Atmospheric Science Letters最新文献

{"title":"Interagency discrepancies in tropical cyclone intensity estimates over the western North Pacific in recent years","authors":"Lina Bai,&nbsp;Yinglong Xu,&nbsp;Jie Tang,&nbsp;Rong Guo","doi":"10.1002/asl.1132","DOIUrl":"10.1002/asl.1132","url":null,"abstract":"<p>This study investigates interagency discrepancies among best-track estimates of tropical cyclone (TC) intensity in the western North Pacific, provided by the Joint Typhoon Warning Center (JTWC), the China Meteorological Administration (CMA), and the Regional Specialized Meteorological Center (RSMC) Tokyo during 2013 to 2019. The results reveal evident differences in maximum wind speed (MSW) estimates, where linear systematic differences are significant. However, the Dvorak parameter (CI) numbers derived from the MSWs reported by the three agencies are internally consistent. Further analysis suggests that the remained CI discrepancies are related to differences in the estimation of intensity trends, initial intensities, and TC positions among these datasets. In addition, the CI estimates provided by the JTWC for TCs over the open ocean are generally higher than those reported by the CMA and RSMC. However, the estimates from CMA and RSMC tend to give higher TC intensities for the TCs in the mainland and coastal areas of China and Japan, respectively, than those over the open ocean with the same intensity in JTWC dataset. This pattern potentially reflects the extensive use of surface observations by these two agencies for landfalling and offshore TCs. These results may help the research community to get more accurate details about the TCs in WNP from the best track datasets of different agencies.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"24 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2022-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1132","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41521701","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":"Primary characteristics of the extreme heavy rainfall event over Henan in July 2021","authors":"Jianhua Sun,&nbsp;Shenming Fu,&nbsp;Huijie Wang,&nbsp;Yuanchun Zhang,&nbsp;Yun Chen,&nbsp;Aifang Su,&nbsp;Yaqiang Wang,&nbsp;Huan Tang,&nbsp;Ruoyun Ma","doi":"10.1002/asl.1131","DOIUrl":"10.1002/asl.1131","url":null,"abstract":"<p>During mid-July 2021, an extreme heavy rainfall event (HRE) occurred in Henan Province (hereafter “21.7” HRE), with extreme hourly precipitation of 201.9 mm appearing at Zhengzhou station. Our preliminary analyses of the “21.7” HRE using the observations and ECMWF (European Centre for Medium-Range Weather Forecasts) ERA5 reanalysis data, reached the following conclusions. Favorable configurations of various synoptic weather systems (e.g., strong upper-level high-pressure ridge, intense middle-level low-pressure trough) acted as crucial background conditions for the occurrence of the “21.7” HRE. A 21-h long-lived mesoscale convective vortex (MCV), mainly located in the middle and lower troposphere west of Zhengzhou city, was a key system that produced the extreme hourly rainfall of 201.9 mm·h⁻¹. The MCV's development/sustainment was dominated by the vertical transport of cyclonic vorticity and tilting, as well as the horizontal import of cyclonic vorticity to the vortex's key region. In contrast, the divergence-related vertical shrinking was the most detrimental factor. Lagrangian moisture transport analysis showed that moisture for the extreme heavy rainfall in Zhengzhou on July 20 mainly came from levels below 2200 m, driven by airflows on the peripheries of tropical cyclones IN-FA and CEMPAKA. To enhance the understanding of “21.7” HRE, we suggest more in-depth investigations in the future.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"24 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2022-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1131","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43559635","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":"Upper-level midlatitude troughs in boreal winter have an amplified low-latitude linkage over Africa","authors":"Neil Ward,&nbsp;Andreas H. Fink,&nbsp;Richard J. Keane,&nbsp;Douglas J. Parker","doi":"10.1002/asl.1129","DOIUrl":"10.1002/asl.1129","url":null,"abstract":"<p>In boreal winter, strong upper-level midlatitude troughs across the Atlantic–Africa–southwestern Asia sector generate substantial tropical–extratropical interaction and have become recognized as important factors in some extreme weather events. As such, they represent important dynamic features to understand and capture in weather forecasts, as well as in climate models for projections on longer timescales. Here, we empirically study the 20% of winter days with strongest trough signatures during 1982–2020 at each longitude across the sector, and show that the trough impact over northern Africa, most notably in central parts, is particularly strong in magnitude, low-latitude extent and persistence, leading to the characterization of a northern Africa mode of several-days weather fluctuation. Weather conditions that follow strong troughs from the eastern Atlantic to the Central Mediterranean include: (i) a warming tendency across much of northern Africa, generally of several Celsius magnitude ahead of the trough, and &gt;1°C even extending to the south of 10° N in central parts and continuing eastward until the Ethiopian Highlands; (ii) precipitation development further north than normal across northern tropical Africa, especially strong over longitudes corresponding to a northward extension of the main Congo rain belt. The intertropical discontinuity and low-level heat low are also shifted significantly north, with the complex of anomalies persisting for several days, beyond the timescale of the trough. For context, at all other trough longitudes across the sector, a warming signal does emerge (statistically significant), but with much shorter persistence (2–3 days), smaller magnitude and extending southward clearly only to 15–20° N. Mid-level tropical plumes of moisture are also typically present for strong troughs from the eastern Atlantic to southwestern Asia, and these alone can lead to weather extremes. However, low-level warming and mid-level moistening are uniquely juxtaposed at low latitudes over central Africa, where a near-equatorial signature develops.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"24 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2022-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1129","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45640343","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":"Progress, challenges, and future steps in data assimilation for convection-permitting numerical weather prediction: Report on the virtual meeting held on 10 and 12 November 2021","authors":"Guannan Hu,&nbsp;Sarah L. Dance,&nbsp;Ross N. Bannister,&nbsp;Hristo G. Chipilski,&nbsp;Oliver Guillet,&nbsp;Bruce Macpherson,&nbsp;Martin Weissmann,&nbsp;Nusrat Yussouf","doi":"10.1002/asl.1130","DOIUrl":"10.1002/asl.1130","url":null,"abstract":"<p>In November 2021, the Royal Meteorological Society Data Assimilation (DA) Special Interest Group and the University of Reading hosted a virtual meeting on the topic of DA for convection-permitting numerical weather prediction. The goal of the meeting was to discuss recent developments and review the challenges including methodological developments and progress in making the best use of observations. The meeting took place over two half days on the 10 and 12 November, and consisted of six talks and a panel discussion. The scientific presentations highlighted some recent work from Europe and the USA on convection-permitting DA including novel developments in the assimilation of observations such as cloud-affected satellite radiances in visible channels, ground-based profiling networks, aircraft data, and radar reflectivity data, as well as methodological advancements in background and observation error covariance modelling and progress in operational systems. The panel discussion focused on key future challenges including the handling of multiscales (synoptic-, meso-, and convective-scales), ensemble design, the specification of background and observation error covariances, and better use of observations. These will be critical issues to address in order to improve short-range forecasts and nowcasts of hazardous weather.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"24 1","pages":""},"PeriodicalIF":3.0,"publicationDate":"2022-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1130","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44957857","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":"Distinct response of near surface air temperature to clouds in North China","authors":"Shuyi Jiang,&nbsp;Chuanfeng Zhao,&nbsp;Yan Xia","doi":"10.1002/asl.1128","DOIUrl":"10.1002/asl.1128","url":null,"abstract":"<p>Using the daily 2 m maximum temperature (Tmax), 2 m minimum temperature (Tmin) and cloud cover data measured at ground sites of the China Meteorological Administration in North China from 2000 to 2017, this study investigates the influence of clouds on the daily temperature range (DTR) defined as the difference between Tmax and Tmin. As expected, the cloud cover shows the similar averaged spatial distribution and monthly variation with Tmin. Surprisingly, it also shows the similar average spatial distribution and monthly variation with Tmax, suggesting the more important roles of regions (latitude) and seasons associated with the variations of land surface temperature, which is further related to solar radiation absorbed and surface heat capacity. By comparing monthly variations of temperature between cloudy and clear skies, we find that clouds can weaken Tmax and increase Tmin, and thus decrease DTR. As a result, the spatial distribution of DTR is opposite to the cloud cover. The clouds have relatively stronger impact on Tmin and DTR over mountain region, which is most likely caused by the stronger longwave cloud radiative forcing associated with higher cloud tops over the mountain region.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"23 12","pages":""},"PeriodicalIF":3.0,"publicationDate":"2022-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1128","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51635894","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 European winter 2020/2021: Influence of a mid-winter sudden stratospheric warming","authors":"Julia F. Lockwood,&nbsp;Nicky Stringer,&nbsp;Hazel E. Thornton,&nbsp;Adam A. Scaife,&nbsp;Philip E. Bett,&nbsp;Tamara Collier,&nbsp;Ruth Comer,&nbsp;Nick Dunstone,&nbsp;Margaret Gordon,&nbsp;Leon Hermanson,&nbsp;Sarah Ineson,&nbsp;Jamie Kettleborough,&nbsp;Jeff Knight,&nbsp;Joseph Mancell,&nbsp;Peter McLean,&nbsp;Doug Smith,&nbsp;Tony Wardle,&nbsp;Prince Xavier,&nbsp;Ben Youngman","doi":"10.1002/asl.1126","DOIUrl":"10.1002/asl.1126","url":null,"abstract":"<p>Boreal winter (December–February) 2020/2021 in the North Atlantic/European region was characterised by a negative North Atlantic Oscillation (NAO) index. Although this was captured within the ensemble spread of predictions from the Met Office Global Seasonal forecast system (GloSea5), with 17% of ensemble members predicting an NAO less than zero, the forecast ensemble mean was shifted towards a positive NAO phase. The observed monthly NAO anomalies were particularly negative in January and February, following an early January sudden stratospheric warming (SSW), and a prolonged period of Phase 6 or 7 of the Madden Julian Oscillation (MJO) in late January/early February. In contrast, predictions showed the expected teleconnection from the observed La Niña, with a positive NAO signal resulting from a weakening of the Aleutian Low leading to a reduction in tropospheric wave activity, an increase in polar vortex strength and a reduced chance of an SSW. Forecasts initialised later in the winter season successfully predicted the negative NAO in January and February once the SSW and MJO were within the medium range timescale. GloSea5 likely over-predicted the strength of the La Niña which we estimate caused a small negative bias in the SSW probability. However, this error is smaller than the uncertainty in SSW probability from the finite forecast ensemble size, emphasising the need for large forecast ensembles. This case study also demonstrates the advantage of continuously updated lagged ensemble forecasts over a ‘burst’ ensemble started on a fixed date, since a change in forecast signal due to events within the season can be detected early and promptly communicated to users.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"23 12","pages":""},"PeriodicalIF":3.0,"publicationDate":"2022-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1126","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48297222","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":"Error investigation of rain retrievals from disdrometer data using triple colocation","authors":"Clizia Annella,&nbsp;Vincenzo Capozzi,&nbsp;Giannetta Fusco,&nbsp;Giorgio Budillon,&nbsp;Mario Montopoli","doi":"10.1002/asl.1127","DOIUrl":"10.1002/asl.1127","url":null,"abstract":"<p>Assessing the uncertainty of precipitation measurements is a challenging problem because precipitation estimates are inevitably influenced by various errors and environmental conditions. A way to characterize the error structure of coincident measurements is to use the triple colocation (TC) statistical method. Unlike more typical approaches, where measures are compared in pairs and one of the two is assumed error-free, TC has the enviable advantage to succeed in characterizing the uncertainties of co-located measurements being compared to each other, without requiring the knowledge of the true value which is often unknown. However, TC requires to have at least three co-located measuring systems and the compliance with several initial assumptions. In this work, for the first time, TC is applied to in-situ measurements of rain precipitation acquired by three co-located devices: a weighing rain gauge, a laser disdrometer and a bidimensional video disdrometer. Both parametric and nonparametric formulations of TC are implemented to derive the rainfall product precision associated with the three devices. While the parametric TC technique requires tighter constraints and explicit assumptions which may be violated causing some artifacts, the nonparametric formulation is more flexible and requires less strict constrains. For this reason, a comparison between the two TC formulations is also presented to investigate the impact of TC constrains and their possible violations. The results are obtained using a statistically robust dataset spanning a 1.5 year period collected in Switzerland and presented in terms of traditional metrics. According to triple colocation analysis, the two disdrometers outperform the classical weighing rain gauge and they have similar measurement error structure regardless of the integration time intervals.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"23 12","pages":""},"PeriodicalIF":3.0,"publicationDate":"2022-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1127","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49307093","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":"Recent decrease in inner-core rain rate of tropical cyclones over the western North Pacific","authors":"Na Wei,&nbsp;Jinjie Song,&nbsp;Yifei Dai,&nbsp;Sulin Jiang,&nbsp;Yihong Duan","doi":"10.1002/asl.1125","DOIUrl":"10.1002/asl.1125","url":null,"abstract":"<p>The tendency in tropical cyclone (TC) rainfall is of great concern due to its remarkable contribution to global precipitation and extreme rainfall events. This study finds a decreasing trend in TC inner-core rain rate over the western North Pacific (WNP) from 1998 to 2019. This basinwide trend is mainly induced by the decreasing TC inner-core rain rates over the region west of 150°E, while it is seldom linked to the changes in the distribution of TC occurrence. The maximum decreases in TC inner-core rain rate are observed over the offshore areas along the coastlines of East Asia. Further analysis reveals that the change in atmospheric stability, referred to as a dominant environmental contributor to basinwide TC inner-core rain rate decreases shown in previous studies, only has a primary impact over the northern South China Sea. By comparison, there is a positive correlation between the variations of the aerosol optical depth and TC inner-core rain rate over the mid-latitude regions extending from the East China Sea to Japan. Our result highlights the linkage of the recent decreasing trends in aerosol optical depth and TC inner-core rain rate over the WNP.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"23 12","pages":""},"PeriodicalIF":3.0,"publicationDate":"2022-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1125","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47444036","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":"How Asian slum emissions impact local microclimates in polluted air masses","authors":"Satyajit Ghosh,&nbsp;C. R. Sathish Kumar,&nbsp;Siddharth Gumber,&nbsp;Steven Dobbie,&nbsp;Huiyi Yang","doi":"10.1002/asl.1124","DOIUrl":"10.1002/asl.1124","url":null,"abstract":"Urban sprawl comprising densely populated slums over South Asian cities yields copious amounts of soot and black carbon from archaic cooking methods involving cow dung cakes and firewood, which remain afloat for over 10–12 h, enabling them to age in a sulphur rich environment. Not only are there toxicological concerns arising out of improper ventilation mechanisms, but there are also other concerns impacting the local microclimate. These emissions mix with other aerosol particles and, when conditions are favourable, are rendered partially soluble, enabling them to activate into cloud condensation nuclei. This study first yields a quantification of the soluble mass fraction and subsequently shows how aerosols from this local area source mix with background aerosol modes to perturb the local cloud microphysics over Chennai, a megacity in Southern India. On‐site sampling was undertaken to find the mass concentrations of the collected deposits separately from cow dung and firewood fuel. Additional micro‐physical attributes, including the morphological indentations that served as a receptacle to contain the accreted sulphate along with the particle size distribution were ascertained through Scanning Electron Microscopy. It is shown that accreted sulphate on carbonaceous particles facilitates CCN activation over the city. We show through large‐eddy simulations (LES) that extensive slum emissions over the study region contribute to the observed local cloud cover and enhanced rain amounts over a densely built‐up area housing the city's most vulnerable citizens.","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"23 12","pages":""},"PeriodicalIF":3.0,"publicationDate":"2022-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1124","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42868596","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":"Recent decrease in western North Pacific tropical cyclone rapid intensification during June","authors":"Jinjie Song,&nbsp;Philip J. Klotzbach,&nbsp;Sulin Jiang,&nbsp;Yihong Duan","doi":"10.1002/asl.1121","DOIUrl":"10.1002/asl.1121","url":null,"abstract":"<p>This study investigates the long-term tendency in the ratio of rapid intensification (RI) cases to the total number of tropical cyclone cases over the western North Pacific (WNP) during June between 1982 and 2021. There is a significant decreasing trend in RI ratio during June, which is opposite to the increasing trend in RI ratio during July–November. From 1982–2005 to 2006–2021, the June RI ratio significantly decreases over the region of 5°–20°N and 120°–150°N, while showing weak changes over other parts of the WNP. Over the region with a significant RI ratio reduction, significantly reduced 850-hPa relative vorticity and 200-hPa divergence and significantly enhanced 850 to 200-hPa vertical wind shear are the likely primary drivers. The RI-suppressing effect of the above changes in dynamical variables exceeds the RI-favoring effect of the warming ocean, for example, significantly increased sea surface temperature and tropical cyclone heat potential, over this same region. Moreover, the changes in dynamic conditions can be related to an anomalous low-level anticyclonic circulation, anomalous upper-level convergent flow and a greater enhancement of upper-level easterlies than lower-level easterlies. Our study highlights the importance of changes in dynamic variables (e.g., vertical wind shear) in modulating WNP RI activity.</p>","PeriodicalId":50734,"journal":{"name":"Atmospheric Science Letters","volume":"23 11","pages":""},"PeriodicalIF":3.0,"publicationDate":"2022-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/asl.1121","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43523909","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}