LISST-Tau
User’s Manual
Appendix E: Measurement Description
Page 28
leading to
𝜏
𝑝𝑔
=
𝜏
𝜏
𝑤
=
𝐺𝜙
𝐺𝜙
𝑤
=
𝜙
𝜙
𝑤
.
In practice, raw transmission measurements are corrected for instrument temperature
effects (e.g., temperature dependence of photodiodes and LED spectral output, analog
electronics), so for a given measurement of raw transmission (
𝜙
), instrument temperature
(
𝑇
, units of
℃)
is also measured. An instrument temperature correction function (
𝐶(𝑇)
,
unitless) is defined such that corrected raw transmission is
𝜙
𝑐𝑜𝑟𝑟
=
𝜙
𝐶(𝑇)
.
For measurement of a water sample at instrument temperature
𝑇
, both the raw transmission
of the sample, and the pure water blank must be corrected for temperature. The pure water
blank is corrected for the instrument temperature at which it was collected:
𝜏
𝑝𝑔
=
𝜏
𝜏
𝑤
=
𝜙
𝑐𝑜𝑟𝑟
𝜙
𝑐𝑜𝑟𝑟,𝑤
=
𝜙
𝜙
𝑤
𝐶(𝑇
𝑤
)
𝐶(𝑇)
.
Beam attenuation for the sample is then calculated:
𝑐
𝑝𝑔
= −
1
𝐿
ln(𝜏
𝑝𝑔
).
