Is there a fourth meridional cell in the general circulation of the atmosphere?
12:30 pm October 16 in Room 2155
The three-cell model for the atmospheric circulation including the
Hadley, Ferrel and Polar cells in each of two hemispheres has been
accepted and used in climate study for a long time. According to the
principle for conservation of angular momentum, a decrease in rotation
radius will cause an increase in westerly velocity aloft for the Polar
cell so that it cannot cross as many latitudes as the Hadley cell does
in the lower latitudes because the distance between the tropospheric
air particle and the earth's rotating axis reduces more rapidly
poleward beyond the latitude of 60°. Using three different global
reanalysis products and one climate model simulation from the
historical and future runs, we are able to show that there might be a
fourth cell in each of two high latitudes. The analyses of meridional
section streamline (MSS) and meridional-mass stream function (MSF)
provided some evidences to support the existence of the fourth cells.
The intensity and location of the fourth cell vary with season, and in
some months it becomes invisible. Further, due to the elevated
topography, the Antarctic cell is much weaker than the Arctic cell.
This poses a challenge to the climate and meteorological community to
verify the discovery with stronger observational basis, improved
modelling capacity, and better assimilation over high latitudes.