Origin of the data

Origin of the solar data

The Solargis WS API delivers essential solar data parameters, including GHI (Global Horizontal Irradiance), DNI (Direct Normal Irradiance), and DIF (Diffuse Horizontal Irradiance), which form the foundation for solar resource analysis.

It also provides calculated parameters like GTI (Global Tilted Irradiance) and PVOUT (Photovoltaic Power Output) to support advanced solar energy modeling and project optimization.

The tabs below provide information on how solar data is integrated into the API response of the Time series API endpoint.

Tracking data origin with CI_FLAG

Within the Solargis WS API, you can determine the origin of solar data by requesting the CI_FLAG parameter (Cloud Identification Quality Flag - i.e. from which source Solargis obtained the cloud situation) in your XML request. The API response labels each data record with one of the following categories:

This system ensures transparency in data provenance, critical for validating solar analyses in your applications.

Recommendation: For accurate interpretation, use CI_FLAG values with the highest solar data resolution (15 or 10 minutes) to ensure granular insights into data quality and source.

Reanalysis of solar data

Solargis ensures high data accuracy through systematic processing of historical and operational solar data. Here's how the timeline works:

Daily reanalysis of DAY-2

• Every day, solar irradiance data is actually calculated for two days: DAY-1 and DAY-2, so that the DAY-2 gets its first reanalysis.

Monthly reanalysis of MONTH-1

At the start of each calendar month (not before 3rd calendar day of the month):

• Solar irradiance data for the previous month is recalculated using finalized atmospheric inputs.

• Atmospheric data is homogenized with historical records to maintain consistency and prevent abrupt changes caused by updates to atmospheric models.

Note: This process ensures long-term data reliability for historical and operational stages.

For a deeper dive into atmospheric data homogenization and reanalysis methods, refer to our Methodology.

Spatial availability of the satellite data

The availability and update frequency of solar data depend on the region, as shown in the image below:

• Orange regions: Data is updated every few minutes, providing access to satellite-based real-time and nowcasting models for the current day.

• Yellow regions: Data is updated daily, ensuring DAY-1 data (the previous day's data) is available.

For detailed timing and descriptions of satellite data regions, refer to the table in Satellite data resources overview chapter.

Satellite data resources overview

The section provides an overview of the satellite data regions used in the Solargis WS API, detailing their historical data availability, satellite characteristics, update timing for DAY-1 data, and real-time or nowcasting capabilities. Use the accompanying map to locate specific regions and understand their data coverage and update frequency.

To request historical data in the areas out of coverage, please use Solargis Evaluate or contact us.

Nowcasting data availability and delay

The total delay of near real-time data combines three factors: satellite data availability delay, data processing delay, and user request delay after processing is complete.

1. Satellite data availability delay varies by latitude and satellite region:

   • PRIME, IODC: 2–16 minutes (increases from north to south)

   • HIMAWARI: 5–15 minutes (increases from south to north)

   • GOES EAST & WEST: 2–12 minutes (increases from south to north)

2. Data processing delay, which includes retrieval, preprocessing, and running the nowcasting model, takes 5–15 minutes. Data becomes accessible immediately after processing is finished.

3. Processing frequency depends on the satellite region:

   • HIMAWARI, GOES EAST & WEST: Every 10 minutes

   • PRIME, IODC: Every 15 minutes

This frequency determines the window for delivering a given nowcast run before it is replaced by the next. The timing of a user’s request during this interval introduces the user request delay, ranging from 0–10 minutes (for 10-minute regions) or 0–15 minutes (for 15-minute regions).

Nowcasting and forecasting update frequency

The map below illustrates the geographical availability of Solargis data, highlighting the update frequencies for short-term nowcasting and forecasting data across different regions. It shows areas with 5-, 10-, and 15-minute updates using Solargis CMV models, alongside regions covered by NWP models with 6-hourly or 1-hourly updates.

Origin of the meteorological data

The Solargis WS API provides key meteorological data parameters, including TEMP (Temperature), WS (Wind Speed), WG (Wind Gusts), WD (Wind Direction), PREC (Precipitation), RH (Relative Humidity), PWAT (Precipitable Water), and AP (Air Pressure). These parameters are derived from the post-processed outputs of global Numerical Weather Prediction (NWP) models to ensure high accuracy and reliability.

The table below outlines how meteorological data is integrated into the API response for the Time series API endpoint.:

You can find more information about forecasting here.