Abstract:There exist varieties of feedback mechanisms in climate system, and the different description of these climate feedback mechanisms within climate models is one of the major causes for the different responses of these models to the same direct radiative forcing (e.g., doubling CO2). Only when these mechanisms are fully understood and then properly represented, these climate models can be applied to the projection of future climate changes. As the first part of this paper, some basic concepts (e.g., climate sensitivity parameter, cloud radiative forcing, etc.) which are widely used in the analysis of climate feedback mechanism will be introduced, and then several methods will be summarized along with their advantages and shortcomings. The detailed analysis of climate feedback and mechanisms will be given in the second part of this paper.

Abstract:The response of an idealized coastal ocean to traveling storms which move in different directions is studied. The results show that the surges near the shore are mainly caused by forcing waves. As for landing storms, the tidal change due to edge waves is produced in the place which is far way from the storm track. The amplitude of edge waves is much smaller than that of forcing waves in the case of straight coastline and two-dimensional shelf topography. The storm traveling along the coast causes forcing waves which move along the storm near the shore. If the storm moves in the same direction with Kelvin waves, shelf waves are stimulated; otherwise, there is no shelf waves. In addition, the offshore currents associated with storm surges are also analyzed.

Abstract:Some analyses on intraseasonal oscillation in the tropical atmosphere are completed by using the ECMWF data. The results show that there are two kinds of the disturbance pattern, Kelvin wave like and Rossby wave like, in tropical intraseasonal oscillation. The disturbance pattern and the anomaly of the cumulus convection are fundamental factors to affect zonal propagation of tropical intraseasonal oscillation. Accompanying the occurrence of El Ni?o event, the kinetic energy of intraseasonal oscillation in the tropical atmosphere decreases rapidly and the kinetic energy of the quasistationary disturbance increases rapidly, this means the exciting effect of tropical intraseasonal oscillation to El Ni?o event and represents a cause for weaker intraseasonal oscillation during El Ni?o event.

Abstract:In order to undertake the simulation and prediction of ENSO, based on the global oceanic general circulation model with lower resolution developed by the Institute of Atmospheric Physics, Chinese Academy of Sciences, after the introductions of Richardson number dependent vertical diffusion and the physical process of solar short-wave radiation penetration, an oceanic general circulation model of upper tropical Pacific with higher resolution was developed. The numerical simulation studies on the structure and evolution of the temperature and circulation in the tropical Pacific Ocean were performed with this model and the observed atmospheric forcing fields from 1980 to 1995. And focusing on the three dimensional characteristics of ocean and its evolution, the simulated results were validated by using the oceanic assimilated analysis during the same period produced by National Center of Environmental Prediction (NCEP) in USA. At first, the ability of this model to simulate the three dimensional features of the structure of ENSO and their evolution was investigated. It was indicated that: basically, the creation, development and decay of all cold and warm events during the 16 years were modeled correctly. There were some errors in the strength and structure of oceanic temperature anomalies, especially, at the subsurface, in the western equatorial Pacific and along the thermocline, the temperature anomalies were significantly weaker than the observed ones. At the sea surface, the oceanic temperature (SST) anomalies were closer to observation and only larger than the observed in the vicinity of dateline. Then, it was emphasized that, the correct simulation of SST was not enough for the successes of atmosphere-ocean coupled model and the prediction of ENSO, the really stringent was the capabilities of oceanic model simulating the ocean at the subsurface. Therefore, in order to evaluate the oceanic model more comprehensively and approach the reasons of model’s errors, after the regions with the most significant interannual and seasonal variability were found out based on the NCEP oceanic analysis, some statistical amounts, i. e., multiyear averaged state and its seasonal variations, interannual variability and its seasonal variations, were validated. The results indicated that the main features of statistical annual mean states of oceanic temperature and current were simulated correctly, but the errors were also obvious, particularly, there were large systematic errors in the simulations of some oceanic circulation systems at subsurface such as thermocline, equatorial trough, northern equatorial ridge, northern equatorial counter-current trough and equatorial under-current and so on. It was these errors that determine the spatial distributions of the modeling errors of other statistical amounts.

Abstract:Using NMC reanalyzed ocean dataset in 1982~1993, the interannual and seasonal variations of upper level (0~400 m) in the equatorial Pacific (10oS~10oN) are analyzed. The analyses suggest the interannual variation of upper level temperature is larger than that of seasonal variation. In El Nino or La Nina year, the temperature anomalies near thermocline are more significant than those in sea surface since the depth of thermocline changes rapidly. The temperature anomalies near thermocline both in western warm pool and eastern cold tong can reach 7oC or above. In the warm pool the extreme anomalies are often in both side of the equator (4o~9o).

Abstract:The rotated singular value decompostion (RSVD) between the 500 hPa height field anomalies over the Northern Hemisphere the preceding winter and the rainfall in China summer are performed based on both data sets of 45 years in the period of 1951 to 1995. The regional characteristic and the time evolution of the dominant coupled correlation patterns are investigated. The researches show that the regional characteristic of the coupled correlation patterns between the large scale flow patterns during the Northern Hemisphere winter and the rainfall in China summer are identified effectively and have a significant physical sense.

Abstract:A numerical model for an unsaturated flow problem by using finite element method is established in order to simulate liquid moisture flow in an unsaturated zone with homogeneous soil and deep subsurface water, and with different initial and boundary conditions. For infiltration or evaporation problems, a traditional method usually yields oscillatory non-physics profiles. However, we obtain nonoscillatory solutions and evade non-physics solutions for these problems by using the mass-lumped finite element method, Moreover, the kind of boundary conditions is handled very well.

Abstract:In the analysis and comparing of the chemical characteristics of precipitation in different areas, if we list the concrete data of all ions, it is very complicated and difficult to get the conclusion. In this paper, we suggest a simplified method to do it. First, we summarize some most important characteristics with representative alphabets, then divide these characteristics into different levels with representative Arabic numerals. By using a group of this kind of alphebets and numerals, we can describe and compare the main chemical characteristics of precipitation in different area. Based on the generally used observed data, we analyse and compare the typical chemical characteristics of precipitation in the three main acid rain areas.

Abstract:Seven stage cascade impactor was used to collect samples of particulate in the spring and fall 1996 in Beijing in order to study the alkaline component of aerosol in different size range, The capacity of calcium salt and magnesium salt acting as a buffer and neutralizing the acid was compared and included that the calcium salt is the main alkaline component. The acid-soluble Ca2+ ions concentration has strong positive regression with the quantitative change in H+ ions concentration after the particulate was dissolved by acid, and the ratio of alkaline calcium salt to acid-soluble calcium salt didn't show seasonal variations, from coarse mode size range to fine mode size range (from first to seventh stage), this ratio are correspondingly 0.84, 0.76, 0.71, 0.59, 0.53, 0.57, 0.28 and value increase with the size growth. The size distribution of alkaline calcium salt and acid-soluble calcium salt in two seasons are almost same. Based on the experimental result, the content of alkaline calcium salt in particulate matter in different size range in spring and fall at Beijing are calculated.