Abstract: To clarify the meteorological conditions of winter wheat damaged by late frost in Henan Province, SPI and the effective accumulated temperature anomaly were taken as early water and heat factors, and the anomaly value of daily range, mean relative humidity, sunshine duration and the difference minimum temperature of the last and frost day were selected as meteorological factors when freezing. Then comparing actual late frost and index frost, K-means cluster analysis was taken and the correlation coefficients between any of two meteorological factors in different actual frost level was analyzed. The results showed that the frequency of late frost (0.64) by meteorological indices was higher than the frequency of real happened frost (0.52) in Henan province during 1964-2014. There was positive correlation between sunshine duration anomaly and daily range anomaly. The cluster analysis results with meteorological factors in early stage showed 83.3% mild actual frost correspond the weak water condition and the sufficient heat condition, 64.3% severe actual frost corresponded the weak water condition and insufficient heat condition. The cluster analysis also showed that 61.11% of mild frosts happened under dry, greater daily range of temperature, greater sunshine hours and larger difference minimum temperature between last and frost day, while 71.42% of severe frosts happened under wet, less daily range of temperature, less sunshine hours and larger difference minimum temperature between last and frost day. The results indicated that the actual frost damage was obviously different from the meteorological damage, and the correlation between meteorological factors affects the freezing injury. The actual frost was related to the insufficient water condition in the early stage, and mild frosts were more possible to be radiation frost, and most of severe frosts were mixed frost.

Key words: Winter wheat, Late frost damage, Meteorological factors, Correlation analysis, Cluster analysis