Search Results - "Lawless, Amos S."
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Treating Sample Covariances for Use in Strongly Coupled Atmosphere‐Ocean Data Assimilation
Published in Geophysical research letters (16-01-2018)“…Strongly coupled data assimilation requires cross‐domain forecast error covariances; information from ensembles can be used, but limited sampling means that…”
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Exploring strategies for coupled 4D-Var data assimilation using an idealised atmosphere-ocean model
Published in Tellus. Series A, Dynamic meteorology and oceanography (01-01-2015)“…Operational forecasting centres are currently developing data assimilation systems for coupled atmosphere-ocean models. Strongly coupled assimilation, in which…”
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Improving the condition number of estimated covariance matrices
Published in Tellus. Series A, Dynamic meteorology and oceanography (01-01-2020)“…High dimensional error covariance matrices and their inverses are used to weight the contribution of observation and background information in data…”
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Investigating the role of prior and observation error correlations in improving a model forecast of forest carbon balance using Four-dimensional Variational data assimilation
Published in Agricultural and forest meteorology (15-11-2016)“…•Four-dimensional Variational data assimilation implemented with DALEC2 model.•Error correlations in prior information and observations proposed.•Including…”
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Quantifying the latitudinal representivity of in situ solar wind observations
Published in Journal of space weather and space climate (2020)“…Advanced space-weather forecasting relies on the ability to accurately predict near-Earth solar wind conditions. For this purpose, physics-based, global…”
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Estimating correlated observation error statistics using an ensemble transform Kalman filter
Published in Tellus. Series A, Dynamic meteorology and oceanography (01-01-2014)“…For certain observing types, such as those that are remotely sensed, the observation errors are correlated and these correlations are state- and…”
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Parameter estimation for a morphochemical reaction-diffusion model of electrochemical pattern formation
Published in Inverse problems in science and engineering (04-05-2019)“…The process of electrodeposition can be described in terms of a reaction-diffusion partial differential equation (PDE) system that models the dynamics of the…”
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Assessment of short‐range forecast error atmosphere–ocean cross‐correlations from the Met Office coupled numerical weather prediction system
Published in Quarterly journal of the Royal Meteorological Society (01-07-2024)“…Operational data assimilation systems for coupled atmosphere–ocean prediction are usually “weakly coupled”, in which there is no explicit interaction between…”
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Conditioning of hybrid variational data assimilation
Published in Numerical linear algebra with applications (01-03-2024)“…In variational assimilation, the most probable state of a dynamical system under Gaussian assumptions for the prior and likelihood can be found by solving a…”
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The effective use of anchor observations in variational bias correction in the presence of model bias
Published in Quarterly journal of the Royal Meteorological Society (01-07-2023)“…In numerical weather prediction, satellite radiance observations have a significant impact on forecast skill. However, radiance observations must usually be…”
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Convergent least-squares optimization methods for variational data assimilation
Published in Optimization (01-11-2024)“…Data assimilation combines prior (or background) information with observations to estimate the initial state of a dynamical system over a given time-window. A…”
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The role of cross‐domain error correlations in strongly coupled 4D‐Var atmosphere–ocean data assimilation
Published in Quarterly journal of the Royal Meteorological Society (01-07-2020)“…Strongly coupled atmosphere–ocean data assimilation offers the ability to improve information exchange across the modelled air‐sea interface by enabling…”
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On time‐parallel preconditioning for the state formulation of incremental weak constraint 4D‐Var
Published in Quarterly journal of the Royal Meteorological Society (01-10-2021)“…Using a high degree of parallelism is essential for the efficient performance of data assimilation. The state formulation of the incremental weak constraint…”
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Randomised preconditioning for the forcing formulation of weak‐constraint 4D‐Var
Published in Quarterly journal of the Royal Meteorological Society (01-10-2021)“…There is growing awareness that errors in the model equations cannot be ignored in data assimilation methods such as four‐dimensional variational assimilation…”
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The impact of hybrid oceanic data assimilation in a coupled model: A case study of a tropical cyclone
Published in Quarterly journal of the Royal Meteorological Society (01-07-2022)“…Tropical cyclones tend to result in distinctive spatial and temporal characteristics in the upper ocean, which suggests that traditional, parametrisation‐based…”
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The impact of using reconditioned correlated observation‐error covariance matrices in the Met Office 1D‐Var system
Published in Quarterly journal of the Royal Meteorological Society (01-04-2020)“…Recent developments in numerical weather prediction have led to the use of correlated observation‐error covariance (OEC) information in data assimilation and…”
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New bounds on the condition number of the Hessian of the preconditioned variational data assimilation problem
Published in Numerical linear algebra with applications (01-01-2022)“…Data assimilation algorithms combine prior and observational information, weighted by their respective uncertainties, to obtain the most likely posterior of a…”
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The conditioning of least‐squares problems in variational data assimilation
Published in Numerical linear algebra with applications (01-10-2018)“…Summary In variational data assimilation a least‐squares objective function is minimised to obtain the most likely state of a dynamical system. This objective…”
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Spectral estimates for saddle point matrices arising in weak constraint four‐dimensional variational data assimilation
Published in Numerical linear algebra with applications (01-10-2020)“…Summary We consider the large sparse symmetric linear systems of equations that arise in the solution of weak constraint four‐dimensional variational data…”
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Weak constraints in four-dimensional variational data assimilation
Published in Meteorologische Zeitschrift (Berlin, Germany : 1992) (17-12-2007)“…The formulation of four-dimensional variational data assimilation allows the incorporation of constraints into the cost function which need only be weakly…”
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