The Frost Characteristics in Ningxia in the Recent 44 years

Based on the data of the day minimum temperature and the ground temperature of 20 meteorological observation stations of Ningxia from 1961～2004,the indication of frost was set.The results showed that the frequencies of frost in Ningxia declined obviously in the near 44a,the probability was of the spring frost higher than the autumn frost,the absolute variability of the last frost date in majority stations was larger than that of the first frost date.The frequency of frost correlated positively with the altitude,negatively with the growing season and the annual minimum temperature.The frost frequency that lasted over 2 days accounted for 1/3,most durations was 5~6d.The continuous frosts were mainly the local frost.Although the entire district frost had the probability less than 1/5,the harms was very serious.The spring frost and the autumn frost occurred differently with the region in the agronomic key period.