Midlatitude F-region neutral winds and temperatures during the priority regular world day 14 August 1980     

Dwight P. Sipler  Manfred A. Biondi  R. G. Roble 《Planetary and Space Science》1981,29(12):1367-1372

Midlatitude F-region neutral winds and temperatures determined from Fabry-Perot interferometer measurements of the doppler shifts and widths of nightglow 630.0 nm line profiles are presented for the priority regular world day 14 August 1980. They exhibit, in many respects, the observed behavior for other summer, geomagnetically quiet nights at solar maximum. The neutral temperature decreases from 1500°K after sunset (21 h LT) to a minimum of ˜ 1200°K before dawn (05 h LT), except to the north of the observatory. The zonal winds are eastward at sunset at 50 m/sec, decrease to zero at 02 h LT and are westward just before dawn. The meridional winds are zero just after sunset and reach a maximum equatorward value of 50–70 m/sec at local midnight but do not decrease as predicted; instead, they remain at roughly these values towards dawn. The NCAR thermospheric general circulation model (TGCM) is used to predict the global upper atmospheric temperature and circulation patterns for this world day. The model predictions agree with the measured neutral temperatures and exhibit qualitative similarities to the measured neutral winds. It is concluded that inclusion in the model of ion drift at midlatitudes should improve the agreement with observations.  相似文献   

Tracer dispersal by mid-ocean mesoscale eddies. Part I. Ensemble statistics     

Dale B. Haidvogel  Thomas Keffer 《Dynamics of Atmospheres and Oceans》1984,8(1):1-40

The rate at which, and the processes by which, a passive tracer is stirred and mixed in a turbulent mesoscale eddy field are examined for environmental parameters characteristic of a homogeneous mid-ocean region. The simulated, time-dependent eddy field is obtained by direct integration of the forced/damped barotropic vorticity equation; the dispersal of a spatially localized, instantaneous release of tracer (a “tracer spot”) within the evolving velocity field is subsequently computed from the advective-diffusive equation. An ensemble of 10 independent releases is used to determin the average spreading properties of the tracer spot.On an f-plane, the ensemble-averaged dispersal is approximately isotropic, and is associated with an effective diffusion rate substantially greater than that supported in the absence of turbulent advection. Quantitatively, the effective ensemble-averaged diffusivity is shown to be 0(UL), where U and L are characteristic velocity and length scales of the turbulent flow. This estimate is consistent with the traditional mixing length hypothesis. With the addition of β, the simulated flow field has substantial zonal anisotropy. Ensemble-averaged dispersal of tracer spots is similarly anisotropic, and the overall rate of tracer dispersal is substantially reduced over its f-plane value.Both with and without β, the initial rate at which maximum tracer concentration and total tracer variance decay are given by the approximate law exp[? αγt] where γ is the RMS rate of strain, and α is approximately constant at a value of 0.5. The heightened rate of variance loss over that associated with pure (subgridscale) diffusion is shown to be accommodated by the rapid transfer of tracer variance from the largest to the shortest scale tracer features, that is, by the rapid sharpening of tracer gradients by turbulent advection. A detailed examination of the dispersal of individual tracer realizations, and the associated question of tracer streakiness, is given in part II of this work (Keffer and Haidvogel, in preparation).  相似文献   

‘The CO2 problem: Are there policy implications — Yet?’ An editorial     

Stephen H. Schneider 《Climatic change》1980,2(3):203-205

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Heating of coronal loops by fast mode MHD waves     

Shadia Rifai Habbal  Egil Leer  Thomas E. Holzer 《Solar physics》1979,64(2):287-301

A possible mechanism for the formation and heating of coronal loops through the propagation and damping of fast mode waves is proposed and studied in detail. Loop-like field structures are represented by a dipole field with the point dipole at a given distance below the solar surface. The density of the medium is determined by hydrostatic equilibrium along the field lines in an isothermal atmosphere. The fast mode waves propagating outward from the coronal base are refracted into regions with a low Alfvén speed and suffer collisionless damping when the gas pressure becomes comparable to the magnetic pressure. The propagation and damping of these waves are studied for three different cases: a uniform density at the coronal base, a density depletion within a given flux tube, and a density enhancement within a given flux tube. The fast mode waves are found to be important in the formation and heating of the loops if the wave energy flux density is of the order 10⁵ ergs cm^-2 s^-1 at the coronal base.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

Dynamo currents representing geomagnetic L variation demonstrated by a multi-layer ionospheric model     

S. Matsushita 《Planetary and Space Science》1984,32(5):629-633

A multi-layer ionospheric model and lunar (2,2) tidal mode have been used to calculate dynamo current systems representing lunar geomagnetic semidiurnal variations. Since both the height variation of the ionospheric conductivities and latitudinal dependence of the height of the conductivity peaks have been taken into account, the dynamo current systems agree with equivalent ones (estimated from geomagnetic data) better than those for a thin shell model of the ionospheric conductivity, especially in the polar region.  相似文献   

Correlations of the evolution of a CCOPE squall line with surface thermodynamics and kinematic fields     

Xu Yumao  J. C. Fankhauser 《大气科学进展》1989,6(1):99-112

A midlatitude squall line passed over the array of the Cooperative Convective Precipitation Experiment (CCOPE) on 1 August 1981. The structure and evolution of the squall line, and the correlations of the storm with surface thermodynamics and kinematic fields are investigated, mainly by using radar and surface mesonet data in CCOPE. The storm-wide precipitation efficiency is also estimated. The squall line was of an obvious process of metabolism. Thirty-four cells formed successively in front of the primary storm and eventually merged into it during the period 1700-2010 MDT. The newest cells formed near surface equivalent potential temperature maxima, and near surface moisture flux convergence zones or/ and the “temperature break lines”. The thunderstorm rainfall, with the precipitation efficiency of 54%, lags 25-30 min behind the moisture flux convergence on the average.  相似文献   

针对对流降水预报的BJ-RUC系统1小时更新循环方案研究   总被引：1，自引：3，他引：1  

童文雪  李刚  孙娟珍 《热带气象学报》2018,34(2):177-187

为了提高快速更新循环系统的分析和预报水平,在BJ-RUC系统中,发展了针对1小时更新循环的分步同化方案。分步同化的方案有效解决了在现有变分同化系统中如何在分析场中加入更多的对流尺度观测信息,同时保持大尺度背景场平衡的问题。该方案是将大尺度的常规观测和小尺度、高分辨率的观测资料分步同化,从不同尺度的观测中分别提取出大尺度和对流尺度的信息。以2009年北京地区夏季的4次强降水过程为个例进行同化和预报试验。结果表明,该方案在12小时的预报时效内能有效提高降水预报。对飑线个例的详细分析结果显示,分步同化方案可以使分析场中同时保留大尺度和对流尺度的信息,从而使预报的降水位置和强度等方面都更准确,降水预报评分有明显提高。   相似文献   

Evolution of the Fine Structure of Magnetic Fields in the Quiet Sun: Observations from Sunrise/IMaX and Extrapolations     

T. Wiegelmann  S. K. Solanki  J. M. Borrero  H. Peter  P. Barthol  A. Gandorfer  V. Martínez Pillet  W. Schmidt  M. Knölker 《Solar physics》2013,283(2):253-272

Observations with the balloon-borne Sunrise/Imaging Magnetograph eXperiment (IMaX) provide high spatial resolution (roughly 100 km at disk center) measurements of the magnetic field in the photosphere of the quiet Sun. To investigate the magnetic structure of the chromosphere and corona, we extrapolate these photospheric measurements into the upper solar atmosphere and analyze a 22-minute long time series with a cadence of 33 seconds. Using the extrapolated magnetic-field lines as tracer, we investigate temporal evolution of the magnetic connectivity in the quiet Sun’s atmosphere. The majority of magnetic loops are asymmetric in the sense that the photospheric field strength at the loop foot points is very different. We find that the magnetic connectivity of the loops changes rapidly with a typical connection recycling time of about 3±1 minutes in the upper solar atmosphere and 12±4 minutes in the photosphere. This is considerably shorter than previously found. Nonetheless, our estimate of the energy released by the associated magnetic-reconnection processes is not likely to be the sole source for heating the chromosphere and corona in the quiet Sun.  相似文献   

Intercomparison of the LASCO-C2, SECCHI-COR1, SECCHI-COR2, and Mk4 Coronagraphs     

Richard A. Frazin  Alberto M. Vásquez  William T. Thompson  Russell J. Hewett  Philippe Lamy  Antoine Llebaria  Angelos Vourlidas  Joan Burkepile 《Solar physics》2012,280(1):273-293

In order to assess the reliability and consistency of white-light coronagraph measurements, we report on quantitative comparisons between polarized brightness [pB] and total brightness [B] images taken by the following white-light coronagraphs: LASCO-C2 on SOHO, SECCHI-COR1 and -COR2 on STEREO, and the ground-based MLSO-Mk4. The data for this comparison were taken on 16?April 2007, when both STEREO spacecraft were within 3.1^° of Earth??s heliographic longitude, affording essentially the same view of the Sun for all of the instruments. Due to the difficulties of estimating stray-light backgrounds in COR1 and COR2, only Mk4 and C2 produce reliable coronal-hole values (but not at overlapping heights), and these cannot be validated without rocket flights or ground-based eclipse measurements. Generally, the agreement between all of the instruments?? pB values is within the uncertainties in bright streamer structures, implying that measurements of bright CMEs also should be trustworthy. Dominant sources of uncertainty and stray light are discussed, as is the design of future coronagraphs from the perspective of the experiences with these instruments.  相似文献   

Developing service-oriented applications in a grid environment     

Jose Garcia  Peter Fox  Patrick West  Stephan Zednik 《Earth Science Informatics》2009,2(1-2):133-139

The Open-source Project for a Network Data Access Protocol (OPeNDAP) software framework has evolved over the last 10 years to become a robust, high performance, service oriented architecture for the access and transport of scientific data from a broad variety of disciplines, over the Internet. Starting with version 4.0 of the server release, Hyrax, has at its core, the Back-End Server (BES). The BES offers ease of programming, extensibility and reliability allowing added functionality especially related to high-performance data Grids, that goes beyond its original goal of distributed data access. We present the fundamentals of the BES server as a component based architecture, as well as our experiences using the BES to distribute data processing in Grid-oriented intensive parallel computational tasks.  相似文献