Research Of The Cause Of Difference Between By AWS- And MAN- Temperature And Relative Humidity Observations Recorded

The Automated Surface Observing System is currently replacing conventional observations In China , From the meteorological and climatological viewpoint,it is necessary to compare the data from the old and new measuring systems in order to gain an understanding of their differences.These differences may become important when using time series for applications such as the computation of climatic abnormal , the development of homogeneous datasets for long periods of record for the investigation of climatic change,and the analysis of extreme weather events.So the 12th CCL ask clearly each country of WMO that it must be parallel observation for long time during the course of automatization of atmosphere observation. With the unified principle of climate data storage and management, it is necessary to do quality evaluation in order to ensure the data homogeneous.For the representation of the research result,By means of computing the annual average differences and the change of monthly average differences of 17 weather stations in different area of China in 2005.As for temperature,sorting analysis hourly data of these stations according to cloud amount,wind speed,day and night,and the differences in site characteristics,Solar radiation(IR cooling in night),instrument system and observing practice are considered the main factors.It is showed that the annual average difference of temperature is almost within±0.2℃,and it is almost no connection with location where the station lie.In spring,summer,autumn and winter,the temperature difference between the auto weather station and man-made Observation has all similar daily change character.Whether the maximal temperature,the minimal temperature or hourly temperature,their monthly and yearly statistic result has similar character,the temperature of auto weather stations is higher than it of man_made observation. In the above four factors,the instrument bias plays an part in these factors,it is about 0.1℃at most stations,and the bias about local effect and observing practice are also very little,but the bias of radiation is largest.According to each disadvantage of auto weather station and man-made observation systems,relative humidity is sorted to 9 species in terms of the diversity with temperature and relative humidity,then it is compared and analyzed.It is indicated that there is systemic bias in most stations,the magnitude of Man-made Observation is usually greater than auto weather station,about 3.5%.The phenomenon is more obvious in humid area.The bias is more great in humid area in the same temperature,and it is revealed that there is similar result when the high temperature in the same relative humidity.