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About January 2013

This page contains all entries posted to Physics Announcements in January 2013. They are listed from oldest to newest.

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January 2013 Archives

January 6, 2013

PhD Proposal - John Sullivan

Date: Monday, January 6, 2014
Time: 8:00 am
Location: PHYS 401

TITLE:
A New Differential Absorption Lidar Using Raman Cells to Measure Subhourly Variation of Tropospheric Ozone Profiles in the Baltimore - Washington D.C. region

ABSTRACT:
This proposal will detail the theory and background necessary for the ground based tropospheric ozone Differential Absorption Lidar (DIAL) system at the NASA Goddard Space Flight Center (Greenbelt, MD 38.99° N, 76.84° W, 57 meters ASL), with initial results from 500 m to 10 km in Summer 2013. Current atmospheric satellites cannot peer through the optically thick stratospheric ozone layer to remotely sense boundary layer tropospheric ozone. In order to monitor this lower ozone more effectively, NASA has funded the ground based Tropospheric Ozone Lidar Network (TOLNET) which currently consists of five stations across the US. The Goddard instrument is based on the Differential Absorption Lidar (DIAL) technique, which transmits three wavelengths, 266, 289 and 299 nm. Ozone is absorbed more strongly at 266 nm and 289 nm than at 299 nm. The DIAL technique exploits this difference between the returned backscatter signals to obtain the ozone number density as a function of altitude. The transmitted wavelengths are generated by focusing the output of a quadrupled Nd:YAG laser beam (266 nm) into a pair of Raman Cells, filled with high pressure Hydrogen and Deuterium. Stimulated Raman Scattering within the focus shifts the pump wavelength and the first Stokes shift in each cell produces the required wavelengths. With the knowledge of the ozone absorption coefficient at these two wavelengths, the range resolved number density can then be derived. A interesting scientific validation data set will be examined, which yields accurate initial results. There are currently surface ozone measurements hourly and ozonesonde launches occasionally, but this system will be the first to make continuous routine ozone profile measurements in the Washington, DC - Baltimore area.

January 9, 2013

PhD Proposal - Thishan Dharshana

Date: Wednesday, January 9, 2013
Time: 2:00 pm
Location: PHYS 401

Title
Improving estimates of CO emissions from biomass burning using FRP and its applicability to atmospheric models.

Abstract
Biomass burning is responsible for the second largest source of Carbon emissions that include Carbon Dioxide (CO2), Carbon Monoxide (CO), and Methane (CH4) emissions. Despite the necessity of quantifying these emissions, a reliable and an efficient approach is unavailable. Hence, we are proposing a new approach, with the focus on CO, a trace gas where the remote sensing is well established and generated from a variety of satellite sensors. For comparison and validation purposes, ARCTAS field campaign is selected.

Despite the multi-sensor capability of several satellites, such as the Terra satellite that we are using at the primary stage of the analysis: MOPITT sensor to obtain CO data, MISR sensor for smoke plume height and MODIS sensor for FRP, there still remains constraints to be addressed. For example, MOPITT sensor is primarily sensitive only to the mid-troposphere so it is not capable of retrieving CO near the fire origin. However, when these high concentrations travel downwind and reach the altitude threshold sensitive to MOPITT, it is detectable by the MOPITT sensor. Throughout the transport, these CO fields move with visible smoke plumes detected by MISR. So, MODIS detected fire locations are connected to MISR detected smoke plumes, which in turn connected to MOPITT detected CO fields.

In applying the above methodology, GEOS-5 wind data will be used with WRF-Chem model to produce the forward transport and to link CO emissions from their sources to the current atmospheric distributions. Then to get the emission time frames, HYSPLITT back-trajectory analysis will be used. To validate the products, airborne measurements will be used with CO data from AQUA AIRS and AURA TES.

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