I intend to collect temperature data of the lower atmosphere using
sounding data of the last 50 years, trying also to correct those data
according to the time-constant (thermal lag) of the temperature
sensors.

Unfortunately not much can be found in the literature on the thermal
lag of different type of sondes. Most papers focus on the behaviour of
the thermal sensors in the upper atmosphere; corrections are thus
applied for radiation effects but apparently not for the thermal lag.
While trying to find this information of actual models from data
sheets (as far as available on the Internet) only those from the
Vaisala sondes have been found to provide this information.

During the last 50 years the temperature sensors have undergone a
technical development. Older sensor types had a thermal lag (at 1000
hPa) of several seconds whereas new sensors have a lag of only a few
tenth of seconds. This improvement seems to have happened in steps and
is related to the appearance of certain types of sondes. Probably
other types having followed some time later when reaching the same
state of technology.

If I interpret the texts found so far correct, the technical
development seems to have been approximatively like this:

End 40s / begin 50s:
A summary of a paper indicates that the observed thermal lag would
amount to about 25s at "useful sounding heights". Depending what
"useful heights" were at that time, the corresponding time-constant
may have been at 1000hPa around 6 to 8 seconds.

End 80s / begin 90s:
A paper comparing temperature measurements near the surface between
balloon soundings and tethered kite estimates for the VIZ sonde a time-
constant which reasonably compares to the 5 to 6 seconds which they
received from the manufacturer by private communication.

However, in the 80s numerous sounding stations started to use the
Vaisala sonde RS80, which claims to have a thermal sensor with a time-
constant of only 2.5 seconds.

Questions:
--------------

Q1) Is it correct to assume that the state of technology (except RS80)
was such that the time-constant of the temperature sensors reduced
only slowly between the 50s and the 90s from about 6-8s to 5-6s?

Q2) Would it be reasonable to assume that this improvement was more or
less linear in time?

Q3) Does this correspond approximatively also for the following sondes
which were in use during those years: VIZ, India, MARS or MRZ,
Shanghai Radio or GZZ, KEW, Mesural, Philips?

Q4) Which models of those sondes (mentioned in Q3) had for the first
time a temperature sensor with a time-constant of approx. 2-3s and
when have those sondes generally started to be used?

The next big step in reducing the time-constant of the temperature
sensor seems to have come again from Vaisala with their sonde RS90
having a time-constant of only a few tenth of seconds.

Q5) Which of the following sondes VIZ, India, MARS or MRZ and
Shanghai Radio or GZZ had for the first time a temperature sensor with
a time-constant of less than 1s and when have those sondes generally
started to be used?


May be there is one or the other reader in this group which may be
able to help to obtain some additional information on this subject.
Just in case this is not directly your subject: may I ask you in this
case to please forward this request to someone you know that he may be
able to help. Thank you.

In the mean time a technical note could be found reporting some
statistics of observations done with RS13 and RS18 sondes during the
decade of the 70s. The report mentions:

"No lag corrections were applied to the observed temperatures. It was
estimated that the lag corrections amount to only 0.3 to 0.5 degrees
Celsius in the troposphere when the lapse rate was dry adiabatic."

According to this text the time-constant would have corresponded to
about 6s to 10 s.

This would indicate that the time-constant of the temperature sensors
didn't noticeably improve between the 50s and (the beginning of ?) the
70s.