改进的综合气象干旱指数在保山市的适用性分析

针对综合气象干旱指数CI会在某些情况下指示旱情等级不合理变化的问题,采用线性递减权重方案代替等权方案计算30 d、90 d降水和可能蒸散,得到改进的综合气象干旱指数CI_(new);从气候统计特征、旱情等级变化、干旱频率和典型干旱过程演变4个方面与CI进行比较,讨论CI_(new)在云南保山市的应用效果及其适用性。结果表明:(1)CI_(new)基本保持了CI反映的干旱频率分布特征,但干旱次数和中旱频率增加。(2)CI_(new)明显地改善了CI指数"指示旱情等级不合理加剧"现象;在无明显降水时段指数下降较缓慢,没有CI指数有时会出现的"指示旱情缓解"现象。(3)改进的综合气象干旱指数CI_(new)对干旱的演变描述更客观合理,适用于保山市气象干旱监测和评估服务。     

标准化降水蒸发指数在中国区域的应用

利用中国气象局160个站1951～2010年月降水和月平均气温资料,分析了最近定义的一种干旱指数——标准化降水蒸发指数(SPEI)在我国不同等级降水区域的适用性,并与标准化降水指数(SPI)和湿润指数H进行了对比分析。结果表明:1)在我国年均降水量大于200 mm的地区,各种时间尺度的SPEI分析均适用;在干旱区(年均降水量小于200 mm),只有12个月以上的大尺度SPEI分析适用性较好;其中12个月尺度的SPEI分析在各区适用性最好。2)由于干旱区冬季的潜在蒸发量和降水量0值均较多,导致1、3、6个月的小尺度SPEI分析在该区不适用。3)与SPI和H指数相比,SPEI既能充分反映1997年气温跃变以后增温效应对干旱程度的影响,又可作为监测指数识别干旱是否发生和结束,能较准确地表征干旱状况。     

CI指数及SPEI指数在长江中下游地区的适用性分析

根据综合气象干旱指数(CI)在长江中下游地区应用中存在的不足,首先对CI中SPI指数等权累积降水进行合理的非等权处理及MI指数的优化,得到改进的综合气象干旱指数。然后利用1962—2013年长江中下游地区164个气象站的观测资料,对比分析了改进的综合气象干旱指数和标准化降水蒸散指数(SPEI)在长江中下游地区的适用性效果。结果表明:改进的综合气象干旱指数物理意义明确,解决了原CI指数对干旱开始时间、旱情发展中不连续加重现象和旱情解除时间滞后等不足,特别是对长江中下游地区的旱涝急转现象反映及时准确;设计的多时间尺度综合气象干旱指数与SPEI指数相关系数平均达0.8以上,说明得到的多时间尺度综合气象干旱指数对旱情的分析评估能力较强。经过适用性对比分析证明,月尺度综合气象干旱指数在江苏和安徽省应用效果要优于SPEI指数,湖南、江西和湖北省月尺度综合气象干旱指数在10—4月间的评估效果更好,SPEI指数在5—9月更优。因此,改进的综合气象干旱指数对长江中下游地区干旱分析与监测、预报预警等具有良好的推广应用价值。      

干旱指数在淮河流域的适用性对比

利用淮河流域河南、安徽、山东、江苏4省170个站1961—2010年逐日气温、降水以及土壤墒情和干旱灾情资料,从干旱年际变化、季节演变、空间分布、典型干旱过程诊断、不合理跳跃点以及与土壤墒情、干旱灾情相关性等方面,对比分析降水距平百分率 (Pa)、Z指数、标准化降水指数 (SPI)、相对湿润度指数 (MI)、综合气象干旱指数 (CI) 和改进的CI (CINew) 在淮河流域的适用性。结果表明:各干旱指数对淮河流域的典型旱年均有较好的诊断能力;在干旱季节演变及空间分布的诊断方面,Pa,MI,CI和CINew与实际较为吻合,而Z指数和SPI诊断效果较差;在典型干旱过程诊断以及不合理跳跃次数方面,CI和CINew更能刻画出干旱发生发展机制,而Pa,Z指数,SPI,MI效果较差;与土壤墒情和历史干旱灾情相关性方面,CI和CINew比Pa,Z指数,SPI,MI具有更好的相关性。即对于淮河流域的干旱监测诊断,CI和CINew要优于Pa,Z指数,SPI及MI,具有更好的适用性。     

标准化降水蒸散指数在中国干旱监测的适用性分析

针对国际上最新提出的干旱指数——标准化降水蒸散指数(SPEI),从拟合优度检验、对历史干旱事件的刻画、以及SPEI与SPI、PDSI指数的关系角度出发,全面分析了SPEI指数在中国区域的适用性。结果表明,只有在冬季且时间尺度小于3个月时,新疆南部、西藏西北部和华北至河套地区的样本不服从Log-logistic分布;而在冬季且时间尺度大于3个月以及夏季的任何时间尺度,中国范围的样本都符合Log- logistic分布,所得SPEI指数可靠。SPEI指数能够准确刻画几次特大干旱事件的地域中心、影响范围和强度。与SPI指数相比,SPEI指数引入了影响干旱的潜在蒸发项,能够更精确地刻画干旱。而与PDSI指数相比,SPEI指数具有多时间尺度特征,计算更简便。     

多种干旱指数在中国北方的适用性及其差异原因初探

利用中国北方(东北、华北、内蒙古、黄淮以及西北地区中东部)12个省(区)267个站点逐日气象数据和典型站点土壤相对湿度资料,对目前应用最为广泛的5种干旱指数在该区域的适用性进行了评估,并对各指数监测结果差异原因进行了初步探讨。结果表明,在我国北方干旱监测中,MCI和K指数的监测效果要优于SPI、Pa和SPEI指数。MCI指数对研究区春旱的监测尤具有优越性,K指数对偏东、偏南区域的夏、秋、冬季旱情的监测能力略优于MCI指数,Pa和SPI指数对夏、秋季的旱情监测准确率较高,而SPEI指数对夏旱有较强的监测能力。Pa指数、SPI指数以及SPEI指数监测准确率低主要是因为这些指数监测偏轻或漏测的频率较高,而K指数对东北区域的春旱漏测频率也较高,漏测频率高达29%。各类干旱指数的监测能力与各自考虑的干旱影响因子及其时间尺度密切相关,抓住主要因子和主要影响时间尺度是准确监测旱情的关键。     

洪湖水位对不同时间尺度SPEI/SPI干旱指数的响应研究

流域洪涝与干旱对流域水资源利用及生态平衡具有重要影响。探讨流域水文要素与气候因子的关系,是应用气候指数进行流域旱涝监测和影响评估的重要前提。基于四湖流域8个气象站及洪湖湖区水位代表站逐月观测资料,从月、季及连续时间序列月平均标准化水位距平与不同时间尺度SPEI/SPI干旱指数的相关分析,研究洪湖水位对不同时间尺度SPEI/SPI指数的响应。结果表明：四湖流域洪涝与干旱主要受降水控制,洪湖水位与SPEI/SPI干旱指数具有较好的相关性,但其相关程度因不同月份和季节及干旱指数的时间尺度存在一定差异,总体上洪湖水位与4~6个月时间尺度SPEI/SPI干旱指数相关性最为密切,表明洪湖水位对降水及蒸散发导致的水分盈亏的响应具有时滞效应和累积效应,当前月洪湖水位受当月及前3~5个月水分盈亏的共同影响。基于5个月时间尺度的SPEI/SPI干旱指数监测历史时期洪湖水位变化具有很好的一致性。研究结果为基于常规气象观测资料进行四湖流域旱涝监测提供了理论依据,同时可为其他流域旱涝监测与评估提供借鉴。     

TRMM降雨数据在甘肃省干旱监测中的应用

热带降雨测量卫星(tropical rainfall measuring mission,TRMM)的微波数据能够提供高时空覆盖性的降水速率数据,可用于区域尺度的干旱监测。选取甘肃省为研究区域,利用28个气象站降雨资料对TRMM月降雨产品进行相关性分析,同时计算站点标准化降水指数(SPI)检验基于TRMM数据构建的降水距平百分率(Pa_TRMM)和降水状态指数(PCITRMM)监测干旱变化的时间序列信息,进一步分析区域干旱时空变化规律。结果表明:(1)TRMM数据精度较高,月降水、年降水数据的相关系数R分别为0.92和0.95,均通过α=0.01显著性检验;(2)Pa_TRMM、PCITRMM与SPI指数的逐月变化有较好一致性,能够有效监测干旱事件;(3)Pa_TRMM和PCITRMM监测出的2000年甘肃省春旱和盛夏旱以及2009年春夏连旱的发生发展过程与实况相符,只是在干旱程度的监测上略有差异。     

五种干旱指标在安徽省应用研究

运用安徽省78个代表站1961-2008年逐日气温和降水资料,采用累积频率法对五种干旱指标的阈值进行修正,用修正后干旱指标来分析安徽省干旱的年际变化、季节演变及空间分布等特征.结果表明:五种干旱指标按照干旱过程计算得到历年总干旱日数的演变趋势基本一致,干旱日数较多的年份与安徽省历史典型大旱年记录非常吻合;Z指数和SPI指数无明显季节变化趋势,而Pa,MI和CI三种指标季节变化趋势明显且基本一致,安徽省秋旱最多,夏旱次之,冬、春旱相对较少;Z指数和SPI指数尤明显的空间分布特征,Pa,MI和三种指标的空间分布基本一致,呈现纬向空间分布,干旱频率自北向南递减;对于安徽干旱监测业务来说,五种干旱指标中CI指数为最优.     

基于SPEI和SPI指数的西江流域干旱多时间尺度变化特征

利用1959 2016年西江流域34个国家气象站的月降水和月平均气温资料,计算了西江流域近57年来不同时间尺度(1个月、3个月、6个月和12个月)的标准降水指数(Standardized Precipitation Index,SPI)和标准降水蒸发指数(Standardized Precipitation Evapotranspiration Index,SPEI)。在此基础上,对比分析了干旱的时空演变特征及干旱指数的表征差异。结果表明:(1)在12个月尺度上,近57年来西江流域大部分地区干旱强度呈现极显著的加重趋势,干旱频率也呈现极显著的上升趋势。(2)在3个月尺度上,西江流域春旱和秋旱较为频繁,影响范围广,而夏旱和冬旱频率低,影响范围小。在12个月尺度上,2000年以后,干旱频率最高,影响范围也更广。(3)干旱频率高、易旱区范围最广的时期为20世纪80年代,其次分别为2010 2016年、20世纪60年代和21世纪00年代,在20世纪70年代和90年代易旱区影响范围较小,干旱频率较低。在12个月的尺度上,SPEI和SPI指数旱涝评价结果整体比较接近。(4)在1个月、3个月和6个月的尺度上,SPEI指数整体上低于SPI指数。尤其在冬季和春季各月SPEI指数远远低于SPI指数。     

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