Heliosat (SARAH)

Screenshot from windprospecting.com showing coverage of the Heliosat (SARAH) dataset.

Introduction

"Heliosat (SARAH)" is a satelite based surface solar irradiance dataset: The raw data are produced and delivered by EUMETSAT CM SAF (Satellite Application Facility on Climate Monitoring) - https://www.cmsaf.eu/. This windPRO 'Heliosat' dataset is a merge of two different datasets, namely:

• Surface Radiation Data Set - Heliosat (SARAH) - Edition 2.1:
  This dataset covers the period from 1999-01-01 to 2017-12-31 - see documentation here.
• ICDR SEVIRI Radiation - based on SARAH-2 methods:
  This dataset is an operational dataset that covers the period from 2018-01-01 to present - see documentation here

A validation report of the ICDR dataset concludes that there is a resonable consistency between the two datasets, see here.

Dataset Overview

• Content: Surface radition parameters to be used in solar calculations in windPRO
• Spatial Resolution: The dataset is available on a regular geographical (lat/lon) grid at 0.05x0.05 resolution (around 5 km).
• Temporal Resolution: 30 minute values.
• Coverage: The dataset has an extend +- 65 degrees in both latetidues and longitudes. In windPRO, offshore coverage is at a distance of approximately 300 km from any known coastlines.
• Period: 20+ years. The EMD databases will hold data back to 1999.
• Availability: This dataset requires a windPRO version 3.4+

Validation and Usage Notes

• This dataset seems hold only older data (until 2017-12-31)?
  Yes, this dataset (SARAH-2) is no longer being updated forward in time. It is replaced by the SARAH-3 datasets, which is also available in windPRO and the SOLAR-PV module. See here: SARAH-3
• How accurate is your surface solar irradiation data from SARAH-2 and SARAH-3- when used in windPRO and the SOLAR-PV module?
  We have prepared a small validation note - based on data from 18 in-situ measurements in Denmark and are also comparing against the global solar atlas as a reference dataset. This is intended to give hints on bias and uncertainty - and to compare to the other datasets often used: ERA5 and SARAH-2. Read more - HERE.

Availability from within windPRO

The data can be accessed and used from windPRO in the following objects:

• Meteo object (data container - online service for obtaining data)
• Solar PV object (calculation tool)

Data Parameters

The windPRO dataset only contains parameters needed for solar calculations. These parameters are listed below.

Table: Overview of the Heliosat (SARAH) parameters.

Parameter	Unit	Description
time		UTC time stamp (half hourly)
SIS	w/m2	Surface Incoming Shortwave Irradiance
SID	w/m2	Surface Irradiance Direct

All parameters are instantaneous. The two parameters SIS and SID can be used to calculate the diffuse radiation as SIS-SID = diffuse radiation.

Required Modules/Licenses

To access the Heliosat (SARAH) data from within windPRO - the following licenses/modules are required in your windPRO setup:

• BASIS
• SOLAR

When the license fee is paid, you then have access to the full dataset without further cost.
Downloading of data is unrestricted for licenced users with an active service subscription, however, a "fair use" policy applies. Visit EMD online ordering to purchase the necessary licences.

Attribution

If data from this dataset is used within any private or public disseminations, then EMD and its data providers must be acknowledged.

Source: 
Heliosat (SARAH). Distribution through EMD and windPRO - EMD International A/S, 2020.
This dataset uses Heliosat (SARAH) data which is being developed by 
EUMETSAT CM SAF (Satellite Application Facility on Climate Monitoring) - see https://www.cmsaf.eu/.

External Links

• EUMETSAT CM SAF (Satellite Application Facility on Climate Monitoring) - https://www.cmsaf.eu/