Atmospheric Monitoring has been assigned as the primary responsibility for Utah State University in the Telescope
Array Low Energy Extension (TALE) Project
TA/TAE US-Japan-ROC Collaboration
An Algorithm for Evaluation of Cloud
Esmaiel Malek (Biometeorologist)
Department of Plants, Soils and Biometeorology, Utah State University, Logan, UT 84322-4820, U.S.A.
Clouds affect the radiation budget of our planet by:
- Reflecting, - Absorbing, and
- Scattering of solar radiation - Re-emission of the terrestrial
radiation. They affect the weather and
climate by positive or negative feedbacks.
Automated Surface Observing Systems (ASOS)
The Vaisala model CT-12K laser beam ceilometer is used at the ASOS to
measure the cloud base height and report the sky conditions on an hourly
basis or at shorter intervals. This laser ceilometer is a fixed-type
whose transmitter and receiver point straight up at the cloud (if any) base.
- It is unable to measure clouds that are not above the sensor.
- A single cloud hanging overhead the sensor will cause overcast readings, whereas, a hole in the clouds could
cause a clear reading to be reported. To report cloudiness at the local scale, many of these type of ceilometers are needed. This is not a perfect method
for cloud measurement.
To overcome this problem, we have set up a ventilated radiation station at Cache-Logan Airport, Utah, U.S.A., since 1995, along
with an algorithm for evaluation of the
-cloud base temperature, - cloud base height, and
- percent of skies covered by cloud at the local scale.