Atmospheric Science Letters最新文献

{"title":"The link between North Atlantic tropical cyclones and ENSO in seasonal forecasts","authors":"Robert Doane-Solomon,&nbsp;Daniel J. Befort,&nbsp;Joanne Camp,&nbsp;Kevin Hodges,&nbsp;Antje Weisheimer","doi":"10.1002/asl.1190","DOIUrl":"10.1002/asl.1190","url":null,"abstract":"<p>This study assesses the ability of six European seasonal forecast models to simulate the observed teleconnection between ENSO and tropical cyclones (TCs) over the North Atlantic. While the models generally capture the basin-wide observed link, its magnitude is overestimated in all forecast models compared to reanalysis. Furthermore, the ENSO-TC relationship in the Caribbean is poorly simulated. It is shown that incorrect forecasting of wind shear appears to affect the representation of the teleconnection in some models, however it is not a completely sufficient explanation for the overestimation of the link.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"25 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1190","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136374216","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Boundary layer profile of decaying and non-decaying tropical storms near landfall","authors":"Enoch Yan Lok Tsui,&nbsp;Pak Wai Chan,&nbsp;Ralf Toumi","doi":"10.1002/asl.1189","DOIUrl":"10.1002/asl.1189","url":null,"abstract":"<p>The vertical profile of the wind structure of translating tropical cyclones, including the associated azimuthal asymmetry, has been the subject of existing theoretical and observational studies using dropsondes. Most of these studies are based on data collected from relatively strong cyclones over the Atlantic. Here we explore the tropical cyclone boundary layer wind profile of mainly relatively weak landfalling cyclones near Hong Kong. We find that decaying tropical storms have a much larger mid- to low-level inflow angle than those that are intensifying or in steady-state. The inflow angles of intensifying, steady-state and decaying tropical storms converge towards the top of the boundary layer. The wind speed reduces through the boundary layer in a similar way in all three cases. The combination of these factors means that decaying tropical storms have stronger inflow than intensifying and steady-state ones. We attribute these local effects to remote enhanced surface friction over land when the storms are weakening.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"25 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1189","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48313462","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Dynamics of localized extreme heatwaves in the mid-latitude atmosphere: A conceptual examination","authors":"Masoud Rostami,&nbsp;Luca Severino,&nbsp;Stefan Petri,&nbsp;Saeed Hariri","doi":"10.1002/asl.1188","DOIUrl":"10.1002/asl.1188","url":null,"abstract":"<p>This study investigates the adjustment of large-scale localized buoyancy anomalies in mid-latitude regions and the nonlinear evolution of associated condensation patterns in both adiabatic and moist-convective environments. This investigation is carried out utilizing the two-layer idealized moist-convective thermal rotating shallow water (mcTRSW) model. Our investigation reveals that the presence of a circular positive potential temperature anomaly in the lower layer initiates an anticyclonic high-pressure rotation, accompanied by a negative buoyancy anomaly in the upper layer, resulting in an anisotropic northeast–southwest tilted circulation of heat flux. The evolution of eddy heat fluxes, such as poleward heat flux, energy, and meridional elongation of the buoyancy field, heavily depends on the perturbation's strength, size, and vertical structure. The heatwave initiates atmospheric instability, leading to precipitation systems such as rain bands and asymmetric latent heat release due to moist convection in a diabatic environment. This creates a comma cloud pattern in the upper troposphere and a comma-shaped buoyancy anomaly in the lower layer, accompanied by the emission of inertia gravity waves. The southern and eastern sectors of the buoyancy anomaly show an upward flux, generating a stronger cross-equatorial flow and inertia-gravity waves in a southward and eastward direction. Furthermore, the simulations reveal a similar asymmetric pattern of total condensed liquid water content distribution, accompanied by the intensification of moist convection as rain bands. This intensification is more pronounced in barotropic structures than in baroclinic configurations with stagnant upper layers. This study highlights the importance of considering moist convection and its effects on atmospheric and oceanic flows in mid-latitude regions, as well as the role of buoyancy anomalies in generating heatwaves and precipitation patterns.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"25 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1188","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47627760","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Predictability of the East Africa long rains through Congo zonal winds","authors":"Neil Ward,&nbsp;Dean P. Walker,&nbsp;Richard J. Keane,&nbsp;John H. Marsham,&nbsp;Adam A. Scaife,&nbsp;Cathryn E. Birch,&nbsp;Ben Maybee","doi":"10.1002/asl.1185","DOIUrl":"10.1002/asl.1185","url":null,"abstract":"<p>East Africa is highly vulnerable to extreme weather events, such as droughts and floods. Skillful seasonal forecasts exist for the October–November–December short rains, enabling informed decisions, whereas seasonal forecasts for the March–April–May (MAM) long rains have historically had low skill, limiting preparation capacity. Therefore, improved long rains prediction is a high priority and would contribute to climate change resilience in the region. Recent work has highlighted how lower-troposphere Congo zonal winds in MAM strongly impact regional moisture fluxes and the long rains total precipitation. We therefore approach long rains predictability through the predictability of the Congo winds. We analyze a set of hindcasts from a dynamical prediction system that is able to reproduce the long rains—Congo winds relationship in its individual ensemble members. Encouragingly, in observations, the strength of MAM Congo zonal winds and East Africa rainfall show substantial correlation with the MAM Atlantic (including North Atlantic Oscillation, NAO) and Indo-Pacific variability, suggestive of ocean influence and potential predictability. However, these features are replaced by different teleconnections in the hindcast ensemble mean fields. This is also true for NAO linkage to Congo winds, despite correct representation in individual members, and good skill in hindcasting the NAO itself. The net effect is strongly negative skill for the Congo winds. We explore statistical correction methods, including using the Congo zonal wind as an anchor index in a signal-to-noise calibration for the long rains. This is considered a demonstration of concept, for subsequent implementation using models with better Congo zonal wind skill. Indeed, the clear signals found in the Atlantic (including Mediterranean) and Indo-Pacific, studied here both in observations and a dynamical prediction system, motivate evaluation of these features across other prediction systems, and offer the prospect of improved physically-informed long rains dynamical predictions.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"24 12","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1185","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48558989","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Role of updraft in dry-season torrential rainfall in Greater Jakarta, Indonesia","authors":"Asteria Satyaning Handayani,&nbsp;Theodorus Permana,&nbsp;Yuzuru Isoda","doi":"10.1002/asl.1186","DOIUrl":"10.1002/asl.1186","url":null,"abstract":"<p>Coastal urban areas in tropical regions, such as Greater Jakarta (GJ) in Indonesia, are susceptible to flood hazards from torrential rainfall. Efforts to understand the convective mechanisms leading to this type of rainfall have been carried out extensively, especially for events occurring in the wet season. However, hydrometeorological risks persist even in the dry season, when the rainfall is more closely correlated with the diurnal wind circulation. Among the aspects of convective activities and this diurnal circulation, the details of the updraft remain the least studied and open for discussion. We investigate the role of the updraft in urban torrential rainfall over GJ, using data from a C-band Doppler radar and reanalysis dataset during the dry season of 2018–2019. Employing back-trajectory calculations, we locate updraft origins corresponding to the peak of daytime inland rainfall. Most updraft origins are localized at an NW–SE-oriented front nearly parallel to the coastline on the low-lying plain, suggesting a region of atmospheric destabilization favorable for convective activity. The dry-season torrential rainfall over GJ may involve convective activity from this front, that from earlier updrafts originating above the densely populated area, and further enhancement coming from orographic contributions. Our findings suggest the important role of updrafts in the rainfall generation, providing insights into the convective mechanism over GJ.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"24 12","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1186","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42160365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Unravelling the transport of moisture into the Saharan Air Layer using passive tracers and isotopes","authors":"Fabienne Dahinden,&nbsp;Franziska Aemisegger,&nbsp;Heini Wernli,&nbsp;Stephan Pfahl","doi":"10.1002/asl.1187","DOIUrl":"10.1002/asl.1187","url":null,"abstract":"<p>The subtropical free troposphere plays a critical role in the radiative balance of the Earth. However, the complex interactions controlling moisture in this sensitive region and, in particular, the relative importance of long-range transport compared to lower-tropospheric mixing, remain unclear. This study uses the regional COSMO model equipped with stable water isotopes and passive water tracers to quantify the contributions of different evaporative sources to the moisture and its stable isotope signals in the eastern subtropical North Atlantic free troposphere. In summer, this region is characterized by two alternating large-scale circulation regimes: (i) dry, isotopically depleted air from the upper-level extratropics, and (ii) humid, enriched air advected from Northern Africa within the Saharan Air Layer (SAL) consisting of a mixture of moisture of diverse origin (tropical and extratropical North Atlantic, Africa, Europe, the Mediterranean). This diversity of moisture sources in regime (ii) arises from the convergent inflow at low levels of air from different neighbouring regions into the Saharan heat low (SHL), where it is mixed and injected by convective plumes into the large-scale flow aloft, and thereafter expelled to the North Atlantic within the SAL. Remarkably, this regime is associated with a large contribution of moisture that evaporated from the North Atlantic, which makes a detour through the SHL and eventually reaches the 850–550 hPa layer above the Canaries. Moisture transport from Europe via the SHL to the same layer leads to the strongest enrichment in heavy isotopes (δ²H correlates most strongly with this tracer). The vertical profiles over the North Atlantic show increased humidity and δ²H and reduced static stability in the 850–550 hPa layer, and smaller cloud fraction in the boundary layer in regime (ii) compared to regime (i), highlighting the key role of moisture transport through the SHL in modulating the radiative balance in this region.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"24 12","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1187","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49589580","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Regional precipitation index: Method analysis and application over Greece","authors":"K. Lagouvardos,&nbsp;G. Papavasileiou,&nbsp;K. Papagiannaki,&nbsp;S. Dafis,&nbsp;E. Galanaki,&nbsp;T. M. Giannaros,&nbsp;I. Koletsis,&nbsp;V. Kotroni","doi":"10.1002/asl.1184","DOIUrl":"10.1002/asl.1184","url":null,"abstract":"<p>The current work focuses on the development of a regional precipitation index (RPI) to rank precipitation events in Greece, with the goal of identifying the most severe weather events in terms of their potential to cause socioeconomic impacts. The study is motivated by the increasing occurrence of extreme weather events and accompanying hydrogeological phenomena worldwide, which have caused significant infrastructure damage and loss of life. The analysis is based on the exploitation of the ERA-Land high-resolution rainfall dataset, covering the period from 1991 to 2020, while it considers both the area and the population affected by each rainfall event. The study provides a categorization of the ranked storms based on the percentiles of all non-zero RPI values and highlights the socioeconomic impacts of the most severe weather events. The findings suggest that the developed RPI can be a useful tool for early warning systems and risk management strategies, particularly for emergency preparedness and response. The resulting ranking procedure has been applied operationally by the METEO unit of the National Observatory of Athens since fall 2021.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"24 12","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1184","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42081770","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Diurnal variations of tropical cyclone outer region size growth","authors":"Jiacheng Hong,&nbsp;Qiaoyan Wu","doi":"10.1002/asl.1183","DOIUrl":"10.1002/asl.1183","url":null,"abstract":"<p>Various aspects of tropical cyclones (TCs) fluctuate with the diurnal cycle. TC size is critical to the extent of its damage, but diurnal variations in the growth of the outer region size have largely remained unexplored. This paper examines the diurnal variations in the growth of the radius of gale-force winds (34 kt; R34) by analyzing best-track data from 2001 to 2019 for both North Atlantic TCs and global TCs outside of the North Atlantic region. Statistically significant diurnal variations was found for R34 growth, with the maximum 6-h growth rate occurring at 2100–0300 local solar time (LST) for North Atlantic TCs, and at 0300–0900 LST for global TCs excluding the North Atlantic which experienced rapid intensification (≥30 knots within 24 h). The higher R34 6-h growth rates during the night were linked to a larger extent of very deep convective clouds with infrared brightness temperatures &lt;208 K during this time.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"24 12","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1183","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46723428","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"The snow-shadow effect of Sado Island on Niigata City and the coastal plain","authors":"Hiroyuki Kusaka,&nbsp;Nobuyasu Suzuki,&nbsp;Masato Yabe,&nbsp;Hiroki Kobayashi","doi":"10.1002/asl.1182","DOIUrl":"10.1002/asl.1182","url":null,"abstract":"<p>Japan's Hokuriku region, near the Sea of Japan, typically experiences heavy snowfall; however, Niigata City, the largest city on the Sea of Japan side, experiences lower levels of snowfall than neighbouring cities. This study investigates the snow-shadow effect of Sado Island on snowfall in Niigata City, located 45 km away leeward. Statistical analysis of long-term radar data for 10 winters showed that snow-shadow effects in the Niigata plain occurred in 151 (80%) of the 188 cases, during which a strong approaching wind reached the island. The location of this snow-shadow effect was always downwind of Sado Island and depended on the wind direction. Numerical experiments using the Weather Research and Forecasting model predicted that snowfall over the Niigata Plain would be lighter with the island than without it. Additionally, the snow-shadow effect occurs in areas more than 150 km downwind. The experiments showed that Sado Island reduces heat fluxes from the sea surface by weakening leeward winds. At the same time, the horizontal wind convergence downwind is weakened. Meanwhile, the orographic snowfall over Sado Island reduces the amount of water vapour, cloud water and cloud ice over the leeward sea. Therefore, Sado Island prevents cloud lines from redeveloping over the leeward sea and can further reduce snowfall over the leeward plain, including in Niigata City.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"24 11","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43732557","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Future of land surface water availability over the Mediterranean basin and North Africa: Analysis and synthesis from the CMIP6 exercise","authors":"Khadija Arjdal,&nbsp;Fatima Driouech,&nbsp;Étienne Vignon,&nbsp;Frédérique Chéruy,&nbsp;Rodrigo Manzanas,&nbsp;Philippe Drobinski,&nbsp;Abdelghani Chehbouni,&nbsp;Abderrahmane Idelkadi","doi":"10.1002/asl.1180","DOIUrl":"10.1002/asl.1180","url":null,"abstract":"<p>The Mediterranean basin and Northern Africa are projected to be among the most vulnerable areas to climate change. This research documents, analyzes, and synthesizes the projected changes in precipitation P, evapotranspiration E, net water supply from the atmosphere to the surface P–E, and surface soil moisture over these regions as simulated by 17 global climate models from the sixth exercise of the Coupled Model Intercomparison Project (CMIP6) under two Shared Socioeconomic Pathways, SSP2-4.5, and SSP5-8.5. It also explores the sensitivity of the results to the chosen climate scenario and model resolution and assesses how the projections have evolved from the fifth exercise (CMIP5). Models project a statistically robust drying over the entire Mediterranean and coastal North Africa. Over the Northern Mediterranean sector, a significant precipitation decrease reaching −0.4 ∓ 0.1 mm <math>\u0000 <mrow>\u0000 <msup>\u0000 <mi>day</mi>\u0000 <mrow>\u0000 <mo>−</mo>\u0000 <mn>1</mn>\u0000 </mrow>\u0000 </msup>\u0000 </mrow></math> is projected during the 21st century under the SSP5-8.5 scenario. Conversely, a significant increase in precipitation of +0.05 to 0.3 ∓ 0.1 mm day⁻¹ is projected over South-Eastern Sahara under the same scenario. Evapotranspiration and soil moisture exhibit decreasing trends over the Mediterranean basin and an increase over the Sahara for both SSPs, with a notable acceleration from the 2020s. As a result, P-E is projected to decrease at a rate of about −0.3 mm day⁻¹ under the high-end scenario SSP5-8.5 over the Mediterranean whilst no significant changes are expected over the Sahara due to evapotranspiration compensation effects. CMIP6 and CMIP5 models project qualitatively similar patterns of changes but CMIP6 models exhibit more intense changes over the Mediterranean basin and South-Eastern Sahara, especially during winter.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"24 11","pages":""},"PeriodicalIF":3.0,"publicationDate":"2023-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45742960","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}