Pub Date : 2024-05-06DOI: 10.1175/jcli-d-23-0773.1
Benjamin I Cook, Edward R Cook, Kevin J Anchukaitis, Deepti Singh
Abstract During summer 2010, exceptional heat and drought in western Russia (WRU) occurred simultaneously with heavy rainfall and flooding in northern Pakistan (NPK). Here, we use the Great Eurasian Drought Atlas (GEDA), a new 1,021 year tree-ring reconstruction of summer soil moisture, to investigate the variability and dynamics of this exceptional spatially concurrent climate extreme over the last millennium. Summer 2010 in the GEDA was the second driest year over WRU and the largest wet–dry contrast between NPK and WRU; it was also the second warmest year over WRU in an independent 1,015 year temperature reconstruction. Soil moisture variability is only weakly correlated between the two regions and 2010 event analogues are rare, occurring in 31 (3.0%) or 52 (5.1%) years in the GEDA, depending on the definition used. Post-1900 is significantly drier in WRU and wetter in NPK compared to previous centuries, increasing the likelihood of concurrent wet NPK–dry WRU extremes, with over 20% of the events in the record occurring in this interval. The dynamics of wet NPK–dry WRU events like 2010 are well captured by two principal components in the GEDA, modes correlated with ridging over northern Europe and western Russia and a pan-hemispheric extratropical wave train pattern similar to that observed in 2010. Our results highlight how high resolution paleoclimate reconstructions can be used to capture some of the most extreme events in the climate system, investigate their physical drivers, and allow us to assess their behavior across longer timescales than available from shorter instrumental records.
{"title":"Characterizing the 2010 Russian heatwave-Pakistan flood concurrent extreme over the last millennium using the Great Eurasian Drought Atlas","authors":"Benjamin I Cook, Edward R Cook, Kevin J Anchukaitis, Deepti Singh","doi":"10.1175/jcli-d-23-0773.1","DOIUrl":"https://doi.org/10.1175/jcli-d-23-0773.1","url":null,"abstract":"Abstract During summer 2010, exceptional heat and drought in western Russia (WRU) occurred simultaneously with heavy rainfall and flooding in northern Pakistan (NPK). Here, we use the Great Eurasian Drought Atlas (GEDA), a new 1,021 year tree-ring reconstruction of summer soil moisture, to investigate the variability and dynamics of this exceptional spatially concurrent climate extreme over the last millennium. Summer 2010 in the GEDA was the second driest year over WRU and the largest wet–dry contrast between NPK and WRU; it was also the second warmest year over WRU in an independent 1,015 year temperature reconstruction. Soil moisture variability is only weakly correlated between the two regions and 2010 event analogues are rare, occurring in 31 (3.0%) or 52 (5.1%) years in the GEDA, depending on the definition used. Post-1900 is significantly drier in WRU and wetter in NPK compared to previous centuries, increasing the likelihood of concurrent wet NPK–dry WRU extremes, with over 20% of the events in the record occurring in this interval. The dynamics of wet NPK–dry WRU events like 2010 are well captured by two principal components in the GEDA, modes correlated with ridging over northern Europe and western Russia and a pan-hemispheric extratropical wave train pattern similar to that observed in 2010. Our results highlight how high resolution paleoclimate reconstructions can be used to capture some of the most extreme events in the climate system, investigate their physical drivers, and allow us to assess their behavior across longer timescales than available from shorter instrumental records.","PeriodicalId":15472,"journal":{"name":"Journal of Climate","volume":"17 1","pages":""},"PeriodicalIF":4.9,"publicationDate":"2024-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140885279","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-06DOI: 10.1175/jcli-d-23-0452.1
Claude Frankignoul, Lea Raillard, Brady Ferster, Young-Oh Kwon
Abstract The models that participated in the Coupled Model Intercomparison Project (CMIP) exhibit large biases in Arctic sea ice climatology that seem related to biases in seasonal atmospheric and oceanic circulations. Using historical runs of 34 CMIP6 models from 1979 to 2014, we investigate the links between the climatological sea ice concentration (SIC) biases in September and atmospheric and oceanic model climatologies. The main inter-model spread of September SIC is well described by two leading EOFs, which together explain ∼65% of its variance. The first EOF represents an underestimation or overestimation of SIC in the whole Arctic, while the second EOF describes opposite SIC biases in the Atlantic and Pacific sectors. Regression analysis indicates that the two SIC modes are closely related to departures from the multi-model mean of Arctic surface heat fluxes during summer, primarily shortwave and longwave radiation, with incoming Atlantic Water playing a role in the Atlantic sector. Local and global links with summer cloud cover, low-level humidity, upper or lower troposphere temperature/circulation, and oceanic variables are also found. As illustrated for three climate models, the local relationships with the SIC biases are mostly similar in the Arctic across the models but show varying degrees of Atlantic inflow influence. On global scale, a strong influence of the summer atmospheric circulation on September SIC is suggested for one of the three models, while the atmospheric influence is primarily via thermodynamics in the other two. Clear links to the North Atlantic Ocean circulation are seen in one of the models.
摘要 参加耦合模式相互比较项目（CMIP）的模式在北极海冰气候学上表现出很大的偏差，这似乎与季节性大气和海洋环流的偏差有关。利用从 1979 年到 2014 年 34 个 CMIP6 模式的历史运行，我们研究了 9 月份气候学海冰浓度（SIC）偏差与大气和海洋模式气候学之间的联系。两个主要的 EOF 很好地描述了 9 月海冰浓度的主要模式间差异，它们共同解释了其 65%的方差。第一个 EOF 代表低估或高估了整个北极地区的 SIC，而第二个 EOF 则描述了大西洋和太平洋地区相反的 SIC 偏差。回归分析表明，这两种 SIC 模式与夏季北极地表热通量（主要是短波和长波辐射）偏离多模式平均值密切相关，而在大西洋扇区，大西洋来水起了作用。此外，还发现了与夏季云量、低层湿度、对流层上层或下层温度/环流以及海洋变量之间的局部和全球联系。如三个气候模式所示，在北极地区，各模式与 SIC 偏差的局部关系基本相似，但受大西洋入流影响的程度不同。在全球尺度上，三个模式中的一个表明夏季大气环流对 9 月 SIC 有很大影响，而在另外两个模式中，大气影响主要是通过热力学产生的。其中一个模式与北大西洋环流有明显联系。
{"title":"Arctic September sea ice concentration biases in CMIP6 models and their relationships with other model variables","authors":"Claude Frankignoul, Lea Raillard, Brady Ferster, Young-Oh Kwon","doi":"10.1175/jcli-d-23-0452.1","DOIUrl":"https://doi.org/10.1175/jcli-d-23-0452.1","url":null,"abstract":"Abstract The models that participated in the Coupled Model Intercomparison Project (CMIP) exhibit large biases in Arctic sea ice climatology that seem related to biases in seasonal atmospheric and oceanic circulations. Using historical runs of 34 CMIP6 models from 1979 to 2014, we investigate the links between the climatological sea ice concentration (SIC) biases in September and atmospheric and oceanic model climatologies. The main inter-model spread of September SIC is well described by two leading EOFs, which together explain ∼65% of its variance. The first EOF represents an underestimation or overestimation of SIC in the whole Arctic, while the second EOF describes opposite SIC biases in the Atlantic and Pacific sectors. Regression analysis indicates that the two SIC modes are closely related to departures from the multi-model mean of Arctic surface heat fluxes during summer, primarily shortwave and longwave radiation, with incoming Atlantic Water playing a role in the Atlantic sector. Local and global links with summer cloud cover, low-level humidity, upper or lower troposphere temperature/circulation, and oceanic variables are also found. As illustrated for three climate models, the local relationships with the SIC biases are mostly similar in the Arctic across the models but show varying degrees of Atlantic inflow influence. On global scale, a strong influence of the summer atmospheric circulation on September SIC is suggested for one of the three models, while the atmospheric influence is primarily via thermodynamics in the other two. Clear links to the North Atlantic Ocean circulation are seen in one of the models.","PeriodicalId":15472,"journal":{"name":"Journal of Climate","volume":"63 1","pages":""},"PeriodicalIF":4.9,"publicationDate":"2024-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140885242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-03DOI: 10.1175/jcli-d-23-0534.1
Lei Fan, Hui-Huang Fu, Yu Liang
Abstract This study identifies two distinct patterns of the summer Indian Ocean Dipole (IOD) — the coastal IOD and the offshore IOD — named based on the proximity of their eastern pole to Sumatra. Their spatial characteristics, evolutionary mechanisms, relationships with ENSO, impacts on precipitation, and the factors controlling the simulation performances of climate models are discussed. The coastal IOD shares the same eastern pole as the conventional IOD off Sumatra, but its western pole is located in the central southern tropical Indian Ocean (TIO). The offshore IOD shares the conventional western pole off Somalia, but its eastern pole is located in the central southern TIO. Regarding their evolutions, while they initially develop similarly, their later evolutions differ due to their distinct pole locations: the offshore IOD peaks in summer, while the coastal IOD can be sustained into autumn. The coastal IOD correlates to preceding and late ENSO states, but the offshore IOD does not, making it an independent internal mode of TIO. The two IODs affect climate differently, with only the coastal IOD affecting Australian rainfall. Climate models exhibit varied levels of performance in simulating the two IODs. Specifically, a stronger link between spring TIO rainfall and ENSO, as well as stronger southeasterly monsoonal winds in the southern TIO, can enhance the coastal IOD modeling, while a stronger summer Somali jet benefits the simulation of the offshore IOD. Distinguishing these two IODs has implications for accurate diagnosis and prediction of the summer climate surrounding the TIO.
{"title":"Two Characteristic Patterns of the Summer Indian Ocean Dipole","authors":"Lei Fan, Hui-Huang Fu, Yu Liang","doi":"10.1175/jcli-d-23-0534.1","DOIUrl":"https://doi.org/10.1175/jcli-d-23-0534.1","url":null,"abstract":"Abstract This study identifies two distinct patterns of the summer Indian Ocean Dipole (IOD) — the coastal IOD and the offshore IOD — named based on the proximity of their eastern pole to Sumatra. Their spatial characteristics, evolutionary mechanisms, relationships with ENSO, impacts on precipitation, and the factors controlling the simulation performances of climate models are discussed. The coastal IOD shares the same eastern pole as the conventional IOD off Sumatra, but its western pole is located in the central southern tropical Indian Ocean (TIO). The offshore IOD shares the conventional western pole off Somalia, but its eastern pole is located in the central southern TIO. Regarding their evolutions, while they initially develop similarly, their later evolutions differ due to their distinct pole locations: the offshore IOD peaks in summer, while the coastal IOD can be sustained into autumn. The coastal IOD correlates to preceding and late ENSO states, but the offshore IOD does not, making it an independent internal mode of TIO. The two IODs affect climate differently, with only the coastal IOD affecting Australian rainfall. Climate models exhibit varied levels of performance in simulating the two IODs. Specifically, a stronger link between spring TIO rainfall and ENSO, as well as stronger southeasterly monsoonal winds in the southern TIO, can enhance the coastal IOD modeling, while a stronger summer Somali jet benefits the simulation of the offshore IOD. Distinguishing these two IODs has implications for accurate diagnosis and prediction of the summer climate surrounding the TIO.","PeriodicalId":15472,"journal":{"name":"Journal of Climate","volume":"23 1","pages":""},"PeriodicalIF":4.9,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140839791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-02DOI: 10.1175/jcli-d-23-0400.1
Yang Zhao, Jianping Li, Yuan Tian, Jiao Li
Abstract This study investigates the disparity in quantitative moisture contribution and synoptic-scale vertical motion in the lower reaches of the Yangtze River (LYRB) for different extreme precipitation (EP) types, which are categorized as EP associated with atmospheric river (AR&EP) or non-atmospheric river (non-AR&EP). To analyze moisture contribution, a backward tracking using the water accounting model-2layers is performed. In general, the remote moisture contribution is 9.7 times greater than the local contribution, with ocean contribution being 1.67 times stronger than land contribution. However, terrestrial and oceanic contributions obviously increase in the EP types, especially for oceanic contribution being double in magnitude. Notably, the West Pacific (WP) contribution emerges as the dominant differentia between the EP types, playing a crucial role in AR formation. By solving the quasi-geostrophic omega equation, the upper-level jet stream (ULJ) acts as the primary dynamic forcing for transverse vertical motion in AR&EP, while the baroclinic trough exhibits a relatively weaker influence. However, both systems have a nearly equal impact on vertical velocity in non-AR&EP. The enhanced shearwise elevation in the non-AR&EP type is the response of the stronger upper-level ridge over the Tibetan Plateau (TP), which induce enhanced Q-vector divergence pointing towards the LYRB. However, the main dynamic differences is location of ULJ, which serves as the trigger role although weak. Diabatic forcing proves to be the decisive factor for vertical motion development, the difference attributed to the released excessive latent heating with excess moisture contribution from the WP in AR&EP with enhanced precipitation.
摘要 本研究探讨了长江下游不同极端降水（EP）类型的定量水汽贡献和同步尺度垂直运动的差异，这些极端降水分为与大气河流相关的极端降水（AR&EP）和非大气河流的极端降水（non-AR&EP）。为了分析水汽贡献，利用水量核算模型-2 层进行了反向跟踪。总体而言，远程水汽贡献是本地贡献的 9.7 倍，海洋贡献是陆地贡献的 1.67 倍。然而，陆地和海洋贡献在 EP 类型中明显增加，特别是海洋贡献增加了一倍。值得注意的是，西太平洋（WP）贡献是 EP 类型之间的主要差异，在 AR 形成中起着至关重要的作用。通过求解准地转ω方程，高层喷流（ULJ）是 AR&EP 中横向垂直运动的主要动力，而条纹状槽的影响相对较弱。然而，这两个系统对非 AR&EP 的垂直速度的影响几乎相同。非 AR&EP 类型的切变抬升增强是青藏高原（TP）上空更强的高层脊的反应，它导致指向涟源低压带的 Q 向量发散增强。然而，主要的动态差异在于 ULJ 的位置，尽管它的触发作用很弱。虚热强迫被证明是垂直运动发展的决定性因素，这种差异可归因于在降水增强的情况下，AR&EP 的 WP 释放了过多的潜热和过多的水汽。
{"title":"Distinguish Extreme Precipitation Mechanisms Associated with Atmospheric River and Non-Atmospheric River in the Lower Yangtze River Basin","authors":"Yang Zhao, Jianping Li, Yuan Tian, Jiao Li","doi":"10.1175/jcli-d-23-0400.1","DOIUrl":"https://doi.org/10.1175/jcli-d-23-0400.1","url":null,"abstract":"Abstract This study investigates the disparity in quantitative moisture contribution and synoptic-scale vertical motion in the lower reaches of the Yangtze River (LYRB) for different extreme precipitation (EP) types, which are categorized as EP associated with atmospheric river (AR&EP) or non-atmospheric river (non-AR&EP). To analyze moisture contribution, a backward tracking using the water accounting model-2layers is performed. In general, the remote moisture contribution is 9.7 times greater than the local contribution, with ocean contribution being 1.67 times stronger than land contribution. However, terrestrial and oceanic contributions obviously increase in the EP types, especially for oceanic contribution being double in magnitude. Notably, the West Pacific (WP) contribution emerges as the dominant differentia between the EP types, playing a crucial role in AR formation. By solving the quasi-geostrophic omega equation, the upper-level jet stream (ULJ) acts as the primary dynamic forcing for transverse vertical motion in AR&EP, while the baroclinic trough exhibits a relatively weaker influence. However, both systems have a nearly equal impact on vertical velocity in non-AR&EP. The enhanced shearwise elevation in the non-AR&EP type is the response of the stronger upper-level ridge over the Tibetan Plateau (TP), which induce enhanced Q-vector divergence pointing towards the LYRB. However, the main dynamic differences is location of ULJ, which serves as the trigger role although weak. Diabatic forcing proves to be the decisive factor for vertical motion development, the difference attributed to the released excessive latent heating with excess moisture contribution from the WP in AR&EP with enhanced precipitation.","PeriodicalId":15472,"journal":{"name":"Journal of Climate","volume":"21 1","pages":""},"PeriodicalIF":4.9,"publicationDate":"2024-05-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140839687","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-30DOI: 10.1175/jcli-d-23-0277.1
Qingye Min, Renhe Zhang
Abstract The South Pacific Oscillation (SPO), characterized by a north-south dipole-like pattern of sea level pressure anomalies, is one of the key factors in understanding tropical-extratropical interactions in South Pacific. We show that in boreal summer (June–July–August), the center of the northern lobe sea level pressure anomalies in the SPO is shifted to the east gradually after the 1960–70s. This study focuses on the relationship between the boreal summer SPO and following winter El Niño–Southern Oscillation (ENSO) diversity before and after the eastward shift of the SPO’s subtropical lobe. The eastward shift of the SPO’s subtropical lobe altered both the seasonal footprint mechanism and the trade wind charging mechanism associated with the SPO, thus profoundly influenced the ENSO diversity. It is revealed that when the northern lobe of the SPO shifts to the west of its average location, it tends to strengthen the EP El Niño mainly via the seasonal footprint mechanism. but after the SPO’s northern lobe shifts to the east of its average location, it tends to promote the development of CP El Niño mainly via the trade wind charging mechanism. The changes in the spatial structure of convection over the tropical Pacific and Indian Ocean may be one of the possible causes for the eastward shift in the SPO’s northern lobe. The findings in the present study have implications for a better understanding of ENSO diversity.
{"title":"The interdecadal changes in the spatial structure of the South Pacific Oscillation and its implication for ENSO diversity","authors":"Qingye Min, Renhe Zhang","doi":"10.1175/jcli-d-23-0277.1","DOIUrl":"https://doi.org/10.1175/jcli-d-23-0277.1","url":null,"abstract":"Abstract The South Pacific Oscillation (SPO), characterized by a north-south dipole-like pattern of sea level pressure anomalies, is one of the key factors in understanding tropical-extratropical interactions in South Pacific. We show that in boreal summer (June–July–August), the center of the northern lobe sea level pressure anomalies in the SPO is shifted to the east gradually after the 1960–70s. This study focuses on the relationship between the boreal summer SPO and following winter El Niño–Southern Oscillation (ENSO) diversity before and after the eastward shift of the SPO’s subtropical lobe. The eastward shift of the SPO’s subtropical lobe altered both the seasonal footprint mechanism and the trade wind charging mechanism associated with the SPO, thus profoundly influenced the ENSO diversity. It is revealed that when the northern lobe of the SPO shifts to the west of its average location, it tends to strengthen the EP El Niño mainly via the seasonal footprint mechanism. but after the SPO’s northern lobe shifts to the east of its average location, it tends to promote the development of CP El Niño mainly via the trade wind charging mechanism. The changes in the spatial structure of convection over the tropical Pacific and Indian Ocean may be one of the possible causes for the eastward shift in the SPO’s northern lobe. The findings in the present study have implications for a better understanding of ENSO diversity.","PeriodicalId":15472,"journal":{"name":"Journal of Climate","volume":"20 1","pages":""},"PeriodicalIF":4.9,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140842476","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-30DOI: 10.1175/jcli-d-23-0567.1
Hong Wang, Liang Gao, Lei Zhu, Lulu Zhang, Jiahao Wu
Abstract Accurately assessing cyclone intensity changes due to global warming is crucial for predicting and mitigating sequential hazards. This study develops a high-resolution, fully coupled air-sea model to investigate the impact of global warming on Super Typhoon Mangkhut (2018). A numerical sensitivity analysis is conducted using the Pseudo-Global Warming (PGW) technique based on multiple global climate models (GCMs) from the Coupled Model Intercomparison Project Phases 6 (CMIP6). Under ocean warming scenarios, the increasing average sea surface temperature (SST) by 2.26 °C, 2.44 °C, 3.45 °C, and 4.53 °C result in reductions in minimum sea-level pressure by 9.2 hPa, 10.6 hPa, 15.7 hPa, and 19.4 hPa, respectively, compared to the original state of Typhoon Mangkhut. Rising SST increases turbulent heat flux, to be specific, an average SST increase of 2.26-4.53 °C changes the turbulent heat flux into 177% to 272% of the original value. Besides, stronger winds enhance SST cooling, including upwelling and entrainment, leading to an increase in the mixed layer depth (MLD). Tropical cyclone heat potential (TCHP) tends to be enhanced under the combined influences as the SST rises. An average increase in SST of 2.26 °C, 2.44 °C, 3.45 °C, and 4.53 °C leads to increase in TCHP of 9.94%, 9.85%, 14.67%, and 15.30%, respectively. However, future changes in atmospheric temperature and humidity will moderate typhoon intensification induced by ocean warming. Considering atmospheric conditions, the maximum wind speed decreases by approximately 10% compared to only considering ocean warming. Nevertheless, typhoon intensity is projected to strengthen under future climate change.
{"title":"Changes in the Typhoon Intensity under a Warming Climate: A Numerical Study of Typhoon Mangkhut","authors":"Hong Wang, Liang Gao, Lei Zhu, Lulu Zhang, Jiahao Wu","doi":"10.1175/jcli-d-23-0567.1","DOIUrl":"https://doi.org/10.1175/jcli-d-23-0567.1","url":null,"abstract":"Abstract Accurately assessing cyclone intensity changes due to global warming is crucial for predicting and mitigating sequential hazards. This study develops a high-resolution, fully coupled air-sea model to investigate the impact of global warming on Super Typhoon Mangkhut (2018). A numerical sensitivity analysis is conducted using the Pseudo-Global Warming (PGW) technique based on multiple global climate models (GCMs) from the Coupled Model Intercomparison Project Phases 6 (CMIP6). Under ocean warming scenarios, the increasing average sea surface temperature (SST) by 2.26 °C, 2.44 °C, 3.45 °C, and 4.53 °C result in reductions in minimum sea-level pressure by 9.2 hPa, 10.6 hPa, 15.7 hPa, and 19.4 hPa, respectively, compared to the original state of Typhoon Mangkhut. Rising SST increases turbulent heat flux, to be specific, an average SST increase of 2.26-4.53 °C changes the turbulent heat flux into 177% to 272% of the original value. Besides, stronger winds enhance SST cooling, including upwelling and entrainment, leading to an increase in the mixed layer depth (MLD). Tropical cyclone heat potential (TCHP) tends to be enhanced under the combined influences as the SST rises. An average increase in SST of 2.26 °C, 2.44 °C, 3.45 °C, and 4.53 °C leads to increase in TCHP of 9.94%, 9.85%, 14.67%, and 15.30%, respectively. However, future changes in atmospheric temperature and humidity will moderate typhoon intensification induced by ocean warming. Considering atmospheric conditions, the maximum wind speed decreases by approximately 10% compared to only considering ocean warming. Nevertheless, typhoon intensity is projected to strengthen under future climate change.","PeriodicalId":15472,"journal":{"name":"Journal of Climate","volume":"23 1","pages":""},"PeriodicalIF":4.9,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140839790","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-26DOI: 10.1175/jcli-d-23-0627.1
Masahiro Shiozaki, Hiroki Tokinaga, Masato Mori
Abstract Atmospheric teleconnections from the Pacific El Niño are key to determining the East Asian winter climate. Using the database for Policy Decision-making for Future climate change (d4PDF) large ensemble simulations, the present study investigates a mechanism for the warm and cold East Asian winters during El Niño with a focus on atmospheric teleconnections triggered by anomalous sea surface temperature (SST) patterns in the tropical Indo-Pacific. Our results show that the Western Pacific (WP) teleconnection pattern plays a primary role in the warm winters in East Asia. The WP pattern tends to appear in years when both an early El Niño and the positive phase of the Indian Ocean dipole mode (IOD) develop in boreal autumn. In those years, the tropical Indian Ocean (TIO) strongly warms in the following winter, forming a distinct zonal contrast in precipitation anomalies over the tropical Indo-Pacific through a reduced Walker circulation. The Rossby wave source anomalies indicate that the WP pattern is associated with the weakened Indo-Pacific Walker circulation. By contrast, the WP pattern does not dominate in the cold winters due to the absence of strong TIO warming. The present study proposes a mechanism that promotes excitation of the WP pattern through the upper-troposphere divergence in East Asia associated with the Walker circulation modulated by the tropical Indo-Pacific interbasin interaction.
摘要 来自太平洋厄尔尼诺现象的大气远缘联系是决定东亚冬季气候的关键。本研究利用未来气候变化决策数据库（d4PDF）大型集合模拟，研究了厄尔尼诺期间东亚冬季冷暖变化的机制，重点是热带印度洋-太平洋异常海面温度（SST）模式引发的大气远缘联系。我们的研究结果表明，西太平洋（WP）遥连模式在东亚暖冬中发挥了主要作用。西太平洋模式往往出现在早期厄尔尼诺现象和印度洋偶极模式（IOD）正相同时出现在北方秋季的年份。在这些年份，热带印度洋（TIO）在接下来的冬季会强烈变暖，通过减弱的沃克环流在热带印度洋-太平洋上空形成明显的降水异常地带性对比。罗斯比波源异常表明，WP 模式与减弱的印度洋-太平洋沃克环流有关。相比之下，由于没有强烈的 TIO 增暖，WP 模式在寒冷的冬季并不占主导地位。本研究提出了一种机制，即通过与受热带印度洋-太平洋流域间相互作用调节的沃克环流相关的东亚上对流层辐散，促进 WP 模式的激发。
{"title":"What Determines the East Asian Winter Temperature during El Niño? — Role of the Early-Onset El Niño and Tropical Indian Ocean Warming","authors":"Masahiro Shiozaki, Hiroki Tokinaga, Masato Mori","doi":"10.1175/jcli-d-23-0627.1","DOIUrl":"https://doi.org/10.1175/jcli-d-23-0627.1","url":null,"abstract":"Abstract Atmospheric teleconnections from the Pacific El Niño are key to determining the East Asian winter climate. Using the database for Policy Decision-making for Future climate change (d4PDF) large ensemble simulations, the present study investigates a mechanism for the warm and cold East Asian winters during El Niño with a focus on atmospheric teleconnections triggered by anomalous sea surface temperature (SST) patterns in the tropical Indo-Pacific. Our results show that the Western Pacific (WP) teleconnection pattern plays a primary role in the warm winters in East Asia. The WP pattern tends to appear in years when both an early El Niño and the positive phase of the Indian Ocean dipole mode (IOD) develop in boreal autumn. In those years, the tropical Indian Ocean (TIO) strongly warms in the following winter, forming a distinct zonal contrast in precipitation anomalies over the tropical Indo-Pacific through a reduced Walker circulation. The Rossby wave source anomalies indicate that the WP pattern is associated with the weakened Indo-Pacific Walker circulation. By contrast, the WP pattern does not dominate in the cold winters due to the absence of strong TIO warming. The present study proposes a mechanism that promotes excitation of the WP pattern through the upper-troposphere divergence in East Asia associated with the Walker circulation modulated by the tropical Indo-Pacific interbasin interaction.","PeriodicalId":15472,"journal":{"name":"Journal of Climate","volume":"23 1","pages":""},"PeriodicalIF":4.9,"publicationDate":"2024-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140802204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-22DOI: 10.1175/jcli-d-23-0102.1
Beiyao Liu, Ying Li, Zhehong Wu, Jialu Lin
Abstract Early summer is a peak time for tropical cyclone (TC) activities over the Bay of Bengal (BoB) and a period of South Asian monsoon onset, and the TCs during this time have a significant impact on the water vapor transport associated with monsoons. This study investigates the anomalous characteristics of the dynamic–thermal atmospheric circulation structure and water vapor budget over the Tibetan Plateau (TP) under the influence of BoB TCs generated in May from 1979 to 2020 with JTWC best track data and ERA5 data. Results reveal that a significant southerly water vapor channel forms from the BoB to the southeastern TP with a water vapor convergence near the Yarlung Zangbo Grand Canyon. A part of the water vapor is transported directly to the TP by deep southerly jet, while the other part is lifted by TCs and then climbs upward to the TP by two uplift processes occurring on the southern slope of the TP and over the TP respectively, which makes the whole troposphere over the southeastern TP warmer and wetter. It is found that anomalous southeasterly airflow in the northeast of TC circulation turns to anomalous southwesterly airflow forming an abnormal anticyclonic circulation over the southern TP in the middle and upper troposphere due to the diabatic heating effect. In this process, the TP acts as an anomalous water vapor sink with remarkable water vapor inflow through its southern boundary, with the main water vapor outflow through the eastern boundary, but a weak easterly water vapor backflow to the eastern TP in the lower troposphere. Significance Statement This study attempts to investigate the anomalous features of the water vapor budget over the Tibetan Plateau (TP) under the influence of the Bay of Bengal (BoB) tropical cyclones (TCs) during early summer. Results show that a significant southerly water vapor channel forms from the BoB to the southeastern TP with a water vapor convergence near the Yarlung Zangbo Grand Canyon. The TP acts as an anomalous water vapor sink with more and higher water vapor inflows through the southern boundary of the TP. A positive temperature and humidity anomaly can be found over the southeastern TP extending upward into the middle and upper troposphere. The results are helpful to understand how the BoB TCs affect the weather process over the TP.
{"title":"Anomalous Characteristics of Water Vapor Budget on the Tibetan Plateau under the Influence of Tropical Cyclones over the Bay of Bengal during Early Summer","authors":"Beiyao Liu, Ying Li, Zhehong Wu, Jialu Lin","doi":"10.1175/jcli-d-23-0102.1","DOIUrl":"https://doi.org/10.1175/jcli-d-23-0102.1","url":null,"abstract":"Abstract Early summer is a peak time for tropical cyclone (TC) activities over the Bay of Bengal (BoB) and a period of South Asian monsoon onset, and the TCs during this time have a significant impact on the water vapor transport associated with monsoons. This study investigates the anomalous characteristics of the dynamic–thermal atmospheric circulation structure and water vapor budget over the Tibetan Plateau (TP) under the influence of BoB TCs generated in May from 1979 to 2020 with JTWC best track data and ERA5 data. Results reveal that a significant southerly water vapor channel forms from the BoB to the southeastern TP with a water vapor convergence near the Yarlung Zangbo Grand Canyon. A part of the water vapor is transported directly to the TP by deep southerly jet, while the other part is lifted by TCs and then climbs upward to the TP by two uplift processes occurring on the southern slope of the TP and over the TP respectively, which makes the whole troposphere over the southeastern TP warmer and wetter. It is found that anomalous southeasterly airflow in the northeast of TC circulation turns to anomalous southwesterly airflow forming an abnormal anticyclonic circulation over the southern TP in the middle and upper troposphere due to the diabatic heating effect. In this process, the TP acts as an anomalous water vapor sink with remarkable water vapor inflow through its southern boundary, with the main water vapor outflow through the eastern boundary, but a weak easterly water vapor backflow to the eastern TP in the lower troposphere. Significance Statement This study attempts to investigate the anomalous features of the water vapor budget over the Tibetan Plateau (TP) under the influence of the Bay of Bengal (BoB) tropical cyclones (TCs) during early summer. Results show that a significant southerly water vapor channel forms from the BoB to the southeastern TP with a water vapor convergence near the Yarlung Zangbo Grand Canyon. The TP acts as an anomalous water vapor sink with more and higher water vapor inflows through the southern boundary of the TP. A positive temperature and humidity anomaly can be found over the southeastern TP extending upward into the middle and upper troposphere. The results are helpful to understand how the BoB TCs affect the weather process over the TP.","PeriodicalId":15472,"journal":{"name":"Journal of Climate","volume":"5 1","pages":""},"PeriodicalIF":4.9,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140802202","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-19DOI: 10.1175/jcli-d-23-0426.1
Arshdeep Singh, Sanjiv Kumar, Liang Chen, Montasir Maruf, Peter Lawrence, Min-Hui Lo
Abstract This study examines the effects of land use (LU) change on regional climate, comparing historical and future scenarios using seven climate models from Coupled Model Intercomparison Phase 6 – Land Use Model Intercomparison Project experiments. LU changes are evaluated relative to land use conditions during the pre-industrial climate. Using the Community Earth System Model version 2 Large Ensemble (CESM2-LE) experiment, we distinguish LU impacts from natural climate variability. We assess LU impact locally by comparing the impacts of climate change in neighboring areas with and without LU changes. Further, we conduct CESM2 experiments with and without LU changes to investigate LU-related climate processes. A multi-model analysis reveals a shift in LU-induced climate impacts, from cooling in the past to warming in the future climate across mid-latitude regions. For instance, in North America, LU's effect on air temperature changes from −0.24±0.18°C historically to 0.62±0.27°C in the future during the boreal summer. The CESM2-LE shows a decrease in LU-driven cooling from −0.92±0.09°C in the past to −0.09±0.09°C in future boreal summers in North America. A hydroclimatic perspective linking LU and climate feedback indicates LU changes causing soil moisture drying in the mid-latitude regions. This contrasts with hydrology-only views showing wetter soil conditions due to LU changes. Furthermore, global warming causes widespread drying of soil moisture across various regions. Mid-latitude regions shift from a historically wet regime to a water limited transitional regime in the future climate. This results in reduced evapotranspiration, weakening LU-driven cooling in future climate projections. A strong linear relationship exists between soil moisture and evaporative fraction in mid-latitudes.
摘要 本研究利用耦合模式相互比较第六阶段--土地利用模式相互比较项目实验中的七个气候模式，比较了历史和未来情景，研究了土地利用（LU）变化对区域气候的影响。相对于工业化前气候期间的土地利用条件，对土地利用变化进行了评估。利用群落地球系统模式第二版大型集合（CESM2-LE）实验，我们将土地利用的影响与自然气候变异性区分开来。我们通过比较有和没有土地利用变化的邻近地区的气候变化影响来评估土地利用的局部影响。此外，我们还进行了有 LU 变化和无 LU 变化的 CESM2 试验，以研究与 LU 相关的气候过程。多模式分析显示，LU 引起的气候影响发生了转变，在整个中纬度地区，过去气候变冷，未来气候变暖。例如，在北美洲的北方夏季，LU 对气温的影响从历史上的 -0.24±0.18°C 变为未来的 0.62±0.27°C。CESM2-LE 显示，在北美洲，LU 驱动的降温从过去的-0.92±0.09°C 下降到未来北方夏季的-0.09±0.09°C。从水文气候角度将土地利用变化与气候反馈联系起来，表明土地利用变化导致中纬度地区土壤水分干燥。这与仅从水文角度看土地利用变化导致土壤更湿润形成鲜明对比。此外，全球变暖导致不同地区的土壤水分普遍干燥。在未来气候中，中纬度地区从历史上的湿润状态转变为限水过渡状态。这导致蒸散量减少，削弱了未来气候预测中由土地利用变化驱动的降温。中纬度地区的土壤湿度与蒸发分量之间存在很强的线性关系。
{"title":"Land Use Feedback under Global Warming – A Transition from Radiative to Hydrological Feedback Regime","authors":"Arshdeep Singh, Sanjiv Kumar, Liang Chen, Montasir Maruf, Peter Lawrence, Min-Hui Lo","doi":"10.1175/jcli-d-23-0426.1","DOIUrl":"https://doi.org/10.1175/jcli-d-23-0426.1","url":null,"abstract":"Abstract This study examines the effects of land use (LU) change on regional climate, comparing historical and future scenarios using seven climate models from Coupled Model Intercomparison Phase 6 – Land Use Model Intercomparison Project experiments. LU changes are evaluated relative to land use conditions during the pre-industrial climate. Using the Community Earth System Model version 2 Large Ensemble (CESM2-LE) experiment, we distinguish LU impacts from natural climate variability. We assess LU impact locally by comparing the impacts of climate change in neighboring areas with and without LU changes. Further, we conduct CESM2 experiments with and without LU changes to investigate LU-related climate processes. A multi-model analysis reveals a shift in LU-induced climate impacts, from cooling in the past to warming in the future climate across mid-latitude regions. For instance, in North America, LU's effect on air temperature changes from −0.24±0.18°C historically to 0.62±0.27°C in the future during the boreal summer. The CESM2-LE shows a decrease in LU-driven cooling from −0.92±0.09°C in the past to −0.09±0.09°C in future boreal summers in North America. A hydroclimatic perspective linking LU and climate feedback indicates LU changes causing soil moisture drying in the mid-latitude regions. This contrasts with hydrology-only views showing wetter soil conditions due to LU changes. Furthermore, global warming causes widespread drying of soil moisture across various regions. Mid-latitude regions shift from a historically wet regime to a water limited transitional regime in the future climate. This results in reduced evapotranspiration, weakening LU-driven cooling in future climate projections. A strong linear relationship exists between soil moisture and evaporative fraction in mid-latitudes.","PeriodicalId":15472,"journal":{"name":"Journal of Climate","volume":"52 1","pages":""},"PeriodicalIF":4.9,"publicationDate":"2024-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140631066","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-19DOI: 10.1175/jcli-d-23-0617.1
Martin P. Hoerling, Jon K. Eischeid, Henry F. Diaz, Balaji Rajagopolan, Eric Kuhn
Abstract Of concern to Colorado River management, as operating guidelines post-2026 are being considered, is whether water resource recovery from low flows during 2000–2020 is possible. Here we analyze new simulations from the sixth generation of the Coupled Model Intercomparison Project (CMIP6) to determine plausible climate impacts on Colorado River flows for 2026–2050 when revised guidelines would operate. We constrain projected flows for Lee Ferry, the gauge through which 85% of the river flow passes, using its estimated sensitivity to meteorological variability together with CMIP6 projected precipitation and temperature changes. The critical importance of precipitation, especially its natural variability, is emphasized. Model projections indicate increased precipitation in the Upper Colorado River basin due to climate change, which alone increases river flows 5%–7% (relative to a 2000–2020 climatology). Depending on the river’s temperature sensitivity, this wet signal compensates some, if not all, of the depleting effects from basin warming. Considerable internal decadal precipitation variability (~5% of the climatological mean) is demonstrated, driving a greater range of plausible Colorado River flow changes for 2026–2050 than previously surmised from treatment of temperature impacts alone: the overall precipitation-induced Lee Ferry flow changes span −25% to +40% contrasting with a −30% to −5% range from expected warming effects only. Consequently, extreme low and high flows are more likely. Lee Ferry flow projections, conditioned on initial drought states akin to 2000–2020, reveal substantial recovery odds for water resources, albeit with elevated risks of even further flow declines than in recent decades.
{"title":"Critical Effects of Precipitation on Future Colorado River Flow","authors":"Martin P. Hoerling, Jon K. Eischeid, Henry F. Diaz, Balaji Rajagopolan, Eric Kuhn","doi":"10.1175/jcli-d-23-0617.1","DOIUrl":"https://doi.org/10.1175/jcli-d-23-0617.1","url":null,"abstract":"Abstract Of concern to Colorado River management, as operating guidelines post-2026 are being considered, is whether water resource recovery from low flows during 2000–2020 is possible. Here we analyze new simulations from the sixth generation of the Coupled Model Intercomparison Project (CMIP6) to determine plausible climate impacts on Colorado River flows for 2026–2050 when revised guidelines would operate. We constrain projected flows for Lee Ferry, the gauge through which 85% of the river flow passes, using its estimated sensitivity to meteorological variability together with CMIP6 projected precipitation and temperature changes. The critical importance of precipitation, especially its natural variability, is emphasized. Model projections indicate increased precipitation in the Upper Colorado River basin due to climate change, which alone increases river flows 5%–7% (relative to a 2000–2020 climatology). Depending on the river’s temperature sensitivity, this wet signal compensates some, if not all, of the depleting effects from basin warming. Considerable internal decadal precipitation variability (~5% of the climatological mean) is demonstrated, driving a greater range of plausible Colorado River flow changes for 2026–2050 than previously surmised from treatment of temperature impacts alone: the overall precipitation-induced Lee Ferry flow changes span −25% to +40% contrasting with a −30% to −5% range from expected warming effects only. Consequently, extreme low and high flows are more likely. Lee Ferry flow projections, conditioned on initial drought states akin to 2000–2020, reveal substantial recovery odds for water resources, albeit with elevated risks of even further flow declines than in recent decades.","PeriodicalId":15472,"journal":{"name":"Journal of Climate","volume":"75 1","pages":""},"PeriodicalIF":4.9,"publicationDate":"2024-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140631071","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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