Satellite instruments' sensitivity
For climatological and hydrological purposes it would be useful to know the areal extent of snow, its water equivalent, grain size, density and presence of liquid water. However, these properties cannot be measured directly by remote sensing systems. Satellite instruments measure radiation in certain ranges of the electromagnetic spectrum, and with the correct processing techniques this data reveals properties of the snow cover (Table 1).
Table 1: Satellite instruments' sensitivity to various snowpack properties in different regions of the electromagnetic spectrum (adapted from WMO CHy-14, 2012).
| Region of electromagnetic spectrum | ||||
|---|---|---|---|---|
| Snow property | Gamma rays | Visible/NIR | Thermal infrared (IR) | Microwaves |
| Snow-covered area | Low | High | Medium | High |
| Depth | Medium | If very shallow | Low | Medium |
| Water equivalent | High | If very shallow | Low | High |
| Stratigraphy | No | No | No | High |
| Albedo | No | High | No | No |
| Liquid water content | No | Low | Low | High |
| Temperature | No | No | Medium | Low |
| Snowmelt | No | Low | Low | Medium |
| Snow-soil interface | Low | No | No | High |
| Additional characteristics | ||||
| Surface seen through clouds, day and night | No | No | No | Yes |
| Current best spatial resolution from space platform | Not possible | 10 m | 100 m | 25 km passive 10 m active |