Investigation of the Reliability of the Sunspot Numbers Issued by Yunnan Observatory

The sunspot numbers have been observed at Yunnan Observatory by tracting the out-line sketchs of sunspots with hands since 1957. The comparison of sunspot numbers issued by Yunnan Observatory and those from the Solar Geophysical Data report has been made in this paper. It is shown that the sunspot numbers of Yunnan Observatory are high—linearly correlated with those from the Solar Geophysical Data report at the whole investigated inter-val from Jan.1964 to Dec.1996 during the solar cycles 20, 21 and 22. The relative deviation is generally less than 10 percent. The observational wolf curve of sunspot numbers of Yun-nan Observatory almost overlays the curve of those from the Solar Geophysical Data report in the solar cycle 21, is much closer to in the solar cycle 20, and has less difference in the so-lar cycle 22.