The initial tendency approach is used to diagnose systematic errors in global GRAPES （Global/Regional Assimilation Prediction System）, including overly strong westerlies in the northern midlatitudes, cold/warm bias ...The initial tendency approach is used to diagnose systematic errors in global GRAPES （Global/Regional Assimilation Prediction System）, including overly strong westerlies in the northern midlatitudes, cold/warm bias dipoles in the vicinity of the tropopause, and excessively strong southerlies in downstream regions of the Tibetan Plateau. This approach, involving the use of the assimilation system, focuses on the first few time steps of numerical weather forecasts to identify the deficiencies in diabatic forcing. The results show that there is insufficient diabatic dissipation in the upper troposphere and lower stratosphere of the northern midlatitudes and the lower troposphere of most latitudes, which results from the absence of a parameterization of subgrid orographic drag in global GRAPES. A scheme to parameterize the effects of these drags is therefore tested and the experiments indicate that the newly introduced scheme reduces zonal momentum budget residuals, weakens the northern midlatitude westerlies and southerlies in the downstream regions of the Tibetan Plateau, decreases the cold/warm bias dipoles, and leads to improved objective verification scores.展开更多
The mountain wave induced by a ridge in two-layer stratified fluid has been successfully simulated in a tank.The wave pattern is qualitatively similar to that calculated with linear theory.
Based on the fundamental equations of geophysical fluid dynamics and on the consequence of verticaldensity stratification,travelling wave coordinates are used in this work to study the geometric topologicalstructures ...Based on the fundamental equations of geophysical fluid dynamics and on the consequence of verticaldensity stratification,travelling wave coordinates are used in this work to study the geometric topologicalstructures of nonlinear permanent wave in phase plane.Rigorous mathematical mechanics demonstratethat the solution of permanent solitary wave does not exist.Hamilton functions and 'action-angle' varia-bles are used to express the travelling wave system in the simplest form and the analytic solution of the nonlinear inertia-gravity internal wave is obtained.展开更多
基金Supported by the National Natural Science Foundation of China(41375107 and 41305090)National Science and Technology Support Program of China(2012BAC22B02)China Meteorological Administration Special Public Welfare Research Fund(GYHY201406005)
文摘The initial tendency approach is used to diagnose systematic errors in global GRAPES （Global/Regional Assimilation Prediction System）, including overly strong westerlies in the northern midlatitudes, cold/warm bias dipoles in the vicinity of the tropopause, and excessively strong southerlies in downstream regions of the Tibetan Plateau. This approach, involving the use of the assimilation system, focuses on the first few time steps of numerical weather forecasts to identify the deficiencies in diabatic forcing. The results show that there is insufficient diabatic dissipation in the upper troposphere and lower stratosphere of the northern midlatitudes and the lower troposphere of most latitudes, which results from the absence of a parameterization of subgrid orographic drag in global GRAPES. A scheme to parameterize the effects of these drags is therefore tested and the experiments indicate that the newly introduced scheme reduces zonal momentum budget residuals, weakens the northern midlatitude westerlies and southerlies in the downstream regions of the Tibetan Plateau, decreases the cold/warm bias dipoles, and leads to improved objective verification scores.
基金National Natural Science Foundation of China.partly supported by the President Foundation of Peking Universitythe State Key Project 96-908-02-02 in the Ninth FiveYear Plan.
文摘The mountain wave induced by a ridge in two-layer stratified fluid has been successfully simulated in a tank.The wave pattern is qualitatively similar to that calculated with linear theory.
基金Project supported by NSFC for Youtb(No.B909920106)
文摘Based on the fundamental equations of geophysical fluid dynamics and on the consequence of verticaldensity stratification,travelling wave coordinates are used in this work to study the geometric topologicalstructures of nonlinear permanent wave in phase plane.Rigorous mathematical mechanics demonstratethat the solution of permanent solitary wave does not exist.Hamilton functions and 'action-angle' varia-bles are used to express the travelling wave system in the simplest form and the analytic solution of the nonlinear inertia-gravity internal wave is obtained.
