Interannual and Interdecadal Variations of the Mid-Atlantic Trough and Associated American-Atlantic-Eurasian Climate Anomalies

The mid-Atlantic trough (MAT) is one of the most prominent circulation systems over the subtropical North Atlantic during the boreal summer, and it can be viewed as a bridge linking the climate in the American-Atlantic-Eurasian region. The upper-tropospheric MAT attains its maximum intensity of 200–150?hPa in June and July. An index measuring the variability of MAT intensity is defined, which reveals significant interannual and interdecadal variations of the trough.

On interannual time scales, the variation of MAT is significantly associated with the North Atlantic Oscillation, a southeastward propagating stationary wave that possibly originates from the northeastern Pacific, and the Atlantic Meridional Mode. A stronger trough is associated with warmer surface temperatures and higher pressure over central-northern North America and the extratropical North Atlantic and with colder surface temperatures and lower pressure over the Arctic, the subtropical North Atlantic, and the northeastern Pacific. In the meantime, significant negative precipitation anomalies occur over the north of the Mediterranean Sea and the Black Sea, as well as the northeastern Atlantic because of the anomalous low-level northeasterly winds over these areas. On an interdecadal time scale, the variation of MAT seems to be related to the Atlantic Multi-decadal Oscillation. Warmer surface temperatures appear over almost the entire North Atlantic, southern Europe, East Asia, and the North Pacific during the weak phase of the trough. A weak trough is also associated with the dipole pattern of anomalous precipitation over the extratropical North Atlantic, Greenland, and northeastern North America, corresponding to a dipole of low-level atmospheric circulation over these regions.     

Climate sensitivity estimated from ensemble simulations of glacial climate

The concentration of greenhouse gases (GHGs) in the atmosphere continues to rise, hence estimating the climate system’s sensitivity to changes in GHG concentration is of vital importance. Uncertainty in climate sensitivity is a main source of uncertainty in projections of future climate change. Here we present a new approach for constraining this key uncertainty by combining ensemble simulations of the last glacial maximum (LGM) with paleo-data. For this purpose we used a climate model of intermediate complexity to perform a large set of equilibrium runs for (1) pre-industrial boundary conditions, (2) doubled CO₂ concentrations, and (3) a complete set of glacial forcings (including dust and vegetation changes). Using proxy-data from the LGM at low and high latitudes we constrain the set of realistic model versions and thus climate sensitivity. We show that irrespective of uncertainties in model parameters and feedback strengths, in our model a close link exists between the simulated warming due to a doubling of CO₂, and the cooling obtained for the LGM. Our results agree with recent studies that annual mean data-constraints from present day climate prove to not rule out climate sensitivities above the widely assumed sensitivity range of 1.5–4.5°C (Houghton et al. 2001). Based on our inferred close relationship between past and future temperature evolution, our study suggests that paleo-climatic data can help to reduce uncertainty in future climate projections. Our inferred uncertainty range for climate sensitivity, constrained by paleo-data, is 1.2–4.3°C and thus almost identical to the IPCC estimate. When additionally accounting for potential structural uncertainties inferred from other models the upper limit increases by about 1°C.     

毕节地区旅游气候资源分析

通过对毕节地区相关气候指标及1978—2007年30a气象资料的分析计算,按照最适宜居住和旅游的基准指标及人体舒适程度,分析毕节地区旅游气候资源。经综合分析,毕节地区呈现清凉、舒适的居住和避暑旅游气候条件。各项气候基准指标都适宜居住和避暑旅游。     

长波区间太阳辐射对气候模拟的影响

长波区间的太阳辐射在气候模式中往往被忽略。利用国家气候中心BCC_AGCM2.0.1大气环流模式,采用矩阵算子辐射传输算法,研究了长波区间太阳辐射对气候模式辐射通量和温度模拟结果的影响。结果表明,以ISCCP和CERES辐射资料为标准,考虑长波区间太阳辐射后,长波区间晴空大气地表向下辐射通量平均误差减小2.05 W/m2,均方根误差减少1.29 W/m2;长波区间晴空大气模式顶向上辐射通量平均误差减小0.70 W/m2,均方根误差减小0.21 W/m2;长波区间有云大气地表向下辐射通量平均误差减小1.38 W/m2,均方根误差减小1.03 W/m2;长波区间有云大气模式顶向上辐射通量平均误差减小0.99 W/m2,均方根误差减小0.30 W/m2。以ECMWF再分析资料为标准,考虑长波区间太阳辐射后,赤道地区上对流层—下平流层区域温度的冷偏差得到改善,对流层顶温度平均误差减小0.27 K,均方根误差减小0.25 K。     

2022年夏季中国气候特征及主要天气气候事件

2022年夏季,中国气候总体呈现暖干特征。全国平均气温22.3℃,较常年同期偏高1.1℃,为1961年以来历史同期最高;全国平均降水量290.6 mm,较常年同期偏少12.3％,为1961年以来历史同期第2少。季内主要天气气候事件有：中国中东部地区出现1961年以来综合强度最强的高温过程,此次高温事件持续79 d,江南大部、江淮西部、江汉、四川盆地东部等地高温日数较常年同期偏多20 d以上,对电力供应和人体健康等产生不利影响;长江中下游及川渝地区出现严重夏伏旱,范围广、强度大,高温干旱叠加给农业生产、水资源、能源供保、长江通航能力等多方面带来不利影响;全国共发生19次区域性暴雨过程,珠江流域、松辽流域出现阶段性汛情;台风生成、登陆个数均较常年同期偏少,初台“暹芭”登陆强度强,对华南及江西等地造成一定经济损失,但对缓解华南高温和干旱有利。     

Climate of scepticism: US newspaper coverage of the science of climate change

This two-part study integrates a quantitative review of one year of US newspaper coverage of climate science with a qualitative, comparative analysis of media-created themes and frames using a social constructivist approach. In addition to an examination of newspaper articles, this paper includes a reflexive comparison with attendant wire stories and scientific texts. Special attention is given to articles constructed with and framed by rhetoric emphasising uncertainty, controversy, and climate scepticism.     

关中区域主要大气污染物时空分布特征分析

利用关中区域西安、咸阳、渭南、铜川、宝鸡五个主要城市2014-2018年PM2.5、PM10、SO2和NO2四种主要大气污染物逐日平均质量浓度,统计分析了关中区域近5年环境空气质量时间变化特征和区域分布特征。结果表明:关中区域颗粒物PM2.5、PM10和SO2年平均质量浓度呈逐年下降趋势;西安、咸阳和渭南NO2年平均质量浓度呈逐年上升趋势,宝鸡和铜川相对较低且变化趋势不明显;区域大气环境质量总体在不断改善。关中区域4-10月尤其是夏季6-9月空气质量状况较好,7月最好;采暖期空气污染较为严重,其中1月环境空气质量最差,其次是2月。近5年以颗粒物PM2.5和PM10为主要污染物,年平均值均超标,而SO2质量浓度相对较低;从区域分布来看,中部环境空气质量最差,其中PM2.5、PM10和NO2质量浓度明显较高,东部次之,北部和西部相对较好。咸阳中度以上污染日数明显较多,其次为西安,渭南居第三,铜川最少;咸阳、西安和渭南中度以上污染日数呈逐年增加趋势,咸阳增加趋势最为显著,而宝鸡和铜川呈逐年减少趋势。     

IPCC-AR4 climate simulations for the Southwestern US: the importance of future ENSO projections

Future climate trends for the Southwestern US, based on the climate models included in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report, project a more arid climate in the region during the 21st century. However, future climate variability associated with El Niño Southern Oscillation (ENSO)—an important driver for winter climate variability in the region—have not been addressed. In this work we evaluate future winter ENSO projections derived from two selected IPCC models, and their effect on Southwestern US climate. We first evaluate the ability of the IPCC coupled models to represent the climate of the Southwest, selecting the two models that best capture seasonal precipitation and temperature over the region and realistically represent ENSO variability (Max Planck Institute’s ECHAM5 and the UK Met Office HadCM3). Our work shows that the projected future aridity of the region will be dramatically amplified during La Niña conditions, as anomalies over a drier mean state, and will be characterized by higher temperatures (~0.5°C) and lower precipitation (~3 mm/mnt) than the projected trends. These results have important implications for water managers in the Southwest who must prepare for more intense winter aridity associated with future ENSO conditions.     

Climate variability and trends in downscaled high-resolution simulations and projections over Metropolitan France

In order to fulfill the society demand for climate information at the spatial scale allowing impact studies, long-term high-resolution climate simulations are produced, over an area covering metropolitan France. One of the major goals of this article is to investigate whether such simulations appropriately simulate the spatial and temporal variability of the current climate, using two simulation chains. These start from the global IPSL-CM4 climate model, using two regional models (LMDz and MM5) at moderate resolution (15–20 km), followed with a statistical downscaling method in order to reach a target resolution of 8 km. The statistical downscaling technique includes a non-parametric method that corrects the distribution by using high-resolution analyses over France. First the uncorrected simulations are evaluated against a set of high-resolution analyses, with a focus on temperature and precipitation. Uncorrected downscaled temperatures suffer from a cold bias that is present in the global model as well. Precipitations biases have a season- and model-dependent behavior. Dynamical models overestimate rainfall but with different patterns and amplitude, but both have underestimations in the South-Eastern area (Cevennes mountains) in winter. A variance decomposition shows that uncorrected simulations fairly well capture observed variances from inter-annual to high-frequency intra-seasonal time scales. After correction, distributions match with analyses by construction, but it is shown that spatial coherence, persistence properties of warm, cold and dry episodes also match to a certain extent. Another aim of the article is to describe the changes for future climate obtained using these simulations under Scenario A1B. Results are presented on the changes between current and mid-term future (2021–2050) averages and variability over France. Interestingly, even though the same global climate model is used at the boundaries, regional climate change responses from the two models significantly differ.     

Climate change, ambient ozone, and health in 50 US cities

We investigated how climate change could affect ambient ozone concentrations and the subsequent human health impacts. Hourly concentrations were estimated for 50 eastern US cities for five representative summers each in the 1990s and 2050s, reflecting current and projected future climates, respectively. Estimates of future concentrations were based on the IPCC A2 scenario using global climate, regional climate, and regional air quality models. This work does not explore the effects of future changes in anthropogenic emissions, but isolates the impact of altered climate on ozone and health. The cities’ ozone levels are estimated to increase under predicted future climatic conditions, with the largest increases in cities with present-day high pollution. On average across the 50 cities, the summertime daily 1-h maximum increased 4.8 ppb, with the largest increase at 9.6 ppb. The average number of days/summer exceeding the 8-h regulatory standard increased 68%. Elevated ozone levels correspond to approximately a 0.11% to 0.27% increase in daily total mortality. While actual future ozone concentrations depend on climate and other influences such as changes in emissions of anthropogenic precursors, the results presented here indicate that with other factors constant, climate change could detrimentally affect air quality and thereby harm human health.     

Climate of the Black Sea region around 0 C.E.

Indications of the climate of the Black Sea Region (the region up to about 500 km from the sea) are examined for a period of a few hundred years before and after 0 C.E. Much of the information is obtained from the work of Soviet scientists, some recent discovery regarding ice conditions on a high mountain of Turkey and from archeology of the region.Levels of the Black Sea, the Caspian and that of the large Lake Van were on the rise at the time. The most plausible cause for the level rise of the latter two exitless water bodies is increased precipitation and inflow from the drainage areas; in the Black Sea's case a contributory factor must have been the level rise of the world's oceans. Pollen investigations in the southern European Soviet Union, as well as the large quantities of wine and figs grown on the northern littoral of the Black Sea at the time, suggest that the climate was a little warmer than at present. The pollen investigations intimate a temperature level about 0.5 °C higher than the cold phase around the middle of the first millenium B.C. Support to the aforementioned inference is offered by the recently discovered ice conditions on Mt. Erciyas, Turkey, as they were 2000 years ago. It is also inferred that the precipitation level of the region was, generally, somewhat higher than nowadays.Finally, a brief review is made of glacier, tree-ring density and peatbog data for Europe and North America. They all show that the period around 0 C.E. was relatively warm.In 1986–90 visiting with the Department of Meteorology, University of Copenhagen, Copenhagen, Denmark.     

Climate change in the northeastern US: regional climate model validation and climate change projections

A high resolution regional climate model (RCM) is used to simulate climate of the recent past and to project future climate change across the northeastern US. Different types of uncertainties in climate simulations are examined by driving the RCM with different boundary data, applying different emissions scenarios, and running an ensemble of simulations with different initial conditions. Empirical orthogonal functions analysis and K-means clustering analysis are applied to divide the northeastern US region into four climatologically different zones based on the surface air temperature (SAT) and precipitation variability. The RCM simulations tend to overestimate SAT, especially over the northern part of the domain in winter and over the western part in summer. Statistically significant increases in seasonal SAT under both higher and lower emissions scenarios over the whole RCM domain suggest the robustness of future warming. Most parts of the northeastern US region will experience increasing winter precipitation and decreasing summer precipitation, though the changes are not statistically significant. The greater magnitude of the projected temperature increase by the end of the twenty-first century under the higher emissions scenario emphasizes the essential role of emissions choices in determining the potential future climate change.     

基于博弈模型的中美气候谈判策略模拟

中美在气候谈判中的共识和分歧已成为影响未来气候谈判走向的重要因素。基于效用和博弈理论,考虑温升幅度及其对GDP影响等因素的不确定性,以及气候变化相关投资对各国净现值效用的负面、正面和外溢影响,对中美气候谈判进行博弈策略模拟及敏感性分析。结果表明,中美气候谈判博弈存在先动劣势,且中美在非合作博弈下的气候变化投资远远无法实现全球2℃控温目标;在合作博弈情景下,为确保实现全球温升控制目标的合作框架的稳定和双赢,未来的气候制度框架需要关注对中国的技术、资金支持和补偿。     

On the role of domain size and resolution in the simulations with the HIRHAM region climate model

We investigate the simulated temperature and precipitation of the HIRHAM regional climate model using systematic variations in domain size, resolution and detailed location in a total of eight simulations. HIRHAM was forced by ERA-Interim boundary data and the simulations focused on higher resolutions in the range of 5.5–12 km. HIRHAM outputs of seasonal precipitation and temperature were assessed by calculating distributed model errors against a higher resolution data set covering Denmark and a 0.25° resolution data set covering Europe. Furthermore the simulations were statistically tested against the Danish data set using bootstrap statistics. The results from the distributed validation of precipitation showed lower errors for the winter (DJF) season compared to the spring (MAM), fall (SON) and, in particular, summer (JJA) seasons for both validation data sets. For temperature, the pattern was in the opposite direction, with the lowest errors occurring for the JJA season. These seasonal patterns between precipitation and temperature are seen in the bootstrap analysis. It also showed that using a 4,000 × 2,800 km simulation with an 11 km resolution produced the highest significance levels. Also, the temperature errors were more highly significant than precipitation. In similarly sized domains, 12 of 16 combinations of variables, observation validation data and seasons showed better results for the highest resolution domain, but generally the most significant improvements were seen when varying the domain size.     

美国军方发布《国家安全与气候变化威胁》报告

2007年4月16日,由退休将军组成的美国海军分析中心军事咨询委员会发布了《国家安全与气候变化威胁》报告,从军事角度评估了气候变化对美国国家安全的潜在威胁。这是继2003年10月美国国防部给布什政府提供的一份秘密报告《气候突变的情景及其对美国国家安全的意义》后,美军方再次抛出的关于气候变化成胁美国国家安全的报告。该报告一经发布,媒体争相报道,在国际社会引起了极大反响。