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1.
The relationship between North Atlantic tropical cyclone (TC) peak intensity and subsurface ocean temperature is investigated in this study using atmospheric and ocean reanalysis data. It is found that the peak intensity of basin-wide strong TCs (Categories 4 and 5) is positively correlated with subsurface ocean temperature in the extratropical North Atlantic. A possible physical mechanism is that subsurface ocean temperature in the extratropical North Atlantic can affect local sea surface temperature (SST); on the other hand, the moisture generated by the warming SST in the extratropical North Atlantic is transported to the main region of TC development in the tropics by a near-surface anticyclonic atmospheric circulation over the tropical North Atlantic, affecting TC peak intensity. Moreover, coastal upwelling off Northwest Africa and southern Europe can affect subsurface ocean temperature in the extratropical North Atlantic. Therefore, the peak intensity of strong TCs is also found to be directly correlated with the water temperature in these two upwelling regions on an interdecadal timescale.摘要利用大气与海洋再分析数据等相关资料, 本项研究发现, 北大西洋强台风 (Saffir–Simpson分类中的第4和第5类) 的最大强度与亚热带北大西洋的次表层海温呈正相关. 由于亚热带北大西洋的次表层海温会影响当地的海表温度, 该地区海面产生的水汽通过近地面的反气旋大气环流可被输送到位于热带的台风主要发展区域, 进而影响台风的最大强度. 与此同时, 位于西非北部和南欧的近岸涌升流会影响亚热带北大西洋的次表层海温. 因此, 强台风的最大强度也被发现与上述两个涌升流区域的海温具有相关性, 但是这种相关性主要体现在年代际时间尺度上.  相似文献   

2.
Using reanalysis data and model simulations, this study reveals an increase in September landfalling North Atlantic tropical cyclones (TCs) during years that have a strengthened Saharan dust plume, and the related physical processes are investigated by analyzing the relationship of dust aerosol optical depth with TC track, intensity, and the related meteorological environment. Suppression of the sea surface temperature (SST) by the Saharan dust plume can hinder TC tracks over the central tropical North Atlantic, inducing westward development of TC tracks to the western tropical North Atlantic with higher SST, which is more conducive to TCs forming major hurricanes. This physical process increases TC landfalls in North America, especially major hurricane landfalls in the continental United States, leading to greater potential destructiveness.摘要本项研究利用再分析数据和模式模拟数据分析了沙尘的气溶胶光学厚度与台风的登陆, 轨迹, 强度及相关气象环境参数的关系, 揭示了9月北大西洋台风的登陆次数会在撒哈拉沙尘较强的年份中增加, 以及这一现象的物理机制. 撒哈拉沙尘对热带北大西洋中部海表温度具有抑制作用, 会阻碍该地区的台风活动, 因此台风只能向西移动进入海表温度较高的热带北大西洋西部, 从而更易于形成强台风. 这一物理过程将导致台风登陆北美大陆的频次增加, 特别是强台风登陆美国的可能性增强, 产生更大的潜在破坏性.  相似文献   

3.
The midwinter suppression of North Pacific storm tracks (NPSTs) reflects that the linear relationship between the NPST and baroclinicity breaks in winter. Based on the reanalysis data during the cold seasons of 1979–2019 and a tracking algorithm, this study analyzes the eddy growth process and shows that an enhanced upper-tropospheric jet favors the generation of upper-level eddies on the northeast side of the Pacific jet, but increasingly suppresses the generation of those in the Northwest Pacific. The upper-level eddies generated upstream of the jet core are unable to grow sufficiently throughout the whole cold season, and only those generated downstream of the jet core can grow normally and constitute the main body of the upper-level NPST. By contrast, the main lower-level eddy genesis area and growth area coincide with the baroclinic zone, with the genesis number and local growth rate increasing with the baroclinicity.摘要北太平洋风暴轴的深冬抑制表明风暴轴强度与斜压性之间的线性关系在冬季破裂. 本研究基于1979–2019年冷季的再分析数据和拉格朗日跟踪算法, 对比分析了高低层扰动的具体生长过程. 结果表明太平洋急流的增强有利于高层扰动在急流核东北侧产生, 但却抑制其在西北太平洋的生成. 在急流核上游产生的高层扰动在整个冷季都无法充分发展, 只有在急流核下游产生的高层扰动才能正常生长且它们是构成高层太平洋风暴轴的主体. 相比之下, 低层扰动的生成区和生长区都与斜压区重合, 并且它们的生成数量和局部增长率随着斜压性的增强而增强.  相似文献   

4.
This study investigates the variability of annual tropical cyclone (TC) frequency and intensity over six major ocean basins from 1980 to 2021. Statistical change-point and trend analyses were performed on the TC time series to detect significant decadal variation in TC activities. In the middle of the last decade of the 20th century, the frequency of TC genesis in the North Atlantic basin (NA) and North Indian Ocean (NIO) increased dramatically. In contrast, the frequency in the western North Pacific (WNP) decreased significantly at the end of the century. The other three basins—the East Pacific, southern Indian, and South Pacific—all experienced a declining trend in annual TC frequency. Over recent decades, the average TC intensity has decreased in the East Pacific and the NA, whereas it has risen in the other ocean basins. Specifically, from 2013 to 2021, the average peak TC intensity in the NIO has enhanced significantly. The magnitude of the Genesis Potential Index exhibits fluctuation that is consistent with large-scale parameters in the NIO, NA, and WNP, emphasizing the enhancing and declining trends in TCs. In addition, a trend and correlation analysis of the averaged large-scale characteristics with TCs revealed significant associations between the vertical wind shear and TC frequency over the NIO, NA, and WNP. Therefore, global TC trends and decadal variations associated with environmental parameters deserve further investigation in the future, mainly linked to the significant climate modes.摘要研究发现在1980–2021期间全球6个海域每年热带气旋的发生频次和强度具有显著年代际变化规律, 最近几十年, 北大西洋和北印度洋的热带气旋发生频次明显增加, 但西北太平洋的热带气旋却显著下降. 另外三个海域, 东太平洋, 南印度洋和南太平洋发现所生成的热带气旋有减少趋势. 但在过去十几年, 平均热带气旋的强度除了在东太平洋和北大西洋有所减弱但在其他几个海域有所加强, 特别是在 2013–2021期间, 北印度洋的平均热带气旋的强度增强明显. 热带气旋的潜在生成指数 (GPI) 增加或减少趋势变化与北印度洋, 北大西洋和西太平洋热带气旋变化相关的大尺度环流一致. 另外, 北印度洋, 北大西洋和西太平洋上空的垂直风切变是影响其区域热带气旋发生频次变化的主要因子, 不同的气候模态也可能对全球热带气旋的趋势变化和年代际变化有影响, 值得进一步研究.  相似文献   

5.
应用常规资料、自动站雨量资料、卫星云图及雷达资料,对2009年5月9-10日发生在鲁西北和鲁中北部的一次区域性大暴雨进行分析。分析发现,低层冷式切变线是引发大暴雨的主要系统,暴雨主要产生在低空冷式切变线右侧、西南低涡的东北象限以及低空急流的左前方,也是高低空急流耦合区。副高西侧的西南急流建立起从南海到华北中部的水汽通道,为大暴雨的发生发展提供暖湿空气和能量,使得低涡辐合加强,是低层切变线长时间停滞的必要条件。地面锋面气旋则是暴雨开始的启动机制,锋后东北冷空气与西南暖湿空气在山东上空交汇,促使对流发展和不稳定能量释放产生暴雨。在低层辐合、高层弱辐散的情况下,暴雨区低涡的涡动作用使得水汽块运动加强。多个对流单体合并形成的中尺度对流系统(MCS)经过大暴雨区,雷达回波表现为层状云为主的混合回波带,说明对流并不旺盛。  相似文献   

6.
Northeast China (NEC) witnessed an interdecadal increase in summer extreme heat days (EHDs) around the mid-1990s. The current study reveals that this interdecadal increase only occurs in June and July, while August features a unique interdecadal decrease in EHDs around the early 1990s. Plausible reasons for the interdecadal decrease in EHDs in August are further investigated. Results show that the interdecadal decrease in EHDs in August is due to the deceased variability of daily maximum temperature (Tmax). Overall, the variation of the Tmax over NEC in August is modulated by the Eurasian teleconnection pattern, Silk Road pattern, and East Asia–Pacific pattern. However, the influence of the Silk Road pattern dramatically weakens after the early 1990s because the meridional wind variability along the westerly jet significantly decreases. The weakened influence of the Silk Road pattern contributes to the decreased Tmax variability over NEC. Meanwhile, the convection over the western North Pacific, which accompanies the East Asia–Pacific pattern, presents a significant decrease in variance after the early 1990s, further decreasing the Tmax variability over NEC.摘要东北夏季极端高温频次在1990年代中期出现年代际增多.本文指出该年代际增多只出现在6–7月, 而8月则呈现特殊性, 即在1990年代初出现年代际减少.进一步分析表明, 东北8月极端高温频次的年代际减少由日最高温度变率的年代际减小造成.东北日最高温度受到欧亚遥相关,丝绸之路遥相关和东亚-太平洋遥相关的共同调制.1990年代初之后, 西风急流上的经向风变率显著减小, 丝绸之路遥相关对下游的影响减弱, 导致东北日最高温度变率减小.同时, 西北太平洋热带对流的变率也在1990年代初出现年代际减小, 通过东亚-太平洋遥相关使东北日最高温度变率进一步减小.  相似文献   

7.
北美偶极子(NAD)是热带北大西洋西部和北美东北部的南北向海平面气压异常偶极型模态.以往的观测研究表明,NAD可以有效地影响ENSO事件的爆发.本文利用全球耦合模式FGOALS-g2,评估了NAD与ENSO的关系.结果表明,该模式能较好地重现NAD模态.进一步的分析验证了冬季NAD可以通过强迫冬末春初副热带东北太平洋上空的反气旋和暖海温的出现,在随后的冬季触发El Ni?o事件.此外,在同化NAD实验中,发生El Ni?o事件的概率增加了将近一倍.相比之下,NAO未能在副热带东北太平洋上空引起表面风和海温的异常,因而不能有效地激发次年冬季ENSO事件.  相似文献   

8.
In this study, the relationship of tropical cyclone (TC) size change rate (SCR), within 24 hours, with size, intensity, and intensity change rate (ICR) are explored over the western North Pacific. TC size is defined as the azimuthally averaged radius of gale-force wind of 17 m s−1 (R17) based on the Multiplatform Tropical Cyclone Surface Winds Analysis data. The majority of SCRs are mainly distributed in the range from −20 to 80 km d−1. The correlation coefficients between SCR and size (SCR-R17), intensity, and ICR (SCR-ICR) are −0.43, −0.12, and 0.25, respectively. The sensitivity of the SCR-R17 and SCR-ICR relationships to size, intensity, and evolution stage are further examined. Results show that the SCR-R17 relationship is more sensitive to variations of size and evolution stage than that of intensity. The relationship of SCR-ICR is largely modulated by the evolution stage. The correlation coefficient of SCR-ICR can increase from 0.25 to 0.40 when only considering the lifetime stages concurrently before and after the lifetime maximum size (LMS) and lifetime maximum intensity. This demonstrates that ICR is a potential factor in predicting SCR during these evolution stages. Besides, the TC size expansion (shrinkage) is more likely to occur for TCs with smaller (larger) size and weaker (stronger) intensity. The complexity of size change during a TC's lifetime can be attributed to the fact that shrinkage or expansion could occur both before and after LMS.摘要为了进一步了解热带气旋 (TC) 尺度变化与其结构的相关关系, 本文基于多平台热带气旋表面风场资料, 通过相关分析得出西北太平洋上TC的24 h尺度变化率(SCR)与其尺度,强度以及强度变化率 (ICR) 的相关系数分别为–0.43, –0.12, 0.25.其中SCR-ICR的相关关系主要受不同发展阶段的影响, 在TC均达到/均未达到最大尺度和最强强度的阶段中, SCR-ICR的相关系数上升至0.40, 表明在这些阶段中ICR是预报SCR的潜在因子之一.当TC尺度较小 (大) 和强度较弱 (强) 时其尺度更易扩张 (收缩) .  相似文献   

9.
In this study, the impact of environmental factors on tropical cyclone (TC) outer-core size was investigated for both migrating and local TCs in the South China Sea during the period 2001–2019. Among all the thermodynamic and dynamic factors, the low-level environmental helicity showed the strongest positive correlation with TC outer-core size. Large helicity favors the development and organization of convection in TCs, and the corresponding strong inflow and large angular momentum fluxes into the system is beneficial for the maintenance and enlargement of TC outer-core size. Besides, the asymmetric distribution of helicity may account for the asymmetry of TC outer-core size. Therefore, the environmental helicity, as an integrated dynamic factor, can provide an alternative view on TC outer-core size.摘要本文利用2001–2019年间的ERA5再分析数据集和热带气旋 (TC) 最佳路径观测, 分析了中国南海TC的外围尺度与环境变量之间的关系. 研究发现, 低层环境螺旋度与TC外围尺度具有显著的正相关. 大的环境螺旋度有利于TC外围对流的增强和组织化, 与之对应的径向入流和角动量输送有利于TC外围尺度的维持或扩张. 此外, 螺旋度的非对称分布与TC外围尺度的非对称性结构也密切相关. 环境螺旋度作为一个包含TC外围对流强度和组织化程度等信息的综合动力因子, 为理解TC外围尺度变化提供了不同的视角.  相似文献   

10.
Using model simulated data, the distribution characteristics, genesis, and impacts on precipitation of available potential energy (APE) are analyzed for a heavy rainfall event that took place over the eastern Tibetan Plateau during 10–11 July 2018. Results show that APE was mainly distributed below 4 km and within 8–14 km. The APE distribution in the upper level had a better correspondence with precipitation. Northwestern cold advection and evaporation of falling raindrops were primary factors leading to positive anomalies of APE in the lower level, while positive anomalies of APE in the upper level were caused by a combination of thermal disturbances driven by latent heat and potential temperature perturbations resulting from the orography of the Tibetan Plateau. Budget analysis of APE indicated that APE fluxes and conversion between APE and kinetic energy (KE) were the main source and sink terms. Meridional fluxes of APE and conversion of KE to APE fed the dissipation of APE in the lower level. Vertical motion enhanced by conversion of APE to KE in the upper level was the major factor that promoted precipitation evolution. A positive feedback between APE and vertical motion in the upper level generated a powerful correlation between them. Conversion of KE to APE lasted longer in the lower level, which weakened vertical motion; whereas, northwestern cold advection brought an enhanced trend to the APE, resulting in a weak correlation between APE and vertical motion.摘要针对2018年7月10-11日青藏高原东部一次暴雨过程, 利用模式模拟资料分析了有效位能分布特征,成因及其对降水发展演变的影响.结果表明, 有效位能主要分布在对流层低层4km以下和高层8-14km, 高层有效位能和降水有更好的对应性西北冷平流和降水粒子下落的蒸发作用是低层有效位能高值中心的主要成因, 而降水过程释放潜热带来的热力扰动叠加高原大地形造成的位温扰动是导致高层有效位能高值的主要原因.有效位能收支分析表明, 有效位能的通量输送项以及与动能间的转换项是主要源汇项.低层有效位能的经向通量输送和动能向有效位能的转化补给了有效位能的耗散;高层有效位能向垂直动能转化增强垂直运动是促进降水发展演变的主要因素.高层有效位能与垂直运动之间的正反馈过程使得两者相关性较强;低层较长时间内均存在垂直动能向有效位能的转化, 削弱了垂直运动, 而西北冷平流使得低层有效位能有增强的趋势, 因此二者相关性较弱.  相似文献   

11.
Previous studies have demonstrated that the western Pacific subtropical high (WPSH) has experienced an eastward retreat since the late 1970s. In this study, the authors propose that this eastward retreat of the WPSH can be partly attributed to atmospheric responses to the positive phase of the Pacific decadal oscillation (PDO), based on idealized SST forcing experiments using the Community Atmosphere Model, version 4. Associated with the positive phase of the PDO, convective heating from the Indian Peninsula to the western Pacific and over the eastern tropical Pacific has increased, which has subsequently forced a Gill-type response to modulate the WPSH. The resulting cyclonic gyre over the Asian continent and the western Pacific in the lower troposphere is favorable for the eastward retreat of the WPSH. Additionally, the resulting anticyclonic gyre in the upper troposphere is favorable for the strengthening and southward expansion of the East Asian westerly jet, which can modulate the jet-related secondary meridional–vertical circulation over the western Pacific and promote the eastward retreat of the WPSH.摘要以往的研究已证实, 西太平洋副热带高压 (副高) 在1970s后期减弱东退.基于大气模式 (CAM4) 的理想型海温强迫试验, 结果表明:副高的东退可能是大气对于正位相太平洋年代际振荡 (PDO) 的相应.伴随着PDO转变为正位相, 西太平洋至印度半岛以及热带东太平洋的对流加热增强, 大气表现为Gill型响应, 在亚洲大陆至西太平洋上空低层产生气旋性异常, 有利于副高东退.同时, 高层产生反气旋异常, 使得东亚西风急流加强和向南扩展, 进而调节西太平洋上空的次级环流, 进一步有利于副高东退.  相似文献   

12.
本研究基于新一代FGOALS-f2动力集合预测系统35年(1981-2015年)的热带气旋历史回报试验对南海台风季(7-11月)热带气旋活动超前10天的月预测技巧进行评估,并对2020年南海台风季热带气旋活动进行了实时月预测尝试.结果表明:FGOALS-f2能较好地预测南海热带气旋路径密度演变特征,预测的热带气旋生成个...  相似文献   

13.
This study investigated the distinct responses of western North Pacific (WNP) tropical cyclone (TC) activity during different decaying El Niño summers. The El Niño events were classified into two types according to the periodicity of the ENSO cycle, with positive SST anomalies in the equatorial central-eastern Pacific maintaining positive values into the following summer as the slow decaying (SD) cases, but transforming to negative values in the following summer as the rapid decaying (RD) cases. Compared with that in SD El Niño summers, the TC occurrence frequency over the WNP is significantly lower in RD El Niño summers, led by a much weaker WNP monsoon trough with more unfavorable environmental factors for TC genesis and development. Further examination showed that the apparent warming over the tropical Indian Ocean basin and cooling over the equatorial central-eastern Pacific contribute together to an enhanced lower-tropospheric anticyclone through modulation of the descending branch of the large-scale Walker circulation over the WNP, which may play a crucial role in suppressing the TC activity during the decaying summer of RD El Niño cases. In contrast, the warming equatorial central-eastern Pacific and remote western Indian Ocean induce a weakening WNP anticyclone and less suppressed deep convection during the decaying summer of SD El Niño cases. Thus, the different evolution of SST anomalies associated with different paces of El Niño decay results in the linkage between the preceding winter El Niño and the decreased WNP TC frequency in summer being more (less) robust for RD (SD) El Niño cases.摘要本文分析了El Niño事件衰减速度的差异对衰退年夏季西北太平洋热带气旋 (tropical cyclone, TC) 频数的不同影响. 按照El Niño事件衰减速度不同, 将其划分为迅速衰减 (rapid decaying, RD) 和缓慢衰减 (slow decaying, SD) 的El Niño事件. SD (RD) El Niño事件的衰退年夏季, 赤道中东太平洋海温仍维持正异常 (衰减为负异常) . 与SD El Niño事件相比, RD El Niño事件衰退年夏季西北太平洋TC频数显著减少. 进一步的分析揭示了导致TC频数差异的大尺度环境要素, 指出热带印度洋-太平洋海温异常密切相关的西北太平洋低层反气旋异常在其中起到了关键作用.  相似文献   

14.
This paper assesses the interannual variabilities of simulated sea surface salinity (SSS) and freshwater flux (FWF) in the tropical Pacific from phases 5 and 6 of the Coupled Model Intercomparison Project (CMIP5 and CMIP6). The authors focus on comparing the simulated SSS and FWF responses to El Niño–Southern Oscillation (ENSO) from two generations of models developed by the same group. The results show that CMIP5 and CMIP6 models can perform well in simulating the spatial distributions of the SSS and FWF responses associated with ENSO, as well as their relationship. It is found that most CMIP6 models have improved in simulating the geographical distribution of the SSS and FWF interannual variability in the tropical Pacific compared to CMIP5 models. In particular, CMIP6 models have corrected the underestimation of the spatial relationship of the FWF and SSS variability with ENSO in the central-western Pacific. In addition, CMIP6 models outperform CMIP5 models in simulating the FWF interannual variability (spatial distribution and intensity) in the tropical Pacific. However, as a whole, CMIP6 models do not show improved skill scores for SSS interannual variability, which is due to their overestimation of the intensity in some models. Large uncertainties exist in simulating the interannual variability of SSS among CMIP5 and CMIP6 models and some improvements with respect to physical processes are needed.摘要通过比较CMIP5和CMIP6来自同一个单位两代模式模拟, 表明CMIP5和CMIP6均能较好地模拟出热带太平洋的海表盐度 (SSS) 和淡水通量 (FWF) 对ENSO响应的分布及其响应间的关系. 与CMIP5模式相比, 大部份CMIP6模式模拟的SSS和FWF年际变化分布均呈现改进, 特别是纠正了较低的中西太平洋SSS和FWF变化的空间关系. 但是, 整体上, CMIP6模式模拟的SSS年际变化技巧没有提高, 与SSS年际变率的强度被高估有关. CMIP5和CMIP6模式模拟SSS的年际变化还存在较大的不确定性, 在物理方面需要改进.  相似文献   

15.
China has been frequently suffering from haze pollution in the past several decades. As one of the most emission-intensive regions, the North China Plain (NCP) features severe haze pollution with multiscale variations. Using more than 30 years of visibility measurements and PM2.5 observations, a subseasonal seesaw phenomenon of haze in autumn and early winter over the NCP is revealed in this study. It is found that when September and October are less (more) polluted than the climatology, haze tends to be enhanced (reduced) in November and December. The abrupt turn of anomalous haze is found to be associated with the circulation reversal of regional and large-scale atmospheric circulations. Months with poor air quality exhibit higher relative humidity, lower boundary layer height, lower near-surface wind speed, and southerly anomalies of low-level winds, which are all unfavorable for the vertical and horizontal dispersion and transport of air pollutants, thus leading to enhanced haze pollution over the NCP region on the subseasonal scale. Further exploration indicates that the reversal of circulation patterns is closely connected to the propagation of midlatitude wave trains active on the subseasonal time scale, which is plausibly associated with the East Atlantic/West Russia teleconnection synchronizing with the transition of the North Atlantic SST. The seesaw relation discussed in this paper provides greater insight into the prediction of the multiscale variability of haze, as well as the possibility of efficient short-term mitigation of haze to meet annual air quality targets in North China.摘要中国近几十年来频受雾霾污染问题困扰, 其中华北平原作为排放最密集的区域之一, 常遭遇不同尺度的严重雾霾污染. 本文利用30余年的能见度和颗粒物 (PM2.5) 观测数据, 发现了华北平原地区在秋季和早冬时雾霾污染在次季节尺度上“跷跷板式”反向变化的关系. 研究发现, 当9–10月污染较轻 (重) 时, 11–12月的污染倾向于加重 (减轻) . 这种突然的变化与局地和大尺度环流的反向变化有关. 污染较重的月份常伴随有更高的相对湿度, 更低的边界层高度和近地面风速以及低层的南风异常, 均不利于污染的垂直和水平扩散和传输, 从而导致了次季节尺度上霾污染的加重. 进一步的研究发现环流场的突然转向与在次季节尺度上活跃的中纬度波列的传播密切相关, 而此波列可能主要与大西洋海温转变及引起的EA/WR遥相关型有关. 这一次季节反向变化为霾污染多尺度变率预测提供了新的理解, 同时为华北地区年度空气质量达标的短期目标提供了具有可行性的参考方法.  相似文献   

16.
North China May precipitation (NCMP) accounts for a relatively small percentage of annual total precipitation in North China, but its climate variability is large and it has an important impact on the regional climate and agricultural production in North China. Based on observed and reanalysis data from 1979 to 2021, a significant relationship between NCMP and both the April Indian Ocean sea surface temperature (IOSST) and Northwest Pacific Dipole (NWPD) was found, indicating that there may be a link between them. This link, and the possible physical mechanisms by which the IOSST and NWPD in April affect NCMP anomalies, are discussed. Results show that positive (negative) IOSST and NWPD anomalies in April can enhance (weaken) the water vapor transport from the Indian Ocean and Northwest Pacific to North China by influencing the related atmospheric circulation, and thus enhance (weaken) the May precipitation in North China. Accordingly, an NCMP prediction model based on April IOSST and NWPD is established. The model can predict the annual NCMP anomalies effectively, indicating it has the potential to be applied in operational climate prediction.摘要尽管华北区域五月降水 (NCMP) 占华北区域年总降水量的比率较少, 但是其气候变率较大, 对华北区域气候和农业生产等具有重要影响. 基于观测和再分析资料, 发现NCMP与前期四月的印度洋海温 (IOSST) 和西北太平洋偶极子 (NWPD) 具有显著关系, NCMP可能受到IOSST和NWPD的协同影响. 进一步分析表明, 前期四月暖 (冷) 的IOSST和正 (负) 位相的NWPD能够分别通过调节印度洋和西北太平洋区域的局地环流增强 (减弱) 从印度洋和西北太平洋向华北区域输送的水汽, 进而增强 (减弱) NCMP. 最后基于四月IOSST和NWPD构建了NCMP异常的预测模型, 后报检验显示该模型对NCMP异常具有较好的预测能力.  相似文献   

17.
Many coupled models are unable to accurately depict the multi-year La Niña conditions in the tropical Pacific during 2020–22, which poses a new challenge for real-time El Niño–Southern Oscillation (ENSO) predictions. Yet, the corresponding processes responsible for the multi-year coolings are still not understood well. In this paper, reanalysis products are analyzed to examine the ocean–atmosphere interactions in the tropical Pacific that have led to the evolution of sea surface temperature (SST) in the central-eastern equatorial Pacific, including the strong anomalous southeasterly winds over the southeastern tropical Pacific and the related subsurface thermal anomalies. Meanwhile, a divided temporal and spatial (TS) 3D convolution neural network (CNN) model, named TS-3DCNN, was developed to make predictions of the 2020/21 La Niña conditions; results from this novel data-driven model are compared with those from a physics-based intermediate coupled model (ICM). The prediction results made using the TS-3DCNN model for the 2020–22 La Niña indicate that this deep learning–based model can capture the two-year La Niña event to some extent, and is comparable to the IOCAS ICM; the latter dynamical model yields a successful real-time prediction of the Niño3.4 SST anomaly in late 2021 when it is initiated from early 2021. For physical interpretability, sensitivity experiments were designed and carried out to confirm the dominant roles played by the anomalous southeasterly wind and subsurface temperature fields in sustaining the second-year cooling in late 2021. As a potential approach to improving predictions for diversities of ENSO events, additional studies on effectively combining neural networks with dynamical processes and mechanisms are expected to significantly enhance the ENSO prediction capability.摘要2020–22年间热带太平洋经历了持续性多年的拉尼娜事件, 多数耦合模式都难以准确预测其演变过程, 这为厄尔尼诺-南方涛动(ENSO)的实时预测带来了很大的挑战. 同时, 目前学术界对此次持续性双拉尼娜事件的发展仍缺乏合理的物理解释, 其所涉及的物理过程和机制有待于进一步分析. 本研究利用再分析数据产品分析了热带东南太平洋东南风异常及其引起的次表层海温异常在此次热带太平洋海表温度(SST)异常演变中的作用, 并构建了一个时空分离(Time-Space)的三维(3D)卷积神经网络模型(TS-3DCNN)对此次双拉尼娜事件进行实时预测和过程分析. 通过将TS-3DCNN与中国科学院海洋研究所(IOCAS)中等复杂程度海气耦合模式(IOCAS ICM)的预测结果对比, 表明TS-3DCNN模型对2020–22年双重拉尼娜现象的预测能力与IOCAS ICM相当, 二者均能够从2021年初的初始场开始较好地预测2021年末 El Niño3.4区SST的演变. 此外, 基于TS-3DCNN和IOCAS ICM的敏感性试验也验证了赤道外风场异常和次表层海温异常在2021年末赤道中东太平洋海表二次变冷过程中的关键作用. 未来将神经网络与动力 模式模式间的有效结合, 进一步发展神经网络与物理过程相结合的混合建模是进一步提高ENSO事件预测能力的有效途径.  相似文献   

18.
降水日变化受大气热力,动力过程以及复杂地形影响,演变特征复杂且区域差异显著.本文采用中国气象局发布的中国地面与CMORPH融合逐小时降水产品(2008-2019年),分析了新疆省暖季降水日变化特征.研究结果表明:(1)新疆大部分地区降水主峰值发生在清晨;(2)持续时间超过三小时的降水事件是新疆地区主要降水事件,贡献了南...  相似文献   

19.
The evaluation of East Asian summer monsoon (EASM) simulations could improve our understanding of Asian monsoon dynamics and climate simulations. In this study, by using Phase 6 of the Coupled Model Intercomparison Project (CMIP6) experiments of the Atmospheric Model Intercomparison Project (AMIP) and historical runs of the Chinese Academy of Sciences (CAS) Flexible Global Ocean–Atmosphere–Land System (FGOALS-f3-L) model, the model simulation skill for the interannual variability in the EASM was determined. According to multivariate empirical orthogonal function (MV-EOF) analysis, the major mode of the EASM mainly emerged as a Pacific-Japan pattern in the western Pacific accompanied by a local anticyclonic anomaly with a total variance of 24.6%. The historical experiment could suitably reproduce this spatial pattern and attained a closer total variance than that attained by the AMIP experiment. The historical experiment could also better simulate the time frequency of the EASM variability than the AMIP experiment. However, the phase of principal component 1 (PC1) was not suitably reproduced in the historical experiment since no initialization procedure was applied at the beginning of the integration in the historical simulation process, whereas the sea surface temperature (SST) was preset in the AMIP experiment. Further analysis revealed that air–sea interactions in the Indian Ocean and tropical western Pacific were important for the model to provide satisfactory EASM simulations, while El Niño–Southern Oscillation (ENSO) simulation was possibly related to the climate variability in the EASM simulations, which should be further analyzed.摘要对东亚夏季季风(EASM)模拟的评估可以提高我们对亚洲季风动力和气候模拟的理解. 在这项研究中, 通过使用中国科学院(CAS)全球海洋-大气-陆地系统(FGOALS-f3-L)模式参加的第六次耦合模式相互比较计划(CMIP6)中的大气模式相互比较计划(AMIP)和历史(historical)试验, 明确了EASM的年际变率的模拟能力. 通过多变量经验正交函数(MV-EOF)分析发现, 观测的EASM的主导模态为西太平洋上的太平洋-日本模态, 并伴有局部反气旋异常. 主导模态的方差贡献率为24.6%. 历史(historical)试验可以基本再现这种空间模态, 其方差贡献率较AMIP试验更接近于观测. 与AMIP试验相比, 历史(historical)试验还能更好地模拟EASM变率的时间频率. 然而, 由于历史(historical)模拟没有在积分开始时应用初始化过程, 而AMIP试验受到海表面温度(SST)的约束, 因此主成分(PC1)的位相在历史(historical)试验中没有得到较好地再现. 进一步分析发现, 印度洋和西太平洋热带地区的海气相互作用对EASM的模拟非常重要, 而EASM气候变率的模拟可能与厄尔尼诺-南方涛动(ENSO)的模拟能力有关, 这值得进一步分析.  相似文献   

20.
Land–atmosphere interaction, as one of the key processes affecting the atmosphere and climate over East Asia, has drawn increasing attention during the past few decades. However, the current level of understanding regarding the mechanisms through which land surface processes impact the East Asian climate needs to be improved. Based on existing studies, six key regions where land surface processes affect the East Asian climate are proposed in this study, which can provide a valuable reference for future research into land–atmosphere interaction in East Asia.摘要陆气相互作用是影响东亚大气环流和气候的一个关键过程, 受到了越来越多的关注. 然而, 关于陆面过程影响东亚气候的相关机理的理解还有待提升. 在已有研究基础上, 提出了陆面过程影响东亚气候研究值得关注的青藏高原, 欧亚中高纬地区, 中国东部季风区, 中南半岛, 中亚中纬度区域, 西亚等6个关键区, 期待为加强陆面过程与东亚气候研究提供一定参考.  相似文献   

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