CAS People

Isla Simpson, Scientist 2


Research


Isla Simpson is a Scientist 2 in the Climate Analysis Section of the Climate and Global Dynamics Division, studying large scale atmospheric dynamics and its representation in Global Climate Models. She works to understand dynamical mechanisms involved in the variability and change of the large scale atmospheric circulation and its impacts on regional climate and hydroclimate using a hierarchy of modelling approaches. The overall aim being to determine the extent which models can successfully capture the processes of relevance for the real atmosphere and to determine how they can be improved.

Publications


Submitted/In Press


Chen, R., Simpson, I. R., Deser, C., Wang, B., Model biases in the simulation of the springtime North Pacific ENSO teleconnection, Submitted to J. Clim.

Published


2020


Deser, C., Phillips, A. S., Simpson, I. R., Rosenbloom, N., Coleman, D., Lehner, F. and Pendergrass, A. G. (2020) Isolating the Evolving Contributions of Anthropogenic Aerosols and Greenhouse Gases: A New CESM1 Large Ensemble Community Resource, Article

Simpson, I. R., Bacmeister, J., Neale, R. B., Hannay, C., Gettelman, A., Garcia, R. R., Lauritzen, P. H., Marsh, D. R., Mills, M. J., Medeiros, B., Richter, J. H. (2020) An evaluation of the large scale atmospheric circulation and its variability in the CESM2 and other CMIP models, JGR Atmospheres, PDF

Seager, R., Liu, H., Kushnir, Y., Osborn, T. J., Simpson, I. R., Kelley, C. R. and Nakamura, J. (2020) Mechanisms of winter precipitation variability in the European-Meditteranean region associated with the North Atlantic Oscillation, J. Clim., Articla

Kim, H., Caron, J. M., Richter, J. H. and Simpson, I. R. (2020) The lack of QBO-MJO connection in CMIP6 models, 47, Article

Richter, J. H., Anstey, J., Butchart, N., Kawatani, Y., Meehl, G., Osprey, S., Simpson, I. R. (2020) Progress in simulating the Quasi-biennial Oscillation in CMIP models, JGR atmospheres, 125 Article

Deser, C., Lehner, F., Rodgers, K. B., Ault, T., Delworth, T. L., DiNezio, P. N., Fiore, A., Frankignoul, C., Fyfe, J. C., Horton, D. E., Kay, J. E., Knutti, R., Lovenduski, N. S., Marotzke, J., McKinnon, K. A., Minobe, S., Randerson, J., Screen, J. A., Simpson, I. R., Ting, M. (2020) Insights from Earth system model initial-condition large ensembles and future prospects, Nat. Clim. Change, 10, 277-286 Article

Ayarzaguena, B., Charlton-Perez, A. J., Butler, A. H., Hitchcock, P., Simpson, I. R., Polvani, L. M., Butchart, N., Gerber, E. P., Gray, L., Hassler, B., Lin, P., Lott, F., Manzini, E., Mizuta, R., Orbe, C., Osprey, S., Saint-Martin, D., Sigmond M., Taguchi, M., Volodin, E. M., Watanabe, S. (2020) Uncertainty in the response of sudden stratospheric warmings and stratosphere-troposphere coupling to quadrupled CO2 concentrations in CMIP6 models, JGR atmospheres doi: 10.1029/2019JD032345 Article

Maycock, A. C., Masukwedza, G. I. T., Hitchcock, P. and Simpson, I. R., (2020) A regime perspective on the North Atlantic eddy-driven jet response to sudden stratospheric warmings, J. Clim., https://doi.org/10.1175/JCLI-D-19-0702.1 Article

Michel, C., Li, C., Simpson, I. R., Bethke, I., King, M. P. and Sobolowski, S., (2020) The change in the ENSO teleconnection under a low global warming scenario and the uncertainty due to internal variability, J. Clim., https://doi.org/10.1175/JCLI-D-19-0730.1 Article

Domiesen, D. I.V., Butler, A. H., Charlton-Perez, A. J., Ayarzaguena, B., Baldwin, M. P., Dunn-Sigouin, E., Furtado, J. C., Garfinkel, C. I., Hitchcock, P., Karpechko, A. Y., Kim, H., Knight, J., Lang, A. L., Lim, E.-P., Marshall, A., Roff, G., Schwartz, C., Simpson, I. R., Son, S.-W., Taguchi, M. (2020), The role of the stratosphere in subseasonal to seasonal prediction. Part 1: predictability of the stratosphere, JGR atmospheres, https://doi.org/10.1029/2019JD030920 Article

Domiesen, D. I.V., Butler, A. H., Charlton-Perez, A. J., Ayarzaguena, B., Baldwin, M. P., Dunn-Sigouin, E., Furtado, J. C., Garfinkel, C. I., Hitchcock, P., Karpechko, A. Y., Kim, H., Knight, J., Lang, A. L., Lim, E.-P., Marshall, A., Roff, G., Schwartz, C., Simpson, I. R., Son, S.-W., Taguchi, M. (2020), The role of the stratosphere in subseasonal to seasonal prediction. Part 2: predictability arising from stratosphere-troposphere coupling, JGR Atmospheres https://doi.org/10.1029/2019JD030923 Article

Richter, J. H., Butchart, N., Kawatani, Y., Bushell, A. C., Holt, L., Serva, F., Anstey, J., Simpson, I. R., Osprey, S., Hamilton, K., Braesicke, P., Cagnazzo, C., Chen, Chih-Chieh, Garcia, R. R., Gray, L. J., Kerzenmacher, T., Lott, F., McLandress, C., Naoe, H., Scinocca, J., Stockdale, T. N., Versick, S., Watanabe, S., Yoshida, K., Yukimoto, S. (2020), Response of the quasi-biennial oscillation to a warming climate in global climate models, QJRMS, doi:10.1002/qj.3749 Article

2019


Wu, Y., Simpson, I. R. and Seager, R. (2019) Inter-model spread in the Northern Hemisphere stratospheric polar vortex response to climate change in the CMIP5 models, Geophys. Res. Lett., 46, 13290-13298 Article

Jiang, J., MacMartin, D. G., Simpson, I. R., Kravitz, B., Cheng, W., Visioni, D., Tilmes, S., Richter, J. H., Mills, M. J. (2019) Stratospheric Sulfate Geoengineering Could Alter the High-Latitude Seasonal Cycle, Geophys. Res. Lett., 46, 14153-14163 doi:10.1029/2019GL085758 Article

Cheng, W., MacMartin, D. G., Dagon, K., Kravitz, B., Tilmes, S., Richter, J. H., Mills, M. J.,Simpson, I. R., Soil moisture and other hydrological changes in a stratospheric aerosol geoengineering large ensemble. JGR Atmospheres, 124, 12773-12793 doi:10.1029/2018JD030237 Article

Merrifield, A. L. and Simpson, I. R. and McKinnon, K. A. and Sippel, S. and Xie, S.-P. and Deser, C. Local and non-local land surface influence in European heatwave initial condition ensembles, Geophys. Res. Lett., 46, doi:10.1029/2019GL083945 Article

Simpson, I. R., Tilmes, S., Richter, J. H., Kravitz, B., MacMartin, D. G., Mills, M. J., Fasullo, J. T. and Pendergrass, A. G. The regional hydroclimate response to stratospheric sulfate geoengineering and the role of stratospheric heating, JGR Atmospheres, 124, 12587-12616, doi:10.1029/2019JD031093 PDF

Gettelman, A., Mills, M. J., Kinnison, D. E., Garcia, R. R., Smith, A. K., Marsh, D. R., Tilmes, S., Vitt, F., Bardeed, C. G., McInerny, J., Liu, H.-L., Solomon, S. C., Polvani, L. M., Emmons, L. K., Lamarque, J.-F., Richter, J. H., Glanville, A. S., Bacmeister, J. T., Phillips, A. S., Neale, R. B., Simpson, I. R., DuVivier, A. K., Hodzic, A. and Randel, W. J., The Whole Atmosphere Community Climate Model Version 6 (WACCM6), JGR-Atmospheres, 124, doi:10.1029/2019JD030943 Article.

Pendergrasss, A. G., Coleman, D. B., Deser, C., Lehner, F., Rosenbloom, N. and Simpson, I. R. Nonlinear Response of Extreme Precipitation to Warming in CESM1, Geophys. Res. Lett., 46 ,10,551-10,560 PDF

Butler, A. H., Charlton-Perez, A., Domiesen, D. I. V., Simpson, I. R. and Sjoberg, J., Predictatbility of Northern Hemisphere final stratospheric warmings and their surface impacts, Geophys. Res. Lett., 46, 10578-10588 PDF

Simpson, I. R., Yeager, S. G., McKinnon, K. A. and Deser, C. (2019) Decadal predictability of late winter precipitation in western Europe through an ocean-jet stream connection, Nature Geoscience, 12, 613-619 Article

Gettelman, A., Truesdale, J. E., Bacmeister, J. T., Caldwell, P. M., Neale, R. B., Bogenschutz, P. A. and Simpson, I. R. (2018) The Single Column Atmosphere Model version 6 (SCAM6): Not a Scam but a Tool for Model Evaluation and Development, JAMES, 11, 1381-1401i PDF

Kravitz, B., MacMartin, D. G., Tilmes, S., Richter, J. H., Mills, M. J., Cheng, W., Dagon, K, Glanville, A. S., Lamarque, J.-F., Simpson, I. R., Tribbia, J. J. and Vitt, F. (2019), Comparing surface and stratospheric impacts of geoengineering with different SO2 injection strategies, JGR-Atmospheres, 124, 7900-7918 PDF

Seager, R., Osborn, T. J., Kushnir, Y., Simpson, I. R., Nakamura, J. and Liu, H. (2019) Climate variability and change of Mediterranean-type climates, J. Clim., 32, 2887-2915 Article

Grise, K. M., Davis, S. M., Simpson, I. R., Waugh, D. W., Fu, Q., Allen, R. J., Rosenlof, K. H., Ummenhofer, C. C., Karnauskas, K. B., Maycock, A. C., Quan, X.-W., Birner, T., Staten, P. W. (2019), Recent Tropical Expansion: Natural Variability or Forced Response?, J. Clim., 32, 1551-1571 PDF

Simpson, I. R., Hitchcock, P, Seager, R, Wu, Y (2019) The role of the stratosphere in future mid-latitude climate projections, USClivar Variations, 17 (1) 33-39, doi:10.5065/q3jb-9642 PDF

2018


Eyring, V., and co-authors (2018) Taking climate model evaluation to the next level, Nat. Clim. Change, doi=10.1038/s41558-018-0355-y Article

Tilmes, S., Richter, J. H., Kravitz, B., MacMartin, D. G., Mills, M. J., Simpson, I. R., Glanville, A. S., Fasullo, J., Phillips, A. S., Lamarque, J.-F., Tribbia, J., Edwards, J., Mickelson, S., Ghosh, S. (2018) CESM1(WACCM) Stratospheric Aerosol Geoengineering Large Ensemble (GLENS) Project, Bull. Amer. Met. Soc., 99, 2361-2371, PDF

Fasullo, J. T., Tilmes, S., Richter, J. H., Kravitz, B., MacMartin, D. G., Mills, M. J. and Simpson, I. R. (2018) Persistent polar ocean warming in a strategically geoengineered climate, Nat. Geosc., article

Adam, O., Grise, K. M., Staten, P., Simpson, I. R., Davis, S. M., Davis, N. A., Waugh, D. W. and Birner, T. (2018) : The TropD software package: Standardized methods for calculating Tropical Width Diagnostics, Geosci. Model Dev., 11, 4339--4357 PDF

Simpson, I. R., Deser, C., McKinnon, K. A. and Barnes, E. A. (2018): Modelled and observed multidecadal variability in the North Atlantic jet stream and its connection to sea surface temperatures (2018), J. Clim., 31, 8313-8338, PDF

Zhang, P., Wu, Y., Simpson, I. R., Smith, K. L., Zhang, X., De, B. and Callaghan, P. (2018): A stratospheric pathway linking a colder Siberia to Barents-Kara sea ice loss, Science Avances, 4, doi: 10.1126/sciadv.aat6025 Article

Simpson, I. R. (2018): Natural variability in the width of the tropics, USClivar Variations, 16 (2), 14-20, doi:10.5065/D69Z92QF PDF

Waugh, D. W., Grise, K. M., Seviour, W. J. M., Davis, S. M., Davis, N., Adam, O., Son, W.-W., Simpson, I. R., Staten, P. W., Maycock, A. C., Ummenhofer, C. C., Birner, T. and Ming, A. (2018) Revisiting the Relationship among Metrics of Tropical Expansion, J. Clim., 31, 7565--7581 PDF

Richter, J. H., Tilmes, S., Glanville, A., Kravitz, B., MacMartin, D. G., Mills, M. J., Simpson, I. R., Vitt, F., Tribbia, J. J., Lamarque, J.-F. (2018) Stratospheric response in the first geoengineering simulation meeting multiple surface climate objectives, J. Geophys. Res.: Atm., 123, doi:10.1029/2018JD028285PDF

Deser, C., Simpson, I. R., Phillips, A. S. and McKinnon, K. A. (2018) How well do we know ENSO's climate impacts over North America, and how do we evaluate models accordingly? J. Clim., 31, 4991--5041 PDF

Simpson, I. R., Hitchcock, P., Seager, R., Wu, Y. and Callaghan, P. (2018) The downward influence of uncertainty in the Northern Hemisphere stratospheric polar vortex response to climate change, J. Clim., 31, 6371--6391 PDF

Lehner, F., Deser, C., Simpson, I. R., Terray, L. (2018) Attributing the U.S. Southwests recent shift to drier conditions, GRL, 45, 6251-6261 PDF

Simpson, I. R., Bacmeister, J. T., Sandu, I. and Rodwell, M. J. (2018) Why do modelled and observed surface wind stress climatologies differ in the trade wind regions?, J. Clim., 31, 491--513 PDF

2017


Barnes, E. A. and Simpson, I. R. (2017) Seasonal sensitivity of the Northern Hemisphere jet-streams to Arctic temperatures on subseasonal timescales, J. Clim, 30, 10117--10137 PDF

Deser, C., Simpson, I. R., McKinnon, K. A. and Phillips, A. S. (2017) , The Northern Hemisphere extra-tropical atmospheric circulation response to ENSO: How well do we know it and how do we evaluate models accordingly? J. Clim, 30, 5059--5082 PDF

Polvani, L. M., Clement, A. C., Medeiros, B.. Benedict, J. J. and Simpson, I. R. (2017), When less is More: Opening the Door to Simpler Climate Modelst, EOS, 98, Article

2016


Hitchcock, P. and Simpson, I. R. (2016), Quantifying eddy feedbacks and forcings in the tropospheric response to stratospheric sudden warmings. J. Atmos. Sci., 73, 3641-3657 PDF.

Seager, R. and Simpson, I. R. (2016) Western boundary currents and climate change, J. Geophys. Res. Oceans, 121, doi:10.1002/2016JC012156. PDF.

Shaw, T. A., Baldwin, M., Barnes, E. A., Caballero, R., Garfinkel, C. I., Hwang, Y-T., Li, C., O'Gorman, P. A., Riviere, G., Simpson, I. R., and Voigt, A. (2016): Storm track processes and the opposing influences of climate change, Nature Geoscience, 9, 656-664 Article

Simpson, I. R. and Polvani, L. M. (2016) Revisiting the relationship between jet position, forced response and annular mode variability in the southern mid-latitudes. Geophys. Res. Lett., 43, 2896-2903 PDF. Supplementary material PDF.

Simpson, I. R. (2016) Climate change predicted to lengthen transatlantic travel times. Env. Res. Lett., 11, 031002. PDF (Perspective on Williams (2016) Env. Res. Lett., 11, 024008.)

Simpson, I. R., Seager, R., Ting, M. and Shaw, T. A. (2016) Causes of change in Northern Hemisphere winter meridional winds and regional hydroclimate, Nature Climate Change, 6, 65-70: Article

2015


Simpson, I. R., Seager, R., Shaw, T. A. and Ting, M. (2015) Mediterranean summer climate and the importance of Middle East Topography. J. Clim., 28 1977--1996: PDF

2014


Seager, R., Neelin, D., Simpson, I. R., Liu, H., Henderson, N., Shaw, T. A., Kushnir, Y., Ting, M. and Cook, B. (2014) Dynamical and thermodynamical causes of large-scale changes in the hydrological cycle of North America in response to global warming., J. Clim., 27, 7921--7948: PDF

Hitchcock, P. and Simpson, I. R. (2014) The Downward Influence of Stratospheric Sudden Warmings (2014) J. Atmos. Sci., 71, 3856--3876: PDF

Seager, R., Liu, H., Henderson, N., Simpson, I. R., Kelley, C., Shaw, T. A., Kushner, Y. and Ting, M. (2014) Causes of increasing aridification of the Mediterranean region in response to rising greenhouse gases (2014), J. Clim., 27, 4655--4676: PDF

Simpson, I. R., Shaw, T. A. and Seager, R. (2014) A diagnosis of the seasonally and longitudinally varying mid-latitude circulation response to global warming (2014) J. Atmos. Sci., 71, 2489--2515: PDF

2013


Simpson, I. R., Shepherd, T. G., Hitchcock, P and Scinocca, J. F. (2013) Southern Annular Mode dynamics in observations and models, part 2: eddy feedbacks. J. Clim., 26, 5220--5241: PDF

Simpson, I. R., Hitchcock, P., Shepherd, T. G. and Scinocca, J. F. (2013) Southern Annular Mode dynamics in observations and models, part 1: the influence of climatological zonal wind biases in a Comprehensive GCM. J. Clim., 26, 3953-3967: PDF

2012


Simpson I. R., Blackburn, M. and Haigh, J. D. (2012) A mechanism for the effect of tropospheric jet structure on the annular mode-like response to stratospheric forcing. J. Atmos. Sci., 69, 2152-2170: PDF

2011


Simpson I. R., Hitchcock, P., Shepherd, T. G. and Scinocca, J. F. (2011) Stratospheric variability and tropospheric annular mode timescales. Geophysical Research Letters, 38, L20806, doi:10.1029/2011GL049304: PDF

Simpson I. R., Shepherd, T. G., Sigmond, M. (2011) Dynamics of the lower stratospheric circulation response to ENSO. Journal of the Atmospheric Sciences, 68, 2537-2556: PDF

2010


Simpson I. R., Blackburn M., Haigh J. D. and Sparrow, S. N. (2010) The impact of the state of the troposphere on the response to stratospheric heating in a simplified GCM. Journal of Climate, 23, 6166-6185: PDF

2009


Simpson I. R., Blackburn M. and Haigh J. D. (2009) The role of eddies in driving the tropospheric response to stratospheric heating perturbations. Journal of the Atmospheric Sciences, 66, 1347-1365: PDF

PHD thesis - Solar influence on stratosphere-troposphere dynamical coupling: PDF

CGD People

Isla Simpson, Scientist 2