someone told me that is trying to detect vapor content in the plume, for example in a volcanic eruption, computing the NDWI…Is that correct? NDWI should be specifically used for vegetation water content…am I wrong? @ABraun probably could help
To my experience, the NDWI is not aiming at atmospheric humidity. But two different definitions exist, one for water bodies and one for vegtetation water.
- McFeeters (1996): The use of Normalized Difference Water Index (NDWI) in the delineation of open water features. International Journal of Remote Sensing 17(7), 1425-1432. URL
- Gao (1996) NDWI - A normalized difference water index for remote sensing of vegetation liquid water from space. Remote sensing of environment 58 (3), 257-266. PDF.
As you see, one uses infra IR/SWIR and the other green/IR. Both are normalized ratios however. None of them is suitable for atmospheric water. Sentinel-2 features some cirrus information which could be used: https://earth.esa.int/web/sentinel/user-guides/sentinel-2-msi/processing-levels/level-2
that is also my knowledge, but I wanted a reliable double check thanks!!