Irina Sandu

Senior Scientist
Research Department, Earth System Modelling Section, Physical Processes Group

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Irina joined ECMWF in 2010, and is now leading the Physical Processes Team.  Her research has so far covered boundary layer clouds and the factors controlling their distribution, aerosol-cloud interactions,  turbulent diffusion in stable conditions,  orographic drag  and land-atmosphere coupling.  Irina used a whole spectrum of models  (from idealized theoretical models, to Large Eddy, meso-scale and global NWP models), but also a wide range of datasets (in situ observations, satellite data and reanalysis) to address questions ranging from process understanding to aspects of subgrid parameterizations and model evaluation. 

At ECMWF, Irina's work aims at improving the representation both stable and cloudy boundary layers in the Integrated Forecasting System, and at understanding the impact of surface drag on the large scale atmospheric circulation. In recent years, Irina played an instrumental role in reviving the interest of the international community for the drag processes, and the orographic drag in particular, by highlighting their importance for the large-scale circulation and the uncertainties related to their representation in models. Irina is also now coordinating polar prediction related activities at ECMWF, particularly in the context of the ongoing WMO Year of Polar Prediction and the H2020 project APPLICATE. 

Professional interests: 
  • improving the representation of physical processes in NWP and climate models
  • momentum transport and drag processes, and more particularly orographic drag
  • boundary layers and boundary layer clouds
  • polar prediction 
Career background: 

Irina got a Phd from Meteo-France and Universite Paul Sabatier, Toulouse (2007). Her PhD research based on Large-Eddy Simulations helped demonstrating that aerosol-cloud interactions are far more complex than initially thought and that the current parametrizations used in climate models are inadequate. 

Irina then spent a couple of years as an Alexander von Humboldt post doctoral fellow at the Max Planck Institute for Meteorology in Hamburg (2008-2010).  Irina used a combination of observations, reanalysis and Large-Eddy Simulations to study the controlling factors of the stratocumulus to cumulus transitions, one of the most proeminent and difficult to model characteristics of marine boundary layer clouds. Based on this work, Irina proposed, and led, an intercomparison exercise for single column models and Large-Eddy Simulations in the framework of the Global Atmospheric System Studies (GASS) of GEWEX.

At ECMWF,  Irina's most notable achievements include various improvement of low-level winds, which were subject to some of the most longstading errors of the ECWMF forecasts, and a few studies demonstrating the impacts of the uncertainties in the representation of orographic drag in models on the Northern Hemisphere winter circulation at both NWP and climate time scales.

External recognitions: 
  • WCRP/WWRP international prize for model development
  • member of the WMO Polar Prediction Project (PPP) Steering Group
  • member of the GEWEX Global Atmospheric System Studies (GASS) panel
  • member of the scientific advisory committee of Meteo-France
  • external reviewer of the NERC/MetOffice PARACON project

Peer-reviewed publications

  • van Niekerk, A., Sandu, I., & Vosper, S. (2018). The circulation response to resolved versus parametrized orographic drag over complex mountain terrains, Journal of Advances in Modeling Earth Systems, 10, 2527–2547.

  • IR Simpson, JT Bacmeister, I Sandu, MJ Rodwell, 2018, Why Do Modeled and Observed Surface Wind Stress Climatologies Differ in the Trade Wind Regions?,  J. Clim.,  2018, 31 (2), 491-513

  • RAJ Neggers, AS Ackerman, et al, 2017, Single‐Column Model Simulations of Subtropical Marine Boundary‐Layer Cloud Transitions Under Weakening Inversions, J. of Adv. in Model. Earth Syst.

  • S. Bony, B Stevens, F Ament et al., 2017, EUREC4A: A field campaign to elucidate the couplings between clouds, convection and circulation, Surveys in Geophysics, 1-40

  • M. Leutbecher, SJ Lock et al, 2017, Stochastic representations of model uncertainties at ECMWF: State of the art and future vision, QJRMS

  • P Ollinaho, SJ Lock et al., 2017, Towards process‐level representation of model uncertainties: stochastically perturbed parametrizations in the ECMWF ensemble, QJRMS, 143 (702), 408-422

  • Pithan, F., A. Ackerman, W. M. Angevine, K. Hartung, L. Ickes, M. Kelley, B. Medeiros, I. Sandu, G.-J. Steeneveld, M. Sterk, G. Svensson, P. A. Vaillancourt, A. Zadra , 2016, Strengths and biases of models in representing the Arctic winter boundary layer: the Larcform 1 single column model intercomparison,  J. Adv. Model. Earth Syst.,  8 (3), 1345-1357

  • L. Schlemmer, P. Bechtold, I. Sandu, M. Ahlgrimm, 2017, Uncertainties related to the representation of momentum transport in shallow convection, J. of Adv. in Model. Earth Syst.

  • De Roode, S. R, I. Sandu, J. J. van der Dussen, A. S. Ackerman, P. Blossey, D. Jarecka, A. Lock, A. P. Siebesma, B. Stevens, 2016, Shallow cumulus cloud control on the stratocumulus lifetime: LES results of EUCLIPSE/GASS Lagrangian stratocumulus transitions,  J. Atmos. Sci., 73 (6), 2485-2508

  • F Pithan, TG Shepherd, G Zappa, I Sandu, 2016, Climate model biases in jet streams, blocking and storm tracks resulting from missing orographic drag, Geophysical Research Letters 43 (13), 7231-7240

  • Sandu, I. , P. Bechtold, A. Beljaars, A. Bozzo, F. Pithan, T.G. Shepherd and A. Zadra, 2016, Impacts of parameterized orographic drag on the Northern Hemisphere winter circulation, J. Adv. Model. Earth Syst., 12/2015, DOI:10.1002/2015MS000564

  • I. F. Trigo, S. Boussetta, P. Viterbo, G. Balsamo, A. Beljaars, I. Sandu, 2015, Comparison of model land skin temperature with remotely sensed estimates and 3 assessment of surface-atmosphere coupling,J. Geophys. Res. Atmos., 120, doi:10.1002/2015JD023812

  • Nuijens, L., B, Medeiros , I. Sandu , M. Ahlgrimm, 2015, Observed and modeled patterns of co-variability between low-level cloudiness and the structure of the trade-wind layer, J. Adv. Model. Earth Syst., 10/2015; DOI:10.1002/2015MS000483

  • Nuijens, L., B, Medeiros , I. Sandu , M. Ahlgrimm, 2015, The behavior of trade-wind cloudiness in observa- tions and models: the major cloud components and their variability, J. Adv. Model. Earth Syst., 7, 600-616, doi: 10.1002/2014MS000390

  • Albergel, C., E. Dutra, J. Munoz-Sabater, T. Haiden, G. Balsamo, A. Beljaars, L. Isaksen, P. de Rosnay, I. Sandu, N. Wedi, 2014, Soil temperature at ECMWF: an assessment using ground based observations, J. Geophys. Res. Atm., DOI: 10.1002/2014JD022505

  • Bozzo, A., R. Pincus, I. Sandu, J.J Morcrette, 2014, Impact of a spectral sampling technique for radiation on ECMWF weather forecasts, J. Adv. Model. Earth Syst., 6(4), doi:10.1002/2014MS000386

  • Sandu, I., A. Beljaars, P Bechtold, T Mauritsen, G Balsamo, 2013, Why is it so difficult to represent stably stratified conditions in numerical weather prediction (NWP) models?, J. Adv. Model. Earth Syst., 5, doi:10.1002/jame.20013.

  • van der Dussen, J. J., S. R. de Roode, A. S. Ackerman, P. N. Blossey, C. S. Bretherton, M. J. Kurowski, A. P. Lock, R. A. J. Neggers, I. Sandu, and A. P. Siebesma, 2013, The GASS/EUCLIPSE model intercomparison of the stratocumulus transition as observed during ASTEX: LES results, J. Adv. Model. Earth Syst., 5, 483-499, doi:10.1002/jame.20033.

  • Zhang, M., et al. (2013), CGILS: Results from the first phase of an international project to understand the physical mechanisms of low cloud feedbacks in single column models,J. Adv. Model. Earth Syst., 5, 826842, doi:10.1002/2013MS000246.

  • Sandu, I. and B. Stevens , 2011, On the factors modulating the stratocumulus to cumulus transitions, J. Atmos. Sci. 68 (9), 1865-1881

  • Sandu, I., B. Stevens and R. Pincus , 2010, On the transitions in marine boundary layer cloudiness, Atmos. Chem. Phys., 10, 2377-2391

  • Sandu, I., J.L. Brenguier, O. Thouron and B. Stevens, 2009, How important is the vertical structure for the representation of aerosol impacts on the diurnal cycle of marine stratocumulus?, Atmos. Chem. and Phys., 9, 4039-4052

  • Sandu, I., J.L. Brenguier, O. Geoffroy, O. Thouron and V. Masson, 2008, Aerosols impacts on the diurnal cycle of marine stratocumulus, J. Atmos. Sci., 65, 2705-2718

  • Geoffroy O., J-L. Brenguier and I. Sandu, 2008, Large scale relationships between drizzle rate, liquid water path and droplet concentration in stratocumulus clouds, Atmos. Chem. Phys., 8, 4641-4654

  • Sandu, I., P. Tulet and J.L. Brenguier, 2005, Parameterization of the cloud droplet single scattering albedo based on aerosol chemical composition for LES modeling of boundary layer clouds, Geophys. Res. Lett. , 32, L19814, doi:10.1029/2005GL023994

  • Sandu, I., F. Bompay and S. Stefan, Validation of atmospheric dispersion models using ETEX data, Inter- national Journal of Environment and Pollution, Vol 19, No 4, pp 367-389, 2003. 


ECMWF Publications

  • I. Sandu, A. Zadra and N. Wedi, On the impact of orographic drag on forecast skill, 2016, ECMWF Newsletter, Winter 2016/2017

  • Sandu, I. and A. Zadra, 2016: Experts discuss role of drag processes in NWP, climate models. ECMWF Newsletter Issue 149, Autumn 2016.

  • Sandu, I, P. Bechtold, A. Beljaars, A. Bozzo, F. Pithan, T. Shepherd, A. Zadra, 2015, On the impacts of subgrid orographic drag on the North Hemisphere winter circulation, ECMWF Technical Memorandum, No. 763

  • E. Dutra, I. Sandu, G. Balsamo, A. Beljaars, H. Freville, E. Vignon, E. Brun, 2015, Understanding the ECMWF surface temperature biases over Antarctica, ECMWF Technical Memorandum, No. 762

  • I. Sandu, N. Wedi, A. Bozzo, P. Bechtold, A. Beljaars, M. Leutbecher, 2014, On the near surface temperature differences between HRES and CTL ENS forecasts, ECWMF Technical Report, RD14-315

  • I. Sandu, A. Beljaars, G. Balsamo, Improving the representation of stable boundary layers, 2014, ECMWF Newsletter, No. 138, Winter 2013/2014

  • G. Balsamo, A. Agusti-Panareda, C. Albergel, A. Beljaars, S. Boussetta, E. Dutra, T. Komori, S. Lang, J. Muoz-Sabater, F. Pappenberger, P. de Rosnay, I. Sandu, N. Wedi, A. Weisheimer, F. Wetterhall, E. Zsoter, 2014, Representing the Earth surfaces in the Integrated Forecasting System: Recent advances and future challenges, ECMWF Technical Memorandum, No. 729

  • Bechtold, P., I. Sandu, D. Klocke, N. Semane, M. Ahlgrimm, A. Beljaars, R. Forbes, M. Rodwell, 2014, The role of shallow convection in ECMWFs Integrated Forecasting System, ECMWF Technical Memorandum, No. 725

  • I. Sandu, A. Beljaars, G Balsamo, 2013, Revision of the turbulence closure in stable conditions, ororgaphic drag and land-atmosphere coupling in Cy40r1, ECMWF Technical Report, RD13-428

  • Bauer, P., A. Beljaars, M. Ahlgrimm, P. Bechtold, J.-R. Bidlot, M. Bonavita, A. Bozzo, R. Forbes, E. Holm, M. Leutbecher, P. Lopez, L. Magnusson, F. Prates, M. Rodwell, I. Sandu, A. Untch, F. Vitart, Model Cycle 38r2: Components and Performance, ECMWF Technical Memorandum, No. 704

  • Ahlgrimm, M., R. Forbes, I.Sandu, and P. Bechtold, 2012, Evaluating the ECMWF model’s clouds and radiation with ARM observations, Proceedings Workshop on Parametrization of Clouds and Precipitation, ECMWF, 5-8 November 2012

  • I. Sandu, A Beljaars, G Balsamo, A. Ghelli, 2011, Revision of the surface roughness length table, ECMWF Newsletter, No. 130, Winter 2011/12

  • I. Sandu, A Beljaars, G Balsamo, 2011, Revision of the roughness length table, ECWMF Technical Report, RD 11104

  • I. Sandu, A. Beljaars and G. Balsamo, 2011, Experience with the representation of stable conditions in the ECMWF model, Proceedings Workshop on Diurnal cycles and the stable boundary layer, ECMWF, 7-10 November 2011