未来四川地区农业气候资源的时空变化特征

进行气候变化背景下四川地区农业气候资源时空变化趋势的预估可对未来应对气候变化及宏观决策提供重要的理论依据。研究利用区域气候模式PRECIS输出的未来A2和B2气候情景(2071-2100年)及基准气候条件(1961-1990年)气象要素资料,分析了四川全年和温度生长期内平均气温、≥10℃积温、日照时数、降水量、参考作物蒸散量和湿润指数的时空变化特征。结果表明,与基准气候条件相比,A2和B2情景下,2071-2100年四川省年平均气温和温度生长期内≥10℃积温呈升高趋势;川西高原年日照时数呈减少趋势,而其他地区以增加为主,温度生长期内日照时数呈增加趋势;A2情景下年降水量以增加为主,B2情景下年降水量有增有减,未来A2和B2情景下温度生长期内降水量在大部地区都呈增加趋势;年参考作物蒸散量和温度生长期内参考作物蒸散量都以增加为主;而年湿润指数和温度生长期内湿润指数在大部地区以减小为主。     

应对气候变化行动的协同关系及研究视角探析

减缓和适应气候变化行动具有交互关系,发现和挖掘具有协同关系的行动有利于低成本应对气候变化。在对国内外相关研究进行文献梳理后发现,减缓和适应行动存在协同关系且具有成本效益优势,主要发生在区域和部门层面,但由于适应气候变化研究较为滞后,减缓和适应行动协同关系研究面临样本不足、研究工具有待开拓等问题,研究边界也有待确定。能源系统受气候变化的双重影响,减缓和适应行动之间存在大量自发的协同效应和竞争关系,具备进一步挖掘协同关系的条件。建议从能源系统入手,增加能源系统的气象灾害风险评估工作,为协同关系研究补充适应行动样本;借助其他学科研究方法对减缓和适应行动的协同关系进行定量研究,开拓适宜的定量分析工具;通过辨识能源系统中具有协同关系的应对气候变化行动,为其他部门和地区的相关研究和实践提供参考和借鉴。     

陆面过程研究的新进展

近年来,陆面过程研究与模式的改进都取得了新进展。文章以VIC-3L模式为代表,分析和总结了近年来在陆面过程、陆面过程参数化、水文与气候模式的耦合、植物动力学和遥感技术在陆面过程中的应用等方面的进展和动态。     

Anthropogenic emission is the main contributor to the rise of atmospheric methane during 1993–2017

Atmospheric methane (CH₄) concentrations have shown a puzzling resumption in growth since 2007 following a period of stabilization from 2000 to 2006. Multiple hypotheses have been proposed to explain the temporal variations in CH₄ growth, and attribute the rise of atmospheric CH₄ either to increases in emissions from fossil fuel activities, agriculture and natural wetlands, or to a decrease in the atmospheric chemical sink. Here, we use a comprehensive ensemble of CH₄ source estimates and isotopic δ¹³C-CH₄ source signature data to show that the resumption of CH₄ growth is most likely due to increased anthropogenic emissions. Our emission scenarios that have the fewest biases with respect to isotopic composition suggest that the agriculture, landfill and waste sectors were responsible for 53 ± 13% of the renewed growth over the period 2007–2017 compared to 2000–2006; industrial fossil fuel sources explained an additional 34 ± 24%, and wetland sources contributed the least at 13 ± 9%. The hypothesis that a large increase in emissions from natural wetlands drove the decrease in atmospheric δ¹³C-CH₄ values cannot be reconciled with current process-based wetland CH₄ models. This finding suggests the need for increased wetland measurements to better understand the contemporary and future role of wetlands in the rise of atmospheric methane and climate feedback. Our findings highlight the predominant role of anthropogenic activities in driving the growth of atmospheric CH₄ concentrations.     

大气气溶胶及其研究概况

大气气溶胶是气候变化研究中的一个极大的不确定性因素,国内外在此方面开展了大量的观测和科学研究.文章论述了大气气溶胶的基本性状、研究的意义及现状.对近年来国际上的重大气溶胶科学计划及当前全球两大气溶胶观测网络,包括世界气象组织的全球大气观测计划(GAW)和气溶胶自动观测网(AERONET)作了详细地介绍.     

Eco-chemical mechanisms govern phytoplankton emissions of dimethylsulfide in global surface waters

The anti-greenhouse gas dimethylsulfide (DMS) is mainly emitted by algae and accounts for more than half of the total natural flux of gaseous sulfur to the atmosphere, strongly reducing the solar radiation and thereby the temperature on Earth. However, the relationship between phytoplankton biomass and DMS emissions is debated and inconclusive. Our study presents field observations from 100 freshwater lakes, in concert with data of global ocean DMS emissions, showing that DMS and algal biomass show a hump-shaped relationship, i.e. DMS emissions to the atmosphere increase up to a pH of about 8.1 but, at higher pH, DMS concentrations decline, likely mainly due to decomposition. Our findings from lake and ocean ecosystems worldwide were corroborated in experimental studies. This novel finding allows assessments of more accurate global patterns of DMS emissions and advances our knowledge on the negative feedback regulation of phytoplankton-driven DMS emissions on climate.     

1956-2013年元江-红河流域径流变化及其影响因素分析

国际河流水文变化和跨境影响一直是国际关注的焦点,从全流域尺度分析径流变化特征及其影响因素可为跨境水资源合理利用和管理等提供科学基础。本文基于元江-红河流域干支流6个水文站径流数据以及64个气象站降水、气温数据,分析径流的年内分配、年际变化特征、径流变化趋势和周期性以及气候变化和人类活动对径流变化的影响。研究结果表明：①元江-红河径流年内分配不均匀,约80%的径流量集中于汛期（6-11月）。支流站点的径流年内分配变化大于干流站点,所有站点径流集中期均表现出提前的趋势;②径流年际变化剧烈,具有明显的丰枯特征,20世纪50年代中期-60年代中期为枯水期,60年代中期-70年代中期为丰水期,70年代中期-90年代初期为平偏枯水期,90年代中期-2002年为平偏丰水期,2002年以后为枯水期;③1956-2013年元江-红河年平均径流量呈减少的趋势,其中李仙江站减少趋势显著;R/S分析表明未来径流量可能呈增加的趋势;④蛮耗站和李仙江站的周期变化主要是4a、6~9a的年际变化和21~22a的年代际周期变化,Son Tay水文站在8~10a和21~22a的年际和年代际变化周期与上游蛮耗站和李仙江站基本一致;⑤流域降水变化是径流量减少的主要原因,人类活动一定程度上改变了径流年内分配特征,但对径流量变化的影响有限。     

基于Budyko假设的流域蒸散发估算及其对气候与下垫面的敏感性分析

蒸散发作为水文循环和能量平衡联系的纽带,对全球和区域水文过程起着重要作用。本文基于Budyko假设,采用全国71个典型流域的水文气象资料,分析了不同水热模型对蒸散发估算精度的影响,并进一步阐释了不同气候和植被类型下蒸散发对降水、潜在蒸散发和下垫面特征的敏感性。结果表明：①水热模型加入反映下垫面特征的参数后,蒸散发的估算精度能得到显著的提高;②蒸散发的敏感性分析结果表明,干旱流域蒸散发对降水最为敏感,其次是下垫面参数和潜在蒸散发;湿润流域蒸散发对下垫面参数最为敏感,其次是潜在蒸散发和降水;③对于不同植被类型的流域而言,森林流域和混合流域蒸散发对降水和下垫面参数变化最为敏感,草地流域蒸散发对降水的变化最为敏感。研究结果对于蒸散发的区域性研究、稀缺资料地区水文预报等有重要的参考意义。     

School climate: the controllable and the uncontrollable

A positive school climate impacts students by promoting positive relations among students, staff and faculty of the school. The current study used latent class analysis and multinomial regression with R3STEP to analyse patterns of negative behaviours in schools and test the association of these patterns with structural variables like school size, demographics, and location using data from the 2008 School Survey on Crime and Safety, (n = 2560). The results indicated five classes of frequencies of negative behaviours. By using the lowest frequency of behaviour class as a reference, the classes with the highest frequencies of bullying, teacher disrespect, and sexual assault were more likely to be found in high crime areas and have larger campuses serving over 1000 students. Implications include the need to serve subgroups of schools based on measurable variables and the need to educate future teachers, administrators, and school psychologists about school climate and positive behaviour support systems.     

Focusing on the Whole Student: An Evaluation of Massachusetts's Wraparound Zone Initiative

We used a comparative interrupted time series design to examine the impact of the Massachusetts' Wraparound Zone Initiative on student achievement, attendance, retention, and suspension. This initiative was designed to create coordinated district systems that allow schools to proactively and systematically address students' nonacademic needs. The state education agency awarded grants to seven high-need districts, each of which used the funds to support a select group of schools in implementing strategies that focused on school climate and culture, family engagement, systems to identify and address student needs, and community partnerships. Results from this study showed that students in Wraparound Zone schools performed better on state academic assessments than students in comparison schools, when considering prior achievement trends. Effects were statistically significant in the 3rd year of implementation. The impact on academic achievement was greatest for third- and fourth-grade students, and was particularly strong for English learners. There was no statistically significant overall impact on attendance, retention, or suspension.