Using geographic information system (GIS) techniques and the newest seasonal and annual average precipitation data of 679 meteorological stations from 1971 to 2000, the multiple regressions equations of the precipitat...Using geographic information system (GIS) techniques and the newest seasonal and annual average precipitation data of 679 meteorological stations from 1971 to 2000, the multiple regressions equations of the precipitation and topographical variables are established to extract the effect of topography on the annual and seasonal precipitation in the upper-middle reaches of the Yangtze River. Then, this paper uses a successive interpolation approach (SIA), which combines GIS techniques with the multiple regressions, to improve the accuracy of the spatial interpolation of annual and seasonal rainfall. The results are very satisfactory in the case of seasonal rainfall, with the relative error of 6.86%, the absolute error of 13.07 mm, the average coefficient of variation of 0.070, and the correlation coefficient of 0.9675; in the case of annual precipitation, with the relative error of 7.34%, the absolute error of 72.1 mm, the average coefficient of variation of 0.092, and the correlation coefficient of 0.9605. The analyses of annual mean precipitation show that the SIA calculation of 3-5 steps considerably improves the interpolation accuracy, decreasing the absolute error from 211.0 mm to 62.4 mm, the relative error from 20.74% to 5.97%, the coefficient of variation from 0.2312 to 0.0761, and increasing the correlation coefficient from 0.5467 to 0.9619. The SIA iterative results after 50 steps identically converge to the observed precipitation.展开更多
Precise vertical total electron contents (VTEC) and its time variation have been obtained by using GPS dual-frequency observations collected by the continuously operating GPS tracking stations distributed over China. ...Precise vertical total electron contents (VTEC) and its time variation have been obtained by using GPS dual-frequency observations collected by the continuously operating GPS tracking stations distributed over China. Us-ing VTEC data, the wave-motion appearing in the iono-sphere on November 3, 2003 is monitored and analyzed when a small solar flare happened. Detailed discussion with the VTEC and its change rate series, which are derived from the observations (data) from PRN23 satellite, indicates that the wave-motion mainly contains two dominant frequencies and propagates almost along the meridian line toward south. Additionally, the fluctuation of the mean VTEC has been calculated in a regional Single Layer Model (SLM) iono-spheric shell in the range of N28.0°―34.0° and E118.0°―123.0°. The spectral analysis and the multi-resolution analy-sis of mean VTEC time series show that the periods of these two components of the wave-motion at middle altitude are around 60 and 25 min separately, and the amplitudes can be up to 1.0―2.0 TECU and 0.4―0.7 TECU respectively. Mean- while, the relative motion between the wave-motion and the Ionosphere Pierce Points (IPPs), which are defined as the cross points between the line-of-sight of the GPS signals and the SLM thin shell, reveals that the traveling speeds of the two components are about 120―150 m/s and 30―40 m/s respectively.展开更多
基金The National 973 Project of China, No.2001CB309404 O versea O utstanding Youth Cooperation Project, N o. 40128001/D 05N ationalN aturalScience Foundation ofChina,N o.49375248 Zhejiang Province Science Research (C33)Project,N o.2004C33082
文摘Using geographic information system (GIS) techniques and the newest seasonal and annual average precipitation data of 679 meteorological stations from 1971 to 2000, the multiple regressions equations of the precipitation and topographical variables are established to extract the effect of topography on the annual and seasonal precipitation in the upper-middle reaches of the Yangtze River. Then, this paper uses a successive interpolation approach (SIA), which combines GIS techniques with the multiple regressions, to improve the accuracy of the spatial interpolation of annual and seasonal rainfall. The results are very satisfactory in the case of seasonal rainfall, with the relative error of 6.86%, the absolute error of 13.07 mm, the average coefficient of variation of 0.070, and the correlation coefficient of 0.9675; in the case of annual precipitation, with the relative error of 7.34%, the absolute error of 72.1 mm, the average coefficient of variation of 0.092, and the correlation coefficient of 0.9605. The analyses of annual mean precipitation show that the SIA calculation of 3-5 steps considerably improves the interpolation accuracy, decreasing the absolute error from 211.0 mm to 62.4 mm, the relative error from 20.74% to 5.97%, the coefficient of variation from 0.2312 to 0.0761, and increasing the correlation coefficient from 0.5467 to 0.9619. The SIA iterative results after 50 steps identically converge to the observed precipitation.
基金supported by the 100-Talent Fund of the Chinese Academy of Sciences in Astro-geodynamic Center of Shanghai Astronomical Observatorythe National Natural Science Foundation of China(Grant No.40174009)+2 种基金the Knowledge Creative Project of the Chinese Academy of Sciences(Grant No.KJCX2-SW-T1)the Shanghai Scientific Technology Development Fund(Grant No.JC14012)the Guangxi Fund for Youth(Grant No.9912008).
文摘Precise vertical total electron contents (VTEC) and its time variation have been obtained by using GPS dual-frequency observations collected by the continuously operating GPS tracking stations distributed over China. Us-ing VTEC data, the wave-motion appearing in the iono-sphere on November 3, 2003 is monitored and analyzed when a small solar flare happened. Detailed discussion with the VTEC and its change rate series, which are derived from the observations (data) from PRN23 satellite, indicates that the wave-motion mainly contains two dominant frequencies and propagates almost along the meridian line toward south. Additionally, the fluctuation of the mean VTEC has been calculated in a regional Single Layer Model (SLM) iono-spheric shell in the range of N28.0°―34.0° and E118.0°―123.0°. The spectral analysis and the multi-resolution analy-sis of mean VTEC time series show that the periods of these two components of the wave-motion at middle altitude are around 60 and 25 min separately, and the amplitudes can be up to 1.0―2.0 TECU and 0.4―0.7 TECU respectively. Mean- while, the relative motion between the wave-motion and the Ionosphere Pierce Points (IPPs), which are defined as the cross points between the line-of-sight of the GPS signals and the SLM thin shell, reveals that the traveling speeds of the two components are about 120―150 m/s and 30―40 m/s respectively.
