| Name | Type | Country | Components |
|---|---|---|---|
| SMEAR I (Värriö) | Observational platform | Finland | 3 |
| SMEAR IV (Kuopio) | Observational platform | Finland | 2 |
| Sofia (IE-BAS) | Observational platform | Bulgaria | 1 |
| Sonnblick Observatory (SBO) | Observational platform | Austria | 2 |
| Strzyżów (ACTRIS ICOS collocated station) | Observational platform | Poland | 1 |
| Suchdol | Observational platform | Czechia | 1 |
| Svartberget | Observational platform | Sweden | 2 |
| Taunus Observatory | Observational platform | Germany | 2 |
| Trollhaugen | Observational platform | Norway | 2 |
| Turbulent Leipzig Aerosol Cloud Interaction Simulator (LACIS-T) | Atmospheric simulation chamber | Germany | 2 |
