Daily mean difference evaluation of manual observation

This paper focuses on the annual cycle, difference frequency and spatial characteristic of 24 and 4 times manual observation for temperature and those of 24 and 8 times, too. It shows 4times manual observation mean temperature is lower than 24times value about 0.11 °C. Whereas 8 times manual observation mean temperature is very close with 24 times value, and the difference frequency reaches 88.9% in the range of observation error. The spatial distribution of difference between 24 and 4 times manual temperature observation has meridional feature. This phenomenon is due to the dissimilarity of Beijing time and local time. Therefore, the stations in difference time zone but closing latitude are chose. The hour to hour daily cycle of mean temperature of those stations are analyzed. By adopting the dynamic mean of 4 times temperature observation, the difference between 24 and 4 times manual temperature observation is closer to the average value of all stations even more. The interpolation of 02 clock note is defined in “Surface meteorology observation criterion”. The difference between interpolation of 02 clock and real value of 02 clock is 0.68 °C in China.