Upland red soil has strong acidity and low fertility, different woodland types produce varying impacts on soil properties and nematode communities. To explore the response of soil, 2 different types of woodland were s...Upland red soil has strong acidity and low fertility, different woodland types produce varying impacts on soil properties and nematode communities. To explore the response of soil, 2 different types of woodland were selected to investigate the changes of soil properties and nematode communities compared to wasteland. The results showed that the content of soil organic carbon and total nitrogen in chestnut forest soil were the highest, 16.41 g/kg and 0.46 g/kg respectively; while the highest contents of soil microbial biomass carbon, nitrogen and phosphorus appeared in wasteland soil, and basal respiration of wasteland soil was 28.36 mg CO_2/kg·d, significantly higher than that of the other 2 soils(p <0.05). The nematode abundance also reached the peak in wasteland soil. Three types of soil exhibited a completely different nematode community structure: the dominant trophic group in wasteland soil was herbivores,while omnivores/predators and bacterivores in forest from farmland and chestnut forest soil, respectively.The influence of different types of woodland on ecological indices of nematode communities was not consistent. Degradation trends of soil properties and nematode communities were presented in the 2woodland types compared with wasteland soil. These results are instructive for the local woodland planning.展开更多
In order to compare and evaluate the performances of the Laplacian viscosity closure, the biharmonic viscosity closure, and the Leith closure momentum schemes in the MPAS-Ocean model, a variety of physical quantities,...In order to compare and evaluate the performances of the Laplacian viscosity closure, the biharmonic viscosity closure, and the Leith closure momentum schemes in the MPAS-Ocean model, a variety of physical quantities, such as the relative reference potential energy(RPE) change, the RPE time change rate(RPETCR), the grid Reynolds number, the root mean square(RMS) of kinetic energy, and the spectra of kinetic energy and enstrophy, are calculated on the basis of results of a 3D baroclinic periodic channel. Results indicate that: 1) The RPETCR demonstrates a saturation phenomenon in baroclinic eddy tests. The critical grid Reynolds number corresponding to RPETCR saturation differs between the three closures: the largest value is in the biharmonic viscosity closure, followed by that in the Laplacian viscosity closure, and that in the Leith closure is the smallest. 2) All three closures can effectively suppress spurious dianeutral mixing by reducing the grid Reynolds number under sub-saturation conditions of the RPETCR, but they can also damage certain physical processes. Generally, the damage to the rotation process is greater than that to the advection process. 3) The dissipation in the biharmonic viscosity closure is strongly dependent on scales. Most dissipation concentrates on small scales, and the energy of small-scale eddies is often transferred to large-scale kinetic energy. The viscous dissipation in the Laplacian viscosity closure is the strongest on various scales, followed by that in the Leith closure. Note that part of the small-scale kinetic energy is also transferred to large-scale kinetic energy in the Leith closure. 4) The characteristic length scale L and the dimensionless parameter Г in the Leith closure are inherently coupled. The RPETCR is inversely proportional to the product of Г and L. When the product of Г and L is constant, both the simulated RPETCR and the inhibition of spurious dianeutral mixing are the same in all tests using the Leith closure. The dissipative scale in the Leith closure depends on the parameter L, and the dissipative intensity depends on the parameter Г. 5) Although optimal results may not be achieved by using the optimal parameters obtained from the 2D barotropic model in the 3D baroclinic simulation, the total energies are dissipative in all three closures. Dissipation is the strongest in the biharmonic viscosity closure, followed by that in the Leith closure, and that in the Laplacian viscosity closure is the weakest. Mesoscale eddies develop the fastest in the biharmonic viscosity closure after the baroclinic adjustment process finishes, and the kinetic energy reaches its maximum, which is attributed to the smallest dissipation of enstrophy in the biharmonic viscosity closure. Mesoscale eddies develop the slowest, and the kinetic energy peak value is the smallest in the Laplacian viscosity closure. Results in the Leith closure are between that in the biharmonic viscosity closure and the Laplacian viscosity closure.展开更多
In order to quantitatively evaluate the spurious dianeutral mixing in a global ocean model MPAS-Ocean(Model for Prediction Across Scales) using a spherical centroidal voronoi tessellations developed jointly by the Nat...In order to quantitatively evaluate the spurious dianeutral mixing in a global ocean model MPAS-Ocean(Model for Prediction Across Scales) using a spherical centroidal voronoi tessellations developed jointly by the National Center for Atmospheric Research and the Los Alamos National Laboratory in the United States, we choose z* vertical coordinate system in MPAS-Ocean, in which all physical mixing processes, such as convection adjustment and explicit diffusion parameter schemes, are omitted, using a linear equation of state. By calculating the Reference Potential Energy(RPE), front revolution position, time rate of RPE change, probability density function distribution and dimensionless parameter χ, from the perspectives of resolution, viscosity, Horizontal Grid Reynolds Number(HGRN), Re?, and momentum transmission scheme, using two ideal cases, overflow and baroclinic eddy channel, we qualitatively analyze the simulation results by comparison with the three non-isopycnal models in Ilicak et al.(2012), i.e., MITGCM, MOM, and ROMS. The results show that the spurious dianeutral mixing in the MPAS-Ocean increases over time. The spurious dianeutral transport is proportional to the HGRN directly and is reduced by increasing the lateral viscosity or using a finer resolution to control HGRN. When the HGRN is less than 10, spurious transport is reduced significantly. When using the proper viscosity closure, MPAS-Ocean performs better than MITGCM and MOM, closely to ROMS, in the 2D case without rotation, and much better than the above-mentioned three ocean models under the condition of 3D space with rotation due to the cell area difference between the hexagon cell and the quadrilateral cell with the same resolution. Both the Zalesak(1979) flux corrected transport scheme and Leith closure in MPAS-Ocean play an excellent role in reducing spurious dianeutral mixing. The performance of Leith scheme is preferable to the condition of three-dimensional baroclinic eddy.展开更多
利用MPAS-A(The Model for Prediction Across Scales-Atmosphere)模式设计了中东太平洋热带辐合带CEP-ITCZ(Intertropical Convergence Zone over Central and Eastern Pacific)对两类厄尔尼诺SST(Sea Surface Temperature)异常的敏感...利用MPAS-A(The Model for Prediction Across Scales-Atmosphere)模式设计了中东太平洋热带辐合带CEP-ITCZ(Intertropical Convergence Zone over Central and Eastern Pacific)对两类厄尔尼诺SST(Sea Surface Temperature)异常的敏感性试验,通过试验结果与两类厄尔尼诺年实际大气异常的对比,初步解释了CEP-ITCZ在两类厄尔尼诺年产生不同异常的可能原因。通过CP-EL试验发现,热带太平洋SST异常的第一模态会使中东太平洋低层风场辐合增强,但对辐合带的位置影响不大,与中部型厄尔尼诺对CEP-ITCZ的影响基本一致。通过EP-EL试验发现,热带太平洋SST异常的第二模态会使中东太平洋低层风场产生较大异常,辐合带中心向南移动,辐合带明显减弱增宽,与东部型厄尔尼诺对CEP-ITCZ的影响基本一致。展开更多
基金Sponsored by National Youth Natural Science Foundation of China(41301235)
文摘Upland red soil has strong acidity and low fertility, different woodland types produce varying impacts on soil properties and nematode communities. To explore the response of soil, 2 different types of woodland were selected to investigate the changes of soil properties and nematode communities compared to wasteland. The results showed that the content of soil organic carbon and total nitrogen in chestnut forest soil were the highest, 16.41 g/kg and 0.46 g/kg respectively; while the highest contents of soil microbial biomass carbon, nitrogen and phosphorus appeared in wasteland soil, and basal respiration of wasteland soil was 28.36 mg CO_2/kg·d, significantly higher than that of the other 2 soils(p <0.05). The nematode abundance also reached the peak in wasteland soil. Three types of soil exhibited a completely different nematode community structure: the dominant trophic group in wasteland soil was herbivores,while omnivores/predators and bacterivores in forest from farmland and chestnut forest soil, respectively.The influence of different types of woodland on ecological indices of nematode communities was not consistent. Degradation trends of soil properties and nematode communities were presented in the 2woodland types compared with wasteland soil. These results are instructive for the local woodland planning.
基金sponsored by the National Natural Science Foundation of China Program (No.41175089)
文摘In order to compare and evaluate the performances of the Laplacian viscosity closure, the biharmonic viscosity closure, and the Leith closure momentum schemes in the MPAS-Ocean model, a variety of physical quantities, such as the relative reference potential energy(RPE) change, the RPE time change rate(RPETCR), the grid Reynolds number, the root mean square(RMS) of kinetic energy, and the spectra of kinetic energy and enstrophy, are calculated on the basis of results of a 3D baroclinic periodic channel. Results indicate that: 1) The RPETCR demonstrates a saturation phenomenon in baroclinic eddy tests. The critical grid Reynolds number corresponding to RPETCR saturation differs between the three closures: the largest value is in the biharmonic viscosity closure, followed by that in the Laplacian viscosity closure, and that in the Leith closure is the smallest. 2) All three closures can effectively suppress spurious dianeutral mixing by reducing the grid Reynolds number under sub-saturation conditions of the RPETCR, but they can also damage certain physical processes. Generally, the damage to the rotation process is greater than that to the advection process. 3) The dissipation in the biharmonic viscosity closure is strongly dependent on scales. Most dissipation concentrates on small scales, and the energy of small-scale eddies is often transferred to large-scale kinetic energy. The viscous dissipation in the Laplacian viscosity closure is the strongest on various scales, followed by that in the Leith closure. Note that part of the small-scale kinetic energy is also transferred to large-scale kinetic energy in the Leith closure. 4) The characteristic length scale L and the dimensionless parameter Г in the Leith closure are inherently coupled. The RPETCR is inversely proportional to the product of Г and L. When the product of Г and L is constant, both the simulated RPETCR and the inhibition of spurious dianeutral mixing are the same in all tests using the Leith closure. The dissipative scale in the Leith closure depends on the parameter L, and the dissipative intensity depends on the parameter Г. 5) Although optimal results may not be achieved by using the optimal parameters obtained from the 2D barotropic model in the 3D baroclinic simulation, the total energies are dissipative in all three closures. Dissipation is the strongest in the biharmonic viscosity closure, followed by that in the Leith closure, and that in the Laplacian viscosity closure is the weakest. Mesoscale eddies develop the fastest in the biharmonic viscosity closure after the baroclinic adjustment process finishes, and the kinetic energy reaches its maximum, which is attributed to the smallest dissipation of enstrophy in the biharmonic viscosity closure. Mesoscale eddies develop the slowest, and the kinetic energy peak value is the smallest in the Laplacian viscosity closure. Results in the Leith closure are between that in the biharmonic viscosity closure and the Laplacian viscosity closure.
基金supported by the National Natural Science Foundation of China (Grant No.41175089)
文摘In order to quantitatively evaluate the spurious dianeutral mixing in a global ocean model MPAS-Ocean(Model for Prediction Across Scales) using a spherical centroidal voronoi tessellations developed jointly by the National Center for Atmospheric Research and the Los Alamos National Laboratory in the United States, we choose z* vertical coordinate system in MPAS-Ocean, in which all physical mixing processes, such as convection adjustment and explicit diffusion parameter schemes, are omitted, using a linear equation of state. By calculating the Reference Potential Energy(RPE), front revolution position, time rate of RPE change, probability density function distribution and dimensionless parameter χ, from the perspectives of resolution, viscosity, Horizontal Grid Reynolds Number(HGRN), Re?, and momentum transmission scheme, using two ideal cases, overflow and baroclinic eddy channel, we qualitatively analyze the simulation results by comparison with the three non-isopycnal models in Ilicak et al.(2012), i.e., MITGCM, MOM, and ROMS. The results show that the spurious dianeutral mixing in the MPAS-Ocean increases over time. The spurious dianeutral transport is proportional to the HGRN directly and is reduced by increasing the lateral viscosity or using a finer resolution to control HGRN. When the HGRN is less than 10, spurious transport is reduced significantly. When using the proper viscosity closure, MPAS-Ocean performs better than MITGCM and MOM, closely to ROMS, in the 2D case without rotation, and much better than the above-mentioned three ocean models under the condition of 3D space with rotation due to the cell area difference between the hexagon cell and the quadrilateral cell with the same resolution. Both the Zalesak(1979) flux corrected transport scheme and Leith closure in MPAS-Ocean play an excellent role in reducing spurious dianeutral mixing. The performance of Leith scheme is preferable to the condition of three-dimensional baroclinic eddy.
文摘利用MPAS-A(The Model for Prediction Across Scales-Atmosphere)模式设计了中东太平洋热带辐合带CEP-ITCZ(Intertropical Convergence Zone over Central and Eastern Pacific)对两类厄尔尼诺SST(Sea Surface Temperature)异常的敏感性试验,通过试验结果与两类厄尔尼诺年实际大气异常的对比,初步解释了CEP-ITCZ在两类厄尔尼诺年产生不同异常的可能原因。通过CP-EL试验发现,热带太平洋SST异常的第一模态会使中东太平洋低层风场辐合增强,但对辐合带的位置影响不大,与中部型厄尔尼诺对CEP-ITCZ的影响基本一致。通过EP-EL试验发现,热带太平洋SST异常的第二模态会使中东太平洋低层风场产生较大异常,辐合带中心向南移动,辐合带明显减弱增宽,与东部型厄尔尼诺对CEP-ITCZ的影响基本一致。
