近30年西藏地区大气可降水量的时空变化特征

利用1980-2009年NCEP/NCAR再分析资料以及同期西藏地区34个气象站的月降水量资料,分析了该地区大气可降水量和降水转化率的时空变化特征.结果表明:(1)该地区大气可降水量具有从东南向西北逐渐递减的空间分布特征;近30年大气可降水量呈逐渐减少趋势且年际变率相对较小,还表现出显著的季节差异,即夏季大气可降水量最大、冬季最小;多、少雨年大气可降水量的空间差异不显著,说明西藏地区的空中水汽含量相对稳定,有利于空中水资源的合理开发和利用.(2)降水转化率在那曲中东部和西藏东南部最高、西藏西北部最低;近30年西藏地区降水转化率呈逐渐增加趋势且年际变率较大,其季节变化与大气可降水量的变化规律一致;降水转化率的高低在一定程度上决定了某年为多(少)雨年.(3)西藏地区大气可降水量和实际降水量的空间分布规律接近,但其时间变化趋势与同期降水量增加的趋势正好相反;大气可降水量转化率与实际降水量的变化趋势基本一致,降水转化率的升高(降低)对应着降水量的增多(减少).     

基于2001～2009年MODIS资料的西藏地区大气可降水量分布特征

利用2001~2009年MODIS近红外的大气可降水的逐月资料,分析了西藏地区大气可降水量时空分布特征及与实际降水量之间的关系。结果表明:西藏大气可降水量时空分布不均匀,空间分布由东南至西北递减;7、8月份大气可降水量最大,夏季大气可降水量占全年的50%;2001~2009年间西藏大气可降水量呈增加趋势,阿里地区、山南地区以及昌都地区增加明显;大气可降水量与实际降水量呈明显负相关,相关系数为-0.688。      

近45a郑州夏季大气可降水量及其降水转化率分析

根据郑州站1964—2008年月平均探空资料及地面降水资料,分析了近45a郑州夏季大气可降水量和地面降水量的演变特征,并在此基础上讨论了与该站夏季降水转化率的关系。结果表明：（1）郑州站夏季可降水量和降水量存在明显的年际变化,可降水量存在准2a的振荡,而降水量主要表现出准4～6a的振荡周期;（2）在长期线性趋势上,可降水量呈微弱的下降趋势,而降水量呈线性上升趋势,两者都在1990年代末发生突变;（3）郑州站夏季降水转化率与降水量存在相同的年际振荡周期和线性增加趋势,其降水转化率在21世纪初发生突变。     

潍坊市地面水汽压时空分布特征及其影响因素

基于1961—2015年潍坊市9个气象观测站逐月地面水汽压及其他气象要素的观测数据,利用气候倾向率、经验正交函数(Empirical Orthogonal Function,EOF)、M-K(Mann-Kendall)突变检验和相关系数等方法,分析了潍坊市地面水汽压的时空分布特征及其影响因素,为合理开发云水资源提供理论依据。结果表明:1961—2015年潍坊地区年与春季、秋季、冬季地面水汽压均呈上升的趋势,春季地面水汽压上升最明显,夏季地面水汽压呈略下降的趋势;潍坊市地面水汽压年代变化明显,20世纪80年代地面水汽压最低。近55 a潍坊市地面水汽压月变化呈明显的单峰型,最大值出现在7月,最小值出现在1月。潍坊市地面水汽压在1989年发生突变,突变后呈明显上升的趋势。近55 a潍坊地区年和四季地面水汽压均呈由西北向东南方向递增的空间分布特征,最低值均出现在青州地区,最高值均出现在诸城地区,主要受地理位置和海拔高度影响造成的。特征向量表明潍坊市地面水汽压具有空间一致性的变化特征,呈西北—东南反向分布。潍坊市地面水汽压受多种气象因素的影响,地面水汽压与相对湿度、气温、降水量均呈显著的正相关关系,地面水汽压与日照时数、蒸发量、风速均呈显著的负相关关系。     

我国大陆上空可降水量的时空变化特征

利用1958-2001年NCEP/NCAR和ECMWF月平均再分析资料,由地面积分到300 hPa计算了我国大陆上空整层大气的可降水量,对可降水量的时空变化规律及我国大陆上空可降水总量变化特征进行了分析,并利用部分站点探空资料对大气再分析资料获得的结果进行了校验.结果表明:我国大部分地区年平均可降水量表现为减少趋势,而西北地区和华南沿海呈增加趋势;各个季节平均可降水量趋势变化特征并不相同;去除线性趋势的可降水量异常变化主要表现为全国大部分地区一致的年代际振荡,在1965年可降水量由偏多向偏少转变,而在1987年前后可降水量又由偏少向偏多转变;我国大陆上空年平均可降水总量的变化特征主要表现为从1960s中期的持续减少和大致从1980s后期的增加趋势特征.     

近55年来中国西北地区降水变化特征及影响因素分析

利用1961-2015年中国西北地区128个站的降水观测资料和NCEP再分析资料,分析了年、季降水量与降水日数变化总趋势及其区域分布特征,并采用与平均温度、气候指数相关性来分析和讨论其所受的影响因素。结果表明:(1)西北中西部年降水量呈增加趋势,增加趋势位于0.1%·(10a)-1~10.0%·(10a)-1;西北东部年降水量呈减少趋势,减少趋势均小于5%·(10a)~(-1);春季、夏季和秋季西北西部大部分地区降水量是以增加趋势为主;东部主要为减少趋势,但是在冬季几乎所有站点的降水量呈增加趋势;(2)西北西部降水日数以增加趋势为主,东部地区降水日数以减少趋势为主,大部分站点年降水日数在冬季呈现增加趋势,其他季节则基本表现为西北西部增加、西北东部减少;(3)河西走廊西部、青海高原边坡、西北东部年降水量与年平均气温呈负相关,青海高原年降水量与年平均气温呈正相关,西北地区大部分年降水日数与年平均气温呈负相关;(4)北疆、南疆和西北东部37°N以南地区年平均降水量变率与年平均温度变率呈现负相关,且相关系数较大,而其余地区为正相关;(5)西风带影响西北大部分地区年降水量,东亚季风和南亚季风主要影响西北地区中北部和南部的年降水量。     

三江源地区近50年降水变化分析

利用西北及三江源(黄河、金沙江及澜沧江)地区122个气象观测台站1956—2004年近50年的逐日降水量及月总降水量资料,分析了三江源地区降水变化特征。结果表明:近50年来三江源地区的年降水量呈减少趋势,减少幅度为6.73mm/10a;降水日数的趋势变化呈较为明显的减少趋势,递减率为2.7d/10a;平均降水强度总体呈弱的增强趋势,增强速率平均为0.20mm/d/10a,增强幅度比中国西北地区平均水平强;从4~9月最长无降水日数趋于增长反映出西北地区干旱化的趋势。     

1961~2010年西北地区极端气候事件变化特征

利用1961~2010年西北地区131个气象站的逐日平均气温、最高和最低气温及逐日降水资料,分析了西北地区极端气候事件的变化趋势及空间分布特征。结果表明:气候变暖背景下,西北地区近50 a来气温整体呈增加趋势,极端高温事件增多,极端低温事件减少;降水量呈微弱的增加趋势,极端降水事件增多;极端高温日数分别在1982年和1996年发生转折,95%、99%极端低温日数均在1980年前后发生突变,95%、99%极端降水日数分别在2000年和1980年出现转折,这与气温和降水的变化趋势一致。极端低温日数减少的幅度大于极端高温日数增加的幅度,表明气温日较差呈减小趋势,存在非对称性增温特征。空间上,增温率大的区域其极端高温日数增加,极端低温日数显著减少;95%、99%极端降水日数增率大的区域多位于降水量倾向率较高的地区。     

1961—2016年汛期东天山北坡不同量级降水日数时空变化特征

利用东天山北坡5个国家级地面气象站1961—2016年汛期(5—9月)逐日降水资料,采用线性趋势、相关系数、多项式拟合及Mann-Kendall突变方法,探讨不同量级降水日数时空演变特征及与汛期总降水量的关系。结果表明:随着降水量级升高,对应降水日数迅速减小;近56 a总降水日数、中雨日数、大雨日数和暴雨日数均呈增加趋势,其中大雨日数增加趋势最明显,对总降水日数的增加贡献最大,小雨日数呈明显的减小趋势,大雨日数在1991年发生突变,暴雨日数在1980年发生由少到多的突变,其他降水日数表现为下降趋势,但均未发生突变;从不同量级降水日数空间分布可知,除了小雨日数其他量级降水日数都是以木垒为高值中心,逐渐向东西两侧减小,最低值一般出现在伊吾和吉木萨尔;汛期随着降水量级上升,降水日数与汛期总降水量相关系数也不断增大,小雨日数与总降水量相关性最差,与大雨日数相关性最高。     

运城市近46年作物生长季降水变化及农业旱涝特征分析

利用运城市13个气象站1974—2019年作物生长季(4—10月)降水和气温统计数据,采用线性回归、气候倾向率和旱涝指数等方法,分析运城市近46年作物生长季降水量、需水量和农业旱涝的时空变化特征。结果表明:(1)作物生长季降水量呈弱减少趋势,变化倾向率为-1.55 mm/10 a;春、秋季为弱增加趋势,夏季明显减少;各月分布不均,7月最多,4月最少,7—9月降水量占作物生长季总降水量的59.8%;在空间上,表现为从东南向西北的递减式分布。(2)需水量呈明显增加趋势,变化倾向率为9.12 mm/10 a;春、夏、秋三季需水量均呈明显的增加趋势,春季增加最快,而夏季需水量占比最大达52%;空间上表现为自西向东递减。(3)旱涝指数平均为0.64,总体属于中度干旱气候类型;年际变化较大,但变化趋势不明显;5月和9月旱涝指数呈弱增加趋势,其余月份均呈弱减小趋势;干旱发生频率为95%;旱灾以春旱为主,涝灾以秋涝为主;旱涝指数自西向东逐渐增大。(4)平均水分亏缺250.1 mm,其中夏季亏缺最多,秋季亏缺最少;水分亏缺自西向东减少,亏缺最严重的是西北地区;平均积分湿度指标为65%,为可旱作农业区,但整体表现为下降趋势,干旱有增多趋势。     

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