Abstract: The law in the variation of the subtropical high ridge line in July and the cause to its formation were analyzed in the paper. The results indicate that the location of the subtropical high ridge line has an significance low-frequency variation. The cycle period of its oscillation covers about thirteen years. The variation is characterized with a teleconnection structure at 500hPa in East Asia. The effective factors are mainly concerned with the apperence of the atmospheric blocking over the East Asia , SST in the region of block current, convective activites surrounding the Philip-pins and the subtropical high over the southern Indian Ocean.
Abstract: The canopy-air temperature-difference models, RW = a + b (Tc-Ta), for wheat, corn and cotton, and the soil-air temperature difference model, RW = a' + b'(Ts -Ta), for bare soil were developed based on the data observed in Handan area in 1990 and 1991. The average relative error was less than 20%. The models are simple and easy to be used for irrigation management and drought monitoring over large areas. The method of crop coverage calibration for the canopy temperature and the temperature-difference indexes of the drought grades were also presented in this paper.
