Atmospheric Acetaldehyde: Importance of Air-Sea Exchange and a Missing Source in the Remote Troposphere.

We report airborne measurements of acetaldehyde (CH3CHO) during the first and second deployments of the National Aeronautics and Space Administration (NASA) Atmospheric Tomography Mission (ATom). The budget of CH3CHO is examined using the Community Atmospheric Model with chemistry (CAM-chem), with a newly-developed online air-sea exchange module. The upper limit of the global ocean net emission of CH3CHO is estimated to be 34 Tg a-1 (42 Tg a-1 if considering bubble-mediated transfer), and the ocean impacts on tropospheric CH3CHO are mostly confined to the marine boundary layer. Our analysis suggests that there is an unaccounted CH3CHO source in the remote troposphere and that organic aerosols can only provide a fraction of this missing source. We propose that peroxyacetic acid (PAA) is an ideal indicator of the rapid CH3CHO production in the remote troposphere. The higher-than-expected CH3CHO measurements represent a missing sink of hydroxyl radicals (and halogen radical) in current chemistry-climate models

UAS Chromatograph for Atmospheric Trace Species (UCATS) – a versatile instrument for trace gas measurements on airborne platforms

UCATS (the UAS Chromatograph for Atmospheric Trace Species) was designed and built for observations of important atmospheric trace gases from unmanned aircraft systems (UAS) in the upper troposphere and lower stratosphere (UTLS). Initially it measured major chlorofluorocarbons (CFCs) and the stratospheric transport tracers nitrous oxide (N2O) and sulfur hexafluoride (SF6), using gas chromatography with electron capture detection. Compact commercial absorption spectrometers for ozone (O3) and water vapor (H2O) were added to enhance its capabilities on platforms with relatively small payloads. UCATS has since been reconfigured to measure methane (CH4), carbon monoxide (CO), and molecular hydrogen (H2) instead of CFCs and has undergone numerous upgrades to its subsystems. It has served as part of large payloads on stratospheric UAS missions to probe the tropical tropopause region and transport of air into the stratosphere; in piloted aircraft studies of greenhouse gases, transport, and chemistry in the troposphere; and in 2021 is scheduled to return to the study of stratospheric ozone and halogen compounds, one of its original goals. Each deployment brought different challenges, which were largely met or resolved. The design, capabilities, modifications, and some results from UCATS are shown and described here, including changes for future missions.Support was provided for HIPPO by NSF award no. AGS-0628452, for ATTREX by NASA Earth Venture program award no. NNA11AA55I, and for ATom by NASA award no. NNH17AE26I; additional support was provided by NASA Upper Atmosphere Research Program award no. NNH13AV69I. This work was also supported in part by the NOAA Cooperative Agreement with CIRES, NA17OAR4320101

The Science Performance of JWST as Characterized in Commissioning

This paper characterizes the actual science performance of the James Webb Space Telescope (JWST), as determined from the six month commissioning period. We summarize the performance of the spacecraft, telescope, science instruments, and ground system, with an emphasis on differences from pre-launch expectations. Commissioning has made clear that JWST is fully capable of achieving the discoveries for which it was built. Moreover, almost across the board, the science performance of JWST is better than expected; in most cases, JWST will go deeper faster than expected. The telescope and instrument suite have demonstrated the sensitivity, stability, image quality, and spectral range that are necessary to transform our understanding of the cosmos through observations spanning from near-earth asteroids to the most distant galaxies.Comment: 5th version as accepted to PASP; 31 pages, 18 figures; https://iopscience.iop.org/article/10.1088/1538-3873/acb29

The Campus Chat

Weekly student newspaper from the North Texas State College in Denton, Texas that includes local, state, and campus news along with advertising

The Campus Chat

Weekly student newspaper from the North Texas State College in Denton, Texas that includes local, state, and campus news along with advertising

The Campus Chat

Weekly student newspaper from the North Texas State College in Denton, Texas that includes local, state, and campus news along with advertising

The Campus Chat

Weekly student newspaper from the North Texas State College in Denton, Texas that includes local, state, and campus news along with advertising

The Campus Chat

Weekly student newspaper from the North Texas State College in Denton, Texas that includes local, state, and campus news along with advertising

Effect of Hydrocarbon Production and Depressurization on Subsidence and Fault Reactivation

Subsurface fluid withdrawal is one of the most common causes of land subsidence. Subsurface fluids include water, oil, gas, and steam. Examples of subsidence induced by groundwater withdrawal significantly outnumber those induced by hydrocarbon production. Several severe subsidence cases induced by hydrocarbon production were documented including Goose Creek field (Pratt and Johnson, 1926), Wilmington field in Long Beach, California, Lost Hill and Belridge fields in California, Bolivar coast in Venezuela (Nunez and Escojido, 1976), and Ekofisk field in the North Sea (Sulak, 1991). Ekofisk field is the most recent and costly example. Ekofisk field was discovered in 1969, and production from the 700- to 1,000-ft-thick geopressured high-porosity chalk reservoir (top at 9,600 ft subsea) began in the 1970s. By 1984, the seabed under the Ekofisk complex had subsided about 10 ft. To stabilize platforms and facilities, an unprecedented billion-dollar project was initiated in 1987 to elevate the four platforms an additional 20 ft and to construct protective barriers around the hydrocarbon storage tank. In addition, gas and water have been injected to increase reservoir pressure and arrest active subsidence. Nevertheless, the local seabed has subsided continuously to 26 ft in 2001. In coastal southeast Texas, land subsidence has been severe in the Houston/Galveston area. However, despite enormous oil and gas production from Frio and Miocene formations, most land subsidence and surface faults in the area have been attributed more to regional shallow groundwater withdrawal than to hydrocarbon production (Kreitler, 1976; Verbeek and Clanton, 1981; Holzer and Bluntzer, 1984; Gabrysch and Coplin, 1987). Holzer and Bluntzer (1984) showed that hydrocarbon production has caused an additional 0.1 to 0.2 m of local subsidence near some oil and gas fields. To better quantify the impact of hydrocarbon production on subsidence and fault reactivation, we need to eliminate the effects of groundwater withdrawals by selecting fields having insignificant groundwater withdrawals relative to hydrocarbon production. Two field areas in the coastal southeast Texas-Port Neches in Orange County and Caplen in Galveston County-satisfy this prerequisite. Both areas contain active surface faults and wetlands that have been inundated by marine waters (White and Morton, 1997). Most Port Neches and Caplen hydrocarbon production occurred between 1940 and 1970.Bureau of Economic Geolog