| With global warming, global hydrological cycle accelerating and moisturecontent in the atmosphere inceasing subsequently, the climatic change triggered bythe obvious change of spatial-temporal distribution pattern in precipitation makemore significant effects on human environment, such as increasing droughts, floodsand so on, having threatened the basic conditions on which human rely. Owing tounique location and the regional advantages in traffic, energy sources and scientificeducational sources, Shaanxi Province is the transport transshipment hub connectingeastern China, northwestern China and southwestern China and is also chineseimportant food production area, energy chemical industry base, modern chinesemedicine base and green fruit base, possessing the important strategic positionconsolidating national defense and developing western economy. An increase in thefrequency of drought-flood disasters appearing in Shaanxi Province has been foundin recent years, which has caused many adverse influences on the residents’ life andproperty security, agricultural production, economic development, ecologicalenvironment and so on in the province. Precipitation change is one of the importantcauses leading to extreme disaster weathers such as droughts, floods and so on.Consequently, it has important meanings for the sustainable development ineconomy and society in Shaanxi Province and in China to study the temporal andspatial pattern in precipitation over Shaanxi Province. Based on ground dailyprecipitation data at82grids whose spatial resolutions are0.5°×0.5°and19meteorological stations over Shaanxi Province during1960～2011, originating fromthe China Meteorological Administration, together with4extreme precipitationindices generated by the joint CCl/CLIVAR/JCOMM ETCCDI and the methods ofclimate tendency rate, climate tendency coefficient, variation coefficient,Mann-Kendall mutations inspection, Morlet wavelet analysis, inverse distanceweighted interpolation and correlation analysis and so on, the spatial-temporalvariation characteristics in precipitation over Shaanxi Province during1960～2011were analyzed from two aspects of mean precipitation and extreme precipitation.The results are as follows:(1) The annual precipitation in Shaanxi Province, northern Shaanxi, central Shaanxi and southern Shaanxi exhibit all decreasing trends during1960～2011; Theannual precipitation in northern Shaanxi represents a continuous negative tendencyfrom the1960s to the1990s and shows a positive trend subsequently, whereas theannual precipitation in Shaanxi Province, central Shaanxi and southern Shaanxirepresent consistently decreasing trends from the1960s to the1970s, then increasein the1980s, decrease again in the1990s and display increase trends again from the1990s to the period of2000～2011; The significant abrupt step changes for theannual precipitation in Shaanxi Province, northern Shaanxi, central Shaanxi andsouthern Shaanxi are found in1985,1978,1984and1988, respectively. For theannual precipitation in Shaanxi Province and southern Shaanxi, there all are twoscales of change cycles which are5-year cycle and13-year cycle, while only onevariation period for the annual precipitation in northern Shaanxi and central Shaanxiis detected and it is5-year cycle and12-year cycle, respectively; The mean value ofannual precipitation in Shaanxi Province shows overall an increasing trend from thenorth part to the south part in study area with obvious spatial distribution differences;Opposite to the spatial distribution of annual precipitation, a decreasing trend fromthe north part to the south part in study area is found for the variation coefficient ofannual precipitation; Annual precipitation present negative trends in northernShaanxi and central Shaanxi, while grids where annual precipitation show positivetrends exist all in southern Shaanxi.(2) During the period of1960～2011, the maximum1-day precipitation, verywet day precipitation and extremely wet day precipitation in Shaanxi Province showincreasing trends, while there is a statistically non-significant decrease tendency formaximum5-day precipitation; The maximum1-day precipitation, very wet dayprecipitation and extremely wet day precipitation exhibit continuous positive trendsfrom the1960s to the1980s, then decrease rapidly in the1990s and representpositive trends again from the1990s to the period of2000～2011, whereasmaximum5-day precipitation displays a decreasing trend from the1960s to the1970s, increases in the1980s, decreases again in the1990s and and shows anincrease trend again from the1990s to the period of2000～2011; The mean valuesof the extreme precipitation in Shaanxi Province have obvious regional differences and present low values in the northwest of northern Shaanxi, increase gradually fromthe North to the South and reach the highest values in the southwest of southernShaanxi; Positive trends are found in the most part of study area for maximum1-dayprecipitation, very wet day precipitation and extremely wet day precipitation, whilemaximum5-day precipitation shows generally negative trends in research area;There are positive correlations between the extreme precipitation and elevation,namely, there are trends towards increases for these extreme precipitation withelevation rising.(3) There are the same variation trends between the gridded series and observedseries of precipitation in Shaanxi Province during recent52years with differenttrend magnitudes; During study period, gridded series are generally higher thanobserved series for mean precipipitation, while lower for extreme precipitation;Except for very wet day precipitation, the gridded series and observed series for theother precipitation display the same interdecadal change trends; The spatialdistributions in mean values for the gridded series and observed series ofprecipitation show all that are very identical in northern Shaanxi and central Shaanxi,but different in southern Shaanxi; The spatial distributions in variation trends for thegridded series and observed series of annual mean precipipitation and very wet dayprecipitation are generally identical in study area, while the degree of coherence forthe other precipitation is comparatively bad in study area; The correlationcoefficients between gridded and observed precipitation series in Shaanxi Provincefrom1960to2011all are above0.75and pass the statistically significant test at the0.01level; The spatial distributions of the correlation coefficients between griddedand observed precipitation series in Shaanxi Province exist obvious regionaldifferences with generally high values in research area; On the whole, the variationcharacteristics in precipitation based on gridded data and observed data over ShaanxiProvince during recent52years are very consistent although there are somedifferences between them, indicating the quality of selected gridded data can satisfyour use requirements within the scope of Shaanxi Province. |
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