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Randolph D. Borys 《Journal of Atmospheric Chemistry》1989,9(1-3):169-185
Aerosol particles were collected on filters for studies of their ability to nucleate ice during the second Arctic Gas and Aerosol Sampling Program (AGASP-II) in April, 1986. The ice nuclei (IN) samples were collected from an aircraft at altitudes ranging from the surface to the vicinity of the tropopause in Arctic locations over Alaska, northern Canada and Greenland. Samples of other components of the aerosol were collected and measurements were made of other properties of the aerosol coincident in time with the IN samples. The IN filters were exposed to water saturation in a dynamic developing chamber at –15° C and –25° C. Ice crystals grew on the IN and were counted on the filters at discrete time intervals during the exposure period to determine the rate of ice nucleation and the final concentration of (IN). Results show that Arctic haze aerosol, identified by pollutant signatures, had lower IN concentrations, a lower IN to total aerosol fraction and slower ice nucleation rates than aerosol which had a chemical signature more indicative of the remote unpolluted troposphere. These observations suggest that the Arctic haze aerosol does not efficiently form ice in the arctic troposphere. This may be a factor contributing to the long-range transport of Arctic haze. 相似文献
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Norbert I. Kömle Hui Bing Wen Jie Feng Roman Wawrzaszek Erika S. Hütter Ping He Wojciech Marczewski Borys Dabrowski Kathrin Schröer Tilman Spohn 《Acta Geotechnica》2007,2(2):127-138
A series of thermal conductivity measurements for various materials was performed in a large climate chamber. The size of
the chamber allowed the preparation of relatively large samples in a controlled thermal environment. Three types of thermal
sensors were used: (1) two needle probes; (2) a grid of temperature sensors, evenly distributed inside the sample; (3) two
additional thermal probes, which were simplified versions of an instrument originally developed for measuring thermal properties
of the ice/dust mixture expected to exist at the surface of a comet nucleus. They consist of a series of individual temperature
sensors integrated into a glass fibre rod. Each of these sensors can be operated in an active (heated) or passive (only temperature
sensing) mode. The following sample materials were used: fine-grained reddish sand, coarse-grained moist sand, gravels with
various grain size distributions from < 1 cm up to about 6 cm, and for comparison and calibration pure water (with convection
suppressed by adding agar-agar), compact ice, and compact granite. Of particular interest are the measurements with composite
samples, like stones embedded in an agar-agar matrix. We describe the evaluation methods and present the results of the thermal
conductivity measurements. 相似文献
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Ronan Higgins David Teyssier Colin Borys Jonathan Braine Claudia Comito Bertrand Delforge Frank Helmich Michael Olberg Volker Ossenkopf John Pearson Russell Shipman 《Experimental Astronomy》2014,37(2):433-452
The Heterodyne Instrument for the Far Infrared (HIFI) on board the Herschel Space Observatory is composed of a set of fourteen double sideband mixers. We discuss the general problem of the sideband ratio (SBR) determination and the impact of an imbalanced sideband ratio on the line calibration in double sideband heterodyne receivers. The HIFI SBR is determined from a combination of data taken during pre-launch gas cell tests and in-flight. The results and some of the calibration artefacts discovered in the gas cell test data are presented here along with some examples of how these effects appear in science data taken in orbit. 相似文献
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Studia Geophysica et Geodaetica - Magnetovariation methods, which are applicable to study the mantle conductivity, require long lasting registration of natural magnetic field variations. Such data... 相似文献
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The hourly data of nine geomagnetic observatories situated in Central Europe have been analyzed using the generalized magnetovariation
(GMV) method designed recently for induction soundings of inhomogeneous media. In this method, impedance is one of transfer
functions in the differential relation between spectra of the magnetic components and their derivatives. The peculiarity of
this impedance is its correspondence to the magnetotelluric one estimated from the linear relations. Three transfer functions
have been estimated simultaneously for data of geomagnetic observatories, using three different routines working in the period
range from three hours up to two days. Noises in the source field components have been compared with noise in the estimated
plane field divergence. The multivariate errors-in-variables method was used to extract spatially and temporally coherent
geomagnetic field structure from the partially incoherent geomagnetic variations. This method allows estimating reliably impedances
and gradient tippers for each observatory, taking into consideration the Earth’s sphericity. The obtained responses have been
used for induction soundings and for detecting a deep inhomogeneity in the region. 相似文献
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Summary A network of ground-based Global Positioning System (GPS) receivers is used to continuously obtain information on variations
in the integrated water vapor (IWV) in the atmosphere. We use GPS data from 1996–1998 to compare the IWV estimates with radiosonde
data. The spatial correlation of estimation errors is important when the GPS results are to be used in assimilation models.
We study and model this effect by comparing the horizontal correlations of the IWV time series derived from the radiosonde
network and the GPS data analysis. Under ideal conditions this method separates the IWV features from the underlying correlation
function for the estimation errors in the GPS data. A sparse radiosonde network limits the quality of the obtained results.
We foresee continued studies including more data and simulations of the errors associated with the GPS technique.
Received November 21, 2000 Revised April 2, 2001 相似文献
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