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EN
A contactless laser hygrometer based on light absorption by H2O molecules at 1392.5 nm is described. However, measurement results can be affected by optical noise when applied to an atmospheric tunnel or glass cuvette. The noises (occurring in the form of periodic fringes in the recorded spectrum) come from unexpected interference of the light beams reflected from surfaces of the windows or other optical elements. The method of their suppression is described in this article. It is based on wavelength modulation and signal averaging over the fringes period. Also, an experiment confirming the usefulness of this method is described here.
EN
We describe construction and investigation results of optical trace gas sensor working in the 3.334-3.337 μm spectral range. Laser spectroscopy was performed with a multipass cell. A setup was elaborated for detection of ethane at the 3.3368035 μm absorption line. Analysis of the gas spectra and the experiment have shown that, beside C2H6, the sensor is suitable for simultaneous detection of methane, formaldehyde and water vapor. Due to nonlinearity of the laser power characteristic we decided to detect the fourth harmonic of signal. Additional laser wavelength modulation was applied for optical interference suppression. In result, the precision of ethane detection of approximately 80 ppt has been achieved for the averaging time of 20 seconds. Long-term stability as well as the measurement linearity have also been positively tested. The system is suitable for detecting potential biomarkers directly in human breath.
EN
Investigation results of a coarse and accumulation mode of aerosol properties above the Baltic Sea are reported. A most important role in the direct aerosol effect on climate have aerosols from the group of coarse and accumulation mode particles. Overseas in the atmosphere, there is a lot of aerosols from the fine fraction but their impact is not so important as coarse and accumulation mode particles. Sea spray emission from the sea surface takes place over a wide range of aerosol particle size distribution, it is also large in size range which are studying in this work (Lewis and Schwartz, 2004). The discussed range is most important in view of atmospheric optical properties, smaller particles do not have such an influence on scattering as particles from range 0.5–2 µm. The research was performed with a multiwavelength lidar. Due to the application of special software, the aerosol particle size distributions were retrieved from the lidar returns. That provided an opportunity to determine the profiles of the aerosol effective radius. We showed that the aerosol properties depend mainly on the direction of the air mass advection and the wind speed. The impact of the Baltic Sea on the aerosol size distribution is huge in the case of the advection from the open sea. Moreover, the aerosol effective radiuses in the whole boundary layer are much larger in the case of strong than for light wind. Our results suggest that the aerosol flux and the aerosol particle size distribution should be related to the wind speed in the emission function.
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