Using a homogenized daily maximum temperature(T_(max))dataset across China,this study characterized the spatiotemporal variation of the onset date of extreme hot days in a year(i.e.,FirstEHD)during 1960-2018.Inhomogen...Using a homogenized daily maximum temperature(T_(max))dataset across China,this study characterized the spatiotemporal variation of the onset date of extreme hot days in a year(i.e.,FirstEHD)during 1960-2018.Inhomogeneous trends of FirstEHD over China during 1960-2018 can be found,with the advanced trend of FirstEHD over most parts in China,while a number of stations in North-Central China(NC)show the delayed trend of FirstEHD.Moreover,there exist interdecadal changes of FirstEHD trend,with a remarkable difference in the trend magnitude before and after the 1990s over South China(SC),and the sign of trend can even reverse from negative to positive after the 1990s in Xinjiang(XJ)and Yangtze River Basin(YR),and from positive to negative in NC.The overall trends of FirstEHD over NC,YR,and XJ during 1960-2018 are dominated by the trends before the 1990s,while they are dominated by the sharp advance after the 1990s over SC.It is further found that the trend of FirstEHD can generally be explained by the long-term trend in T_(max) over most parts of China,but the contribution from T_(max) variabilities is also non-negligible and can even account for more than 75% of the overall trend over NC.The possible factors responsible for the decadal changes in FirstEHD trends are also discussed.展开更多
The formation of tree-rings is closely related to climate variation. This paper establishes the tree-ring chronology of Pinus massoniana for a period of 36 years and examines the relationship between the tree-ring chr...The formation of tree-rings is closely related to climate variation. This paper establishes the tree-ring chronology of Pinus massoniana for a period of 36 years and examines the relationship between the tree-ring chronology and climatic conditions based on tree-ring width samples from three sites on the northeast slopes of Yangming Mountain. This data is used to study the relationship between the tree-ring width of a young tree and climatic conditions in a moist hilly region of southern China and to understand the general pattern of climate variation and its effects on tree growth in the past in this region. The results indicate that changes in tree-ring widths in these sites are closely related to local climatic conditions. There is a significant positive correlation between the radial growth of Pinus massoniana and the mean temperature of the current year from January to May（coefficient of correlation, R, is 0.596, P〈0.01） and the mean temperature of the previous year from June to July（R is 0.639, P〈0.01）. The radial growth of Pinus massoniana is negatively correlated with the total precipitation of the previous year from January to March and November to December（R is-0.46, P〈0.05） and negatively correlated with the total precipitation of the previous year from June to July（R is-0.582, P〈0.05）. The effect of precipitation on the radial growth of Pinus massoniana is known as the ＂hysteresis effect＂.展开更多
基金funded by the National Key Research and De-velopment Program of China[Grant number 2017YFA0604304]the National Natural Science Foundation of China[Grant number 41661144032].
文摘Using a homogenized daily maximum temperature(T_(max))dataset across China,this study characterized the spatiotemporal variation of the onset date of extreme hot days in a year(i.e.,FirstEHD)during 1960-2018.Inhomogeneous trends of FirstEHD over China during 1960-2018 can be found,with the advanced trend of FirstEHD over most parts in China,while a number of stations in North-Central China(NC)show the delayed trend of FirstEHD.Moreover,there exist interdecadal changes of FirstEHD trend,with a remarkable difference in the trend magnitude before and after the 1990s over South China(SC),and the sign of trend can even reverse from negative to positive after the 1990s in Xinjiang(XJ)and Yangtze River Basin(YR),and from positive to negative in NC.The overall trends of FirstEHD over NC,YR,and XJ during 1960-2018 are dominated by the trends before the 1990s,while they are dominated by the sharp advance after the 1990s over SC.It is further found that the trend of FirstEHD can generally be explained by the long-term trend in T_(max) over most parts of China,but the contribution from T_(max) variabilities is also non-negligible and can even account for more than 75% of the overall trend over NC.The possible factors responsible for the decadal changes in FirstEHD trends are also discussed.
基金National Natural Science Foundation of China(41571509)
文摘The formation of tree-rings is closely related to climate variation. This paper establishes the tree-ring chronology of Pinus massoniana for a period of 36 years and examines the relationship between the tree-ring chronology and climatic conditions based on tree-ring width samples from three sites on the northeast slopes of Yangming Mountain. This data is used to study the relationship between the tree-ring width of a young tree and climatic conditions in a moist hilly region of southern China and to understand the general pattern of climate variation and its effects on tree growth in the past in this region. The results indicate that changes in tree-ring widths in these sites are closely related to local climatic conditions. There is a significant positive correlation between the radial growth of Pinus massoniana and the mean temperature of the current year from January to May（coefficient of correlation, R, is 0.596, P〈0.01） and the mean temperature of the previous year from June to July（R is 0.639, P〈0.01）. The radial growth of Pinus massoniana is negatively correlated with the total precipitation of the previous year from January to March and November to December（R is-0.46, P〈0.05） and negatively correlated with the total precipitation of the previous year from June to July（R is-0.582, P〈0.05）. The effect of precipitation on the radial growth of Pinus massoniana is known as the ＂hysteresis effect＂.
