A micro pulse lidar (MPL) has been indigenously designed and developed at the National Physical
Laboratory, New Delhi using a 532 nm, 500 pico second pulsed laser having average power of 50mW (at 7.5
KHz PRR). Photon counting technique has been incorporated using the conventional optics, multichannel
scaler (Stanford Research Systems SR430) and high sensitive photomultiplier tube. The sensitivity, range and
bin etc are computer controlled in the present system. The interfacing between MPL and computer has been
achieved by serial (RS232) and parallel printer port. The necessary software and graphical user interface has
been developed using visual basic. In addition to this the telescope cover status sensing circuit has been
incorporated to avoid conflict between dark count and background acquisition. The micro pulse lidar will be
used for the aerosol, boundary layer and the cloud studies at a bin resolution of 6 meters. In the present
communication the details of the system and preliminary results will be presented.
Tropospheric aerosol play an important role in regional meteorology and energy balance of radiation. Specially in huge
urban areas like New Delhi, India a large amount of aerosols from anthropogenic origins is continuously produced and
released in the atmospheric boundary layer. The effect of aerosols on atmospheric energy balance is a key global
change problem. Aerosol vertical distribution monitoring can be significantly improved using active remote sensing by
Lidar. Micro-pulse lidar proved to be an important state of art tool providing a detailed picture of the vertical structure
of boundary layer and elevated dust or tiny aerosol. Aerosols are spatially and temporarily varied in short period. The
movement of the pollutants can be tracked or mapped out as a function of time by the help of Lidar which is very
important to understand the dynamics of particulate matters. The in-situ measurements of aerosol at ground will not be
a true representation of total aerosol and its vertical distribution in the atmosphere, therefore the monitoring of vertical
profiles of aerosol is very important and timely which is not possible by conventional methods. In view of the above a
micro pulse lidar is being setup at NPL, New Delhi to get vertical profiles of aerosol to study the radiative forcing and
characterization of aerosols using depolarization ratio. In the present communication details of the system and some
preliminary results will be presented.
Human activities have been influencing the global atmosphere since the beginning of the industrial era, causing shifts from its natural state. The measurements have shown that tropospheric ozone is increasing gradually due to anthropogenic activities. Surface ozone is a secondary pollutant, its concentration in lower troposphere depends upon its precursors (CO, CH4, non methane hydrocarbons, NOx) as well as weather and transport phenomenon. The surface ozone exceeding the ambient air quality standard is health hazard to human being, animal and vegetation. The regular information of its concentrations on ground levels is needed for setting ambient air quality objectives and understanding photo chemical air pollution in urban areas. A Differential Absorption Lidar (DIAL) using a tunable CO2 laser has been designed and developed at National Physical Laboratory, New Delhi, to monitor water vapour, surface ozone, ammonia, ethylene etc. Some times ethylene and surface ozone was found to be more than 40 ppb and 140 ppb respectively which is a health hazard. Seasonal variation in ozone concentrations shows maximum in the months of summer and autumn and minimum in monsoon and winter months. In present communication salient features of experimental set up and results obtained will be presented in detail.
The earth's environment is constantly changing. Scientific evidence indicates that these changes are result of a complex interplay among a number of natural and human related systems. Therefore in recent times, concern has grown about global change studies - which is related to natural and anthropogenic alteration of the Earth's environment. The atmospheric trace gases play an important role in many processes such as biosphere-troposphere interaction, the chemistry of troposphere and the troposphere - stratosphere exchange. Therefore measurement of various minor constituents in the atmosphere is of great significance to understand physics, Chemistry and dynamics of the atmosphere. A Differential Absorption Lidar (DIAL) system using a tunable CO2 laser has been designed and developed at National Physical Laboratory, New Delhi, to monitor various minor constituents in the atmosphere. The system is being used to monitor water vapour, surface ozone, ammonia and ethylene concentration. Some times these trace species were found to be quite high which is a health hazard. Some measurements have also been made to estimate the liquid water contents of the fog by the measurement of CO2 laser transmission at 9.5 μm. The liquid water content was found to be in the range 0.008 - 0.2 gm/m3 depending on the density of fog. In the present communication salient features of experimental set up and results obtained will be presented in detail.
The measurement of various minor constituents in the atmosphere is of great significance to understand physics, Chemistry and dynamics of the atmosphere. Ozone in the troposphere is one of the most important trace species as it is a greenhouse gas trapping the longwave radiation in 9.6 ?m band affecting the energy budget of the earthatmosphere system. It is also a pollutant produced as a result of anthropogenic activities such as fossil fuel burning and has potential to affect human health and vegetation if it is allowed to attain high concentrations. Water vapour also plays a significant role in climate studies and the chemistry of the atmosphere. Ethylene is an urban pollutant and its concentration as low as 10 ppb is toxic to plants. A differential absorption lidar system using a tunable CO2 laser has been designed and developed at National Physical Laboratory, New Delhi, to monitor various minor constituents in the atmosphere. Some times ethylene concentration was found to be more than 20 ppb while that of surface ozone was more than 140 ppb which is a health hazard. In this paper salient features of experimental set up and results obtained will be presented in detail.
Conference Committee Involvement (4)
Lidar Remote Sensing for Environmental Monitoring IX
18 November 2008 | Noumea, New Caledonia
Lidar Remote Sensing for Environmental Monitoring VII
14 November 2006 | Goa, India
Lidar Remote Sensing for Industry and Environmental Monitoring V
9 November 2004 | Honolulu, Hawai'i, United States
Lidar Remote Sensing for Industry and Environment Monitoring III
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