Effects of climatic change and climatic variability on the Thornthwaite moisture index in the Delaware River basin

The Thornthwaite moisture index is useful as an indicator of the supply of water in an area relative to the demand under prevailing climatic conditions. This study examines the effects of long-term changes in climate (temperature and precipitation) on the Thornthwaite moisture index in the Delaware River basin. Temperature and precipitation estimates for doubled-CO₂ conditions derived from three general circulation models (GCMs) are used to study the response of the moisture index for steady-state doubled-CO₂ conditions and for gradual changes from present to doubled-CO₂ conditions.Results of the study indicate that temperature and precipitation under doubled-CO₂ conditions will cause the Thornthwaite moisture index to decrease, implying significantly drier conditions in the Delaware River basin than currently exist. The amount of decrease depends, however, on the GCM climatic-change scenario used. The results also indicate that future changes in the moisture index will be partly masked by natural year-to-year variability in temperature and precipitation.     

Extreme climatic events in the Amazon basin

During 2009 the Amazon basin was hit by a heavy flooding with a magnitude and duration few times observed in several decades. Torrential rain in northern and eastern Amazonia during the austral summer of 2008–2009 swelled the Amazon River and its tributaries. By July 2009, water levels of the Rio Negro, a major Amazon tributary, reached at Manaus harbor a new record, the highest mark of the last 107?years. During the 2008–2009 hydrological year, the rainy season on northern and northwestern Amazonia started prematurely, and was followed by a longer-than-normal rainy season. An anomalously southward migration of the ITCZ during May–June 2009, due to the warmer than normal surface waters in the tropical South Atlantic, was responsible for abundant rainfall in large regions of eastern Amazonia and Northeast Brazil from May to July 2009. We also compared the flood of 2009 with other major events recorded in 1989 and 1999. The hydrological consequences of this pattern were earlier than normal floods in Amazon northern tributaries, which peak discharges at their confluences with the main stem almost coincided with the peaks of southern tributaries. Since the time displacement of the contribution to the main stem of northern and southern Amazon tributaries is fundamental for damping flood waves in the main stem, the simultaneous combinations of peak discharges of tributaries resulted in an extreme flood.     

Impact of recent climatic change on growth of low elevation eastern Mediterranean forest trees

Evidence is presented of how Pinus halepensis Miller from dry habitats at <300 m elevation of four Greek island regions have responded to climatic conditions of the last two centuries. We compared historical periods of low growth due to low precipitation with the recent period of significant precipitation decline. In all cases trees?? growth patterns across the twentieth century were consistent with trends in annual (rather than seasonal) precipitation, with lowest values in both precipitation and radial growth during the last two decades of the twentieth century, the worst conditions for tree growth in more than 200 years. The data are compared with trends across different vegetation belts of the northern Mediterranean basin. Drought related tree mortality in Greece in 2000 and 2007 coincided with the most severe fire outbreaks on record. IPCC WG I (2007) climate scenarios for the Mediterranean suggest a further decline in precipitation, particularly in the eastern regions. Should this occur, growth reduction in trees, tree mortality and damage from forest fires are likely to become more severe.     

Potential effects of climatic change on the distribution of Tetraclinis articulata, an endemic tree from arid Mediterranean ecosystems

South-eastern Spain is a key area for assessing the effects of climate change on biodiversity since it presents an ecotone between the Mediterranean biome and the subtropical shrublands of arid lands. The forests of Tetraclinis articulata constitutes an especially relevant case. A species distribution model has been developed, regionalised climate change scenarios for South-eastern Spain were generated and expected changes in the suitability area of this species were estimated under B2 and A2 SRES scenarios for the time slice 2020–2050. Moreover, land use in the present and future potential habitat has been analysed. The high sensitivity of T. articulata is expressed not only as effects of climate change in the near future when compared to the present-day situation but also in the remarkable differences under scenarios B2 and A2. Under scenario B2 the suitable area for T. articulata would expand six-fold whereas under A2 the potential habitat would disappear from its present-day distribution and would move to a small area in the interior mountains. Under scenario B2 the future potential habitat in the coastal location would include enough area of shrublands, the main effective habitat of the species. Moreover, the present and future potential habitat partially overlaps, which facilitates the species migration. On the contrary, in the interior potential habitat the land use is less favourable for the effective habitat, the actual and future potential habitat do not overlap and the low dispersal capabilities of the species prevents natural migration to the interior to be expected.     

Solar signals in global climatic change

Based on the physical background that varying solar activity should lead to variations of the ‘solar constant’ and that the climate system may respond sensitively even to small solar variations, a correlation analysis is performed where hemispheric and global averages of the annual mean surface air temperature are compared with the variations of a variety of solar forcing parameters: sunspots, related hypotheses including variations of the quasi-eleven-year solar cycle length, solar diameter variations and gravitational effects. This analysis is based on the 1881–1988 period, for the northern hemisphere including proxy data 1671–1988. Cross correlations and correlations moving in time reveal some instability effects which are hard to interpret. The temperature variance components which may be hypothetically explained by solar forcing are small. Similarly, a seasonal and regional signal and signal-to-noise analysis based on a gridded temperature time series 1890–1985 reveals small signals which do not exceed roughly 1.5 K in the arctic winter (maximum) or 0.2-0.3 K on a global average.     

Rapid climatic change and the deep ocean

A simple transient two-dimensional (latitude-depth) upwelling-diffusion ocean model coupled with an energy balance climate model is used to determine the surface temperature response to changes in the deep water formation rate. The changes in surface temperature are large and rapid with a large magnification at high latitudes, suggesting that rapid climate changes during the Glacial-Holocene transition could have been the result of variations in the rate of deep water formation. If this is true, the mechanism is essentially transient in nature and cannot be predicted using steady state models.     

近50a贵州气候变化分析

利用贵州省15个代表站1951～2000年的温度、降水资料,通过计算气候趋势系数、30a滑动平均和29a滑动均方差,研究了贵州各季及年平均温度、降水的长期变化趋势及气候基本态的变化特征和气候变率的长期变化,并用蒙特卡洛显著性检验方法对温度、降水的长期变化进行统计检验.研究指出近50a来贵州除春季降水显著减少外,各季及年平均温度、降水变化均不明显,属于自然振动.     

Modelling geomorphic response to climatic change

This paper develops a three-step thaw model to assess the impact of predicted warming on an ice-rich polar desert landscape in the Canadian high Arctic. Air temperatures are established for two climate scenarios, showing mean annual increases of 4.9 and 6.5°C. This leads to a lengthening of the summer thaw season by up to 26 days and increased thaw depths of 12–70 cm, depending on the thermal properties of the soil. Subsidence of the ground surface is the primary landscape response to warming and is shown to be a function of the amount and type of ground ice in various cryostratigraphic units. In areas of pore ice and thin ice lenses with a low density of ice wedges, subsidence may be as much as 32 cm. In areas with a high density of ice wedges, subsidence will be slightly higher at 34 cm. Where massive ice is present, subsidence will be greater than 1 m. Landscape response to new climate conditions can take up to 15 years, and may be as long as 50 years in certain cases.     

中国近50a气候变化复杂性分析

分析了我国气温和降水量变化的兰帕尔－齐夫复杂度空间分布特征，结果表明，平均而言，我国平均气温和降水量变化的复杂度约为10－11，小于随机序列的复杂度13，年平衡气温变化序列的复杂度最小，秋季平均气温变化序列的复杂度最大，季节和年平均气温序列的复杂度小于月平均气温变化序列的复杂度，月总降水量变化序列的复杂度为西部，北部大于南部和东部，我国东南沿海地区气候要素变化的复杂度最大。     

气候突变的定义和检测方法

气候突变现象及其理论的研究是近代气候学一个新兴的研究领域.本文是气候突变研究评述的第一部分,着重讨论了突变,主要是气候突变的定义和气候突变信号的各种检测方法.把气候突变归纳为四类,即均值突变、变率突变、转折突变和翘翘板(seasaw)突变.并通过Mann-Kendall法的检测,发现在本世纪20年代经历了一次全球范围的气候突变.     

气候变迁研究现状的几个问题

气候变迁研究在近几年有很大的发展,现在它已不只是一个学术问题,而是一个具有重要现实意义的科学课题了。随着社会生产的发展,编制长期发展规划和设计重大工程都需要参考过去和未来的气候情况。其目的不仅是为了预防气候灾害,而且也要求对今后气候资源有所估计,以便开发利用。我国农业学大寨运动蓬勃开展以来,很多地方迅速     

Assessing the sensitivity of Canada's ecosystems to climatic change

Global warming due to increased concentrations of atmospheric CO₂ is expected to be amplified in middle and higher latitudes. Consequently, ecosystems in these latitudes will experience more pronounced climatic variations. This investigation attempts to assess the sensitivity of Canada's ecosystems to climatic change. Potential ecological impacts resulting from global warming are outlined. With this background, the effects of a doubled CO₂ climate are applied to a classification model derived from the current ecological setting. Results reveal not only major shifts in ecological boundaries but also changes in the character of these broadly distributed ecosystems.     

Assessing the impact of climatic change on food production

Attempts to assess the impact of a hypothetical climatic change on food production have relied on the use of statistical models which predict crop yields using various climatic variables. It is emphasized that the coefficients of these models are not universal constants, but rather statistical estimates subject to several sources of error. Thus, any statement regarding the estimated impact of climatic change on food production must be qualified appropriately.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

贵州气候变化的科学事实

介绍了中国气候变化及贵州气候变化的主要特征,提出了贵州气候变化的科学事实及贵州应对气候变化需要关注的5个问题.     

Sensitivity of agricultural production to climatic change

Although the range of cultivated species is relatively restricted, domestic plants and animals exhibit considerable resilience to stochastic shocks, and the study of their ecological adaptability and critical physiological and phenological requirements is a valuable first step in determining their possible response to climatic change. Methods of assessing agroclimatic suitability and their limitations are discussed, and suggestions are made for simulating the probable impact of shifts in the main climatic parameters on the productivity and spatial distribution of key crops and livestock. Some regions and crops are climatically more vulnerable than others: some regions (in particular North America) are strategically more critical to the stability of world food supplies, while in others resources for agricultural production are under more severe pressure.As well as attempts to forecast long-term climatic trends and their effects on agriculture, combating climatic variability merits high priority. This is an ever-present source of instability in production and could be enhanced in association with changing climate. Its magnitude differs widely among crops and geographical regions, but its impact from year to year is often greater than that predicted from climatic change even in extreme scenarios. The paper indicates a number of potentially desirable areas for action and suggests that several of these would be beneficial both as a buffer against short-term effects of variability and as a means of combating climatic change.     

Impact of climatic change on the biological production in the Barents Sea

The Barents Sea is a high latitude ecosystem and is an important nursery and feeding area for commercial fish stocks such as cod, capelin and herring. There is a large inter-annual variability both in physical and biological conditions in the Barents Sea. Understanding and predicting changes in the system requires insight into the coupled nature of the physical and biological interactions. A coupled physical and biological ocean model is used to study the impact of postulated future atmospheric changes on the physical and biological conditions in the Barents Sea. Results from this simulation not only show that there is a large variability in the physical conditions on a wide range of time scales, but also that the temperature in the Barents Sea is increasing. The corresponding ice cover decrease is most noticeable in the summer months. The changes in physical properties will most likely have an impact on the biotope. On average, the primary production increases slightly over a 65 year long period, about 8%, partly due to an increased production in the northern Barents Sea. The model further simulates that the production of Atlantic zooplankton species increases approximately 20% and becomes more abundant in the east. The Arctic zooplankton biomass decreases significantly (50%) causing the total simulated production to decrease.     

贵州省近50a降水资源的评估

介绍了国家气候中心使用的降水资源评估方法,利用贵州省32个代表站1961～2004年年降水量和历年气候灾情资料,对近50a来全省年降水资源的变化和旱涝灾害出现情况做了分析,对年降水资源进行评估.研究表明贵州年降水资源量20世纪70年代最多,90年代次之,80年代最少,其年降水资源量值低于多年平均值,但各年代总体变化不大,均在正常范围内;贵州省历年有较大干旱灾情出现的频率大于较大洪涝灾情出现频率,且20世纪90年代旱涝灾情同年出现的现象明显,主要原因①近年来各种气象灾情收集记录更详实;②虽然全年降水总量变化不明显,但极端天气出现频繁;③随着经济的发展,人类活动加剧使我贵州气象灾害的承灾能力下降.干旱洪涝对农业生产及国民经济产生的影响巨大,防汛抗旱工作形势更加严峻.     

Variations in climatic and hydrological parameters in the Selenga River basin in the Russian Federation

The variations in average annual surface air temperature, precipitation, and runoff in the Selenga River basin (within Russia) are analyzed. It is demonstrated that the considerable increase in average annual temperature of surface air layers occurred in the 1980s-1990s. The decrease in peak water discharge in the rivers and the increase in the frequency of low-water periods were revealed in the forest-steppe and steppe zones of the Selenga River basin in 2001-2010. In the southwestern mountain regions (the Dzhida River basin) the river runoff increased during that period.