Modeling And Numerical Simulation Of Paleoclimate Reconstruction In The Northern Hemisphere And China

The rareness and inhomogeneity of the proxy data points bring many difficulties for the climate reconstruction. And the existing methods are based on an assumption that the major spatial patterns of the temperature field obtained in the period having measured data were also the main spatial patterns in the other periods. The optimal regional averaging method that is suitable for obtaining the average temperature of the region where the proxy data is rare and inhomogeneous is applied to reconstruct the average temperature of the northern hemisphere and China in this paper. The influence of the number and spatial distribution of stations and the various paramenters of this method on the reconstruction results are discussed. On the basis, we combine the optimal regional averaging method and the spherical harmonic analysis method to reconstruct the past thousand year average temperature in the northern hemisphere, which overcomes the defect of the past research, which assumped that the major spatial patterns of the temperature field obtained in the period having measured data were also the main spatial patterns in the other periods. And the main works are as follows:1. Targeting at the question of the covariance pattern in the optimal regional averaging method only suitable for getting the average in small region, the covariance pattern for large region is calculated by meshing summation of the covariance pattern for small region. The average temperature of the northern hemisphere is got by the optimal regional averaging method, and the results are verified through comparing with the published data. And the influence of the number and spatial distribution of data points on the results obtained from the optimal averaging method are discussed. And the result shows that10data points with reasonable distribution can get a available average temperature in the reconstruction of the northern hemisphere, which is far less than the data points needed by other method.2. The optimal regional averaging method and the proxy data-Maximum Latewood Density Temperature Sequence Dataset are applied to reconstruct the past500year average temperature in the northern hemisphere, and the results is very well with the previous studies even if the number of data points is less than other studies;3. The optimal regional averaging method, a new scheme for climate regionalization in China regional average and the measured temperature data from Dataset of Surface Climatic Information in China are used to get the average temperature in China4. Aim at the questions that the weights change only with space and do not change with time in past research and the question existed in the solving of covariance pattern, the spherical harmonic analysis method is introduced to calculate the global temperature field. The covariance pattern is caculated directly through the temperatures of all the sites by the spherical harmonic analysis method. And then weights changing with space and time are got by the optimal regional averaging method. The past thounsand year average temperature are reconstructed with the data points less than that of other methods. The results are in good consistent with the results of predecessors.