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排序方式: 共有163条查询结果,搜索用时 15 毫秒
1.
The Infrared Astronomical Satellite (IRAS) program will produce an extremely sensitive all-sky survey over the wavelength region 8 to 120 μm when the mission is flown in 1982. These data will provide a novel opportunity to detect planetary-sized objects having masses <0.08M⊙ or near our solar system. The improved detection limit of the IRAS will greatly increase the volume of space searched for such objects as compared with previous optical and infrared studies. 相似文献
2.
Parasitic programs for the Search for Extraterrestrial Intelligence (SETI), carried out concurrently with conventional radio astronomical observing programs, can be an attractive and cost-effective means of exploring the large multidimensional search space intrinsic to this effort. We describe a microprocessor-based automated SETI acquisition system which searches for and records spectra of narrowband signals in the IF band of an observatory receiver. Data taken with this system over 35 days at the Hat Creek Radio Observatory at 1612 MHz are discussed. Out of approximately 105 spectra processed during this period, 4000 were identified by the system as containing narrowband signals and were recorded. Subsequent analysis indicates that over 3900 of these are due to local RF contamination. The remainder are undergoing further investigation. 相似文献
3.
Warren J. de Bruyn Mike Harvey Jill M. Cainey Eric S. Saltzman 《Journal of Atmospheric Chemistry》2002,41(2):189-209
Atmospheric dimethyl sulfide (DMS) and sulfur dioxide (SO2) concentrations were measured at Baring Head, New Zealandduring February and March 2000. Anti-correlated DMS and SO2 diurnalcycles, consistent with the photochemical production of SO2 from DMS, were observed in clean southerly air off the ocean. The data is used to infer a yield of SO2 from DMS oxidation. The estimated yields are highly dependent on assumptions about the DMS oxidation rate. Fitting the measured data in a photochemical box model using model-generated OH levels and the Hynes et al. (1986) DMS + OH rate constant suggests that theSO2 yield is 50–100%, similar to current estimates for the tropical Pacific.However, the observed amplitude of the DMS diurnal cycle suggests that the oxidation rate is higher than that used by the model, and therefore, that theSO2 yield is lower in the range of 20–40%. 相似文献
4.
Edouard L. Davin Reto St?ckli Eric B. Jaeger Samuel Levis Sonia I. Seneviratne 《Climate Dynamics》2011,37(9-10):1889-1907
This study presents an evaluation of a new biosphere-atmosphere Regional Climate Model. COSMO-CLM2 results from the coupling between the non-hydrostatic atmospheric model COSMO-CLM version 4.0 and the Community Land Model version 3.5 (CLM3.5). In this coupling, CLM3.5 replaces a simpler land surface parameterization (TERRA_ML) used in the standard COSMO-CLM. Compared to TERRA_ML, CLM3.5 comprises a more complete representation of land surface processes including hydrology, biogeophysics, biogeochemistry and vegetation dynamics. Historical climate simulations over Europe with COSMO-CLM and with the new COSMO-CLM2 are evaluated against various data products. The simulated climate is found to be substantially affected by the coupling with CLM3.5, particularly in summer. Radiation fluxes as well as turbulent fluxes at the surface are found to be more realistically represented in COSMO-CLM2. This subsequently leads to improvements of several aspects of the simulated climate (cloud cover, surface temperature and precipitation). We show that a better partitioning of turbulent fluxes is the central factor allowing for the better performances of COSMO-CLM2 over COSMO-CLM. Despite these improvements, some model deficiencies still remain, most notably a substantial underestimation of surface net shortwave radiation. Overall, these results highlight the importance of land surface processes in shaping the European climate and the benefit of using an advanced land surface model for regional climate simulations. 相似文献
5.
Summary ?The long-term variations of upward terrestrial (E) and downward atmospheric (A) long-wave radiation fluxes above a pine stand
in the southern part of the upper Rhine valley plain are analysed based on monthly mean values from 27 years of monitoring.
Equivalent blackbody temperatures of the canopy and the atmosphere are calculated and compared to air temperatures at nearby
sites.
Based on 324 monthly values each, correlations between A and E as well as A and global radiation G are analysed. Only the
former are highly correlated. Monthly mean values of long-wave radiation A can be calculated from air temperature, water vapour
pressure and cloud cover.
The long-term yearly average of equivalent blackbody temperature of the canopy is 0.6 K lower than kinetic air temperature
at nearby sites.
Only small, insignificant increases of both blackbody temperatures and air temperature are found. Despite the strong forest
growth, it is surprising that the ratio of canopy emission temperature to air temperature did not change significantly.
Relationships between the changes of general atmospheric circulation and equivalent blackbody temperatures of the canopy point
to a strong dependence on shifts of general atmospheric flow.
Received February 24, 2000; revised April 18, 2002; accepted July 20, 2002 相似文献
6.
7.
The study of human dimensions of global climatic change is still in the initial stage of development. Several attempts have been undertaken to define sensible research strategies in the field but until now relatively little empirical work has been undertaken and there is a lack of sound theoretical arguments. The present paper presents a theory-based empirical study of determinants influencing the probability that somebody takes climate-relevant environmental action. Important methodological differences between current models of climate dynamics and models of human reality are discussed in order to build three models of climate-related environmental action. A model focussed on the information transfer from science to the public at large is compared with a model focussed on sociodemographic characteristics and with a model focussed on socio-cultural variables like interpersonal rules and social networks. The hypothesis that the latter model is strongly superior to the former ones is tested and confirmed. Some implications for interdisciplinary cooperation and for policy making are discussed. 相似文献
8.
Summary
Lees's topographic correction for a simple idealized hill is discussed and extended to a monoclinal structure. It is valuable as giving very simply the order of magnitude of the correction. A number of new measurements of temperature in Tasmanian boreholes has been made and the previous rather high value of over 2 cal/cm2 sec for the heat flux has been confirmed. The variation of thermal conductivity through the thickness of a differentiated tholeiite sheet has been measured and found to be in reasonably good agreement with values calculated from chemical and modal analyses. 相似文献
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