
Babiano, A. and T. Dubos. 2005. On the contribution of coherent vortices to the 2D inverse energy cascade. J. Fluid Mech., 529, 97–116.



Carlotti, P. and P. Drobinski. 2004. Length scales in wallbounded highReynoldsnumber turbulence. Journal Of Fluid Mechanics, 516, 239–264.
Résumé: In this study, estimates of inhomogeneous integral scales are derived from rapid distortion theory (RDT) for the case of wallbounded highReynoldsnumber turbulence and from largeeddy simulation (LES) of a neutrally stratified atmospheric boundary layer (ABL). As for any inhomogeneous flow, integral scales in different directions are introduced. Downward integral scales are introduced since they differ from the usual vertical integral scales because of the presence of the wall. The study concentrates on the length scales based on the vertical velocity, which are the most affected by blocking by the wall, which is assumed to be horizontal. It is shown from RDT that the asymptotic behaviour of the integral length scales for small heights depends crucially on the spectrum power law 2p. When 2p > 1 there is always one length scale which does not scale with the distance to the wall z. Only the downward integral scale is proportional to z for any 2p. These results show that the assumption, often made in studies of boundary layers, that all the lengths are proportional to z, is not compatible with the assumption of a spectrum decaying according to Kolmogorovâ€™s law, but rather with a spectrum following a I power law. It is an encouraging result since there is now widespread theoretical, experimental and numerical evidence that such a 1 powerlaw subrange exists in the spectra of highReynoldsnumber wallbounded turbulence, for eddies larger than z. The RDT results allow an interpretation of the vertical profiles of the integral length scales computed from the LES outputs: above the third grid point, the vertical profiles of the integral length scales have a linear shape, as expected for highReynoldsnumber turbulence and 2p = 1. Very close to the surface, the upward integral length scales decreases with z because of the fast decay of the spectrum (2p > 2) from the LES subgrid model. The longitudinaltotransverse integral length scale ratio is computed using RDT and LES. This ratio is interpreted as the aspect ratio of elongated nearwall large eddies, which are ubiquitous features of LES of boundary layers in which shear plays an important role in the dynamics. The LES shows that the longitudinaltotransverse integral length scale ratio is an increasing function of z, ranging between 1 and 3, which is of the order of magnitude of the published theoretical value of 3.5. From RDT, the evolution with z of the longitudinaltotransverse integral length scale ratio means either that the velocity shear beta decreases with z and the spectral power law 2p varies in a nontrivial manner, or if both the RDT and LES are valid that the scale of the large eddies is proportional to betaz with beta varying from 1.3 to about 4.
MotsClés: intro



Dubos, T. and A. Babiano. 2003. Comparing the twodimensional cascades of vorticity and a passive scalar. J. Fluid. Mech, 492, 131–145.



Dubos, T. and A. Babiano. 2002. Cascades in twodimensional mixing : a physical space approach. J. Fluid Mech., 467, 81–100.



Clerbaux, C., S. Turquety, P. Coheur. 2010. Infrared remote sensing of atmospheric composition and air quality: Towards operational applications. Comptes Rendus Geosciences, 342(45), 349–356.



Dubos, T. 2001. A spatially selective parameterization for the transport of a passive or active tracer by a large scale flow. C.R.Ac.Sci. (Paris), 329, 509–516.



Dubos, T. 2005. Frame invariance and conservation in twodimensional subgrid models. Physica D, 202, 1–15.



Menut, L., Mailler, S., Dupont, J.C., Haeffelin, M., Elias, T. 2014. Predictability of the meteorological conditions favorable to radiative fog formation during the 2011 ParisFog campaign. Boundary Layer Meteorology, 150(2), 277–297.



Omrani, H., P. Drobinski and T. Dubos. 2012. Investigation of indiscriminate nudging and predictability in a nested quasigeostrophic model. Quarterly Journal of the Royal Meteorological Society, 138(662), 158–169.
Résumé: In this work, we consider the effect of indiscriminate nudging time on an idealized highresolution global model (GM) and limitedarea model (LAM) simulations. The model used is a twolayer quasigeostrophic model on the betaplane. The effect of nudging is studied as a function of the predictability time, following a 'Big Brother' experimental approach: a highresolution 'global' model is used to generate a 'reference run'. These fields are filtered afterwards to remove small scales and provide the coarseresolution fields which are used to drive the highresolution GM and the LAM. Comparison of the reference fields and the highresolution runs over the same region allows the estimation of the ability of the highresolution GM and LAM to regenerate the removed small scales. This fully nonlinear setup mimics the configuration used for regional highresolution atmospheric modelling. For the highresolution GM, the results show that the behaviour of the nudged model depends primarily on the ratio of the nudging time to the predictability time. When the nudging time is very small compared to the predictability time, the model reproduces the large scale used to drive themodel. On the other hand, if the nudging time is close to or larger than the predictability time, the nudging effect is weak and both large and small scales are poorly reproduced compared to the reference fields. The best result is obtained with a nudging time close to half the predictability time. This technique clearly improves themodel capacity to reproduce the reference fields. For the highresolution LAM, our results show that for a sufficiently small domain the simulation is largely controlled by the lateral boundary conditions (LBCs) and is quasiinsensitive to nudging. However, if the domain size exceeds a few Rossby radii, the highresolution LAM becomes sensitive to initial conditions and the control exerted by LBCs becomes insufficient to prevent a divergence from the driving fields. Although the reconstructed fine scales are significantly damped, they are surprisingly well correlated to their reference values in a deterministic sense, not a statistical sense.
MotsClés: intro; downscaling; large/smallscale perturbations; potential vorticity; uncertainties



Omrani H., D.P., Dubos T. 2012. Spectral Nudging in Regional Climate Modelling: How Strongly Should we Nudge? QJRMS, 138, 1808–1813.



Chaboureau JP, R.E., Pinty JP, Cyrille Flamant, Paolo Di Girolamo, Christoph Kiemle, Andreas Behrendt, Hélène Chepfer, Marjolaine Chiriaco and Volker Wulfmeyert. 2011. Longrange transport of Saharan dust and its radiative impact on precipitation forecast: a case study during the Convective and Orographicallyinduced Precipitation Study (COPS). Q. Joyal Meteo. Soc., 137, 236–251.



Drobinski, P., R. Rotunno and T. Dubos. 2011. Linear theory of the sea breeze in a thermal wind. Q. J. R. Meteorol. Soc., 137(659), 1602–1609.
Résumé: This article investigates the linear dynamics of the sea breeze in an alongshore thermal wind shear. The present analysis shows that the seabreeze circulation is tilted towards the slanted isentropes associated with the thermal wind. At a critical value of the thermal wind shear, the tilt of the seabreeze circulation becomes equal to the slope of the background isentropes. The present analysis also shows a spatial shift between the heating pattern and the seabreeze circulation. The present linear theory is then applied to interpret measurements made in the vicinity of New York City where there is a warmseason synoptic southwesterly jet. It is compared with observations and past numerical simulations. Agreement is found with respect to the enhanced alongcoast wind that follows the tilted isentropes, the order of magnitude of the isentrope tilt and the clockwise rotating wind hodograph showing the jet maximum peaking at 1800 solar time. There is a disagreement between theory and observations on the phase lag between the jet maximum and the crossshore pressure gradient maximum. However, this disagreement can reasonably be attributed to either the angle made by the synoptic jet to the coastline and/or the presence of friction. The inland spatial shift of the breeze indicated by the theory might also be indirectly confirmed by the coastal inland wind observations of a larger diurnal amplitude for a stronger synoptic jet. Copyright (C) 2011 Royal Meteorological Society
MotsClés: coastal lowlevel jet; intro; breeze circulation; linear model



Salameh, T., P. Drobinski and T. Dubos. 2010. The effect of indiscriminate nudging time on large and small scales in regional climate modelling: Application to the Mediterranean basin. Quarterly Journal Of The Royal Meteorological Society, 136(646, Part A), 170–182.
Résumé: A regional climate model (RCM) is driven by the ERA40 reanalyses produced by the ECMWF general circulation model (GCM) to simulate the winter 1998 climate over the Mediterranean basin. In this article, we consider the effects on internal variability of temporal nudging. This technique consists of relaxing the RCMâ€™s prognostic variables towards the GCM values within a predetermined timescale, with the aim of disallowing large and unrealistic departures between driving and driven fields. To interpret the significant effect of time nudging on the regional climate prediction, we develop a â€˜toy modelâ€™ basically consisting of resolving a linear transport equation with a Newtonian relaxation term. This model predicts the existence of an optimal nudging time which depends on the timescale over which numerical errors affect significantly the accuracy of the â€˜regionalâ€™ solution at the large spatial scales, and the typical timescale of the smallscale phenomena that are not resolved by the GCM. Copyright (C) 2010 Royal Meteorological Society
MotsClés: intro



Alexander, M.J. and 15 others. 2010. Recent developments in gravitywave effects in climate models and the global distribution of gravitywave momentum flux from observations and models. Q. J. R. Meteorol. Soc., 136, 1103–1124.



Plougonven, R., A. Arsac, A. Hertzog, L. Guez and F. Vial. 2010. Sensitivity study for mesoscale simulations of gravity waves above Antarctica during Vorcore. Q. J. R. Meteorol. Soc., 136, 1371–1377.

