Monthly Weather Review最新文献

{"title":"Interaction of the Monsoon Trough and Western Disturbance Ignites Multiday Extreme Rainfall Event in July 2023 over North India","authors":"Rohtash Saini, Raju Attada, Kieran M. R. Hunt, Sreehari Kizhuveettil, Deepak Pandidurai","doi":"10.1175/mwr-d-25-0147.1","DOIUrl":"https://doi.org/10.1175/mwr-d-25-0147.1","url":null,"abstract":"Abstract The present paper aims to investigate the atmospheric processes that led to extreme rainfall resulting in destructive flash flooding and loss of life and property in the northwestern region of India on 8–9 July 2023. Exceptionally heavy precipitation occurred in the western Himalaya and adjoining regions, leading to widespread disruption of communication, electricity, and inundation of houses. Flash floods, combined with debris flows, caused massive devastation in northern India, with the overall death toll surging to 91. Records from automatic weather stations highlight the severity of the event, with several stations breaking 20-yr records. This study examines the synoptic drivers, dynamic and thermodynamical features associated with the rainfall episode. Prior to the extreme precipitation, the monsoon trough migrated northward, and its interaction with an incoming western disturbance (WD) passing over northwest India led to deep tropospheric instability over the western Himalaya. The dynamic coupling of the monsoon trough with an unusually strong and slow-moving WD, caused by an extratropical cutoff low, facilitated moisture exchange, which further intensified, resulting in a severe rainstorm. The high moisture convergence was driven by extremely high amounts of moisture flux directed from the Bay of Bengal and the Arabian Sea toward the western Himalaya by the combined monsoon trough–WD system. Alongside this, an intense jet streak associated with the WD led to additional ageostrophic forcing over the western Hindukush Himalayas from 7 July, creating conducive conditions for deep ascent. Vorticity and moisture budget analyses highlight the main dynamical drivers (horizontal vorticity advection and vertical moisture transport) of the event.","PeriodicalId":18824,"journal":{"name":"Monthly Weather Review","volume":"154 2","pages":"183-201"},"PeriodicalIF":0.0,"publicationDate":"2025-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147920513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 Sensitivity of Falling Hail to Different Melting and Terminal Velocity Parameterizations and Environmental Conditions","authors":"Hannah C. Vagasky, Rebecca Adams‐Selin, Sarah D. Bang, Andrew J. Heymsfield, Aaron Bansemer","doi":"10.1175/mwr-d-24-0180.1","DOIUrl":"https://doi.org/10.1175/mwr-d-24-0180.1","url":null,"abstract":"Abstract The processes that dictate hail melt and hail terminal velocity are complex, poorly understood, and important to the characteristics of the hail that ultimately reaches the ground. Multiple parameterizations describing hail melt and terminal velocity have been developed since the 1960s. However, there has never been a systematic comparison of these parameterizations and how they respond to different environments. The current study combines unique in-cloud hail size distribution data with a melt-only, one-dimensional version of the HAILCAST hail trajectory model, termed HAILMELT, to explore how different hail melt (HMP) and terminal velocity (TVP) parameterizations simulate falling hail in the midlatitudes and tropics. We also explore how sensitive the falling hail is to temperature, moisture, and in-cloud vertical velocity changes. For hail smaller than 40 mm, simulations are frequently at least as sensitive, and often more sensitive, to which parameterization is used than to changes in the environmental conditions. In tropical oceanic environments, results suggest that hail initially smaller than 10 mm requires unrealistically cool or dry conditions to reach the surface. However, initially larger hailstones in tropical environments are shown to be capable of reaching the surface. These results indicate that there are likely larger uncertainties than previously understood in our hail simulations of the current and future climate. Additionally, they suggest all the hail identified by satellite-based hail climatologies in the tropics entirely melts before reaching the surface in some cases. Significance Statement This study is the first systematic comparison of different hail melt and hail fall speed relationships in the midlatitudes and tropics. It explores the environmental sensitivity of these relationships for hail smaller than 40 mm. The amount that hailstones melt is often more sensitive to which relationship is being used than to changes in environmental conditions. This sensitivity likely adds additional uncertainty to simulations that predict the size of hail. We also show that the initial in-cloud hailstone sizes have a larger impact on determining if hail will reach the surface in the tropics than the environmental conditions.","PeriodicalId":18824,"journal":{"name":"Monthly Weather Review","volume":"153 11","pages":"2535-2554"},"PeriodicalIF":0.0,"publicationDate":"2025-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147917369","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Predicting fibrosis progression in non-alcoholic fatty liver disease patients using the FAST Score: A paired biopsy study.","authors":"Nisanur Sariyar, Haluk Tarik Kani, Cigdem Ataizi Celikel, Yusuf Yilmaz","doi":"10.14744/hf.2023.2023.0021","DOIUrl":"10.14744/hf.2023.2023.0021","url":null,"abstract":"<p><strong>Background and aim: </strong>This study aimed to investigate the predictive value of various non-invasive scores for identifying the progression of hepatic fibrosis over time in patients with Non-Alcoholic Fatty Liver Disease (NAFLD).</p><p><strong>Materials and methods: </strong>We examined 69 patients with NAFLD who had undergone two liver biopsies at an average interval of 21.3±9.7 months. Progression and regression of fibrosis were defined as an increase or decrease of at least one stage in fibrosis between the initial and follow-up biopsies, respectively. The Fibrosis-4 Index (FIB-4), NAFLD Fibrosis Score (NFS), Agile 3+, Agile 4, and FibroScan-AST (FAST) scores were calculated at the initial biopsy.</p><p><strong>Results: </strong>Comparison of paired biopsies revealed that 45% of participants (n=31) exhibited no change in fibrosis stages, 26% (n=18) experienced progression, and 29% (n=20) demonstrated regression. Multivariable logistic regression analysis identified the FAST score as the only independent predictor of progressive fibrosis, with the odds increasing by 19% (95% CI: 8-38%, p<0.05) for each unit increase in the FAST score at the initial biopsy. No independent predictors for fibrosis regression were identified.</p><p><strong>Conclusion: </strong>Higher baseline FAST scores were associated with an increased likelihood of fibrosis progression, independent of other variables. Thus, the FAST score could serve as both a diagnostic and prognostic tool for fibrosis in patients with NAFLD.</p>","PeriodicalId":18824,"journal":{"name":"Monthly Weather Review","volume":"53 1","pages":"33-36"},"PeriodicalIF":1.2,"publicationDate":"2024-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10809337/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86752815","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"Improvement of albedo and snow-cover simulation during snow events over the Tibetan Plateau","authors":"Lian Liu, Yaoming Ma","doi":"10.1175/mwr-d-23-0083.1","DOIUrl":"https://doi.org/10.1175/mwr-d-23-0083.1","url":null,"abstract":"\u0000The snow albedo is a vital component of land–atmosphere coupling models. It plays a critical role in regulating land surface energy exchange by controlling incoming solar radiation absorbed by the land surface and influencing the timing and rate of snowmelt. Accurate snow albedo simulation is essential to obtain surface energy balance and snow-cover estimates. Here, the simulation of albedo and snow cover using the Weather Research and Forecasting model and an improved snow albedo scheme is verified against satellite-retrieved products during and immediately following eight snowfall events over the Tibetan Plateau. The improved model successfully characterizes the spatial pattern and inverted U-shaped temporal pattern of albedo over the entire Tibetan Plateau. This is attributed to the local optimization of snow-age parameters and explicit consideration of snow depth in the improved scheme. Compared with the previous model, the model proposed herein greatly decreases the overestimated albedo (by 0.13–0.27), yielding a bias range of ± 0.08, mean relative bias decrease of 70%, and significant increase in the spatial correlation coefficient of 0.03–0.39 (mean: 0.13). The significant improvements of albedo estimates appear in deep snow-covered regions, largely attributed to parameter optimization related to snow albedo decay, while less improvements appear over the shallow snow-covered regions. Accurate reproduction of the spatiotemporal variation in albedo alleviated snow-cover overestimation by small amounts. For snow-cover estimates, the improved model consistently decreases the false-alarm rate by 0.03, and increases the overall accuracy and equitable threat score by 0.04 and 0.03, respectively. Moreover, the improved scheme shows an equivalent improvement of albedo estimates at both 1- and 5-km grid spacing over the eastern Tibetan Plateau; this is also true for snow-cover estimates.","PeriodicalId":18824,"journal":{"name":"Monthly Weather Review","volume":"36 28","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139442741","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influences of the South American Low-Level Jet on the Convective Environment in Central Argentina using a Convection-Permitting Simulation","authors":"Clayton R.S. Sasaki, Angela K. Rowe, L. McMurdie, A. Varble, Zhixiao Zhang","doi":"10.1175/mwr-d-23-0122.1","DOIUrl":"https://doi.org/10.1175/mwr-d-23-0122.1","url":null,"abstract":"\u0000This study documents the spatial and temporal distribution of the South American low-level jet (SALLJ) and quantifies its impact on the convective environment using a 6.5-month convection-permitting simulation during the Remote Sensing of Electrification, Lightning, And Mesoscale/Microscale Processes with Adaptive Ground Observations and Clouds, Aerosols, and Complex Terrain Interactions (RELAMPAGO-CACTI) campaigns. Overall, the simulation reproduces the observed SALLJ characteristics in Central Argentina near the Sierras de Córdoba (SDC), a focal point for terrain-focused upscale growth. SALLJs most frequently occur in the summer with maxima to the northwest and east of the SDC and minima over the higher terrain. The shallower SALLJs (< 1750 m) have a strong overnight skew, while the elevated jets are more equally spread throughout the day. SALLJ periods often have higher amounts of low-level moisture and instability compared to non-SALLJ periods, with these impacts increasing over time when the SALLJ is present and decreasing afterwards. The SALLJ may enhance low-level wind shear magnitudes (particularly when accounting for the jet height); however, enhancement is somewhat limited due to the presence of speed shear in most situations. SALLJ periods are associated with low-level directional shear favorable for organized convection and an orientation of cloud-layer wind shear parallel to the terrain, which could favor upscale growth. A case study is shown where the SALLJ influenced both the magnitude and direction of wind shear concurrent with convective upscale growth near the SDC. This study highlights the complex relationship between the SALLJ and its impacts during periods of widespread convection.","PeriodicalId":18824,"journal":{"name":"Monthly Weather Review","volume":"20 4","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139445476","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Orographic Controls on Extreme Precipitation associated with a Mei-yu Front","authors":"Ian C. Cornejo, Angela K. Rowe, Kristen L. Rasmussen, Jennifer C. DeHart","doi":"10.1175/mwr-d-23-0170.1","DOIUrl":"https://doi.org/10.1175/mwr-d-23-0170.1","url":null,"abstract":"\u0000Taiwan regularly receives extreme rainfall due to seasonal Mei-yu fronts that are modified by Taiwan’s complex topography. One such case occurred between 1-3 June 2017 when a Mei-yu front contributed to flooding and landslides from over 600 mm of rainfall in 12 hours near Taipei basin, and over 1500 mm of rainfall in 2 days near the Central Mountain Range (CMR). This Mei-yu event is simulated using the Weather Research and Forecasting (WRF) model with halved terrain as a sensitivity test to investigate the orographic mechanisms that modify the intensity, duration, and location of extreme rainfall. The reduction in WRF terrain height produced a decrease in rainfall duration and accumulation in northern Taiwan and a decrease in rainfall duration, intensity, and accumulation over the CMR. The reductions in northern Taiwan are linked to a weaker orographic barrier jet resulting from a lowered terrain height. The reductions in rainfall intensity and duration over the CMR are partially explained by a lack of orographic enhancements to Mei-yu frontal convergence near the terrain. A prominent feature missing with the reduced terrain is a redirection of postfrontal westerly winds attributed to orographic deformation, i.e., the redirection of flow due to upstream topography. Orographically deforming winds converge with prefrontal flow to maintain the Mei-yu front. In both regions, the decrease in Mei-yu front propagation speed is linked to increased rainfall duration. These orographic features will be further explored using observations captured during the 2022 Prediction of Rainfall Extremes Campaign in the Pacific (PRECIP) field campaign.","PeriodicalId":18824,"journal":{"name":"Monthly Weather Review","volume":"12 12","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139381956","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 Response of Precipitation to Initial Soil Moisture over the Tibetan Plateau: Respective Effects of Boundary Layer Vertical Heat and Vapor Diffusions","authors":"Feimin Zhang, Kaixuan Bi, Sentao Wei, Chenghai Wang","doi":"10.1175/mwr-d-23-0025.1","DOIUrl":"https://doi.org/10.1175/mwr-d-23-0025.1","url":null,"abstract":"\u0000This study investigates the influences of initial soil moisture over the Tibetan Plateau (TP) on precipitation simulation, and the respective effects of boundary layer vertical diffusion for heat (Kh) and vapor (Kq). Results indicate that the responses of boundary layer vertical diffusion to soil moisture are obvious mainly in the daytime. Wetter land surface corresponds to weaker vertical diffusion, which could strengthen thermal forcing and dynamic lifting in the lower atmosphere, and encourage water vapor saturation near the top of boundary layer to prevent the environmental dry air entrainment/invasion, these would be beneficial to more convection and precipitation. Wetter land surface over the TP could enhance the contrast between the cold in the northwestern TP and the warm in the southeastern TP, which would be conducive to the southeastward propagation of precipitation.\u0000The simulation of heat and moisture in the boundary layer could be improved by perturbing the relative intensity of Kh and Kq. From the perspective of heat and moisture, Kh affects atmospheric stability, while Kq affects moisture and its vertical transport in the boundary layer. The Kh and Kq have competitive effects on precipitation intensity by influencing relative importance of moisture and atmospheric stability conditions in the boundary layer. Adjusting the relative intensity of Kh and Kq would deactivate the competitive effects. Stronger Kh but weaker Kq would alleviate the overestimated precipitation by inhibiting vertical transport of moisture to the top of boundary layer and attenuating convective instability in the boundary layer.","PeriodicalId":18824,"journal":{"name":"Monthly Weather Review","volume":"32 14","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139389295","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evaluation of Parametric Tropical Cyclone Surface Winds over the Eastern Australian Region","authors":"Julian O’Grady, Hamish Ramsay, Kathy McInnes, Rebecca Gregory","doi":"10.1175/mwr-d-23-0063.1","DOIUrl":"https://doi.org/10.1175/mwr-d-23-0063.1","url":null,"abstract":"\u0000Hazard studies based on thousands of synthetic tropical cyclone (TC) events require a validated model representation of the surface wind field. Here, we assess three different TC parametric vortex models with input from four along-track parameter studies of the TC size and shape, based on statistical formulation of the relationships to observed TC intensity, geographic location, and forward transition speed. The 12 model combinations are compared to in situ 10-min observed surface mean wind speeds for 10 TCs that made landfall over Queensland, Australia, which occurred over the period 2006–17. Empirical wind reduction factors to reduce gradient winds to the surface are recalculated for the more recent TCs at both offshore (ocean, small islands, reefs, and moorings) and onshore (land) locations. To improve the wind comparisons over ocean and land, a secondary reduction factor was developed based on an inland decay function. Pearson correlations for the unadjusted modeled peak wind speed from 118 instances of a TC passing a weather station sit between a range of 0.57 and 0.65 for the 12 model combinations. Using the secondary reduction factor based on the inland decay function increases the range of correlation to 0.74–0.81. Based on the assessment of the instances of peak surface wind speed correlations, bias, and root-mean-square error, along with the correlation 48 h around the peak, the top-ranked performing model combination for the region was an along-track parameter study with a double-vortex model, both previously tested for the South Pacific basin.\u0000\u0000\u0000When assessing tropical cyclone hazards, users are presented with several simplified parametric models to describe the surface wind field of tropical cyclones. These parametric models are used routinely for risk assessment of cyclonic winds, as well as for input to surge and wave models used in coastal hazard assessments. Differences between the models include the formulation of the parametric cyclone model, the way winds above the boundary layer are specified at the surface and along-track parameters that describe the cyclones’ size and shape. Of the 12 model combinations investigated in this study, the top-ranked performing model combination for the region was an along-track parameter equation with a double-vortex model, which were both tested previously for the South Pacific basin. Analysis is performed to show unadjusted modeled winds overestimate observed 10-min surface winds over the ocean by around 13% (median) and over land by around 73.9% (median), which is resolved in this study with a secondary empirical wind reduction factor. These findings will support future modeling of tropical cyclone winds for multiple applications, including regional risk assessment and coastal hazard studies.","PeriodicalId":18824,"journal":{"name":"Monthly Weather Review","volume":"8 5","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139394955","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Diagnosing flavors of tropospheric Rossby wave breaking and their associated dynamical and sensible weather features","authors":"Grant LaChat, K. Bowley, Melissa Gervais","doi":"10.1175/mwr-d-23-0153.1","DOIUrl":"https://doi.org/10.1175/mwr-d-23-0153.1","url":null,"abstract":"\u0000Rossby wave breaking (RWB) can be manifested by the irreversible overturning of isentropes on constant potential vorticity (PV) surfaces. Traditionally, the type of breaking is categorized as anticyclonic (AWB) or cyclonic (CWB) and can be identified using the orientation of streamers of high potential temperature (θ) and low θ air on a PV surface. However, an examination of the differences in RWB structure and their associated tropospheric impacts within these types remains unexplored. In this study, AWB and CWB are identified from overturning isentropes on the dynamic tropopause (DT), defined as the 2 potential vorticity unit (PVU) surface, in the ERA5 reanalysis dataset during December, January, and February 1979–2019. Self-organizing maps (SOM), a machine learning method, is used to cluster the identified RWB events into archetypal patterns, or “flavors”, for each type. AWB and CWB flavors capture variations in the θ minima/maxima of each streamer and the localized meridional θ gradient (∇θ) flanking the streamers. Variations in the magnitude and position of ∇θ between flavors correspond to a diversity of jet structures leading to differences in vertical motion patterns and troposphere-deep circulations. A subset of flavors of AWB (CWB) events are associated with the development of strong surface high (low) pressure systems and the generation of extreme poleward moisture transport. For CWB, many events occurred in similar geographical regions, but the precipitation and moisture patterns were vastly different between flavors. Our findings suggest that the location, type, and severity of the tropospheric impacts from RWB are strongly dictated by RWB flavor.","PeriodicalId":18824,"journal":{"name":"Monthly Weather Review","volume":" February","pages":""},"PeriodicalIF":3.2,"publicationDate":"2023-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138960588","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Shear-Relative Asymmetric Kinematic Characteristics of Intensifying Hurricanes as Observed by Airborne Doppler Radar","authors":"Udai Shimada, P. Reasor, Robert F. Rogers, Michael S. Fischer, Frank D. Marks, Jonathan A. Zawislak, Jun A. Zhang","doi":"10.1175/mwr-d-22-0340.1","DOIUrl":"https://doi.org/10.1175/mwr-d-22-0340.1","url":null,"abstract":"While recent observational studies of intensifying (IN) versus steady-state (SS) hurricanes have noted several differences in their axisymmetric and asymmetric structures, there remain gaps in the characterization of these differences in a fully three-dimensional framework. To address these limitations, this study investigates differences in the shear-relative asymmetric structure between IN and SS hurricanes using airborne Doppler radar data from a dataset covering an extended period of time. Statistics from individual cases show that IN cases are characterized by peak wavenumber-1 ascent concentrated in the upshear-left (USL) quadrant at ~12-km height, consistent with previous studies. Moderate updrafts (2–6 m s−1) occur more frequently in the downshear eyewall for IN cases than for SS cases, likely leading to a higher frequency of moderate to strong updrafts USL above 9-km height. Composites of IN cases show that low-level outflow from the eye region associated with maximum wavenumber-1 vorticity inside the radius of maximum wind (RMW) in the downshear-left quadrant converges with low-level inflow outside the RMW, forming a stronger local secondary circulation in the downshear eyewall than SS cases. The vigorous eyewall convection of IN cases produces a net vertical mass flux increasing with height up to ~5-km and then is almost constant up to 10 km, whereas the net vertical mass flux of SS cases decreases with height above 4 km. Strong USL upper-level ascent provides greater potential for the vertical development of the hurricane vortex, which is argued to be favorable for continued intensification in shear environments.","PeriodicalId":18824,"journal":{"name":"Monthly Weather Review","volume":"111 ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139175996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}