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numerical Simulation of Global Temperature Change during the 20th Century with the IAP/LASG GOALS Model

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Advances in Atmospheric sciences 2004年第2期21卷 227-235页

作者：马晓燕郭裕福石广玉俞永强 state key laboratory of numerical Modeling for atmospherics sciences and geophysical fluid dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029

The IAP/LASG GOALS coupled model is used to simulate the climate change during the 20th century using historical greenhouse gases concentrations, the mass mixing ratio of sulfate aerosols simulated by a CTM model, and reconstruction of solar variability spanning the period 1900 to 1997. Four simulations, including a control simulation and three forcing simulations, are conducted. Comparison with the observational record for the period indicates that the three forcing experiments simulate reasonable temporal and spatial distributions of the temperature change. The global warming during the 20th century is caused mainly by increasing greenhouse gas concentration especially since the late 1980s; sulfate aerosols offset a portion of the global warming and the reduction of global temperature is up to about 0.11℃ over the century; additionally, the effect of solar variability is not negligible in the simulation of climate change over the 20th century.

关键词： global warming greenhouse gases sulfate aerosols solar variability

Effect of the Lower Boundary Position of the Fourier Equation on the Soil Energy Balance

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Advances in Atmospheric sciences 2004年第6期21卷 868-878页

作者：孙菽芬张霞 state key laboratory of numerical Modeling for atmospherics sciences and geophysical fluid dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029

In this study, the e?ect of the lower boundary position selection for the Fourier equation on heat transfer and energy balance in soil is evaluated. A detailed numerical study shows that the proper position of the lower boundary is critical when solving the Fourier equation by using zero heat ?ux as the lower boundary condition. Since the position de?nes the capacity of soil as a heat sink or source, which absorbs and stores radiation energy from the sky in summer and then releases the energy to the atmosphere in winter, and regulates the deep soil temperature distribution, the depth of the position greatly in?uences the heat balance within the soil as well as the interaction between the soil and the atmosphere. Based on physical reasoning and the results of numerical simulation, the proper depth of the position should be equal to approximately 3 times of the annual heat wave damping depth. For most soils, the proper lower boundary depth for the Fourier equation should be around 8 m to 15 m, depending on soil texture.

关键词： thermal conductivity lower boundary position effect on heat balance

An Evaluation of the Effects of Cloud Parameterization in the R42L9 GCM

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Advances in Atmospheric sciences 2004年第2期21卷 153-162页

作者：吴统文王在志刘屹岷宇如聪吴国雄 state key laboratory of numerical Modeling for atmospherics sciences and geophysical fluid dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 Laboratory for Climate Study National Climate Center Beijing 100081 state key laboratory of numerical Modeling for atmospherics sciences and geophysical fluid dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029

Cloud is one of the uncertainty factors influencing the performance of a general circulation model (GCM). Recently, the state key laboratory of Atmospheric sciences and geophysical fluid dynamics, Institute of Atmospheric Physics (LASG/IAP) has developed a new version of a GCM (R42L9). In this work, roles of cloud parameterization in the R42L9 are evaluated through a comparison between two 20-year simulations using different cloud schemes. One scheme is that the cloud in the model is diagnosed from relative humidity and vertical velocity, and the other one is that diagnostic cloud is replaced by retrieved cloud amount from the International Satellite Cloud Climatology Project (ISCCP), combined with the amounts of high-, middle-, and low-cloud and heights of the cloud base and top from the NCEP. The boreal winter and summer seasonal means, as well as the annual mean, of the simulated top-of-atmosphere shortwave radiative flux, surface energy fluxes, and precipitation are analyzed in comparison with the observational estimates and NCEP reanalysis data. The results show that the scheme of diagnostic cloud parameterization greatly contributes to model biases of radiative budget and precipitation. When our derived cloud fractions are used to replace the diagnostic cloud amount, the top-of-atmosphere and surface radiation fields are better estimated as well as the spatial pattern of precipitation. The simulations of the regional precipitation, especially over the equatorial Indian Ocean in winter and the Asia-western Pacific region in summer, are obviously improved.

关键词： cloud parameterization effect of cloud on model performance R42L9 model climatological cloud scheme diagnostic cloud scheme

Decadal/Interdecadal Variations of the Ocean Temperature and its Impacts on Climate

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Advances in Atmospheric sciences 2006年第6期23卷 964-981页

作者：李崇银周文贾小龙王鑫 state key laboratory of numerical Modeling for atmospherics Science and geophysical fluid dynamics (LASG) Institute of Atmospheric PhysicsChinese Academy of Sciences Beijing 100029 Institute of Meteorology PLA University of Science and TechnologyNanjing 211101 state key laboratory of numerical Modeling for atmospherics Science and geophysical fluid dynamics (LASG) Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029

Decadal/interdecadal climate variability is an important research focus of the CLIVAR Program and has been paid more attention. Over recent years, a lot of studies in relation to interdecadal climate variations have been also completed by Chinese scientists. This paper presents an overview of some advances in the study of decadal/interdecadal variations of the ocean temperature and its climate impacts, which includes interdccadal climate variability in China, the interdecadal modes of sea surface temperature （SST） anomalies in the North Pacific, and in particular, the impacts of interdecadal SST variations on the Asian monsoon rainfall. As summarized in this paper, some results have been achieved by using climate diagnostic studies of historical climatic datasets. Two fundamental interdecadal SST variability modes （7- 10-years mode and 25 35-years mode） have been identified over the North Pacific associated with different anomalous patterns of atmospheric circulation. The southern Indian Ocean dipole （SIOD） shows a major feature of interdecadal variation, with a positive （negative） phase favoring a weakened （enhanced） Asian summer monsoon in the following summer. It is also found that the China monsoon rainfall exhibits interdecadal variations with more wet （dry） monsoon years in the Yangtze River （South China and North China） before 1976, but vice versa after 1976. The weakened relationship between the Indian summer rainfall and ENSO is a feature of interdecadal variations, suggesting an important role of the interdecadal variation of the SIOD in the climate over the south Asia and southeast Asia. In addition, evidence indicates that the climate shift in the 1960s may be related to the anomalies of the North Atlantic Oscillation （NAO） and North Pacific Oscillation （NPO）. Overall, the present research has improved our understanding of the decadal/interdecadal variations of SST and their impacts on the Asian monsoon rainfall. However, the research also highlights a n

关键词： decadal/interdecadal variation climate change Southern Indian Ocean dipole monsoonrainfall

The Characteristics of Climate Change over the Tibetan Plateau in the Last 40 Years and the Detection of Climatic Jumps

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Advances in Atmospheric sciences 2004年第2期21卷 193-203页

作者：牛涛陈隆勋周自江 Chinese Academy of Meteorological sciences Beijing 100081 State Key Laboratory of Numerical Modeling for Atmospherics Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 Chinese Academy of Meteorological sciences Beijing 100081 National Meteorological Center Beijing 100081

Through analyzing the yearly average data obtained from 123 regular meteorological observatories located in the Tibetan Plateau (T-P), this article studies the characteristics of climate change in T-P in the last 40 years. Prom the distribution of the linear trend, it can be concluded that the southeastern part of T-P becomes warmer and wetter, with an obvious increase of rainfall. The same characteristics are found in the southwestern part of T-P, but the shift is smaller. In the middle of T-P, temperature and humidity obviously increase with the center of the increase in Bangoin-Amdo. The south of the Tarim Basin also exhibits the same tendency. The reason for this area being humid is that it gets less sunshine and milder wind. The northeastern part of T-P turns warmer and drier. Qaidam Basin and its western and southern areas are the center of this shift, in which the living environment is deteriorating. Analyzing the characteristics of the regional average time series, it can be found that in the mid-1970s, a significant sudden change occurred to annual rainfall, yearly average snow-accumulation days and surface pressure in the eastern part of T-P. In the mid-1980s, another evident climatic jump happened to yearly average temperature, total cloud amount, surface pressure, relative humidity, and sunshine duration in the same area. That is, in the mid 1980s, the plateau experienced a climatic jump that is featured by the increase of temperature, snow-accumulation days, relative humidity, surface pressure, and by the decrease of sunshine duration and total cloud amount. The sudden climatic change of temperature in T-P is later than that of the global-mean temperature. Prom this paper it can be seen that in the middle of the 1980s, a climatic jump from warm-dry to warm-wet occurred in T-P.

关键词： Tibetan Plateau linear trend climatic jump

Parallel Computing of a Variational Data Assimilation Model for GPS/MET Observation Using the Ray-Tracing Method

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Advances in Atmospheric sciences 2004年第2期21卷 220-226页

作者：张昕刘月巍王斌季仲贞 key laboratory of Pure and Applied Mathematics Center for Computational Science and EngineeringSchool of Mathematical Sciences Peking University Beijing 100871 National Meteorological Center Beijing 100081 National Meteorological Center Beijing 100081 state key laboratory of numerical Modeling for atmospherics sciences and geophysical fluid dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029

The Spectral Statistical Interpolation (SSI) analysis system of NCEP is used to assimilate meteorological data from the Global Positioning Satellite System (GPS/MET) refraction angles with the variational technique. Verified by radiosonde, including GPS/MET observations into the analysis makes an overall improvement to the analysis variables of temperature, winds, and water vapor. However, the variational model with the ray-tracing method is quite expensive for numerical weather prediction and climate research. For example, about 4 000 GPS/MET refraction angles need to be assimilated to produce an ideal global analysis. Just one iteration of minimization will take more than 24 hours CPU time on the NCEP's Cray C90 computer. Although efforts have been taken to reduce the computational cost, it is still prohibitive for operational data assimilation. In this paper, a parallel version of the three-dimensional variational data assimilation model of GPS/MET occultation measurement suitable for massive parallel processors architectures is developed. The divide-and-conquer strategy is used to achieve parallelism and is implemented by message passing. The authors present the principles for the code's design and examine the performance on the state-of-the-art parallel computers in China. The results show that this parallel model scales favorably as the number of processors is increased. With the Memory-IO technique implemented by the author, the wall clock time per iteration used for assimilating 1420 refraction angles is reduced from 45 s to 12 s using 1420 processors. This suggests that the new parallelized code has the potential to be useful in numerical weather prediction (NWP) and climate studies.

关键词： parallel computing variational data assimilation GPS/MET

On Nonlinear Stability Theorems of 3D Quasi-geostrophic Flow

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Advances in Atmospheric sciences 2006年第5期23卷 809-814页

作者：刘永明蔡景景 key laboratory of Geographic Information Science Ministry of Education East China Normal University Shanghai 200062 State Key Laboratory of Numerical Modeling for Atmospherics Sciences and Geophysical Fluid DynamicsInstitute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 Department of Mathematics East China Normal University Shanghai 200062 Department of Mathematics East China Normal University Shanghai 200062

Nonlinear stability criteria for quasi-geostrophic zonally symmetric flow are improved by establishing an optimal Poincard inequality. The inequality is derived by a variational calculation considering the additional invariant of zonal momentum. When applied to the Eady model in a periodic channel with finite zonal length, the improved nonlinear stability criterion is identical to the linear normal-mode stability criterion provided the channel meridional width is no greater than 0.8605... times its channel length （which is the geophysically relevant case）.

关键词： 3D-Quasi-geostrophic flow Nonlinear stability Eady model

An Empirical Formula to Compute Snow Cover Fraction in GCMs

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Advances in Atmospheric sciences 2004年第4期21卷 529-535页

作者：吴统文吴国雄 state key laboratory of numerical Modeling for atmospherics sciences and geophysical fluid dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 Laboratory for Climate Study National Climate Center Beijing 100081 state key laboratory of numerical Modeling for atmospherics sciences and geophysical fluid dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029here exists great uncertainty in parameterizing snow cover fraction in most general circulation models (GCMs) using various empirical formulae which has great influence on the performance of GCMs. This work reviews the commonly used relationships between region-averaged snow depth (or snow water equivalent) and snow cover extent (or fraction) and suggests a new empirical formula to compute snow cover fraction which only depends on the domain-averaged snow depth for GCMs with different horizontal resolution. The new empirical formula is deduced based on the 10-yr (1978-1987) 0.5°×0.5°weekly snow depth data of the scanning multichannel microwave radiometer (SMMR) driven from the Nimbus-7 Satellite. Its validation to estimate snow cover for various GCM resolutions was tested using the climatology of NOAA satellite-observed snow cover.

There exists great uncertainty in parameterizing snow cover fraction in most general circulation models (GCMs) using various empirical formulae, which has great influence on the performance of GCMs. This work reviews the commonly used relationships between region-averaged snow depth (or snow water equivalent) and snow cover extent (or fraction) and suggests a new empirical formula to compute snow cover fraction, which only depends on the domain-averaged snow depth, for GCMs with different horizontal resolution. The new empirical formula is deduced based on the 10-yr (1978-1987) 0.5°× 0.5° weekly snow depth data of the scanning multichannel microwave radiometer (SMMR) driven from the Nimbus-7 Satellite. Its validation to estimate snow cover for various GCM resolutions was tested using the climatology of NOAA satellite-observed snow cover.

关键词： snow cover fraction parameterization satellite derived snow depth GCM