Simple indices of global climate variability and change: Part I – variability and correlation structure     

K. Braganza  D. Karoly  A. Hirst  M. Mann  P. Stott  R. Stouffer  S. Tett 《Climate Dynamics》2003,20(5):491-502

  相似文献   

Synoptic and mesoscale study of a severe convective outbreak with the nonhydrostatic Global Environmental Multiscale (GEM) model   总被引：1，自引：0，他引：1  

A. Erfani  A. Méthot  R. Goodson  S. Bélair  K.-S. Yeh  J. Côté  R. Moffet 《Meteorology and Atmospheric Physics》2003,82(1-4):31-53

Summary ?A nonhydrostatic 4-km version of the Global Environmental Multiscale (GEM) model, with detailed microphysics included, was used to forecast the initiation, development, and structure of a tornado-producing supercell storm that occurred near Pine Lake (Alberta, Canada) on 15 July 2000. Examination of observations and comparison with conceptual models indicate that this storm is a good example of supercell storms that regularly produce summertime severe weather over Alberta. It was found that the high-resolution model was able to reproduce the early initiation of convective activity along the Rocky Mountains foothills, as well as the rapid northeastward propagation towards the Pine Lake area and the subsequent intensification into a supercell storm. The general structures of the forecasted convective system correspond well with conceptual representations of such events. Overall, this high-resolution forecast of the Pine Lake supercell storm was a significant improvement over the current operational version of the GEM model (24 km), which was not able to intensify the foothills’ convection into a supercell storm. Finally, it was found that the nonhydrostatic version of the model produces better trajectory and propagation speed of the convective system, as compared with the hydrostatic one. Received March 20, 2001; revised August 24, 2001  相似文献   

Intercomparison of Stratospheric Chemistry Models under Polar Vortex Conditions     

M. Krämer  Ri. Müller  H. Bovensmann  J. Burrows  J. Brinkmann  E. P. Röth  J.-U. Grooß  Ro. Müller  Th. Woyke  R. Ruhnke  G. Günther  J. Hendricks  E. Lippert  K. S. Carslaw  Th. Peter  A. Zieger  Ch. Brühl  B. Steil  R. Lehmann  D. S. McKenna 《Journal of Atmospheric Chemistry》2003,45(1):51-77

Several stratospheric chemistry modules from box, 2-D or 3-D models, have been intercompared. The intercomparison was focused on the ozone loss and associated reactive species under the conditions found in the cold, wintertime Arctic and Antarctic vortices. Comparisons of both gas phase and heterogeneous chemistry modules show excellent agreement between the models under constrained conditions for photolysis and the microphysics of polar stratospheric clouds. While the mean integral ozone loss ranges from 4–80% for different 30–50 days long air parcel trajectories, the mean scatter of model results around these values is only about ±1.5%. In a case study, where the models employed their standard photolysis and microphysical schemes, the variation around the mean percentage ozone loss increases to about ±7%. This increased scatter of model results is mainly due to the different treatment of the PSC microphysics and heterogeneous chemistry in the models, whereby the most unrealistic assumptions about PSC processes consequently lead to the least representative ozone chemistry. Furthermore, for this case study the model results for the ozone mixing ratios at different altitudes were compared with a measured ozone profile to investigate the extent to which models reproduce the stratospheric ozone losses. It was found that mainly in the height range of strong ozone depletion all models underestimate the ozone loss by about a factor of two. This finding corroborates earlier studies and implies a general deficiency in our understanding of the stratospheric ozone loss chemistry rather than a specific problem related to a particular model simulation.  相似文献   

Modelling of the OASIS Energy Flux Measurements Using Two Canopy Concepts     

K. Finkele  J.J. Katzfey  E.A. Kowalczyk  J.L. McGregor  L. Zhang  M.R. Raupach 《Boundary-Layer Meteorology》2003,107(1):49-79

Two land surface schemes, SCAM and CSIRO9, were used to model the measured energy fluxes during the OASIS (Observations At Several Interacting Scales) field program. The measurements were taken at six sites along a 100 km rainfall gradient. Two types of simulations were conducted: (1) offline simulations forced with measured atmospheric input data at each of the six sites, and (2) regional simulations with the two land surface schemes coupled to the regional climate model DARLAM.The two land surface schemes employ two different canopy modelling concepts: in SCAM the vegetation is conceptually above the ground surface, while CSIRO9 employs the more commonly used `horizontally tiled' approach in which the vegetation cover is modelled by conceptually placing it beside bare ground. Both schemes utilize the same below-ground components (soil hydrological and thermal models) to reduce the comparison to canopy processes only. However, the ground heat flux, soil evaporation and evapotranspiration are parameterised by the two canopy treatments somewhat differently.Both canopy concepts reproduce the measured energy fluxes. SCAM has a slightly higher root-mean standard error in the model-measurement comparison for the ground heat flux. The mean surface radiative temperature simulated by SCAM is approximately 1K lower than in the CSIRO9 simulations. However, the soil and vegetation temperatures (which contribute to the radiative temperature) varied more in the CSIRO9 simulations. These larger variations are due to the absence of a representation of the aerodynamic interactions between vegetation and ground.  相似文献   

Description and evaluation of the bergen climate model: ARPEGE coupled with MICOM   总被引：2，自引：4，他引：2  

T. Furevik  M. Bentsen  H. Drange  I. K. T. Kindem  N. G. Kvamstø  A. Sorteberg 《Climate Dynamics》2003,21(1):27-51

A new coupled atmosphere–ocean–sea ice model has been developed, named the Bergen Climate Model (BCM). It consists of the atmospheric model ARPEGE/IFS, together with a global version of the ocean model MICOM including a dynamic–thermodynamic sea ice model. The coupling between the two models uses the OASIS software package. The new model concept is described, and results from a 300-year control integration is evaluated against observational data. In BCM, both the atmosphere and the ocean components use grids which can be irregular and have non-matching coastlines. Much effort has been put into the development of optimal interpolation schemes between the models, in particular the non-trivial problem of flux conservation in the coastal areas. A flux adjustment technique has been applied to the heat and fresh-water fluxes. There is, however, a weak drift in global mean sea-surface temperature (SST) and sea-surface salinity (SSS) of respectively 0.1 °C and 0.02 psu per century. The model gives a realistic simulation of the radiation balance at the top-of-the-atmosphere, and the net surface fluxes of longwave, shortwave, and turbulent heat fluxes are within observed values. Both global and total zonal means of cloud cover and precipitation are fairly close to observations, and errors are mainly related to the strength and positioning of the Hadley cell. The mean sea-level pressure (SLP) is well simulated, and both the mean state and the interannual standard deviation show realistic features. The SST field is several degrees too cold in the equatorial upwelling area in the Pacific, and about 1 °C too warm along the eastern margins of the oceans, and in the polar regions. The deviation from Levitus salinity is typically 0.1 psu – 0.4 psu, with a tendency for positive anomalies in the Northern Hemisphere, and negative in the Southern Hemisphere. The sea-ice distribution is realistic, but with too thin ice in the Arctic Ocean and too small ice coverage in the Southern Ocean. These model deficiencies have a strong influence on the surface air temperatures in these regions. Horizontal oceanic mass transports are in the lower range of those observed. The strength of the meridional overturning in the Atlantic is 18 Sv. An analysis of the large-scale variability in the model climate reveals realistic El Niño – Southern Oscillation (ENSO) and North Atlantic–Arctic Oscillation (NAO/AO) characteristics in the SLP and surface temperatures, including spatial patterns, frequencies, and strength. While the NAO/AO spectrum is white in SLP and red in temperature, the ENSO spectrum shows an energy maximum near 3 years.  相似文献   

Competition of NAO regime changes and increasing greenhouse gases and aerosols with respect to Arctic climate projections     

W. Dorn  K. Dethloff  A. Rinke  E. Roeckner 《Climate Dynamics》2003,21(5-6):447-458

Regional magnitudes and patterns of Arctic winter climate changes in consequence of regime changes of the North Atlantic Oscillation (NAO) are analyzed using a regional atmospheric climate model. The regional model has been driven with data of positive and negative NAO phases from a control simulation as well as from a time-dependent greenhouse gas and aerosol scenario simulation. Both global model simulations include a quite realistic interannual variability of the NAO with pronounced decadal regime changes and no or rather weak long-term NAO trends. The results indicate that the effects of NAO regime changes on Arctic winter temperatures and precipitation are regionally significant over most of northwestern Eurasia and parts of Greenland. In this regard, mean winter temperature variations of up to 6 K may occur over northern Europe. Precipitation and synoptic variability are also regionally modified by NAO regime changes, but not as significantly as temperatures. However, the climate changes associated with the NAO are in some regions clearly stronger than those attributed to enhanced greenhouse gases and aerosols, indicating that projected global changes of the atmospheric composition and internal circulation changes are competing with each other in their importance for the Arctic climate evolution in the near future. The knowledge of the future NAO trend on decadal and longer time scales appears to be vitally important in terms of a regional assessment of climate scenarios for the Arctic.  相似文献   

Contens of Volume 59     

Henry F. Diaz  Jon K. Eischeid  Chris Duncan  Raymond S. Bradley 《Climatic change》2003,59(3):417-418

  相似文献   

Internet teaching foundation for the Remote Sensing Core Curriculum program     

T.W. Foresman  T. Cary  T. Shupin  R. Eastman  J.E. Estes  N. Faust  J.R. Jensen  K.K. Kemp 《ISPRS Journal of Photogrammetry and Remote Sensing》1997,52(6):294-300

The Remote Sensing Core Curriculum (RSCC) was initiated in 1993 to meet the demands for a college-level set of resources to enhance the quality of education across national and international campuses. The American Society of Photogrammetry and Remote Sensing adopted the RSCC in 1996 to sustain support of this educational initiative for its membership and collegiate community. A series of volumes, containing lectures, exercises, and data, is being created by expert contributors to address the different technical fields of remote sensing. The RSCC program is designed to operate on the Internet taking full advantage of the World Wide Web (WWW) technology for distance learning. The issues of curriculum development related to the educational setting, with demands on faculty, students, and facilities, is considered to understand the new paradigms for WW-influenced computer-aided learning. The WWW is shown to be especially appropriate for facilitating remote sensing education with requirements for addressing image data sets and multimedia learning tools. The RSCC is located at http://www.umbc.edu/rscc  相似文献   

Remote sensing of horticultural plantations in Kumarsain tehsil in Shimla district, Himachal Pradesh     

M M Kimothi  M H Kalubarme  Sujay Dutta  Rajendra Thapa  R K Sood 《Journal of the Indian Society of Remote Sensing》1997,25(1):19-26

The favourable agroclimatic conditions for orchards especially apples have increased the acreages in Himachal Pradesh (HP) which has significantly contributed in the growth of state economy. Realizing the importance of horticulture in HP and its changing scenario of the land use/land cover, a study was conducted to identify and map apple and almond plantations in the Kumarsain tehsil of Shimla district using Remote Sensing (RS) techniques. IRS-IB LISS-II False Colour Composite (FCC) diapositives of October 27, March 30 and April 20, 1992 were visually analysed for mapping apple and almond plantations. The results indicate that IRS LISS-II data of April 20 on 1∶50,000 scale was found very useful for identification and mapping of apple and almond plantations in this region. Accuracy of interpretation was also tested on sample basis assuming a binomial distribution for the probability of success/failure of sample points. The overall interpretation accuracy assessed based on 40 sample points was found to be 87 per cent at 90 per cent confidence limits.  相似文献   

Site suitability evaluation for locating sewage treatment plants using remote sensing and gis — a case study of phillaur and phagwara townships in punjab     

P K Litoria  Ajay Mathur  P K Sharma  Charan kamal Singh 《Journal of the Indian Society of Remote Sensing》1997,25(4):261-272

Level-II urban land use information available in this Town and Country Planning maps, Survey of India toposteets for Phillaur and Phagwara towns and the land use information generated through visual interpretation of satellite data was digitized, integrated and analysed using PAMAP GIS. The land use map of the two towns suggest that the wastelands located near the point of present disposal can be utilised for siting sewage treatment plants in both the towns. The STP sites suggested were away from the thickly habttared area. It was observed that some of the areas earmarked for locating STP’s, were partially brought under habitation before the execution of the preject. Hence, it is necessary that planning and execution of such projects should be done on a real time basis so that the sites identified for locating STP’s are not brought under other land uses.  相似文献