两次飞机增雨作业效果的非参数检验

本文针对我省飞机增雨作业区域的不确定性，采用移动的“影响区”和一个与之相对应的“对比区”的划分方法，对１９８９年９月２５日和９月２６日两次飞机增雨作业，用Ｗ－Ｍ－Ｗ法的ｕ检验、符号检验和Ｗｉｌｃｏｘｏｎ带符号的秩和检验三种方法［１］对作业的增雨效果进行了非参数检验。结果表明：作业开始后３小时“影响区”与“对比区”雨量有显著性差异，人工催化使影响区雨量较对比区明显增大；而作业开始后３小时影响区雨量与同区域作业前３小时雨量无显著差异或比作业前减小，这可能是由于作业时段处于系统后部，降水系统和云层已开始减弱，人工增雨率被自然降水的时间变率覆盖所致。     

X波段移动天气雷达产品在人工增雨中的应用

2020年5月19日四川省绵阳地区实施了一次人工增雨作业,利用X波段移动天气雷达产品,对作业前后雷达回波和地面降水资料进行了对比分析。结果表明：反射率因子大于20dBz、垂直累计液态水含量（VIL）达到 0.3kg/m² 以上时,云层具备较好的降水条件,有利于实施人工增雨作业;增雨作业后,反射率因子最大强度、平均强度和降水回波面积都明显增大,回波中心 VIL 显著上升;利用对比区和影响区降水资料分析得到相对增雨率为 18.9%,绝对增雨量达 6.2mm,作业催化取得较好效果。     

基于区域历史回归法的雷州半岛火箭增雨作业效果检验

利用ERA5再分析资料,区域自动站雨量资料以及双偏振雷达基数据,采用区域历史回归方法,对2020年7月4日雷州半岛火箭人工增雨作业进行物理检验和统计检验。结果表明:作业后作业区域云系云冰含量大幅增加,强回波区面积增大,回波顶高度升高,平均回波强度显著增加。选取1971—2000年作业影响区和对比区逐年7月的平均日降水量资料作为历史样本建立回归公式,结合作业当天区域自动站的雨量资料,计算得出日降水量和作业后3 h累积降水量的绝对增雨量分别为11.07 mm和2.32 mm,相对增雨率分别为51.08%和38.73%,均通过了置信水平为α=0.05显著性检验。因此,雷州半岛开展人工增雨作业对缓解气象干旱,满足水库蓄水等有重要意义。     

新安县人工增雨效益评估办法

根据作业云回波面积和强度的变化,可定性判断人工增雨是否有效。对有效增雨,可根据高炮有效控制半径,计算出影响面积;根据作业区样本点作业后比作业前的降水平均增量和对比区样本点作业前后雨量平均变化量,可确定作业区平均增雨量(mm);根据增雨量,可计算出影响区增雨质量,并由此计算出经济效益。     

对流云人工增雨潜力初步探讨

利用在古田水库建立的以新一代天气雷达为主,包括稠密地面雨量站网等人工增雨综合监测技术系统,结合古田水库“蓄水型”人工增雨外场试验研究对流云降水量、降水效率和人工增雨潜力。研究表明:①试验区对流云自然降水效率平均约为1222×103m3,最大为1626×103m3;②人工催化后18~36 min,平均降水效率提高6个百分点,每次作业降水量增加395.5×103m3;相对增加28.36%,最大分别增加10个百分点,为972×103m3和59.78%;③每次作业水库入库流量增加143×103m3;④综合12年(1975~1986)古田人工增雨试验和2004年古田水库“蓄水型”人工增雨效果分析,可以认为对流云云内含水量大,有明显的增雨潜力。     

人工增雨效果的数值统计评估方法

利用1995～2001年河南省春季降水资料，采用数值预报与统计相结合的方法，对飞机人工增雨的效果进行检验。该方法的基本思路是根据降水的气候特征设定增雨效果的评估区，在同一评估区内应用数值模式MM5V3对历史降水过程的降水量进行数值预报，从而获得一组预报雨量，对非增雨过程的数值预报雨量与降水实况进行统计分析，建立预报雨量与实况雨量的数理统计关系。对增雨作业过程的降水同样采用相同的数值模式进行预测，并与增雨后的实况雨量比较，从而得到飞机人工增雨效果。评估结果表明：1995～2001年春季飞机人工增雨效果比较明显，豫北区(Ⅰ区)平均为16．7％，豫东区(Ⅱ区)平均为19．3％。     

古田水库2004年蓄水型人工增雨作业分析

将宁德市人工增雨指挥系统应用到2004年6~8月古田水库抗旱蓄水型人工增雨作业和进行综合效果评价,取得显著效果。5次作业过程,水库流域共增雨16117×104m3。结果表明:新一代天气雷达宁德市人工增雨指挥系统在实际作业中应用,对旱情的监测、作业条件确定、把握最佳作业时机、场外作业指挥、云团跟踪分析、效果综合评价等方面发挥了很好的作用,使人工增雨作业科学化、客观化、系统化,提高了工作效率,增强了工作效果,扩大了社会影响。     

2009年飞机人工增雨作业抗春旱效益评估

本文介绍了人工增雨作业效益的一种评估方法——区域雨量对比法,以及该方法在实际业务工作中的应用:统计了2009年春季四川省飞机人工增雨的作业情况,采用区域雨量对比法对每次作业进行效益计算,得出每次作业的影响面积、影响区降水、对比区降水、增雨量、增加的降水量等,根据春旱期间的降水情况与旱情缓解情况,对人工增雨抗春旱的效益进行了分析评估,并尝试计算出缩短春旱的持续时间,给出了评估结论,并对该方法的应用进行了讨论。该评估方法对于人工影响天气业务工作,具有一定的实用性和可操作性。      

新安县人工增雨效益评估办法

根据作业云回波面积和强度的变化，可定性判断人工增雨是否有效。对有效增雨，可根据高炮有效控制半径，计算出影响面积；根据作业区样本点作业后比作业前的降水平均增量和对比区样本点作业前后雨量平均变化量，可确定作业区平均增雨量（mm）；根据增雨量，可计算出影响区增雨质量，并由此计算出经济效益。     

2009年飞机人工增雨作业抗春旱效益评估

本文介绍了人工增雨作业效益的一种评估方法——区域雨量对比法,以及该方法在实际业务工作中的应用：统计了2009年春季四川省飞机人工增雨的作业情况,采用区域雨量对比法对每次作业进行效益计算,得出每次作业的影响面积、影响区降水、对比区降水、增雨量、增加的降水量等,根据春旱期间的降水情况与旱情缓解情况,对人工增雨抗春旱的效益进行了分析评估,并尝试计算出缩短春旱的持续时间,给出了评估结论,并对该方法的应用进行了讨论。该评估方法对于人工影响天气业务工作,具有一定的实用性和可操作性。     

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.     

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