Matjaž Puh, Christian Keil, Christoph Gebhardt, C. Marsigli, Mirjam Hirt, Fabian Jakub, George C. Craig
The physically based stochastic perturbation scheme PSP has been implemented in the convection‐permitting ICON‐D2 ensemble prediction system at DWD and run for a three‐month trial experiment in summer 2021. The scheme mimics the impact of boundary layer turbulence on the smallest resolved scales and impacts in particular convective precipitation. A weather regime‐dependent systematic evaluation shows that PSP efficiently increases ensemble spread of precipitation in weak synoptic forcing, while producing realistic convective structures. During strong forcing, the effect of the scheme is negligible, as expected by design. The probabilistic verification shows improvements in the forecast skill of other variables as well, especially the spread to skill ratio, but identifies starting points for further improvements of the method.This article is protected by copyright. All rights reserved.
{"title":"Physically based stochastic perturbations improve high‐resolution forecast of convection","authors":"Matjaž Puh, Christian Keil, Christoph Gebhardt, C. Marsigli, Mirjam Hirt, Fabian Jakub, George C. Craig","doi":"10.1002/qj.4574","DOIUrl":"https://doi.org/10.1002/qj.4574","url":null,"abstract":"The physically based stochastic perturbation scheme PSP has been implemented in the convection‐permitting ICON‐D2 ensemble prediction system at DWD and run for a three‐month trial experiment in summer 2021. The scheme mimics the impact of boundary layer turbulence on the smallest resolved scales and impacts in particular convective precipitation. A weather regime‐dependent systematic evaluation shows that PSP efficiently increases ensemble spread of precipitation in weak synoptic forcing, while producing realistic convective structures. During strong forcing, the effect of the scheme is negligible, as expected by design. The probabilistic verification shows improvements in the forecast skill of other variables as well, especially the spread to skill ratio, but identifies starting points for further improvements of the method.This article is protected by copyright. All rights reserved.","PeriodicalId":49646,"journal":{"name":"Quarterly Journal of the Royal Meteorological Society","volume":" ","pages":""},"PeriodicalIF":8.9,"publicationDate":"2023-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46311001","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}
The effect of a sub‐grid scale cloud field on the propagation of long atmospheric waves is investigated using a new scale‐consistent formulation based upon the asymptotic theory of homogenisation. A key aim is to quantify potential model errors in wave propagation speeds, introduced by using averaged fields in place of the fully resolved circulation, in the setting of a simple stratified Boussinesq mid‐latitude β‐channel model. The effect of the cloud field, represented here by a random array of strongly nonlinear axisymmetric circulations, is found to appear in the large‐scale governing equations through new terms which redistribute the large‐scale buoyancy and horizontal momentum fields in the vertical. These new terms, which have the form of non‐local integral operators, are linear in the cloud number density, and are fully determined by the solution of a linear elliptic equation known as a cell problem. The cell problem in turn depends upon the details of the nonlinear cloud circulations. The integral operators are calculated explicitly for example cloud fields and then dispersion relations are compared for different waves in the presence of clouds at realistic densities. The main finding is that baroclinic Rossby waves are significantly slowed and damped by the clouds, whilst inertia‐gravity waves are affected almost exclusively by damping, most strongly at the lowest frequencies. In contrast, all waves with a barotropic structure are found to be almost unaffected by the presence of clouds, even at the highest realistic cloud densities.An important consequence of this study is a new approach to the closure of sub‐grid scale cloud fields in the parameterisation of convection in large‐scale atmospheric models.This article is protected by copyright. All rights reserved.
{"title":"Wave propagation through a stationary field of clouds: a homogenisation approach","authors":"E. J. Goldsmith, James G. Esler","doi":"10.1002/qj.4567","DOIUrl":"https://doi.org/10.1002/qj.4567","url":null,"abstract":"The effect of a sub‐grid scale cloud field on the propagation of long atmospheric waves is investigated using a new scale‐consistent formulation based upon the asymptotic theory of homogenisation. A key aim is to quantify potential model errors in wave propagation speeds, introduced by using averaged fields in place of the fully resolved circulation, in the setting of a simple stratified Boussinesq mid‐latitude β‐channel model. The effect of the cloud field, represented here by a random array of strongly nonlinear axisymmetric circulations, is found to appear in the large‐scale governing equations through new terms which redistribute the large‐scale buoyancy and horizontal momentum fields in the vertical. These new terms, which have the form of non‐local integral operators, are linear in the cloud number density, and are fully determined by the solution of a linear elliptic equation known as a cell problem. The cell problem in turn depends upon the details of the nonlinear cloud circulations. The integral operators are calculated explicitly for example cloud fields and then dispersion relations are compared for different waves in the presence of clouds at realistic densities. The main finding is that baroclinic Rossby waves are significantly slowed and damped by the clouds, whilst inertia‐gravity waves are affected almost exclusively by damping, most strongly at the lowest frequencies. In contrast, all waves with a barotropic structure are found to be almost unaffected by the presence of clouds, even at the highest realistic cloud densities.An important consequence of this study is a new approach to the closure of sub‐grid scale cloud fields in the parameterisation of convection in large‐scale atmospheric models.This article is protected by copyright. All rights reserved.","PeriodicalId":49646,"journal":{"name":"Quarterly Journal of the Royal Meteorological Society","volume":" ","pages":""},"PeriodicalIF":8.9,"publicationDate":"2023-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46806140","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}
Cycling data assimilation and forecast experiments in August 2016 together with a case study of an intense Arctic Cyclone (AC16) are performed using the community Weather Research and Forecasting (WRF) model's Data Assimilation system (WRFDA). Three‐Dimensional Variational (3DVAR) and Multi‐Resolution Incremental Four‐Dimensional Variational (MRI‐4DVAR) data assimilation along with Polar WRF are applied to evaluate MRI‐4DVAR performance during a 20‐day cycling run, to investigate the impacts of initial conditions on the forecast skill of AC16, and to identify the factors impacting AC16's predictability. Six‐hourly continuous cycling experiments started from 1 August 2016 with 7‐day free forecasts initialized at each 0000 UTC. The results from departure statistics and forecast verification throughout the 20‐day period indicate the robustness and reliability of MRI‐4DVAR. For the AC16 case study, multiple processes, including merging of arctic cyclones, merging of vortices, vertical coupling between low‐level and upper‐level circulations, baroclinic processes and jet stream forcing, contributed to its generation and development. Compared to the initial conditions produced by 4DVAR, 3DVAR produced amplified vortices, stronger baroclinic instability, intensified upper‐level jet streams and a stronger low‐level frontal zone. These factors caused early strengthening of the dominant Arctic Cyclone and led to the early coupling between the low‐level Arctic cyclone and upper‐level vortices that resulted in the over development of AC16 in 3DVAR. For MRI‐4DVAR, the successful prediction of AC16 is likely due primarily to the more accurate simulation of upper‐level atmospheric fields, that was facilitated by better satellite radiance assimilation resulting from MRI‐4DVAR producing a balanced initial model state.This article is protected by copyright. All rights reserved.
{"title":"Improved Forecasting of the Extreme Arctic Cyclone in August 2016 with WRF MRI‐4DVAR","authors":"J. Ban, Zhiquan Liu, D. Bromwich, L. Bai","doi":"10.1002/qj.4569","DOIUrl":"https://doi.org/10.1002/qj.4569","url":null,"abstract":"Cycling data assimilation and forecast experiments in August 2016 together with a case study of an intense Arctic Cyclone (AC16) are performed using the community Weather Research and Forecasting (WRF) model's Data Assimilation system (WRFDA). Three‐Dimensional Variational (3DVAR) and Multi‐Resolution Incremental Four‐Dimensional Variational (MRI‐4DVAR) data assimilation along with Polar WRF are applied to evaluate MRI‐4DVAR performance during a 20‐day cycling run, to investigate the impacts of initial conditions on the forecast skill of AC16, and to identify the factors impacting AC16's predictability. Six‐hourly continuous cycling experiments started from 1 August 2016 with 7‐day free forecasts initialized at each 0000 UTC. The results from departure statistics and forecast verification throughout the 20‐day period indicate the robustness and reliability of MRI‐4DVAR. For the AC16 case study, multiple processes, including merging of arctic cyclones, merging of vortices, vertical coupling between low‐level and upper‐level circulations, baroclinic processes and jet stream forcing, contributed to its generation and development. Compared to the initial conditions produced by 4DVAR, 3DVAR produced amplified vortices, stronger baroclinic instability, intensified upper‐level jet streams and a stronger low‐level frontal zone. These factors caused early strengthening of the dominant Arctic Cyclone and led to the early coupling between the low‐level Arctic cyclone and upper‐level vortices that resulted in the over development of AC16 in 3DVAR. For MRI‐4DVAR, the successful prediction of AC16 is likely due primarily to the more accurate simulation of upper‐level atmospheric fields, that was facilitated by better satellite radiance assimilation resulting from MRI‐4DVAR producing a balanced initial model state.This article is protected by copyright. All rights reserved.","PeriodicalId":49646,"journal":{"name":"Quarterly Journal of the Royal Meteorological Society","volume":" ","pages":""},"PeriodicalIF":8.9,"publicationDate":"2023-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47568336","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}
Julia F. Lockwood, N. Stringer, Katie R. Hodge, P. Bett, J. Knight, Doug Smith, Adam A. Scaife, Matthew Patterson, N. Dunstone, H. Thornton
Recent studies have shown that seasonal forecasting systems have significant skill in predicting Northern European winds and storms in winter, but other seasons have not been so extensively analysed. Given this fact, and coupled with requests from users of the Met Office 3‐month outlook for the UK, we have investigated the skill in predicting seasonal (3‐month) mean UK wind speed and storms (extreme winds) with a one‐month lead‐time, throughout the year, using a large ensemble from the Met Office's seasonal prediction system, GloSea. We find that seasonal UK storms and mean wind speeds are well correlated, and therefore a single prediction of UK mean wind speed will give an indication of predicted storm counts. Skill for these predictions is highest in winter (December–February), related to predictability of the North Atlantic oscillation. In contrast, summer (June–August) UK wind skill is not significant and furthermore appears to be negative. We find evidence, in both observations and model members, for a Rossby wave from the tropics influencing UK summer winds and forming a significant predictable component in the model ensemble mean. However, the model predictable signal appears to be out of phase with that observed leading to the negative correlation. Further investigation into summer Rossby wave generation and propagation is necessary to understand whether summer predictions could be improved.This article is protected by copyright. All rights reserved.
{"title":"Seasonal prediction of UK mean and extreme winds","authors":"Julia F. Lockwood, N. Stringer, Katie R. Hodge, P. Bett, J. Knight, Doug Smith, Adam A. Scaife, Matthew Patterson, N. Dunstone, H. Thornton","doi":"10.1002/qj.4568","DOIUrl":"https://doi.org/10.1002/qj.4568","url":null,"abstract":"Recent studies have shown that seasonal forecasting systems have significant skill in predicting Northern European winds and storms in winter, but other seasons have not been so extensively analysed. Given this fact, and coupled with requests from users of the Met Office 3‐month outlook for the UK, we have investigated the skill in predicting seasonal (3‐month) mean UK wind speed and storms (extreme winds) with a one‐month lead‐time, throughout the year, using a large ensemble from the Met Office's seasonal prediction system, GloSea. We find that seasonal UK storms and mean wind speeds are well correlated, and therefore a single prediction of UK mean wind speed will give an indication of predicted storm counts. Skill for these predictions is highest in winter (December–February), related to predictability of the North Atlantic oscillation. In contrast, summer (June–August) UK wind skill is not significant and furthermore appears to be negative. We find evidence, in both observations and model members, for a Rossby wave from the tropics influencing UK summer winds and forming a significant predictable component in the model ensemble mean. However, the model predictable signal appears to be out of phase with that observed leading to the negative correlation. Further investigation into summer Rossby wave generation and propagation is necessary to understand whether summer predictions could be improved.This article is protected by copyright. All rights reserved.","PeriodicalId":49646,"journal":{"name":"Quarterly Journal of the Royal Meteorological Society","volume":" ","pages":""},"PeriodicalIF":8.9,"publicationDate":"2023-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47875036","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}
Jana Popová, Zbynek Sokol, Pao Wang, Jaroslav Svoboda
The study analyses a winter thunderstorm that passed over the Milešovka meteorological observatory on February 4, 2022, between 23:00 and 23:30 UTC. Lightning was recorded directly over the observatory by both the observer and the EUCLID lightning network at 23:20 UTC. To analyse the state of the atmosphere at the time when the lightning occurred, we used data from the X‐band Doppler polarimetric radar and the Ka‐band Doppler polarimetric vertical profiler, both located at the observatory. We also applied data from the Meteosat Second Generation satellite, and data from standard meteorological instruments located at the observatory. In addition, we run our cloud electrification model to simulate cloud electrification of the winter thunderstorm to find out whether the model develops conditions suitable for the occurrence of lightning and if so, under what circumstances. Our results show that the lightning appeared at the very end of the storm passage defined by high radar reflectivity. At the same time, it is clear from the radar observations that before lightning occurred, the cloud contained hydrometeors (graupel, cloud or rain water, and ice or snow) which are commonly associated to charge separation by collisions. Our analysis of the radar data also suggests that in at least several parts of the cloud the electric field was strong. Although the cloud top height was very low compared to summer storms, the model results indicate conditions suitable for lightning occurrence. However, an uncertainty remains on how to properly formulate the initial conditions for model simulations for this type of storm which was shallow and occurs rarely in winter.This article is protected by copyright. All rights reserved.
{"title":"Observations and modelling of the winter thunderstorm on February 4, 2022 at the Milešovka meteorological observatory","authors":"Jana Popová, Zbynek Sokol, Pao Wang, Jaroslav Svoboda","doi":"10.1002/qj.4572","DOIUrl":"https://doi.org/10.1002/qj.4572","url":null,"abstract":"The study analyses a winter thunderstorm that passed over the Milešovka meteorological observatory on February 4, 2022, between 23:00 and 23:30 UTC. Lightning was recorded directly over the observatory by both the observer and the EUCLID lightning network at 23:20 UTC. To analyse the state of the atmosphere at the time when the lightning occurred, we used data from the X‐band Doppler polarimetric radar and the Ka‐band Doppler polarimetric vertical profiler, both located at the observatory. We also applied data from the Meteosat Second Generation satellite, and data from standard meteorological instruments located at the observatory. In addition, we run our cloud electrification model to simulate cloud electrification of the winter thunderstorm to find out whether the model develops conditions suitable for the occurrence of lightning and if so, under what circumstances. Our results show that the lightning appeared at the very end of the storm passage defined by high radar reflectivity. At the same time, it is clear from the radar observations that before lightning occurred, the cloud contained hydrometeors (graupel, cloud or rain water, and ice or snow) which are commonly associated to charge separation by collisions. Our analysis of the radar data also suggests that in at least several parts of the cloud the electric field was strong. Although the cloud top height was very low compared to summer storms, the model results indicate conditions suitable for lightning occurrence. However, an uncertainty remains on how to properly formulate the initial conditions for model simulations for this type of storm which was shallow and occurs rarely in winter.This article is protected by copyright. All rights reserved.","PeriodicalId":49646,"journal":{"name":"Quarterly Journal of the Royal Meteorological Society","volume":" ","pages":""},"PeriodicalIF":8.9,"publicationDate":"2023-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41786576","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}
Ruhui Gan, Yi Yang, Hong Li, Shuchang Guo, Qian Xie, Liu Peng
Increasing convection information in initial field and weakening spurious convection information are hot topics in numerical weather prediction (NWP). How to economically assimilate radar reflectivity in non‐convective region (NCR) is the focus of this study. This study proposed a new assimilation scheme for the two‐dimensional (2D) composite reflectivity in NCR through the ensemble square root filter (EnSRF) method. A single column observation test and two convective cases are studied to verify the assimilation effect. Three experiments are designed for each test, including a control experiment (Exp_CTL) that only assimilates convective reflectivity and two assimilation experiments that assimilate reflectivity in NCR (one assimilates 3D weak reflectivity [Exp_RF] and the other assimilates 2D composite reflectivity [Exp_CRF]) based on the Exp_CTL. The results of real case studies show that the new scheme has two clear advantages. One is that it can save approximately three‐quarters of the assimilation workload. The other is that the new scheme has the most significant effect on weakening spurious convection and decreasing the FARs of precipitation and reflectivity.This article is protected by copyright. All rights reserved.
{"title":"An economical assimilation scheme for radar reflectivity in non‐convective region to suppress spurious precipitation","authors":"Ruhui Gan, Yi Yang, Hong Li, Shuchang Guo, Qian Xie, Liu Peng","doi":"10.1002/qj.4571","DOIUrl":"https://doi.org/10.1002/qj.4571","url":null,"abstract":"Increasing convection information in initial field and weakening spurious convection information are hot topics in numerical weather prediction (NWP). How to economically assimilate radar reflectivity in non‐convective region (NCR) is the focus of this study. This study proposed a new assimilation scheme for the two‐dimensional (2D) composite reflectivity in NCR through the ensemble square root filter (EnSRF) method. A single column observation test and two convective cases are studied to verify the assimilation effect. Three experiments are designed for each test, including a control experiment (Exp_CTL) that only assimilates convective reflectivity and two assimilation experiments that assimilate reflectivity in NCR (one assimilates 3D weak reflectivity [Exp_RF] and the other assimilates 2D composite reflectivity [Exp_CRF]) based on the Exp_CTL. The results of real case studies show that the new scheme has two clear advantages. One is that it can save approximately three‐quarters of the assimilation workload. The other is that the new scheme has the most significant effect on weakening spurious convection and decreasing the FARs of precipitation and reflectivity.This article is protected by copyright. All rights reserved.","PeriodicalId":49646,"journal":{"name":"Quarterly Journal of the Royal Meteorological Society","volume":" ","pages":""},"PeriodicalIF":8.9,"publicationDate":"2023-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44614313","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}
Ho‐Hsuan Wei, Aneesh C. Subramanian, K. Karnauskas, Danni Du, M. Balmaseda, Beena B. Sarojini, F. Vitart, C. DeMott, M. Mazloff
The tropical Pacific plays an important role in modulating the global climate through its prevailing sea surface temperature spatial structure and dominant climate modes like ENSO, MJO, and their teleconnections. These modes of variability, including their oceanic anomalies, are considered to provide sources of prediction skill on subseasonal timescales in the tropics. Therefore, this study aims to examine how assimilating in‐situ ocean observations influences the initial ocean sea surface temperature (SST) and mixed layer depth (MLD) and their subseasonal forecasts. We analyze two subseasonal forecast systems generated with European Centre for Medium‐Range Weather Forecasts (ECMWF) Integrated Forecast System (IFS) where the ocean states were initialized using two Observing System Experiment (OSE) reanalyses. We find that the SST differences between forecasts with and without ocean data assimilation grow with time, resulting in a reduced cold tongue bias when assimilating ocean observations. Two mechanisms related to air‐sea coupling are considered to contribute to this growth of SST differences. One is a positive feedback between zonal SST gradient, pressure gradient, and surface wind. The other is the difference in Ekman suction and mixing at the equator due to surface wind speed differences. While the initial mixed layer depth (MLD) can be improved through ocean data assimilation, this improvement is not maintained in the forecasts. Instead, the MLD in both experiments rapidly shoals at the beginning of the forecast. These results emphasize how initialization and model biases influence the air‐sea interaction and the accuracy of subseasonal forecast in the tropical Pacific.This article is protected by copyright. All rights reserved.
{"title":"The role of in‐situ ocean data assimilation in ECMWF subseasonal forecasts of SST and MLD over the tropical Pacific Ocean","authors":"Ho‐Hsuan Wei, Aneesh C. Subramanian, K. Karnauskas, Danni Du, M. Balmaseda, Beena B. Sarojini, F. Vitart, C. DeMott, M. Mazloff","doi":"10.1002/qj.4570","DOIUrl":"https://doi.org/10.1002/qj.4570","url":null,"abstract":"The tropical Pacific plays an important role in modulating the global climate through its prevailing sea surface temperature spatial structure and dominant climate modes like ENSO, MJO, and their teleconnections. These modes of variability, including their oceanic anomalies, are considered to provide sources of prediction skill on subseasonal timescales in the tropics. Therefore, this study aims to examine how assimilating in‐situ ocean observations influences the initial ocean sea surface temperature (SST) and mixed layer depth (MLD) and their subseasonal forecasts. We analyze two subseasonal forecast systems generated with European Centre for Medium‐Range Weather Forecasts (ECMWF) Integrated Forecast System (IFS) where the ocean states were initialized using two Observing System Experiment (OSE) reanalyses. We find that the SST differences between forecasts with and without ocean data assimilation grow with time, resulting in a reduced cold tongue bias when assimilating ocean observations. Two mechanisms related to air‐sea coupling are considered to contribute to this growth of SST differences. One is a positive feedback between zonal SST gradient, pressure gradient, and surface wind. The other is the difference in Ekman suction and mixing at the equator due to surface wind speed differences. While the initial mixed layer depth (MLD) can be improved through ocean data assimilation, this improvement is not maintained in the forecasts. Instead, the MLD in both experiments rapidly shoals at the beginning of the forecast. These results emphasize how initialization and model biases influence the air‐sea interaction and the accuracy of subseasonal forecast in the tropical Pacific.This article is protected by copyright. All rights reserved.","PeriodicalId":49646,"journal":{"name":"Quarterly Journal of the Royal Meteorological Society","volume":" ","pages":""},"PeriodicalIF":8.9,"publicationDate":"2023-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45732177","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":"Erratum to 'A conditional decomposition of proper scores: quantifying the sources of information in a forecast'","authors":"S. Allen, C. Ferro, F. Kwasniok","doi":"10.1002/qj.4565","DOIUrl":"https://doi.org/10.1002/qj.4565","url":null,"abstract":"","PeriodicalId":49646,"journal":{"name":"Quarterly Journal of the Royal Meteorological Society","volume":" ","pages":""},"PeriodicalIF":8.9,"publicationDate":"2023-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43335304","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}
The boundary layer plays a key role in several aspects of hurricane dynamics. Here we focus on its contribution to the balanced circulation. Previous studies, whilst including centrifugal terms, have not included an explicit balance in the boundary layer. Here, we improve the balanced theory to include an Ekman balance, the so‐called Frictional Axisymmetric Vortex (FAV). This approach is analogous to semi‐geostrophic theory that includes a realistic boundary‐layer diffusion: semi‐geotriptic (SGT) theory. We formulate the FAV for an axisymmetric system in cylindrical polar coordinates. We then derive a Sawyer‐Eliassen equation for the vertical circulation. Example solutions for both an idealised hurricane‐scale and synoptic‐scale vortex are compared.This article is protected by copyright. All rights reserved.
{"title":"A balanced model of a hurricane vortex coupled to a boundary layer","authors":"R. Beare, M. Cullen","doi":"10.1002/qj.4556","DOIUrl":"https://doi.org/10.1002/qj.4556","url":null,"abstract":"The boundary layer plays a key role in several aspects of hurricane dynamics. Here we focus on its contribution to the balanced circulation. Previous studies, whilst including centrifugal terms, have not included an explicit balance in the boundary layer. Here, we improve the balanced theory to include an Ekman balance, the so‐called Frictional Axisymmetric Vortex (FAV). This approach is analogous to semi‐geostrophic theory that includes a realistic boundary‐layer diffusion: semi‐geotriptic (SGT) theory. We formulate the FAV for an axisymmetric system in cylindrical polar coordinates. We then derive a Sawyer‐Eliassen equation for the vertical circulation. Example solutions for both an idealised hurricane‐scale and synoptic‐scale vortex are compared.This article is protected by copyright. All rights reserved.","PeriodicalId":49646,"journal":{"name":"Quarterly Journal of the Royal Meteorological Society","volume":" ","pages":""},"PeriodicalIF":8.9,"publicationDate":"2023-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43244850","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}
The thermal air‐sea interaction mechanism that modulates the atmospheric mixing by the sea surface temperature (SST) variability is studied with long‐term consistent satellite records. Statistical analyses of daily and instantaneous wind and SST data are performed over the major western boundary currents (WBCs). This wind‐SST coupling, that is mediated by the atmospheric mixing, is found to be very relevant on daily, and even shorter, time scales. Co‐located and simultaneous SST and surface wind fields (from Advanced Very High Resolution Radiometer and Advanced Scatterometer data) reveal that the atmosphere responds instantaneously to the presence of SST structures with a larger coupling coefficient with respect to daily and monthly time averaged fields. The coupling strength varies seasonally over the WBCs in the Northern Hemisphere, with the winter‐time coupling being the lowest. Reanalysis data show that this behaviour is related to the seasonality of the air‐sea temperature difference over the region of interest. Over the Northern Hemisphere WBCs, dry and cold continental air masses drive very unstable conditions, associated with a very weak thermal air‐sea coupling.This article is protected by copyright. All rights reserved.
{"title":"Satellite signature of the instantaneous wind response to mesoscale oceanic thermal structures","authors":"A. Meroni, Fabien Desbiolles, C. Pasquero","doi":"10.1002/qj.4561","DOIUrl":"https://doi.org/10.1002/qj.4561","url":null,"abstract":"The thermal air‐sea interaction mechanism that modulates the atmospheric mixing by the sea surface temperature (SST) variability is studied with long‐term consistent satellite records. Statistical analyses of daily and instantaneous wind and SST data are performed over the major western boundary currents (WBCs). This wind‐SST coupling, that is mediated by the atmospheric mixing, is found to be very relevant on daily, and even shorter, time scales. Co‐located and simultaneous SST and surface wind fields (from Advanced Very High Resolution Radiometer and Advanced Scatterometer data) reveal that the atmosphere responds instantaneously to the presence of SST structures with a larger coupling coefficient with respect to daily and monthly time averaged fields. The coupling strength varies seasonally over the WBCs in the Northern Hemisphere, with the winter‐time coupling being the lowest. Reanalysis data show that this behaviour is related to the seasonality of the air‐sea temperature difference over the region of interest. Over the Northern Hemisphere WBCs, dry and cold continental air masses drive very unstable conditions, associated with a very weak thermal air‐sea coupling.This article is protected by copyright. All rights reserved.","PeriodicalId":49646,"journal":{"name":"Quarterly Journal of the Royal Meteorological Society","volume":" ","pages":""},"PeriodicalIF":8.9,"publicationDate":"2023-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48842553","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}
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