2021/01/16 by Anastassia M. Makarieva, Makarieva, Anastassia M., A. V. Nefiodov +2 · 1 citation
Earth and Planetary Sciences · Environmental Science · Mathematics · Physics and Astronomy · #Atmospheric and Oceanic Physics (physics.ao-ph) #Atmospheric sciences #Climate variability and models #Environmental science #FOS: Physical sciences #Fluid Dynamics (physics.flu-dyn) #Mathematics #Mechanics #Meteorological Phenomena and Simulations #Meteorology #Ocean Waves and Remote Sensing #Outflow #Physics #RADIUS #Temperature gradient #Thermodynamics #Tropical and Extratropical Cyclones Research #Tropical cyclone #Velocity gradient #Wind gradient #Wind profile power law #Wind speed #physics.ao-ph #physics.flu-dyn
paper · pdf · doi:10.48550/arxiv.2101.06500
published in arXiv (Cornell University) (Cornell University) · Third revision for the Journal of the Atmospheric Sciences. Reply to the two reviewers can be found in Appendix E. 41 pages, 3 figures, 2 tables
openalex publication_date 2021/01/16 · arxiv created 2022/01/25 · arxiv updated 2022/01/26 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Emanuel's concept of maximum potential intensity (E-PI) estimates the maximum velocity of tropical cyclones from environmental parameters. At the point of maximum wind, E-PI's key equation relates proportionally the centrifugal acceleration (squared maximum velocity divided by radius) to the radial gradient of saturated moist entropy. The proportionality coefficient depends on the outflow temperature. Here it is shown that a different relationship between the same quantities derives straightforwardly from the gradient-wind balance and the definition of entropy, with the proportionality coefficient depending on the radial gradient of local air temperature. The robust alternative reveals a previously unexplored constraint: for E-PI to be valid, the outflow temperature should be a function of the radial temperature gradient at the point of maximum wind. When the air is horizontally isothermal (which, as we argue, is not an uncommon condition), this constraint cannot be satisfied, and E-PI's key equation underestimates the squared maximum velocity by approximately twofold. This explains "superintensity" (maximum wind speeds exceeding E-PI). The new formulation predicts less superintensity at higher temperatures, corroborating recent numerical simulations. Previous analyses are re-evaluated to reveal inconsistent support for the explanation of superintensity by supergradient winds alone. In Hurricane Isabel 2003, maximum superintensity is found to be associated with minimal gradient-wind imbalance. Modified to diagnostically account for supergradient winds, the new formulation shows that air temperature increasing towards the storm center can mask the effect of gradient-wind imbalance, thus reducing "superintensity" and formally bringing E-PI closer to observations. The implications of these findings for assessing real storms are discussed.