function size_to_z,bins,npb,Ze=ze
;Calculates the reflectivity for a given liquid particle size distribution
;Requires bins to be in microns and npb to be in 1/cm3.
;--------------------------------------------------------------------------

;Convert units
;-------------
b=bins/1000.		;convert to mm
n=npb*(10^6.)		;convert to 1/m3

z=total(b^6. * n)
if not(keyword_set(ze)) then z=10.*alog10(z)
return,z
end