Search

Hydroclimate variations over eastern China are affected by the Asian monsoon, exhibiting great variability and frequent extreme events occurrence. However, the driving mechanisms of their spatial and temporal variabilities are not fully understood due to the short period of available climate observation data. Here we used interpolated dry/wet grades dataset derived from Chinese historical documents and method of regional division to reconstruct a new annual hydroclimatic variation dataset dating back 1000 years, including nine regions of eastern China. This dataset reveals the spatial coverage and trend of long‐lasting extreme drought and flood events, and discloses the spatial patterns and similarities of interannual (2–7‐year) and interdecadal (15–35‐year) hydroclimate variations under the different temperature backgrounds of the Medieval Climate Anomaly (MCA), Little Ice Age (LIA) and Current Warm Period. Although no obvious drying or wetting trends were detected in the past 1000 years, the frequencies of extreme flood and drought events during the two warm periods of 960–1300 and 1901–2000 were higher than those during the cold period of 1301–1900. There are 17 long‐lasting and even severe than 1637–1641 large spatial scale extreme drought events during the past 1000 years. The observed spatial dipole pattern of flooding in the south and drought in the north, or the opposite pattern, was rare during the historical period. However, it was the second leading mode explaining the low variances in the principal component analysis for 2–7‐year hydroclimatic variations, which were not related to temperature change. Moreover, the stability of the teleconnection between the hydroclimate over eastern China and the climatic modes of Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation was further discussed. [ABSTRACT FROM AUTHOR]

The major droughts and floods in the Hanjiang River Basin, central China, have a significant impact on flood prevention and control in the middle reaches of the Yangtze River and water resources management in the areas of the South–North Water Diversion Middle Line Project. However, there is a lack of understanding of the multi-decadal to centennial-scale patterns of extreme droughts and floods in the area. Applying the yearly drought and flood records from historical documents and precipitation data in the period of instrumental measurements, this study constructs a time series of extreme droughts and floods in the Hanjiang River Basin from 1426–2017 and analyzes the temporal and spatial characteristics of the extreme drought and flood event variations. The results show that there were a total of 45 extreme droughts and 52 extreme floods in the basin over the past 592 years. Extreme droughts and floods were highly variable on a multi-decadal to centennial scale, and the frequencies were higher in the first and last 100 years or so of the study period and lower in between. Spatially, the frequencies of extreme droughts and floods were generally higher in the middle and lower reaches than in the upper reaches. It was also found that there is a good correlation of drought and flood frequencies between the upper Hanjiang River Basin and North China. These results are informative for the study of mechanisms and predictability of multi-decadal to centennial-scale variability of extreme hydroclimatic events in the river basin. [ABSTRACT FROM AUTHOR]

In China, historical documents record a large quantity of information related to climate change and grain harvest. This information can help to explore the impacts of extreme drought or flood on crop production, which can provide implications for the adaptation of agriculture to higher-probability extreme climate in the context of global warming. In this paper, reported extreme drought/flood chronologies and reconstructed grain harvest series derived from historical documents were adopted in order to investigate the association between the reported frequency of extreme drought/flood in eastern China and reconstructed poor harvests during 801–1910. The results show that extreme droughts were reported more often in 801–870, 1031–1230, 1481–1530, and 1581–1650 over the whole of eastern China. On a regional scale, extreme droughts were reported more often in 1031–1100, 1441–1490, 1601–1650, and 1831–1880 in the North China Plain, 801–870, 1031–1120, 1161–1220, and 1471–1530 in Jianghuai, and 991–1040, 1091–1150, 1171–1230, 1411–1470, and 1481–1530 in Jiangnan. The grain harvest was reconstructed to be generally poor in 801–940, 1251–1650, and 1841–1910, but the reconstructed harvests were bumper in 951–1250 and 1651–1840, approximately. During the entire period from 801 to 1910, the frequency of reporting of extreme droughts in any subregion of eastern China was significantly associated over the long term with lower reconstructed harvests. The association between reported frequency of extreme floods and reconstructed low harvests appeared to be much weaker, while reconstructed harvest was much worse when extreme drought and extreme flood in different subregions were reported in the same year. The association between reconstructed poor harvests and reported frequency of regional extreme droughts was weak during the warm epoch of 920–1300 but strong during the cold epoch of 1310–1880, which could imply that a warm climate could weaken the impact of extreme drought on poor harvests; yet other historical factors may also contribute to these different patterns extracted from the two datasets. [ABSTRACT FROM AUTHOR]

Reconstructed hydroclimatic spatial patterns from historical documents, the chronology of El Niño events since 1525, Meiyu (a unique rainy season dominated by the East Asian summer monsoon in eastern China) series since 1736, and a 1000-year control simulation using the Community Earth System Model were used to analyze the occurrence of anomalous summer precipitation patterns over eastern China with El Niño events. The results show that the frequency of the south-flood north-drought during 1525–2005 was significantly higher during El Niño episodes. Specifically, the occurrences of the triple pattern with floods in the Yangtze River Valley but droughts in its north and south (FYRDNS) as well as the dipole pattern with floods in the south but droughts in the north (FSDN) divided by the Yangtze River both increased in El Niño developing years, while the occurrence of FSDN increased in El Niño decaying years. Among 44 severe and extreme Meiyu events over the middle and lower reaches of the Yangtze River in 1736–2016, 75% of events occurred during El Niño episodes. Especially, 80% of extreme Meiyu events occurred in El Niño decaying years. The 1000-year control simulation captured well the reconstructed triple pattern of FYRDNS in developing years and the dipole pattern of FSDN in decaying years, with more noticeable precipitation anomalies for developing years of very strong and extremely strong El Niño events. These results implicated that the El Niño is likely an early signal for the occurrence of the south-flood north-drought over eastern China. [ABSTRACT FROM AUTHOR]