Journal of Geophysical Research: Atmospheres最新文献

{"title":"Flux Convergence and Divergence Linked to Asymmetric Transport by Large Turbulent Eddies in the Unstable Atmospheric Surface Layer","authors":"Zhongming Gao, Lei Li, Heping Liu, Bai Yang","doi":"10.1029/2024JD041022","DOIUrl":"https://doi.org/10.1029/2024JD041022","url":null,"abstract":"<p>It is well-established that large eddies significantly influence the turbulent transport of heat and scalars in the atmospheric surface layer. However, the mechanistic understanding of how large eddies originating from both the ground (updrafts) and aloft (downdrafts) regulate flux convergence (FC) and divergence (FD) remains relatively unexplored. Based on turbulence data measured at 12 levels, spanning from 1.2 to 60.5 m above the ground, we observe a notable increase in the variability of sensible heat flux magnitudes with height. Our results show that FC and FD of sensible heat are primarily linked to variations in the respective transport efficiencies (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>γ</mi>\u0000 <mrow>\u0000 <mi>w</mi>\u0000 <mi>θ</mi>\u0000 </mrow>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${gamma }_{wtheta }$</annotation>\u0000 </semantics></math>) at different heights. Using the cross-wavelet transform, we find that in FC cases, the regions with high wavelet coherence expand with height, resulting in higher <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>γ</mi>\u0000 <mrow>\u0000 <mi>w</mi>\u0000 <mi>θ</mi>\u0000 </mrow>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${gamma }_{wtheta }$</annotation>\u0000 </semantics></math> at higher levels compared to low ones. Conversely, in FD cases, the regions with high wavelet coherence decrease with height, leading to lower <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>γ</mi>\u0000 <mrow>\u0000 <mi>w</mi>\u0000 <mi>θ</mi>\u0000 </mrow>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${gamma }_{wtheta }$</annotation>\u0000 </semantics></math> at higher levels. Large eddies with length scales of approximately 120–500 m have a significant impact on amplifying or attenuating <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>γ</mi>\u0000 <mrow>\u0000 <mi>w</mi>\u0000 <mi>θ</mi>\u0000 </mrow>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${gamma }_{wtheta }$</annotation>\u0000 </semantics></math> at higher levels compared to lower levels. Using conditional sampling to extract the updrafts and downdrafts of large eddies, distinct patterns are observed in the characterist","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 1","pages":""},"PeriodicalIF":3.8,"publicationDate":"2024-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JD041022","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143121350","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Use of Satellite, Surface Observations and Numerical Weather Prediction Model Data to Improve Cloud Base Height and Cloud Base Vertical Velocity Estimation","authors":"David T. Haliczer,&nbsp;John R. Mecikalski,&nbsp;Pavlos Kollias","doi":"10.1029/2024JD041853","DOIUrl":"https://doi.org/10.1029/2024JD041853","url":null,"abstract":"<p>Cloud base height (CBH) and cloud base vertical velocity (CBVV) are important variables that impact the overall climate in a region as they influence the formulation, longevity, and evolution of clouds. Retrieval of both parameters have long used ground instrumentation (e.g., Doppler lidar (DL), ground base radar); however, retrieving CBH from satellites is particularly challenging given that space-based instruments only observe cloud tops. In this manuscript, CBH is retrieved using a multi-linear regression equation, while CBVV used a random forests model. Both retrievals combine satellite and numerical weather prediction data. The satellite data used are the Visible Infrared Imaging Radiometer Suite imagery, while measurements of CBH and CBVV include DL and radiosonde data at the Southern Great Plains (SGP) Atmospheric Radiation Measurement observatory. Data from 83 summer days (May-August) in 2018–2021 featuring cumulus clouds forced by solar heating were examined and used to train the models, with years 2022–2023 used for validation. Various spatial domains were defined with one large (2.4° longitude by 2.0° latitude) SGP domain being split into smaller sections (smallest being 0.99° and 0.61° longitude and latitude respectably). CBH and CBVV values obtained from the DL as compared to the models show root mean square errors between 150 and 200 m, with CBVV values between 0.45 and 1 ms⁻¹. It was found that the CBH formulation performs well over all domains, while the CBVV retrievals become less accurate due to more turbulence being introduced into the observations as the number of DL stations decreases in the smaller domains.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 1","pages":""},"PeriodicalIF":3.8,"publicationDate":"2024-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143121507","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}

{"title":"Eurasian Snow Anomaly Amplifying the Effect of North Atlantic SST on Interannual Occurrences of Spring Frosts Over Northeast China","authors":"Xinyao Lang,&nbsp;Huopo Chen","doi":"10.1029/2024JD042374","DOIUrl":"https://doi.org/10.1029/2024JD042374","url":null,"abstract":"<p>The spring frost over northeast China significantly affects local socioeconomic development; however, the variations and underlying mechanisms remain unclear. The present study explored the spatiotemporal attributes of spring frost days (FD) over northeast China in recent decades, and the potential mechanisms underlying their interannual variations. The results indicated an evident decline in spring FD over northeast China, accompanied by substantial interannual variation. Further analyses suggested that anomalous springtime North Atlantic tripole sea surface temperature (SST) and Eurasian snow depth are critical factors controlling the interannual variations of spring FD in northeast China. Rossby wave trains can be stimulated by the anomalous North Atlantic tripole SST (NAT), which propagates eastward through the Eurasian continent to northeast China, significantly affecting the atmospheric circulation along the pathways. This results in anomalous negative geopotential heights and cyclonic circulation over northeast China, causing low-temperature anomalies by moderating wind-induced alterations in surface heat fluxes and cloud-induced modifications in surface radiation. Meanwhile, Eurasian snow depth anomalies represent a consistent effect with NAT. The anomalous Eurasian snow depth may modify the atmosphere thickness by regulating surface heat flux, promoting the propagation of wave trains as a snow-atmosphere bridge, which enhances the impact of NAT on FD. In addition, it also triggers the Rossby wave trains to spread from high-latitude Siberia to northeast China. Both of these processes have a considerable impact on the local atmospheric circulation. Consequently, these two factors contribute to local surface cooling, thereby increasing the spring frost occurrence over northeast China.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 1","pages":""},"PeriodicalIF":3.8,"publicationDate":"2024-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143120971","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}

{"title":"Insight Into the Molecular Photooxidation Evolution Mechanism of Brown Carbon Released From Residential Solid Fuel Combustion","authors":"Diwei Wang,&nbsp;Zhenxing Shen,&nbsp;Gezi Bai,&nbsp;Leiming Zhang,&nbsp;Shasha Huang,&nbsp;Jian Sun,&nbsp;Hongmei Xu,&nbsp;Junji Cao","doi":"10.1029/2024JD041827","DOIUrl":"https://doi.org/10.1029/2024JD041827","url":null,"abstract":"<p>Solid fuels were one of the important emission sources of brown carbon (BrC). This study investigates molecular composition of BrC derived from combustion of five types of residential solid fuels (i.e., firewood, corn cob, bituminous coal, anthracite, and biomass briquette) and their photooxidation evolution mechanisms using an oxidation flow reactor. Results show that nitrogen-containing and sulfur-containing organic compounds are the main components of molecular composition of methanol-soluble organic compounds (MSOC) emitted from these fuels, with their intensity being 33%–43% and 23%–56%, respectively, depending on fuel type. The photooxidation processes mediated by NO₃⋅ and ⋅ OH significantly altered the molecular composition and distribution of aged MSOC. The formation of typical nitrogen-containing BrC chromophores (e.g., nitro-aromatic compounds) also proves the role of NO₃ ⋅ in the photooxidation reaction. However, the photo-enhancement effect of NO₃ ⋅ mediated photooxidation reaction could not offset the destruction of the molecular conjugation degree and aromaticity of BrC by ⋅ OH oxidation, resulting in a significant reduction in the light absorption capacity of BrC. The mass absorption coefficient at 365 nm of BrC aged for 12 days derived from the remaining fuels decreased by 47.0%–55.8% compared to that of fresh BrC, except for firewood, which only decreased by 5.3%. These findings on the molecular evolution and oxidation mechanism of BrC generated from solid fuels are useful in reducing uncertainties in climate change studies involving BrC aerosol.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 1","pages":""},"PeriodicalIF":3.8,"publicationDate":"2024-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143120793","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}

{"title":"On the Quantification of Thermodynamic Phases of Raining Clouds: Insights From Multi-Year CloudSat and Ground-Based Radar Observations Over Longmen, Southern China","authors":"Qinghui Li,&nbsp;Haoran Li,&nbsp;Xuejin Sun,&nbsp;Zheng Ruan,&nbsp;Liping Liu,&nbsp;Wenhua Gao,&nbsp;Chenxi Liao,&nbsp;Han Ding","doi":"10.1029/2024JD041824","DOIUrl":"https://doi.org/10.1029/2024JD041824","url":null,"abstract":"<p>The thermodynamic phase of clouds is fundamental to rain initiation and development. Although it is well established that majority of rainfall from mid- to-high latitudes originates from ice, there is a lack of consensus on the major thermodynamic phase of raining clouds over low latitudes. Previous CloudSat-based studies have yet reached consistent results on the fraction of ice-phase raining clouds <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mfenced>\u0000 <msub>\u0000 <mi>F</mi>\u0000 <mi>ice</mi>\u0000 </msub>\u0000 </mfenced>\u0000 </mrow>\u0000 <annotation> $left({F}_{mathit{ice}}right)$</annotation>\u0000 </semantics></math> over Southern China. In this work, we found that CloudSat-based approaches are subject to metrics used for flagging rainfall events, which may lead to different <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>F</mi>\u0000 <mi>ice</mi>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${F}_{mathit{ice}}$</annotation>\u0000 </semantics></math> estimates. Analysis of multi-year surface radar observations suggests that <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>F</mi>\u0000 <mi>ice</mi>\u0000 </msub>\u0000 </mrow>\u0000 <annotation> ${F}_{mathit{ice}}$</annotation>\u0000 </semantics></math> has diurnal variation and increases with rain rate, while the surface rainfall originating from warm clouds does not exceed 50 <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>m</mi>\u0000 <mi>m</mi>\u0000 <mo>/</mo>\u0000 <mi>h</mi>\u0000 </mrow>\u0000 <annotation> $mathrm{m}mathrm{m}/mathrm{h}$</annotation>\u0000 </semantics></math>. Using disdrometer observations to flag surface rainfall events, we found that about 71<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>%</mi>\u0000 </mrow>\u0000 <annotation> $%$</annotation>\u0000 </semantics></math> and 95<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>%</mi>\u0000 </mrow>\u0000 <annotation> $%$</annotation>\u0000 </semantics></math> of surface rainfall events and rainfall accumulation come from cold clouds, respectively. In addition, the observed rainfall accumulations over Longmen are consistent with the fifth generation atmospheric reanalysis (ERA5), whereas the frequency of warm rainfall over Longmen is significantly underestimated in ERA5.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 1","pages":""},"PeriodicalIF":3.8,"publicationDate":"2024-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143120965","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}

{"title":"Exploring Surface-Enhanced Heterogeneous Oxidation of Isoprene: Evidence for Atmospheric Haze Chemistry","authors":"Haiwei Li,&nbsp;Jingyi Li,&nbsp;Wingkei Ho,&nbsp;Long Cui,&nbsp;Ming Wang,&nbsp;Yunjiang Zhang,&nbsp;Junfeng Wang,&nbsp;Hongli Wang,&nbsp;Cheng Huang,&nbsp;Qingyan Fu,&nbsp;Yuanchun Jiang,&nbsp;Mindong Chen,&nbsp;Hong Liao,&nbsp;Junji Cao,&nbsp;Shun-cheng Lee,&nbsp;Xinlei Ge,&nbsp;Yu Huang,&nbsp;Judith C. Chow,&nbsp;John G. Watson","doi":"10.1029/2024JD042439","DOIUrl":"https://doi.org/10.1029/2024JD042439","url":null,"abstract":"<p>Solid atmospheric particulates can act as heterogeneous drivers for gas loss and particle aging during haze episodes. Observational and experimental evidence reveals an unidentified competitive mechanism involving transition metal ions (TMIs) that catalyze the heterogeneous oxidation of isoprene. Hydroxyl radicals (OH) were generated through the reaction of singlet oxygen (O(¹D)) with molecular water at the surface of earth-abundant manganese (Mn) nanoparticles. The energy threshold for OH production was minimized to 213 kJ mol⁻¹ in the presence of alkali K⁺ ions, significantly lower than the 392 kJ mol⁻¹ required for ozone photolysis. The rapid loss of isoprene (1.60 × 10⁻² s⁻¹) for the particulate mixtures resulted in the formation of approximately 70% C₁–C₄ carbonyl oligomers via interfacial binding modes, which promoted particle growth. This contrasts with the higher yields of C₅ products typically observed in gas-phase reactions of isoprene with OH radicals. The findings could enhance the understanding of severe haze formation, particularly under complex air pollution conditions.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 1","pages":""},"PeriodicalIF":3.8,"publicationDate":"2024-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143120792","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}

{"title":"The Observed and Simulated Evolution of a Microburst Using X-Band Phased-Array Radar Data Assimilation With EnKF","authors":"Yiqing Zhu,&nbsp;Ang Zhou,&nbsp;Kun Zhao,&nbsp;Yinghui Lu,&nbsp;Hao Huang","doi":"10.1029/2024JD042614","DOIUrl":"https://doi.org/10.1029/2024JD042614","url":null,"abstract":"<p>A microburst is a severe small-scale meteorological event that develops rapidly, producing intense downdrafts that result in catastrophic divergent winds near the ground. The fine-scale structure and evolution of real-case microbursts are rarely analyzed due to the limitation of regular observational platforms and the computational capacity for numerical simulations. On 12 September 2020, a microburst was effectively captured by China's S-band operational weather radar network and an X-band polarimetric phased-array radar (XPAR). XPAR observations can identify precursor signatures of the rapidly evolving microburst before the occurrence of surface wind disasters, demonstrating superior spatiotemporal resolution in monitoring compared to the S-band radars. To disclose the evolution of small-scale structure and the underlying physical processes, this study utilizes the Weather Research and Forecasting (WRF) model and the ensemble Kalman filter (EnKF) system to assimilate XPAR data. The simulation successfully reproduces the fine-scale structure and evolution of the microburst with a misocyclone. The analysis indicates that the microburst's downdraft is primarily triggered by the middle-level hydrometeor loading. The misocyclone generates a downward-directed perturbation pressure gradient then accelerates the microburst's downdraft toward the surface. This study is the first observation and simulation of a real-case microburst using the WRF-EnKF system assimilating XPAR data. The investigation of the impact of misocyclone on the microburst enhances our understanding of microbursts' forcing mechanism.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 1","pages":""},"PeriodicalIF":3.8,"publicationDate":"2024-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143120733","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}

{"title":"Intermediate-Volatility Organic Compounds (IVOCs) Emissions Based on Source-Specific Emission Ratios Relative to NonMethane Volatile Organic Compounds (NMVOCs) Give Better Representation of the Spatial Distribution of IVOCs in China","authors":"Ning Yang,&nbsp;Qiaoqiao Wang,&nbsp;Qi Xiong,&nbsp;Zeman Fan,&nbsp;Guangjin Liu,&nbsp;Fan Li,&nbsp;Shaowen Zhu,&nbsp;Yaqing Zhou,&nbsp;Jiangchuan Tao,&nbsp;Juan Hong,&nbsp;Hongli Wang,&nbsp;Cheng Huang,&nbsp;Yele Sun,&nbsp;Yafang Cheng,&nbsp;Hang Su,&nbsp;Nan Ma","doi":"10.1029/2024JD041464","DOIUrl":"https://doi.org/10.1029/2024JD041464","url":null,"abstract":"<p>Intermediate-volatility organic compounds (IVOCs) and their contribution to secondary organic aerosols (SOA) in China are simulated in GEOS-Chem with seven newly constructed IVOCs emission inventories (IEIs). The IEIs based on different references and source-specific emission ratios show a large range of emissions in China (4.8–14 Tg yr⁻¹) and also significant differences in major sources and spatial distributions. Among them, the IEI relative to nonMethane volatile organic compounds (NMVOCs) with a total emission of 12 Tg yr⁻¹, dominated by solvent use, better captures observed spatial distributions of IVOCs and SOA. In contrast, IEIs relative to primary organic aerosols (POA) misinterpret the major sources and tend to have a negative bias in megacities even when the total emission is scaled up to 14 Tg yr⁻¹. The study indicates that previous studies have underestimated IVOCs emission and hence the contribution to SOA. It also demonstrates the importance of using an appropriate reference to better represent the major sources and the spatial distribution of IVOCs.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 1","pages":""},"PeriodicalIF":3.8,"publicationDate":"2024-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143120734","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}

{"title":"Influence of Vortex Couplets Following Cold Fronts Related to the Lateral Friction by Mountains on Elevated Thunderstorm Initiation","authors":"Xinyue Luo,&nbsp;Xiaogang Huang,&nbsp;Jianfang Fei,&nbsp;Ju Wang,&nbsp;Chao Li,&nbsp;Xiaoping Cheng","doi":"10.1029/2024JD041987","DOIUrl":"https://doi.org/10.1029/2024JD041987","url":null,"abstract":"<p>Convective initiation (CI) over complex terrain poses a difficult problem. By conducting numerical simulations and surface friction experiments, this study investigated the dynamic mechanism of elevated thunderstorm initiation on the eastern side of Dalou Mountain. The evolution characteristics of vortices before and after CI, as well as the impact of lateral friction of the mountain on the formation of vortices, were assessed. Simulation results showed that a pair of vortex couplets following the cold front (CFVs) were associated with lateral friction of the terrain, where the northern and southern sides experienced anticyclonic and cyclonic vortices, respectively. Easterly winds between CFVs could be an indication for CI. CFVs had an unsymmetrical structure in the vertical direction, which had a high depth in the south and low depth in the north, and exhibited nocturnal intensification. In the sensitivity experiments, lateral friction showed the positive impact on the low-level easterlies from afternoon to evening, following the rule that the greater the surface lateral friction, the stronger the easterly. The promotion of positive vorticity in the southern vortex by lateral friction was obviously above 1,500 m, while the enhancement of negative vorticity in the northern vortex was mainly reflected in the low-level layer. The variation of the latter was not as large as that of the former due to the difference of the south and the north terrain. These results provide an important perspective on the qualitative relationship between the lateral friction, vortex couplets, and airflow intensity.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 1","pages":""},"PeriodicalIF":3.8,"publicationDate":"2024-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143120742","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}

{"title":"Mechanisms for the Influence of the MJO on Precipitation in Southwestern South America","authors":"F. Matus,&nbsp;R. Rondanelli,&nbsp;J. Rutllant,&nbsp;S. Henderson","doi":"10.1029/2024JD041935","DOIUrl":"https://doi.org/10.1029/2024JD041935","url":null,"abstract":"<p>During austral winter under neutral ENSO conditions, positive precipitation anomalies in Southwestern South America from 30<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> ${}^{circ}$</annotation>\u0000 </semantics></math> to 45<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>°</mo>\u0000 </mrow>\u0000 <annotation> ${}^{circ}$</annotation>\u0000 </semantics></math>S coincide with strong real-time multivariate MJO (RMM) Phase 1 events. Using ERA5 composites arranged according to active RMM phases, we found that a three-part mechanism, traced approximately 10–15 days before MJO Phase 1 events, roughly corresponding to RMM phases 7 and 8, explains these precipitation anomalies. This mechanism is composed of three Rossby wave trains in response to convective perturbations: two cross equatorial teleconnections attributed to suppressed convection in the Indian Ocean and the Maritime Continent, and an interhemispheric Rossby wave linked to enhanced convection over the warm pool of the western hemisphere. Composite analyses of OLR and wave activity flux, complemented with Rossby wave ray tracing, support these findings. This research provides insights into the MJO's influence on additional large-scale teleconnection patterns across the Southern Hemisphere besides the Pacific South American (PSA) teleconnection mode. The dispersion of the convective RMM phase at different lags and the interaction between multiple wave trains introduce uncertainty when associating a specific RMM phase with precipitation anomalies.</p>","PeriodicalId":15986,"journal":{"name":"Journal of Geophysical Research: Atmospheres","volume":"130 1","pages":""},"PeriodicalIF":3.8,"publicationDate":"2024-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143120744","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}