Study On Effect Of Meteorological Environment On Wheat Powdery Mildew And Long-Term Forecast

Using the atmospheric general circulation characteristic indexes and surface data obtained easily to study the relationship between epidemic of wheat Powdery mildew and atmosphere general circulation and meteorological condition, to study the possible influencing mechanism, select circulation indexes and surface indexes affecting the epidemic of wheat Powdery mildew in China and in the Changjiang valley, then establish long-term forecasting models with which the three-year-extending forecast is made, and the result tallies with the real, which indicates that the forecasting models have better extension effect.The circumfluence background affecting the epidemic of wheat power mildew is posted; the correlation study between the epidemic and 74 circulation characteristic indexes indicate: (1) In china, in the year of heavy occurrence of wheat power mildew, the monthly average of area index of Northern Hemisphere polar vortex from last Jan. to this Mar. is 33 less than the monthly average of many years during the same period; the monthly average of Eurasian meridional circulation index from last Jul. to this Jan. is 7 less; the Indiaburman trough index in last Aug. is 9 more; the monthly average of area index of West Pacific Subtropical high from last May. to this Mar. is 5 more. The impact of Northern Hemisphere polar vortex area and Eurasian meridional circulation on the epidemic of wheat power mildew is negative, while the impact of Indiaburman trough and West Pacific Subtropical high area is positive. (2) In Changjiang valley, in the year of heavy occurrence of wheat power mildew, the monthly average of Asia polar vortex area index in last Aug. is over 25 less than the monthly average of many years during the same period; the monthly average of Tibet altiplano index from last Mar. to last Jul. is over 5 higher; the center location of Northern Hemisphere polar vortex in last Nov. to this Jan. is far too from China; the sunspot index in last Dec. is 800 higher; the monthly average of intensity index of North America Atlantic Subtropical high from last May. to last Jul. is about 32 higher; the position of South China Sea Subtropical high ridge line is partial to north about 1 -2 1at.; the numbered typhoons in last May. are more than 3. In the year of light occurrence of wheat power mildew, the monthly average of Eurasian meridional circulation index from last Jul. to last Aug. is 3 less than the monthly average of many years during the same period.The key periods > key factors and indexes of the meteorological condition affecting the epidemic of wheat Powdery mildew in Changjiang valley are selected, the results indicate: (1) The key period is Apr. and from the last dekad of Dec. to the last dekad of Feb.; in which the impact of spring is important than winter. (2) With the increase of rainfalls during the winter key period and the middle rainfalls during the spring key period, and the decrease of average temperature in winter during the spring key period, the occurrence degree will enhance obviously. (3) The corresponding indexes under different occurrence degrees which tally with the real after being tested. (4) During the whole growth period, the epidemic degrees increase with the enhance of average wind speed. The maximum temperature and ground surface temperature have negative correlation with disease.The possible mechanism of climatic background affecting wheat Powdery mildew is studied.The increase of sunspot may make the rainfall enhance in Jan. in Changjiang valley. The nearer the Northern Hemisphere polar vortex is away from China in last Nov. to last Dec., the less the rainfall in the middle and last dekad in this Jan., and the higher the temperature in last dekad in this Jan. When the average meridional circulation in last Jul. to last Aug is stronger, the rainfall in this Apr. is more. The atmospheric general circulation boosts or restrains the occurrence and development of wheat Powdery mildew by affecting microclimate environment.