An annual cycle of long lived stratospheric gases from MIPAS M. N. Juckes British Atmospheric Data Centre, SSTD, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK
Abstract. MIPAS, on ENVISAT, has made high quality observations of ozone,
methane and water vapour.
Gridded fields, at 4 hourly intervals and, have been calculated for
all of 2003 using data assimilation with isentropic advection as a constraint.
The gridded fields are validated against independent measurements
(from 7 other instruments in the case of ozone, 3 for water vapour and one for methane).
For ozone the results are in agreement with previously published
results. For water vapour the bias relative to HALOE is below 10% between
20 and 48 km, and the standard deviation is below 12% in this range. Departures
from SAGE II and POAM III are substantially larger. The methane analysis
has a bias of less than 5% relative to HALOE between 23 and 40 km, with a
standard deviation less than 10% in this height range.
The water vapour field clearly reflects the upward motion in
the lower tropical stratosphere, while both water vapour and methane
show the signature of advection higher up. In the polar regions
the descent in the vortex is clearly visible, with strong descent
in autumn giving way to weaker descent through the winter.
Descent rates of around 10−3\ms are found during the formation
of the polar vortices, slowing to around 3×10−4\ms during
the winter. Ascent of around 2×10−4\ms in the tropics
is revealed by the water vapour and total observed hydrogen
fields (4 times the methane plus twice the water vapour concentration).
The total observed hydrogen is depleted in the polar upper
stratosphere when air is advected down
from the upper mesosphere.
Citation: Juckes, M. N.: An annual cycle of long lived stratospheric gases from MIPAS, Atmos. Chem. Phys., 7, 1879-1897, doi:10.5194/acp-7-1879-2007, 2007.