Campaign : Diffuse Shortwave IOP

2001.09.24 - 2001.10.22

Data Availability

Data will not be available for public viewing until April 8, 2002. All data will be archived at the diffuse IOP web site by that date.

For data sets, see below.

Summary

Almost 4 weeks of data were acquired under mostly sunny skies. Ninety-two percent of the daylight hours had measureable direct beam radiation. Much of the sunny data included completely cloud free conditions. The trackers functioned perfectly. Clear-sky data included low to moderate aerosol cases with no high aerosol conditions sampled. Data recovery from the pyranometers was near 100%. Absolute cavity data were acquired on the first 7 days of the IOP. Some completely overcast data were available on a few days to test the instruments behavior relative to those conditions as well as the clear sky conditions. Data are still being analyzed.

Description

Scientific hypothesis: There is no absolute standard for diffuse horizontal irradiance measurements as there is for the direct beam irradiance. In lieu of an absolute standard, we were interested in the level of agreement that one could achieve by comparing a wide assortment of current instrumentation measuring skylight simultaneously for both clear and overcast situations. The main motivation for this need to improve the diffuse measurement is the persistent overestimation of clear-sky models relative to measurements.

Approach to test hypothesis: We sought voluteers to take part from the ARM, BSRN, and manufacturing communities. We chose early fall conditions because that time of year has been dependable with regard to having both clear and cloudy conditions needed for these comparisons. The pyranometers were mounted on five Sci-Tec trackers providing space for up to 14 instruments. The instruments were pre- and/or post-calibrated by their providers. Any corrections suggested by the providers were implemented before comparing data.

Additional Information

See

article by Jeffries

Campaign Data Sets

Campaign Participant	Data Set	Archived Data
Dolce, Robert	Kipp & Zonen CM11	Order Data
Dutton, Ellsworth	EKO MS-801	Order Data
Haeffelin, Martial	CIMEL B&W	Order Data
Haeffelin, Martial	Modified Eppley PSP	Order Data
Hickey, John	Eppley New B&W	Order Data
Jeffries, William	Yankee Isothermal Pyranometer	Order Data
Major, Gyorgy	Budapest University	Order Data
Mathias, David	Carter-Scott design EQ08-A	Order Data
McArthur, Bruce	Schenk Star	Order Data
McArthur, Bruce	Kipp & Zonen CM21	Order Data
Philipona, Rolf	Kipp & Zonen CM22-PMOD Vent	Order Data
Slater, Donald	TMI Cavity	Order Data
Stoffel, Tom	Eppley 8-48	Order Data
Stoffel, Tom	NREL Eppley PSP	Order Data
Valero, Francisco	RAdiation Measurement System (RAMS)	Order Data