Zhao H.,Shanxi Climate Center |
Gao G.,National Climate Center |
Yan X.,CAS Institute of Atmospheric Physics |
Yan X.,Beijing Normal University |
And 4 more authors.
Climate Research | Year: 2011
Droughts caused by a lack of precipitation are one of the major factors limiting agricultural crop production. It is thus important to assess the risk of such droughts in order to reduce their effect on agriculture. In the present study, the drought risk for crop production was assessed through an integrated approach that analyzed the relationship between crop yield and drought on the Henan Plain, China. We used the calibrated CERES-Wheat model to simulate 2 levels of wheat yield, the yield potential and the water-limited yield potential, at 66 weather stations. The yield gap between the yield potential and the water-limited yield potential was used as an indicator of the effects of a precipitation deficit on crop production under rain-fed conditions. A strong linear relationship between the yield gap and the amount of precipitation in the growing season was observed for each station during the period 1962-2009. A uniform criterion for drought severity thresholds for the entire Henan Plain was constructed based on the yield gap. For each station, the growing-season precipitation thresholds associated with different drought severities were then calculated based on the linear relationship between the yield gap and the amount of precipitation in the growing season. Drought frequencies derived from changes in the amount of precipitation during the growing season were also examined for all stations and spatially interpolated over the plain. The results showed diverse spatial patterns of frequency with respect to different drought types. Light droughts often occurred in the southern region, and moderate droughts occurred more frequently in the western and eastern regions. Severe drought displayed a generally decreasing trend from north to south. © Inter-Research 2011.
Guo J.,Chinese Academy of Meteorological Sciences |
Guo J.,University of Maryland University College |
Zhai P.,Chinese Academy of Meteorological Sciences |
Wu L.,Henan Climate Center |
And 7 more authors.
International Journal of Climatology | Year: 2014
Some new features concerning the diurnal variation of precipitation over the Tibetan Plateau (TP) are revealed from rainfall data acquired by a network of rain gauge stations and estimated by the Climate Precipitation Center Morphing (CMORPH) technique collected during the summer of 2010 and 2011. Maxima in precipitation amount and frequency are associated with the afternoon-to-evening precipitation regime at approximately 60% of the stations in the network. CMORPH data also capture this pattern, but miss the late morning peak that occurs at some stations. The timing of maximum occurrence agrees well with the diurnal cycle of synoptic conditions favouring the development of precipitation over this area. There is no distinct west-to-east propagation of the diurnal cycle, implying that the diurnal cycle is more driven by local effects than by large-scale circulation. It turns out that the diurnal cycle in precipitation frequency depends largely on topography and landscape. The geographical transition in precipitation peak time is distinct from hilly regions (daytime peak) towards lakes and valleys (evening-to-nocturnal peaks). Stations located in mountainous regions (valleys) tend to experience more precipitation in either late morning or early afternoon (late afternoon or evening). Overall, precipitation amount shows a similar topographic dependence, as does the precipitation frequency, suggesting that local-scale effects, such as the mountain valley circulation effect, has a great impact on the diurnal variation in precipitation when large-scale dynamical processes are weak. A possible mechanism for the non-uniform diurnal cycle of precipitation over the TP is proposed. The major conclusion is that plateau-scale synoptic systems, as well as local circulation systems caused by the complex topography, should be taken into account when determining the diurnal variation in precipitation over the TP. © 2013 Royal Meteorological Society.
Gu W.-L.,Henan Climate Center |
Zhu L.-L.,Henan Climate Center |
Xu H.-M.,National Climate Center |
Wang J.-J.,Henan Climate Center |
Zhu Y.-Y.,Henan Climate Center
Chinese Journal of Ecology | Year: 2010
In order to evaluate the effects of climate change on water resources, an evaluation model for the upper reaches of Shahe River (the central agricultural area of Henan Province) was set up, based on the Soil and Water Assessment Tool (SWAT) model. By using 1:4000000 digital river data, the error automatically produced by using 1:250000 DEM was removed. In the meantime, the hydrological and meteorological data in 1999-2002 and 2003-2006 were respectively applied to calibrate and verify the model, based on the sensitivity analysis of parameters. During the calibration period, the Ens = 0. 96 and r2 = 0. 95; and during the verification period, the Ens =0.81 and r 2 = 0. 87. Both of these indicated that the model could be successfully applied to simulate the monthly runoff. The simulated results from 1966 to 2007 showed that the surface runoff and groundwater had the same changing trend with precipitation. Evapotranspiration was the main output of the water resources in the area, and the surface runoff was about 2 times of the groundwater. The runoff showed a lag behind precipitation, and the precipitation lagged 3 months to become groundwater.
Wu L.,Chinese Academy of Meteorological Sciences |
Wu L.,Henan Climate Center |
Zhai P.,Chinese Academy of Meteorological Sciences
Acta Meteorologica Sinica | Year: 2012
Daily precipitation amounts and frequencies from the CMORPH (Climate Prediction Center Morphing Technique) and TRMM (Tropical Rainfall Measuring Mission) 3B42 precipitation products are validated against warm season in-situ precipitation observations from 2003 to 2008 over the Tibetan Plateau and the regions to its east. The results indicate that these two satellite datasets can better detect daily precipitation frequency than daily precipitation amount. The ability of CMORPH and TRMM 3B42 to accurately detect daily precipitation amount is dependent on the underlying terrain. Both datasets are more reliable over the relatively flat terrain of the northeastern Tibetan Plateau, the Sichuan basin, and the mid-lower reaches of the Yangtze River than over the complex terrain of the Tibetan Plateau. Both satellite products are able to detect the occurrence of daily rainfall events; however, their performance is worse in regions of complex topography, such as the Tibetan Plateau. Regional distributions of precipitation amount by precipitation intensity based on TRMM 3B42 are close to those based on rain gauge data. By contrast, similar distributions based on CMORPH differ substantially. CMORPH overestimates the amount of rain associated with the most intense precipitation events over the mid-lower reaches of the Yangtze River while underestimating the amount of rain associated with lighter precipitation events. CMORPH underestimates the amount of intense precipitation and overestimates the amount of lighter precipitation over the other analyzed regions. TRMM 3B42 underestimates the frequency of light precipitation over the Sichuan basin and the mid-lower reaches of the Yangtze River. CMORPH overestimates the frequencies of weak and intense precipitation over the mid-lower reaches of the Yangtze River, and underestimates the frequencies of moderate and heavy precipitation. CMORPH also overestimates the frequency of light precipitation and underestimates the frequency of intense precipitation over the other three regions. The TRMM 3B42 product provides better characterizations of the regional gamma distributions of daily precipitation amount than the CMORPH product, for which the cumulative distribution functions are biased toward lighter precipitation events. © 2012 The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg.
Ji X.-J.,Henan Climate Center |
Wang J.-J.,Henan Climate Center |
Gu W.-L.,Henan Climate Center |
Zhu Y.-Y.,Henan Climate Center |
Li F.-X.,Henan Climate Center
Advances in Climate Change Research | Year: 2012
The annual and seasonal trends in pan evaporation in the lower Yellow River Basin based on quality-controlled data from 10 meteorological stations in 1961-2010 are analyzed. The causes for the changes in annual and seasonal pan evaporation are also discussed. The results suggest that, despite the 1.15°C increasing in annual mean surface air temperature over the past 50 years (0.23°C per decade), the annual pan evaporation has steadily declined by an average rate of -7.65 mm per year. By comparison, this change is greater than those previously reported in China. Significant decreasing trends in annual pan evaporation have been observed at almost all stations. As a whole, seasonal pan evaporation decreased significantly, especially in summer, whereas seasonal temperature increased significantly, except in summer. Thus, the pan evaporation paradox exists in the lower Yellow River Basin. The trend analysis of other meteorological factors indicates significant decrease in sunshine duration and wind speed, but no significant variations in precipitation and relative humidity at annual and seasonal time scales. By examining the relationship between precipitation and pan evaporation, it did not show a concurrent decrease in pan evaporation and increase in precipitation. The partial correlation analysis discovered that the primary cause of decrease in annual and seasonal pan evaporation is the decrease in wind speed. A further examination using a stepwise regression shows that decrease in wind speed and sunshine duration, and increase in mean temperature are likely to be the main meteorological factors affecting the annual and seasonal pan evaporation in the lower Yellow River Basin over the past 50 years.