Catherine F. Cahill

Theoretical Investigations on Potential Impacts of High-Latitude Volcanic Emissions of Heat, Aerosols and Water Vapor and their Interactions with Clouds and Precipitation

Augustine Volcano (located in the Cook Inlet of South Central Alaska at 59.4 o N and 153.4 o W) erupted in January 2006 and released, among other things, water vapor, radiation heat, and aerosols into the atmosphere. To determine the potential impact of volcanic emissions and ashfall on local weather, 16 simulations assuming artificial emission and ashfall scenarios were performed with the Weather Research and Forecasting model for 24 consecutive days starting the day before the first eruption. These simulations include (1) the control simulation without consideration of any volcanic perturbation, (2) four simulations with simplified scenarios for each individual volcanic factor (radiative heat from the caldera, water vapor, cloud condensation nuclei (CCN) and/or ice nuclei (IN) aerosols, and albedo change due to ashfall), and (3) 11 simulations containing all possible combinations of these factors. These 11 simulations serve to examine interactions among impacts of the different perturbations under the assumed scenarios. The impact of volcanic factors on local weather depends on the synoptic situation, emission strength, (combination of) volcanic factors, and interaction among impacts of factors if they occur concurrently. ANalysis Of VAriance shows that the greatest (statistically significant at the 95% or higher confidence level) volcanic impact occurs on relatively humid days and immediately downwind of the volcano (<50 km). Depending on relative humidity and temperature conditions, volcanic heat release can increase condensation and/or cloud top levels or reduce cloudiness. Due to non-linear cloud microphysical processes, meteorological responses to volcanic factors can diminish or enhance the impacts of the individual factors when factors occur concurrently. As an example, depending on the ambient conditions, concurrently occurring volcanic factors can lead to a decrease in precipitation at one time and an increase at another time. These findings indicate that in the immediate vicinity of erupting volcanoes, predicted cloud conditions and precipitation may be inaccurate due to the unknown volcanic forcing.

Evaluating the effect of ambient particulate pollution on DNA methylation in Alaskan sled dogs: Potential applications for a sentinel model of human health

BACKGROUND Exposure to ambient particulate matter (PM) is known to be associated with increased morbidity and mortality in human populations. During the winter months in Fairbanks, Alaska, severe temperature inversions lead to elevated concentrations of ambient PM smaller than 2.5 μm (PM2.5). Sled dogs represent an easily accessible environmentally exposed population that may yield findings informative for human health risk assessment. OBJECTIVES In this pilot study, we evaluated whether ambient PM was associated with markers of global methylation in sled dogs. METHODS Kennels were strategically recruited to provide a wide PM2.5 exposure gradient for the Fairbanks area. Continuous monitoring of ambient PM2.5 was conducted at each kennel during the winter of 2012/13 using a DustTrak 8530. Dogs received a physical examination and assessment of standard hematology and clinical chemistries. Global methylation was determined using the LUminometric Methylation Assay (LUMA) and 5-Methycytosine (5-mC) quantification. RESULTS Three sled dog kennels (n~30 dogs/kennel) were evaluated and sampled. The average PM2.5 concentrations measured for kennels A, B, and C were 90 μg/m(3), 48 μg/m(3), 16 μg/m(3) (p<0.0001), respectively. The average (standard deviation) global methylation percentage for each kennel measured by LUMA was 76.22 (1.85), 76.52 (1.82), and 76.72 (2.26), respectively. The average (standard deviation) global methylation percentage for each kennel measured by 5-mC was 0.16 (0.04), 0.15 (0.04), and 0.15 (0.05), respectively. There was no statistically significant difference between the three kennels and their average global methylation percentage either by LUMA or 5-mC. CONCLUSIONS In this study we evaluated global methylation using LUMA and 5-mC and found no differences between kennels, though exposure to ambient PM2.5 was significantly different between kennels. As more information becomes available regarding immunologically-related canine genes and functionally active promoter subunits, the utility of this surrogate could increase.

Compact eye-safe backscatter lidar for aerosol studies in urban polar environment

We report a Compact Eye-Safe Backscatter Lidar (CESBL) system conceived for tropospheric aerosol research in the Arctic environment. The instrument will play an active role in the investigation of Arctic Haze and Ice Fog during winter time; intercontinental transport of Asian dust during springtime; and Aerosol plumes released from forest fires during summer time. In addition the system will perform systematic observations of Arctic Boundary Layer dynamics and Cirrus clouds. The lidar works at 1.574 μm and delivers 200 mJ maximum per pulse at 10 Hz prf. The output beam is conveniently expanded to yield an Eye-Safe factor greater than 250 suitable to operate in Urban Environments. The receiver is aimed with a Cassegrain telescope F/10, 20 cm primary diameter. The collimation and focusing were designed using commercial optics to holds approximately 1mrad field of view over a detector surface of 0.2 mm diameter. Signal detection is made by an InGaAs-APD followed by amplifiers. The Lidar system is mounted on an optical breadboard on a steerable platform and integrated into a PXI National Instrument data acquisition computer providing two acquisition channels at 200 MS/s maximum; 200 MHz of maximum bandwidth; and 12 bits vertical resolution. The acquisition code runs in a Lab-View platform with visualization interface and acquisition options optimized for field work. In this article the lidar system characteristics and the concept design are discussed. Initial geophysical results are shown.

Using an unmanned aircraft to observe black carbon aerosols during a prescribed fire at the RxCADRE campaign

Black carbon (BC) aerosols impact the earths climate by absorbing solar radiation in the atmosphere and depositing on ice surfaces and lowering the albedo of those surfaces. Black carbon aerosols have been widely studied; however, using small unmanned aircraft systems (UAS) for the airborne study of the vertical and horizontal concentrations of BC is new territory. Using UAS to study BC poses some challenges due to size and weight restrictions of the aircraft, as well as issues that arise when adapting ground based instrumentation for use on different aircraft. University of Alaska Fairbanks researchers successfully integrated and flew a microAeth AE-51 on a Boeing ScanEagle to measure the concentration of BC and other absorbing and scattering particles during a prescribed fire experiment, RxCADRE, conducted at Eglin AFB, FL, during October and November 2012. The microAeth successfully collected black carbon aerosols in the smoke plume when the Boeing ScanEagle UAS encountered the plume.