| Based on each day’s minimum ground temperature data of 62 meteorological stations from 1961 to 2010 in Shanxi Province, has analyzed yearly variation features and spatial distribution characteristics of the last frost. The results showed that: (1) The average last frost day presented an advancing trend in 1961 to 2010 with obvious wave variation, during 2001—2010 was the most volatile stage. (2) The average last frost day was Apr.12, whole distribution presented a property of early in South and late in North. The last frost day will be finished at the middle ten days in March to the middle ten days in May from the South to the North. (3) The probability of the end of normal last frost was 54%～74% in Shanxi Province. its distribution was alternately “small—large” from Northeast to Southwest, the bigger probability area was located in the Central and the Southeast. The probability of the later frost was 2%～22%, the maximal probability appeared in the South and the North. The probability of the most late frost was 14%～36%, the larger probability area was located in the Northern central region. (4) The M-K mutation test showed that the average last frost day in Shanxi Province had an obvious mutation in 1990. The last frost day in most meteorological stations had obvious mutations from 1975 to 1996. (5) The distribution of the last frost changing trend in Shanxi Province possessed apparent regional difference, from the South to the North, it appeared in altem
ately “large—small” distribution, the large advancing region was located in the Midwest and the South, the large delaying region was concentrated in the Northwest and the Mideast. (6) The primary cycle of the mild, moderate and severe last frost was 15, 12 and 7 years, respectively; the secondary cycle of the mild, moderate and severe last frost was 1, 1 and 5 years, respectively. |