了降水峰值和谷值的数量及变化趋势,但时间和强度有偏差。误差来源于复杂地形、PMW观测时间分辨率不足和IR反演降水准确度不足对卫星估测降水的影响。分级检验结果显示,相同量级内,雨区的POD更大,FAR更小,CSI评分更高,IMERG对雨区的反演能力更强。IMERG对"天鸽"估测效果最好,POD较高,FAR较小,CSI较高;"帕卡"POD较低,暴雨及以上的FAR较高,CSI下降显著;"玛娃"POD比"帕卡"高,但FAR也高,CSI中等。可见IMERG对小量级降水具有较好的估测能力,强降水估测显著偏高,暴雨及以上的降水误差起了主要贡献。     

GPM卫星和地面雷达对江苏盐城龙卷风强降水估测的对比

为综合评估卫星和天气雷达在2016年6月23日盐城龙卷风期间的强降水过程的降水估测精度,以国家级雨量站观测数据为基准,结合相关系数(CC)、相对误差(RB)、均方根误差(RMSE)以及分级评分指标,利用S波段的天气雷达定量降雨估测产品(RQPE)和全球降水观测计划多卫星融合产品(IMERG_FRCal,IMERG_FRUncal,IMERG_ERCal)进行比较。结果表明,雷达和卫星的累积降水量与雨量站的空间相关性很强(相关系数大于0.9),基本上能捕捉到整个降水过程的空间分布。降水主要分布在江苏省北部,但卫星高估了江苏省东北部强降水中心的降水量;对于小时时序区域平均降水,卫星高估了降水,而雷达低估了累积降水量。综合降水中心区域分析,IMERG的强降水区域降水量与雨量站的时间序列的偏差显著;RQPE在降水峰值达到之前及峰值之后与地面雨量站的变化趋势基本一致,但对降雨量峰值有明显的偏低。RQPE能较为准确地在时间上捕捉到降雨强度的变化趋势,但对于大雨及暴雨的估测能力不佳;RQPE的POD、SCI值都远远高于IMERG, FAR也较小。IMERG几乎未能监测到强降水的发生。总体上,RQPE对此次龙卷风强降水量的估测表现优于3种IMERG产品,特别是在捕捉强降水区域的空间分布方面,但对于强降水的估测能力仍需进一步改善。     

基于CINRAD SA双偏振雷达新型定量降水估测方法研究

杭州下沙S波段天气雷达在双偏振升级的基础上增加了精细化探测技术，为了进一步提高雷达定量降水估测精度，本文参考小时雨量计订正雷达估测降水算法模型，建立了一种基于分钟级雨量计数据的实时定量降雨估测雨强订正方法（简称QPE ADJUST法），利用雨量计资料对雷达的QPE数据逐体扫实时订正，累计完成1 h、3 h降水估测产品，提高了雷达降水估测精度。通过对雷达产品及自动站数据资料的评估，分别从降水估测算法、雷达分辨率影响及体扫周期速度影响3方面对QPE ADJUST法的估测降水效果进行了统计分析。结果表明：QPE ADJUST法在雷达高分辨率、快体扫周期的情况下均比其他算法更好地表现出降水时空分布特征，并将雷达小时定量降水估测的误差从50%降低至20%左右，有很高的估测精度和稳定性，具有业务应用价值。     

基于雷达—雨量计降水融合方法提高极端降水监测能力

高时空分辨率、高精度的降水产品对于极端降水的监测以及防灾减灾具有重要意义。地面雨量计提供点尺度降水精确观测,但无法精细化捕捉对流性强降水的空间分布。雷达观测可以精细地刻画降水的空间分布特征,但雷达定量估计降水（QPE,quantitative precipitation estimation）产品估测精度易受雷达观测偏差和Z–R（雷达反射率—降水率）关系等因素影响。因此,本文开展高时空分辨率的雷达—雨量计降水融合算法研究,集成雨量计观测和雷达定量估计降水产品各自的优点。该算法主要步骤包括:雨量站观测数据格点化、局地雨量计订正雷达QPE和雷达—雨量计降水融合三个部分。首先利用克里金插值方法,对雨量站观测的降水进行插值,得到格点降水信息;再通过局地雨量计订正方法系统性地订正雷达QPE产品,以提高雷达QPE产品精度;最后,结合降水类型,通过雷达—雨量计降水融合算法,产生高时空分辨率、高精度的雷达—雨量计降水融合产品。通过郑州“21·7”暴雨、台风“烟花”和2021年8月随州暴雨三个典型的极端降水个例,对雷达—雨量计降水融合算法产生的雷达—雨量计降水融合产品进行了系统地评估和分析。结果表明,在不同的极端降水个例和不同的降水时段,雷达—雨量计降水融合产品精度上优于雷达QPE产品,且在降水的空间分布上较雨量站观测格点插值产品更能精细地刻画降水的结构特征。表明算法得到的雷达—雨量计降水融合产品的准确性较高,对极端降水有较好地捕捉和监测能力。     

X波段双偏振雷达对造成北京门头沟泥石流的强降水观测分析

利用房山X波段双偏振雷达观测资料,分析2017年6月18日北京门头沟泥石流的强降水过程,重点研究了泥石流发生地上空10 km×10 km区域内雷达反射率因子时空变化特征,并结合雷达定量降水估测(Quantitative Precipitation Estimation, QPE)讨论该类雷达探测设备在复杂地形区域的适用性。结果表明,在山区常规自动气象站布网稀疏的条件下,X波段双偏振雷达能够有效捕捉此次强降水的发生发展过程,同时,雷达定量降水估测得到的高分辨率降水场可以把握山区强降水中心,进而弥补山区雨量站匮乏的不足。此次过程中影响泥石流事件发生的降水时间发生在6月18日12—16时,其中,15时事发区域小时QPE最大值达到53.9 mm·h^-1,上游来水和局地突发性强降水共同作用是本次泥石流事件的主要成因。     

SWAN系统中QPE产品的应用评估

“灾害天气短时临近预报系统”(SWAN)在我国气象预报业务中已得到广泛应用。文章介绍其中雷达定量降水估算QPE算法 (RASIM方法)的技术与特点,选取湖北省6部S波段多普勒天气雷达在2012年探测的暴雨天气过程资料,系统性评估了SWAN系统中QPE产品实用性,初步分析了产生估算误差的原因。评估表明：整体而言该方法在湖北省使用效果较好,平均绝对误差率小于30%;探测距离的增加对S波段雷达QPE精度影响不大;各雷达对30 mm以上降水的估算平均绝对误差率较小,但估算结果较实况偏弱,随着雨量（雨强）增大,低估的比例也增大。就单部雷达而言,宜昌雷达估算降水误差最大,武汉雷达受附近建筑遮挡影响次之,恩施雷达估算降水误差最小。     

多卫星融合降水产品对2015—2020年登陆浙江台风降水的监测能力评估

基于浙江省雨量站观测数据,利用相对偏差(RB)、均方根误差(RMSE)、相关系数(CC)对2015—2020年登陆浙江的“灿鸿”“摩羯”“利奇马”“米娜”和“黑格比”影响期间全球降水观测计划GPM多卫星融合产品V06B版的准实时降水产品IMERG＿ER(简称IMERG)进行总体评估,并采用探测率(POD)、空报率(FAR)和临界成功指数(CSI)来评估不同降水量级下IMERG的降水估测能力。结果表明：IMERG总体能较好反映降水的空间分布特征,但对强降水落区范围大小的捕捉能力尚有一定不足。IMERG对“灿鸿”过程总降水量具有一定程度的低估,对“摩羯”“利奇马”“米娜”和“黑格比”过程总降水量存在高估。此外,IMERG对“黑格比”降水变化的捕捉能力最强,接着依次是“灿鸿”“摩羯”和“利奇马”,较差的是“米娜”。从分级检验结果看,随着降水量级的增加,POD和CSI稳中有降,FAR稳中有升,即IMERG对小雨的辨识能力最优,对大暴雨的捕捉能力较差,同时高估了较强降水发生的可能性。客观上看,IMERG对个别台风降水强度的捕捉能力稍显不足,定量误差较大,但总体上追踪台风降水动态变化的能力尚可,具...     

卫星降水产品在太行山区的适用性初步评估

以地面雨量站的观测数据作为基准,采用连续统计指标(相关系数R、均方根误差RMSE、偏差率β、变化率γ、综合评价指标KGE')以及分类统计指标(命中率POD、误报率FAR、临界成功指数CSI),在不同时间尺度(1,3,6,12和24 h),基于不同降水强度(小雨、中雨、大雨、暴雨、大暴雨)范围,综合评价了3种卫星降水产品(CMORPH CRT,TMPA TRMM 3B42和GPM IMERG)在太行山区的适用性。结果表明:在精度表现上,当降水累积到3 h之后,各产品的精度表现逐渐平稳,KGE'值基本保持不变,但总体精度较低。在降水探测表现上,3种产品的POD随时间积累而升高,波动范围在0. 5～0. 8,CRT和3B42产品的FAR随时间的累积而下降,波动范围在0. 5～0. 75。在不同降水强度范围的进行精度分析,发现卫星观测降水和地面实际降水呈弱相关(R0. 4),RMSE随雨强的增大而增大,POD随雨强的增大而减少,范围大致在0. 4～0. 65,FAR随雨强的增大而升高,范围大致在0. 6～0. 85。IMERG产品在各时间尺度下都低估了0. 1 mm降水事件,而对降水≥0. 1 mm事件的观测则不同程度地偏高。CRT产品在1,3,6和24 h时间尺度上的大雨和暴雨事件存在高估现象,3B42产品在不同时间尺度上都更为接近实际降水情况。     

SWAN中定量降水估测和预报产品的检验与误差分析

采用2010—2011年5—9月河南省区域加密自动站雨量和全省6部新一代天气雷达资料,用点对点统计检验评分方法,分析SWAN系统中定量降水估测(QPE)和定量降水预报(QPF)产品在河南省短时强降水过程中的误差分布,并分别讨论二者在河南省区域与局地强降水过程中的差别及产生误差的直观原因。结果表明:1)SWAN中QPE和QPF均对小时雨量低于10 mm的降水有较好的估测和预报能力;QPE以豫西南和豫北效果最好,QPF在豫中地区预报能力更强。QPE估测较实况偏大;QPF对小时雨量低于20 mm的短时强降水预报略偏大,而对更强降水预报偏小,尤以豫西和豫南最明显。2)QPE和QPF均对区域性降水有更好的估测或预报能力。3)区域降水过程中,QPE对降水中心范围和位置估测较准确,估测值较实况偏大;QPF对强降水中心位置预报略有偏差,其中心强度较实况偏弱。     

深度学习模型在2021年汛期武汉市雷达回波临近预报中的应用评估

近年来，人工智能技术在图像识别领域取得了突破性进展，为探寻人工智能模型在武汉地区雷达回波临近预报中的应用价值，本文利用湖北武汉市2015—2020年雷达回波和降水量观测资料，对PredRNN++、MIM、CrevNet和PhyDNet 4种深度学习模型进行雷达回波临近预报训练，并基于2021年汛期雷达回波资料进行雷达回波临近预报。在此基础上，通过降水强度和降水面积指数筛选降水过程，并以均方误差（Mean Square Error, MSE）、结构相似性指数（Structural Similarity Index Measurement, SSIM）、命中率（Probability of Detection, POD）、空报率（False Alarm Rate, FAR）和临界成功指数（Critical Success Index, CSI）为指标，检验评估上述4种深度学习模型和光流法对2021年汛期武汉地区雷达回波的临近预报性能。结果表明：（1）整体来看，MIM模型的MSE最小、POD最高，MIM和PredRNN++模型的SSIM并列最高；所有深度学习模型的FAR均低于光流法，且Phy...     

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.     

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.     

IMPACT OF ATMOSPHERIC LOW-FREQUENCY OSCILLATION ON THE IMMIGRATION OF NILAPARVATA LUGENS(STL) IN HUNAN AND JIANGXI PROVINCES

Various features of the atmospheric environment affect the number of migratory insects, besides their initial population. However, little is known about the impact of atmospheric low-frequency oscillation(10 to 90 days) on insect migration. A case study was conducted to ascertain the influence of low-frequency atmospheric oscillation on the immigration of brown planthopper, Nilaparvata lugens(Stl), in Hunan and Jiangxi provinces. The results showed the following:(1) The number of immigrating N. lugens from April to June of 2007 through 2016 mainly exhibited a periodic oscillation of 10 to 20 days.(2) The 10-20 d low-frequency number of immigrating N. lugens was significantly correlated with a low-frequency wind field and a geopotential height field at 850 h Pa.(3) During the peak phase of immigration, southwest or south winds served as a driving force and carried N. lugens populations northward, and when in the back of the trough and the front of the ridge, the downward airflow created a favorable condition for N. lugens to land in the study area. In conclusion, the northward migration of N. lugens was influenced by a low-frequency atmospheric circulation based on the analysis of dynamics. This study was the first research connecting atmospheric low-frequency oscillation to insect migration.     

A COMPARATIVE ANALYSIS OF ATMOSPHERIC AND OCEANIC CONDITIONS BEFORE THE OCCURRENCE OF TWO TYPES OF EL NIO EVENTS

The atmospheric and oceanic conditions before the onset of EP El Ni?o and CP El Ni?o in nearly 30 years are compared and analyzed by using 850 hPa wind, 20℃ isotherm depth, sea surface temperature and the Wheeler and Hendon index. The results are as follows: In the western equatorial Pacific, the occurrence of the anomalously strong westerly winds of the EP El Ni?o is earlier than that of the CP El Ni?o. Its intensity is far stronger than that of the CP El Ni?o. Two months before the El Ni?o, the anomaly westerly winds of the EP El Ni?o have extended to the eastern Pacific region, while the westerly wind anomaly of the CP El Ni?o can only extend to the west of the dateline three months before the El Ni?o and later stay there. Unlike the EP El Ni?o, the CP El Ni?o is always associated with easterly wind anomaly in the eastern equatorial Pacific before its onset. The thermocline depth anomaly of the EP El Ni?o can significantly move eastward and deepen. In addition, we also find that the evolution of thermocline is ahead of the development of the sea surface temperature for the EP El Ni?o. The strong MJO activity of the EP El Ni?o in the western and central Pacific is earlier than that of the CP El Ni?o. Measured by the standard deviation of the zonal wind square, the intensity of MJO activity of the EP El Ni?o is significantly greater than that of the CP El Ni?o before the onset of El Ni?o.     

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