The relationship between El Niño Southern Oscillations and cereal production in Sahel

The effect of drought on crop yield and water resources has been an important socio-economic concern in the Sahel region of Africa. The most severe droughts in the Sahel region occurred during the strong El Niño Southern Oscillation (ENSO) events. There is thus increased need to understand the stochastic relationship between such physical mechanism like ENSO and crop yield. In this paper, such a relationship is investigated using a wavelet approach. Our result shows that a statistically significant relationship exists between ENSO and cereal production in the region. In particular, El Niño events are devastation to millet yield with little or no impact on maize and sorghum production. This can be attributed to the lower length of growing period for maize and sorghum compared to millet. On the other hand La Niña events favor cereal production and mirrored sorghum yield during the La Niña years of 1973–1976. The potential value of ENSO-based rainfall forecast and socio-economic impact on local population in Sahel region are discussed.     

洞庭湖流域冬季降水的时空变化及与全球海温的关系

论文基于1961-2015年洞庭湖流域96个气象站点逐月降水数据和英国哈德莱中心月平均海表温度资料,利用EOF、Morlet小波和偏相关分析等方法,对洞庭湖流域冬季降水的时空变化和周期特征进行分析,并探讨影响流域冬季降水的关键海区及其关键时段。结果表明：在年际时间尺度上,洞庭湖流域冬季降水主要存在全区一致型、南北反向型和中部-南北部反向型3个模态,各模态分别具有12 a、16 a和7 a左右的长周期以及3 a左右的短周期。在与全球海温的关系方面,流域冬季降水与ENSO和南海海温均存在显著相关,平均而言,在ENSO处于暖位相或南海海温偏高时,流域冬季降水易偏多,反之,则流域冬季降水易偏少;但ENSO和南海海温对流域冬季降水的影响范围及其关键时段存在明显差异,其中ENSO的影响范围主要分布在流域南部,其在前期10月与流域冬季降水相关性最好,而南海海温的影响范围集中在流域东部,其在次年2月与流域冬季降水相关性达到最高。     

Climatology and Trends of the Temporal and Spatial Distribution of Sandstorms in Inner Mongolia

The temporal and spatial distribution of sandstorms have been investigated statistically for a period of 40 years (1961–2000),using data from 118 observatories in Inner Mongolia, P.R. of China. In terms of climate variations, the effects of changes in climate(affecting parameters such as precipitation, temperature, ENSO activities, etc.), ecological systems and human behavior on the space-time distribution of sandstorms have been studied. It is shown that in Inner Mongolia nearly all sandstorms occurred inthe central-western region during 1961–2000. Their frequency decreased from the 1960s to the 1990s. The mean annual variationshows that spring is the main sandstorm season, especially April. In view of connection with climate variations, dry and cold periods correspond with a high frequency of sandstorms,wet and warm periods with a low frequency. With respect to thespatial distribution, sandstorms hit preferably dry and warm regions. There are some relations between ENSO activities andthe sandstorm frequency. The sandstorm rate was relatively higher in most of the El Niño years, and in most of the La Niña years the rate was relatively lower.     

SIMULATED IMPACTS OF EL NINO/SOUTHERN OSCILLATION ON UNITED STATES WATER RESOURCES1

ABSTRACT: The El Nino/Southern Oscillation (ENSO) phenomena alter global weather patterns with consequences for fresh water supply. ENSO events impact regions and their natural resource sectors around the globe. For example, in 1997 and 1998, a strong El Nino brought warm ocean temperatures, flooding, and record snowfall to the west coast of the United States. Research on ENSO events has improved long range climate predictions, affording the potential to reduce the damage and economic cost of these weather patterns. Here, using the Hydrologic Unit Model for the United States (HUMUS), we simulate the impacts of four types of ENSO states (Neutral, El Niño, La Niña, and strong El Niño) on water resources in the conterminous United States. The simulations show that La Niña conditions increase water yield across much of the country. We find that water yield increases during El Niño years across the south while declining in much of the rest of the country. However, under strong El Niño conditions, regional water yields are much higher than Neutral, especially along the West Coast. Strong El Niño is not simply an amplification of El Niño; it leads to strikingly different patterns of water resource response.     

一种大气CO2源汇反演模式方法的建立及应用

在一个二维全球大气化学传输模式的基础上,通过对模式的修改和调整,建立了一个简单二维扩散、传输模式,用于CO2源汇的反演研究.在验证了模式的有效性之后,将其应用于大气CO2源汇分布的研究.大气CO2的源主要集中在赤道地区和北半球中高纬度地区.其中,海洋和陆地生态系统(热带雨林的破坏)是赤道地区的主要碳源;北半球中高纬度的陆地生态系统是重要的碳汇,而南半球中纬度地区则表现为CO2的弱汇.对El Nino年(1982年)和其他年份的碳源汇分布情况作了比较,两者之间存在显著的差异,由于化石燃料燃烧排放并无明显波动,因此认为碳通量的年际变化是由于El Nino事件对陆地和海洋碳循环产生影响而造成的.     

基于SPEI的西南地区近53 a干旱时空特征分析

论文基于标准化降水蒸散指数（SPEI）,统计分析西南地区128 个测站1960-2012 年的气象数据,从干旱年际变化趋势、四季变化趋势、干旱强度、干旱事件频次、干旱频率以及与ENSO的关系,对西南地区近半个世纪的干旱时空特征进行了分析。结果表明：①西南地区及子区域近53 a 来呈干旱化趋势,21 世纪初干旱发生最频繁,干旱强度、极端干旱及中等干旱的频次均呈增加趋势;②四季大部分区域呈干旱化趋势,以秋季最为突出;③春季,干旱发生频率最高且集中在横断山地、四川盆地东部和云贵高原中部,夏季,横断山地北部、若尔盖高原和广西丘陵西北部易发生干旱,秋季,云贵高原、广西丘陵及四川盆地部分区域干旱频率较高,冬季,干旱易发区集中在若尔盖高原、四川盆地西南部一线;④各区域四季的干旱指数与ENSO指数相关性不同,并且ENSO事件强度与四川盆地和横断山地的SPEI 在年变化趋势方面存在明显负相关,与其他区域呈正相关。此外,西南地区在厄尔尼诺年和拉尼娜年都会出现干旱,但前者爆发干旱灾害的概率比后者高。而且各区域存在差异,四川盆地、若尔盖高原在厄尔尼诺年易发生干旱,而云贵高原在拉尼娜年发生频率较高,广西丘陵、横断山地没有明显规律和特征。     

广西秋季异常干旱的气候背景及其成因

用多种方法对近45年来广西秋季降水的异常变化特征及其气候背景进行了分析,并以此为基础,讨论了广西秋季异常干旱的形成原因及其影响因子.研究表明:秋季大陆副高强度偏强是导致广西秋季异常干旱的重要原因;广西秋季降水存在着年代际和年际两个显著振荡周期;以ENSO事件为代表的赤道太平洋地区热力振荡和太阳活动的周期性变化是这两种振荡的重要影响因子.