Multicollinearity and correlation among local regression coefficients in geographically weighted regression   总被引：5，自引：3，他引：5  

David Wheeler  Michael Tiefelsdorf 《Journal of Geographical Systems》2005,7(2):161-187

Present methodological research on geographically weighted regression (GWR) focuses primarily on extensions of the basic GWR model, while ignoring well-established diagnostics tests commonly used in standard global regression analysis. This paper investigates multicollinearity issues surrounding the local GWR coefficients at a single location and the overall correlation between GWR coefficients associated with two different exogenous variables. Results indicate that the local regression coefficients are potentially collinear even if the underlying exogenous variables in the data generating process are uncorrelated. Based on these findings, applied GWR research should practice caution in substantively interpreting the spatial patterns of local GWR coefficients. An empirical disease-mapping example is used to motivate the GWR multicollinearity problem. Controlled experiments are performed to systematically explore coefficient dependency issues in GWR. These experiments specify global models that use eigenvectors from a spatial link matrix as exogenous variables.This study was supported by grant number 1 R1 CA95982-01, Geographic-Based Research in Cancer Control and Epidermiology, from the National Cancer Institute. The author thank the anonymous reviewers and the editor for their helpful comments.  相似文献   

影响华东地区热带气旋年频数与热带对流场的关系          下载免费PDF全文

周霞琼  葛旭阳等 《气象科学》2002,22(1):9-15

利用由美国NOAA系列卫星观测的OLR资料研究了影响华东地区热带气旋年频数（记为ATC）与热带对流场的关系，结果表明两者存在密切的联系：（1）当华东地区热带气旋年频数ATC为异常偏多（少）时，ITCZ位置累积距平为正（负）值，即ITCZ位置异常偏北（南）；（2）利用OLR设计了Walker综合指数WI，该指数的强弱可以反映ATC的异常情况，即当ATC为异常偏多（少）时，walker环流圈异常强（弱）；（3）OLR距平累积量场能较好的表征ATC异常年份所对应的低纬度及中高纬地区大气环流的配置，其可以作为预测影响华东地区热带气旋年频数的强信号。  相似文献   

Structure Functions In A Wall-Turbulent Shear Flow     

U. Giostra  D. Cava  S. Schipa 《Boundary-Layer Meteorology》2002,103(3):337-359

Wavelet and quadrant analyses were applied to turbulent velocity data in order to investigate the transition from the anisotropy of energy-containing eddies to the isotropy of the inertial subrange scales. The quadrant analysis of the wavelet coefficients of longitudinal and vertical velocity components allows the evaluation of the velocity structure functions and the momentum cospectrum as a function of the separation distance and of the quadrants. In an isotropic condition the contribution both of ejections and sweeps (even quadrants), and both of reflections and deflections (odd quadrants), has to be equal. The analysis has shown that in neutrally stratified conditions the transition to isotropy occurs in a frequency range (0.2 < r/z < 3) usually referred to as internal to the inertial subrange (r is separation distance, z is height). In the transition region, as in the isotropic region, the velocity structure functions still agree with the 1941 and 1962 Kolmogorov theories; but on the other hand the structure functions of the even and odd quadrants are fitted by power laws of different slopes in the transition region. The proposed analysis allows the investigation within the transition region of the different dynamical structure in the energy transfer from the energy-containing scales to the isotropic scales.  相似文献   

Cretaceous length of day perturbation by mantle avalanche     

Philippe Machetel  Emilie Thomassot 《Earth and Planetary Science Letters》2002,202(2):379-386

These last 10 years, numerical models of mantle convection have emphasized the role of the 670 km endothermic phase change in generating avalanches that trigger catastrophic mass transfers between upper and lower mantle. On the other hand, scientists have emphasized the concomitance of large-scale worldwide geophysical and tectonic events, which could find their deep thermal roots in the huge mass transfers induced by the avalanches. In particular, the paleontological records show two periods of length of day (l.o.d.) shortening between 420 and 360, and 200 and 80 Myr BP. This last event is synchronous with a strong true polar wander and a global warming of the upper mantle. In order to study the potential effects of the avalanche on the main component of the Earth’s rotation, the Liouville equation has been solved and the l.o.d. evolution has been calculated from the perturbations of the inertia tensor. The results show that the inertia tensor of the Earth’s is mainly sensitive to the global transfers through the 670 km discontinuity. The l.o.d. perturbations will be synchronous with the global thermal effects of the avalanche. These theoretical results allow proposing a self-consistent physical mechanism to explain periods of the Earth’s rotation acceleration. Within this context, the l.o.d. shortening during the Cenozoic and Cretaceous brings one more clue to the possible participation of a mantle avalanche in generating the concomitant large scale events which have occurred during this very particular period of the Earth’s history.  相似文献   

MODIFIED MASS FLUX CUMULUS CONVECTIVE PARAMETERIZATION SCHEME AND ITS SIMULATION EXPERIMENT—PART Ⅰ:MASS FLUX SCHEME AND ITS SIMULATION OF THE 1991 FLOOD EVENT^*          下载免费PDF全文

LIU Yiming  DING Yihui 《Acta Meteorologica Sinica》2002,16(1):37-49

Based on the existing cumulus convective parameterization schemes,a mass flux scheme (MFS) for cumulus convective parameterization has been successfully developed by reference to the work of Chen et al. (1996).The MFS is a comprehensive scheme.In MFS,not only the importance of the large-scale moisture convergence is taken into account,but also it includes the cumulus updrafts and downdrafts,cumulus-induced subsidence in the environmental air.entrainment,detrainment and evaporation.The interaction between the cumulus and the environment is described by using a one-dimensional bulk model.At the same time the scheme includes the penetrative and shallow convections.The MFS has been successfully incorporated into the regional climate model RegCM2 developed by NCAR.The new model has been applied to simulate summer monsoon characteristics and their variations of heavy rainfall process in the Changjiang-Huaihe River Basins for three months from May to July 1991.The results show that the new model can successfully simulate this rainfall prolonged process.By comparising the model outputs of RegCM2.using the Kuo scheme and the MFS.it is found that the MFS is better in simulating the surface temperature,rainfall position and amount,and rainfall duration.  相似文献   

On the state of sublithospheric upper mantle beneath a supercontinent   总被引：2，自引：0，他引：2  

Jun Korenaga  Thomas H. Jordan 《Geophysical Journal International》2002,149(1):179-189

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The time-averaged magnetic field in numerical dynamos with non-uniform boundary heat flow   总被引：2，自引：0，他引：2  

Peter Olson  U. R. Christensen 《Geophysical Journal International》2002,151(3):809-823

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Mantle circulation models with variational data assimilation: inferring past mantle flow and structure from plate motion histories and seismic tomography   总被引：3，自引：0，他引：3  

Hans-Peter Bunge  C. R. Hagelberg  B. J. Travis 《Geophysical Journal International》2003,152(2):280-301

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A comparison of subgrid-scale models for large-eddy simulations of convection in the Earth's core   总被引：2，自引：1，他引：2  

Bruce A. Buffett 《Geophysical Journal International》2003,153(3):753-765

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Time-dependent surface topography in a coupled crust–mantle convection model     

Russell N. Pysklywec  M. Hosein Shahnas 《Geophysical Journal International》2003,154(2):268-278

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