A schematic of the relevant processes
of cloud processes and transport
of zonal mean circulation. Arrows indicate
circulation, black dashed line is clear-sky level of zero
net radiative heating (LZRH), and black solid lines show
isentropes (in K, based on European Centre for Medium Range
Weather Forecasts 40-year reanalysis (ERA-40)). The letter
indicates deep convection: main outflow around
200 hPa, rapid decay of outflow with height in tropical
tropopause layer (TTL), and rare penetrations of tropopause.
Fast vertical transport of tracers from boundary layer
into the TTL.
The letter b
indicates radiative cooling
The letter c
indicates subtropical jets, which
limit quasi-isentropic exchange between troposphere and
stratosphere (transport barrier).
The letter d
indicates radiative heating, which
balances forced diabatic ascent.
The letter e
indicates rapid meridional transport of
tracers and mixing.
The letter f
indicates the edge of
the ‘‘tropical pipe,’’ relative isolation of tropics, and
stirring over extratropics (‘‘the surf zone’’).
The letter g
indicates deep convective cloud.
The letter h
indicates the convective core overshooting
its level of neutral buoyancy.
The letter i
indicates ubiquitous optically
(and geometrically) thin, horizontally extensive cirrus
clouds, often formed in situ.
The height-pressure-potential temperature relations are
based on tropical annual mean temperature fields, with
height values rounded to the nearest 0.5 km.