Evaluation of a Simple Theoretical Expression for Hadley Cell Width
Abstract
The latitudinal width of Earth's Hadley cell has a simple expression that is a function of the planetary radius, and the atmosphere's angular velocity, stability, and depth: the cell width varies as the square root of the Brunt-Vaisala frequency and the tropospheric depth such that a deep, stable atmosphere extends further poleward. There are multiple avenues to this expression based on either the dynamics (Schneider (1977); Held (2000)) or the statistical mechanics (Garrett et al (2016)) of the cell. Here, we contrast these approaches and test the expression for application to other planetary bodies within the solar system. In general, we find the expression accounts for the wide range of cell widths, ranging from very narrow (Jupiter) to very wide (Titan). However, there is a choice of atmospheric depth to be considered in the calculation, and we find that the effective depth that leads to best agreement with observed cell widths is closest to the tropospheric density scale height rather than the depth of the troposphere itself, as has commonly been assumed. There remain significant discrepancies that require explanation, however. For example, the effective depth for Earth is 11.3 km rather than 8.5 km and Uranus has an effective depth of 20 km compared to its tropospheric scale height of 27.7 km. We discuss possible explanations for these differences.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.A53F0371R
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSESDE: 3319 General circulation;
- ATMOSPHERIC PROCESSESDE: 3339 Ocean/atmosphere interactions;
- ATMOSPHERIC PROCESSESDE: 3373 Tropical dynamics;
- ATMOSPHERIC PROCESSES