6
• Extended-Surface Reflectance and In Situ Measurements: development of methods for
measuring surface reflectance over a larger area (e.g., 20 X 20 km) by using a tower or
small aircraft, special aircraft and balloon experiments to collect in situ information to
validate the remote sensing measurements.
• Atmospheric Inhomogeneities: studies aimed at improving the understanding and
measurement of the radiative features of inhomogeneous and broken clouds
• Special Measurements: development of cost-effective instrumentation and methods for
measurement of spectral ultraviolet and infrared SRB that will aid the improvement of
satellite algorithm design and validation of satellite SRB determinations
• Improvement of Instrumentation: investigations to improve the design and performance
of “standardized” instrumentation such as sunphotometers and pyranometers, and
incorporate, improve, and develop more sophisticated remote sensing instrumentation to
enhance the cloud-observing abilities of the BSRN.
Site Evaluation Criteria
Characteristic Locations Representing Example Location
Radiation field
values
large variability, both synoptic and seasonal scales Siberia
Satellite algorithm
performance
a range of difficulty for set retrievals Equatorial Indian Ocean
Temperate Oceania
Cloud Properties a range of cloud types Tropical Pacific
Climate Change the potentially higher sensitivity of a region to changes in
global climate
Antarctic coasts, Northern
Canada
Satellite Coverage a range dependence on the orbit, viewing angle, overlap
regions
Spitsbergen
Unusual
atmospheric
phenomenon
a range of unusual atmospheric phenomenon (aerosol,
clear skies, etc.)
Sahel, Tropical Pacific
Surface Cover a range of surface cover (e.g., snow, sea ice, ocean,
vegetated, desert, etc.)
South Ocean, Ice Island,
Equatorial Africa
Climatic Regions a range of climate regions (polar, tropical, etc.) Ice Island, Central
Australia, Antarctic Coast
Upwelling flux
studies
areas where upwelling flux studies would be of particular
value to validation because of the site qualities and in
some cases the existence of SRB measurement facilities
Boulder Tower
Calibration locations possessing uniform and high surface
reflectance properties for the calibration of satellite-
borne instruments
Prairie, Amazon Basin
Table 1.2. List of site evaluation criteria based upon a selection of desirable surface/atm ospheric
characteristics and the results of satellite algorithm performance comparisons.
• The type of geographical region where such stations would most aid the development
and validation of satellite algorithms (Table 1.2) and specific research areas on
instrument development and calibration were also proposed at the workshop.
While the objectives and goals have been laid down specifically for climate research, the impact
of the BSRN concept is far wider than just this one community. By providing a standard means of
measuring radiation to a known accuracy, other programs and countries can implement these
ideas with little added effort. Other programs such as the Global Atmosphere Watch (GAW) and
the Atmospheric Radiation Measurement (ARM) Program has already implemented ideas
presented in the early BSRN documents. Countries presently developing radiation networks or
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