青藏高原地区FGGEⅢb资料相对湿度场的分析与订正及其对预报影响…

本文用Ｃｒｅｓｓｍａｎ逐步订正法和青藏高原气象科学实验资料对高原地区１９７９年６－８月中６０个是次的ＦＧＧＥⅢｂ级资料相对湿度场进行了订正和分析，然后利用一有限区域数值模式，选择两例高原低涡过程，用订正前后的ＦＧＧＥⅢｂ相地湿度资料分别作初始湿度场进行了７２ｈ和４８ｈ预报试验。结果表明：高原地区相对湿度的高会位于其东南部，然后向西北逐渐递减，低值区位于高原西部。ＦＧＧＥⅢｂ相对湿度场能较好地反映高     

冷锋影响山东半岛的中尺度客观分析试验

使用山东半岛部分加密测站的锋面个例逐时资料，采用九点拉格朗日插值的逐步订正法，对地面场的资料进行了个尺度客观分析试验。通过对逐步订正法中观测前５个时次资料平均场、观测前１个时次资料场和观测时次资料场作为不同的初始估计场得到的客观分析结果的比较，提出在山东半岛进行中尺度客观分析，当观测资料分布不均，海面区域没有资料点及冷锋附近气象要素变化剧烈时，采用观测时次资料场作为有限区域网格的初始估计场而得到的结果较好。     

基于西南区域模式的四川强降水开始时间订正试验

基于2018~2019年5~9月和2020年8月四川地面观测降水数据（含区域自动站）,结合同时段西南区域模式08时起报的各要素场资料,开展了模式预报短时强降水开始时间的订正方法—最小偏差和订正法的本地化研究,并运用该方法对2020年8月强降水事件的开始时间进行了订正检验。结果表明:最小偏差和的订正法可以确定强降水开始时间相关物理因子订正阈值及最优阈值百分比;从2020年8月强降水的订正效果来看,该方法对短时强降水开始时间有一定的订正能力,强降水开始时间偏差减少2~8 h。      

逐步订正法中不同分析方案对降水预后影响的对比试验

利用Ｂｅｒｊａｍｉｎ等改进的逐步订正客观分析中的三种权重函数－圆形、椭圆形、曲率椭圆形，用１９９５年７月１３日００：００－７月１９日００：００的Ｔ６３Ｌ１６模式预报产品和实况资料及改进的有限区域嵌套高分辨率模式对上述三种方案提供的不同初值作了对比试验。     

青藏高原地区FGGEⅢb资料相对湿度场的分析与订正及其对预报影响的数值试验

本文用Ｃｒｅｓｍａｎ逐步订正法和青藏高原气象科学实验资料对高原地区１９７９年６—８月中６０个时次的ＦＧＧＥⅢｂ级资料相对湿度场进行了订正和分析，然后利用一有限区域数值模式，选择两例高原低涡过程，用订正前后的ＦＧＧＥⅢｂ相对湿度资料分别作初始湿度场进行了７２ｈ和４８ｈ预报试验。结果表明：高原地区相对湿度的高值区位于其东南部，然后向西北逐渐递减，低值区位于高原西部。ＦＧＧＥⅢｂ相对湿度场能较好地反映高原东部的分布，但在高原西部比实际明显偏大。订正高原上的初始湿度场（ＦＧＧＥⅢｂ相对湿度场）能明显改进高原地区的降水和形势预报，对环流的影响可达到高原东侧并波及高原的南北侧地区，显示了加密高原西部资料的重要性。     

非均一性气温气候序列订正方法的研究

本文采用一元线性回归订正法、逐步多元线性回归订正法、综合订正法和差值订正法对分布在全国２５省区的３５个台站进行了各方法气温资料订正效果等方面的试验研究。结果表明，四种方法中以逐步多元线性回归订正法的抉合误差值最小，其次是一元线性回归订正法，再其次是综合订正法和差值订正法。试验还表明，拟合误差值的大小于确定订正方程式的资料有关，平行资料年数越长越好，至少不宜短于１０年；相关系数越高越好，若将拟合误差     

ECMWF高分辨率模式2 m温度预报误差订正方法研究

文章提出了一种结合滑动双权重平均订正法和空间误差逐步订正法的综合订正技术,并对2016年5月1日至2017年5月1日期间24～168 h预报时效内欧洲中期天气预报中心(ECMWF)高分辨率模式的2 m最高和最低温度进行偏差订正和误差分析,主要结论如下:(1)ECMWF模式在江西省的温度预报整体上比实况偏低,最高温度尤为明显,模式温度的空间分布表现出显著的系统性偏差,且偏差在不同预报时效是稳定的,订正ECMWF模式温度具有可行性。(2)滑动双权重平均订正法中较长的滑动订正周期对模式温度预报有更好的订正效果,采用滑动订正周期20 d是比较理想的。滑动双权重平均订正法具有持续的订正能力,但在季节过渡期间订正效果可能并不理想,而空间误差逐步订正法能进一步提高滑动双权重平均订正法的预报订正质量。(3)温度预报准确率表明,滑动双权重平均订正法和空间误差逐步订正法综合订正技术较好地改善了站点温度的预报质量。经过订正后,模式最高温度24、48、72 h预报误差≤2℃的准确率分别从0.59、0.55、0.52提高到0.75、0.68、0.62,模式最低温度24、48、72 h预报准确率分别从0.84、0.83、0.82提高到0.89、0.87、0.85。订正后72 h最高和最低温度的预报准确率都大于订正前模式24 h的准确率。总体而言,该综合订正技术较好地订正了模式误差,且误差在空间分布上较均匀。(4)对于高山站而言,经过订正后的最高和最低温度与实况基本吻合。空间误差逐步订正法的订正量在±1℃之内,与滑动双权重平均订正后的偏差呈现一定的负相关,有正的订正效果。该综合订正法已成功运用于江西省精细化气象要素客观预报业务系统中。     

逐步订正法中不同分析方案对降水预报影响的对比试验

利用Ｂｅｒｊａｍｉｎ等改进的逐步订正客观分析中的三种权重函数——圆形、椭圆形、曲率椭圆形，用１９９５年７月１３日００：００—７月１９日００：００的Ｔ６３Ｌ１６模式预报产品和实况资料及改进的有限区域嵌套高分辨率模式对上述三种方案提供的不同初值作了对比试验。２４ｈ和４８ｈ的预报试验表明，椭圆形方案好于圆形，曲率椭圆形方案又好于椭圆形     

基于评分最优化的模式降水预报订正算法对比

使用2013年1月1日-2016年1月7日全国气象站观测资料,应用准对称混合滑动训练期,不改变雨带预报位置和形态,基于模式降水预报订正结果的TS评分最优化及ETS评分最优化,分别设计最优TS评分订正法（OTS）和最优ETS评分订正法（OETS）确定预报日各级降水订正系数,对2014-2015年降水数值预报进行分级订正,并与频率匹配法（FM）对比。结果表明:在24 h累积降水的多个预报时效订正中,无论是对欧洲中期天气预报中心、日本气象厅、美国国家环境预报中心和中国气象局的全球模式降水预报,还是对4个模式的简单多模式平均,OTS和OETS较FM在TS评分和ETS评分等传统降水检验指标上均更优秀,其中OTS在所有时效均能提高模式降水预报质量,为三者最优。在概率空间的稳定公平误差评分方面,OTS在各时效、各单模式及多模式平均等方面优势明显。在预报员对应参考时效上,OTS在24~168 h的24 h累积降水预报中的TS评分也优于主观预报。     

用逐步订正法做客观场分析

本文阐述了用逐步订正法做客观场分析的方法与步骤；阐述了初值的给出方法，猜测值的求算；扫描半径的选取并通过对１９９３年６月２７日的客观场的分析与天气图的分析对比发现，逐步订正法是可行的。     

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.     

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.     

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