Optimizing and Characterizing EARL for the Stratospheric Aerosol Layer
Abstract:
We intend to use EARL to measure the Stratospheric Aerosol Layer (SAL) for volcanic particle (SO2) constitution and flux. Since intensity falls off at inverse the square distance, EARL’s signal from the SAL is much fainter than normal tropospheric viewing. Therefore, we need to first optimize EARL for the SAL by varying the PMT voltage to maximize the returned signal. Once optimized, we intend to take several night data sets throughout late October and early November, focusing specifically on the SAL, and to use the new EARL GUI to determine the relative density of SO2 in the SAL. We will create a catalog to help monitor the flux of SO2 in this layer and create a baseline data set by which to compare the change in SO2 over time. I have a moderate level of expertise with handling the EARL and little to no expertise with using the new GUI.
Scientific Justification for the Project:
We are specifically interested in how volcanic eruptions affect climate change. Toward this end, we wish to observe and monitor the SAL for volcanic particles. Volcanic particles do not actually float around the atmosphere; instead, they combine post-eruption with water droplets to form SO2 in the troposphere and become swept up into the SAL. The SO2 follows the current in the SAL, and ground-based lidar instruments like EARL have been used in the past to monitor the flux of SO2 in the SAL over time. We intend to use EARL to view the SO2 in the SAL and to compare our results with previous findings. If EARL can be optimized to view the SO2 in the SAL, then we can monitor SO2 flux and draw conclusions about climate change. First, however, we need to create a baseline of normal SAL aerosol amounts so that we can observe SO2 once another volcanic eruption occurs. Most of my research this semester will culminate in this.
The Stratospheric Aerosol Layer is a layer of the atmosphere inside of the stratosphere, discovered by Christian Junge, which contains particles that are predominantly made of sulfur and have a radius between .1 and 2 microns. Most of these particles are water-soluble [2]. The SAL affects solar radiation and ozone, and monitoring its constitution and flux is important for measurements and observations of climate change, volcanic particles, and aerosol pollutants. Most of the aerosols in this layer are due to the SO2 released from volcanic explosions, although some are natural biological products that rise from the troposphere and other aerosols are human-made [3]. The SAL generally ranges from fifteen to eighteen kilometers, just outside the normal range for which EARL is optimized. The EARL has initially only been optimized with the PMT voltage for altitudes of up to fourteen kilometers, so we need to first maximize the signal that the EARL receives for the altitude of fifteen to eighteen kilometers by varying the PMT voltage.
The figure above shows how much signal, which is relatively correlatable with the density of particles in the atmosphere above the EARL, the EARL receives as a function of altitude. This signal has been corrected for the range fall-off of intensity. Altitude is on the x-axis, and the received signal/particle density is on the y-axis. The dashed line is the atmospheric density that we get from sounding data. This graph shows us that the EARL is capable of measuring up to twenty kilometers. The bumps in the signal above the dashed line indicate that we received signal back that is not due to the normal density of the atmosphere. From the figure above, we can determine that there is some amount of observable aerosols in the Stratospheric Aerosol Layer. According to current research, the SAL does not currently have much SO2. Therefore, the current SAL is perfect for creating a baseline of background, non-volcanic aerosols. If we create a baseline of the normal amount of aerosols in the SAL, then we can work from the baseline to determine how much of the SAL is due to SO2 once another volcanic eruption occurs.
[1] Thomason, Larry. United States. Introduction on Stratospheric Aerosol. Hampton, VA: , 2001. Web. <http://aerosols.larc.nasa.gov/indexintro.html>.
[2] Junge, Christian. "A World-wide Stratospheric Aerosol Layer." Science. 133.3463 1478-1479. Web. 19 Sep. 2011.
[3] Thomason, Larry. United States. Introduction on Stratospheric Aerosol. Hampton, VA: , 2001. Web. <http://aerosols.larc.nasa.gov/indexintro.html>.
We intend to use EARL to measure the Stratospheric Aerosol Layer (SAL) for volcanic particle (SO2) constitution and flux. Since intensity falls off at inverse the square distance, EARL’s signal from the SAL is much fainter than normal tropospheric viewing. Therefore, we need to first optimize EARL for the SAL by varying the PMT voltage to maximize the returned signal. Once optimized, we intend to take several night data sets throughout late October and early November, focusing specifically on the SAL, and to use the new EARL GUI to determine the relative density of SO2 in the SAL. We will create a catalog to help monitor the flux of SO2 in this layer and create a baseline data set by which to compare the change in SO2 over time. I have a moderate level of expertise with handling the EARL and little to no expertise with using the new GUI.
Scientific Justification for the Project:
We are specifically interested in how volcanic eruptions affect climate change. Toward this end, we wish to observe and monitor the SAL for volcanic particles. Volcanic particles do not actually float around the atmosphere; instead, they combine post-eruption with water droplets to form SO2 in the troposphere and become swept up into the SAL. The SO2 follows the current in the SAL, and ground-based lidar instruments like EARL have been used in the past to monitor the flux of SO2 in the SAL over time. We intend to use EARL to view the SO2 in the SAL and to compare our results with previous findings. If EARL can be optimized to view the SO2 in the SAL, then we can monitor SO2 flux and draw conclusions about climate change. First, however, we need to create a baseline of normal SAL aerosol amounts so that we can observe SO2 once another volcanic eruption occurs. Most of my research this semester will culminate in this.
The Stratospheric Aerosol Layer is a layer of the atmosphere inside of the stratosphere, discovered by Christian Junge, which contains particles that are predominantly made of sulfur and have a radius between .1 and 2 microns. Most of these particles are water-soluble [2]. The SAL affects solar radiation and ozone, and monitoring its constitution and flux is important for measurements and observations of climate change, volcanic particles, and aerosol pollutants. Most of the aerosols in this layer are due to the SO2 released from volcanic explosions, although some are natural biological products that rise from the troposphere and other aerosols are human-made [3]. The SAL generally ranges from fifteen to eighteen kilometers, just outside the normal range for which EARL is optimized. The EARL has initially only been optimized with the PMT voltage for altitudes of up to fourteen kilometers, so we need to first maximize the signal that the EARL receives for the altitude of fifteen to eighteen kilometers by varying the PMT voltage.
The figure above shows how much signal, which is relatively correlatable with the density of particles in the atmosphere above the EARL, the EARL receives as a function of altitude. This signal has been corrected for the range fall-off of intensity. Altitude is on the x-axis, and the received signal/particle density is on the y-axis. The dashed line is the atmospheric density that we get from sounding data. This graph shows us that the EARL is capable of measuring up to twenty kilometers. The bumps in the signal above the dashed line indicate that we received signal back that is not due to the normal density of the atmosphere. From the figure above, we can determine that there is some amount of observable aerosols in the Stratospheric Aerosol Layer. According to current research, the SAL does not currently have much SO2. Therefore, the current SAL is perfect for creating a baseline of background, non-volcanic aerosols. If we create a baseline of the normal amount of aerosols in the SAL, then we can work from the baseline to determine how much of the SAL is due to SO2 once another volcanic eruption occurs.
[1] Thomason, Larry. United States. Introduction on Stratospheric Aerosol. Hampton, VA: , 2001. Web. <http://aerosols.larc.nasa.gov/indexintro.html>.
[2] Junge, Christian. "A World-wide Stratospheric Aerosol Layer." Science. 133.3463 1478-1479. Web. 19 Sep. 2011.
[3] Thomason, Larry. United States. Introduction on Stratospheric Aerosol. Hampton, VA: , 2001. Web. <http://aerosols.larc.nasa.gov/indexintro.html>.