What is defined as the standard deviation of the Doppler spectrum?

The standard deviation of the Doppler spectrum is referred to as the spectrum width. Spectrum width is a critical parameter in radar meteorology as it quantifies the spread of Doppler velocities present in the radar return signal, which can be indicative of turbulence or the presence of multiple scatterers moving with different velocities within a given volume of air.

Higher spectrum width values often suggest a wider range of velocities, which can point to turbulent conditions, while lower values indicate more uniform motion among scatterers. In Doppler radar applications, understanding spectrum width can help meteorologists assess storm attributes, including the potential for severe weather phenomena.

The other options relate to different aspects of the Doppler spectrum. The first Doppler moment pertains to the mean Doppler velocity, while the 0th Doppler moment corresponds to the total power or reflectivity of the return signal. Variance of the Doppler spectrum, although a relevant concept, is not directly synonymous with standard deviation; rather, standard deviation is the square root of variance. Thus, spectrum width is the most accurate term for the standard deviation of the Doppler spectrum.