Steric Sea Level Change in Twentieth Century Historical Climate Simulation and IPCC-RCP8.5 Scenario Projection: A Comparison of Two Versions of FGOALS Model

To reveal the steric sea level change in 20th century historical climate simulations and future climate change projections under the IPCC＇s Representative Concentration Pathway 8.5 （RCP8.5） scenario, the results of two versions of LASG/IAP＇s Flexible Global Ocean-Atmosphere-Land System model （FGOALS） are analyzed. Both models reasonably reproduce the mean dynamic sea level features, with a spatial pattern correlation coefficient of 0.97 with the observation. Characteristics of steric sea level changes in the 20th century historical climate simulations and RCPS.5 scenario projections are investigated. The results show that, in the 20th century, negative trends covered most parts of the global ocean. Under the RCPS.5 scenario, global-averaged steric sea level exhibits a pronounced rising trend throughout the 21st century and the general rising trend appears in most parts of the global ocean. The magnitude of the changes in the 21st century is much larger than that in the 20th century. By the year 2100, the global-averaged steric sea level anomaly is 18 cm and 10 cm relative to the year 1850 in the second spectral version of FGOALS （FGOALS-s2） and the second grid-point version of FGOALS （FGOALS-g2）, respectively. The separate contribution of the thermosteric and halosteric components from various ocean layers is further evaluated. In the 20th century, the steric sea level changes in FGOALS-s2 （FGOALS-g2） are largely attributed to the thermosteric （halosteric） component relative to the pre-industrial control run. In contrast, in the 21st century, the thermosteric component, mainly from the upper 1000 m, dominates the steric sea level change in both models under the RCPS.5 scenario. In addition, the steric sea level change in the marginal sea of China is attributed to the thermosteric component.

Evaluation and Projection of Temperature Extremes over China Based on CMIP5 Model

Evaluation and projection of temperature extremes over China are carried out with 8 model datasets from CMIF5. Compared with the NCEP reanalysis data, multi-model weighted ensemble is capable of reproducing the 8 temperature extreme indices and 20-yeax return values of annual maximum/minimum temperatures. The time correlation coefficients of all the 8 indices between multi-model ensemble and the reanalysis can reach a significance level of 0.10. The spatial correlation coefficient of 20-year return level of annual maximum/minimum temperatures is greater than 0.98. Under the RCP4.5 scenario, more extreme warm events and less cold events are expected over China in multi-model ensemble. By the middle of the 21st century, the heat wave duration index will be multiplied 2.6 times. At the end of the 21st century, the cold wave duration index will decrease 71%, and the 20-year return value will increase 4℃ in parts of China for the maximum/minimum temperatures.

Prediction of meteorological drought in arid and semi-arid regions using PDSI and SDSM: a case study in Fars Province, Iran

Drought is one of the most significant environmental disasters,especially in arid and semi-arid regions.Drought indices as a tool for management practices seeking to deal with the drought phenomenon are widely used around the world.One of these indicators is the Palmer drought severity index(PDSI),which is used in many parts of the world to assess the drought situation and continuation.In this study,the drought state of Fars Province in Iran was evaluated by using the PDSI over 1995-2014 according to meteorological data from six weather stations in the province.A statistical downscaling model(SDSM)was used to apply the output results of the general circulation model in Fars Province.To implement data processing and prediction of climate data,a statistical period 1995-2014 was considered as the monitoring period,and a statistical period 2019-2048 was for the prediction period.The results revealed that there is a good agreement between the simulated precipitation(R2>0.63;R2,determination coefficient;MAE<0.52;MAE,mean absolute error;RMSE<0.56;RMSE,Root Mean Squared Error)and temperature(R2>0.95,MAE<1.74,and RMSE<1.78)with the observed data from the stations.The results of the drought monitoring model presented that dry periods would increase over the next three decades as compared to the historical data.The studies showed the highest drought in the meteorological stations Abadeh and Lar during the prediction period under two future scenarios representative concentration pathways(RCP4.5 and RCP8.5).According to the results of the validation periods and efficiency criteria,we suggest that the SDSM is a proper tool for predicting drought in arid and semi-arid regions.

Projected Changes of Palmer Drought Severity Index under an RCP8.5 Scenario

The potential change of drought measured by the Palmer Drought Severity Index （PDSI） is projected by using a coupled climate system model under a Representative Pathway 8.5 （RCP8.5） scenario.The PDSI changes calculated by two potential evapotranspiration algorithms are compared.The algorithm of Thomthwaite equation overestimates the impact of surface temperature on evaporation and leads to an unrealistic increasing of drought frequency.The PM algorithm based on the Penman-Monteith equation is physically reasonably and necessary for climate change projections.The Flexible Global Ocean-Atmosphere-Land System model,Spectral Version 2 （FGOALS-s2） projects an increasing trend of drought during 2051-2100 in tropical and subtropical areas of North and South America,North Africa,South Europe,Southeast Asia,and the Australian continent.Both the moderate drought （PDSI ＜-2） and extreme drought （PDSI ＜-4） areas show statistically significant increasing trends under an RCP8.5 scenario.The uncertainty in the model projection is also discussed.

Projected changes in summer water vapor transport over East Asia under the 1.5°C and 2.0°C global warming targets

This study investigates changes in summer water vapor transport(WVT) over East Asia under 1.5°C and 2.0°C global warming(GW) for the +4.5 and +8.5 W m-2 Representative Concentration Pathway(RCP) scenarios(RCP4.5 and RCP8.5, respectively). Of the 27 models used, 18 show better skill in simulating the climatological summer WVT over East Asia of the present day. Of those 18, 13 reach 1.5°C and 2.0°C GW for the two RCPs. Based on these 13 models, results show that — relative to the present day-th e summer WVT is enhanced over East Asia under 1.5°C and 2.0°C GW for RCP4.5 and RCP8.5. The inte r-model consistency is higher under 2.0°C GW. Increased water vapor content favors the enhanced WVT over both southern and northern East Asia, while lower-level circulation contributes to the enhanced WVT over southern East Asia. Compared to 1.5°C GW, th e summer WVT under 2.0°C GW is further enhanced over most of East Asia for RCP4.5. For RCP8.5, the summer WVT is also further enhanced over southern East Asia, while this is not the case over northern East Asia. Under the additional 0.5°C GW, the changes in summer WVT, with low in ter-model consistency, are closely related to anomalous lower-level circulation. Precipitation increases over the East China Sea to southern Japan, the Korean Peninsula, and North China, for both RCP4.5 and RCP8.5. However, the changes in precipitation over the South China Sea and Northeast China are different for the two RCPs. This is connected to the difference in the changes of WVT divergence.

Climate Services Elaboration for Cocoa Cultivation in Côte d’Ivoire: Contribution of CORDEX Climate Projections

This study assessed the contribution of climate projections to improving rainfall information for cocoa crops in the central and southern regions of Côte d’Ivoire. Particular attention was paid to fourteen localities in these two climatic zones. Simulation data were obtained from the CORDEX ensemble and observation data from CHIRPS. They cover the period 1991-2005 for the reference period and the future period from 2021 to 2050 for the RCP4.5 and RCP8.5 scenarios. In addition, the study was based on the water requirements necessary during the critical phase of the cocoa tree (the flowering phase) for a good yield from the cocoa production chain on the one hand, and on a selection of three climate indices CDD, CWD and r95PTOT to study their spatio-temporal changes over two future periods 2021-2035 (near future) and 2036-2050 (medium-term) on the other. These climatic indices influence cocoa cultivation and their use in studies of climatic impacts on agriculture is of prime importance. The analysis of their spatio-temporal changes in this work also contributes to providing climate services based on rainfall, to which cocoa crops are highly sensitive. Our results show that the CDD and CWD indices vary from one region to another depending on latitude. For the fourteen localities studied, the number of consecutive dry days (CDD) could increase between now and 2050, while the number of consecutive wet days (CWD) could decrease over the period 2021-2035 and then increase over the period 2036-2050. The localities of Tabou, Aboisso and San-Pedro record high numbers of CDD index and CWD index for both projection scenarios. In comparison with the RCP4.5 and RCP8.5 scenarios, these results show that the RCP8.5 scenarios are having an impact on cocoa growing in Côte d’Ivoire.

气候模拟数据订正方法在作物气候生产潜力预估中的应用——以江苏冬小麦为例

利用全球气候模式BCC_CSM1.1(Beijing Climate Center Climate System Model version 1.1),耦合区域气候模式Reg CM4(Regional Climate Model version 4)输出的1961-1990年(基准时段)气候模拟数据,并根据同期实测资料,确定模拟值和实测值之间的非线性传递函数与方差订正参数,构建气候模拟数据的误差订正模型。利用1991-2005年(验证时段)模拟数据与实测资料验证该模型的有效性,并对RCP(Representative Concentration Pathway)情景下2021-2050年(未来时段)气候模拟数据进行订正,同时通过潜力衰减方法预估未来江苏冬小麦气候生产潜力格局。结果表明:将气候模拟数据订正方法应用到作物气候生产潜力预估是有效的。以均值传递函数和方差信息建立的模型可以较好订正江苏逐日气候模拟数据。订正后的秋冬季气温、辐射量、蒸散量和冬春季降水量模拟偏差明显减小。在此基础上研究发现,冬小麦的成熟期在RCP4.5和RCP8.5情景下介于153~175和153~174,较基准时段均明显提前。两种情景下冬小麦气候生产潜力分别介于10335~14368kg·hm^(-2)和9991~13708kg·hm^(-2),较基准时段呈下降趋势。其变异系数分别介于7.6%~14.6%和7.5%~13.6%,较基准时段呈增大趋势,表明江苏冬小麦气候生产潜力总体趋于不稳定。未来时段,徐州中北部、连云港东北部、宿迁西部以及盐城东南部冬小麦在RCP4.5和RCP8.5情景下可以保持相对较高的生产潜力(≥12501kg·hm^(-2)),该省应确保这些地区的冬小麦种植用地。研究建议,作物气候生产潜力预估应考虑利用研究区实测资料对气候模拟数据进行订正,以提高预估可信度。

江苏省农业气候资源及未来情景预估

利用江苏省60个气象台站1961-2012年地面气象观测资料与Reg CM4.0区域气候模式模拟的RCP4.5和RCP8.5排放情景下数据,分析江苏省近52年的农业气候资源的变化趋势并预估未来时段(2015-2050)光、温、水等农业气候资源的变化特征。结果表明:近52年,太阳总辐射呈下降趋势,变化率为-2.78 MJ/m2,≥0℃活动积温呈上升趋势,气候倾向率变化为每10年89℃,降水量和参考作物蒸散量年际波动明显,其中1970s的平均降水量和1980s的平均参考作物蒸散量最少。与基准气候相比(1961-2005年),未来2种气候情景下≥0℃活动积温、太阳总辐射均呈递增趋势;全省大部分地区降水量在RCP4.5情景下呈现递增趋势,RCP8.5情景下呈现递减趋势,参考作物蒸散量在2种情景下大体变化趋势一致,2种情景下水分盈亏差异较大,其中RCP8.5情景下苏北地区水分短缺显著。研究结果可为江苏省农业气候资源利用、农业生产和布局提供科学指导。

中、高温室气体排放情景下2069~2098年中国冬小麦气候适宜种植分区对比

基于温度、降水、光照等指标,通过利用区域气候模式所预估的分辨率为1°(纬度)×1°(经度)的未来气候预估数据,对1981~2005年的基准期和RCP4.5、RCP8.5两排放情景下2069~2098年中国热量资源以及冬小麦种植界限、理论生育期和气候适宜种植分区的空间分布特征进行了对比分析。研究主要结论为:与基准期相比,两未来气候变化情景下我国热量资源、冬小麦种植条件与气候适宜性差异显著。且相比于RCP4.5情景,在RCP8.5情景下中国2069~2098年多数地区热量资源增加、冬小麦种植北界和南界北移东扩、可种植面积扩大,多数区域理论适宜播种期推迟、理论成熟期提前、潜在生长季缩短,且潜在生长季内的光—温—水配置使得冬小麦气候适宜性有所提高。但由于冬小麦为喜凉作物,对高温胁迫非常敏感,RCP8.5情景下更多的极端高温天气和不对称增温等因素带来的负面影响很可能抵消前述光—温—水配置所带来的有利影响,从而降低冬小麦的种植适宜性。因此,未来研究工作仍应致力于减缓气候变化,以保障我国粮食生产的安全。

Projected Flood Risks in China Based on CMIP5

Based on the simulations of 22 CMIP5 models in combination with socio-economic data and terrain elevation data,the spatial distribution of risk levels of flood disaster and the vulnerability to flood hazards in China are projected under the RCP8.5 for the near term period(2016–2035), medium term period(2046–2065) and long term period(2080–2099),respectively. The results show that regions with high flood hazard levels are mainly located in Southeast China, while the vulnerability to flood hazards is high in eastern China. Under the RCP8.5 greenhouse gas emissions scenario, future high flood risk levels will mainly appear in the eastern part of Sichuan, in major part of East China, and in the provinces of Hebei, Beijing, and Tianjin. The major cities in Northeast China, some areas in Shaanxi and Shanxi, as well as the coastal areas in southeastern China will also encounter high flood risks. Compared with the baseline period, the regional flood risk levels will increase towards the end of the 21 st century, although the occurrences of floods change little. Due to the coarse resolution of the climate models and the indistinct methodology for determining the weight coefficients,large uncertainty still exists in the projection of flood risks.

Impacts of Climate Change on the Hydrology of a Small Brazilian Headwater Catchment Using the Distributed Hydrology-Soil-Vegetation Model

Climate change is one of the greatest issues for human society. The objective of this study is to assess the impacts of future climate change on seasonal average discharge and monthly water budget in a small headwater catchment, located on the Grande River basin, in Minas Gerais, Brazil. The assessment is carried out using the hydrology model, DHSVM. The atmospheric forcing to drive the Distributed Hydrology-Soil-Vegetation Model (DHSVM) is derived from the downscaling of the HadGEM2-ES projections by the Eta Regional Climate Model, at 5-km high resolution. The projections assume the RCP4.5 and RCP8.5 IPCC AR5 emission scenarios. Baseline period was taken between 1961 and 1990. The projections are assessed in three time slices (2011-2040, 2041-2070 and 2071-2099). The climate change is assessed in time slices of 30 years and in comparison against the baseline period to evaluate the hydrological changes in the catchment. The results showed differences in the hydrological behavior between the emission scenarios and though time slices. Reductions in the magnitude of the seasonal average discharge and monthly water budget may alter the water availability. Under the RCP4.5 scenario, results show greater reductions in the water availability in the first time slice, whereas under RCP8.5 scenario greater reductions are indicated in the third time slice.

Change in Climate Indices Using Bias-Adjusted CMIP5 Models: The Case Study of the Fatick Region, Senegal

This study analyses change in rainfall and temperature indices by 2035 and 2050 in Senegal, with a focus on the Fatick region. These parameters are crucial for understanding the impacts of anthropogenic climate change on some vital socio-economic sectors such as agriculture and water resources in this region. To this end, a multi model ensemble mean of 21 bias-adjusted global climate models participating in CMIP5 has been used. We considered two Representative Concentration Pathways (RCP4.5 and RCP8.5). The results indicate an increase of 0.7&#730;C for maximum and minimum temperature by 2035 compared to the reference period (1976 - 2005). By 2050, an increase of 1.4&#730;C (2&#730;C) is projected for RCP4.5 (RCP8.5). These increases in temperature are statistically significant at the 90% confidence level. Conversely, the mean rainy season length decreases from 95 to 85 days by 2035 and less than 80 days by 2050. These decreases in rainy season length are mainly due to a delayed rainy season onset by 2035 and 2050, with the ensemble mean projecting an onset in the second half of July by 2050 instead of around the middle of June. The changes in both the onset and the length of the rainy season are significant at the 90% confidence level. Our results show a slight decrease in seasonal cumulated total rainfall by 2035 and 2050. However, we note a slight increase in seasonal cumulated extreme rainfall. These future changes in climate indices could induce yield reduction and water resources availability. To reduce yield losses, it would be interesting to adopt longer season varieties and also diversify income-generating activities. Concerning water resources, many actions could be done such as carrying out water retention works, treatment and reuse of non-conforming water for agriculture and livestock to reduce pressure on the resource.

Projected changes in population exposure to extreme heat in China under a RCP8.5 scenario

Overall population exposure is measured by multiplying the annual average number of extremely hot days by the number of people exposed to the resultant heat. Extreme heat is also subdivided into high temperature（HT） and extremely high temperature（EHT） in cases where daily maximum temperature exceeds 35℃ and 40℃, respectively. Chinese population exposure to HT and EHT over four periods in the future（i.e., 2021–2040, 2041–2060, 2060–2081 and 2081–2100） were projected at the grid cell level in this study using daily maximum temperature based on an ensemble mean of 21 global climate models under the RCP8.5 scenario and with a population projection based on the A2 r socio-economic scenario. The relative importance of population and climate as drivers of population exposure was evaluated at different spatial scales including national and meteorological geographical divisions. Results show that, compared with population exposure seen during 1981–2010, the base period, exposure to HT in China is likely to increase by 1.3, 2.0, 3.6, and 5.9 times, respectively, over the four periods, while concomitant exposure to EHT is likely to increase by 2.0, 8.3, 24.2, and 82.7 times, respectively. Data show that population exposure to HT is likely to increase significantly in Jianghuai region, Southwest China and Jianghan region, in particular in North China, Huanghuai region, South China and Jiangnan region. Population exposure to EHT is also likely to increase significantly in Southwest China and Jianghan region, especially in North China, Huanghuai, Jiangnan, and Jianghuai regions. Results reveal that climate is the most important factor driving the level of population exposure in Huanghuai, Jianghuai, Jianghan, and Jiangnan regions, as well as in South and Southwest China, followed by the interactive effect between population and climate. Data show that the climatic factor is also most significant at the national level, followed by the interactive effect between population and climate. The rate of contribution of climate to national-level projected changes in exposure is likely to decrease gradually from ca. 70% to ca. 60%, while the rate of contribution of concurrent changes in both population and climate is likely to increase gradually from ca. 20% to ca. 40% over the four future periods in this analysis.

Cross-shelf carbon transport under different greenhouse gas emission scenarios in the East China Sea during winter

Based on Marx-Planck coupled model simulations and in situ hydrography measurements, the volume transport of ocean currents and associated carbon fluxes across the continental margin from the continental shelf to the deep ocean in the East China Sea during winter are estimated. Because cross-shelf currents in the Yellow and East China seas are much stronger in winter than in other seasons and are subducted into the subsurface Kuroshio, the cross-shelf burial of carbon takes place mainly in winter. The analyses show prominent cross-shelf transports during winter in the Yellow and East China seas, with annual mean offshore transport across a section from Taiwan to Cheju at 3.92 Sv(1 Sv=10~6 m^3 s^(-1)). Net transport across the section was0.82 Sv off the shelf, determined by the difference between Taiwan and Cheju strait transports. Net cross-shelf transports of dissolving inorganic carbon(DIC), dissolved organic carbon(DOC), and particulate organic carbon(POC) in winter were 98, 12,and 0.1 million tons, respectively. Under global greenhouse gas emission reduction(RCP4.5) and continuous increase(RCP8.5)scenarios, this cross-shelf transport has an increasing trend. The transports across the Taiwan-Cheju section in winter are predicted to increase by 0.54 and 0.65 Sv from 2006 to 2099, with rates of increase 15.3% and 19.6%, respectively. Associated with the transport increase, the cross-shelf fluxes of DIC, DOC and POC increase by as much as 15.4–25.2%. Cross-shelf carbon fluxes in the East China Sea during winter are evaluated for the first time under the global warming scenarios, showing the importance of cross-shelf transport in the carbon cycle of the China marginal seas.

不同温室气体排放背景下东海冬季跨陆架碳输运通量

基于马普耦合模式,结合现场水文观测资料,估算了东海冬季跨陆架环流的流量及其向深海大洋的碳输送量.由于黄东海冬季的跨陆架环流强度远大于其他季节,且进入黑潮次表层,因此,黄东海跨陆架埋碳过程主要发生在冬季.分析结果表明,黄东海存在明显的跨陆架输运,其中跨越台湾岛至济州岛一线陆架边缘向外海的年平均水体输送量为3.92Sv(1Sv=10~6m^3s^(-1)),净输送量为向外海0.82Sv,与台湾海峡和济州海峡流量之差相当.冬季,跨陆架向外海的溶解无机碳(DIC)、溶解有机碳(DOC)和颗粒有机碳(POC)的净输运量分别为98、12和0.1百万吨.在全球温室气体减排(RCP4.5)和持续增加(RCP8.5)背景下,该跨陆架输运有不断增强的趋势,其中冬季跨越台湾岛至济州岛一线陆架边缘向外海的流量从2006～2099年分别增加了0.54和0.65Sv,增幅分别达15.3%和19.6%.受其影响,冬季跨陆架向外海的DIC、DOC和POC的输运量增加幅度在15.4～25.2%.本文首次评估了全球变暖背景下的东海冬季跨陆架碳输运量,揭示了跨陆架输运在中国近海碳循环中的重要作用.

基于区域气候模式对未来西北太平洋热带气旋活动的模拟评估

本文将基于 HadGEM2-ES 驱动 PRECIS 的西北太平洋热带气旋数据对未来在 RCP4.5 和 RCP8.5情景下对 2030-2039,2050-2059 以及 2090-2099 三个十年时期内进行数量等进行模拟,总结在将来在碳排放情景下,全球气温升高的背景下西北太平洋热带气旋的变化规律,为之后西北太平洋地区热带气旋的防灾减灾提供一定的帮助。