1,721,119 research outputs found
Remote sensing of atmospheric aerosols from active and passive optical techniques
No full textSignificant contributions to studies in aerosol science have come from optical remote sensing techniques and, for several reasons, these studies have special importance over the tropics where convective and high-altitude convective (as well as dynamical) processes affect the distribution of aerosols. Atmospheric aerosol studies employing active remote sensing techniques such as light detection and ranging (lidar) have been in progress for the past decade at the Indian Institute of Tropical Meteorology (IITM), Pune (18 32' N, 73 51' E, 559 m above mean sea level), India. Simultaneous measurements of aerosol optical and physical properties using passive remote sensing techniques such as spectroradiometry have also been in practice at the IITM since 1992. The experimental techniques developed and the results of the studies that have been carried out at the IITM are reviewed in this paper. These observations have enabled the study of aerosol climatology over Pune and have led to a better description of the atmospheric aerosol structure and stratification in the nocturnal atmospheric boundary layer, the air quality, and their association with the experimental terrain and meteorological conditions of the observing station. Such tropospheric aerosol climatologies are sparse over the tropics and almost nonexistent in India. The stratospheric physical and dynamical aerosol aspects of recent major volcanic eruptions, studied from ground-based lidar and satellite observations, are also discusse
Study of physico-chemical and optical properties of atmospheric constituents under different environmental and meteorological conditions in India - Part II: Trace gases
No full textIn the previous paper, several experimental techniques developed and the results of extensive, multistation observations of atmospheric aerosols have been presented. The present paper deals with the study of trace gas constituents and their role in the chemistry of the troposphere and stratosphere where the interactions between atmospheric gases, aerosols and cloud droplets are known to be very strong. The direct as well as remote sensing experimental techniques and modelling methods that have been developed at the Indian Institute of Tropical Meteorology (IITM), Pune, and employed for determining the trace gas concentrations over different stations associated with a variety of meteorological conditions, are discussed. Also included in the paper are the results of the studies related to precipitation chemistry. The main conclusions drawn from the above studies conducted are summarized and the gaps in the field and need for further research are highlighted
Active remote sensing of the atmosphere using lasers
No full textThe potential of the laser radar or lidar technique (lidar is an acronym for light detection and ranging) and the present state of the art of the technology for remote sounding of atmospheric constituents and meteorological parameters are reviewed. Based on lidar devices developed at the Indian Institute of Tropical Meteorology, Pune, a review of measurements of some of these parameters is given. The scattering and absorption processes that occur due to the interaction of the laser radiation with the atmosphere and their application to the retrieval of information on various atmospheric parameters are summarized. The future scope of the lidar technique for probing the composition and physical state of the atmosphere is also outlined
Variations in aerosol optical and microphysical properties during an Indian festival observed with space-borne and ground-based observations
Get PDFThis study analyzes changes in the response of meteorological parameters, aerosol, ozone, and water vapor properties over a tropical urban station in Pune, India, using ground-based and satellite data sets from February 23 to March 4, 2010 covering the Holi festival period. Continuous ground-based measurements of Microprocessor-based Total Ozone Portable Spectrometer (Microtops II) were made. The variations in aerosol optical depth (AOD) showed higher values on March 1, 2010 which coincide with the peak festival time. Using the least squares method, A °ngström exponent (α) is calculated in the spectral interval of 340-1020 nm, along with the coefficient a2 of the second-order polynomial fit to the plot of log AOD versus the log wavelength. The correlation between the coefficient a2 vs. AOD 500 nm is discussed. Results from ground-based Microtops and CIMEL sun-sky radiometer observations are also found to match well with satellite retrievals. The aerosol index (AI) derived from the Ozone Monitoring Instrument (OMI) along with AOD derived from the Moderate-Resolution Imaging Spectrometer (MODIS) indicate positive correlation. This suggests that satellite observations over the region confirm the presence of absorbing aerosols mainly due to bio-mass burning and colored powder spray activities during the festival
On the atmospheric tidal wind variations at meteor heights
No full textMonthly averages of the zonal and meridional neutral wind data recorded over Obninsk (55°N), Heiss Island (805°N) and Molodezhnaya (67°S), using meteor radar technique, during the period 1967-71 are analyzed in detail in terms of prevailing and periodic components. Results of the geographical variation of the data reveal the presence of comparatively higher amplitudes of the wind components at Molodezhnaya station. It is observed that higher amplitudes of the semi-diurnal component are mostly associated with lower phases at all the three stations. The momentum flux due to the diurnal and semi-diurnal wind components are calculated for all the seasons at each site. The results are compared with the measurements made at other latitudinal stations
Association between aerosol scattering and meteorological parameters during lunar eclipse
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