Study On Monitoring Late Freezing Disaster In Winter Wheat By Remote Sensing

Degrees and days of late freezing disaster of winter wheat in Henan province is performed by means of EOF and Morlet analysis through creating the index of freezing disaster on the basis of previous researches. The results show that the occurring rate of late frost disaster is 47.7%, and is getting more frequently than before. The serious degree areas of late freezing disaster mainly distribute the south-east and the south-west of Henan province, and the low degree areas are at the southern places of Huaihe river as well as the west of Henan province etc. The Morlet analysis indicates that there is a 2-4-year period in 1970s to 1990s, and there is another 12-year and longer period. The high number center of days of late frost disaster appears in the middle and the east and the south of Henan province, and the low number center is in the north-east and the west, and the results by Morlet conveal that there exists a 2-4-year cycle in 1980s-1990s.The calculating methods of wheat development period in grids and the minimum ground temperature are developed based on crop data and remote sensing data in order to monitor qualificationally late frost disaster of winter wheat. To reckon wheat growth date in grids, at first the potential temperature and air pressure in grids is computed by the potential temperature equation and the state equation, then the temperature in grids is counted, finally the elong date of winter wheat in grids is calculated according to the accumulated temperature model of development period. The results convey that this way of indirect calculating temperature makes error decrease after potential temperature and air pressure is computed. During counting the minimum ground temperature by remote sensing, the best method is put forward after different split window algorithm methods given out by the previous researchers are validated and compared. The error further diminishes after using variational technique. It shows that the different errors of several split window algorithm means are...