Based on 20 models from phase 6 of the Coupled Model Intercomparison Project(CMIP6),this article explored possible reasons for differences in simulation biases and projected changes in precipitation in northern China ...Based on 20 models from phase 6 of the Coupled Model Intercomparison Project(CMIP6),this article explored possible reasons for differences in simulation biases and projected changes in precipitation in northern China among the allmodel ensemble(AMME),“highest-ranked”model ensemble(BMME),and“lowest-ranked”model ensemble(WMME),from the perspective of atmospheric circulations and moisture budgets.The results show that the BMME and AMME reproduce the East Asian winter circulations better than the WMME.Compared with the AMME and WMME,the BMME reduces the overestimation of evaporation,thereby improving the simulation of winter precipitation.The three ensemble simulated biases for the East Asian summer circulations are generally similar,characterized by a stronger zonal pressure gradient between the mid-latitudes of the North Pacific and East Asia and a northward displacement of the East Asian westerly jet.However,the simulated vertical moisture advection is improved in the BMME,contributing to the slightly higher performance of the BMME than the AMME and WMME on summer precipitation in North and Northeast China.Compared to the AMME and WMME,the BMME projects larger increases in precipitation in northern China during both seasons by the end of the 21st century under the Shared Socioeconomic Pathway 5-8.5(SSP5-8.5).One of the reasons is that the increase in evaporation projected by the BMME is larger.The projection of a greater dynamic contribution by the BMME also plays a role.In addition,larger changes in the nonlinear components in the BMME projection contribute to a larger increase in winter precipitation in northern China.展开更多
大气氧化能力(AOC)通常是指大气通过氧化过程去除大气中微量气体成分的速率总和。在对流层和近地层大气中,AOC主要表观为对污染气体的清除能力或净化能力,亦称大气氧化性。AOC是地球大气自洁净的核心能力,但一直缺乏对其内涵的深入认知...大气氧化能力(AOC)通常是指大气通过氧化过程去除大气中微量气体成分的速率总和。在对流层和近地层大气中,AOC主要表观为对污染气体的清除能力或净化能力,亦称大气氧化性。AOC是地球大气自洁净的核心能力,但一直缺乏对其内涵的深入认知和对其指标的量化描述。本文作者通过承担国家重点研发计划“区域大气氧化能力与空气质量的定量关系及调控原理”研究等项目,从大气化学基本理论入手,对AOC开展了系列研究,并在其量化表达方面取得了突破性进展。本文将围绕“大气氧化能力量化研究”这一科学问题,对这些进展进行简要的描述。首先在深入认知AOC内涵的基础上,分别从大气化学的热力学和动力学基本原理出发,构建了大气氧化能力表观指数(AOIe)和潜势指数(AOIp),并通过二者归一化指数日变化闭合研究,发现了非均相化学过程对AOC的贡献不容忽视。随着PM2.5污染的加重,无论夏季还是冬季,AOIe亦随之增加,但在冬季AOIp则出现了相反的情景,表现出AOIp的变化受气象条件的影响更大。AOC闭合研究思路用于大气OH自由基的储库分子HONO“未知源”研究,发现了北京大气HONO的重要非均相来源,阐释了MCM(Master Chemical Mechanism)机制对冬季AOC低估的重要原因。AOIp用于预测我国大气臭氧污染潜势格局,发现臭氧光化学生成表观潜势(AOIp_O_(3))与NO_(2)的光解系数[J(NO_(2))]直接相关,全国J(NO_(2))的年均值为4.39×10^(-3)s^(-1),高值区主要分布在四川、贵州、重庆和湖南等地。与其他化学反应氧化性指数对比,AOIe与AOIp组合指数更具准确性、普适性和实用性,可评价已发生的污染过程AOC的变化,亦可预测城市或区域重污染发生的可能性及其变化和格局。展开更多
随着国家对科技投入的不断增长,加快推进高水平科技自立自强,成为国家发展和安全的重要支撑和保障。深入探讨了美国科技相关部门和资助机构在预算绩效管理与评价方面的经验和做法,通过对美国预算绩效管理历史沿革的回顾,从早期绩效评价...随着国家对科技投入的不断增长,加快推进高水平科技自立自强,成为国家发展和安全的重要支撑和保障。深入探讨了美国科技相关部门和资助机构在预算绩效管理与评价方面的经验和做法,通过对美国预算绩效管理历史沿革的回顾,从早期绩效评价探索至《政府绩效与结果法案》《总统管理议程》《政府绩效与结果修正案》的相继出台,揭示了美国科技预算绩效管理法制化、系统化的发展轨迹。以美国国家科学基金会(National Science Foundation,NSF)、美国能源部(Department of Energy,DOE)为例,详细分析了战略目标设定、绩效指标制定和绩效评价过程。从突出自上而下的战略引领作用、强化结果导向的绩效管理、完善绩效目标和评价的持续管理制度、建立规范的预算绩效管理流程4个方面提出建议,以期为中国的科技预算绩效管理提供借鉴和启示。展开更多
基金jointly supported by the National Natural Science Foundation of China(Grant No.41991285)the National Key Research and Development Program of China(2017YFA0605004)the Program for Distinguished Professors of Jiangsu。
文摘Based on 20 models from phase 6 of the Coupled Model Intercomparison Project(CMIP6),this article explored possible reasons for differences in simulation biases and projected changes in precipitation in northern China among the allmodel ensemble(AMME),“highest-ranked”model ensemble(BMME),and“lowest-ranked”model ensemble(WMME),from the perspective of atmospheric circulations and moisture budgets.The results show that the BMME and AMME reproduce the East Asian winter circulations better than the WMME.Compared with the AMME and WMME,the BMME reduces the overestimation of evaporation,thereby improving the simulation of winter precipitation.The three ensemble simulated biases for the East Asian summer circulations are generally similar,characterized by a stronger zonal pressure gradient between the mid-latitudes of the North Pacific and East Asia and a northward displacement of the East Asian westerly jet.However,the simulated vertical moisture advection is improved in the BMME,contributing to the slightly higher performance of the BMME than the AMME and WMME on summer precipitation in North and Northeast China.Compared to the AMME and WMME,the BMME projects larger increases in precipitation in northern China during both seasons by the end of the 21st century under the Shared Socioeconomic Pathway 5-8.5(SSP5-8.5).One of the reasons is that the increase in evaporation projected by the BMME is larger.The projection of a greater dynamic contribution by the BMME also plays a role.In addition,larger changes in the nonlinear components in the BMME projection contribute to a larger increase in winter precipitation in northern China.
文摘大气氧化能力(AOC)通常是指大气通过氧化过程去除大气中微量气体成分的速率总和。在对流层和近地层大气中,AOC主要表观为对污染气体的清除能力或净化能力,亦称大气氧化性。AOC是地球大气自洁净的核心能力,但一直缺乏对其内涵的深入认知和对其指标的量化描述。本文作者通过承担国家重点研发计划“区域大气氧化能力与空气质量的定量关系及调控原理”研究等项目,从大气化学基本理论入手,对AOC开展了系列研究,并在其量化表达方面取得了突破性进展。本文将围绕“大气氧化能力量化研究”这一科学问题,对这些进展进行简要的描述。首先在深入认知AOC内涵的基础上,分别从大气化学的热力学和动力学基本原理出发,构建了大气氧化能力表观指数(AOIe)和潜势指数(AOIp),并通过二者归一化指数日变化闭合研究,发现了非均相化学过程对AOC的贡献不容忽视。随着PM2.5污染的加重,无论夏季还是冬季,AOIe亦随之增加,但在冬季AOIp则出现了相反的情景,表现出AOIp的变化受气象条件的影响更大。AOC闭合研究思路用于大气OH自由基的储库分子HONO“未知源”研究,发现了北京大气HONO的重要非均相来源,阐释了MCM(Master Chemical Mechanism)机制对冬季AOC低估的重要原因。AOIp用于预测我国大气臭氧污染潜势格局,发现臭氧光化学生成表观潜势(AOIp_O_(3))与NO_(2)的光解系数[J(NO_(2))]直接相关,全国J(NO_(2))的年均值为4.39×10^(-3)s^(-1),高值区主要分布在四川、贵州、重庆和湖南等地。与其他化学反应氧化性指数对比,AOIe与AOIp组合指数更具准确性、普适性和实用性,可评价已发生的污染过程AOC的变化,亦可预测城市或区域重污染发生的可能性及其变化和格局。
文摘随着国家对科技投入的不断增长,加快推进高水平科技自立自强,成为国家发展和安全的重要支撑和保障。深入探讨了美国科技相关部门和资助机构在预算绩效管理与评价方面的经验和做法,通过对美国预算绩效管理历史沿革的回顾,从早期绩效评价探索至《政府绩效与结果法案》《总统管理议程》《政府绩效与结果修正案》的相继出台,揭示了美国科技预算绩效管理法制化、系统化的发展轨迹。以美国国家科学基金会(National Science Foundation,NSF)、美国能源部(Department of Energy,DOE)为例,详细分析了战略目标设定、绩效指标制定和绩效评价过程。从突出自上而下的战略引领作用、强化结果导向的绩效管理、完善绩效目标和评价的持续管理制度、建立规范的预算绩效管理流程4个方面提出建议,以期为中国的科技预算绩效管理提供借鉴和启示。