| Abstrakt: |
The mesoscale spectrum describes the distribution of kinetic energy in the Earth's atmosphere between length scales of 10 and 400 km. Since the first observations, the origins of this spectrum have been controversial. At synoptic scales, the spectrum follows a −3 spectral slope, consistent with two‐dimensional turbulence theory, but a shallower −5/3 slope was observed at the shorter mesoscales. The cause of the shallower slope remains obscure, illustrating our lack of understanding. Through a novel coarse‐graining methodology, we are able to present a spatio‐temporal climatology of the spectral slope. We find convection and orography have a shallowing effect and can quantify this using "conditioned spectra." These are typical spectra for a meteorological condition, obtained by aggregating spectra where the condition holds. This allows the investigation of new relationships, such as that between energy flux and spectral slope. Potential future applications of our methodology include predictability research and model validation. Plain Language Summary: The kinetic energy spectrum describes how much energy is at different spatial scales in the atmosphere, from km‐scale atmospheric waves to large‐scale weather systems 1,000 km across. This distribution may influence predictability. Edward Lorenz argued that the spectrum can determine whether a fluid can be forecast arbitrarily far into the future or not. In this paper, we employ a novel method to reveal how the spectrum varies in different locations on Earth. In addition, we generate the first "conditioned spectra," which are the aggregated spectra for different levels of orography, convection and energy transfer. We are able to demonstrate the tendency of convection and orography to increase small‐scale energy and show their effect on the classic global spectrum. Spectra are vital for model validation and predictability research; therefore, these results and the methods used to obtain them are of interest to meteorology practitioners, theorists and those in neighboring fields. Key Points: Global maps of spectral slope are produced through a novel coarse‐graining methodOrography and precipitation shallow the spectral slope in the troposphere significantlyConditioned spectra quantify the relationship between slope, orography, precipitation and energy flux [ABSTRACT FROM AUTHOR] |
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