Vaisala Energy Support
What is the Vaisala 2.0 dataset?
The Vaisala 2.0 dataset is the first dataset Vaisala created using the new REST2 clear sky algorithm and uses the ECMWF-MACC (Monitoring Atmospheric Composition and Climate) product as the source of the aerosol and water vapor inputs.
The REST2 model is a parameterized version of Dr. Gueymard's SMARTS radiative transfer model, as described in C. A. Gueymard, "REST2: High-performance solar radiation model for cloudless-sky irradiance, illuminance, and photosynthetically active radiation – validation with a benchmark dataset," Solar Energy, vol. 82, pp. 272-285, 2008.
We are using version 9.0 of the REST2 clear sky code. Defaults are currently used for ozone, albedo, single scattering albedo, and asymmetry parameter values. Vaisala 2.0 uses ECMWF-MACC as the source for aerosol optical depth (AOD) and precipitable water.
Whether the Perez or REST2 clear sky model is used, GHI is calculated by modulating the clear sky GHI values by the cloud index values to calculate the cloudy sky GHI value. In the Perez model, DNI is calculated from GHI using Dr. Perez's DIRINT methodology. In the REST2 model, a second modulation function is used to calculate DNI from the cloud index and the clear sky DNI value. Diffuse is then calculated from the GHI and DNI values and solar zenith angle.
Vaisala uses a proprietary cloud index calculation methodology to compute cloudy sky irradiance. To derive the cloud index, the satellite radiance measurements are first processed to account for instrument degradation over time. The Vaisala cloud algorithm then divides the satellite measurements into bins by solar azimuth and zenith angle, and treats each bin independently for the calculation of a cloud index. The fit between cloud index, clear-sky GHI, clear-sky DNI, and observations is done on a regional basis.
More Solar Online Tools Questions
- How accurate is the data in the Solar Time Series Tools?
- The datasets give different answers. Which one is right?
- Why are there so many (5) different versions of solar data?
- Which weather data source should I pick?
- Why do the values in my TMY file change?
- What updates were applied to the datasets in November 2019?
- What's the latest month available in the solar time series tool?
- What solar values are shown on the map in solar prospecting and solar time series tool?
- How do I enter a location?
- Why does the map disappear?
- How do I interpret the graphs provided by the Monthly Mean Irradiance Tools in the Prospecting Tools?
- What do the Annual Mean Irradiance Tools in the Prospecting Tools provide?
- How can I compare sites side-by-side in the Prospecting Tools?
- How much area is covered by the Solar Prospecting Tools?
- How accurate are the Solar Prospecting Tools?
- What data is shown in the Solar Time Series Viewer?
- What data can I get from the Solar Time Series Download tool?
- What is the Vaisala 1.0 dataset?
- What is the Vaisala 1.1 dataset?
- What is the Vaisala 1.2 dataset?
- What is the Vaisala 2.1 dataset?
- What are the units of irradiance?
- What is the “TMY” Data Type in the Solar Time Series Download tool?
- What is the “Long-Term” Data Type in the Solar Time Series Download tool?
- Why does the data not match my observations?
- How do I input CSV files into PVSyst?
- How can I input time series data into PVSyst?
- What is Global Horizontal Irradiance?
- What is Direct Normal Irradiance?
- What is Diffuse Horizontal Irradiance?
- What affects solar radiation at a given site?
If you didn't find what you were looking for, please contact 3TIER Support for additional assistance.