CMIP5多模式对阿留申低压气候特征的模拟检验与预估

利用观测的海温资料和海平面气压资料,检验了CMIP5(Coupled Model Intercomparison Project 5,CMIP5)多模式对阿留申低压(Aleutian Low,AL)特征指数的时空分布和变化的模拟能力;从AL周期及变化趋势等方面,分析了CMIP5模式预估的未来AL的变化特征。结果表明,CMIP5模式及其集合平均能够很好地模拟AL的环流结构,对AL的气候态有着较强的模拟能力,尤其是模式对于东太平洋海表温度的模拟能力直接影响其对于AL的模拟效果。模式的集合平均对变率强度的模拟偏强,且对于变率的模拟效果逊于对气候态的模拟。22个模式中的16个模式能模拟出AL强度指数的年代际变化周期,对年代际周期有着较好的刻画能力。Historical试验下对于AL的变化趋势存在着较大的不确定性,而相对于两种不同排放情景,随着排放的增加,AL更加偏北,强度增强,年际、年代际周期变得更加显著。在两种排放情景下模式的集合平均以及多数模式模拟出AL有着向北和增强的趋势。     

气候模式对东北三省降水模拟能力评估及预估

利用CMIP 5全球气候模式、RegCM 4区域气候模式数据集和中国东北三省162个气象站降水观测资料,评估了CMIP 5和RegCM 4模式对中国东北三省降水的模拟能力,并对RCP 4.5和RCP 8.5温室气体排放情景下东北三省未来降水的变化进行了预估。结果表明:CMIP 5和RegCM 4模式均能较好地模拟东北三省年及四季降水量的变化,可再现东北三省降水量由东南向西向北递减的空间分布形势,但模拟的降水中心偏北,模拟的降水强度偏强;两个模式对夏季降水的模拟优于冬季,对冬季降水的模拟存在较大偏差。总体而言,全球气候模式CMIP 5对东北三省降水的模拟结果较好。对东北三省降水量的预估表明,在RCP 4.5和RCP 8.5情景下,全球气候模式CMIP 5预估东北三省年和四季降水量均呈不同程度的增加,其中对冬季降水量预估的偏差百分率增幅最大。在RCP 8.5情景下,东北三省降水量增幅显著,预估未来东北三省降水增加量基本呈由南向北逐步递减的分布,降水偏差百分率基本呈由西南向东北递减的分布。在RCP 4.5情景下,东北三省降水量增幅较小,预估未来东北三省降水量总体呈由东南向西北递减的分布,降水偏差百分率基本呈由西向东递减的分布。     

基于CMIP5和RegCM4模式的内蒙古气候变化模拟评估及未来RCPs情景预估

文章利用CMIP5全球气候模式和RegCM4区域气候模式模拟的内蒙古降水量和平均气温的逐月数据,分别将2个气候模式1961—2005年的模拟结果与实际观测值进行对比,综合评估2个气候模式对内蒙古降水量和平均气温的模拟能力,并预估分析3种RCPs情景下2021—2100年内蒙古未来降水量和平均气温的可能变化特征。结果显示:CMIP5模式对年降水量模拟效果优于RegCM4模式,而RegCM4模式对年平均气温的细节模拟更具有优势,总体上CMIP5模式对内蒙古降水量和平均气温均具有良好的模拟能力。未来80年内蒙古气候呈暖湿变化趋势,其中RCP8.5情景增幅最大,年降水量和年平均气温分别增加了21.6%和5.3℃,RCP4.5情景次之,RCP2.6情景增加趋势不明显。四季和各年代的降水量和平均气温也一致呈增加趋势,其中冬季降水量增幅最大,最大可达22.15%,秋季平均气温在RCP2.6和RCP4.5情景下增幅最大,分别为1.50℃和2.22℃,冬季平均气温在RCP8.5情景下增幅最大,为3.67℃;RCP2.6情景下,年降水量和年平均气温分别在21世纪60年代和40年代增幅最大,分别为8.12%和1.57℃,而RCP4.5和RCP8.5情景下则均在21世纪90年代增加幅度最大,最大分别可达18.52%和5.80℃。     

CMIP5 analysis of the interannual variability of the Pacific SST and its association with the Asian-Pacific oscillation

基于27个CMIP5模式的模拟数据,评估了模式对太平洋海表温度年际变率及其与亚洲-太平洋涛动关系的模拟能力,并预估了其在RCP4.5和RCP8.5情景下的未来变化。评估结果表明,大多数模式和多模式集合能很好的再现观测中北太平洋和热带东太平洋海表温度的强年际变率,其与亚洲-太平洋涛动的同位相和反位相变化关系也能成功模拟出。多模式集合预估显示,与1950-99年相比,2050-99年期间北太平洋和热带东太平洋海表温度的年际变率在RCP4.5和RCP8.5情景下将减弱。大多数模式的预估结果与此相一致。此外,多模式集合预估还表明,当今亚洲-太平洋涛动与北太平洋和热带东太平洋海表温度的年际关系在RCP4.5和RCP8.5情景下仍存在,不过单模式的预估结果具有明显差异。     

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,模式对冬季和夏季的模拟效果优于秋季和春季;在区域尺度信息上,区域模式和全球模式的模拟值均较观测值偏小,RegCM4模式的模拟结果明显优于CMIP5模式,且对模拟的冷偏差有改善。未来东北地区年及四季气温均呈升高趋势,RCP2.6情景下增温相对较小,RCP4.5次之,RCP8.5情景下增温最显著;冬季和秋季气温增幅较大,夏季气温增幅最小;与CMIP5模式相比,RegCM4模式的增温幅度更大,且年际振荡特征更加明显。空间上,区域模式和全球模式预估的近期、中期、末期增温分布格局比较一致,均呈自北向南逐渐减小的纬向分布特征,辽宁地区增温幅度最小,增幅高值区位于黑龙江省大兴安岭地区,虽然北部升温幅度较南部明显,但是升温后未来东北地区的气温分布特征仍是南部气温高于北部。     

8个CMIP5模式对中国极端气温的模拟和预估

利用8个耦合模式比较计划第五阶段（CMIP5）模式结果,采用加权平均方法进行多模式集合,并与NCEP再分析资料进行对比分析,评估了CMIP5模式对中国极端气温的模拟效果,在此基础上,对未来极端气温进行预估。CMIP5模式对中国8个极端气温指数和20年一遇最高（低）气温有模拟能力,所有极端气温指数模拟和观测结果的时间相关均达到0.10显著性水平,20年一遇最高、最低气温模拟和观测结果空间相关系数均超过0.98。在中等排放RCP4.5情景下,未来中国极暖（冷）日数增多（减少）,到21世纪中期热浪指数增加2.6倍,到21世纪末期寒潮指数减少71%,20年一遇最高（低）气温在中国地区均呈现升高趋势,局部升温幅度达到4℃。     

CMIP5模式对中国地区气温模拟能力评估与预估

利用第五次国际耦合模式比较计划（CMIP5）中29个气候模式的气温模拟结果,评估了各模式对中国地区年平均气温的模拟能力,对未来不同典型浓度路径（RCPs）下中国地区气温的可能变化给出了预估。结果表明：各模式能较好地模拟过去100多年中国地区增温趋势和年平均气温的空间分布,从模式间标准差来看,各模式对中国中部、南部气温模拟具有较高的一致性。利用相对均方根误差分析了各模式的模拟能力,对于多时间尺度（月、年）气温的气候平均态,有7个模式表现良好,高于中等水平,5个模式的模拟能力低于中等水平,模式集合平均值的模拟效果优于大多数单个模式。根据29个模式的评估结果,使用模拟性能相对较好的模式分析了未来不同排放情景下中国地区气温变化,21世纪前期,不同排放情景之间的预估结果差别较小,21世纪中期各情景之间的差别逐渐增大,到21世纪后期,3种排放情景的升温差别明显增大。     

不同代表性浓度路径(RCPs)下21世纪长江中下游强降水预估

利用政府间气候变化专门委员会第5次评估报告(IPCC AR5)耦合模式相互比较计划第5阶段(CMIP5)中所包含的8个模式资料,对长江中下游强降水的气候特征在21世纪的变化进行预估,并与此前基于第3阶段(CMIP3)的7个模式的预估结果进行了对比。所用资料既包括模式对20世纪的历史模拟,也包括它们在未来高、中、低三种排放情景(即RCP8.5、RCP4.5、RCP2.6三种代表性浓度路径)下的预估试验资料。结果表明:1)不同模式的预估结果有较好的一致性。相对于20世纪最后20 a(1980—1999年),21世纪不仅强降水事件频次、强降水事件的平均强度增加,且年际变率也有所增强。就增加幅度而言,西部强度较小,东部强度较大。2)就不同排放情景相互比较而言,在低排放情景和高排放情景(RCP2.6和RCP8.5)下,降水强度和频次的增长均比在中等排放情景(RCP4.5)下大。3)与之前CMIP3的结果相比,尽管二者均预估未来降水强度和频次增长,但二者增加幅度的空间分布并不一致。在CMIP5中,表现为自西向东幅度递增的特点,而在CMIP3中则中部地区增幅最大。     

CMIP5耦合模式对北半球3—4月积雪面积的历史模拟和未来预估

基于卫星观测数据,评估了23个CMIP5耦合模式对北半球3—4月积雪面积的模拟能力,在此基础上应用多模式集合平均结果,预估了未来不同温室气体排放情景下北半球3—4月积雪面积的变化情况。结果表明:整体上看,CMIP5耦合模式对北半球3—4月积雪面积具有一定的模拟能力,模式基本能再现北半球3—4月积雪面积的分布特征,但对高原等复杂地形地区积雪的模拟偏差较大并且低估了北半球积雪的减少趋势,这些可能是由卫星资料本身的缺陷以及模式参数化方案的不同造成的。多模式集合预估结果表明,未来几十年北半球3—4月积雪将继续减少并且集中发生在欧亚大陆中西部地区。温室气体排放将会对未来北半球积雪的变化产生显著影响。在RCP8.5情景下,未来北半球积雪减少最显著;在RCP4.5和RCP6.0情景下,在21世纪前半叶北半球积雪减少趋势与RCP8.5情景相当,但是在21世纪后半叶积雪的减少趋势明显小于RCP8.5情景;在RCP2.6情景下,北半球积雪减少趋势最小。所以,控制温室气体排放对于未来北半球积雪的生存至关重要。     

21世纪气候变化情景下环北极地区植被生长季与活动积温变化

基于部门间影响模式比较计划（ISI-MIP, Inter-Sectoral Impact Model Intercomparison Project)对CMIP5中5个气候（地球）系统模式模拟结果的降尺度数据,利用多模式集合预估了气候变化情景下21世纪环北极地区植被生长季与活动积温变化。研究发现:1）多模式集合模拟能够基本再现观测的初、终霜日及无霜期长度与>10°C积温的空间分布特征以及1979～2004年各指标变化趋势的空间分布特征,但其对气候变化年际变率的模拟能力较弱;2）至21世纪末,终霜日最多将提前60 d,初霜日将推迟20～40 d,无霜期延长幅度最高可达100 d,积温将增加1000～1200°C。其中RCP8.5情景下,各指标变幅最大,RCP2.6情景下变幅最小;3）各指标变幅呈现出较大的空间差异,亚欧大陆中西部的变幅普遍较大,随着气候变暖,>10°C积温增加幅度表现出明显的纬度地带性,南部增幅较大,北部增幅较小。     

Simulation and Projection of the Western Pacific Subtropical High in CMIP5 Models

This work examined the performance of 26 coupled climate models participating in the Coupled Model Intercomparison Project Phase 5 （CMIP5） in the simulation of the present-day temporal variability and spatial pattern of the western Pacifi c subtropical high （WPSH）. The results show that most models are able to capture the spatial distribution and variability of the 500-hPa geopotential height and zonal wind fi elds in the western subtropical Pacifi c, but with underestimated mean intensity of the WPSH. The underestimation may be associated with the cold bias of sea surface temperature in the tropical Indian and western Pacifi c oceans in the models. To eliminate the impact of the climatology biases, the climatology of these models is replaced by that of the NCEP/NCAR reanalysis in the verifi cation, and the models reproduce the WPSH’s enhancement and westward extension after the late 1970s. According to assessment of the simulated WPSH indices, it is found that some models （CNRM-CM5, FGOALS-g2, FIO-ESM, MIROC-ESM, and MPI-ESM-P） are better than others in simulating WPSH. Then, the ensemble mean of these better models is used to pro ject the future changes of WPSH under three representative concentration pathway scenarios （RCP8.5, RCP4.5, and RCP2.6）. The WPSH enlarges, strengthens, and extends westward under all the scenarios, with the largest linear growth trend projected in RCP8.5, smallest in RCP2.6, and in between in RCP4.5;while the ridge line of WPSH shows no obvious long-term trend. These results may have implications for the attribution and prediction of climate variations and changes in East Asia.     

Future changes in summer precipitation in regional climate simulations over the Korean Peninsula forced by multi-RCP scenarios of HadGEM2-AO

In this study, the regional climate of the Korean Peninsula (KP) was dynamically downscaled using a high-resolution regional climate model (RCM) forced by multi- representative concentration pathways (RCP) scenarios of HadGEM2-AO, and changes in summer precipitation were investigated. Through the evaluation of the present climate, the RCM reasonably reproduced long-term climatology of summer precipitation over the KP, and captured the sub-seasonal evolution of Changma rain-band. In future projections, all RCP experiments using different RCP radiative forcings (i.e., RCP2.6, RCP4.5, RCP6.0, and RCP8.5 runs) simulated an increased summer precipitation over the KP. However, there were some differences in changing rates of summer precipitation among the RCP experiments. Future increases in summer precipitation were affected by future changes in moisture convergence and surface evaporation. Changing ranges in moisture convergences among RCP experiments were significantly larger than those in surface evaporation. This indicates that the uncertainty of changes in summer precipitation is related to the projection of the monsoon circulation, which determines the moisture convergence field through horizontal advection. Changes in the sub-seasonal evolution of Changma rain-band were inconsistent among RCP experiments. However, all experiments showed that Changma rain-band was enhanced during late June to early July, but it was weakened after mid-July due to the expansion of the western North Pacific subtropical high. These results indicate that precipitation intensity related to Changma rain-band will be increased, but its duration will be reduced in the future.     

CMIP5多模式集合对江苏省气候变化模拟评估及情景预估

利用中国气象局所属的2 400余个台站观测资料制作的分辨率为0.25°×0.25°数据集中的气温、降水量资料评估了CMIP5中17个模式对于1961—2004年江苏省气温和降水量空间分布特征的模拟能力,筛选出了5个对江苏省气候特征模拟较好的模式。之后基于5个优选模式集合平均的结果预估了3种典型浓度路径(Representative Concentration Pathways,RCPs)下江苏省2006—2100年的气温和降水量变化趋势。结果表明:(1)全球耦合气候模式对江苏省的气温和降水量空间分布特征具有一定的模拟能力,并且模式集合平均的气温和降水量与观测资料的空间相关系数分别为0.85和0.93;(2)在低浓度路径(RCP2.6)、中浓度路径(RCP4.5)和高浓度路径(RCP8.5)3种温室气体排放情景下,江苏省2006—2100年的地表温度均呈现明显的增温趋势,并且苏北的增温幅度要高于苏南;(3)3种温室气体排放情景下,江苏省未来百年降水量均呈现出北方增多南方减少的趋势;(4)未来百年江苏省降水量随气温变化的趋势并不稳定,RCP2.6和RCP4.5情景下降水量随气温的升高而增加,而RCP8.5情景下降水量随气温的增加而减少。     

Relationship Between the Western Pacific Subtropical High and the Subtropical East Asian Diabatic Heating During South China Heavy Rains in June 2005

Based on the daily NCEP/NCAR reanalysis data, the position variation of the western Pacific subtropical high (WPSH) in June 2005 and its relation to the diabatic heating in the subtropical East Asia are analyzed using the complete vertical vorticity equation. The results show that the position variation of the WPSH is indeed associated with the diabatic heating in the subtropical East Asian areas. In comparison with June climatology, stronger heating on the north side of the WPSH and relatively weak ITCZ (intertropical convergence zone) convection on the south side of the WPSH occurred in June 2005. Along with the northward movement of the WPSH, the convective latent heating extended northward from the south side of the WPSH. The heating to the west of the WPSH was generally greater than that inside the WPSH, and each significant enhancement of the heating field corresponded to a subsequent westward extension of the WPSH. In the mid troposphere, the vertical variation of heating on the north of the WPSH was greater than the climatology, which is unfavorable for the northward movement of the WPSH. On the other hand, the vertical variation of heating south of the WPSH was largely smaller than the climatology, which is favorable for the anomalous increase of anticyclonic vorticity, leading to the southward retreat of the WPSH. Before the westward extension of the WPSH in late June 2005, the vertical variation of heating rates to (in) the west (east) of the WPSH was largely higher (lower) than the climatology, which is in favor of the increase of anticyclonic (cyclonic) vorticity to (in) the west (east) of the WPSH, inducing the subsequent westward extension of the WPSH. Similar features appeared in the lower troposphere. In a word, the heating on the north-south, east-west of the WPSH worked together, resulting in the WPSH extending more southward and westward in June 2005, which is favorable to the maintenance of the rainbelt in South China.     

“05. 6”华南强降水期间副热带高压活动与加热场的关系

采用NCEP/NCAR再分析逐日资料,根据全型垂直涡度倾向方程,研究2005年6月华南强降水期间西太平洋副热带高压(副高)位置变动特征及其与加热场的关系.结果表明,西太平洋副高位置变化和副热带地区的非绝热加热有密切关系.与气候平均状况相比,2005年6月副高北侧的加热区很强,而南侧赤道辐合带(ITCZ)没有相当强度的对流;伴随着副高北抬,其南侧均有明显的对流潜热加热向北伸展.副高西侧的加热基本上都大于副高纬带内的加热,副高的每一次西伸都伴随着西侧加热的显著增强,并且加热增强先于副高西伸.对流层中层,副高北侧非绝热加热率的垂直变化基本上都大于气候平均值,不利于副高北进;而南侧加热率的垂直变化均小于多年平均,有利于副高南侧反气旋性涡度异常增长,从而有利于副高南退.2005年6月下旬副高西伸之前,副高西侧非绝热加热率的垂直变化基本上都高于气候平均状况,有利于副高两侧反气旋涡度增加,从而诱使副高随后西伸;而东侧加热率的垂直变化大多数时间都低于气候平均状况,使得副高东侧气旋性涡度增加,有利于副高西伸,对流层低层也具有类似特点.因此在南北两侧加热和东西两侧加热的共同作用下,2005年6月副高位置较常年偏南偏西,从而有利于雨带在华南地区维持.     

Projected Climate Change in the Northwestern Arid Regions of China: An Ensemble of Regional Climate Model Simulations

The projected temperature and precipitationchange under different emissions scenarios using Coupled Model Intercomparison Project Phase 5 models over the northwestern arid regions of China(NWAC) were analyzed using the ensemble of three high-resolution dynamical downscaling simulations: the simulation of the Regional Climate Model version 4.0(Reg CM4) forced by the Beijing Climate Center Climate System Model version 1.1(BCC_CSM1.1); the Hadley Centre Global Environmental Model version 3 regional climate model(Had GEM3-RA) forced by the Atmosphere-Ocean coupled Had GEM version 2(Had GEM2-AO); and the Weather Research and Forecasting(WRF) model forced by the Norwegian community Earth System Model(Nor ESM1-M). Model validation indicated that the multimodel simulations reproduce the spatial and temporal distribution of temperature and precipitation well. The temperature is projected to increase over NWAC under both the 4.5 and 8.5 Representative Concentration Pathways scenarios(RCP4.5 and RCP8.5, respectively) in the middle of the 21 st century, but the warming trend is larger under the RCP8.5 scenario. Precipitation shows a significant increasing trend in spring and winter under both RCP4.5 and RCP8.5; but in summer, precipitation is projected to decrease in the Tarim Basin and Junggar Basin. The regional averaged temperature and precipitation show increasing trends in the future over NWAC; meanwhile, the large variability of the winter mean temperature and precipitation may induce more extreme cold events and intense snowfall events in these regions in the future.     

Assessment of future climate change over East Asia due to the RCP scenarios downscaled by GRIMs-RMP

This study assesses future climate change over East Asia using the Global/Regional Integrated Model system—Regional Model Program (RMP). The RMP is forced by two types of future climate scenarios produced by the Hadley Center Global Environmental Model version 2 (HG2); the representative concentration pathways (RCP) 4.5 and 8.5 scenarios for the intergovernmental panel on climate change fifth assessment report (AR5). Analyses for the current (1980–2005) climate are performed to evaluate the RMP’s ability to reproduce precipitation and temperature. Two different future (2006–2050) simulations are compared with the current climatology to investigate the climatic change over East Asia centered in Korea. The RMP satisfactorily reproduces the observed seasonal mean and variation of precipitation and temperature. The spatial distribution of the simulated large-scale features and precipitation by the RMP is generally less reflective of current climatic conditions than that is given by the HG2, but their inter-annual variations in East Asia are better captured by the RMP. Furthermore, the RMP shows higher reproducibility of climate extremes including excessive heat wave and precipitation events over South Korea. In the future, strong warming is distinctly coupled with intensified monsoonal precipitation over East Asia. In particular, extreme weather conditions are increased and intensified over South Korea as follows: (1) The frequency of heat wave events with temperature greater than 30 °C is projected to increase by 131 and 111 % in the RCP 8.5 and 4.5 downscaling, relative to the current climate. (2) The RCP 8.5 downscaling shows the frequency and variability of heavy rainfall to increase by 24 and 31.5 %, respectively, while the statistics given by the RCP 4.5 downscaling are similar to those of the current climate.     

CMIP5模式对冬季北极涛动的模拟和预估

基于NCEP/NCAR再分析资料和CMIP5的19个模式结果,从异常模态、年代际趋势和周期特征等方面评估了CMIP5耦合模式对冬季北极涛动(Arctic Oscillation,AO)的模拟能力,并对未来RCP4.5、RCP8.5两种浓度路径下AO的可能变化趋势给出了定性的预估。CMIP5模式历史试验结果显示,大多数模式都能够模拟出AO模态的基本结构,但是对中心位置、强度的模拟存在较大的偏差,其中MPI-ESM-LR和Had GEM2-AO能较好地模拟出AO整体模态来。在历史演变和周期特征的刻画方面,模式的冬季海平面气压经验正交函数分解第一模态时间序列(Principal Component,PC1)基本能够反映出1950~1970年以来的减弱趋势,但对1970年以后的增长趋势模拟并不明显,而北半球环状模指数(Zonal Index,ZI)序列对两个阶段的趋势均可模拟出来,模式的PC1和ZI序列总体表现为正的变化趋势。有一半以上的模式对2~3 a高频周期模拟较好,但对20 a左右的周期模拟较差,其中仅有Can ESM2、CNRM-CM5、GFDL-ESM2G这3个模式对ZI指数的两个周期变化模拟较好。在RCP4.5和RCP8.5两种浓度路径下,ZI序列有显著的上升趋势,从长期趋势系数看RCP4.5路径下有14个模式呈现正的变化趋势,其中有10个模式通过了检验。RCP8.5浓度路径下,16个模式为正变化趋势,有11个模式通过了检验,集合平均结果正变化趋势较为显著。两种浓度路径下不同时段的海平面气压变化趋势表明,ZI序列的年代际变化明显,存在3个不同的变化阶段——2006~2039年、2070~2100年为两个上升阶段,2040~2069年为缓慢下降阶段。     

How the “best” CMIP5 models project relations of Asian–Pacific Oscillation to circulation backgrounds favorable for tropical cyclone genesis over the western North Pacific

Based on the simulations of 32 models from the Coupled Model Intercomparison Project Phase 5 (CMIP5), the present study assesses their capacity to simulate the relationship of the summer Asian–Pacific Oscillation (APO) with the vertical zonal wind shear, low-level atmospheric vorticity, mid-level humidity, atmospheric divergence in the lower and upper troposphere, and western Pacific subtropical high (WPSH) that are closely associated with the genesis of tropical cyclones over the western North Pacific. The results indicate that five models can simultaneously reproduce the observed pattern with the positive APO phase accompanied by weak vertical zonal wind shear, strengthened vorticity in the lower troposphere, increased mid-level humidity, intensified low-level convergence and high-level divergence, and a northward-located WPSH over the western North Pacific. These five models are further used to project their potential relationship under the RCP8.5 scenario during 2050–2099. Compared to 1950–1999, the relationship between the APO and the vertical zonal wind shear is projected to weaken by both the multi-model ensemble and the individual models. Its linkage to the low-level vorticity, mid-level humidity, atmospheric divergence in the lower and upper troposphere, and the northward–southward movement of the WPSH would also reduce slightly but still be significant. However, the individual models show relatively large differences in projecting the linkage between the APO and the mid-level humidity and low-level divergence.