Combined effects of pumped-storage operation and climate change on thermal structure and water quality

Climatic Change - The assessment of ecological impacts of pumped-storage (PS) hydropower plants on the two connected water bodies is usually based on present climatic conditions. However,...     

关于东亚副热带季风和热带季风的再认识

利用NCEP/NCAR再分析数据集和CMAP(Climate Prediction Center Merged Analysis of Precipitation)降水资料, 分析了东亚副热带夏季风与热带夏季风的区别和联系, 以及两者相互作用问题, 深入讨论了东亚副热带季风的本质。分析发现东亚副热带夏季风建立早于热带夏季风, 于3月中旬已经开始建立。两者是相互独立的两个过程, 前者并非是后者向北推进的结果;相反, 前者建立后的突然南压有利于后者的爆发。副热带夏季风为渐进式建立, 但撤退迅速;热带夏季风爆发突然, 但撤退缓慢。副热带夏季风的建立以偏南风的建立为特征, 而热带夏季风的建立以偏东风向偏西风转变为特征。热带夏季风的建立时间取决于经向海陆热力差异转向, 而东亚副热带夏季风则更依赖于纬向海陆热力差异的逆转。亚洲大陆（含青藏高原）与西太平洋之间的纬向海陆热力差异的季节逆转无论对东亚副热带夏季风还是热带夏季风均有重要作用。     

东亚季风研究的进展

中国气象科学研究院曾长期组织和从事东亚季风及其对中国天气和旱涝影响的研究。该文对中国气象科学研究院在东亚季风研究方面取得成果进行综述, 并回顾了20世纪50年代以来国内有关季风的研究活动, 也回顾了影响我国天气气候、东亚季风环流系统的提出及其后续的有关东亚和印度季风系统的相互作用, 引发中国大陆暴雨生成的水汽输送, 表达中国大陆季风活动的季风指数设计等研究结果。综述了南海夏季风爆发、梅雨开始、中国雨季开始及传播等有关研究成果; 东亚季风系统中副热带地区低频振荡纬向和经向传播特征及与赤道地区不同之处, 东亚低频振荡对El Niño形成及夏季东亚热带和副热带季风爆发的可能影响, 东亚热带和副热带季风低频振荡对中国天气气候的影响等有关成果; 亚洲地区大气热源的计算及其分布, 青藏高原夏季热源对东亚夏季风及降水的可能影响, 青藏高原冬季冷源对El Niño生成的可能影响等有关成果; 东亚季风及降水的年际变化特征, 准4年年际振荡的分析及与ENSO形成间的相互作用, 极地对东亚夏季降水的影响及东亚季风年代际变化特征等成果。综述东亚季风系统形成的可能机制, 特别是亚洲大陆—西太平洋海陆热力差异及非洲、印度半岛、中南半岛及澳大利亚陆地与周围海洋对冬夏季风形成、印度和东亚季风系统形成、南海夏季风形成作用的结果。     

南亚地区黑碳气溶胶对亚洲夏季风的影响

利用NCAR的全球大气模式CAM3,模拟了南亚地区黑碳气溶胶对亚洲夏季风的影响.结果表明:晚春时期,南亚地区黑碳气溶胶强烈吸收太阳辐射,加热低层大气,造成孟加拉湾及沿岸地区雨季的提前,可能导致南亚夏季风提前爆发.夏季,被加热的大气沿青藏高原南坡爬升,在高空形成一个稳定的加热层.高空的持续加热,引起局地的深对流活动,使得印度洋和南亚大陆之间产生一个北升南降的经圈环流,导致印度洋洋面上的向北运动加强,从而使南亚夏季风的强度增大.但是,南亚地区黑碳气溶胶通过影响表面气压、垂直运动、降水和850 hPa风场等减弱了东亚夏季风,且导致西太平洋副热带高压北移西伸,使我国梅雨带位置向东北方向移动.     

Regional water temperature characteristics of lakes subjected to climate change

A deterministic, validated, one-dimensional, unsteady-state lake water quality model was linked to a daily weather data base to simulate daily water temperature profiles in lakes over a period of twenty-five (1955–79) years. Twenty seven classes of lakes which are characteristic for the north-central U.S. were investigated. Output from a global climate model (GISS) was used to modify the weather data base to account for a doubling of atmospheric CO₂. The simulations predict that, after climate change, epilimnetic temperatures will be higher but increase less than air temperature, hypolimnetic temperatures in seasonally stratified dimictic lakes will be largely unchanged or even lower than at present, evaporative water loss will be increased by as much as 300 mm for the season, onset of stratification will occur earlier and overturn later in the season, and overall lake stability will become greater in spring and summer.     

人为气溶胶的直接辐射效应及其对南亚冬季风的影响

运用区域气候模式RegCM4.0(Regional Climate Model Verson 4.0)耦合入一个化学过程,对硫酸盐、黑碳、有机碳这3种人为气溶胶的时空分布特征和直接辐射效应进行了数值模拟,进而研究了气溶胶对南亚冬季风的影响。结果表明:光学厚度和地表短波辐射强迫的时空变化可能主要受硫酸盐气溶胶的影响。在南亚夏季风向冬季风转换时期和南亚冬季风盛行时期,大气层顶和地表的负短波辐射强迫分布与气溶胶分布基本一致,地表辐射强迫强度绝对值比大气层顶辐射强迫强度绝对值大得多。相关分析和合成分析表明:在南亚夏季风向冬季风转换时期和南亚冬季风盛行时期,南亚人为气溶胶主要分布区中的气溶胶柱浓度含量与南亚冬季风的建立和强度有反相关关系。这与气溶胶吸收太阳辐射,从而引起气温和位势高度的变化有关。     

Shifts in the thermal niche of almond under climate change

Delineating geographic shifts in crop cultivation under future climate conditions provides information for land use and water management planning, and insights to meeting future demand. A suitability modeling approach was used to map the thermal niche of almond cultivation and phenological development across the Western United States (US) through the mid-21st century. The Central Valley of California remains thermally suitable for almond cultivation through the mid-21st century, and opportunities for expansion appear in the Willamette Valley of western Oregon, which is currently limited by insufficient heat accumulation. Modeled almond phenology shows a compression in reproductive development under future climate. By the mid-21st century, almond phenology in the Central Valley showed ~?2-week delay in chill accumulation and ~?1- and ~?2.5-week advance in the timing of bloom and harvest, respectively. Although other climatic and non-climatic restrictions to almond cultivation may exist, these results highlight opportunities for shifts in the geography of high-value cropping systems, which may influence growers’ long-term land use decisions, and shape regional water and agricultural industry discussions regarding climate change adaptation options.     

东亚季风区夏季陆地生态系统碳循环对东亚夏季风的响应

东亚地区陆地生态系统的时空变率表现出明显的对季风气候的响应特征。使用EOF（经验正交分解）方法分析了AVIM2动态植被陆面模式离线模拟试验模拟的1953～2004年东亚季风区夏季陆地生态系统总初级生产力（GPP）、生态系统净初级生产力（NPP）、净生态系统初级生产力（NEP）、植被呼吸以及土壤呼吸的时空分布特点,探讨了东亚夏季风对陆地生态系统碳循环影响机制。研究发现,在强季风年,江淮地区高温少雨的特点限制了光合作用,造成GPP偏低;而华南地区在强季风年气候温暖湿润,利于植被生长,GPP偏高。季风对于植被呼吸和土壤呼吸影响不明显,使得GPP和植被呼吸之差NPP的变化及NPP和土壤呼吸之差NEP的变化与GPP的变化保持一致。在强季风年江淮流域地区干热的气候条件使得NPP和NEP降低;但是在华南地区温度升高的同时降水增多使得在NPP偏高的基础上NEP也偏高。     

Impact of Different East Asian Summer Monsoon Circulations on Aerosol-Induced Climatic Effects

The different spatial distributions of aerosol-induced direct radiative forcing and climatic effects in a weak(2003)and a strong(2006)East Asian summer monsoon(EASM)circulation were simulated using a high-resolution regional climate model(RegCM3).Results showed that the atmospheric circulations of summer monsoon have direct relations with transport of aerosols and their climatic effects.Both the top-of-the-atmosphere(TOA)and the surface-negative radiative forcing of aerosols were stronger in weak EASM circulations.The main difference in aerosol-induced negative forcing in two summers varied between 2 and 14 W m 2from the Sichuan Basin to North China,where a maximum in aerosol-induced negative forcing was also noticed in the EASM-dominated areas.The spatial difference in the simulated aerosol optical depth(AOD)in two summers generally showed the similar pictures.Surface cooling effects induced by aerosols were spatially more uniform in weak EASM circulations and cooler by about 1–4.5 C.A preliminary analysis here indicated that a weaker low-level wind speed not conducive to the transport and diffusion of aerosols could make more contributions to the differences in the two circulations.     

An East Asian Monsoon in the Mid-Pliocene

In this study, the authors simulate the East Asian climate changes in the mid-Pliocene (～3.3 to 3.0 Ma BP) with the Community Atmosphere Model version 3.1 (CAM3.1) and compare the simulated East Asian monsoon with paleoclimate data. The simulations show an obvious warming pattern in East Asia in the mid-Pliocene compared with the pre-industrial climate, with surface air temperature increasing by 0.5 4.0°C. In the warm mid-Pliocene simulation, the East Asian Summer Monsoon (EASM) becomes stronger, while the East Asian Winter Monsoon (EAWM) is similar relative to the pre-industrial climate. Compared with the paleoclimate data, our simulations depict the intensified EASM well but cannot reproduce the weakened EAWM. This model-data discrepancy may be attributed to the uncertainty in the reconstructed mid-Pliocene sea surface temperature.     

东亚季风近几十年来的主要变化特征

本文简要综述了关于东亚夏季风和冬季风近几十年来的主要变化特征的若干研究结果,特别是关于其年代际变化方面.夏季风及夏季气候的主要变化特征有:1970年代末之后东亚夏季风的年代际时间尺度的减弱以及相应的我国夏季降水江淮流域增多而华北减少、1992年之后我国华南夏季降水增多、1999年之后我国长江中下游夏季降水减少而淮河流域夏季降水增多、东亚夏季风和ENSO之间的年际变化相关性存在不稳定性.而关于东亚冬季风与冬季气候的主要变化特征有:1980年代中期之后东亚冬季风及其年际变率减弱、1970年代中期之后冬季风和ENSO的年际变化相关性较弱、近年来的北极秋季海冰减少对北半球冬季积雪增多有显著贡献、东北冬季积雪在1980年代中期以后增多.与上述变化有关的极端气候和物候都发生了多方面的变化.     

The response of the South Asian Summer Monsoon circulation to intensified irrigation in global climate model simulations

Agricultural intensification in South Asia has resulted in the expansion and intensification of surface irrigation over the twentieth century. The resulting changes to the surface energy balance could affect the temperature contrasts between the South Asian land surface and the equatorial Indian Ocean, potentially altering the South Asian Summer Monsoon (SASM) circulation. Prior studies have noted apparent declines in the monsoon intensity over the twentieth century and have focused on how altered surface energy balances impact the SASM rainfall distribution. Here, we use the coupled Goddard Institute for Space Studies ModelE-R general circulation model to investigate the impact of intensifying irrigation on the large-scale SASM circulation over the twentieth century, including how the effect of irrigation compares to the impact of increasing greenhouse gas (GHG) forcing. We force our simulations with time-varying, historical estimates of irrigation, both alone and with twentieth century GHGs and other forcings. In the irrigation only experiment, irrigation rates correlate strongly with lower and upper level temperature contrasts between the Indian sub-continent and the Indian Ocean (Pearson’s r = ?0.66 and r = ?0.46, respectively), important quantities that control the strength of the SASM circulation. When GHG forcing is included, these correlations strengthen: r = ?0.72 and r = ?0.47 for lower and upper level temperature contrasts, respectively. Under irrigated conditions, the mean SASM intensity in the model decreases only slightly and insignificantly. However, in the simulation with irrigation and GHG forcing, inter-annual variability of the SASM circulation decreases by ~40 %, consistent with trends in the reanalysis products. This suggests that the inclusion of irrigation may be necessary to accurately simulate the historical trends and variability of the SASM system over the last 50 years. These findings suggest that intensifying irrigation, in concert with increased GHG forcing, is capable of reducing the variability of the simulated SASM circulation and altering the regional moisture transport by limiting the surface warming and reducing land–sea temperature gradients.     

冬季亚洲大陆的热力差异对亚洲季风活动的影响

亚洲冬季地面的热力状况与冬季风活动有关, 对后期的天气气候变化也有重要的作用.作者用EOF方法分析了亚洲冬季地面气温的时空特征, 发现第二模态表明东北亚和南亚地区的地面气温有反相变化的特征并具有明显的年代际变化.进一步研究发现, 这种南亚-东北亚的热力差特征与亚洲夏季风强弱有非常好的对应关系, 籍此定义了一个大陆冬季南亚-东北亚热力差指数.分析表明热力差指数有非常明显的年代际变化, 根据这一特征, 进一步研究了夏季北半球大尺度环流和中国气候的年代际变化, 发现其年代际变化对前冬亚洲大陆热力差指数的年代际特     

青藏高原的热力和动力作用对亚洲季风区环流的影响

利用NCEP/NCAR再分析资料,研究了青藏高原热状况的季节变化、动力和热力作用对周围环流,特别是对亚洲热带季风环流的影响。高原对西风带的机械作用在冬季最强,春季次之。冬季的机械作用形成以高原为主,南侧气旋性、北侧反气旋性的"偶极子"偏差环流,它比传统认识的爬坡、绕流的影响范围大得多,遍及东亚的高、低纬度。随着西风带的北移和高原总加热在4月由负变正,南侧气旋性偏差环流增强并逐渐北移,6月形成气旋盘踞整个高原的夏季型。在高原南侧,高原冬季偶极型、夏季加热的作用导致孟加拉湾地区常年存在印缅槽,使得印度半岛的感热加热始终强于中南半岛,而中南半岛上空的潜热加热大于印度半岛。印缅槽的演变存在明显的半年周期,证明2月初和8月初的较强低压槽分别对应冬季高原最强的动力强迫和夏季高原最强的热力强迫。对低纬经向风场的分析还表明,季风爆发前高原的热力作用尤为重要,是导致江南春雨的形成,亚洲季风最早在孟加拉湾东部爆发,最后在印度半岛爆发的原因。     

地球轨道偏心率变化对东亚季风气候模拟的影响

采用较为真实的椭圆轨道代替了原区域气候模式中的圆近似轨道,并进行了10年模拟试验,用以了解该模式对东亚季风区气候年际变化的模拟能力,同时比较地球轨道参数计算变化对现代东亚季风气候模拟的影响.结果表明:当把模式中的地球轨道计算从圆形改为椭圆时,中国东部的降水模拟有所改进,东亚地区的温度、降水、比湿等气候要素均出现夏季降低(减少)而冬季升高(增加)的季节变化趋势,而且亚洲冬、夏季风也均有减弱.但从总体上说,现代气候状况的模拟对地球公转轨道的计算方案不敏感.通过该工作的模拟研究说明,对较短时期的现代气候模拟,地球公转轨道采用圆近似是可行的.     

气溶胶对东亚冬季风影响的数值模拟

利用NCAR/UCAR CAM5.1模式研究气溶胶对东亚冬季风的影响。模式从1991—2010年运行20年,取2001—2010年冬季的结果。模式结果可以较好地再现东亚冬季风的主要特征。试验结果表明:气溶胶增加使我国东南部地区和东北亚地区（35°~55°N,115°~150°E）冬季风减弱,同时,造成我国东南部地区降水减少。其中,热源热汇的变化和无辐散风减弱为主要原因。气溶胶增加改变了大气热源的分布,造成在我国东南部地区热源减弱,热汇加强;我国东北地区热汇减弱,日本列岛热源加强;气溶胶增加使这些区域全位能的产生减弱,消耗加强。同时,凝结潜热的变化主要影响热源和热汇,其中大尺度过程产生的凝结潜热变化起主要作用。在我国东南部和东北亚地区辐散风动能向全位能的转换增加,造成辐散风减弱。故该区域辐散风向无辐散风的转换减弱,导致无辐散风减弱,最终造成东亚冬季风减弱。     

Reappraisal of Asian Summer Monsoon Indices and the Long-Term Variation of Monsoon

The Webster and Yang monsoon index (WYI)-the zonal wind shear between 850 and 200 hPa was calculated and modified on the basis of NCEP/NCAR reanalysis data. After analyzing the circulation and divergence fields of 150-100 and 200 hPa, however, we found that the 200-hPa level could not reflect the real change of the upper-tropospheric circulation of Asian summer monsoon, especially the characteristics and variation of the tropical easterly jet which is the most important feature of the upper-tropospheric circulation. The zonal wind shear U850-U(150 100) is much larger than U850-U200, and thus it can reflect the strength of monsoon more appropriately. In addition, divergence is the largest at 150 hPa rather than 200 hPa, so 150 hPa in the upper-troposphere can reflect the coupling of the monsoon system. Therefore, WYI is redefined as DHI, i.e., IDH=U850* - U(150 100)*, which is able to characterize the variability of not only the intensity of the center of zonal wind shear in Asia, but also the monsoon system in the upper and lower troposphere. DHI is superior to WYI in featuring the long-term variation of Asian summer monsoon as it indicates there is obvious interdecadal variation in the Asian summer monsoon and the climate abrupt change occurred in 1980. The Asian summer monsoon was stronger before 1980 and it weakened after then due to the weakening of the easterly in the layer of 150-100 hPa, while easterly at 200 hPa did not weaken significantly. After the climate jump year in general, easterly in the upper troposphere weakened in Asia, indicating the weakening of summer monsoon; the land-sea pressure difference and thermal difference reduced, resulting in the weakening of monsoon; the corresponding upper divergence as well as the water vapor transport decreased in Indian Peninsula, central Indo-China Peninsula, North China, and Northeast China, indicating the weakening of summer monsoon as well. The difference between NCEP/NCAR and ERA-40 reanalysis data in studying the intensity and long-term variation of Asian summer monsoon is also compared in the end for reference.     

南亚夏季风爆发的统计动力分析

作者对南亚(印度)夏季风爆发作了统计动力分析,即将南亚夏季风爆发前后的高低层风场看作一个整体,并以南亚夏季风爆发日为基准,作了经验正交函数(矢量)分析,得到了以下结论:偏差风场的第一模态反映了季风爆发前后大规模的风系变化,其时间系数直接体现了南亚夏季风的爆发,在爆发日前后该模态反映的偏差风系有剧烈变化,这表明季风爆发时大气环流有突变发生;第二模态反映了具有5～7天振荡周期的中纬天气尺度波系及其对低纬季风区的影响;第三模态反映了热带、副热带地区呈准双周振荡的低频扰动.     

南半球环流变化对东亚夏季风的影响

南半球环流是影响东亚夏季风季节内、季节到年际变化的重要因子之一.作者系统综述了南半球环流各系统包括连接两半球的越赤道气流、马斯克林高压和澳大利亚高压、南极涛动和南极海冰等对东亚夏季风环流和中国夏季降水的影响.特别是,近年来的研究揭示了南极涛动是影响东亚夏季风年际变化的强信号.当南极涛动偏强时,马斯克林高压和澳大利亚高压和相关的越赤道气流也趋于偏强.同时,西太平洋副热带高压偏西偏南,强度增强,长江流域降水偏多,其两侧降水偏少.这对中国夏季降水的预测有重要的应用价值.最后提出了一些相关的科学问题以供进一步研究.