基于海气耦合环流模式的ENSO预测

Predictions of ENSO are described by using a coupled atmosphere-ocean general circulation model. The initial conditions are created by forcing the coupled system using SST anomalies in the tropical Pacific at the background of the coupled model climatology. A series of 24-month hindcasts for the period from November 1981 to December 1997 are carried out to validate the performance of the coupled system. Correlations of SST anomalies in the Nino3 region exceed 0.54 up to 15 months in advance and the rms errors are less than 0.9℃. The system is more skillful in predicting SST anomalies in the 1980s and less in the 1990s. The model skills are also seasonal-dependent, which are lower for the predictions starting from late autumn to winter and higher for those from spring to autumn in a year-time forecast length. The prediction, beginning from March, persists 8 months long with the correlation skill exceeding 0.6, which is important in predictions of summer rainfall in China. The predictions are succesful in many aspects for the 1997-2000 ENSO events.     

一个有限差分大气环流模式的并行效率

适合于大规模并行处理机（ＭＰＰ）的中国科学院大气物理研究所新一代九层大气环流模式（ＩＡＰ ９Ｌ ＡＧＣＭ）被发展成功。本文描述了并行模式的设计原则，给出了该模式的并行版本在我国几种主要的并行机上的并行执行效率数据。采用消息传递方式（ＭＰＩ）的区域分解方法用于实现程序的并行，结果表明，对于该模式，只有一维区域分解方法才能取得较好的并行可扩展性，即随着处理器的增加而能得到相应较好的并行加速比和并行效率。     

全球变化与区域干旱化

本文总结了已完成的国家重点基础研究发展规划计划项目(“973”项目)“我国生存环境演变和北方干旱化趋势预测”(1999～2004年)和正在执行的“973”项目“北方干旱化与人类适应”的有关干旱化问题研究的部分成果。主要是中国科学院大气物理研究所最近几年在近代区域干旱化的事实及全球联系方面的研究进展,并对全球增暖背景下区域干旱化的形成机理展开讨论。     

Numerical Simulations of Intense Meiyu Rainfall in 1991 over the Changjiang and Huaihe River Valleys by a Regional Climate Model with p-б Incorporated Coordinate System

Based on the primitive equation model with p-σincorporated coordinate system originally developed by Qian et al., a one-way nested fine mesh limited area model is developed. This model is nested with ECMWF T42 data to simulate the extra-intensive rainfall event occurring in the Changjiang and Huaihe River valleys in summer of 1991. The results show that the model has cer-tain capacity to fairly reproduce the regional distribution and the movement of the main rainfall belts. Therefore it can be used as a regional climate model to simulate and predict the short-range regional climate changes.     

Baroclinic Instability in the Generalized Phillips’ Model Part II: Three-layer Model

The nonlinear stability of the three-layer generalized Phillips model, for which the velocity in each layer is constant and the top and bottom surfaces are either rigid or free, is studied by employing Arnol’d’s variational principle and a prior estimate method. The nonlinear stability criteria are established. For com-parison, the linear instability criteria are also obtained by using normal mode method, and the influences of the free parameter, β parameter and curvature in vertical profile of the horizontal velocity on the linear in-stability are discussed by use of the growth rate curves.The comparison between the nonlinear stability criterion and the linear one is made. It is shown that in some cases the two criteria are exactly the same in form, but in other cases, they are different. This phenom-enon, which reveals the nonlinear property of the linear instability features, is explained by the explosive resonant interaction (ERI). When there exists the ERI, i.e., the nonlinear mechanisms play a leading role in the dynamical system, the nonlinear stability criterion is different from the linear one; on the other hand, when there does not exist the ERI, the nonlinear stability criterion is the same as the linear one in form.     

Climatological features of the global tropical subsidence region based on satellite observations

Consisting of subtropical highs and tropical buffer zone, the global tropical subsidence region is the subsidence branches of Hadley cell, Walker circulation and monsoon circulation which are important com-ponents of the global general circulation. This region is closely connected with Asian monsoon. Based on long-term satellite observations of OLR (Outgoing Longwave Radiation) and HIRS-Tbl2 (the bright tem-perature from High-resolution Infra-red Radiation Sounder Channel 12 (6.7μm)), the climatological fea-tures over the global tropical subsidence region are studied in this paper and the main findings are as follows:1) Based on the physical meaning of satellite observed HIRS-12 and comparison with the satellite ob?served OLR and climatological maps of conventional observations of geopotential height and vertical veloc?ity at 500 hPa from NCEP / NCAR reanalysis data, it was found that HIRS-12 might be the best indicator of the global tropical subsidence region from the satellite observations.2) Using satellite observed HIRS-12, some new climatological features were revealed, especially those related with Asian monsoon.3) Comparing the climatological characteristics of tropical subsidence regions between both hemi-spheres, it was found that the circulation in the Northern Hemisphere is more complicated and much closely related with monsoon circulation than that in the Southern Hemisphere. Sudden decay of subsidence movement before monsoon onsets over the South China Sea revealed by HIRS-12 suggested that in the future study of Asian monsoon, it should be paid attention to not only the development of convection but also the variation of tropical subsidence region. It is very useful to monitor the convective and subsidence movements in the tropics by using OLR and HIRS-Tbl2 have been observed from satellite.     

GPS"射线打靶”模式的并行计算

全球定位系统（ＧＰＳ）“射线打靶”模式是ＧＰＳ／ＭＥＴ（气象）资料变分同化中联系ＧＰＳ原始观测与大气状况的一种自成一体的观测算子，但因其计算量非常巨大而一直没能得到实用。为了克服这一困难，我们建立一个并行版本的 ＧＰＳ“射线打靶”模式，并在国家重点基础研究发展规划项目“大规模科学计算研究”资助下研制的微机机群系统（ＬＳＳＣ）上成功地实现了并行计算，取得了理想的加速比和并行效率，而且具有良好的可扩展性，为该观测算子达到实用迈出了实质性的一步。     

我国短期气候动力预测模式系统的研究及试验

气候和气候异常对我国的国民经济发展具有重大影响,为提高短期气候预测的准确率,研究动力气候模式短期气候预测新技术至关重要.通过近5年的努力,建立了一套出月动力延伸预报模式,海气耦合的全球气候模式(AGCM+OGCM+海冰+高分辨率印度洋-太平洋海盆模式),区域气候模式季和年际尺度的业务动力模式组成的系统.初步把我国的短期气候预测水平由经验统计方法提高到定量和客观分析的水平上.在此基础上,已建成了一个具有物理基础的统计方法与气候动力模式相结合的综合气候预报系统.     

Parallel Computing of a Climate Model on the Dawn 1000 by Domain Decomposition Method

ＰａｒａｌｅｌＣｏｍｐｕｔｉｎｇｏｆａＣｌｉｍａｔｅＭｏｄｅｌｏｎｔｈｅＤａｗｎ１０００ｂｙＤｏｍａｉｎＤｅｃｏｍｐｏｓｉｔｉｏｎＭｅｔｈｏｄ①ＢｉＸｕｎｑｉａｎｇ（毕训强）ＩｎｓｔｉｔｕｔｅｏｆＡｔｍｏｓｐｈｅｒｉｃＰｈｙｓｉｃｓ，ＣｈｉｎｅｓｅＡ...     

1998年东亚夏季风过程的数值模拟

The 1998 East Asian Summer Monsoon is simulated by use of an improved nine-level p-σ model, the boundary forcing is the South China Sea Monsoon Experiment (SCSMEX) reanalysis data from May 1 to August 31, 1998. It is found that basic features of the atmospheric circulation (such as the South Asia high and the West Pacific subtropical high) can be simulated fairly. However the South Asia high is a little stronger than the observed, while the West Pacific subtropical high a little weaker. Seen from variations of the time correlation coefficient, this model is good for the short-time climate simulation (less than two months), while for the long-time simulation, its climate drift is a little obvious. It can be also seen from the spatial distribution of correlation coefficient that the worse simulation areas of the model are located in the Tibetan Plateau and the adjacent northwest Indo-China Peninsula. For the simulation of precipitation, the movement of rain belt from May to June can be simulated, but the simulation of July and August precipitation shifts obviously to north of the observed. It is also found from the analysis of sensitive experiment that the improvement of the nested boundary condition has a great impact on the simulation results, especially on the precipitation, so the model and the nesting technique need further improvements.     

A Numerical Study on Effects of Land-Surface Heterogeneity from “Combined Approach” on Atmospheric Process Part I: Principle and Method

A method based on Giorgi (1997a, 1997b) and referred to as ‘combined approach’, which is a combination of mosaic approach and analytical-statistical-dynamical approach, is proposed. Compared with those of other approaches, the main advantage of the combined approach is that it not only can represent both interpatch and intrapatch variability, but also cost less computational time when the land surface heterogeneity is considered. Because the independent variable of probability density function (PDF) is extended to the single valued function of basic meteorological characteristic quantities, which is much more universal, the analytical expressions of the characteristic quantities, (e.g., drag coefficient, snow coverage, leaf surface aerodynamical resistance) affected by roughness length are derived, when the roughness length (and/ or the zero plane displacement) heterogeneity has been mainly taken into account with the approach. On the basis of the rule which the PDF parameters should follow, we choose a function y of the roughness length z0 as the PDF independent variable, and set different values of the two parameters width ratio αn and height ratio γ of PDF (here a linear, symmetric PDF is applied) for sensitivity experiments, from which some conclusions can be drawn, e.g., relevant characteristic terms show different sensitivities to the heterogeneous characteristic (i.e., roughness length), which suggests that we should consider the heterogeneities of the more sensitive terms in our model instead of the heterogeneities of the rest, and which also implies that when the land surface scheme is coupled into the global or regional atmospheric model, sensitivity tests against the distribution of the heterogeneous characteristic are very necessary; when the parameterαn is close to zero, little heterogeneity is represented, andαn differs with cases, which have an upper limit of about 0.6; in the reasonable range ofαn, a peak-like distribution of roughness length can be depicted by a small value ofγ, etc..     

用 IAP／LASG GOALS模式模拟CO2增加引起的东亚地区气候变化

Two simulations, one for the control run and another for the perturbation run, with a global coupled ocean-atmosphere-land system model (IAP / LASG GOALS version 4) have been carried out to study the global warming, with much detailed emphasis on East Asia. Results indicate that there is no climate drift in the control run and at the time of CO2 doubling the global temperature increases about 1.65℃. The GOALS model is able to simulate the observed spatial distribution and annual cycles of temperature and precipitation for East Asia quite well. But, in general, the model underestimates temperature and overestimates rainfall amount for regional annual average. For the climate change in East Asia, the temperature and precipitation in East Asia increase 2. l℃ and 5% respectively, and the maximum warming occurs at middle-latitude continent and the maximum precipitation increase occurs around 25°N with reduced precipitation in the tropical western Pacific.     

Numerical Experiment for the Impact of the Ozone Hole over Antarctica on the Global Climate

A numerical experiment has been carried out with IAP (Institute of Atmospheric Physics) 9-layer general circulation model to investigate the influence of the Antarctic Ozone Hole on the global climate. The results show that the changes of total amount of ozone over higher latitude and polar region of the Southern Hemisphere affect not only the climate in the Southern Hemisphere, but also that in the Northern Hemisphere significantly. In the next spring, although the total amount of ozone over Antarctica has returned to the normal value, the influences of Ozone Hole still exist. Suppported by LASG and the National Key Project of Fundamental Research “Climate Dynamics and Climate Prediction Theory.≓     

“我国南方致洪暴雨监测与预测的理论和方法研究”通过中期评估并获高度评价

由中国气象科学研究院承担的国家重点基础研究发展规划项目“我国南方致洪暴雨监测与预测的理论和方法研究”圆满完成项目任务书规定的研究任务，于2006年12月11～12日顺利通过了中期评估，并获得高度评价。经过研究人员两年的努力，已经在南方致洪暴雨的中尺度结构、机理以及监测与预报理论和方法研究方面取得重要进展，研究成果显示出良好的业务应用前景，圆满完成了头两年任务书所规定的目标与任务，为后3年的研究奠定了良好的基础。     

Nonlinear stability of zonally symmetric quasi-Geostrophic flow

By using the conservation laws and the method of variational principle, an improved Arnol’d’s second nonlinear stability theorem for the two-dimensional multilayer quasi-geostrophic model in periodic chan-nel is obtained.