Monthly Weather Review最新文献

{"title":"Radar-derived Convective Features and Atmospheric Environments of Hail-Producing Storms over the Contiguous United States","authors":"Edward R. Vasquez, Chuntao Liu","doi":"10.1175/mwr-d-23-0151.1","DOIUrl":"https://doi.org/10.1175/mwr-d-23-0151.1","url":null,"abstract":"\u0000Hail smaller than 0.75 inch is known to cause economic impacts yet remains understudied due to report biases towards recording larger hail sizes (≤1 inch). In this study, we assembled ground hail reports during 2017-2022 from the National Centers for Environmental Information (NCEI) Storm Data, Community Collaborative Rain, Hail and Snow Network (CoCoRaHS) and Meteorological Phenomena Identification Near the Ground (mPING) databases. Then these reports are collocated with the attributes of radar-derived convective features from the Multi-Radar/Multi-sensor System (MRMS) and the European Centre for Medium-Range Weather Forecasts Reanalysis v5 (ERA5) atmospheric vertical profiles to construct a dataset describing properties of a full spectrum of hailstorms. The characteristics of radar reflectivity and atmospheric profiles are examined for hail of different sizes reported within selected regions over the Contiguous United States (CONUS). In addition to the seasonal and diurnal variations, the morphology of convective features shows apparent regional differences from west to east in CONUS. The Maximum Expected Size of Hail (MESH) performance against reported hail sizes shows underestimation of hail with significant sizes, and overestimation of small hail sizes.\u0000ERA5 vertical atmospheric profiles are explored to form relationships between storm environment and hail sizes. In addition to the relationships between wind shear and hail sizes, the roles of low-level relative humidity and freezing level height in regard to hail melting are discussed.","PeriodicalId":18824,"journal":{"name":"Monthly Weather Review","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141927582","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":"An implementation of the particle flow filter in an atmospheric model","authors":"Chih‐Chi Hu, Peter Jan van Leeuwen, Jeffrey L. Anderson","doi":"10.1175/mwr-d-24-0006.1","DOIUrl":"https://doi.org/10.1175/mwr-d-24-0006.1","url":null,"abstract":"\u0000The particle flow filter (PFF) shows promise for fully nonlinear data assimilation (DA) in high dimensional systems. However, its application in atmospheric models has been relatively unexplored. In this study, we develop a new algorithm, PFF-DART, in order to conduct DA for high-dimensional atmospheric models. PFF-DART combines the PFF and the two-step ensemble filtering algorithm in the Data Assimilation Research Testbed (DART), exploiting the highly parallel structure of DART. To evaluate the performance of PFF-DART, we conduct an Observing System Simulation Experiment (OSSE) in a simplified atmospheric general circulation model, and compare the performance of PFF-DART with an existing linear and Gaussian DA method. Using the PFF-DART algorithm, we demonstrate, for the first time, the capability of the PFF to yield stable results in a year-long cycling DA OSSE. Moreover, PFF-DART retains the important ability of the PFF to improve the assimilation of nonlinear and non-Gaussian observations. Finally, we emphasize that PFF-DART is a versatile algorithm that can be integrated with numerous other non-Gaussian DA techniques. This quality makes it a promising method for further investigation within a more sophisticated numerical weather prediction model in the future.","PeriodicalId":18824,"journal":{"name":"Monthly Weather Review","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141829739","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":"Clustering Anomalous Circulations and Their Implications on the Prediction of Minimum 2m Air Temperature over Northeastern China during Winter","authors":"Yang Zhou, Binshuo Liu, Boyang Lei, Qifan Zhao, Shanlei Sun, Haishan Chen","doi":"10.1175/mwr-d-24-0014.1","DOIUrl":"https://doi.org/10.1175/mwr-d-24-0014.1","url":null,"abstract":"\u0000The ERA5 reanalysis during cold months (November-March) of 1979-2020 was used for determining four cluster centroids through the k-means for classifying regional anomalies of the daily geopotential height at 500 hPa (H500) over northeastern China. EOF was used to reduce dimensionality. Four clusters were linked to the EOF patterns with clear meteorological meanings, which are associated with the evolutions of ridge and trough over northeastern China. Those systems relate to warm and cold advections at 850 hPa. In each H500 cluster, the advection is the major contributor leading to temperature changes at 850 hPa, which significantly relates to the changes and anomalies of daily minimum air temperature at 2m (T2min). Furthermore, the jet activities over Asia relate to more or less occurrence of specific H500 clusters in jet phases. This is because anomalous westerlies are generally in favor of positive anomalies of vorticity tendency at 500 hPa. For the reforecasts during 2004-2019 in the CMA S2S model, the hit rates above 50% for all the H500 clusters are within 9.5 days, which are in between those for the first two and the last two clusters. The correct prediction of H500 anomalies improves the T2min prediction up to 12 days, compared with 8 days for the incorrect one. The good prediction of the jet activities leads to more accurate prediction of H500 anomalies. Therefore, improvement of the model prediction of the jet activities and the H500 anomalies will lead to better prediction of winter weather near the ground over northeastern China.","PeriodicalId":18824,"journal":{"name":"Monthly Weather Review","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141828114","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":"A priori test of scale-similarity parameterizations for subgrid-scale fluxes in convective storms","authors":"Shun-ich I. Watanabe, Junshi Ito","doi":"10.1175/mwr-d-24-0059.1","DOIUrl":"https://doi.org/10.1175/mwr-d-24-0059.1","url":null,"abstract":"\u0000This study evaluates a parameterization scheme for subgrid-scale (SGS) fluxes based on the scale-similarity assumption and employing a large-eddy simulation of an idealized backbuilding convective system. In this parameterization, the SGS fluxes are decomposed into the “Leonard term” which depends only on the resolved scale components, the “Reynolds term” which depends only on the SGS components, and the “cross term” which corresponds to the interaction between the resolved scale and SGS components. Assuming a linear relationship between the Leonard term and the Reynolds and cross terms, SGS fluxes are expressed as the product of an empirical coefficient and the Leonard term. The Leonard term reasonably represents the SGS flux derived by a smooth filter operation, including the counter-gradient vertical SGS transport of potential temperature, which cannot be represented by a traditional eddy-diffusivity model. The dependence of the empirical coefficient on filter width is also evaluated. This dependence is related mainly to the Reynolds term, the magnitude of which varies widely with filter width. The estimation based on the spectral decomposition of the Reynolds term explains the obtained dependence of the empirical coefficient for the vertical flux on filter width. In contrast, the variation of the empirical coefficient with filter width is not required to obtain the horizontal flux. For the parameterization of SGS fluxes in kilometer-scale models that use finite difference or volume methods, the Leonard term is expressed by the horizontal gradient of variables on a discrete grid. The Leonard term on a discrete grid also accurately represents the amplitude and spatial pattern of the SGS flux.","PeriodicalId":18824,"journal":{"name":"Monthly Weather Review","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141646217","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":"Examining Outer Band Supercell Environments in Landfalling Tropical Cyclones using Ground-Based Radar Analyses","authors":"A. A. Alford, Benjamin Schenkel, Samuel Hernandez, Jun A. Zhang, M. Biggerstaff, Emily Blumenauer, T. Sandmæl, S. Waugh","doi":"10.1175/mwr-d-23-0287.1","DOIUrl":"https://doi.org/10.1175/mwr-d-23-0287.1","url":null,"abstract":"\u0000Supercells in landfalling tropical cyclones (TCs) often produce tornadoes within 50 km of the coastline. The prevalence of TC tornadoes near the coast is not explained by the synoptic environments of the TC, suggesting a mesoscale influence is likely. Past case studies point to thermodynamic contrasts between ocean and land or convergence along the coast as a possible mechanism for enhancing supercell mesoscyclones and storm intensity. This study augments past work by examining the changes in the hurricane boundary layer over land in context of vertical wind shear. Using ground-based single- and dual-Doppler radar analyses, we show that the reduction of the boundary layer wind results in a increase in vertical wind shear/storm relative helicity inland of the coast. We also show that convergence along the coast may be impactful to supercells as they cross the coastal boundary. Finally, we briefly document the changes in mesocyclone vertical vorticity to assess how the environmental changes may impact individual supercells.","PeriodicalId":18824,"journal":{"name":"Monthly Weather Review","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141679890","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":"Modulation of U.S. tornado activity by year-round North American weather regimes","authors":"Michael K. Tippett, Kelsey Malloy, Simon H. Lee","doi":"10.1175/mwr-d-24-0016.1","DOIUrl":"https://doi.org/10.1175/mwr-d-24-0016.1","url":null,"abstract":"\u0000Here we examine the relation between U.S. tornado activity and a new year-round classification of North American weather regimes. The regime classification is based on 500-hPa geopotential height anomalies and classifies each day as Pacific Trough, Pacific Ridge, Alaskan Ridge, Greenland High, or No Regime. During the period 1979–2022, we find statistically significant relations between average tornado report numbers and weather regimes in all months except June–August. Tornado activity is enhanced on Pacific Ridge days during late winter and spring, reduced on Pacific Trough days in spring, and reduced on Alaskan Ridge and Greenland High days during fall and early winter. During active regimes, the probability of many tornadoes occurring also increases, and there is greater variability in the number of tornadoes reported each day. A reanalysis-based tornado index reproduces the regional features of the modulation of tornado activity by the weather regimes and attributes them to changes in storm relative helicity, convective available potential energy, and convective precipitation. The phase of the El Niño-Southern Oscillation (ENSO) also plays a role. In winter and spring, Pacific Ridge days occur more often and average more reports per day during cool ENSO conditions. During warm ENSO conditions, Pacific Trough days occur more often and are associated with widespread reduced tornado activity.","PeriodicalId":18824,"journal":{"name":"Monthly Weather Review","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141687103","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":"Track Deflection of Typhoon Chanthu (2021) near Taiwan as Investigated Using a High-Resolution Global Model","authors":"Ya-Shin Chi, Ching-Yuang Huang, W. Skamarock","doi":"10.1175/mwr-d-23-0237.1","DOIUrl":"https://doi.org/10.1175/mwr-d-23-0237.1","url":null,"abstract":"\u0000The Model for Prediction Across Scales (MPAS) with variable resolution (60-15-1 km) is used to investigate the track deflection of Typhoon Chanthu (2021) near Taiwan. Chanthu exhibited a rightward track deflection as it approached southeast Taiwan and underwent a leftward deflection when moving northward offshore of northeast Taiwan. Numerical experiments are conducted to identify the physical processes for the track deflection. The rightward deflection of the northbound typhoon is induced by the recirculating flow resulting from the effect of Taiwan’s topography. A wavenumber-one potential vorticity (PV) budget analysis indicates that horizontal PV advection dominates the earlier rightward deflection, while the later leftward deflection is mainly in response to stronger asymmetric cloud heating at low levels at the offshore quadrant of the typhoon. A pair of cyclonic and anticyclonic gyres in the wavenumber-one flow difference is induced by Taiwan’s topography. These rotate counterclockwise to drive the track deflection, most often in westbound typhoons. Idealized WRF simulations are also conducted to explore the track deflection under different northbound conditions. The simulations confirm the track deflection mechanism with similar PV dynamics to the MPAS simulations for Chanthu and illustrate the variabilities of the track deflection for different steering conditions and vortex origins. The rightward deflection of northbound typhoons is essentially determined by a reduced ratio of R/LE where R is the vortex size and LE is the effective length of the mountain range.","PeriodicalId":18824,"journal":{"name":"Monthly Weather Review","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141717069","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":"Probabilistic Neural Networks for Ensemble Postprocessing","authors":"Pu Liu, Markus Dabernig, Aitor Atencia, Yong Wang, Yuchu Zhao","doi":"10.1175/mwr-d-23-0220.1","DOIUrl":"https://doi.org/10.1175/mwr-d-23-0220.1","url":null,"abstract":"\u0000Accurate temperature forecasts are critical for various industries and sectors. We propose a probabilistic neural network (PNN), an extension of the distributional regression network (DRN), for 2-m temperature forecasts, consisting of three variants with different inputs and target variables. The first variant, standardized anomaly probabilistic neural network (SAPNN), employs a two-step approach involving standardized anomalies and global PNN modeling to effectively capture underlying features and anomalies. The second variant, PNN with geographical predictors (PNNGE), incorporates raw and static geographical predictors to enhance predictive performance. The third variant, PNN with station one-hot encoding (PNNEN), utilizes raw with station one-hot encoding predictors to represent geographical information effectively. We compare three PNN variants with two benchmarks: 1) standardized anomaly model output statistics (SAMOS) and 2) three DRN variants identical to those applied to PNN. These evaluations utilize ECMWF data from 2019 to 2020 at 6-h intervals up to 72 h over Hebei, China. Results show that SAPNN and PNNGE are better than SAMOS, while PNNEN notably exhibits a significant 14% improvement in the continuous ranked probability skill score (CRPSS). Moreover, the PNN variants exhibit comparable or superior performance to DRN regarding forecast accuracy, CRPSS, and reliability, showcasing a better-calibrated spread–error relationship. This study highlights the value of the proposed PNN variants with a distribution output in capturing nonlinear relationships within different sources of predictors and improving temperature forecast skills.\u0000\u0000\u0000This study aims to improve the accuracy, skills, and reliability of 2-m temperature forecasts, which are crucial in agriculture and energy management. To achieve this, we extend a popular artificial intelligence framework and explore four data sources with two schemes to systematically compare the predictive performances in making temperature forecasts. The findings of this research are vital as they offer novel ways to improve forecast skills. Imagine having a weather app that is significantly more accurate, enabling you to plan your day better. This study is about discovering innovative approaches to enhance forecast skills and reliability, which could benefit various aspects of our daily lives. One of the new methods even exhibits a 14% improvement in forecast skills.\u0000","PeriodicalId":18824,"journal":{"name":"Monthly Weather Review","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141707334","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":"A Tale of Two Novembers: Confounding influences on La Niña’s relationship with rainfall in Australia","authors":"C. Tozer, J. Risbey, M. Pook, D. Monselesan, Damien Irving, Nandini Ramesh, Doug Richardson","doi":"10.1175/mwr-d-23-0112.1","DOIUrl":"https://doi.org/10.1175/mwr-d-23-0112.1","url":null,"abstract":"\u0000Despite common background La Niña conditions, Australia was very dry in November 2020 and wet in November 2021. This paper aims to provide an explanation for this difference. Large-scale drivers of Australian rainfall, including the El Niño Southern Oscillation, Indian Ocean Dipole, Southern Annular Mode and Madden Julian Oscillation, were examined but did not provide obvious clues for the differences. We found that the absence (in 2020) or presence (in 2021) of an enhanced thermal wind and subtropical jet over the Australian continent contributed to the rainfall anomalies. In general, La Niña sets up warm sea surface temperatures around northern Australia, which enhances the meridional temperature gradient over the continent, and hence thermal wind and subtropical jet. In November 2021 these warm sea surface temperatures, coupled with a persistent mid-latitude trough, which advected cold air over the Australian continent, led to an enhanced meridional temperature gradient and subtropical jet over Australia. The enhanced jet provided favourable conditions for the development of rain-bearing weather systems across Australia. In 2020 the continent was warm, displacing the latitude of maximum meridional temperature gradient south of the continent, resulting in fewer instances of the subtropical jet over Australia, and little development of weather systems over the continent. We highlight that although La Niña tilts the odds to wetter conditions for Australia, in any given month, variability in temperatures over the continent can contribute to subtropical jet variability and resulting rainfall in ways which confound the normal expectation from La Niña.","PeriodicalId":18824,"journal":{"name":"Monthly Weather Review","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141351166","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":"Cold Surge Impacts on the Structure, Energy Budget, and Turbulence of the South China Sea Boundary Layer","authors":"Kuan-Yun Wang, Chung-Hsiung Sui, Mong-Ming Lu, Jing-Shan Hong","doi":"10.1175/mwr-d-23-0238.1","DOIUrl":"https://doi.org/10.1175/mwr-d-23-0238.1","url":null,"abstract":"\u0000Episodic cold surges in the East Asia winter monsoon can penetrate deep into the South China Sea (SCS), enhance consequent tropical rainfall, and further strengthen the East Asia meridional overturning circulation. These cold surges can promote strong surface fluxes and lead to a deeper marine boundary layer (MBL). However, there is a lack of boundary layer studies over the SCS, unlike many other well-studied regions such as the north Atlantic Ocean and the central-eastern Pacific Ocean. In this study, we use high resolution radiosonde data of temperature and humidity profiles over Dongsha Island (116.69E, 20.70N) to identify the inversion layer, mixed layer, cloud base, cloud top, and factors controlling low cloud cover for the period of December-January-February from 2010 to 2020. We perform an energy budget analysis with ERA-5 meteorological variables and surface fluxes. Here we show a strong turbulent flux convergence of both heat and moisture within the SCS MBL during cold surges, which leads to a lifting of the mixed layer to ~1.0 km and inversion layer to ~2.0 km and associated cloud development over Dongsha Island. The cold and dry horizontal advection is balanced by this vertical turbulent flux convergence in the energy budget. Overall, cold surges over the SCS enhance lower branch of winter monsoon meridional overturning circulation with stronger inversion and higher low cloud covers.","PeriodicalId":18824,"journal":{"name":"Monthly Weather Review","volume":null,"pages":null},"PeriodicalIF":3.2,"publicationDate":"2024-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141266722","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}