1961年以来海南岛降水变化趋势分析

应用趋势分析法和聚类分析法等方法分析了海南岛全岛各站点1961～2004年雨量和雨日分布特征及其变化规律。结果表明：全岛年降水主要集中在5～10月份；年均雨量最多在中部和东部沿海地区，其中琼中最高（2438．9mm／a）；最少在西部沿海地区；不同等级降雨雨日分布与雨量基本一致。从年际变化看，全岛年雨量、早期雨量、汛期雨量均呈增加的趋势；全岛平均年降雨日数、毛毛雨日数以及年最长持续降雨日数均呈逐渐减少的趋；而全岛多年平均年大雨日数、暴雨日数则呈逐渐增加的趋势。     

台江县近46 a降雨和降雨侵蚀力变化特征分析

基于台江县气象观测站1970年1月—2015年12月逐年、逐月降雨量、雨日资料,采用线性趋向、累计距平等方法分析了台江县年、季降雨量和雨日变化趋势,结果表明:台江县近46 a年平均降雨量呈减少趋势,雨日显减少趋势,除暴雨及以上量级雨量呈增加趋势外,其余量级为减少趋势,降雨量、雨日及量级雨量的趋势均说明降雨越来越集中,发生强降雨的频率在增大,从而易引发的气象灾害将对人类的生产和生活产生不利的影响;四季降雨量和降雨日数分布不均且呈减少趋势,其中春季和秋季降雨日数呈显著减少趋势,且夏和秋两季出现强降雨的频率较大,秋季降雨量及降雨日数减少趋势率均为最大,秋旱发生的概率相对增大;年平均夜间降雨量大于年平均白天降雨量,在春季的4月最为明显,降雨强度夜间大于白天;逐年降雨侵蚀力及其降雨引起的土壤侵蚀潜能呈增加趋势。     

阿勒泰地区暖季昼夜降水气候特征分析

利用阿勒泰地区7个气象站1961—2013年5—9月逐日降水量资料,采用数理统计方法分析了阿勒泰地区暖季昼夜降水的气候统计特征及其变化。结果表明:1近53 a阿勒泰地区暖季昼夜雨量空间分布基本一致,总体表现为由山麓丘陵向河谷平原减少的特征。各站暖季昼夜雨量差和雨日差值均呈昼雨量多于夜雨量,昼雨日多于夜雨日的分布。2全地区昼、夜降雨日数的月际分布均表现为单峰式分布,峰值为7月。3全地区昼夜降水量均呈增多趋势,日数均呈减少趋势,夜雨量的增加速率大雨昼雨雨量,夜雨日数的减少速率小雨昼雨日数,表明该地区暖季昼夜降水的雨强增大,极端降水事件有所增加,并且这种变化在夜间表现得更为明显。4夜雨量和夜雨日数和昼雨量的年代际变化一致,均在20世纪90年代最多,70年代最少;昼雨日数在80年代最多,21世纪第一个10 a最少。暖季昼夜降水日数均在1972年发生了突变,夜雨量和昼雨量分别在1983年和1991年发生了突变。5暖季昼夜降水的Morlet小波分析表明虽然昼夜雨量和日数各自有其周期变化特征,但也有共性,目前夜雨量、夜雨日数、昼雨日数均处于偏少时期。     

1961—2010年北京地区降水变化特征

采用15个常规气象站1961-2010年逐日降水数据资料,分析了北京地区降水量、降水日数和降水强度的变化趋势,包括年和各季节的总降水量和降水日数,不同降水级别降水量、降水日数和降水强度变化趋势的时空特征。结果表明：在近50年内,北京地区平均年降水量和年降水日数、年降水强度均呈下降趋势;各季节中,夏季的降水量呈明显下降趋势,春季降水日数略有增加,夏季略有减少;降水强度在春季增大和夏季减小趋势明显;小雨雨量变化不明显,中雨雨量呈增加趋势,大雨和暴雨雨量呈明显降低趋势;小雨降雨日数略呈减小趋势,中雨降水日数呈显著增加趋势,大雨和暴雨降水日数呈较明显降低趋势;小雨降水强度略呈上升趋势,而大雨和暴雨的降水强度呈明显的降低趋势。     

1960-2012年陕西降水变化特征及可能成因分析

利用陕西82个气象观测站的降水观测资料、NCEP/NCAR的2.5°×2.5°再分析资料以及MODIS卫星的气溶胶产品,分析了1960-2012年陕西雨季和全年的降水量、降水日数变化特征,并讨论了大气可降水量和气溶胶对降水的可能影响。结果表明,近60年陕西雨季、全年雨量和降雨日数均呈南多北少分布,年总雨量和降雨日数均呈下降趋势,雨季总雨量呈增加趋势,而降雨日数呈降低趋势,雨季雨强增加,降水向雨季集中;陕西全年和雨季小雨雨量和降雨日数均呈现下降趋势,雨季10 mm以上的降水量和降雨日数均呈增加趋势,增加站点占所选站点的75.6%,雨季降水的增加主要是10 mm以上降水量的贡献。陕西全年总雨量的减少可能与整层大气可降水量的减少有关。全年和雨季5 mm以下降水量的减少应该与气溶胶对降水的抑制有关,雨季10 mm以上降水量增加与气溶胶对降水的促进作用有关。分析表明当AOD≥0.4时,雨季气溶胶对降水有一定的促进作用。总之,陕西全年小雨的减少以及雨季10 mm以上降水量增多,雨量向雨季集中应该与近几十年陕西气溶胶增加、气溶胶类型的转变有较大关系。     

广西6～8月分级降水的气候特征

利用广西87个站1977~2006年6~8月逐日降水资料,研究广西分级降水雨日、降雨量的时空分布特征及变化趋势。指出,广西6~8月小雨雨日最多,暴雨雨量最大。雨日和雨量的空间分布特点是:河谷地区少,山地地区多。广西30年来6~8月有效降水总雨日是不明显的增加趋势,总降雨量是明显的增加趋势,平均每年增加5.6mm。微雨雨日数是明显的减少趋势;大雨雨日和雨量是明显的增加趋势;暴雨雨日和降雨量都是显著的增加趋势,增加趋势最明显的是桂中南的平原地区。有效降水总降雨量的增加趋势主要是由于大雨、暴雨雨日的增加趋势引起的。     

广西天峨近44年来不同等级降水量与降水日数变化特征

利用天峨1971-2013年逐日降水量资料,利用线性趋势和Mann-Kendall突变检验等方法,对天峨不同等级降水量和降水日数的变化特征进行分析。结果表明:年降水量和降水日数均呈减少趋势,降水日数的减少更加显著;小雨量(日数)呈极其显著的减少趋势,中雨量(日数)和大雨量(日数)呈不显著的减少趋势,暴雨量(日数)则呈增加趋势。年降水日数、小雨量(日数)、中雨日数、大雨量、暴雨量(日数)突变特征明显;年降水量(日数)、小雨量(日数)、中雨量(日数)、均有一致的22a主周期变化,而大雨量(日数)均有一致的20a主周期变化,暴雨量(日数)均有一致的26a主周期变化。     

江淮地区不同相态降水日数变化特征

基于1960—2013年106个地面气象站观测数据,对江淮地区雨、雪、雨夹雪及冻雨4种相态降水日数气候特征、月际分布、年际变化、长期趋势以及各相态降水日数与纬度、海拔高度之间关系等方面进行探讨,结果表明:江淮地区全年降雨日数为各相态降水日数之最多,空间分布上呈南多北少的分布特点,雪日数空间分布与雨日数相反,为北多南少;雨夹雪和冻雨日数主要表现为纬向差异,东部沿海少于西部内陆;在近54a中,各相态降水日数区域平均值均呈减少趋势,其中雨、雪、雨夹雪减少趋势显著;从各站点降水日数变化趋势的空间分布看,虽然各相态降水日数普遍以减少趋势为主,但冻雨显著减少的站点最少;除降雨主要出现在3—8月,其他相态的降水出现较多的时段为11月至翌年3月;4种相态降水日数中,降雪和冻雨日数与海拔高度关系最为密切,呈显著正相关,其次为雨夹雪。     

鹤山降雨的气候特征及趋势分析

利用鹤山1970～2009年共40a逐日降雨资料,用统计的方法诊断分析了各量级雨日和雨量的气候特征及变化趋势。结果表明:鹤山40年以来降雨集中期为4～9月,中雨以上量级雨日及雨量均呈双峰分布,量级越大双峰分布越明显;雨日及雨量在时空上存在明显干季、雨季分布,年内降雨表现为量级越大、季节性越明显、集中程度越高的特征。雨日量级越大年际变化越大;雨日、小雨日、中雨日、大雨日呈减少趋势,雨日及小雨日减少趋势明显,中雨日及大雨日减少不明显;暴雨日、大暴雨日呈增多趋势,大暴雨日增多的趋势比暴雨日增多的趋势大。鹤山年雨量主要由中雨、大雨、暴雨组成,其中大雨贡献最大;过去40a暴雨及大暴雨增多趋势较明显;年总降雨量及大雨量呈减少的趋势,但减少不明显;小雨量、中雨量减少趋势明显。     

浙江省不同强度降水日数的时空分布特征

根据浙江省1961～2010年逐日降水量资料,在对不同等级降水日数进行趋势分析的基础上,运用Mann-Kendall检验、等值线分布等方法对显著降水事件进行时空分布特征的研究,探讨浙江省不同等级降水日数的时间演变趋势和空间分布特征。结果表明:近50 a来,浙江省总降水日数呈明显的下降趋势,相当于每10 a减少4.82 d,其中小雨日数占总雨日的73.00%。在时间变化上,总雨日和小雨日均在1980年代中后期发生突变,转为急剧下降趋势,且小雨日的减少趋势略超前于总雨日。在空间分布上,年降水日数和小雨日数的空间分布基本一致,在台州、宁波出现了高值中心,低值区域主要分布在浙江东北部,而浙西南地区变化平缓;空间趋势分布表现为全省一致的减少趋势,东部沿海下降趋势显著,而内陆地区下降缓慢。浙江省年雨量及其气候倾向率的分布,均表现出较明显的"东—西"向差异,和地形高低有一定关系。年雨量整体表现为增加趋势。以上研究说明,在近50a来,浙江省发生极端天气事件的概率明显增加,干旱或洪涝的趋势或风险加大。     

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