Air–Sea \mathrm{CO}_{2} Gas Transfer Velocity in a Shallow Estuary

The air–sea transfer velocity of $\mathrm{CO}_{2}\, (k_{\mathrm{CO}_{2}})$ was investigated in a shallow estuary in March to July 2012, using eddy-covariance measurements of $\mathrm{CO}_{2}$ fluxes and measured air–sea $\mathrm{CO}_{2}$ partial-pressure differences. A data evaluation method that eliminates data by nine rejection criteria in order to heighten parametrization certainty is proposed. We tested the data evaluation method by comparing two datasets: one derived using quality criteria related solely to the eddy-covariance method, and the other derived using quality criteria based on both eddy-covariance and cospectral peak methods. The best parametrization of transfer velocity normalized to a Schmidt number of 600 $(k_{600})$ was determined to be: $k_{600} = 0.3\,{U_{10}}^{2.5}$ where $U_{10}$ is the wind speed in m $\mathrm{s}^{-1}$ at 10 m; $k_{600}$ is based on $\mathrm{CO}_{2}$ fluxes calculated by the eddy-covariance method and including the cospectral peak method criteria. At low wind speeds, the transfer velocity in the shallow water estuary was lower than in other coastal waters, possibly a symptom of low tidal amplitude leading to low intensity water turbulence. High transfer velocities were recorded above wind speeds of 5 m $\mathrm{s}^{-1}$ , believed to be caused by early-breaking waves and the large fetch (6.5 km) of the estuary. These findings indicate that turbulence in both air and water influences the transfer velocity.     

RCP 8.5��A scenario of comparatively high greenhouse gas emissions

This paper summarizes the main characteristics of the RCP8.5 scenario. The RCP8.5 combines assumptions about high population and relatively slow income growth with modest rates of technological change and energy intensity improvements, leading in the long term to high energy demand and GHG emissions in absence of climate change policies. Compared to the total set of Representative Concentration Pathways (RCPs), RCP8.5 thus corresponds to the pathway with the highest greenhouse gas emissions. Using the IIASA Integrated Assessment Framework and the MESSAGE model for the development of the RCP8.5, we focus in this paper on two important extensions compared to earlier scenarios: 1) the development of spatially explicit air pollution projections, and 2) enhancements in the land-use and land-cover change projections. In addition, we explore scenario variants that use RCP8.5 as a baseline, and assume different degrees of greenhouse gas mitigation policies to reduce radiative forcing. Based on our modeling framework, we find it technically possible to limit forcing from RCP8.5 to lower levels comparable to the other RCPs (2.6 to 6 W/m²). Our scenario analysis further indicates that climate policy-induced changes of global energy supply and demand may lead to significant co-benefits for other policy priorities, such as local air pollution.     

Is climate change affecting wolf populations in the high arctic?

Gobal climate change may affect wolves in Canadas High Arctic (80° N) acting through three trophic levels (vegetation, herbivores, and wolves). A wolf pack dependent on muskoxen and arctic hares in the Eureka area of Ellesmere Island denned and produced pups most years from at least 1986 through 1997. However, when summer snow covered vegetation in 1997 and 2000 for the first time since records were kept, halving the herbivore nutrition-replenishment period, muskox and hare numbers dropped drastically, and the area stopped supporting denning wolves through 2003. The unusual weather triggering these events was consistent with global-climate-change phenomena.     

An Approach to Minimizing Artifacts Caused by Cross-Sensitivity in the Determination of Air–Sea \text{ CO }_{2} Flux Using the Eddy-Covariance Technique

The air–sea $\text{ CO }_{2}$ flux was measured from a research vessel in the North Yellow Sea in October 2007 using an open-path eddy-covariance technique. In 11 out of 64 samples, the normalized spectra of scalars ( $\text{ CO }_{2}$ , water vapour, and temperature) showed similarities. However, in the remaining samples, the normalized $\text{ CO }_{2}$ spectra were observed to be greater than those of water vapour and temperature at low frequencies. In this paper, the noise due to cross-sensitivity was identified through a combination of intercomparisons among the normalized spectra of three scalars and additional analyses. Upon examination, the cross-sensitivity noise appeared to be mainly present at frequencies ${<}0.8\,\text{ Hz }$ . Our analysis also suggested that the high-frequency fluctuations of $\text{ CO }_{2}$ concentration (frequency ${>}0.8\,\text{ Hz }$ ) was probably less affected by the cross-sensitivity. To circumvent the cross-sensitivity issue, the cospectrum in the high-frequency range 0.8–1.5 Hz, instead of the whole range, was used to estimate the $\text{ CO }_{2}$ flux by taking the contribution of the high frequency to the $\text{ CO }_{2}$ flux to be the same as the contribution to the water vapour flux. The estimated air–sea $\text{ CO }_{2}$ flux in the North Yellow Sea was $-0.039\,\pm \,0.048\,\text{ mg } \text{ m }^{-2}\,\text{ s }^{-1},$ a value comparable to the estimates using the inertial dissipation method and Edson’s method (Edson et al., J Geophys Res 116:C00F10, 2011).     

Detection of the synoptic southeastward-extending Siberian cold high during 1978–2017

To better understand the relationship between anticyclones in Siberia and cold-air activities and temperature changes in East Asia, this study proposes a 2D anticyclone identification method based on a deep-learning model, Mask R-CNN, which can reliably detect the changes in the morphological characteristics of anticyclones. Using the new method, the authors identified the southeastward-extending Siberian cold high (SEESCH), which greatly affects wintertime temperatures in China. This type of cold high is one of the main synoptic systems (45.7%) emerging from Siberia in winter. Cold air carried by SEESCH has a significant negative correlation with the temperature changes in the downstream area, and 52% of SEESCHs are accompanied by cold-air accumulation in North and East China, which has a significant impact on regional cooling. These results provide clues for studying the interconnection between SEESCHs and extreme cold events.摘要为了更好地研究西伯利亚地区反气旋与冷空气活动,东亚地区气温变化之间的关联, 本文提出一种基于Mask R-CNN的反气旋识别方法, 能够较为准确地刻画反气旋形态特征变化. 使用该方法能够识别对中国冬季气温具有较大影响的东南延伸型西伯利亚冷高压(SEESCH), 这种冷高压是冬季出现在西伯利亚地区的主要天气系统之一(45.7%). SEESCH携带的冷空气与下游地区温度变化呈显著负相关, 52%的SEESCH伴随着华北华东地区冷空气聚集, 对区域降温有显著影响. 这些结果为研究 SEESCH 与极端寒冷事件之间的联系提供线索.     

Low and high frequency Madden–Julian oscillations in austral summer: interannual variations

The Madden–Julian oscillation (MJO) is the main component of intraseasonal variability of the tropical convection, with clear climatic impacts at an almost-global scale. Based on satellite observations, it is shown that there are two types of austral-summer MJO events (broadly defined as 30–120 days convective variability with eastward propagation of about 5 m/s). Equatorial MJO events have a period of 30–50 days and tend to be symmetric about the equator, whereas MJO events centered near 8°S tend to have a longer period of 55–100 days. The lower-frequency variability is associated with a strong upper-ocean response, having a clear signature in both sea surface temperature and its diurnal cycle. These two MJO types have different interannual variations, and are modulated by the Indian Ocean Dipole (IOD). Following a negative IOD event, the lower-frequency southern MJO variability increases, while the higher-frequency equatorial MJO strongly diminishes. We propose two possible explanations for this change in properties of the MJO. One possibility is that changes in the background atmospheric circulation after an IOD favour the development of the low-frequency MJO. The other possibility is that the shallower thermocline ridge and mixed layer depth, by enhancing SST intraseasonal variability and thus ocean–atmosphere coupling in the southwest Indian Ocean (the breeding ground of southern MJO onset), favour the lower-frequency southern MJO variability.     

Variations of δ^18 O in Precipitation along Vapor Transport Paths

Three sampling cross sections along the south path starting from the Tropics through the vapor passage in the Yunnan-Guizhou Plateau to the middle-low reaches of the Yangtze River, the north path from West China, via North China, to Japan under the westerlies, and the plateau path from South Asia over the Himalayas to the northern Tibetan Plateau, are set up, based on the IAEA (International Atomic Energy Agency)/WMO global survey network and sampling sites on the Tibetan Plateau. The variations, and the relationship with precipitation and temperature, of the δ^18 O in precipitation along the three cross sections are analyzed and compared. Along the south path, the seasonal differences of mean δ^18 O in precipitation are small at the stations located in the Tropics, but increase markedly from Bangkok towards the north, with the 51so in the rainy season smaller than inthe dry season. The δ^18 O sovalues in precipitation fluctuate on the whole, which shows that there are different vapor sources. Along the north path, the seasonal differences of the mean δ^18 O in precipitation for the stations in the west of Zhengzhou are all greater than in the east of Zhengzhou. During the cold half of the year, the mean δ^18 O in precipitation reaches its minimum at Uriimqi with the lowest temperature due to the wide, cold high pressure over Mongolia, then increases gradually with longitude, and remains at roughly the same level at the stations eastward from Zhengzhou. During the warm half of the year, the δ^18 O values in precipitation are lower in the east than in the west, markedly influenced by the summer monsoon over East Asia. Along the plateau path, the mean δ^18 O values in precipitation in the rainy season are correspondingly high in the southern parts of the Indian subcontinent, and then decrease gradually with latitude. A sharp depletion of the stable isotopic compositions in precipitation takes place due to the very strong rainout of the stable isotopic compositions in vapor in the process of lifting over the southern slope of the Himalayas. The low level of the δ^18 O in precipitation is from Nyalam to the Tanggula Mountains during the rainy season,but δ^18 O increases persistently with increasing latitude from the Tanggula Mountains to the northern Tibetan Plateau because of the replenishment of vapor with relatively heavy stable isotopic compositions originating from the inner plateau. During the dry season, the mean δ^18 O values in precipitation basically decrease along the path from the south to the north. Generally, the mean δ^18 O in precipitation during the rainy season is lower than in the dry season for the regions controlled by the monsoons over South Asia or the plateau, and opposite for the regions without a monsoon or with a weak monsoon.     

长江流域大气降水中δ^18O变化与水汽来源

根据GNIP所提供的长江流域多年月平均降水中δD、δ^18O料以及NOAA-CIRES提供的NCEP/NCAR再分析资料,研究了长江流域降水稳定同位素与降水量、水汽压、温度和水汽来源之间的关系。结果表明：在平均季节尺度下,长江流域大气降水中δ^18O降水量、水汽压和温度均存在显著的负相关关系,说明该流域降水中δ^18O...     

长江流域大气降水中δ^18O变化与水汽来源

根据GNIP所提供的长江流域多年月平均降水中δD、δ^18O料以及NOAA-CIRES提供的NCEP/NCAR再分析资料,研究了长江流域降水稳定同位素与降水量、水汽压、温度和水汽来源之间的关系。结果表明：在平均季节尺度下,长江流域大气降水中δ^18O降水量、水汽压和温度均存在显著的负相关关系,说明该流域降水中δ^18O化存在显著的降水量效应、湿度效应和反温度效应。基于降水中过量氘示踪水汽来源原理,分析了中国长江流域季风区降水中过量氘与阿拉伯海、孟加拉湾和南印度洋3个海区相对湿度的关系,表明中国长江流域的水汽主要来源于上述3个海区,而昆明和成都可能受到其他水汽作用,使其与水汽源区的相对湿度呈正相变化。     

Advances in Air–Sea \hbox {CO}_2 Flux Measurement by Eddy Correlation

Eddy-correlation measurements of the oceanic \(\hbox {CO}_2\) flux are useful for the development and validation of air–sea gas exchange models and for analysis of the marine carbon cycle. Results from more than a decade of published work and from two recent field programs illustrate the principal interferences from water vapour and motion, demonstrating experimental approaches for improving measurement precision and accuracy. Water vapour cross-sensitivity is the greatest source of error for \(\hbox {CO}_2\) flux measurements using infrared gas analyzers, often leading to a ten-fold bias in the measured \(\hbox {CO}_2\) flux. Much of this error is not related to optical contamination, as previously supposed. While various correction schemes have been demonstrated, the use of an air dryer and closed-path analyzer is the most effective way to eliminate this interference. This approach also obviates density corrections described by Webb et al. (Q J R Meteorol 106:85–100, 1980). Signal lag and frequency response are a concern with closed-path systems, but periodic gas pulses at the inlet tip provide for precise determination of lag time and frequency attenuation. Flux attenuation corrections are shown to be \(<\) 5 % for a cavity ring-down analyzer (CRDS) and dryer with a 60-m inlet line. The estimated flux detection limit for the CRDS analyzer and dryer is a factor of ten better than for IRGAs sampling moist air. While ship-motion interference is apparent with all analyzers tested in this study, decorrelation or regression methods are effective in removing most of this bias from IRGA measurements and may also be applicable to the CRDS.     

二维温盐环流模型研究^14C在海洋中的分布

海洋碳循环模式中常使用放射性同位素＾１４Ｃ来检验该模式的物理模型是否较好地反映了海洋中的大尺度变化的过程。本工作使用的物理模型是包括太平洋、大西洋和南大洋在内的二维温盐环流模式，在给定的年平均海表强迫下积分４０００年后，环流达到准稳态，其定常流场用来驱动＾１４Ｃ模式。对＾１４Ｃ模式积分５０００年以上，可得到＾１４Ｃ稳态的分布。使用不同的二氧化碳海气交换系数和垂直湍流扩散系数值进行了７个实验，发现使     

Conditions of generation of extremely high water content of Primorye rivers in autumn–winter 2012

Analyzed are the synoptic and hydrological conditions of the generation of extremely high water content of Primorye rivers in the autumn of 2012. Revealed are the general features of atmospheric circulation, precipitation, water content, and hydrological regime of rivers. Presented are quantitative parameters characterizing the extremity of observed events. The expert assessment of the probability of such combination of events demonstrates that its return period is about 500–1000 years if there is assumption on the stationarity of processes. Taking into account the revealed facts and available assessments of climate changes it can be supposed that the analyzed event rather indicates real changes in the hydrological regime of the region than represents a rare random phenomenon.     

天目山柳杉树轮δ^13C对华东地区降水序列的重建

对采自天目山的柳杉树轮进行交叉定年后，得到树轮的δ^13C年序列。将δ^13C年序列去除大气CO2的影响，保留其高频振荡部分。利用华东地区部分气象站的降水资料，通过主成份分析，分析了降水与树轮δ^13C之间的关系。考虑滞后效应，利用回归方法重建了过去一百多年来的华东地区不同时段的降水序列，并分析了其变化特征。     

The future of the past—an earth system framework for high resolution paleoclimatology: editorial essay

High-resolution paleoclimatology is the study of climate variability and change on interannual to multi-century time scales. Its primary focus is the past few millennia, a period lacking major shifts in external climate forcing and earth system configuration. Large arrays of proxy climate records derived from natural archives have been used to reconstruct aspects of climate in recent centuries. The main approaches used have been empirical and statistical, albeit informed by prior knowledge both of the physics of the climate, and of the processes imprinting climate information in the natural archives. We propose a new direction, in which emerging tools are used to formalize the combination of process knowledge and proxy climate records to better illuminate past climate variability on these time scales of great relevance to human concerns.     

A study of climate model responses of the western Pacific subtropical high to El Niño diversity

Climate Dynamics - This study examines a climate model hindcast of the responses of the western Pacific subtropical high (WPSH) to three types of El Niño events: the Eastern Pacific (EP) El...     

Scenarios for a 2 °C world: a trade-linked input–output model with high sector detail

In this study a scenario model is used to examine if foreseen technological developments are capable of reducing CO₂ emissions in 2050 to a level consistent with United Nations Framework Convention on Climate Change (UNFCCC) agreements, which aim at maximizing the temperature rise to 2 °C compared to pre-industrial levels. The model is based on a detailed global environmentally extended supply–use table (EE SUT) for the year 2000, called EXIOBASE. This global EE SUT allows calculating how the final demand in each region drives activities in production sectors, and hence related CO₂ emissions, in each region. Using this SUT framework, three scenarios have been constructed for the year 2050. The first is a business-as-usual scenario (BAU), which takes into account population, economic growth, and efficiency improvements. The second is a techno-scenario (TS), adding feasible and probable climate mitigation technologies to the BAU scenario. The third is the towards-2-degrees scenario (2DS), with a demand shift or growth reduction scenario added to the TS to create a 2 °C scenario. The emission results of the three scenarios are roughly in line with outcomes of typical scenarios from integrated assessment models. Our approach indicates that the 2 °C target seems difficult to reach with advanced CO₂ emission reduction technologies alone.

Policy relevance

The overall outlook in this scenario study is not optimistic. We show that CO₂ emissions from steel and cement production and air and sea transport will become dominant in 2050. They are difficult to reduce further. Using biofuels in air and sea transport will probably be problematic due to the fact that agricultural production largely will be needed to feed a rising global population and biofuel use for electricity production grows substantially in 2050. It seems that a more pervasive pressure towards emission reduction is required, also influencing the basic fabric of society in terms of types and volumes of energy use, materials use, and transport. Reducing envisaged growth levels, hence reducing global gross domestic product (GDP) per capita, might be one final contribution needed for moving to the 2 °C target, but is not on political agendas now.     

Pathways of Influence of the Northern Hemisphere Mid–high Latitudes on East Asian Climate: A Review

This paper reviews recent progress made by Chinese scientists on the pathways of influence of the Northern Hemisphere mid–high latitudes on East Asian climate within the framework of a "coupled oceanic–atmospheric(land–atmospheric or seaice–atmospheric) bridge" and "chain coupled bridge". Four major categories of pathways are concentrated upon, as follows:Pathway A—from North Atlantic to East Asia; Pathway B—from the North Pacific to East Asia; Pathway C—from the Arctic to East Asia; and Pathway D—the synergistic effects of the mid–high latitudes and tropics. In addition, definitions of the terms "combined effect", "synergistic effect" and "antagonistic effect" of two or more factors of influence or processes and their criteria are introduced, so as to objectively investigate those effects in future research.