my name is wayne sure about professor of atmospheric science
and i came to see issue in nineteen seventy three after graduating from ucla in
the department of atmospheric science there
and i work mostly in dynamic meteorology
especially in tropical dynamics
and i have a group here which consists of about five graduate students now
and a three research associates
and i'd like to show just an example of some of the work we do
on a project first thing i'd like to show is an example of the inner
tropical convergence on
this is a satellite picture
from a g a stationary satellite
this is the california coast here
why use out here so this the eastern pacific
and this is a band of very deep convection in what's called inter tropical convergence
on
so that the air is going up
in the atmosphere in the inner tropical convergence
and it has to be drawn from the north and from the self
and it gives rise to what's called the heady circulation so you can imagine a
circulation where the air comes in at low levels goes up and then back in
the same thing on the other side
so there's two branches of the head recirculation since this is in july we call
this summer hemisphere branch and this the winter atmosphere branch
now what we did on our project is try to understand the relative strength of
the two branches of the head of circulation
now this is an example
of what the heavy circulation would look like
if
the inter tropical "'cause" virgins overwrite on the equator this is thirty north this is
the equator this is thirty self
and this is vertical going from the surface
to about fifteen kilometres or in pressure from about a thousand middle bars two hundred
millimetres
now if the
inter tropical convergence somewhere right on the equator
what happened is that there would circulate like this it would come in equal amounts
from either hemisphere and then go up and then go out in equal amounts
but on the average the inner trouble convergence zone is north the equator so we
have a situation like this
again this is thirty north thirty self this is equator
so this an example where the inner trouble convergence zone is located at ten degrees
north latitude
and what happens then he's that the air is a it's again drawn in from
the south and from the north
but these lines indicate how strong the circulation is and if you count the number
of lines here it's about three times the number of lines here which indicates that
this branch of the head recirculation is running about three times the string of this
print this is remember the winter
hemisphere branch of the head recirculation this is the summer hemisphere branch so we've determined
from this modeling it's the it's the winter hattie cell which always runs a stronger
than the summer had be so
and the reason for this is that
what drives the circulation is the release of latent heat in the upper branch that
is one water vapour is converted to liquid water
he just released
and that drives upward motion
so
the error has to come in from both directions and there's resistance to the movement
of air in the nor self direction and it turns out that resistance is less
at the equator then it is farther from the equator so it's easier for the
error just slip along this way then this way because it this errors right close
to the equator
so if we go back to this diagram here what you can imagine is that
you have an i t c z here at ten north
and you have the summer at least so running like this
and the winner had this already like this but the winter cell is running about
three times a strong
as the summer so in the model you can move the latitude of the head
the circulation it turns out that the maximum asymmetry between the two hemispheres happens when
the i t c z is located about thirteen degrees north
average position maybe ten degrees north so
the average position is close to the position of maximum asymmetry
so if you'd like to read more about this
all of this information is on a website