Concern over Arctic methane (CH4) emissions has increased following recent discoveries of poorly understood sources and predictions that methane emissions from known sources will grow as Arctic temperatures increase. New efforts are required to detect increases and explain sources without being confounded by the multiple sources. Methods for distinguishing different sources are critical. We conducted measurements of atmospheric methane and source tracers and performed baseline global atmospheric modeling to begin assessing the climate impact of changes in atmospheric methane. The goal of this project was to address uncertainties in Arctic methane sources and their potential impact on climate by (1) deploying newly developed trace-gas analyzers for measurements of methane, methane isotopologues, ethane, and other tracers of methane sources in the Barrow, AK, (2) characterizing methane sources using high-resolution atmospheric chemical transport models and tracer measurements, and (3) modeling Arctic climate using the state-of-the-art high- resolution Spectral Element Community Atmosphere Model (CAM-SE).
During the month of January 2019, the TBS crew made progress revamping the equipment to prepare for upcoming 2019 flights. Both winches were upgraded using a SE encore E43 59.3:1 gearbox coupled with a Leeson Permanent magnet motor. This increased the torque capability by approximately 3x and the rotational speed by ~30%. The existing electronics system on one winch was repurposed to power four 3,500 lb ATV winches. These winches will automate the retrieval of the balloons allowing for retrieval during faster winds, and thus increasing potential operating conditions, while also improving crew safety. The ATV winches are expected to be added to the second winch in February. Finally, a new electronics box was designed which will be used to power the new winch motor. The new winch motors are variable speed, meaning they accept 0-180V and the speed correlates to the input voltage. The new electronics boxes will be mounted directly to the winches to allow the winches to be removed from the trailers in case of size/weight operating limitations. The winches will instead be powered directly by 220V generators vs the lead acid battery banks used by the previous systems.
UAS and TBS operations at Oliktok Point, Alaska, have laid the groundwork for extended and semiroutine operations of such vehicles by the DOE ARM program. This paper provided an overview of these activities, along with insights into obstacles overcome and initial science achieved. While measurements from these initial activities are just beginning to be analyzed, these observations demonstrate the value of the new perspectives offered by these platforms, including information on spatial variability and vertical structure, and over difficult-to-sample surfaces such as newly forming sea ice and partially frozen tundra. Over the next few years, the measurements obtained, and those to be collected in the near future, will continue to be analyzed and used for model and remote sensing retrieval development and for the production of scientific understanding. Some such studies are currently being prepared for publication, offering new insights into atmospheric thermodynamic structure, aerosol processes, cloud macro- and microphysics, and turbulent and radiative energy fluxes at high latitudes. Information gained on the efficient use of unmanned platforms in the Arctic will benefit future missions, while scientific insight from such activities will continue, providing a valuable complement to measurements obtained from ARM's surface-based sensors and those provided by crewed research aircraft and satellites.
This monthly report is intended to communicate the status of North Slope ARM facilities managed by Sandia National Labs. The report includes: budget, safety, instrument status, and North Slope facilities.
We have made the first continuous measurements of black carbon in Barrow, Alaska at the ARM aerosol-observing site at the NOAA Barrow Observatory using a Single-Particle Soot Photometer (SP2). These data demonstrate that BC particles are extremely small, and a majority of the particles (by number density) are smaller than 0.5 fg, the lower limit of reliability of the SP2. We developed the first numerical model capable of quantitatively reproducing the laser-induced incandescence (LII) and scattering signals produced by the SP2, the industry-standard BC instrument. Our model reproduces the SP2 signal temporally and spectrally and demonstrates that the current SP2 optical design allows substantial contamination of LII on the scattering signal. We ran CAM5-SE in nudged mode, i.e., by constraining the transport used in the model with meteorological data. The results demonstrate the problem observed previously of under-predicting BC at high latitudes. The cause of the discrepancy is currently unknown, but we suspect that it is associated with scavenging and rainout mechanisms.