According to the monitoring record, human nuclear activities, especially intensive nuclear tests during the 1960s in the world, caused atmospheric tritium concentration increasing significantly, which provided convenient condition for global water cycle research, especially for tracer dating research of groundwater. However, due to the layout of monitoring sites and other reasons, most parts of the world are lack of monitoring data of tritium concentration in precipitation. The tritium time series in precipitation in Beijing during 1953~2002 was reconstructed in this paper using combined methods, including improved Guanbingjun Method, Trigonometric Interpolation Method and Correlation Method, aiming to find the best method for Beijing. Considering the real situation of Beijing, some improvement has been made about the Guanbingjun Method, (assigning the weights of adjacent latitudes for tritium concentration in precipitation reconstructed as 9:1, 5:5, 1:9 to get the final value). Compared with Trigonometric Interpolation Method, the result calculated by improved Guanbingjun Method has the lowest relative error, which is 5.07%, because it takes the different effects which the adjacent bonds of latitude contribute into account.
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