The second most disastrous windstorm of the nineteenth century in the Czech Lands, 26-27 October 1870

Theoretical and Applied Climatology - One of the most disastrous windstorms to take place over the Czech Lands occurred on the night of 26/27 October 1870. It is here analysed through the use of...     

Desertification in Northern Sinai in the eighteenth century

Several natural and anthropogenic phenomena in the northern Sinai sand sea and the northern Negev desert were caused by desiccation of the area during most of the 17^th and the 18^th century. The dry phase had been preceded by a wet period. It appears that the combination of several wet decades followed by a long period of desiccation was the cause of desertification processes in the area which then triggered the destruction of vegetation.There is some congruity between the wet period and the period of maximum sunspot activity, known as theMedieval Maximum, while the desiccation of the area which followed coincided approximately with the period of minimum solar activity, known as theMaunder Minimum.     

Long-term variability of temperature and precipitation in the Czech Lands: an attribution analysis

Among the key problems associated with the study of climate variability and its evolution are identification of the factors responsible for observed changes and quantification of their effects. Here, correlation and regression analysis are employed to detect the imprints of selected natural forcings (solar and volcanic activity) and anthropogenic influences (amounts of greenhouse gases—GHGs—and atmospheric aerosols), as well as prominent climatic oscillations (Southern Oscillation—SO, North Atlantic Oscillation—NAO, Atlantic Multidecadal Oscillation—AMO) in the Czech annual and monthly temperature and precipitation series for the 1866–2010 period. We show that the long-term evolution of Czech temperature change is dominated by the influence of an increasing concentration of anthropogenic GHGs (explaining most of the observed warming), combined with substantially lower, and generally statistically insignificant, contributions from the sulphate aerosols (mild cooling) and variations in solar activity (mild warming), but with no distinct imprint from major volcanic eruptions. A significant portion of the observed short-term temperature variability can be linked to the influence of NAO. The contributions from SO and AMO are substantially weaker in magnitude. Aside from NAO, no major influence from the explanatory variables was found in the precipitation series. Nonlinear forms of regression were used to test for nonlinear interactions between the predictors and temperature/precipitation; the nonlinearities disclosed were, however, very weak, or not detectable at all. In addition to the outcomes of the attribution analysis for the Czech series, results for European and global land temperatures are also shown and discussed.     

The reconstruction of eighteenth century temperature records through the use of content analysis

The reconstruction of a temperature record for eighteenth century eastern Massachusetts is discussed. In addition to instrumental records diaries were analyzed in order to produce temperature indices. Reliability tests demonstrate that the methodology used is capable of replicating results regardless of changes in coders or intraregional variability in language. Validity tests, comparing diary reconstructions with instrumental records for the same period, produced positive results. A compilation of all climate related data shows the decades of the 1720's, 1750's, and 1760's were cool, while the 1770's and 1790's were warm.     

Modelling climate change impacts on maize growth and development in the Czech Republic

Summary The crop growth model CERES-Maize is used to estimate the direct (through enhanced fertilisation effect of ambient CO₂) and indirect (through changed climate conditions) effects of increased concentration of atmospheric CO₂ on maize yields. The analysis is based on multi-year crop model simulations run with daily weather series obtained alternatively by a direct modification of observed weather series and by a stochastic weather generator. The crop model is run in two settings: stressed yields are simulated in water and nutrient limited conditions, potential yields in water and nutrient unlimited conditions. The climate change scenario was constructed using the output from the ECHAM3/T42 model (temperature), regression relationships between temperature and solar radiation, and an expert judgement (precipitation). Results: (i) After omitting the two most extreme misfits, the standard error between the observed and modelled yields is 11%. (ii) The direct effect of doubled CO₂: The stressed yields would increase by 36–41% in the present climate and by 61–66% in the 2 × CO₂ climate. The potential yields would increase only by 9–10% as the improved water use efficiency does not apply. (iii) The indirect effect of doubled CO₂: The stressed yields would decrease by 27–29% (14–16%) at present (doubled) ambient CO₂ concentration. The increased temperature shortens the phenological phases and does not allow for the optimal development of the crop. The simultaneous decrease of precipitation and increase of temperature and solar radiation deepen the water stress, thereby reducing the yields. The reduction of the potential yields is significantly smaller as the effect of the increased water stress does not apply. (iv) If both direct and indirect effects of doubled CO₂ are considered, the stressed yields should increase by 17–18%, and the potential yields by 5–14%. (v) The decrease of the stressed yields due to the indirect effect may be reduced by applying earlier planting dates. Received March 9, 2001 Revised September 25, 2001     

Tree-ring based hydroclimate reconstruction over northern Vietnam from Fokienia hodginsii: eighteenth century mega-drought and tropical Pacific influence

We present here the first statistically calibrated and verified tree-ring reconstruction of climate from continental Southeast Asia. The reconstructed variable is March–May (MAM) Palmer Drought Severity Index (PDSI) based on ring widths from 22 trees (42 radial cores) of rare and long-lived conifer, Fokienia hodginsii (Po Mu as locally called) from northern Vietnam. This is the first published tree ring chronology from Vietnam as well as the first for this species. Spanning 535 years, this is the longest cross-dated tree-ring series yet produced from continental Southeast Asia. Response analysis revealed that the annual growth of Fokienia at this site was mostly governed by soil moisture in the pre-monsoon season. The reconstruction passed the calibration-verification tests commonly used in dendroclimatology, and revealed two prominent periods of drought in the mid-eighteenth and late-nineteenth centuries. The former lasted nearly 30 years and was concurrent with a similar drought over northwestern Thailand inferred from teak rings, suggesting a “mega-drought” extending across Indochina in the eighteenth century. Both of our reconstructed droughts are consistent with the periods of warm sea surface temperature (SST) anomalies in the tropical Pacific. Spatial correlation analyses with global SST indicated that ENSO-like anomalies might play a role in modulating droughts over the region, with El Niño (warm) phases resulting in reduced rainfall. However, significant correlation was also seen with SST over the Indian Ocean and the north Pacific, suggesting that ENSO is not the only factor affecting the climate of the area. Spectral analyses revealed significant peaks in the range of 53.9–78.8 years as well as in the ENSO-variability range of 2.0 to 3.2 years.     

冬季北极涛动对西伯利亚高压、东亚冬季风以及海冰范围的可能影响

利用NCEP／NCAR月平均再分析资料（1958－1997），月平均海表面温度资料（1950－1992）以及月的海冰密集度资料（1953－1995），研究了冬季北极涛动与西伯利亚高压、东亚冬季风以及巴伦支海海冰范围之间的联系。研究结果表明，冬季北极涛动不仅影响北极和北大西洋区域气候变化，并且可能影响冬季西伯利亚高压，进而影响东亚冬季风。当冬季北极涛动处于正位相时，冬季西伯利亚高压和东亚冬季风都偏弱，在西伯利亚南部和东亚沿岸，包括中国东部、韩国和日本，从地表面到对流层中部气温偏高0.5-2℃。当冬季北极涛动处于负位相时，结果正相反。研究结果还表明，冬季西伯利亚高压对北极以及北大西洋区域气候变化没有显的影响，与北极涛动的影响相比，西伯利亚的影响强度和范围明显偏弱。研究进一步揭示了冬季北极涛动可能影响西伯利亚高压的可能机理。冬季西伯利亚高压与动力过程以及从地表面到对流层中部的气温变化有密切的关系。西伯利亚高压的西部变化主要依赖于动力过程，而其东部与气温变化更为密切。冬季西伯利亚高压的维持主要依赖于对流层中的下沉气流，这种下沉气流源于北大西洋区域，其变化受到北极涛动的影响。当冬季北极涛动处于正（负）位相时，气流的下沉运动明显减弱（增强），进而影响冬季西伯利亚高压。此处，冬季北极涛动对同时期的巴伦支海海冰范围有显的影响。     

Systemic impacts of climate change on an eroding coastal region over the twenty-first century

A numerical model detailing the functioning and emergent behaviour of an eroding coastal system is described. Model output from a 50-km study region centred on the soft-rock shore of northeast Norfolk was verified through comparison with cliff recession rates that were extracted from historical maps spanning more than a century. Predictions were then made for the period 2000 to 2100 under combined climatic change and management scenarios. For the scenarios evaluated, the model was relatively insensitive to increases in offshore wave height and moderately sensitive to changes in wave direction, but the most important effects were associated with accelerated sea-level rise (SLR). In contrast to predictions made using a modified version of the Bruun rule, the systems model predicted rather complex responses to SLR. For instance, on some sectors of coast, whereas the Bruun rule predicted increased recession under accelerated SLR, the systems model actually predicted progradation owing to the delivery of sediment from eroding coasts up-drift. By contrast, on coasts where beaches are underlain by shore platforms, both the Bruun rule and the systems model predicted accelerated recession rates. However, explicit consideration of the interaction between beach and shore platform within the systems model indicates that these coasts have a broader range of responses and lower overall vulnerability to SLR than predicted by the Bruun rule.     

Implications of twenty-first century climate change on Northeastern United States maple syrup production: impacts and adaptations

Previous research on the impacts of maple syrup production in the Northeastern United States has been based on correlative relationships between syrup production and average temperature. Here a simple biologically and physically-based model of sapflow potential is used to assess observed changes in sapflow across the Northeastern US from 1980 to 2006; document the correspondence between these observations and independent downscaled atmosphere ocean general circulation model (AOGCM) simulations of conditions during this period; and quantify changes in sapflow potential through 2100. The sapflow model is able to capture the spatial and temporal (in terms of the start date of sapflow) variations of sapflow that are observed across the Northeast. Likewise the AOGCM simulations reflect the mean number of sapflow days and the timing of sapflow during the 1980–2006 overlap period. Through the twenty-first century, warming winter temperatures will result in a decline in the number of sapflow days if traditional sap collection schedules are maintained. Under the A1fi emissions scenario the number of sapflow days decreases by up to 14 days. However, the changes in climate also translate the optimal timing of sap collection to earlier in the year. Across the region, the time period that maximizes the number of sapflows days becomes as much as 30 days earlier by 2100 under the A1fi emissions scenario. Provided this change is accounted for by modifying the start of the traditional sap collection schedule, there is essentially no net loss of sapflow days across the majority of the region, with a net increase of sapflow days indicated in the extreme north.     

Unprecedented low twentieth century winter sea ice extent in the Western Nordic Seas since A.D. 1200

We reconstructed decadal to centennial variability of maximum sea ice extent in the Western Nordic Seas for A.D. 1200–1997 using a combination of a regional tree-ring chronology from the timberline area in Fennoscandia and δ¹⁸O from the Lomonosovfonna ice core in Svalbard. The reconstruction successfully explained 59% of the variance in sea ice extent based on the calibration period 1864–1997. The significance of the reconstruction statistics (reduction of error, coefficient of efficiency) is computed for the first time against a realistic noise background. The twentieth century sustained the lowest sea ice extent values since A.D. 1200: low sea ice extent also occurred before (mid-seventeenth and mid-eighteenth centuries, early fifteenth and late thirteenth centuries), but these periods were in no case as persistent as in the twentieth century. Largest sea ice extent values occurred from the seventeenth to the nineteenth centuries, during the Little Ice Age (LIA), with relatively smaller sea ice-covered area during the sixteenth century. Moderate sea ice extent occurred during thirteenth–fifteenth centuries. Reconstructed sea ice extent variability is dominated by decadal oscillations, frequently associated with decadal components of the North Atlantic Oscillation/Arctic Oscillation (NAO/AO), and multi-decadal lower frequency oscillations operating at ~50–120 year. Sea ice extent and NAO showed a non-stationary relationship during the observational period. The present low sea ice extent is unique over the last 800 years, and results from a decline started in late-nineteenth century after the LIA.     

Drought in the Southern United States over the 20th century: variability and its impacts on terrestrial ecosystem productivity and carbon storage

Drought is one of the most devastating natural hazards faced by the Southern United States (SUS). Drought events and their adverse impacts on the economy, society and environment have been extensively reported during 1895?C2007. Our aim is thus to characterize drought conditions in the SUS and explore the impacts on terrestrial ecosystem function (i.e., net primary productivity (NPP) and net carbon exchange (NCE)). Standard precipitation index (SPI) was used to characterize drought intensity and duration, and a process-based ecosystem model was used to explore the relationship between drought and ecosystem function. Combining overall information on growing-season SPI, drought area and duration, we concluded there was no significant change in drought conditions for the SUS during 1895?C2007. However, increased drought intensity was found for many areas in the east, resulting in significant decreases in NPP for these areas, with the largest decrease up to 40% during extreme droughts. Changes in precipitation patterns increased C emissions of 0.16 Pg (1 Pg?=?10¹⁵?g) in the SUS during 1895?C2007. The west (dry region) acted as a C sink due to increased precipitation, while the east (water-rich region) acted as a C source due to increased drought intensity. Both NPP and NCE significantly increased along a gradient of declining drought intensity. Changes in precipitation resulted in C sources in forest, wetland, and cropland ecosystems, while C sinks in shrubland and grassland ecosystems. Changes in air temperature could either enhance or reduce drought impacts on NPP and NCE across different vegetation types.     

重庆“5.6”强风雹天气过程成因分析

利用常规观测、NCEP分析场及雷达、自动站等资料对重庆＂5.6＂强风雹天气的成因进行了分析,结果表明：冷锋和副热带高空急流在风雹发生地近乎重叠的配置结构促进了次级环流的形成并有利于上升运动的强烈发展;风暴天气发生前,下垫面强烈加热、低层增温增湿、中高层干冷对大气对流不稳定性增强的作用显著;对流有效位能（CAPE）、K指数、SI指数高值区边缘的强指数梯度区、对流抑制（CIN）的小值区以及较强的垂直风切变对大风冰雹的预报有重要的指示意义;雷达回波显示多单体风暴具有三体散射、弱回波区等冰雹回波特征,中层径向辐合和反射率因子核心的反复上升下降也是形成地面大风和冰雹的重要特征;四川盆地东部东北西南向山脉对冷空气的移动有阻挡作用,山脉之间的槽状地形为多单体风暴的持续发展保留了较大的空间,明月山南麓的地形起到了强迫抬升和触发的作用,由于地形的阻挡形成狭管效应,加强了下击暴流形成的地面大风,是形成11级大风的重要因素。     

Declining summer snowfall in the Arctic: causes, impacts and feedbacks

Recent changes in the Arctic hydrological cycle are explored using in situ observations and an improved atmospheric reanalysis data set, ERA-Interim. We document a pronounced decline in summer snowfall over the Arctic Ocean and Canadian Archipelago. The snowfall decline is diagnosed as being almost entirely caused by changes in precipitation form (snow turning to rain) with very little influence of decreases in total precipitation. The proportion of precipitation falling as snow has decreased as a result of lower-atmospheric warming. Statistically, over 99% of the summer snowfall decline is linked to Arctic warming over the past two decades. Based on the reanalysis snowfall data over the ice-covered Arctic Ocean, we derive an estimate for the amount of snow-covered ice. It is estimated that the area of snow-covered ice, and the proportion of sea ice covered by snow, have decreased significantly. We perform a series of sensitivity experiments in which inter-annual changes in snow-covered ice are either unaccounted for, or are parameterized. In the parameterized case, the loss of snow-on-ice results in a substantial decrease in the surface albedo over the Arctic Ocean, that is of comparable magnitude to the decrease in albedo due to the decline in sea ice cover. Accordingly, the solar input to the Arctic Ocean is increased, causing additional surface ice melt. We conclude that the decline in summer snowfall has likely contributed to the thinning of sea ice over recent decades. The results presented provide support for the existence of a positive feedback in association with warming-induced reductions in summer snowfall.     

Simulation of Turbulent Flow in An Urban Forested Park Damaged by a Windstorm

The damage caused by windstorms to forest ecosystems is often very heterogeneous. In order to improve the stability of forested landscapes, it is of great importance to identify the factors responsible for this spatial variability. The structure of the landscape itself may play a role, through possible influences of canopy heterogeneities on the development of turbulence. For the purpose of investigating the role of landscape fragmentation on turbulence development, we used a numerical flow model with a k–ε turbulence scheme model, previously validated in simple cases with well-defined surface changes (roughness change and forest edge flow). A series of two- and three-dimensional simulations were performed over a heterogeneous urban forested park in Europe, which was severely damaged in various places by the Lothar windstorm in December 1999. The model shows the development of a region of strong turbulence, resulting from the generation of large wind shear at the top of the canopy. A sensitivity study shows how the location, extension and intensity of the region depend on canopy characteristics such as the leaf density, the nature of the edge or the presence of gaps and clearings. Simulations performed in conditions representative of the windstorm show that the location of the damaged areas corresponds very closely to the regions where the turbulent kinetic energy was above a certain threshold.     

Climate change in the Tahoe basin: regional trends, impacts and drivers

The purpose of this study was to quantify the decadal-scale time trends in air temperature, precipitation phase and intensity, spring snowmelt timing, and lake temperature in the Tahoe basin, and to relate the trends to large-scale regional climatic trends in the western USA. Temperature data for six long-term weather stations in the Tahoe region were analyzed for trends in annual and monthly means of maximum and minimum daily temperature. Precipitation data at Tahoe City were analyzed for trends in phase (rain versus snow), decadal standard deviation, and intensity of rainfall. Daily streamflow data for nine gaging stations in and around the Tahoe basin were examined for trends in snowmelt timing, by two methods, and an existing record for the temperature of Lake Tahoe was updated. The results for the Tahoe basin, which contrast somewhat with the surrounding region, indicate strong upward trends in air temperature, a shift from snow to rain, a shift in snowmelt timing to earlier dates, increased rainfall intensity, increased interannual variability, and continued increase in the temperature of Lake Tahoe. Two hypotheses are suggested that may explain why the basin could be warming faster than surrounding regions. Continued warming in the Tahoe basin has important implications for efforts to manage biodiversity and maintain clarity of the lake.     

气候变化与海洋生态系统：影响、适应和脆弱性——IPCC AR6 WGⅡ报告之解读

IPCC第六次评估报告(AR6)第二工作组报告第三章开展了气候变化对海洋的影响和风险,以及生态系统及其服务功能、脆弱性和适应评估。AR6明确指出,人为气候变化已经并将继续显著地改变全球和区域海洋的气候影响驱动因子,包括海温升高、海平面上升、海洋酸化和缺氧,以及营养盐浓度变化等海洋物理和化学因子。例如,20世纪80年代以来全球海洋热浪发生的频率已增加了1倍,到21世纪末期可能增加4～8倍。气候影响驱动因子的变化已经对海洋和海岸带生态系统造成了广泛而深远的影响:1)海洋变暖使得海洋物种自1950年代以来以(59.2±15.5) km/(10 a)的速率向极地方向迁移,导致热带海域生物量减少,中纬度海区热带化,极地和亚极地海区浮游植物生长期提前;2)频繁发生的海洋热浪事件已经接近甚至超过了某些海洋生物的耐受极限或其气候临界点,如暖水珊瑚的大规模白化、死亡,海草和大型海藻的大面积消失;3)海洋变暖、缺氧和酸化使得河口区生物群落结构改变,赤潮等有害藻华事件频发,近海和大洋浮游植物生物量和初级生产力下降;4)海平面上升导致海岸带红树林、盐沼和海草床等生态系统的退化;5)未来全球海洋生态系统面临的风险将不断加剧,尤其是在热带和北冰洋海区。其中,当全球升温1.5℃时(最快到21世纪40年代,SSP5-8.5情景),暖水珊瑚礁预计将减少70％～90％;当升温2℃时,几乎所有的(>99％)暖水珊瑚礁将会消失。目前人类社会采取的一些措施(如建立海洋保护区和红树林生态修复)已越来越不能应对日益增长的气候风险,迫切需要发展变革性的行动措施,推动海洋生态系统恢复力的发展,并需尽快采取强有力的减排措施以减缓全球变暖的影响。     

Identifying stakeholder-relevant climate change impacts: A case study in the Yakima River Basin,Washington, USA

Designing climate-related research so that study results will be useful to natural resource managers is a unique challenge. While decision makers increasingly recognize the need to consider climate change in their resource management plans, and climate scientists recognize the importance of providing locally-relevant climate data and projections, there often remains a gap between management needs and the information that is available or is being collected. We used decision analysis concepts to bring decision-maker and stakeholder perspectives into the applied research planning process. In 2009 we initiated a series of studies on the impacts of climate change in the Yakima River Basin (YRB) with a four-day stakeholder workshop, bringing together managers, stakeholders, and scientists to develop an integrated conceptual model of climate change and climate change impacts in the YRB. The conceptual model development highlighted areas of uncertainty that limit the understanding of the potential impacts of climate change and decision alternatives by those who will be most directly affected by those changes, and pointed to areas where additional study and engagement of stakeholders would be beneficial. The workshop and resulting conceptual model highlighted the importance of numerous different outcomes to stakeholders in the basin, including social and economic outcomes that go beyond the physical and biological outcomes typically reported in climate impacts studies. Subsequent studies addressed several of those areas of uncertainty, including changes in water temperatures, habitat quality, and bioenergetics of salmonid populations.     

The local impacts of climate change in the Ferlo, Western Sahel

Recent increases in the accuracy of climate models have enhanced the possibilities for analyzing the impacts of climate change on society. This paper explores how the local, economic impacts of climate change can be modeled for a specific eco-region, the Western Sahel. The people in the Sahel are highly dependent on their natural resource base, and these resources are highly vulnerable to climate change, in particular to changes in rainfall. Climate models project substantial changes in rainfall in the Sahel in the coming 50 years, with most models predicting a reduction in rainfall. To connect climate change to changes in ecosystem productivity and local income, we construct an ecological–economic model that incorporates rangeland dynamics, grazing and livestock prices. The model shows that decreased rainfall in the Sahel will considerably reduce local incomes, in particular if combined with increases in rainfall variability. Adaptation to these climate change projections is possible if reductions in rainfall are followed by destocking to reach efficient grazing levels. However, while such a strategy is optimal from the perspective of society, the stocking rate is determined by individual pastoralists that face few incentives to destock.