Northern Hemisphere Polar Winter UVZT Animations
The data used are the daily stratospheric analyses from UK Met office
("UKMO", now "MetO") originally by way of the British Atmospheric
Data Centre (BADC),
and now through The Centre for Environmental Data Analysis (CEDA).
North polar stereographic projections are shown (but with linear
latitude spacing).
The scales are fixed for each parameter/level over the duration
of the animation as given at the bottom of each contour plot. That is
the contour step is (max-min)/12, since there are 12 colour levels,
increasing as grey to red-brown. These were chosen to show the most
detail in mid winter (consequently fall and spring exhibit less detail).
In the case of U,V the scales have been modified
slightly so there is an exact zero contour (as shown by tiny legend off the bottom right
"corner" of the plot). The Z parameter is geopotential height minus
"nominal height" [ The nominal height is calculated as
(64.8/4) x (3. - log10 Pmb) Km.] Greenwich Meridian (zero longitude) is
at the bottom, as is the low latitude limit.
When time permits, the rest of the available (1992-) years will be posted
(some may be in an older format)
Unfortunately the MetO/UKMO stratospheric data we have been using are no longer
available. Consequently, for this year we had switched to NCEP reanalysis1,
which has an upper limit of 10 hPa (~30 Km). But recently the GEM model
(Meteorological Service of Canada, documentation at
https://eccc-msc.github.io/open-data/readme_en/)
has gone from 20 hPa to a 1 hPa upper limit (~49 Km),
much better for us. So we will use it instead.
The best animation scales were pre-chosen for each parameter/pressure level and remain the same day-to-day
over the winter. There are twelve Colours ranging from grey (minimum) to dark red (maximum).The (approximate)
values for grey and dark red appear below the contour plot. Contours for exact zero levels are indicated
by small insets.
Most recent winter day
(Our go-to program for controlled viewing of the gif89a animations
is "gif movie gear". )