Abstract
The longitudinal structure and annual cycle of mean meridional and eddy
momentum fluxes in the upper troposphere of the deep tropics are studied
using ERA-Interim reanalysis over a 40 year period. In a zonal mean
sense, these two terms oppose each other and peak during the Indian
summer monsoon. This zonal mean character arises from a rich
longitudinal structure revealed by splitting the globe into three zones,
namely, the Asia-West Pacific, central Pacific-West Atlantic, and
African sectors. The mean meridional convergence term is cohesive across
these three regions; it has a single peak in the boreal summer and
always acts to decelerate the zonal flow. On the other hand, eddy fluxes
are much more varied and go from being small and seasonally invariant in
the African sector to having large seasonal peaks of acceleration
(deceleration) in the Asia-West Pacific (central Pacific-West Atlantic)
sector. This longitudinal variation in eddy momentum fluxes presents
interesting insights into the overturning circulation in these zonally
limited sectors, which previously remained hidden in the zonal mean.