A cloud phase detector comprising: a magnetostrictive resonator configured to be affixed to an aircraft, the magnetorestrictive resonator having a baseline resonant frequency in an ice-free and liquid-water-free condition, the magnetostrictive resonator configured to resonate at a resonant frequency indicative of a measure of ice accretion upon an exterior surface of the magnetostrictive resonator; and a liquid-water detection system configured to generate a signal indicative of liquid-water content of an aircraft surface, the liquid-water detection system comprising: a frequency detector configured to detect the resonant frequency f R of the magnetostrictive resonator; a noise detector configured to detect temporal variations of the resonant frequency of the magnetostrictive resonator; and a processor configured to: calculate a running mean resonant frequency f R, as the mean value of a certain number of last measured resonant frequencies; compare the running mean resonant frequency f R with an established baseline resonant frequency; calculate a temporal variation of the resonant frequency f N 2 = ∑ N f R N − f R ̅ 2 and a measure of noise f N; compare the calculated noise f N of the resonant frequency with a predetermined threshold; generate a signal indicative of liquid-water content on the aircraft surface, wherein the generated signal indicative of liquid-water content is zero if the compared running mean resonant frequency is not less than the determined baseline resonant frequency and the compared noise is not greater than the predetermined threshold, and wherein the generated signal indicative of liquid-water content on the aircraft surface is greater than zero if the compared noise is greater than the predetermine threshold. a magnetostrictive resonator configured to be affixed to an aircraft, the magnetorestrictive resonator having a baseline resonant frequency in an ice-free and liquid-water-free condition, the magnetostrictive resonator configured to resonate at a resonant frequency indicative of a measure of ice accretion upon an exterior surface of the magnetostrictive resonator; and a liquid-water detection system configured to generate a signal indicative of liquid-water content of an aircraft surface, the liquid-water detection system comprising: a frequency detector configured to detect the resonant frequency f R of the magnetostrictive resonator; a noise detector configured to detect temporal variations of the resonant frequency of the magnetostrictive resonator; and a processor configured to: calculate a running mean resonant frequency f R, as the mean value of a certain number of last measured resonant frequencies; compare the running mean resonant frequency f R with an established baseline resonant frequency; calculate a temporal variation of the resonant frequency f N 2 = ∑ N f R N − f R ̅ 2 and a measure of noise f N; compare the calculated noise f N of the resonant frequency with a predetermined threshold; generate a signal indicative of liquid-water content on the aircraft surface, wherein the generated signal indicative of liquid-water content is zero if the compared running mean resonant frequency is not less than the determined baseline resonant frequency and the compared noise is not greater than the predetermined threshold, and wherein the generated signal indicative of liquid-water content on the aircraft surface is greater than zero if the compared noise is greater than the predetermine threshold. a frequency detector configured to detect the resonant frequency f R of the magnetostrictive resonator; a noise detector configured to detect temporal variations of the resonant frequency of the magnetostrictive resonator; and a processor configured to: calculate a running mean resonant frequency f R, as the mean value of a certain number of last measured resonant frequencies; compare the running mean resonant frequency f R with an established baseline resonant frequency; calculate a temporal variation of the resonant frequency f N 2 = ∑ N f R N − f R ̅ 2 and a measure of noise f N; compare the calculated noise f N of the resonant frequency with a predetermined threshold; generate a signal indicative of liquid-water content on the aircraft surface, wherein the generated signal indicative of liquid-water content is zero if the compared running mean resonant frequency is not less than the determined baseline resonant frequency and the compared noise is not greater than the predetermined threshold, and wherein the generated signal indicative of liquid-water content on the aircraft surface is greater than zero if the compared noise is greater than the predetermine threshold.