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A one-dimensional heat transfer model of the Antarctic ice Sheet and modeling of snow temperatures at Dome A, the summit of Antarctic Plateau

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Science China Earth Sciences 2010年第5期53卷 763-772页

A vertical one-dimensional numerical model for heat transferring within the near-surface snow layer of the Antarctic ice Sheet was developed based on simplified parameterizations of associated physical processes for the atmosphere, radiation, and snow/ice systems. Using the meteorological data of an automatic weather station (AWS) at Dome A (80°22′S, 70°22′E), we applied the model to simulate the seasonal temperature variation within a depth of 20 m. comparison of modeled results with observed snow temperatures at 4 measurement depths (0.1, 1, 3. 10 m) shows good agreement and consistent seasonal variations. The model results reveal the vertical temperature structure within the near-surface snow layer and its seasonal variance with more details than those by limited measurements. Analyses on the model outputs of the surface energy fluxes show that: 1) the surface energy balance at Dome A is characterized by the compensation between negative net radiation and the positive sensible fluxes, and 2) the sensible heat is on average transported from the atmosphere to the snow, and has an evident increase in spring. The results are considered well representative for the highest interior Antarctic Plateau.

关键词： Antarctic ice Sheet near-surface layer energy transfer numerical model

Artificial Neural Network for combining Forecasts

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Journal of Systems Engineering and Electronics 1995年第2期6卷 58-64页

作者： Shanming Shi, Li D. Xu & Bao Liu(Department of computer Science, university of colorado at boulder, boulder, co {3., usa)(Department of MSIS, Wright State university, Dayton, OH 4543.,usa)(Institute of Systems Engineering, Tianjin university, Tianjin 3. Department of computer Science University of Colorado at Boulder CO 80309 USA Department of MSIS Wright State University Dayton OH 45435 USA Institute of Systems Engineering Tianjin University Tianjin 300072 China

This paper proposes artificial neural networks (ANN) as a tool for nonlinear combination of forecasts. In this study, three forecasting models are used for individual forecasts, and then two linear combining methods are used to compare with the ANN combining method. The comparative experiment using real--world data shows that the prediction by the ANN method outperforms those by linear combining methods. The paper suggests that the ANN combining method can be used as- an alternative to conventional linear combining methods to achieve greater forecasting accuracy.

关键词： Artificial neural network,Forecasting combined forecasts Nonlinear systems.

Water Vapor Variability in the Tropical Western Pacific from 20-year Radiosonde data

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Advances in Atmospheric Sciences 2001年第5期18卷 752-766页

作者： Junhong Wang, Harold L. cole and David J. Carlson National center for Atmospheric Research P. O, Box 3.00,boulder, co 803.7 National center for Atmospheric Research

The 20-year (1976-1995) daily radinsonde data at 17 stations in the tropical western Pacific was ana- lyzed. The analysls shows that the atmosphere is more humid in a warmer climate on seasonal,inter-annual and long-term (20-year) time scales, implying a positive water vapor feedback The vertlcal structure of the long-term trends in relative humidity (RH) is distinct from that on short-term (seasonal and inter-annual) time scales, suggesting that observed water vapor changes on short time scales could not be considered as a surrogate of long-term climate change. The increasing trend of RH (3.-5% / decade) in the upper troposphere is stronger than that in the lower troposphere (1 %-2% / decade). Such verthal structure would amplify positive water vapor feedback in comparison to the common assumption of constant RH changes vertically. The empicical orthogonal function (EOF) analysis of vertical structure of RH varmtions shows distinct features of the vert1cal structure of the first three EOFs. The first three EOFs are optimal for repre- sentation of water vapor profiles and provide some hints on physical mechanisms respons1ble for observed humidity variability. Vaisala radiosondes were used at nine stations, and VIZ radiosondes used at other eight stations The Vaisala data are corrected for temperature-dependence error using the correction siheme developed by NCAR / ATD and Vaisala. The comparison of Vaisala and VIZ data shows that the VIZ-measured RHs after October 1993.have a moist bias of - 10% at RHs 5, several changes in- cluding both instruments and reporting pract{3. have been made at Vaisala stations and introduce errors to long-term RH variations.

关键词： Water vapor Radiosonde

Study of ozone “weekend effect” in Shanghai

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Science China Earth Sciences 2008年第9期51卷 1354-1360页

作者： TANG WenYuan1↑, ZHAO ChunSheng1, GENG FuHai1,2, PENG Li2, ZHOU GuangQiang2, GAO Wei2, XU JianMing2 & TIE XueXi2,3.1 Department of Atmospheric Science, School of Physics, Peking university, Beijing 100871, China 2 Atmospheric Chemistry Laboratory of Shanghai Meteorological Bureau, Shanghai 20003., China 3.Atmospheric Chemistry Division, NCAR, boulder co 803.1, usa Department of Atmospheric Science School of Physics Peking University Beijing China Atmospheric Chemistry Laboratory of Shanghai Meteorological Bureau Shanghai China Atmospheric Chemistry Division NCAR Boulder USA

Analysis of observed ozone data in 2006 from five monitoring sites (Xujiahui, Chongming, Baoshan, Pudong, Jinshan) in Shanghai reveals that ozone (O_3. concentrations in Xujiahui are higher at week-ends than those on weekdays, despite the fact that emissions of ozone precursor substances, such as oxides of nitrogen (NOx), carbon monoxide (co) and volatile organic compounds (VOCs) are lower at weekends than those on weekdays. The possible chemical cause of ozone "weekend effect" is that NO_2/NO ratio increases at weekends by 25.61% compared with those on weekdays. In addition, because of an average 12.13. reduction in NOx (NO + NO_2) in the early morning (05:00-09:00) at weekends compared with that on weekdays, the ozone inhibition period ends 0.5 h earlier at weekends resulting in the longer duration of ozone accumulation and the higher ozone production rate. The rate of ozone production is a function of VOCs and NOx in the atmosphere. VOCs/NOx ratio in Xujiahui is 4.55 at weekends, and 4.3. on weekdays, belonging to the "NOx-limited". The increasing VOCs/NOx ratio at weekends leads to ozone enhancement from 73.ppbv to 80 ppbv, which are consistent with ozone "weekend effect" in Xujiahui. Furthermore, combining with MICAPS cloud amount data, the fact that ozone "weekend effect" in Xujiahui weakens gradually along with the increasing of cloud amount indicates that ozone photochemical production leads to ozone "weekend effect" in Xujiahui of Shanghai.

关键词： Shanghai ozone photochemical pollution "weekend effect"

Atmospheric Methane over the Past 2000 Years from a Sub-tropical ice core, Central Himalayas

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Journal of Mountain Science 2010年第1期7卷 1-14页

作者： LI Jiule XU Baiqing YAO Tandong WANG Ninglian Ken MacClune Laboratory of Tibetan Environment Changes and Land Surface Processes Chinese Academy of Sciences Beijing 100085 China State Key Laboratory of Cryospheric Science Chinese Academy of Sciences Lanzhou 730000 China Stable Isotope Laboratory Institute ofArctic andAlpine Research University of Colorado Boulder Colorado CO 80303 USA

A high-resolution 2ooo-year methane record has been constructed from an ice core recovered at 7200 m a.s.1, on the Dasuopu Glacier in the central Himalayas. This sub-tropical methane record reveals an increasing trend in the concentration of methane during the industrial era that is similar to observations from polar regions. However, we also observed the differences in the atmospheric methane mixing ratio between this monsoon record and those from polar regions during pre-industrial times. In the time interval o N 1850 A.D., the average methane concentration in the Dasuopu ice core was 782±40 ppbv and the maximum temporal variation exceeded 200 ppbv. The difference gradient of methane concentration in Dasuopu ice core with Greenland and Antarctica cores are 66±40 ppbv and 107±40 ppbv, respectively. This suggests that the tropical latitudes might have acted as a major global methane source in preindustrial times. In addition, the temporal fluctuation of the pre-industrial methane records suggests that monsoon evolution incorporated with high methane emission from south Asia might be responsible for the relatively high methane concentration observed in the Dasuopu ice core around A.D. 800 and A.D. 1600. These results provide a rough understanding of the contribution of tropical methane source to the global methane budget and also the relationship betweenatmospheric methane and climate change.

关键词： climate change ice core air bubble atmospheric methane Dasuopu Glacier centralHimalayas

Observation　of　clouds　and　solar　radiation　over　the　Pacific　Ocean　as　relation　to　global　climate

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Acta Oceanologica Sinica 1995年第2期14卷 201-207页

作者： Farn Parungo Clarence Nagamoto Cecilia M. I. R. Girz Jeff Torgerson and Zhou Mingyu (Science and Technology corporation, boulder, co, U. S. A.Air Resources Laboratory, NOAA, boulder, co, U. S. A.Forecast Systems Laboratory, NOAA, boulder, co, U. S. A.U

During a research cruise over the Pacific Ocean in 1989, solar irradiance was measured with a broad-band pyranometer along the cruise track. Cloud cover was photographed with an all-sky time-lapse came ra. Cloud types were observed and recorded. The data show that both the types and the amounts of clouds affect radiation fluxes on the sea surface. For low-level and middle-level clouds, the correlations (r) between measured irradiance (in Percent of calculated maximum irradiance) and cloud amount (in fraction of sky) were significant: r=-0. 79 and - 0. 66, respectively. For high-level clouds, the correlation was not significant: r=-0. 21. The results indicate that cloud shortwave forcing is a major modifier of the earth's surface insolation and change of cloud amount may affect global climate.

关键词： Solar irradiance cloud type cloud cover earth's surface insolation global climate

Seasonal water storage change of the Yangtze River basin detected by GRACE

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Science China Earth Sciences 2006年第5期49卷 483-491页

作者： HU Xiaogong1, CHEN Jianli1,2, ZHOU Yonghong1, HUANG Cheng1 & LIAO Xinhao1 1. center for Astro-geodynamics Research, Shanghai Astronomical Observatory, National Astronomical Observatories, Shanghai 20003., China 2. center for Space Research, university of Texas at Austin, 3.25 W. Braker Lane, Suite 200, Austin, TX78750,{3. center for Astro-geodynamics Research Shanghai Astronomical Observatory National Astronomical Observatories Shanghai China center for Space Research University of Texas at Austin Austin USA

US-Germany co-sponsered satellite gravimetry mission GRACE (Gravity Recovery And Climate Experiment), launched in March 2002, has been producing monthly time series of Earth gravity models up to degree and order of 120. The GRACE mission consists of two identical satellites flying on an almost polar orbit with an altitude of about 3.0-500 km and satelite-to-satellite ranging of about 220 km. Thanks to the payloads of space-borne GPS receivers, accelerometers and high-precision K-band satelite-to-satellite ranging mesurements, GRACE gravity models are expected to achieve more than one order of magnitude of improvement over previous models at spatial scales of a few hundred kilometers or larger. Recovery of surface mass re-distribution based on GRACE’s time-varying gravity models is applied to studies in solid Earth geophysics, oceanography, climatology and geodesy. At secular time scales, GRACE is expected to provide valuable information on global ice changes, whose variations have profound influences on global climate, and in particular, on sea level changes. At seasonal time scales, GRACE is expected to reveal surface water changes with an ac- curacy of less than 1 cm, or ocean bottom pressure changes with an accuracy of less than 1 mbar (1 mbar =102 Pa). These surface mass redistribution measurements would impove our understanding of the global and regional mass and energy cycles that are critical to human life. Using 15 GRACE monthly gravity models covering the period from April 2002 to December 2003. this study compares seasonal water storage changes recovered from GRACE data and hydrology models at global and regional scales, with particular focus on the Yangtze River basin of China. Annual amplitude of 3.4 cm of equivalent water height change is found for the Yangtze River basin with maximum in Spring and Autumn, agreeing with two state-of-the-art hydrology models. The differences between GRACE re- sults and model predictions are less than 1-2 cm. We conclude

关键词： GRACE, earth gravity, water storage, Yangtze River basin.

Effect of aerosols on visibility and radiation in Tianjin,China

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Effect of aerosols on visibility and radiation in Tianjin,Ch...

一种采用时域仿真器进行开关变换的小信号自动分析

强化科技基础推进气象现代化——第29届中国气象学会年会

作者： Suqin Han 1,Hai Bian 1,Yufen Zhang 2,Jianhui Wu 2,Yimei Wang 2,Xuexi Tie 3.Yinghua Li 1 Xiangjin Li 1 Qing Yao 1 1 Tianjin Institute of meteorological science,Tianjin,3.0074 2 Nankai university,Tianjin,3.0071.3.National center for Atmospheric Research,boulder,co{3.

Meteorological and aerosol data were measured at the atmospheric boundary layer observation station in Tianjin,China,and were analyzed to study the effects of aerosol mass,composition,and size distributions on visibility and short-term radiation *** results show that fine particles played important roles in controlling visibility in *** major contributors to light extinction coefficients included sulfate(28.7%),particulate organic matter(27.6%),elemental carbon(19.2%),and nitrate(6.1%).In addition to the measurement of aerosol composition,the size distribution of aerosol number concentrations were also measured and classified between haze days and non-haze days during *** extinction characteristics of ambient aerosol in haze days and non-haze days were calculated using Mie theory *** average extinction coefficient and scattering coefficient of atmospheric aerosols were 0.253.km-1 and 0.213.km-1 in non-haze days,while 0.767 km-1 and 0.665 km-1 in haze days.A radiation transmission model LOWTRAN7 is also applied in this *** model calculated radiant flux densities in haze days and non-haze days,which showed a fairly agreement with the observation results,showing that the heavy aerosol loadings in Tianjin had significantly impact on atmospheric visibility and radiation fluxes.

关键词： aerosol visibility extinction coefficient refractive index radiation fluxes

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电源世界 2001年第6期 33-38,32页

作者： Dragan Maksimovic Power Electronics Group Department of Electrical and computer Engineering university of colorado BoulderCO 80309-0425

The paper describes a method for automated small-signal frequency response analysis based on transient responseobtained using a generalpurpose simulation tool such as *** method is based on using the simulation toolto evaluate the converter impulse *** main advantage of the proposed method as a design verification tool isthat frequency responses can be generated efficiently for any converter configuration and any model complexity supportedby the general-purpose simulator, Application examples are included to demonstrate very good correlation betweenthe generated responses and experimental data, and to compare the results with predictions of approximate analyticalmethods.

关键词：仿真器自动分析仿真方法小信号时域开关模型变换采用世界