If a rotating shadowband spectrometer can be field proven, it will be included in the instrument complement. An automated filter photometer will also be employed to provide a moderate resolution measurement comparable to that obtained using hand held sunphotometers. The instrumentation deployed at the base station will provide redundancy, to support calibration and to facilitate quality control. Previous radiation studies have had to rely upon radiosonde or aircraft measurements of temperature, humidity, cloud and aerosol profiles. However, the atmosphere is sufficiently dynamic that such profiles are rarely useful for studies of radiative processes.
Radiation properties change with the instantaneous state of the atmosphere.
Such instruments are necessary to gain access to data and regions inaccessible to remote measurement, and for calibration, but these profiles are not coincident with the radiation observations either in time or space. Rapid atmospheric structure variation is an especially difficult restriction for the measurement of atmospheric humidity, which is now known to vary on small scales. Melfi et al. Even a calm night exhibited significant turbulent moisture variation. They observed step discontinuities in the moisture profile, which changed on time scales of a few minutes or spatial variation on the scale of a few hundred meters.