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Rainfall of the Yangtze River

The Yangtze River is the third longest river in the world. Its Valley stretches from the Tibetan Plateau to eastern China. Almost one-third of the population of China resides in this valley. Monthly rainfall in the catchment’s basin of the Yangtze River is normally heavy during March-June with peak totals exceeding 200 mm during May and June.

Seasonal rainfall was above average all over southern China during JJA 2002, with the largest surpluses of 300-500 mm observed in the Yangtze River Valley. Local seasonal totals ranged from 700-900 mm all over this region, exceeding 900 mm in the southwest. In the East these amounts were 150%-200% of normal, while they exceeded 200% of normal in parts of the West.

The whole area-averaged rainfall of this region, totals during these three months reached almost 850 mm (blue curve, Fig. 1d), double the climatological mean. The area-averaged totals exceeded 350 mm in June, while the totals reached 250 mm and crossed the 90th percentile in both July and August.

This extreme rainfall throughout July and August resulted mostly from two delayed convective episodes. The first occurred during the second half of July and the second occurred in mid-August, as indicated by daily precipitation time series’ at three recording stations in the Yangtze River Valley. During the July convective episode a daily extreme total of 225 mm (9 inches) was recorded at Yueyang on 19 July. Daily totals at this station remained above 12.5 mm in each of the subsequent five days, and exceeded 25 mm on three of these days. Both Changde and Lingling also recorded several days with totals exceeding 25 mm during the period.

During the second convective episode both Changde and Yueyang recorded rainfall amounts above 25 mm on six of nine days between 12-20 August. Lingling also recorded daily totals near 50 mm on three of these days.

Yueyang’s normal rain was 200 mm when compared to the entire period from 16 July to 31 August it was 700 mm (27.5 inches). In both Changde and Lingling normal rain was 175 mm and 190 mm, respectively but during this period it was recorded as 500 mm (20 inches).

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