2C or not 2C?

Political attention has increasingly focused on limiting warming to 2 °C. However, there is no consensus on both questions “Is the 2 °C target achievable?” and “What should be done with this target that becomes increasingly difficult to achieve?”. This paper aims at disentangling the points of deep uncertainty underlying this absence on consensus. It first gives simple visualizations of the challenge posed by the 2 °C target and shows how key assumptions (on the points of deep uncertainty) influence the answer to the target achievability question. It then proposes an “uncertainties and decisions tree”, linking different beliefs on climate change, the achievability of different policies, and current international policy dynamics to various options to move forward on climate change.     

不同升温阈值下中国地区极端气候事件变化预估

本文基于耦合模式比较计划第五阶段(CMIP5)的18个全球气候模式的模拟结果,预估了全球平均气温在不同典型浓度路径(RCPs)下达到2℃、3℃和4℃阈值时,中国地区气温和降水的变化,并采用了具有稳定统计意义的27个极端气候指标定量评估了全球平均气温达到不同阈值时,中国地区极端气候事件的可能变化。结果表明,未来我国平均气温增幅将高于全球平均增暖,极端暖事件(如暖夜、暖昼、热带夜)明显增多,达到4℃阈值时,暖夜指数相比参考时段增加约49.9%。极端冷事件(如冷夜、冷昼、霜冻)减少。随全球气温升高,中国北方平均降水增多。在不同升温阈值下,中国地区降水的极端性都体现出增强的趋势,强降水事件发生频率(如中雨日数、大雨日数)和强度(如五日最大降水量、极端强降水量)都明显增加。随升温阈值的升高,这些变化幅度更大,在 RCP8.5 情景下全球升温 3℃和4℃时,中国平均五日最大降水分别增加 12.5mm和17.0mm。我国西南地区极端降水强度的增幅高于其他地区。     

Characterization of C2−C4 NMHCs distributions at a high altitude tropical site in India

Air samples were collected covering a full diurnal cycle during each month of the year 2002 at a mountaintop of Mt. Abu (24.6^∘ N, 72.7^∘ E, 1680 amsl). These samples were analyzed for C₂−C₄ NMHCs using a gas chromatograph (GC) equipped with flame ionization detector (FID). The seasonally averaged diurnal distributions of these NMHCs do not show significant variations in the summer season. While sharp peaks in the diurnal variation of some species during evening hours are additional features apart from higher levels in all NMHCs in the winter season. The seasonal variations in relatively long lived species (e.g. ethane, propane and acetylene) are observed to be more pronounced compared to those in reactive species (e.g. ethene, propene and butanes). The seasonal changes in transport patterns seem to be more dominant factor at this site for the observed variations in NMHCs than changes in OH radical concentration. The annual mean mixing ratios of ethane, ethene, propane, propene, i-butane, acetylene, and n-butane are 1.22 ± 0.58, 0.34 ± 0.24, 0.46 ± 0.20, 0.17 ± 0.14, 0.21 ± 0.18, 0.41 ± 0.43, and 0.31 ± 0.35 ppbv, respectively. Only few pairs of NMHCs are observed to show good correlations, mainly due to transport of air masses with different degree of photochemical processing. A comparison of this measurement with data reported for other remote sites of the globe indicates lower levels of light NMHCs in the tropical sites. The annual mean mixing ratios of various C₂−C₄ NMHCs at Mt. Abu are lower by factors ranging between 3 to 9 compared to a nearest urban site of Ahmedabad. The annual mean propylene (propene) equivalent concentrations of about 1.12 and 8.62 ppbC were calculated for Mt. Abu and Ahmedabad, respectively.     

Natural and anthropogenic C2 to C6 hydrocarbons in the central-eastern Venezuelan atmosphere during the rainy season

The levels of low molecular weight hydrocarbons were measured at pristine sites and rural locations affected by hydrocarbon emissions from oil and gas producing fields in Venezuela. At the clean sites, lower concentrations of C₂ to C₆ alkanes were observed, whereas, in comparison with remotes sites, very much higher levels were measured at the polluted sites. Alkenes present relatively high concentrations, with isoprene being the most abundant, all over the study region. The main sources of alkenes are likely to be natural, mainly from vegetation. The levels of alkanes recorded at the clean sites and the alkene levels found everywhere in the region are in agreement with the values reported for other clean sites in the tropics. The increase of ozone production capacity due to the anthropogenic emissions of alkanes from oil and gas fields was estimated. Due to the presence in the atmosphere of important amounts of naturally emitted isoprene, ethene and propene, which makes a substantial contribution to the reactivity of the hydrocarbon mixture, a small increase (<5%) was estimated to occur in the capacity of the ozone production at a regional scale during the rainy season.     

14C年代学

利用14C的比度测定年代是一项划时代的工作,对推动考古学及古气候研究起了决定性的作用。这项工作是从Libby开始的,他创建了14C年代学的理论基础和实验方法。14C年代学的原理是放射性14C只存在于大气和一切与大气处于交换状态的含碳物质中。一旦该物质脱离交换状态,14C放射性不再得到补偿,只会按衰变规律降低。这样就可以按下列公式算出该物质的年龄,即:     

The CLIVAR C20C project: selected twentieth century climate events

We use a simple methodology to test whether a set of atmospheric climate models with prescribed radiative forcings and ocean surface conditions can reproduce twentieth century climate variability. Globally, rapid land surface warming since the 1970s is reproduced by some models but others warm too slowly. In the tropics, air-sea coupling allows models to reproduce the Southern Oscillation but its strength varies between models. We find a strong relationship between the Southern Oscillation in global temperature and the rate of global warming, which could in principle be used to identify models with realistic climate sensitivity. This relationship and a weak response to ENSO suggests weak sensitivity to changes in sea surface temperature in some of the models used here. In the tropics, most models reproduce part of the observed Sahel drought. In the extratropics, models do not reproduce the observed increase in the North Atlantic Oscillation in response to forcings, through internal variability, or as a combination of both.     

Measuring C T 2 , C Q 2 , and C TQ in the unstable surface layer,and relations to the vertical fluxes of heat and moisture

The structure parameters of temperature (C _T ² ), humidity (C _Q ² ) and temperature-humidity (C _TQ ) were observed at a height of 4 m in the unstable surface layer using thin platinum wires and two Ly- hygrometers. Two ways of measuring structure parameters were employed: one using spaced sensors, the other using time-delayed observations at one location. It is found that the three structure parameters follow free-convection scaling down to -z/L 0.02. The scaling functions % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4baFfea0dXde9vqpa0lb9% cq0dXdb9IqFHe9FjuP0-iq0dXdbba9pe0lb9hs0dXda91qaq-xfr-x% fj-hmeGabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGMbaaaa!3346!\[f\]₁ (of C _T ² ), % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4baFfea0dXde9vqpa0lb9% cq0dXdb9IqFHe9FjuP0-iq0dXdbba9pe0lb9hs0dXda91qaq-xfr-x% fj-hmeGabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGMbaaaa!3346!\[f\]₂ (of C _TO ) and % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4baFfea0dXde9vqpa0lb9% cq0dXdb9IqFHe9FjuP0-iq0dXdbba9pe0lb9hs0dXda91qaq-xfr-x% fj-hmeGabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGMbaaaa!3346!\[f\]₃ (of C _Q ² ) are found to be related through % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4baFfea0dXde9vqpa0lb9% cq0dXdb9IqFHe9FjuP0-iq0dXdbba9pe0lb9hs0dXda91qaq-xfr-x% fj-hmeGabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGMbaaaa!3346!\[f\]₂/% MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4baFfea0dXde9vqpa0lb9% cq0dXdb9IqFHe9FjuP0-iq0dXdbba9pe0lb9hs0dXda91qaq-xfr-x% fj-hmeGabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGMbaaaa!3346!\[f\]₁ 0.69 and % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4baFfea0dXde9vqpa0lb9% cq0dXdb9IqFHe9FjuP0-iq0dXdbba9pe0lb9hs0dXda91qaq-xfr-x% fj-hmeGabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGMbaaaa!3346!\[f\]₃/% MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4baFfea0dXde9vqpa0lb9% cq0dXdb9IqFHe9FjuP0-iq0dXdbba9pe0lb9hs0dXda91qaq-xfr-x% fj-hmeGabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGMbaaaa!3346!\[f\]₁ 0.84. The usefulness of the structure parameters for inferring the fluxes of heat and water vapor, as well as the Bowen ratio, is demonstrated. The scatter is about 30% on either side of the mean.This work was done while the author was a visiting scientist at the Wave Propagation Laboratory, NOAA, ERL, Boulder, U.S.A. He received support from the Netherlands Minister for Science Policy and the U.S. Army Research Office.     

FY-3A/MERSI、MODIS C5.1和C6气溶胶光学厚度产品在中国区域与地面观测站点的对比分析

准确获取气溶胶光学厚度对于气候变化研究和大气环境监测具有重要意义。通过波长插值和时空匹配方法,利用气溶胶自动观测站网（AERONET）观测的气溶胶光学厚度（AOD）对风云3A/中分辨率光谱成像仪（FY-3A/MERSI）、Terra（Aqua）/MODIS的C5.1（Collections 5.1）和C6（Collections 6）气溶胶光学厚度产品在中国区域的反演精度进行验证分析。结合一次发生在中国境内的沙尘天气与一次严重雾霾天气个例,分析上述卫星气溶胶光学厚度的分布特征。研究结果表明,（1）FY-3A/MERSI AOD的反演精度较高（R=0.887,RMSE=0.234）,其值低于AERONET的观测值（Bias=-0.293）。（2）在不同的下垫面下,各种卫星暗像元算法AOD产品反演精度有差异,植被覆盖情况越好,反演精度越高,而植被很少的地区,即亮地表甚至没有反演值。（3）MODIS C5.1深蓝算法产品能在亮地表地区反演AOD,但效果不佳。MODIS C6中的深蓝算法产品在不同下垫面的反演精度都很高（RMSE为0.096-0.127）。（4）在不同季节的对比中,各种卫星AOD产品在夏季的反演精度最差,而反演最好的季节各有不同。（5）在一次沙尘天气污染与一次严重雾霾天气个例中,中国西部与北部区域,MODIS C6深蓝算法AOD的监测效果优于其他算法AOD;MERSI AOD产品在此区域的分布不连续。总体而言,MODIS C6 AOD分布比MODIS C5.1产品连续,MODIS 3 km产品在相同区域的AOD值高于其他产品。以上结论可为卫星AOD产品在中国区域的使用提供参考。      

C.T.R. Wilson versus G.C. Simpson: Fifty years of controversy in atmospheric electricity

Two British scientists, G.C. Simpson and C.T.R. Wilson, held contrasting views on the electrical polarity of thunderclouds for nearly half of the 20th century. Simpson's perspective was dominated by the measured charge on rain, by the breaking drop theory for the charging of raindrops, and later, by the branching behavior of lightning flashes. Wilson's view was dominated by his work on the field changes accompanying lightning, by his knowledge of the corona current from the ground beneath electrified clouds, and ultimately by his unifying global circuit hypothesis, requiring a source current to maintain a negatively charged Earth against dissipation. Simpson's observed tripole structure of thunderclouds provided partial resolution to the controversy, but the main positive dipole supported Wilson's view, which survives today.     

C波段多普勒雷达观测暴雨灾害过程的分析

本文通过对2005年6月29~30日成都地区一次西太平洋副热带高压影响的暴雨天气过程的常规气象资料和位于凤凰山C波段多普勒天气雷达观测资料的分析, 重点从多普勒雷达反射率因子 (Z) 、径向速度 (V) 、速度谱宽 (W) 和垂直累积含水量 (VIL) 出发, 归纳出对成都地区暴雨灾害短临预报应用具有一定参考价值的回波特征指标, 提高和改善该地区暴雨灾害的监测和预警能力。      

C Builder中基于ADO的数据库访问方法

介绍了C Builder中ADO数据库访问控件的属性及其使用方法,并以Access 2000数据库为例,给出了如何利用ADO控件对数据记录进行添加、查询的操作方法。     

中国地区两种MODIS气溶胶产品的比较分析

对比分析了2003-2009年中国及其周边地区中分辨率成像光谱仪(MODIS)C004和C005的气溶胶光学厚度(AOD)产品特征,并将MODIS的气溶胶产品与AERONET观测站资料做了对比分析。结果表明：(1)中国及其周边地区AOD平均值为0.34±0.32,具有显著的空间变化;C005反演算法得到的AOD产品对C...     

Some recent climatic changes in Washington,D.C.

Summary The frequency of occurrence of clear and cloudy days in Washington, D. C., is compared for the intervals 1891–1920 and 1921–1950. There has been a steady increase of cloudy days, 36 more per year, and a decrease of clear days, 57 less per year. This change is reflected in all months of the year even though to a varying degree. The monthly frequency distributions show a statistically barely significant difference between the two intervals. This difference, in the light of collateral evidence, is, however, not attributable to chance. In conjunction with trends observed in temperature, dew point, and humidity values, only part of the change in cloud conditions can be ascribed to the growth of the city but is more likely due to the increasing maritime character of the climate in the northeastern United States.

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Zusammenfassung Die Häufigkeiten heiterer und trüber Tage in Washington werden für die Perioden 1891 bis 1920 und 1921 bis 1950 verglichen. Dabei wird eine stetige Zunahme der jährlichen Zahl trüber Tage um durchschnittlich 36 und eine Abnahme der heiteren Tage um 57 festgestellt. Diese Änderungen treten in wechselndem Maße in allen Monaten auf. Die Unterschiede der monatlichen Häufigkeitsverteilungen liegen im statistischen Sinn gerade innerhalb der Grenze der Überzufälligkeit; doch können sie trotzdem auf Grund anderer, allgemeiner Überlegungen als reell angesehen werden. Im Zusammenhang mit der Tendenz von Temperatur, Taupunkt und Feuchte kann die Änderung der Bewölkungsverhältnisse nur zum Teil auf das Wachsen der Großstadt zurückgeführt werden und hängt wohl mehr mit dem zunehmend maritimen Charakter des Klimas der nordöstlichen Vereinigten Staaten zusammen.

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Résumé On compare les fréquences des jours clairs et des jours couverts à Washington pendant les périodes 1891–1920 et 1921–1950, et l'on constate une augmentation continue du nombre annuel moyen de jours couverts de 36, et une diminution des jours clairs de 57; ces changements se répartissent d'une façon variable sur tous les mois. Les différences des fréquences mensuelles restent dans les limites des probabilités statistiques; mais pour des raisons d'ordre général on peut les considérer comme réelles. Envisagées conjointement avec les tendances de la température, du point de rosée et de l'humidité, les modifications de la nébulosité ne s'expliquent que partiellement par l'accroissement de l'agglomération urbaine et dépendent certainement du fait que le climat du Nord-Est des Etats-Unis voit s'accentuer son caractère maritime.

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With 3 figures.     

On the Budget of OH Radicals and Ozone in an Urban Plume from the Decay of C5–C8 Hydrocarbons and NOx

Simultaneous measurements of ozone and ozoneprecursors were made during a field campaign atSchauinsland in the Black Forest and in the valleynorth of Schauinsland that channels the flow ofpolluted air from the city of Freiburg to the site.From the decay of hydrocarbons and NO_x between the twomeasuring sites and the known rate coefficients, theconcentration of OH radicals was calculated. From abudget analysis of OH and HO_x it is concluded that therelatively high OH concentrations (5–8 ×10⁶cm^-3) in the presence of high NO₂concentrations cannot be explained by the knownprimary sources. The budget can be closed if efficientrecycling of OH via HO₂ is assumed to occur andthat, based on the measured hydrocarbons, 2 HO₂molecules are formed for each OH radical that reactswith a hydrocarbon molecule. This assumption is inaccordance with the budget of O_x obtained from ourmeasurements and with results from earliermeasurements of alkylnitrates and peroxy radicals atSchauinsland. A possible conclusion is that the decayof precursors and production of photooxidants in urbanplumes proceeds at a faster rate than is currentlyassumed. The potential role of biogenichydrocarbons for the radical budget is alsodiscussed.     

模糊C均值聚类法在新疆年降水气候分区中的应用

利用新疆98个气象站1960-2011年的年降水量资料,采用模糊C均值聚类法,对新疆年降水量进行分区研究;同时利用线性趋势、累积距平、M-K检验、t检验相结合的方法,对新疆年降水量在不同区域上的变化趋势以及突变时间等进行了对比诊断分析,得到了新疆地区年降水量分布的空间特征。结果表明：（1）新疆年降水的分布大致可分为7个区域;（2）根据模糊C均值方法所分区域能够体现出由于地形差异导致的降水分布不均匀的特点,这一结果与其他研究干旱区降水分布差异产生的原因相同。分区结果合理,说明该聚类方法适用于区域气候区划;（3）新疆大部分区域的降水量在20世纪80年代中后期以前偏少,低于多年平均值,自80年代中后期以后才开始偏多;不同区域的降水量依次从70年代初、80年代中后期、90年代初开始增加;整个南疆盆地、阿勒泰地区、准噶尔盆地降水的突变时间较为接近;（4）新疆降水量整体异常表现为降水一致多（或少）、北多南少、西多东少。