Mj. Hammond et al., A FAST-RESPONSE MULTIPASS TRANSMISSOMETER OPERATING OVER VARIABLE WAVELENGTH RANGES, Atmospheric environment, 29(1), 1995, pp. 69-76
An instrument capable of making accurate measurements of the extinctio
n of visible and near infrared radiation through the thickest of cloud
s is presented. The transmissometer is multi-pass with a path length o
f 17.1 m and has a short integration time, operating at similar to 6 H
z The instrument is compact and portable and can be operated at any si
te of interest. ''Clear-air'' signals are obtained by physically isola
ting the sample volume from the ambient conditions; this ensures that
these signals can be measured without waiting for cloud-free condition
s. The current operation is in the wavelength range 575-1150 nm, set b
y the limits of the optical coatings and the monochromator. The spectr
al extinction can be calculated to within 10% over the wavelength rang
e 600-1100 nm. Phase-sensitive detection at 650 Hz is used to reduce d
etector noise. The instrument has also been used to investigate the at
mospheric transmission in the infrared region (1400 nm-2900 nm).