Water vapor content in the atmosphere and its variation trend over North China

Based on the NCEP/NCAR global re-analysis grid data(2.5°×2.5° Lat/Lon) for 56 years (1948-2003), the water vapor contents in the atmosphere are calculated over North China.We analyze the geographic distribution of water vapor content in the whole atmospheric layer, annual variations of water vapor content along 37.5°N, annual variat ions of water vapor content along 115°E and the inter-annual variations of water vapor content from 1948-2003 over North China.The result shows that (1) the water vapor content in the atmosphere over Huabei areas mainly concentrates in the east and the south, but there is very little in the west and the north; (2) the water vapor content in the atmosphere over Huabei areas reaches the maximum in summer, and the minimum in winter; (3) the tendency of water vapor content in the atmosphere over Huabei areas is continually decreasing from the end of fifties to the middle of eight ies of the 20th contury.From the end of forties to the middle of sevent ies of the 20th contury, there exists higher water vapor content in the atmosphere; from the middle of seventies to the beginning of 21th century, the anomaly of water vapor content in the atmosphere is basically below zero, namely, the period of low value; and (4) there are obviously correlations between the inter-annual vacillation of water vapor content and the ENSO events.