可照时间受地形的影响及其精细的空间分布

设计了起伏地形下可照时间分布式计算模型，讨论了不同纬度的坡度、坡向、遮蔽等地形因子对可照时间的影响。结果表明：可照时间的纬向分布特征明显；同一纬度，同一坡向的可照时间随着坡度的增加而减小；坡向对可照时间的影响复杂，不同坡向上的可照时间随季节和坡度变化；在太阳高度角较低的冬季，地形遮蔽对可照时间的影响显著，可明显地影响可照时间的空间分布，清楚表现出可照时间的非地带性。同时绘制了1：100万我国实际地形下精细的可照时间空间分布。     

大理州山地日照时间的时空分布特征

基于数字高程模型（DEM）模拟计算了大理州山地日照时间的时空分布,结果显示,除了日照百分率外,坡度、坡向和地形之间的相互遮蔽对日照时间的分布有很大的影响。冬季太阳高度角较小,地形遮蔽对日照时间的影响很大,夏季相对较小。遮蔽系数4月最大,12月最小。一年中的任意时刻随着坡度的增加日照时间减少。坡向对日照时间的影响有很强的...     

1961—2004年青海积雪及雪灾变化

利用1961—2004年青海省海西东部和环青海湖地区地面气象观测资料和北半球500 hPa高度场网格点资料, 整理了地表积雪序列和雪灾年表, 并对积雪的年代际变化特征和雪灾发生的机理及其成因进行了研究。结果表明:海西东部和环青海湖地区出现区域性雪灾的几率为15.9% (7/44), 而出现局部雪灾的几率仅为9.1% (4/44)。海西东部和环青海湖地区近44年来冬季累计积雪量的缓慢增加易形成雪灾和低温冻害。造成该区域主要降水的影响系统是高原槽、蒙古槽和高原低涡, 若后冬至春季北半球500 hPa极涡中心偏向西 (东) 半球, 青藏高原与我国东部沿海地区高度距平场形成“西低东高 (西高东低)”的距平分布型时, 海西东部和环青海湖地区容易出现多 (少) 雪年。     

江西强雷电活动分布与地形及其土地利用的相关性

为揭示地形及土地利用类型对江西地区强雷电活动影响，本文选取闪电密度极大值和闪电平均强度极大值作为反映强雷电活动的两个主要参数，利用江西雷电监测资料、地表植被遥感以及地形高程影像文件，提取不同土地利用类型以及海拔高度、坡度和坡向参数值，重点分析强雷电活动分布与土地利用及地形的相关性。结果表明：江西强雷电活动活跃区主要分布于城乡建设用地，雷电活动的落雷概率最高，其次为耕地。闪电平均强度极大值的雷电活动集中发生在赣州及九江的丘陵和山地，其土地利用类型主要为林地，其次为耕地。影响强雷电活动分布的地形因子主要包括坡度、坡向及海拔高度。     

环青海湖地区气候变化及其对水位影响的研究

分析青海湖地区1961～2000年气象观测资料得出，年度和四季的气温、地表蒸发以及年和夏季、冬季降水变化的气候倾向率均为正值，而春季、秋季降水变化的气候倾向率为负值。气温升高、地表蒸发加大的趋势比较显著，而降水增多的趋势不显著且年代际变化比较大，气温、地表蒸发等气象要素有向暖干化过渡的趋势，这种暖干化趋势是造成青海湖水位下降的主要原因之一。     

1961～2007年青藏高原四季开始日期的变化趋势分析

利用中国气象局国家气象信息中心提供的青藏高原60个测站1961～2007年逐日气温度资料,分析了青藏高原近47年来四季开始日期的时空变化特征和年代际变化趋势.结果表明,青藏高原的四季开始日期变化主要表现为春季和夏季的提前趋势,秋季和冬季的推后趋势,其中春季、冬季的变化显著,夏季、秋季的变化相对春季、冬季变化较小,四季开始日期的这种变化在增温明显的1990年代和21世纪初最为明显,并且春季和冬季开始日期的年代变化较大,而夏季和秋季开始日期的年际变化较大.这种变化趋势在空间分布上有所差异,春季和冬季开始日期变化的空间分布相似,春季和冬季开始日期的变化在空间上有相当的同步性而且都属于“中间高两边低”的分布状态,夏季和秋季开始日期变化的空间分布相似.此外,春季丌始日期在1990年代之前整体相对平稳并没有表现出明显的提早趋势,从1990年代开始变得较明显;夏季开始日期的提早变化相对平稳但年际变化较大;秋季开始日期的推迟相对平稳但是年际变化较大,1990年代有较明显的推迟趋势;冬季在1990年代表现出推迟趋势但是并不明显,但是到21世纪初表现出强烈的推迟.     

基于MODIS资料内蒙古气溶胶光学厚度反演分析

文章利用国家卫星气象中心引进的以暗像元特性为基础的气溶胶光学厚度反演软件,对内蒙古地区2009年12月至2010年12月的EOS/MODIS气象卫星资料进行反演,计算0.55μm气溶胶光学厚度,并提取119个气象台站气溶胶光学厚度值按盟市进行月平均、年平均值统计分析,寻找气溶胶光学厚度的空间分布特征和时间变化规律。结果表明:(1)内蒙古地区气溶胶光学厚度存在非常明显的空间分布特征,最高值区主要集中在中部和西部地区,东部的大部地区基本没有最高值出现。(2)内蒙古地区气溶胶光学厚度存在明显的时间变化规律。从1月份逐渐增加,到6月和7月份达到全年最大值,再逐渐降低趋势;春季和夏季最大,而秋季和冬季最小,夏季>春季>秋季>冬季。     

基于TM和ETM~+数据的玛纳斯河流域积雪时空分布特征研究

为了进一步研究玛纳斯河流域积雪的时空分布特征以及影响因素,应用遥感技术,以Landsat TM(美国地球资源探测卫星系统上加载的专题绘图资料)以及ETM+(增强型专题绘图资料)为数据源,利用雪盖指数法对研究区进行了积雪信息提取。通过对提取积雪信息的研究,分析了研究区的积雪时空分布的特征,并详细分析了高程、坡度、坡向以及其他因素对于积雪分布的影响。结果表明研究区积雪空间分布随高度和地形变化非常明显,积雪主要分布高海拔地区,而山间河谷地带则相对较少,同时积雪受季节影响较大,主要集中在秋、冬、春3个季节;并得出高程、坡向对积雪分布影响比较大,而坡度对积雪分布影响则相对较小的规律特征。     

巴州地区近40年降水量变化特征分析

应用巴州地区11个站的降水资料进行统计分析,结果显示：1.40a来全地区年降水量及夏季、冬季降水量都明显增多,春秋季节变化不大.2.年降水量主要表现为全州一致的多雨或少雨空间分布型,其次为南部、北部地区的降水变化的相反趋势,春季降水的空间分布与年相似.3.全年和夏、秋季降水量都存在7.3a的主要变化周期.     

基于Landsat 8的川西复杂地形太阳辐射估算研究

山地地表太阳辐射受坡度、坡向及地形遮蔽等影响,导致区域地表所接收的连续分布的太阳辐射量较难测量,而针对山地地表太阳辐射估算已成为目前研究的一个重点。为定量分析山地地表太阳辐射,本文利用Landsat8遥感影像、数字高程模型及气象观测数据计算相关参数,采用已有的太阳直射模型、天空散射模型和周围地形反射模型,综合估算研究区山地地表特定时刻的瞬时太阳辐射,同时根据气象站点获取的逐时太阳辐射和日总辐射量数据对结果进行验证。结果表明:该模型估算的山地瞬时太阳辐射误差均值为13.56 W/m2,日总辐射量误差均值为1.49 MJ/m2,估算值与观测值存在较好的一致性,结果误差小,精度高,参数可靠。山地太阳辐射分布与地形地貌密切相关,总体上阳坡大于阴坡,山脊大于山谷。山区太阳辐射随坡度增大而递减,同时受坡向、植被覆盖度等因素影响,坡面辐射量在一定坡度有略微上升趋势,当坡度大于太阳天顶角时,辐射量下降明显。山区受植被覆盖影响,随着地表植被的增加,地表辐射量呈下降趋势。      

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.     

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.     

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.     

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