ADVANCES IN THE STUDY OF RAINFALL VARIATIONS IN THE HISTORICAL PERIODS OF CHINA

Our work succeeded in retrieving the events, reconstructing the sequences and extremes of historical precipitation, as shown below.

1) In recent years an attempt has been made to reduce grid-based anomaly fields from historical descriptions. With the aid of computers and the"A Compendium of Chinese Meteorological Records of the Last 3000 Years" as basic data, different values were assigned to related grid points according to the descriptions and through interpolation a rainfall anomaly field was computer-retrieved in a way that denotes grid anomalies by -1, 0 and +1 at a 1-year and a 1x1 lat./long. resolution. We have thus reduced tentatively the anomaly fields in 1501-1900 annual precipitation for the eastern part of China, attaining a total of 400 grid-based maps and intend to employ in addressing climate change and verifying output from numerical models.

2) Restudy of rainfall descriptions from the "Daily Weather Records" covered 1724-1904 made in Qing Dynasty for Beijing . The present work recalculated the retrievals and investigated its techniques, whereupon we propose an 8-factor stepwise regression scheme to "translate" the descriptions into seven categories of daily rainfall intensity, from which monthly precipitation totals are obtained in conformity with contemporary rainfall data. Thereby we get rainfall series on a seasonal and an annual basis in 1724-2000.

3) Retrieval of extremely dry and wet events in historical periods e.g., those of large-scale excessive precipitation on a continuous basis in 1552-1553, 1755-1757 and 1870-1872, and of extensive persistent droughts, in 1484-1485,1527-1529,1784-1787 and 1876-1878. It is worth noting that many of the historical extremes exceed in severity the counterparts to much greater extent that have merged in the past 50 years.