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Li Q.,National Meteorological Information Center | Peng J.,Hunan Provincial Climate Center | Shen Y.,National Meteorological Information Center
Acta Geographica Sinica | Year: 2012

Based on the collection and processing of the China's national-wide monthly station observational precipitation data during 1900-2009, the data series for each station has been tested for their homogeneity with Standard Normalized Homogeneity Test (SNHT) method and the inhomogeneous part of the series are adjusted. Then the 1971-2000 climatology normals and precipitation anomalies during 1900-2009 have been transformed into the grid boxes at resolutions of 5°×5° and 2°×2°, respectively, and two gridded form datasets are constructed by combining the normals and anomalies. After that, the missing values for the 5°×5° grid dataset are interpolated by Empirical Orthogonal Function (EOF) techniques. With the datasets at different resolutions, the precipitation change series during 1900-2009 over Chinese Mainland were built, and the annual and seasonal precipitation changing trends for recent 110 years were analyzed. The result indicated that the annual precipitation showed a slightly dryer trend during the 110 years, but with no statistical confidence. To be pointed out, the interpolation of the missing values makes the precipitation amounts in the early 1900s decrease, so the trend for the 110 years increased. Source


Wu X.-Y.,Chinese Academy of Meteorological Sciences | Wu X.-Y.,Nanjing University of Information Science and Technology | Wu X.-Y.,Hunan Provincial Climate Center | Ding Y.-H.,National Climate Center
Journal of Tropical Meteorology | Year: 2013

Based on the daily regional mean rainfall, the Z-index method is used to identify persistent flood and drought events lasting for at least 10 days over a region where Dongting Lake and Poyang Lake sit (referred to as the "two-lake region" hereafter). The National Centers for Environmental Prediction (NCEP) reanalysis data are then utilized to perform a preliminary diagnostic analysis on these events. The results indicate that the composite standardized geopotential height at 500 hPa presents two different meridional wave trains from north to south over the East Asian-Pacific region, i.e., a "-+-" pattern for the droughts and a "+-+" pattern for the floods, respectively. The developing, maintaining and decaying phases in the drought and flood events are closely related to the intensity and location of a subtropical high and an extra-tropical blocking high. It is shown that the East Asian summer monsoon is strong (weak) with the occurrence of persistent drought (flood) events. Droughts (floods) are accompanied by a weak (strong) tropical convergent system and a strong (weak) subtropical convergent system. Furthermore, the persistent drought (flood) events are associated with a divergence (convergence) of vertically integrated water vapor flux. In the vertical profile of water vapor flux, divergence (convergence) in the mid- and lower-levels and convergence (divergence) in the higher levels are evident in the droughts (floods). Both the divergence in the droughts and the convergence in floods are strongest at 850 hPa. Source


Li Q.,National Meteorological Information Center | Li Q.,Hunan Provincial Climate Center | Peng J.,Hunan Provincial Climate Center | Shen Y.,National Meteorological Information Center
Journal of Geographical Sciences | Year: 2012

Based on the collection and processing of the China national-wide monthly station observational precipitation data in 1900-2009, the data series for each station has been tested for their homogeneity with the Standard Normalized Homogeneity Test (SNHT) method and the inhomogeneous parts of the series are adjusted or corrected. Based on the data, the precipitation anomalies during 1900-2009 and the climatology normals during 1971-2000 have been transformed into the grid boxes at 5°×5° and 2°×2° resolutions respectively. And two grid form datasets are constructed by combining the normal and anomalies. After that, the missing values for the 5°×5° grid dataset are interpolated by Empirical Orthogonal Function (EOF) techniques. With the datasets of different resolutions, the precipitation change series during 1900-2009 over Mainland China are built, and the annual and seasonal precipitation trends for the recent 110 years are analyzed. The result indicates that the annual precipitation shows a slight dryer trend during the past 110 years, notwithstanding lack of statistical confidence. It is worth noting that after the interpolation of the missing values, the annual precipitation amounts in the early 1900s become less, which increases the changing trend of the annual precipitation in China for the whole 110 years slightly (from -7.48 mm/100a to -6.48 mm/100a). © 2012 Science China Press and Springer-Verlag Berlin Heidelberg. Source

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