bands are regularly used for monitoring of weather and even forecasting through data
assimilation in numerical models. Similarly, oceanic waves are remotely sensed to
forewarn ships, offshore industries and fisheries for avoidance of days with expected
rough sea-states. Monitoring and predicting of Cyclone track and intensity is a glaring
example of utility of Remote Sensing. Variations in polar snow covers, well-known in
Climate Change context, are important information retrieved from Remote Sensing
data.
Credit: "Remote Sensing Illustration" by Arkarjun (Wikimedia Commons)
Sonali: How are physical parameters retrieved from observations made from space
platforms?
Dr. Sarkar: Science of Retrieval of physical parameters of Earth systems are based
on several principles of Physics. Different objects with varying Emissive properties
and temperature radiate in different wavelengths with varying intensities (well-known
Planck’s Radiation Law). In fact this
helps in discriminating different objects.
During the passage of radiation from earth-atmosphere system to space, it gets altered
due to Absorption and Scattering. Mathematical representation of these processes are
however not very straight-forward. The atmosphere is known to be a layered
(stratified) medium and hence, the contributions of different layers in emission,
multiple reflection and scattering need to be modelled. This calls for knowledge of
distribution (horizontal and vertical) of the constituents and their electromagnetic
properties. The electromagnetic radiation received at the satellite sensor (operating at
certain frequencies) will be complex functions of the emission from the source.
Inversion of these received radiations into the source properties is a challenging task.
This is achieved by advanced statistical techniques and physics-based modelling of