2023

Shataer, Shaerdan, Lawless, Amos S. and Nichols, Nancy K. ORCID: https://orcid.org/0000-0003-1133-5220 (2023) Conditioning of hybrid variational data assimilation. Numerical Linear Algebra with Applications. e2534. ISSN 1099-1506 doi: https://doi.org/10.1002/nla.2534

Francis, Devon J., Fowler, Alison M. ORCID: https://orcid.org/0000-0003-3650-3948, Lawless, Amos S., Eyre, John and Migliorini, Stefano (2023) The effective use of anchor observations in variational bias correction in the presence of model bias. Quarterly Journal of the Royal Meteorological Society. ISSN 1477-870X doi: https://doi.org/10.1002/qj.4482

2022

Tabeart, Jemima M., Dance, Sarah L. ORCID: https://orcid.org/0000-0003-1690-3338, Lawless, Amos S., Nichols, Nancy K. ORCID: https://orcid.org/0000-0003-1133-5220 and Waller, Joanne A. (2022) New bounds on the condition number of the Hessian of the preconditioned variational data assimilation problem. Numerical Linear Algebra with Applications, 29 (1). e2405. ISSN 1099-1506 doi: https://doi.org/10.1002/nla.2405

Leung, Tsz Yan ORCID: https://orcid.org/0000-0003-0056-284X, Lawless, Amos S., Nichols, Nancy K. ORCID: https://orcid.org/0000-0003-1133-5220, Lea, Daniel J. and Martin, Matthew J. (2022) The impact of hybrid oceanic data assimilation in a coupled model: a case study of a tropical cyclone. Quarterly Journal of the Royal Meteorological Society, 148 (746). pp. 2410-2430. ISSN 0035-9009 doi: https://doi.org/10.1002/qj.4309

2021

Dauzickaite, Ieva, Lawless, Amos S., Scott, Jennifer A. ORCID: https://orcid.org/0000-0003-2130-1091 and Leeuwen, Peter Jan (2021) On time-parallel preconditioning for the state formulation of incremental weak constraint 4D-Var. Quarterly Journal of the Royal Meteorological Society, 147 (740). pp. 3521-3529. ISSN 1477-870X doi: https://doi.org/10.1002/qj.4140

Daužickaitė, Ieva ORCID: https://orcid.org/0000-0002-1285-1764, Lawless, Amos S., Scott, Jennifer A. ORCID: https://orcid.org/0000-0003-2130-1091 and Van Leeuwen, Peter Jan ORCID: https://orcid.org/0000-0003-2325-5340 (2021) Randomised preconditioning for the forcing formulation of weak constraint 4D‐Var. Quarterly Journal of the Royal Meteorological Society, 147 (740). pp. 3719-3734. ISSN 1477-870X doi: https://doi.org/10.1002/qj.4151

Otkin, Jason A., Potthast, Roland W. E. and Lawless, Amos S. (2021) Nonlinear conditional model bias estimation for data assimilation. SIAM Journal on Applied Dynamical Systems, 20 (1). pp. 299-332. ISSN 1536-0040 doi: https://doi.org/10.1137/19M1294848

2020

Dauzickaite, Ieva, Lawless, Amos S., Scott, Jennifer A. and Van Leeuwen, Peter Jan (2020) Spectral estimates for saddle point matrices arising in weak constraint four-dimensional variational data assimilation. Numerical Linear Algebra with Applications, 27 (5). ISSN 1099-1506 doi: https://doi.org/10.1002/nla.2313

Smith, Polly J., Lawless, Amos S. and Nichols, Nancy K. (2020) The role of cross-domain error correlations in strongly coupled 4D-Var atmosphere-ocean data assimilation. Quarterly Journal of the Royal Meteorological Society, 146 (730). pp. 2450-2465. ISSN 1477-870X doi: https://doi.org/10.1002/qj.3802

Tabeart, J. M., Dance, S.L., Lawless, A.S., Migliorini, S., Nichols, N. K., Smith, F. and Waller, J. A. (2020) The impact of using reconditioned correlated observation error covariance matrices in the Met office 1D-Var system. Quarterly Journal of the Royal Meteorological Society, 146 (728). pp. 1372-1390. ISSN 1477-870X doi: https://doi.org/10.1002/qj.3741

Owens, Mathew J., Lang, Matthew, Riley, Pete, Lockwood, Mike and Lawless, Amos S. (2020) Quantifying the latitudinal representivity of in situ solar wind observations. Journal of Space Weather and Space Climate, 10. 8. ISSN 2115-7251 doi: https://doi.org/10.1051/swsc/2020009

Tabeart, J. M., Dance, S. L., Lawless, A. S., Nichols, N. K. and Waller, J. A. (2020) Improving the condition number of estimated covariance matrices. Tellus A: Dynamic Meteorology & Oceanography, 72 (1). pp. 1-19. ISSN 1600-0870 doi: https://doi.org/10.1080/16000870.2019.1696646

Pinnington, Ewan, Quaife, Tristan, Lawless, Amos, Williams, Karina, Arkebauer, Tim and Scoby, Dave (2020) The land variational ensemble data assimilation framework: LaVEnDAR v1.0.0. Geoscientific Model Development, 13. pp. 55-69. ISSN 1991-9603 doi: https://doi.org/10.5194/gmd-13-55-2020

2019

Sgura, Ivonne, Lawless, Amos S. and Bozzini, Benedetto (2019) Parameter estimation for a morphochemical reaction-diffusion model of electrochemical pattern formation. Inverse Problems in Science and Engineering, 27 (5). pp. 618-647. ISSN 1741-5985 doi: https://doi.org/10.1080/17415977.2018.1490278

2018

Tabeart, Jemima M., Dance, Sarah L., Haben, Stephen A., Lawless, Amos S., Nichols, Nancy K. and Waller, Joanne A. (2018) The conditioning of least squares problems in variational data assimilation. Numerical Linear Algebra with Applications, 25 (5). e2165. ISSN 1099-1506 doi: https://doi.org/10.1002/nla.2165

Smith, Polly J., Lawless, Amos S. and Nichols, Nancy K. (2018) Treating sample covariances for use in strongly coupled atmosphere-ocean data assimilation. Geophysical Research Letters, 45 (1). pp. 445-454. ISSN 0094-8276 doi: https://doi.org/10.1002/2017gl075534

Otkin, J. A., Potthast, Roland and Lawless, Amos S. (2018) Nonlinear bias correction for satellite data assimilation using Taylor series polynomials. Monthly Weather Review, 146 (1). pp. 263-285. ISSN 0027-0644 doi: https://doi.org/10.1175/mwr-d-17-0171.1

2017

Smith, Polly J., Lawless, Amos S. and Nichols, Nancy K. (2017) Estimating forecast error covariances for strongly coupled atmosphere-ocean 4D-Var data assimilation. Monthly Weather Review, 145 (10). pp. 4011-4035. ISSN 0027-0644 doi: https://doi.org/10.1175/MWR-D-16-0284.1

Howes, K. E., Fowler, Alison M. and Lawless, A. S. (2017) Accounting for model error in strong-constraint 4DVar data assimilation. Quarterly Journal of the Royal Meteorological Society, 143 (704). pp. 1227-1240. ISSN 1477-870X doi: https://doi.org/10.1002/qj.2996

Pinnington, Ewan M., Casella, Eric, Dance, Sarah L., Lawless, Amos S., Morison, James I. L., Nichols, Nancy K., Wilkinson, Matthew and Quaife, Tristan L. (2017) Understanding the effect of disturbance from selective felling on the carbon dynamics of a managed woodland by combining observations with model predictions. JGR-Biogeosciences, 122 (4). pp. 886-902. ISSN 2169-8961 doi: https://doi.org/10.1002/2017JG003760

2016

Pinnington, Ewan M., Casella, Eric, Dance, Sarah L., Lawless, Amos S., Morison, James I. L., Nichols, Nancy K., Wilkinson, Matthew and Quaife, Tristan L. (2016) Investigating the role of prior and observation error correlations in improving a model forecast of forest carbon balance using Four Dimensional Variational data assimilation. Agricultural and Forest Meteorology, 228-229. pp. 299-314. ISSN 0168-1923 doi: https://doi.org/10.1016/j.agrformet.2016.07.006

Fowler, Alison M. and Lawless, Amos S. (2016) An idealized study of coupled atmosphere-ocean 4D-Var in the presence of model error. Monthly Weather Review, 144 (10). pp. 4007-4030. ISSN 0027-0644 doi: https://doi.org/10.1175/MWR-D-15-0420.1

2015

Smith, Polly J., Fowler, Alison M. and Lawless, Amos S. (2015) Exploring strategies for coupled 4D-Var data assimilation using an idealised atmosphere-ocean model. Tellus A, 67. 27025. ISSN 1600-0870 doi: https://doi.org/10.3402/tellusa.v67.27025

2014

Waller, Joanne A., Dance, Sarah L., Lawless, Amos S. and Nichols, Nancy K. (2014) Estimating correlated observation error statistics using an ensemble transform Kalman filter. Tellus A, 66. 23294. ISSN 1600-0870 doi: https://doi.org/10.3402/tellusa.v66.23294

Waller, Joanne A., Dance, Sarah L., Lawless, Amos S., Nichols, Nancy K. and Eyre, J. R. (2014) Representativity error for temperature and humidity using the Met Office high-resolution model. Quarterly Journal of the Royal Meteorological Society, 140 (681). pp. 1189-1197. ISSN 1477-870X doi: https://doi.org/10.1002/qj.2207

Haben, S. A., Lawless, A. S. and Nichols, N. K., (2014) Conditioning and preconditioning of the optimal state estimation problem. Mathematics Preprint Series. 2014-08. Technical Report. Dept of Mathematics & Statistics, University of Reading pp21.

2013

Lawless, Amos (2013) Variational data assimilation for very large environmental problems. In: Cullen, M., Freitag, M.A., Kindermann, S. and Scheichl, R. (eds.) Large Scale Inverse Problems: Computational Methods and Applications in the Earth Sciences. Radon Series on Computational and Applied Mathematics, 2 (13). De Gruyter, Berlin, pp. 55-90. ISBN 9783110282269

Smith, P. J., Thornhill, G. D., Dance, S. L., Lawless, A. S., Mason, D. C. and Nichols, N. K. (2013) Data assimilation for state and parameter estimation: application to morphodynamic modelling. Quarterly Journal of the Royal Meteorological Society, 139 (671 Part B). pp. 314-327. ISSN 1477-870X doi: https://doi.org/10.1002/qj.1944

Moodey, Alexander J. F., Lawless, Amos S., Potthast, Roland W. E. and Van Leeuwen, Peter Jan (2013) Nonlinear error dynamics for cycled data assimilation methods. Inverse Problems, 29 (2). 025002. ISSN 0266-5611 doi: https://doi.org/10.1088/0266-5611/29/2/025002

2012

Thornhill, Gill D., Mason, David C., Dance, Sarah L., Lawless, Amos S., Nichols, Nancy K. and Forbes, Heather R. (2012) Integration of a 3D Variational data assimilation scheme with a coastal area morphodynamic model of Morecambe Bay. Coastal Engineering, 69. pp. 82-96. ISSN 0378-3839 doi: https://doi.org/10.1016/j.coastaleng.2012.05.010

2011

Haben, Stephen A., Lawless, Amos S. and Nichols, Nancy K. (2011) Conditioning of incremental variational data assimilation, with application to the Met Office system. Tellus Series A: Dynamic Meteorology and Oceanography, 63 (4). pp. 782-792. ISSN 1600-0870 doi: https://doi.org/10.1111/j.1600-0870.2011.00527.x

Haben, Stephen A., Lawless, Amos S. and Nichols, Nancy K. (2011) Conditioning and preconditioning of the variational data assimilation problem. Computers & Fluids, 46 (1). pp. 252-256. ISSN 0045-7930 doi: https://doi.org/10.1016/j.compfluid.2010.11.025

Baxter, G.M., Dance, S.L., Lawless, A.S. and Nichols, N.K. (2011) Four-dimensional variational data assimilation for high resolution nested models. Computers & Fluids, 46 (1). pp. 137-141. ISSN 0045-7930 doi: https://doi.org/10.1016/j.compfluid.2011.01.023

Boess, Caroline, Lawless, Amos S., Nichols, Nancy K. and Bunse-Gerstner, A. (2011) State estimation using model order reduction for unstable systems. Computers & Fluids, 46 (1). pp. 155-160. ISSN 0045-7930 doi: https://doi.org/10.1016/j.compfluid.2010.11.033

Pocock, Joanne A., Dance, Sarah L. and Lawless, Amos S. (2011) State estimation using the particle filter with mode tracking. Computers & Fluids, 46 (1). pp. 392-397. ISSN 0045-7930 doi: https://doi.org/10.1016/j.compfluid.2011.02.009

Katz, D., Lawless, Amos S., Nichols, Nancy K., Cullen, M. J. P. and Bannister, Ross N. (2011) Correlations of control variables in variational data assimilation. Quarterly Journal of the Royal Meteorological Society, 137 (656). pp. 620-630. ISSN 1477-870X doi: https://doi.org/10.1002/qj.798 (Part A)

2010

Dance, Sarah Louise, Baines, Michael John, Lawless, Amos Stephen, Mason, David Cecil, Nichols, Nancy Kay, Scott, Tania Ruth, Sweby, Peter Kenneth, Smith, Polly and Thornhill, Gillian Denise (2010) Use of data assimilation methods in coastal sediment models. In: Flood Risk from Extreme Events (FREE) Final Science Meeting, 20 October, London. (Unpublished)

Lawless, A. S. (2010) A note on the analysis error associated with 3D-FGAT. Quarterly Journal of the Royal Meteorological Society, 136 (649). pp. 1094-1098. ISSN 1477-870X doi: https://doi.org/10.1002/qj.619

2009

Nichols, Nancy Kay, Baxter, Gillian, Dance, Sarah Louise and Lawless, Amos Stephen (2009) Issues in high resolution data assimilation. In: The 8th International Workshop on Adjoint Model Applications in Dynamic Meteorology, May 2009, Tannersville, PA, USA.

Thornhill, Gillian Denise, Scott, Tania Ruth, Smith , P.J., Dance, Sarah Louise, Mason, David Cecil, Nichols, Nancy Kay, Baines, Michael John, Horsburgh, K.J., Sweby, Peter Kenneth and Lawless, Amos Stephen (2009) Progress on “Changing coastlines: data assimilation for morphodynamic prediction and predictability”. In: Third NERC FREE Conference, 10-11 September, Plymouth. (Unpublished)

2008

Bannister, Ross Noel, Katz, D., Cullen, M. J. P., Lawless, A. S. and Nichols, N. K. (2008) Modelling of forecast errors in geophysical fluid flows. International Journal for Numerical Methods in Fluids, 56 (8). pp. 1147-1153. ISSN 0271-2091 doi: https://doi.org/10.1002/fld.1618

Lawless, A.S., Nichols, N.K., Boess, C. and Bunse-Gerstner, A. (2008) Approximate Gauss-Newton Methods for optimal state estimation using reduced-order models. International Journal for Numerical Methods in Fluids, 56 (8). 1367 -1373. ISSN 0271-2091 doi: https://doi.org/10.1002/fld.1629

Scott, T. R., Smith, Polly J., Dance, S. L., Mason, D.C., Baines, M.J., Nichols, N.K., Horsburgh, K.J., Sweby, P.K. and Lawless, A.S. (2008) Data assimilation for morphodynamic prediction and predictability. In: Coastal Engineering 2008 Proceedings of the 31st International Conference. World Scientific, pp. 2386-2398. doi: https://doi.org/10.1142/9789814277426_0197

Lawless, A.S., Nichols, N.K., Boess, C. and Bunse-Gerstner, A. (2008) Using model reduction methods within incremental four-dimensional variational data assimilation. Monthly Weather Review, 136 (4). pp. 1511-1522. ISSN 0027-0644 doi: https://doi.org/10.1175/2007MWR2103.1

2007

Watkinson, L.R., Lawless, A.S., Nichols, N.K. and Roulstone, I. (2007) Weak constraints in four-dimensional variational data assimilation. Meteorologische Zeitschrift, 16 (6). pp. 767-776. doi: https://doi.org/10.1127/0941-2948/2007/0249

Gratton, S., Lawless, A.S. and Nichols, N.K. (2007) Approximate Gauss-Newton methods for nonlinear least squares problems. SIAM Journal on Optimization (SIOPT), 18 (1). pp. 106-132. ISSN 1052-6234 doi: https://doi.org/10.1137/050624935

Lawless, A. S., Nichols, N. K., Boess, C. and Bunse-Gerstner, A. (2007) Approximate Gauss-Newton methods using reduced order models. In: Proceedings of the Ninth International ICFD Conference on Numerical Methods for Fluid Dynamics, March 26 – 29, 2007. ICFD, Reading.

Bannister, R. N., Katz, D., Cullen, M. J. P., Lawless, A. S. and Nichols, N. K. (2007) Modelling of forecast errors in geophysical fluid flows. In: Proceedings of the Ninth International ICFD Conference on Numerical Methods for Fluid Dynamics, March 26 – 29, 2007. ICFD, Reading.

Scott, Tania Ruth, Smith, Polly J., Dance, S.L., Mason, D.C., Nichols, N.K., Baines, M.J., Horsburgh, K., Sweby, P K and Lawless, A.S. (2007) Progress on Changing coastlines: data assimilation for morphodynamic prediction and predictability. In: 2nd NERC Conference on Flood Risk from Extreme Events (FREE). (Unpublished)

Baxter, G. M., Dance, S. L., Lawless, A. S., Nichols, N. K. and Ballard, S. P. (2007) Towards Multi-scale Data Assimilation for High Resolution Nested Models. In: Proceedings of the Ninth International ICFD Conference on Numerical Methods for Fluid Dynamics, March 26 – 29, 2007. ICFD, Reading.

2006

Lawless, A. S. and Nichols, N. K. (2006) Inner loop stopping criteria for incremental four-dimensional variational data assimilation. Monthly Weather Review, 134. pp. 3425-3435.

Lawless, Amos, Gratton, S and Nichols, Nancy (2006) An investigation of the convergence of incremental 4D-Var. In: The Fourth WMO International Symposium on Assimilation of Observations in Meteorology and Oceanography, 2006.

2005

Lawless, A. S., Gratton, S. and Nichols, N. K. (2005) Approximate iterative methods for variational data assimilation. International Journal For Numerical Methods In Fluids, 47 (10-11). pp. 1129-1135.

Watkinson, L. R., Lawless, A. S., Nichols, N. K. and Roulstone, I. (2005) Variational data assimilation for Hamiltonian problems. International Journal For Numerical Methods In Fluids, 47 (10-11). pp. 1361-1367.

Lawless, A. S., Gratton, S. and Nichols, N. K. (2005) An investigation of incremental 4D-Var using non-tangent linear models. Quarterly Journal of the Royal Meteorological Society, 131 (606). pp. 459-476. ISSN 1477-870X

2004

Lawless, A.S., Gratton, S. and Nichols, N. K. (2004) Approximate iterative methods for variational data assimilation. In: Proceedings of the ICFD International Conference on Numerical Methods for Fluid Dynamics, Oxford, University of Oxford.

Stanton, L.R., Lawless, A.S., Nichols, N. K. and Roulstone, I. (2004) Variational data assimilation for Hamiltonian problems. In: Proceedings of the ICFD International Conference on Numerical Methods for Fluid Dynamics, Oxford, University of Oxford.

2003

Lawless, A.S., Nichols, N.K. and Ballard, S.P. (2003) A comparison of two methods for developing the linearization of a shallow-water model. Quarterly Journal of the Royal Meteorological Society, 129 (589). pp. 1237-1254. ISSN 1477-870X doi: https://doi.org/10.1256/qj.02.75

Lawless, A.S. and Nichols, N.K. (2003) The convergence of incremental 4D-Var using non-tangent linear models. In: Cote, J. (ed.) Research activities in atmospheric and oceanic modelling. WMO CAS/JSG Working Group on Numerical Experimentation, 01-17 + 01-18.