Tropical precipitation and
Hadley circulation on the
DWD-Aqua-Planet
H. Borth L. Göring & V. Wirth
D. Majewski H. Frank & B. Ritter
Reading 2005
GME-aqua-planet set-up
horizontal grid:
ni = 32 or ~ 2°
vertical grid:
31 hybrid levels (10 mbar)
GME-aqua-planet set-up
time steps for simulation:
dt = 600s
dt_con = 1800s
dt_radfull = 2h
time steps for calculation of fluxes:
dt_flx = 6h
APE-experiment set-up
four experiments with symmetric forcing:
control, peak, flat and qobs
spin-up from symmetric state of rest with
prescribed vertical structure:
6 months
APE-experiment set-up
time of simulation for averaging after spin-up:
1 year
Relative angular momentum
global mean
control
183 days
Total precipitation
global mean
control
183 days
Total Precipitation
zonal mean
time average
Convective rain
zonal mean
time average
Gridscale rain
zonal mean
time average
Simple models for the
Hadley circulation
Model of the General
Circulation (Hadley 1735)
(Lorenz 1967)
Model of the General
Circulation (Ferrel 1856)
(Lorenz 1967)
Stationary zonally symmetric
models for the Hadley cell

uv tan    u 
  u u   fv 
 

a
z  z 

u 2 tan 
1    u 
  u v   fu 

 

a
a  z  z 
single column

  u     E 
  u    

dynamics
z  z 




+ boundary
g
 u  0
conditions !!
z
0
(Lindzen 1990)
(Held & Hou 1980)
Stationary zonally symmetric
models for the Hadley cell
Zonal Velocity in the upper troposphere
velocity for
conserved
total
angular
momentum
without eddy
transport
Hide’s theorem
implies:
velocity in “balance”
with equilibrium
temperature
ΘE
U ≤ UM
meridional
circulation near
the equator
ΦH
(Lindzen 1990)
(Held & Hou 1980)
Stationary zonally symmetric
models for the Hadley cell
ΦE = (5R/3)1/2 (latitude where Hadley cell ends)
with
R = gH/(Ωa)1/2 ΔT
where
g gravity
Ω angular velocity
H height of tropopause
a planetary radius
ΔT =[Θ(Equator)-Θ(Pole)]/Θ0
(Lindzen 1990)
(Held & Hou 1980)
The Hadley circulation in the
ape experiments
Mass stream function and
total angular momentum (sm)
ape control
Total angular momentum
ape control
Zonal velocity
ape control
Mass stream function and
total angular momentum (sm)
ape flat
Total angular momentum
ape flat
Zonal velocity
ape flat
Meridional transport of total
angular momentum
mf
ape control
Meridional transport of
relative angular momentum
mf
ape control
Parts of meridional transport
of relative angular momentum
ape control
Meridional transport of total
angular momentum
mf
ape flat
Parts of meridional transport
of relative angular momentum
ape flat
Meridional transport of total
angular momentum
What drives the Hadley
circulation?
Energy fluxes
control
Energy fluxes
flat
Energy fluxes (TOA - Surface)
Goals
Interpret and try to get a better
understanding of the tropical mean
circulation in the ape-experiments using a
Held & Hou type zonally symmetric model
Connect single column dynamics with
general circulation in a simple (too simple?)
model
Future
Investigate temporal ans spatial structure of
tropical circulation and connect it to the
zonal mean fluxes