Solar Suitability Index (SSI™) – Classification (Levels 1–7) Regional
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Map Information
A classified continental solar suitability index (1-7) dividing conditions into seven discrete levels for simplified interpretation and decision-making. The Solar Suitability Index closely aligns with independent estimates of solar energy performance, indicating strong reliability as a global screening metric.
Data Legend
Location Analysis
Technical Specifications
Regional Solar Suitability Index (SSI™) – Classification (Levels 1–7)
Global | ~1 km Resolution | 2020–2024
Raster Name
Global Solar Suitability Index (SSI™) – Classification (Levels 1–7)
File Name
solar_suitability_index_2020_2024_master_1km_class_v2.tif
Short Description
A classified global solar suitability dataset representing the relative favorability of locations for solar energy development using seven discrete categories derived from the continuous Solar Suitability Index (SSI™).
Units of Measure
Classification Level (1–7, ordinal)
Technical Specification
This dataset represents a classified interpretation of the continuous Solar Suitability Index (SSI™), developed by AtmosphericIQ LLC using a proprietary multi-parameter analysis of atmospheric and radiative conditions derived from ERA5 reanalysis data.
The classification groups the continuous SSI™ surface into seven discrete categories using fixed threshold ranges applied globally.
SSI™ ∈ [0, 100]
The classification is intended to support:
- Rapid site screening
- Engineering decision-making
- Portfolio comparison
- Web-based visualization and scoring workflows
Classification Framework
The discrete classification is derived from the continuous index using fixed threshold ranges:
Class = f(SSI™)
| Class | SSI™ Range | Suitability Level | General Interpretation |
|---|---|---|---|
| 1 | 0–<30 | Very Low | Poor solar resource conditions with severe atmospheric limitations |
| 2 | 30–<40 | Low | Limited solar viability due to persistent atmospheric constraints |
| 3 | 40–<50 | Moderate-Low | Reduced solar potential influenced by clouds, humidity, or temperature |
| 4 | 50–<60 | Moderate | Viable solar resource with noticeable atmospheric effects |
| 5 | 60–<70 | High | Strong solar resource typical of high-performing regions |
| 6 | 70–<80 | Very High | High-quality solar resource found in globally favorable dry climates |
| 7 | 80–100 | Exceptional | Top-tier global solar resource observed in the best desert and arid environments |
These classification thresholds are fixed and globally consistent, allowing direct comparison across geographic regions.
Under the current 2020–2024 climatology, observed SSI™ values typically range from approximately 15 to 84, with the highest-performing global solar environments occurring within Classes 6 and 7.
Key Characteristics
- Discrete global classification with ordinal values from 1 to 7
- Higher classes indicate more favorable solar resource conditions
- Lower classes indicate reduced solar potential due to atmospheric or environmental limitations
- Derived directly from the continuous Global Solar Suitability Index (SSI™) – Continuous Score (1–100)
Spatial Characteristics
- Coordinate System: GCS_WGS_1984
- Spatial Resolution: ~1 km
- Coverage: Global (±85.0511° for web compatibility)
Processing
The SSI™ dataset was developed by AtmosphericIQ LLC and processed for distribution and deployment by Engineering Director, Inc.
The continuous Global Solar Suitability Index (SSI™) raster was classified into seven discrete levels using fixed threshold ranges applied globally:
SSI™class = f(SSI™continuous)
The classified raster was exported as an integer GeoTIFF to optimize web tile rendering performance, storage efficiency, and categorical visualization workflows.
Model Validation
The Solar Suitability Index (SSI™) was evaluated against independent solar performance datasets to confirm its reliability as a global screening and comparison tool.
Validation Approach
Validation was performed by comparing SSI™ values against the Global Solar Atlas photovoltaic power potential (PVOUT) dataset, which represents long-term average solar energy production potential (kWh/kWp) based on independent modeling methodologies.
A set of 9,864 globally distributed sample points was generated, and SSI™ values were extracted and compared directly with PVOUT values after spatial alignment to a common grid.
Validation Results
- Pearson Correlation (r): 0.929
- Coefficient of Determination (R²): 0.863
- Sample Count: 9,864
Interpretation
The results demonstrate excellent agreement between the Solar Suitability Index (SSI™) and independent photovoltaic performance estimates.
An R² value of 0.863 indicates that the SSI™ explains approximately 86% of the variation in photovoltaic power potential globally. This confirms that the SSI™ effectively captures the combined influence of solar irradiance, atmospheric attenuation, and environmental conditions on solar energy suitability.
Model Behavior
The SSI™ correctly identifies high-suitability regions such as:
- Sahara Desert
- Arabian Peninsula
- Atacama Desert
- Southwestern United States
- Interior Australia
It also identifies lower suitability regions characterized by:
- persistent cloud cover
- high atmospheric moisture
- elevated humidity or temperature constraints
This spatial consistency further supports the physical validity of the model.
Scope and Intended Use
The Solar Suitability Index (SSI™) is a relative scoring model designed for:
- global solar resource screening
- comparative site evaluation
- portfolio analysis
- geospatial decision support
The classified SSI™ dataset is not intended to predict exact system output, but rather to provide a normalized, globally consistent categorical measure of solar suitability based on climatological conditions.
Data Access & API Services
The SSI™ dataset is developed by AtmosphericIQ LLC and made available through Engineering Director, Inc. platforms.
Interactive map access, API integration, bulk-scoring, and enterprise lookup services are available at:
www.engineeringdirector.com
Use of the SSI™ dataset beyond visual interpretation, including API access, bulk-scoring, automated queries, or integration into external systems, is subject to the Engineering Director API Terms of Service.
Related SSI™ Datasets
Additional Solar Suitability Index (SSI™) products are available at multiple classification levels and spatial extents.
-
Regional Solar Suitability Index (SSI™) – Index (1–7)
View Interactive Map
Regionally clipped categorical suitability dataset for focused analysis. -
Global Solar Suitability Index (SSI™) – Index (1–7)
View Interactive Map
Discrete global classification derived from the continuous SSI™ model. -
Global Solar Suitability Index (SSI™) – Continuous Score (1–100)
View Interactive Map
Full-resolution continuous global suitability model.
Supporting Climatic Input Layers
The following climatic layers represent key environmental inputs used in the development of the Solar Suitability Index (SSI™) model. These layers are provided as companion visualization datasets.
All SSI™ datasets are derived from a proprietary multi-parameter model developed by AtmosphericIQ LLC.
-
Global Horizontal Irradiance (GHI – Mean Irradiance)
View Interactive Map -
Clear-Sky Global Horizontal Irradiance (GHIcs)
View Interactive Map -
Beam Horizontal Irradiance (BHI – Mean Irradiance)
View Interactive Map -
Clear-Sky Beam Horizontal Irradiance (BHIcs)
View Interactive Map -
Total Cloud Cover (TCC)
View Interactive Map -
Total Column Water Vapour (TCWV)
View Interactive Map -
2-Meter Air Temperature (T2M)
View Interactive Map -
Surface Pressure (SP)
View Interactive Map -
Wind Speed
View Interactive Map -
Mean Annual Relative Humidity (RH)
View Interactive Map
Legal & Licensing
© 2026 AtmosphericIQ LLC and Engineering Director, Inc. All rights reserved.
SSI™ is a trademark of Engineering Director, Inc.
This dataset and associated models are proprietary to AtmosphericIQ LLC and distributed by Engineering Director, Inc.
No part of the SSI™ dataset may be reproduced, distributed, or used for commercial purposes without prior written permission from AtmosphericIQ LLC or Engineering Director, Inc.
The SSI™ dataset is provided "as is" without warranty of any kind. AtmosphericIQ LLC and Engineering Director, Inc. make no representations regarding accuracy, completeness, or fitness for a particular purpose. Users assume all risk associated with its use.
Dataset Citation
Mazzella, J. (2026).
Global Solar Suitability Index (SSI™) – Classification (Levels 1–7), 2020–2024.
AtmosphericIQ LLC / Engineering Director, Inc.
Based on ERA5 reanalysis data:
Hersbach, H., et al. (2020).
The ERA5 global reanalysis.
Quarterly Journal of the Royal Meteorological Society, 146(730), 1999–2049.
ECMWF Copernicus Climate Data Store (CDS)
https://cds.climate.copernicus.eu
Data Distribution Analysis
These histograms show the distribution of pixel values across the entire raster dataset, helping you understand the range and frequency of different measurements.