CMIP5和CMIP6模式在历史试验下对AMO和PDO的模拟评估

利用Hadley中心的观测海温资料,以及耦合模式比较计划的第五阶段和耦合模式比较计划的第六阶段历史试验的模式资料,分析和评估了2个最为重要的年代际尺度模态,北大西洋年代际振荡、太平洋年代际振荡在耦合模式比较计划的第五阶段和耦合模式比较计划的第六阶段中的模拟能力。通过对比多模式集合发现,在空间模态方面,耦合模式比较计划的第五阶段和耦合模式比较计划的第六阶段都能模拟出北大西洋年代际振荡在北大西洋地区的信号,但耦合模式比较计划的第六阶段的模拟更好,对于太平洋年代际振荡模态而言,都能模拟出在北太平洋地区的信号,而太平洋年代际振荡在热带太平洋地区的信号,耦合模式比较计划的第六阶段模拟的振幅明显更接近观测。在周期的模拟方面,耦合模式比较计划的第五阶段和耦合模式比较计划的第六阶段结果相似,都能模拟出北大西洋年代际振荡存在60~70年的周期,以及太平洋年代际振荡存在20年和60~70年的双周期。整体而言,耦合模式比较计划的第六阶段相比于耦合模式比较计划的第五阶段在空间特征模拟方面有一定进步,但是对于周期的模拟能力,没有明显进步。     

Climate change impacts on meteorological drought using SPI and SPEI: case study of Ankara,Turkey

ABSTRACT

Using regionally downscaled and adjusted outputs of three global climate models (GCMs), meteorological drought analysis was accomplished across Ankara, the capital city of Turkey. To this end, standardized precipitation index (SPI) and standardized precipitation evapotranspiration index (SPEI) were projected under (representative concentration pathway) RCP4.5 and RCP8.5 greenhouse gas scenarios. In general, our results show that Ankara experienced six severe and two extreme drought events during the reference period, 1971–2000. However, the projections indicate fewer drought events for the near-future period of 2016–2040, with no potential extreme drought events. While the RCP4.5 scenario showed that dry spells will be dominant in the second half of the near-future period, the RCP8.5 scenario projected that dry spells will be evenly distributed during the entire near-future period.     

CMIP3及CMIP5模式对冬季和春季北极涛动变率模拟的比较

结合NCEP再分析资料,评估了28个参加第五次耦合模式比较计划（CMIP5）的耦合模式对1950-2000年冬、春季北极涛动（AO）变率的模拟能力,并与CMIP3模式模拟结果进行了对比。结果表明,尽管CMIP5模式没能模拟出冬、春季AO指数前30年处于显著的负位相期而后20年处于显著的正位相期的特征,但是基本能够模拟出冬、春季AO指数1950-2000年显著的增强趋势以及振荡周期,多模式集合改进了模拟效果。同样,CMIP3模式没能模拟出冬、春季AO指数前30年处于显著的负位相而后20年处于显著的正位相的特征,而且1950-2000年冬、春季AO指数的增强趋势在CMIP3模式模拟结果中也没有表现出来,多模式集合没有改进模式模拟效果。不仅如此,CMIP3模式对AO指数的长期变化周期模拟不好,只是模拟出了冬季周期为2～3 a的振荡,没有模拟出春季AO指数的4～5 a振荡周期。尽管CMIP5模式对冬、春季AO指数的模拟能力还不够理想,没有完全模拟出AO指数的变化特征,但是相对于CMIP3模式,无论是对AO指数变化趋势的模拟还是对其变化周期的模拟,CMIP5模式都有所提高。     

Evaluation of the carbon sequestration of Zhalong Wetland under climate change

Wetland ecosystems are crucial to the global carbon cycle.In this study,the Zhalong Wetland was investigated.Based on remote sensing and meteorological observation data from 1975–2018 and the downscaled fifth phase of the coupled model intercomparison project (CMIP5) climate projection dataset from 1961–2100,the parameters of a net primary productivity (NPP) climatic potential productivity model were adjusted,and the simulation ability of the CMIP5 coupled models was evaluated.On this basis,we analysed the spatial and temporal variations of land cover types and landscape transformation processes in the Zhalong Nature Reserve over the past 44 years.We also evaluated the influence of climate change on the NPP of the vegetation,microbial heterotrophic respiration (Rh),and net ecosystem productivity (NEP) of the Zhalong Wetland and predicted the carbon sequestration potential of the Zhalong Wetland from 2019–2029 under the representative concentration pathways (RCP) 4.5 and RCP 8.5 scenarios.Our results indicate the following:(1) Herbaceous bog was the primary land cover type of the Zhalong Nature Reserve,occupying an average area of 1168.02±224.05 km~2,equivalent to 51.84%of the total reserve area.(2)Since 1975,the Zhalong Nature Reserve has undergone a dry–wet–dry transformation process.Excluding several wet periods during the mid-1980s to early 1990s,the reserve has remained a dry habitat,with particularly severe conditions from 2000 onwards.(3) The 1975–2018 mean NPP,Rh,and NEP values of the Zhalong Wetland were 500.21±52.76,337.59±10.80,and 162.62±45.56 g C·m~(-2)·a~(-1),respectively,and an evaluation of the carbon balance indicated that the reserve served as a carbon sink.(4) From 1975–2018,NPP showed a significant linear increase,Rh showed a highly significant linear increase,while the increase in the carbon absorption rate was smaller than the increase in the carbon release rate.(5) Variations in NPP and NEP were precipitation-driven,with the correlations of NPP and NEP with annual precipitation and summer precipitation being highly significantly positive(P0.001);variations in Rh were temperature-driven,with the correlations of Rh with the average annual,summer,and autumn temperatures being highly significantly positive (P0.001).The interaction of precipitation and temperature enhances the impact on NPP,Rh and NEP.(6) Under the RCP 4.5 and RCP 8.5 scenarios,the predicted carbon sequestration by the Zhalong Wetland from 2019–2029 was 2.421 (±0.225)×10~(11) g C·a~(-1) and 2.407 (±0.382)×10~(11) g C·a~(-1),respectively,which were both lower than the mean carbon sequestration during the last 44 years (2.467 (±0.950)×10~(11) g C·a~(-1)).Future climate change may negatively contribute to the carbon sequestration potential of the Zhalong Wetland.The results of the present study are significant for enhancing the abilities of integrated eco-meteorological monitoring,evaluation,and early warning systems for wetlands.     

中国东北地区气温变化的模拟评估与未来情景预估

基于RegCM4区域气候模式、CMIP5全球气候模式数据集和中国东北地区162个气象站气温观测资料,采用偏差分析和相关分析评估了RegCM4和CMIP5对东北地区气温的模拟能力,预估了RCP2.6、RCP4.5和RCP8.5排放情景下东北地区未来气温的变化.结果表明:区域模式和全球模式均能较好地再现气温时空变化特征,模...     

Evaluation of the performance of CMIP5 and CMIP6 models in simulating the South Pacific Quadrupole-ENSO relationship

先前的观测研究表明,南太平洋四极子海温模态(SPQ)可以有效地作为ENSO的前兆信号.本文利用20个CMIP6模式及其对应的20个先前的CMIP5模式的工业化前气候模拟试验数据,评估和比较了CMIP6以及CMIP5模式对SPQ与ENSO的关系的模拟能力.结果表明,大多数CMIP5和CMIP6模式可以合理地模拟SPQ的基...     

CMIP5多模式集合对东北三省未来气候变化的预估研究

应用CN05观测资料,以及参与国际耦合模式比较计划第5阶段(CMIP5)中的26个模式,评估了新一代全球气候模式对东北三省气候变化模拟能力并选出4个较优模式,发现经过筛选得出的较优模式集合平均模拟结果的可靠性得到进一步加强,尤其体现在对气温的模拟上.在此基础上着重分析了多模式集合在不同典型浓度路径(RCPs)下对未来气候变化特征的预估.结果表明:21世纪的未来阶段,东北三省将处于显著增温的状态,且RCP8.5情景下的增温速率(0.53℃/10a)明显高于RCP4.5情景下的速率(0.22℃/10a);空间上,北部地区将成为增温幅度最大、增温速率最高的区域.未来降水将会相对增加,但波动较大,21世纪末期RCP4.5和RCP8.5情景下的降水增加幅度分别为11.24%和15.95%;空间上,辽宁省西部地区将成为降水增加最为显著的区域.根据水分盈亏量,21世纪未来阶段,RCP4.5情景下的东北三省绝大多数地区未来将相对变湿,尤其到了中后期;RCP8.5情景下则是中西部地区将相对变干,其余地区则会相对变湿.     

Future river flows and flood extent in the Upper Niger and Inner Niger Delta: GCM-related uncertainty using the CMIP5 ensemble

A semi-distributed hydrological model of the Upper Niger and the Inner Niger Delta is used to investigate the RCP 4.5 scenario for 41 CMIP5 GCMs in the 2050s and 2080s. In percentage terms, the range of change in precipitation is around four times as large as for potential evapotranspiration, which increases for most GCMs over most sub-catchments. Almost equal numbers of sub-catchment–GCM combinations experience positive and negative precipitation change. River discharge changes are equally uncertain. Inter-GCM range in mean discharge exceeds that of precipitation by three times in percentage terms. Declining seasonal flooding within the Inner Delta is dominant; 78 and 68% of GCMs project declines in October and November for the 2050s and 2080s, respectively. The 10- and 90-percentile changes in mean annual peak inundation range from ?6136 km² (?43%) to +987 km² (+7%) for the 2050s and ?6176 km² (?43%) to +1165 km² (+8.2%) for the 2080s.     

Estimating present climate in a warming world: a model-based approach

Weather services base their operational definitions of “present” climate on past observations, using a 30-year normal period such as 1961–1990 or 1971–2000. In a world with ongoing global warming, however, past data give a biased estimate of the actual present-day climate. Here we propose to correct this bias with a “delta change” method, in which model-simulated climate changes and observed global mean temperature changes are used to extrapolate past observations forward in time, to make them representative of present or future climate conditions. In a hindcast test for the years 1991–2002, the method works well for temperature, with a clear improvement in verification statistics compared to the case in which the hindcast is formed directly from the observations for 1961–1990. However, no improvement is found for precipitation, for which the signal-to-noise ratio between expected anthropogenic changes and interannual variability is much lower than for temperature. An application of the method to the present (around the year 2007) climate suggests that, as a geographical average over land areas excluding Antarctica, 8–9 months per year and 8–9 years per decade can be expected to be warmer than the median for 1971–2000. Along with the overall warming, a substantial increase in the frequency of warm extremes at the expense of cold extremes of monthly-to-annual temperature is expected.     

CMIP6模式对亚洲中高纬区极端温度变化的模拟及预估

利用观测的亚洲中高纬区逐日最高、最低气温和CMIP6计划中28个全球气候模式资料,系统评估了CMIP6模式对亚洲中高纬区日最高温(TXx)和日最低温(TNn)的模拟性能,并对其未来演变趋势进行了科学预估.主要结论如下:1)CMIP6大部分模式能合理地模拟亚洲中高纬区TXx和TNn自南向北、自西到东逐渐降低的空间分布特征...