Abstract
ERA5 represents the state of the art for atmospheric reanalyses and is widely used in meteorological and climatological research. In this work, this dataset is evaluated using the wind kinetic energy spectrum. Seasonal climatologies are generated for 30° latitudinal bands in the Northern Hemisphere (periodic domain) and over the North Atlantic area (limited-area domain). The spectra are also assessed to determine the effective resolution of the reanalysis. The results present notable differences between the latitudinal domains, indicating that ERA5 is properly capturing the synoptic conditions. The seasonal variability is adequate too, being winter the most energetic, and summer the least energetic season. The limited area domain results introduce a larger energy density and range. Despite the good results for the synoptic scales, the reanalysis’ spectra are not able to properly reproduce the dissipation rates at mesoscale. This is a source of uncertainties which needs to be taken into account when using the dataset. Finally, a cyclone tropical transition is presented as a case study. The spectrum generated shows a clear difference in energy density at every wavelength, as expected for a highly-energetic status of the atmosphere.
Highlights
At the present time, most of the meteorological predictions and forecasting products are based on numerical weather prediction (NWP) models
Thanks to the enhancement of computational resources, the constant increase of spatio-temporal resolution in NWP models has reached a challenging point for their own improvement, as nowadays limited-area mesoscalar model resolutions are verging on the microscale (Prósper et al 2019; Siewert and Kroszczynski 2020)
These figures are analysed several times in the paper, as the results for the effective resolution and the climatologies are evaluated in separate subsections
Summary
Most of the meteorological predictions and forecasting products are based on numerical weather prediction (NWP) models. The distance of sampling will mark the lower limit of the curve (2Δx as per Nyquist 1928) and the longitude of the observation segment will define the upper limit of it (as it effectively filters the maximum wavelength) These conditions to the curve are present in NWP simulations due to grid and domain sizes, and limitedarea models will introduce additional modifications to the curve (Skamarock 2004). Several researchers have been able to adequately reproduce the observations in global and limited area NWP simulations (Abdalla et al 2013; Koshyk and Hamilton 2001; Ricard et al 2013; Skamarock 2004; Takahashi et al 2006), proving the effective resolution of the respective models used. This shows the limitations of GCMs for the study of fine scale phenomena and the current value of limited-area high-resolution NWP models at the present state of the art
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