ST. PETERSBURG, FL - In the 1970’s and 80’s, commercial aircraft were used to measure wind velocity and temperature in the upper troposphere and lower stratosphere. From these measurements, atmospheric scientists and forecasters have derived useful information that helped to improve understanding and modeling of changes in our weather. One of the most significant outcomes of this activity was the derivation of the equations describing distributions of the kinetic and potential energies of the atmospheric circulation over different scales of motion known as the kinetic and potential energies spectra. Named after their inventors, Drs. G.D. Nastromand K.S. Gage, these spectra exhibited little variation with altitude, latitude and season, and due to this universality, they became known as canonical.
Many researchers rely on the Nastrom & Gage, or canonical energy spectra, assuming that they are latitudinal-independent and so can be latitudinally averaged. Upon careful consideration, however, one reveals considerable dependence on latitude, particularly, in the equatorial region. Thus, the latitudinal averaging of the spectra and, possibly, other flow characteristics may lead to spurious results and, as Dr. Boris Galperin of the USF College of Marine Science explains, “…losing the physics.”
Clearly, a better qualitative and quantitative understanding of the physics behind the Nastrom & Gage spectra has been required but is had evaded scientists for about 50 years.
Dr. Galperin, professor of physical oceanography at USFCMS, and Dr. Semion Sukoriansky, from the Ben-Gurion University in Beer Sheva,Israel, have recently developed a new theory of turbulence in rotating systems, such as Earth and other planets. This is an analytical theory built at the level of first principles, meaning that it relies upon the most fundamental laws of motion and involves no empirical constants. The equations for the kinetic energy spectra derived from that theory agree almost perfectly with the Nastrom & Gage spectra. The theory explains the physics of the spectra and sheds light upon their universality. In addition, it quantifies their latitudinal dependence. Furthermore, the theory predicts that the same spectra should exist in the ocean and indeed, comparisons with oceanic data confirm this prediction. Thus, the theory uncovers the deep-rooted affinity between large-scale atmospheric and oceanic turbulence. In addition, it explains how energy flows from large scales to small scales and eventually dissipates on smallest scales, something that modern theories have difficulty with.
The value of the theory is not only in explaining the background physics of circulations but also in providing quantitative metrics that can be used for validation and verification of the results of numerical models. One of the important outcomes of this research could be improved performance of the models used for numerical weather prediction.
From turbulence and waves to large-scale weather events, the theory’s applications are broad and far reaching. Future NASA missions, for example, could see improvements in the interpretation of Earth observations (sea surface elevations, velocities,temperature, etc.) through the use of advanced models that rely upon the new theory.
Observing that recent developments in the study of fluid dynamics tend to pull in various directions, often contradicting each other, Galperin hopes the new theory will have a unifying effect while providing simpler answers to complex problems through a better understanding of the flow energetics and the underlying energy spectra.
For additional works by Boris Galperin view the links below.