| The Penman-Monteith, Blaney-Criddle, Hargreaves, Prestley-talylor and Markkink formula are used to compute ten-day and daily crop evapo-transpriations (ET0) with 30-year ten-day meteorological data collected by Baotou meteorological station and the daily data of crop growth of 2001 collected by Baotou meteorological station, and the results of the computation by the Penman-Monteith formulae is used to evaluate the computations by the other four formula. The ten-day ET0s computed with the Penman-Monteith formulae and the other formula all has very good correlativity and the ten-day ET0 by the Blaney-Criddle formulae is better than those by the other formulae. The daily ET0s computed by the four formula show relatively big errors and the daily ET0 computed by the Markkink formula is better than the ET0s computed by the other formula. Meanwhile, the relation between the ET0 and atmospheric temperature is analyzed and empirical formulae suitable to compute the ET0 in the regions under question is established. The computation by the empirical formulae to compute the ET0s is simple and accurate. |