Quarterly Journal of the Royal Meteorological Society最新文献

{"title":"Joint estimation of sea ice and atmospheric state from microwave imagers in operational weather forecasting","authors":"Alan J. Geer","doi":"10.1002/qj.4797","DOIUrl":"https://doi.org/10.1002/qj.4797","url":null,"abstract":"Satellite‐observed microwave radiances provide information on both surface and atmosphere. For operational weather forecasting, information on atmospheric temperature, humidity, cloud, and precipitation is inferred directly using all‐sky radiance data assimilation. In contrast, information on the surface state, such as sea‐surface temperature (SST) and sea‐ice concentration (SIC), is typically provided through third‐party retrieval products. Scientifically, this is a sub‐optimal use of the observations, and practically it has disadvantages such as time delays of more than 48 h. A better solution is to estimate the surface and atmospheric state jointly from the radiance observations. This has not been possible until now, due to incomplete knowledge of the surface state and the radiative transfer that links this to the observed radiances. A new approach based on an empirical state and an empirical sea‐ice surface emissivity model is used here to add sea‐ice state estimation, including SIC, to the European Centre for Medium‐range Weather Forecasts atmospheric data assimilation system. The sea‐ice state is estimated using augmented control variables at the observation locations. The resulting SIC estimates are of good quality and they highlight apparent defects in the existing OCEAN5 sea‐ice analysis. The SIC estimates can also be used to track giant icebergs, which may provide a novel maritime application for passive microwave radiances. Further, the SIC estimates should be suitable for onward use in coupled ocean–atmosphere data assimilation. There is also increased coverage of microwave observations in the proximity of sea ice, leading to improved atmospheric forecasts out to day 4 in the Southern Ocean.","PeriodicalId":49646,"journal":{"name":"Quarterly Journal of the Royal Meteorological Society","volume":"29 1","pages":""},"PeriodicalIF":8.9,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141548739","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":"On the robustness of methods to account for background bias in data assimilation to uncertainties in the bias estimates","authors":"Alison M. Fowler","doi":"10.1002/qj.4790","DOIUrl":"https://doi.org/10.1002/qj.4790","url":null,"abstract":"Fundamental to the theory of data assimilation is that the data (i.e., the observations and the background) provide an unbiased estimate of the true state. There are many situations when this assumption is known to be far from valid; and without bias correction (BC), significant biases will be present in the resulting analysis. Here, we compare two methods to account for biases in the background that do not require a change to the data assimilation algorithm: explicit BC and covariance inflation (CI). When the background bias is known perfectly it is clear that the BC method outperforms the CI method, in that it can completely remove the effect of the background bias whereas the CI method can only reduce it. However, the background bias can only be estimated when unbiased observations are available. A lack of unbiased observations means that the estimate of the background bias will always be subject to sample errors and structural errors due to poor assumptions about how the bias varies in space and time. Given these difficulties in estimating the background bias, the robustness of the two methods in producing an unbiased analysis is studied within an idealised linear system. It is found that the CI method is much less sensitive to errors in the background bias estimate and that a smooth estimate of the bias is crucial to the success of the BC method. However, the CI method is more sensitive to uncorrected biases in the observations.","PeriodicalId":49646,"journal":{"name":"Quarterly Journal of the Royal Meteorological Society","volume":"32 1","pages":""},"PeriodicalIF":8.9,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141548534","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":"Investigating the role of tropical and extratropical waves in the Hadley circulation via present‐day Earth‐like to globally uniform sea‐surface temperature forcing","authors":"A.B.S. Thakur, Jai Sukhatme, Nili Harnik","doi":"10.1002/qj.4784","DOIUrl":"https://doi.org/10.1002/qj.4784","url":null,"abstract":"The tropical overturning circulation is examined in a moist aquaplanet general circulation model forced using a non‐interactive sea‐surface temperature (SST) distribution that varies between a present‐day Earth‐like profile and one that is globally uniform. A Hadley cell (HC)‐like flow is observed in all experiments along with the poleward transport of heat and angular momentum. In simulations with non‐zero SST gradients, deep convection near the Equator sets up a deep tropical cell; midlatitude baroclinic Rossby waves flux heat and angular momentum poleward, reinforcing the thermally direct circulation. As the imposed SST gradient is weakened, the HC transitions from a thermally and eddy‐driven regime to one that is completely eddy‐driven. When the SST is globally uniform, equatorial waves concentrate precipitation in the Tropics and facilitate the lower‐level convergence necessary for the ascending branch of the HC. Midlatitude Rossby waves generated near the surface become very weak, but upper‐level baroclinicity generates waves that cause equatorward transport of heat and poleward transport of momentum. Moreover, these upper‐level waves induce a circulation that opposes the time‐mean HC, thus highlighting the role of tropical waves in driving an overturning circulation that looks similar to the present‐day Earth‐like case, even for the case with globally uniform SSTs. In all cases, anomalies associated with the tropical waves closely resemble those that sum to give the upper‐level zonal mean divergent outflow. Through their ability to modulate tropical rainfall and the related latent heating, equatorial waves cause considerable hemispheric asymmetry in the HC and impart synoptic and intraseasonal variability to the tropical overturning circulation.","PeriodicalId":49646,"journal":{"name":"Quarterly Journal of the Royal Meteorological Society","volume":"38 1","pages":""},"PeriodicalIF":8.9,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141552603","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":"Correlation analysis between environmental factors and microphysical variables during the “Suizhou 812” heavy precipitation process in Suizhou City, Hubei Province of China","authors":"Yinglian Guo, Zhimin Zhou, Zhaoping Kang, Minghuan Wang, Jun Li, Chunguang Cui","doi":"10.1002/qj.4792","DOIUrl":"https://doi.org/10.1002/qj.4792","url":null,"abstract":"Based on numerical simulation, this study investigates the relationship between environmental factors and microphysical variables of a heavy precipitation event in Suizhou on August 12, 2021, aiming to provide a reference for studying the interaction mechanisms of physical processes involved at different scales. The results demonstrate that environmental instability factors give an early indication of heavy precipitation occurrence and play a crucial role in connecting microphysical processes in the middle/upper layers with water vapor uplift in the lower layers before and during heavy precipitation events. Most of the peak/valley values of both environmental factors and microphysical variables occur simultaneously with those of precipitation on the hourly time series. The vertical profile reveals that, before the occurrence of heavy precipitation, there is an initial strengthening of ascending movement in the middle to upper troposphere, leading to an increase in ice‐phase particles and cloud water within these layers. Additionally, gravity sedimentation and melting significantly contribute to increased rainwater content within the lower to middle layers. When heavy precipitation occurs, intensified vertical velocity, vorticity, and water vapor convergence results in a decrease in cloud/rain particles' peak height and an increase in graupel particles' peak height. This leads to a prolonged collision process and heightened rainfall intensity. Furthermore, enhanced water vapor convergence promotes raindrops formation through colliding and coalescing with cloud droplets. By comparing variables/factors between extreme hourly heavy precipitation and general hourly heavy precipitation, it is suggested that the strengthened self‐feedback mechanism between microphysical latent heat release and vorticity may be one of the reasons for the occurrence of extreme hourly heavy rainfall.","PeriodicalId":49646,"journal":{"name":"Quarterly Journal of the Royal Meteorological Society","volume":"21 1","pages":""},"PeriodicalIF":8.9,"publicationDate":"2024-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141503270","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":"Time variability and periodicities of cross‐regional hydroclimatic causation in the contiguous United States","authors":"Xueli Yang, Zhi‐Hua Wang, Qi Li, Ying‐Cheng Lai","doi":"10.1002/qj.4800","DOIUrl":"https://doi.org/10.1002/qj.4800","url":null,"abstract":"Identifying and understanding various causal relations are fundamental to climate dynamics for improving the predictive capacity of Earth system modeling. In particular, causality in Earth systems has manifest temporal periodicities, like physical climate variabilities. To unravel the characteristic frequency of causality in climate dynamics, we develop a data‐analytic framework based on a combination of causality detection and Hilbert spectral analysis, using a long‐term temperature and precipitation dataset in the contiguous United States. Using the Huang–Hilbert transform, we identify the intrinsic frequencies of cross‐regional causality for precipitation and temperature, ranging from interannual to interdecadal time scales. In addition, we analyze the spectra of the physical climate variabilities, including El Niño‐Southern Oscillation and Pacific Decadal Oscillation. It is found that the intrinsic causal frequencies are positively associated with the physics of the oscillations in the global climate system. The proposed methodology provides fresh insights into the causal connectivity in Earth's hydroclimatic system and its underlying mechanism as regulated by the characteristic low‐frequency variability associated with various climatic dynamics.","PeriodicalId":49646,"journal":{"name":"Quarterly Journal of the Royal Meteorological Society","volume":"539 1","pages":""},"PeriodicalIF":8.9,"publicationDate":"2024-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141503272","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":"Is a more physical representation of aerosol chemistry needed for fog forecasting?","authors":"Moumita Bhowmik, Anupam Hazra, Sachin D. Ghude, Sandeep Wagh, Rituparna Chowdhury, Avinash N. Parde, Gaurav Govardhan, Ismail Gultepe, M. Rajeevan","doi":"10.1002/qj.4729","DOIUrl":"https://doi.org/10.1002/qj.4729","url":null,"abstract":"With the changing climate, the study of fog formation is essential due to the impact of the complexity of natural and anthropogenic aerosols. The evolution of the droplet size distribution in the presence of different aerosol species remains poorly understood. To make progress towards reducing the uncertainty of fog forecasts, the Eulerian–Lagrangian particle‐based small‐scale model for the diffusional growth of droplets is used to better understand the droplet activation and growth. The small‐scale model simulations are performed using observed data from the Winter Fog Experiment study over Indira Gandhi International Airport, New Delhi. The microphysical properties, such as droplet number concentrations (Nd) and liquid water content (LWC), important for fog simulation, are evaluated to gain more insights. The small‐scale simulations have shown the droplet microphysical properties at different evolutionary stages. The Nd and effective radius change with variations in LWC for different aerosol chemistries (i.e., organics, mix, and inorganic). The calculated visibility at small scale is also shown with the variation of Nd and LWC. This study compared visibility from an existing parametrization with parcel–direct numerical simulation calculation. The hygroscopicity , which is highly related to the activation of aerosols to condensation nuclei, is taken into account to demonstrate the contribution of aerosol chemistry to fog droplet formation. The results highlight that hygroscopicity is essential in the numerical model for fog and visibility prediction as the microphysical properties of fog are regulated by aerosol species.","PeriodicalId":49646,"journal":{"name":"Quarterly Journal of the Royal Meteorological Society","volume":"57 1","pages":""},"PeriodicalIF":8.9,"publicationDate":"2024-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141503271","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 moisture budget perspective on Australian rainfall variability","authors":"Sunil Kumar Pariyar, Giovanni Liguori, Christian Jakob, Martin S. Singh, Michael J. Reeder, Michael A. Barnes","doi":"10.1002/qj.4778","DOIUrl":"https://doi.org/10.1002/qj.4778","url":null,"abstract":"Rainfall variability over Australia is revisited from the viewpoint of the atmospheric moisture budgets in three regions: the extratropics, Subtropics, and Tropics. The budgets are calculated using three‐hourly European Centre for Medium‐Range Weather Forecasts Reanalysis v5 (ERA5) and ERA5‐Land data between 1979 and 2022. The use of the moisture budget at short time‐scales enables the investigation of the relationship between synoptic weather‐scale processes and the longer term variability of the rainfall climate. The total variability in the vertically integrated moisture flux divergence (VIMD) is significantly larger than the evaporation minus precipitation (<jats:italic>E</jats:italic> − <jats:italic>P</jats:italic>), to a large extent due to the sub‐daily time‐scales. <jats:italic>E</jats:italic> − <jats:italic>P</jats:italic> is related more closely to moisture flux convergence in winter (summer) over south (north) Australia, suggesting a clear seasonality in the relationship between the two budget terms. The <jats:italic>E</jats:italic> − <jats:italic>P</jats:italic>–VIMD relationship is nearly in phase in the Tropics, whereas VIMD leads <jats:italic>E</jats:italic> − <jats:italic>P</jats:italic> by 9–15 hr with eastward‐propagating signals in the extratropics and Subtropics. Such seasonal and regional discrepancies in the relationship are attributed to the background state of moisture availability and temperature as represented by relative humidity and lifting condensation levels. The variability of the budget imbalance and its seasonality are dominated by the variability in VIMD. The imbalance reduces rapidly with temporal smoothing, with the storage term approaching zero at approximately 20 days, which can be thought of as making a transition time‐scale from high‐frequency weather‐related variability into slow‐varying background conditions. Weather‐related variability (cyclones, fronts, and thunderstorms) dominates the overall <jats:italic>E</jats:italic> − <jats:italic>P</jats:italic> variability in the extratropics and Subtropics, whereas slow‐varying background conditions contribute equally to the total variability in the Tropics.","PeriodicalId":49646,"journal":{"name":"Quarterly Journal of the Royal Meteorological Society","volume":"2013 1","pages":""},"PeriodicalIF":8.9,"publicationDate":"2024-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141526696","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The performance of the CoMorph‐A convection package in global simulations with the Met Office Unified Model","authors":"A. P. Lock, M. Whitall, A. J. Stirling, K. D. Williams, S. L. Lavender, C. Morcrette, K. Matsubayashi, P. R. Field, G. Martin, M. Willett, J. Heming","doi":"10.1002/qj.4781","DOIUrl":"https://doi.org/10.1002/qj.4781","url":null,"abstract":"The impact on global simulations of a new package of physical parametrizations in the Met Office Unified Model is documented. The main component of the package is an entirely new convection scheme, CoMorph. This has a mass‐flux structure that allows initiation of buoyant ascent from any level and the ability for plumes of differing originating levels to coexist in a grid box. It has a different form of closure, where the mass flux of initiation is dependent on local instability, and an implicit numerical solution for detrainment that yields smooth timestep behaviour. The scheme is coupled more consistently to the cloud, microphysics, and boundary‐layer parametrizations and, as a result, significant changes to these have also been made. The package, called CoMorph‐A, has been tested in a variety of single‐column and idealized regimes. Here we test it in global configurations and evaluate it against observations using a range of standard metrics. Overall it is found to perform well against the control. Biases in the climatologies of the radiative fluxes are significantly reduced across the Tropics and subtropics, tropical and extratropical cyclone statistics are improved, and the Madden–Julian oscillation and other propagating tropical waves are strengthened. It also improves overall scores in numerical weather prediction trials, without revisions to the data assimilation. There is still work to do to improve the diurnal cycle of precipitation over land, where the peak remains too close to the middle of the day.","PeriodicalId":49646,"journal":{"name":"Quarterly Journal of the Royal Meteorological Society","volume":"40 1","pages":""},"PeriodicalIF":8.9,"publicationDate":"2024-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141526697","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 mechanism for coastal fog genesis at evening transition","authors":"Thomas J. Hintz, Kelly Y. Huang, Sebastian W. Hoch, Stef L. Bardoel, Saša Gaberšek, Ismail Gultepe, Jesus Ruiz‐Plancarte, Eric R. Pardyjak, Qing Wang, Harindra J. S. Fernando","doi":"10.1002/qj.4732","DOIUrl":"https://doi.org/10.1002/qj.4732","url":null,"abstract":"Transitional changes in the atmospheric boundary layer (ABL) are known to facilitate the onset of terrestrial fog, which is defined as a condition with near‐surface visibility &lt;1 km due to airborne water droplets. In particular, the evening transition from a daytime convective ABL to a night‐time stable ABL provides favorable conditions for fog. This article describes a local fog event observed during the evening transition at a Canadian islet in the north Atlantic known as Sable Island during the “Fog and Turbulence Interactions in the Marine Atmosphere (Fatima)” field campaign. The comprehensive set of data collected using a myriad of instruments covering a wide range of scales allowed identification of a novel mechanism underlying this fog event. Therein an ocean–land discontinuity created a flow regime consisting of several stacked boundary layers, interplay of which produced a thin low‐level cloud that then diffused downward to the surface, causing visibility reduction. This mechanism offers useful insights on the role of boundary layers, stratification, and turbulence in fog genesis over oceanic islands.","PeriodicalId":49646,"journal":{"name":"Quarterly Journal of the Royal Meteorological Society","volume":"73 1","pages":""},"PeriodicalIF":8.9,"publicationDate":"2024-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141503273","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 machine‐learning approach to thunderstorm forecasting through post‐processing of simulation data","authors":"Kianusch Vahid Yousefnia, Tobias Bölle, Isabella Zöbisch, Thomas Gerz","doi":"10.1002/qj.4777","DOIUrl":"https://doi.org/10.1002/qj.4777","url":null,"abstract":"Thunderstorms pose a major hazard to society and the economy, which calls for reliable thunderstorm forecasts. In this work, we introduce SALAMA, a feedforward neural network model for identifying thunderstorm occurrence in numerical weather prediction (NWP) data. The model is trained on convection‐resolving ensemble forecasts over central Europe and lightning observations. Given only a set of pixel‐wise input parameters that are extracted from NWP data and related to thunderstorm development, SALAMA infers the probability of thunderstorm occurrence in a reliably calibrated manner. For lead times up to 11 h, we find a forecast skill superior to classification based only on NWP reflectivity. Varying the spatiotemporal criteria by which we associate lightning observations with NWP data, we show that the time‐scale for skillful thunderstorm predictions increases linearly with the spatial scale of the forecast.","PeriodicalId":49646,"journal":{"name":"Quarterly Journal of the Royal Meteorological Society","volume":"10 1","pages":""},"PeriodicalIF":8.9,"publicationDate":"2024-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141526698","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}