HAL CCSD
Space-time cascades and the scaling of ECMWF reanalyses: Fluxes and fields
Lovejoy, S.
Schertzer, D
Department of Physics [Montréal] ; McGill University = Université McGill [Montréal, Canada]
Centre de recherche sur la dynamique du système Terre (GEOTOP) ; École Polytechnique de Montréal (EPM)-McGill University = Université McGill [Montréal, Canada]-Université de Montréal (UdeM)-Université du Québec en Abitibi-Témiscamingue (UQAT)-Université du Québec à Rimouski (UQAR)-Concordia University [Montreal]-Université du Québec à Montréal = University of Québec in Montréal (UQAM)
Laboratoire Eau, Environnement et Systèmes Urbains (LEESU) ; AgroParisTech-Université Paris-Est Marne-la-Vallée (UPEM)-École des Ponts ParisTech (ENPC)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)
International audience
ISSN: 2169-897X
EISSN: 2169-8996
Journal of Geophysical Research: Atmospheres
American Geophysical Union
hal-00697552
https://enpc.hal.science/hal-00697552
https://enpc.hal.science/hal-00697552
Journal of Geophysical Research: Atmospheres, 2011, 116, pp.D14117. ⟨10.1029/2011JD015654⟩
DOI: 10.1029/2011JD015654
info:eu-repo/semantics/altIdentifier/doi/10.1029/2011JD015654
en
Multifractals
atmospheric turbulence
forecasting
reanalysis
[PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph]
[SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]
info:eu-repo/semantics/article
Journal articles
We consider the space-time scaling properties of the European Centre for Medium-Range Weather Forecasts (ECMWF) interim reanalysis products for the wind (u, v, w), humidity (h(s)), temperature (T), and geopotentials (z) and their corresponding turbulent fluxes using the daily 700 mbar products for the year 2006. Following previous studies on T, h(s), and u, we show that that the basic predictions of multiplicative cascade models are well respected over space-time scales below similar to 5000 km, shorter than similar to 5-10 days providing precise scale by scale determination of the reanalysis statistical properties (needed for example for stochastic parameterizations in ensemble forecasting systems). We innovate by including the meridional and vertical wind components (v, w) and geopotential (z), and by considering their horizontal anisotropies, their latitudinal variations and, perhaps most importantly, by directly analyzing the fields (not just fluxes). Whereas the fluxes have nearly isotropic exponents in space-time with little latitudinal variation (displaying only scale independent "trivial" anisotropy), the fields have significant scaling horizontal anisotropies. These complicate the interpretation of standard isotropic spectra and are likely to be artifacts. Many of the new (nonconservation) exponents (H) are nonstandard and currently have no adequate theoretical explanation although the key horizontal wind and temperature H exponents may be consequences of horizontal Kolmogorov scaling, combined with sloping isobaric surfaces. In time the scaling is broken at around 5-10 days, i.e., roughly the lifetime of planetary structures; lower frequencies are spectrally flatter: the "spectral plateau," weather-low-frequency weather regime.
2011-07-29