Atmospheric Science Letters最新文献

{"title":"Change detection of the Köppen climate zones in Southeastern Europe","authors":"Gordan Mimić,&nbsp;Zorica Podraščanin,&nbsp;Biljana Basarin","doi":"10.1002/asl.1270","DOIUrl":"https://doi.org/10.1002/asl.1270","url":null,"abstract":"<p>The study exploits the air temperature and precipitation data from ERA5-Land reanalysis and E-OBS gridded observations that are freely available from the Copernicus Climate Change Service. The objectives of the study are to analyze the distribution of Köppen climate zones and to detect the changes in the presence and coverage of the specific climate types in Southeastern Europe. The results are shown separately for the following reference periods: 1961–1990, 1971–2000, 1981–2010, and 1991–2020. In the period 1961–1990, the most dominant climate type in Southeastern Europe was fully humid temperate climate with warm summer (Cfb), while fully humid continental climate with warm summer (Dfb) was also highly present there, together with fully humid temperate climate with hot summer (Cfa). In the period 1991–2020, the shift of Köppen climate zones appeared in such a way that the area with Dfb continental climate, that is often called snow or cold climate, is significantly reduced and this type is replaced with Cfb temperate climate. At the same time, Cfa climate type with hot summer is spread across wider area, mainly instead of Cfb with warm summer, now reaching almost the same percentage of coverage as Cfb type.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"25 11","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1270","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142579573","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":"Are convection-permitting climate projections reliable for urban planning over Africa? A case study of Johannesburg","authors":"William J. Keat,&nbsp;Chris J. Short,&nbsp;Elizabeth J. Kendon","doi":"10.1002/asl.1264","DOIUrl":"https://doi.org/10.1002/asl.1264","url":null,"abstract":"<p>Cities are particularly vulnerable to surface water flooding. It is also well-known that they influence local rainfall themselves, which has important implications for climate change adaptation planning for cities. At km-scale resolution, convection-permitting climate models (CPCMs) better resolve cities and should better represent local urban temperature and rainfall modifications. However, using state-of-the-art pan-African CPCM simulations with the Met Office Unified Model (CP4), we show that for the city of Johannesburg, South Africa, this is not the case. A significant enhancement of rainfall occurs over the city compared with surrounding rural areas, which is not seen in available observations. We demonstrate this is associated with an overestimated urban heat island effect, which leads to additional triggering of rainfall. Urban signals in future rainfall change are small compared with changes in the wider surroundings, the latter of which we expect to be more reliable than in models with parameterized convection. This suggests that deficiencies in representation of urban processes are of secondary importance in terms of future percentage change in rainfall. We recommend urban planners apply relative changes in CP4 as an uplift to observations, where available, or treat absolute future rainfall as an upper estimate if used directly.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"25 11","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1264","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142579679","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 asymmetry of surface albedo in a semi-arid grassland over the China's Loess Plateau","authors":"Di Zhu,&nbsp;Jianrong Bi,&nbsp;Xiting Wang,&nbsp;Zhaozhao Meng,&nbsp;Jinsen Shi,&nbsp;Oufan Li","doi":"10.1002/asl.1271","DOIUrl":"https://doi.org/10.1002/asl.1271","url":null,"abstract":"<p>In current land surface models or satellite remote sensing retrievals, clear-sky surface albedo (<i>α</i>) is usually assumed to be symmetrical and relies only on the solar elevation angle (SEA). Based on 1-min high-resolution measurements of surface radiation fluxes, this study demonstrated that the diurnal variations of clear-sky surface albedo exhibited a significant asymmetrical pattern in both summer and winter seasons over a semi-arid grassland of the China's Loess Plateau. The results indicated that <i>α</i> values in the morning were generally larger than those in the afternoon at the same SEA, and diurnal asymmetry of surface albedo was distinctly prominent with SEA &lt;40° in summer (before 9:30 a.m.) or SEA &lt;20° in winter (before 10:00 am), and tended to diminish at midday. The averaged morning/afternoon albedo differences under sunny days were 0.05 (30.4%) and 0.09 (37.8%) in summer and winter seasons, respectively. Air relative humidity was positively correlated with the diurnal asymmetry of surface albedo, ascribed to probable formation of dew in the morning. Depression of the dew point was negatively linked to the morning/afternoon albedo differences, which was attributed to the strong scattering of incident sunlight by dewdrops could enhance the morning surface albedo. Such diurnal asymmetry of surface albedo should be included in the parameterization scheme of mesoscale and region-scale climate models in the semi-arid areas of China's Loess Plateau.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"25 11","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1271","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142579604","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":"Quantitative study on the water vapor transport characteristics of an extreme precipitation event in North China","authors":"Xiaofan Li,&nbsp;Yufei Chang,&nbsp;Changwen Yu,&nbsp;Zhiqiang Gong,&nbsp;Yunhao Li,&nbsp;Zhongjie Zhang,&nbsp;Shaojing Che","doi":"10.1002/asl.1269","DOIUrl":"https://doi.org/10.1002/asl.1269","url":null,"abstract":"<p>North China experienced an extreme precipitation event from July 29 to August 1, 2023 (i.e., the “23.7” event) causing severe floods, significant infrastructure damage and multiple fatalities. To enhance comprehension of the mechanism behind the extreme precipitation of the “23.7” event, water vapor transport paths and sources were determined, and water vapor contribution of each source was quantitatively evaluated based on Lagrangian methods. Results showed that the extreme precipitation of the “23.7” event was closely related to large-scale water vapor transport and convergence from low-latitude oceans. There were five main water vapor sources which corresponded to five transport pathways. Path 1 was derived from tropical West Pacific, containing the most trajectories (195), carrying the most water vapor (69.3%) and contributing the most to the extreme precipitation of the “23.7” event (45.7%). Path 2 was guided by the cross-equatorial flow through South China Sea, contributing to 10.1% of the precipitation. Path 3 originating from eastern tropical Indian Ocean and Path 4 from the west source near the Caspian Sea contributed less to the precipitation. Last but not the least, water vapor evaporation from eastern China contributed more than 30% to the extreme precipitation, making this region another important water vapor source.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"25 11","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1269","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142579791","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":"A shifting climate: New paradigms and challenges for (early career) scientists in extreme weather research","authors":"Marlene Kretschmer,&nbsp;Aglaé Jézéquel,&nbsp;Zachary M. Labe,&nbsp;Danielle Touma","doi":"10.1002/asl.1268","DOIUrl":"https://doi.org/10.1002/asl.1268","url":null,"abstract":"<p>Research on weather and climate extremes has become integral to climate science due to their increasing societal relevance and impacts in the context of anthropogenic climate change. In this perspective we examine recent changes and evolving paradigms in the study of extreme events, emphasizing the increasingly interdisciplinary nature of research and their societal implications. We discuss the importance of understanding the physical basis of extreme events and its linkages to climate impacts, highlighting the need for collaboration across multiple disciplines. Furthermore, we explore the challenge of big climate data analysis and the application of novel statistical methods, such as machine learning, in enhancing our understanding of extreme events. Additionally, we address the engagement with different stakeholder groups and the evolving landscape of climate services and private-sector involvement. We conclude with reflections on the risks and opportunities for early career researchers in navigating these interdisciplinary and societal demands, stressing the importance of meaningful scientific engagement, and removing barriers to inclusivity and collaboration in climate research.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"25 11","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1268","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142579647","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":"A simple subtropical high-pressure system index over the South Atlantic","authors":"Kwesi A. Quagraine,&nbsp;Bruce Hewitson,&nbsp;Francis Nkrumah,&nbsp;Kwesi T. Quagraine,&nbsp;Temitope S. Egbebiyi","doi":"10.1002/asl.1266","DOIUrl":"10.1002/asl.1266","url":null,"abstract":"<p>This research introduces a novel index for the South Atlantic High Pressure (SAHP) system to enhance understanding of regional climate variability and change. Subtropical highs significantly influence regional climates, yet comprehensive indices to measure their behaviours are lacking. Utilizing ERA5 reanalysis data from 1940 to 2023, the proposed index estimates a weighted centroid of the area surrounding the maximum sea level pressure within a 3 hPa range. This method ensures robustness and flexibility in contiguous area estimation specific to subtropical high events. Results showed the index effectively reflects the position and intensity of the SAHP. The study reveals that latitudinal variability of the SAHP has a strong unimodal structure, whereas longitudinal variability exhibits a bimodal structure. Seasonal patterns of the index show noticeable changes, with winter (JJA) and spring (SON) months having relatively high index values compared to summer (DJF) and autumn (MAM) months, underscoring the intra-annual variability of the SAHP index. During ENSO events, the mean centroid position of the SAHP shifts significantly, moving westwards and polewards during El Niño and showing greater stability during La Niña. The index, with minimal computation requirements and flexibility, can be applied across diverse datasets, aiding in the assessment of future subtropical high changes.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"25 11","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1266","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142191273","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":"Towards replacing precipitation ensemble predictions systems using machine learning","authors":"Rüdiger Brecht,&nbsp;Alex Bihlo","doi":"10.1002/asl.1262","DOIUrl":"10.1002/asl.1262","url":null,"abstract":"<p>Forecasting precipitation accurately poses significant challenges due to various factors affecting its distribution and intensity, including but not limited to subgrid variability. Although higher resolution simulations are often considered to improve precipitation forecasts, it is crucial to note that simply increasing resolution may not suffice without appropriate adjustments to parameterization schemes or tuning. Traditionally, ensembles of simulations are used to generate uncertainty predictions associated with precipitation forecasts, but this approach can be computationally intensive. As an alternative, there is a growing trend towards leveraging neural networks for precipitation prediction, which offers potential computational advantages. We propose a new approach to generating ensemble weather predictions for high-resolution precipitation without requiring high-resolution training data. The method uses generative adversarial networks to learn the complex patterns of precipitation and produce diverse and realistic precipitation fields, allowing to generate realistic precipitation ensemble members using only the available control forecast. We demonstrate the feasibility of generating realistic precipitation ensemble members on unseen higher resolutions. We use evaluation metrics such as RMSE, CRPS, rank histogram and ROC curves to demonstrate that our generated ensemble is almost identical to the ECMWF IFS ensemble, on which our model was trained on.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"25 11","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1262","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142191279","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":"Accuracy of daily extreme air temperatures under natural variations in thermometer screen ventilation","authors":"R. Giles Harrison,&nbsp;Stephen D. Burt","doi":"10.1002/asl.1256","DOIUrl":"10.1002/asl.1256","url":null,"abstract":"<p>Accurate air temperatures underpin environmental research. Most professional meteorological air temperature measurements still expose thermometers within traditional, naturally ventilated screens. Their representation of true air temperature depends on screen airflow, and therefore local winds. Accuracies of daily maximum (<i>T</i>_max) and minimum (<i>T</i>_min) air temperatures are assessed by comparison between a naturally ventilated large conventional screen and a co-located aspirated reference screen. In over 1200 days' data, the naturally ventilated <i>T</i>_min and <i>T</i>_max both showed small (median &lt; 0.06°C) cold bias, but, in 1% of cases, warm <i>T</i>_max bias and cold <i>T</i>_min bias &gt;|1°C|. The <i>T</i>_min cold bias is associated with calm clear nights, and the <i>T</i>_max warm bias events with calm winter days at low sun angles, allowing solar heating of the screen. The prevalence of poor natural ventilation, potentially affecting <i>T</i>_min and <i>T</i>_max, is estimated across European sites. Poor ventilation occurred at <i>T</i>_min for 12% of values, and at <i>T</i>_max for 4%. Climatological averaging will reduce these effects, but, without corroborating wind data, statistical changes in <i>T</i>_min or <i>T</i>_max, including identifying “Tropical Nights” (<i>T</i>_min &gt; 20°C) or occurrences of winter extremes, may have limited value. Wider adoption of aspirated thermometer screens, with an initial overlap period, will largely eliminate these effects.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"25 10","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1256","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142191274","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":"Changing dynamics of Western European summertime cut-off lows: A case study of the July 2021 flood event","authors":"Vikki Thompson,&nbsp;Dim Coumou,&nbsp;Vera Melinda Galfi,&nbsp;Tamara Happé,&nbsp;Sarah Kew,&nbsp;Izidine Pinto,&nbsp;Sjoukje Philip,&nbsp;Hylke de Vries,&nbsp;Karin van der Wiel","doi":"10.1002/asl.1260","DOIUrl":"10.1002/asl.1260","url":null,"abstract":"<p>In July 2021, a cut-off low-pressure system brought extreme precipitation to Western Europe. Record daily rainfall totals led to flooding that caused loss of life and substantial damage to infrastructure. Climate change can amplify rainfall extremes via thermodynamic processes, but the role of dynamical changes is uncertain. We assess how the dynamics involved in this particular event are changing using flow analogues. Using past and present periods in reanalyses and large ensemble climate model data of the present-day climate and 2°C warmer climate, we find that the best flow analogues become more similar to the cut-off low-pressure system observed over Western Europe in 2021. This may imply that extreme rain events will occur more frequently in the future. Moreover, the magnitude of the analogue lows has deepened, and the associated air masses contain more precipitable water. Simulations of future climate show similar events of the future could lead to intense rainfall further east than in the current climate, due to a shift of the pattern. Such unprecedented events can have large consequences for society, we need to mitigate and adapt to reduce future impacts.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"25 10","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1260","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142191275","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 effect of vertical temperature gradient on the equivalent depth in thin atmospheric layers","authors":"Yair De-Leon,&nbsp;Chaim I. Garfinkel,&nbsp;Nathan Paldor","doi":"10.1002/asl.1259","DOIUrl":"10.1002/asl.1259","url":null,"abstract":"<p>The equivalent depth of an atmospheric layer is of importance in determining the phase speed of gravity waves and characterizing wave phenomena. The value of the equivalent depth can be obtained from the eigenvalues of the vertical structure equation (the vertical part of the primitive equations) where the mean temperature profile is a coefficient. Both numerical solutions of the vertical structure equation and analytical considerations are employed to calculate the equivalent depth, <span></span><math>\u0000 <mrow>\u0000 <msub>\u0000 <mi>h</mi>\u0000 <mi>n</mi>\u0000 </msub>\u0000 </mrow></math>, as a function of the atmospheric layer's thickness, <span></span><math>\u0000 <mrow>\u0000 <mi>Δ</mi>\u0000 <mi>z</mi>\u0000 </mrow></math>. Our solutions for layers of thickness 100 <span></span><math>\u0000 <mrow>\u0000 <mo>≤</mo>\u0000 <mi>Δ</mi>\u0000 <mi>z</mi>\u0000 <mo>≤</mo>\u0000 </mrow></math> 2000 m show that for baroclinic modes, <span></span><math>\u0000 <mrow>\u0000 <msub>\u0000 <mi>h</mi>\u0000 <mi>n</mi>\u0000 </msub>\u0000 </mrow></math> can be over two orders of magnitudes smaller than <span></span><math>\u0000 <mrow>\u0000 <mi>Δ</mi>\u0000 <mi>z</mi>\u0000 </mrow></math>. Analytic expressions are derived for <span></span><math>\u0000 <mrow>\u0000 <msub>\u0000 <mi>h</mi>\u0000 <mi>n</mi>\u0000 </msub>\u0000 </mrow></math> in layers of uniform temperature and numerical solutions are derived for layers in which the temperature changes linearly with height. A comparison between the two cases shows that a slight temperature gradient (of say 0.65 K across a 100 m layer) decreases <span></span><math>\u0000 <mrow>\u0000 <msub>\u0000 <mi>h</mi>\u0000 <mi>n</mi>\u0000 </msub>\u0000 </mrow></math> by a factor of 3 (but can reach a factor of 10 for larger gradients) compared with its value in a layer of uniform temperature, while a change of 10 K in the layer's uniform temperature hardly changes <span></span><math>\u0000 <mrow>\u0000 <msub>\u0000 <mi>h</mi>\u0000 <mi>n</mi>\u0000 </msub>\u0000 </mrow></math>. The <span></span><math>\u0000 <mrow>\u0000 <mi>n</mi>\u0000 <mo>=</mo>\u0000 <mn>0</mn>\u0000 </mrow></math> baroclinic mode exists in all combinations of boundary conditions top and bottom while the barotropic mode only exists when the vertical velocity vanishes at both boundaries of the layer.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"25 10","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1259","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142191276","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}