The AMR is an enhanced version of the Jason-1 Microwave Radiometer (JMR). Like the JMR, it acquires measurements via three separate frequency channels to determine the path delay of the altimeter's radar signal due to atmospheric water vapor and liquid water in the atmosphere.

Function

The AMR measures water vapor content in the atmosphere so that we can determine how it impacts radar signal propagation. Its measurements also can be used directly for studying other atmospheric phenomena, particularly rain.

Principle

The AMR is a passive receiver that collects radiation reflected by the oceans at frequencies of 18.7, 23.8 and 34.0GHz.
Radiation measured by the radiometer depends on surface winds, ocean temperature, salinity, foam, absorption by water vapor and clouds, and various other factors. To determine atmospheric water vapor content accurately, we need to take into account sea surface and cloud contributions in the signal received by the radiometer. That is why the AMR uses different frequencies, each of which is more sensitive than the others to one of these contributions. The main 23.8-GHz frequency is used to measure water vapor; the 34-GHz channel provides the correction for non-rainbearing clouds; and the 18.7-GHz channel is highly sensitive to wind-driven variations in the sea surface. By combining measurements acquired at each of these frequencies, we can extract the water vapor and liquid water signals.