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Paul,

First of all, thank you  for takeing all the time, getting the copy and
looking it up!

Some other source (Andy Young - thank you George!) told me in the meantime ,
that the figures  found are plots of digitised data taken from the 1966
supplement. They represent these data, but are not the original data.

you wrote:
> I now have the U.S. Standard Atmosphere 1976 book from the library. The
> only temperature vs. latitude graphs I see are for heights of 40, 60,
> and 80 km. I don't think these are very useful for computing refraction,
> since above 40 km the air is so rarefied that surely it can't have much
> effect.
>
> The book does say, "In the region 0 to 86 km, latitudinal and seasonal
> variations about the Standard are observed. In addition, both
> observation and inference show that extreme departures of considerable
> magnitude occur. This information is being developed in detail in a
> series of reference atmospheres which will extend to 90 km.

Could it be, that in the 1976 edition they removed the lower part of the
atmosphere since there are sufficient balloon data available in this most
variing part between 0 and 30 to 40km, and left the data for the upper parts
which seem to be more difficult to obtain (rockets, LIDAR)?

Do the graphs in the 1976 supplement for heights of 40, 60 and 80km actually
show typical temperature profiles for different latitudes?

> "These reference atmospheres are being prepared under the direction of
> COESA to replace those described in the U.S. Standard Atmosphere
> Supplement, 1966. They will include mean monthly atmospheres for each
> 15° of latitude from Equator to pole. Winter models at 60° and 75°N will
> depict typical conditions over both North America and Europe. These data
> will provide information to scientists and engineers on latitudinal,
> longitudinal, seasonal, and day-to-day changes in atmospheric
> structure..."
>
> I don't know whether or not those reference atmospheres were ever
> completed. Try a search engine.

Hopefully they find soon that there is more on the globe than North America
and Europe ;-)
Unfortunately I couldn't find some data as indicated above, when searching
under COESA.

Coming back to the comment I made referring missing pressure data:
>> Without this information the data are unfortunately useless.
This comment was made when I racked my brain on how I would have to handle
the balloon data, if I would decide to use them. At one moment I thought
misleadingly that the temperature and pressure data would have to be scaled
to the selected standard condition before using the data for calculating
refraction values. It is at this stage when I wrote the above comment which
is not correct. The temperature pressure and density profiles are calculated
from the lapse rate profile which is built-up on the selected standard
condition at sea level. One therefore needs only to extract the lapse rate
profile (these data are relative and not absolute) from the balloon data or
from graphs.

Based on the available graphs, I analysed in the meantime the seasonal and
latitudinal influence on the refraction at the horizon, the dip at the
horizon and the corresponding K-factor  (used for terrestrial refraction and
in simplified formulae for calculating the dip) for a height of 10m (which I
thought to be a reasonable value for nautical navigation).These calculations
were done iterative to come "very close" to the actual edge of the horizon.
The results show that latitude and season (independent of the seasonal
temperature differences) are each of them responsible for a variation of
about 2arc min. I can provide more details on these results, if this is of
interest.

Marcel

   

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