بررسي تغييرات سري هاي رطوبت در ايستگاههاي سينوپتيك كشور

Increase of greenhouse gases not only causes global warming but also leads to some changes in climatic elements like humidity. Increases of both temperature and humidity have occurred in many places throughout the world . The higher atmospheric humidity, the more accessible water vapor for precipitation producing systems like thunderstorms or snowstorms. Atmospheric humidity changes can be assessed through study of time series of each humidity measures of relative humidity, actual water vapor pressure and dew point temperature or all these three. Since there are positive trend for temperature in most synoptic stations of the country especially for minimum temperature and also due to a mutual relation between temperature and humidity, we found it appropriate to study variables other than relative humidity. In this study, humidity data of 29 Iranian old synoptic stations for period 1951-1997 are Considered. We also used some recommended WMO4 tests like homogeneity, jump and trend ones. According to initial obtained results, we analyzed outputs only for 11 out of 29 stations that have more reliable data. We got interesting results upon using the above tests. We found negative trend for annual average of relative humidity and positive trend for annual average of maximum temperature in Isfahan. This can be due to afternoon decrease of absolute humidity in cities. Positive trends for both variables were found in Rasht.