Vaisala Energy Support

What Is The Vaisala 1.1 Dataset?

The Vaisala 1.1 dataset is the second dataset created by Vaisala, then 3TIER. The main change over the V1.0 dataset was increasing the number of channels used from MODIS for aerosol inputs to four and still uses monthly averages.

The clear sky model used is the Perez SUNY v1.0 methodology, the same as contained in this reference (hereafter referred to as Perez v1.0): R. Perez et al, “A new operational model for satellite-derived irradiances: description and validation”, Solar Energy, Vol. 73, Iss. 5, November 2002, pages 307-317

The primary difference is that the Linke coeffificent used is derived using a Vaisala proprietary method incorporating the MODIS AOD and Water Vapor dataset mentioned above, using Ineichen's “Conversion function between the Linke turbidity and the atmospheric water vapor and aerosol content.” Solar Energy, 82, 1095-1097.

Vaisala uses a proprietary Cloud Index calculation methodology. To derive the Cloud Index the satellite measurements are first processed to account for instrument degradation over time. The proprietary Vaisala cloud algorithm is the main deviation from the Perez SUNY irradiance calculation methodology. It works by dividing the satellite measurements into bins by solar azimuth and zenith angle, and treating each bin independently, for the calculation of a cloud index. The fit between cloud index, clear-sky GHI, and observations is done on a per satellite basis.

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