Considering intentional stratospheric dehydration for climate benefits.

We introduce a climate intervention strategy focused on decreasing water vapor (WV) concentrations near the tropopause and in the stratosphere to increase outbound longwave radiation. The mechanism is the targeted injection of ice-nucleating particles (INP) in air supersaturated with respect to ice at high altitudes in the tropical entryway to the stratosphere. Ice formation in this region is a critical control of stratospheric WV.

Influence of Wildfire on Urban Ozone: An Observationally Constrained Box Modeling Study at a Site in the Colorado Front Range.

Increasing trends in biomass burning emissions significantly impact air quality in North America. Enhanced mixing ratios of ozone (O) in urban areas during smoke-impacted periods occur through transport of O produced within the smoke or through mixing of pyrogenic volatile organic compounds (PVOCs) with urban nitrogen oxides (NO = NO + NO) to enhance local O production. Here, we analyze a set of detailed chemical measurements, including carbon monoxide (CO), NO, and speciated volatile organic compounds (VOCs), to evaluate the effects of smoke transported from relatively local and long-range fires on O measured at a site in Boulder, Colorado, during summer 2020.

Ozone chemistry in western U.S. wildfire plumes.

Wildfires are a substantial but poorly quantified source of tropospheric ozone (O). Here, to investigate the highly variable O chemistry in wildfire plumes, we exploit the in situ chemical characterization of western wildfires during the FIREX-AQ flight campaign and show that O production can be predicted as a function of experimentally constrained OH exposure, volatile organic compound (VOC) reactivity, and the fate of peroxy radicals. The O chemistry exhibits rapid transition in chemical regimes.

Novel Analysis to Quantify Plume Crosswind Heterogeneity Applied to Biomass Burning Smoke.

We present a novel method, the Gaussian observational model for edge to center heterogeneity (GOMECH), to quantify the horizontal chemical structure of plumes. GOMECH fits observations of short-lived emissions or products against a long-lived tracer (e.g.

Global airborne sampling reveals a previously unobserved dimethyl sulfide oxidation mechanism in the marine atmosphere.

Dimethyl sulfide (DMS), emitted from the oceans, is the most abundant biological source of sulfur to the marine atmosphere. Atmospheric DMS is oxidized to condensable products that form secondary aerosols that affect Earth's radiative balance by scattering solar radiation and serving as cloud condensation nuclei. We report the atmospheric discovery of a previously unquantified DMS oxidation product, hydroperoxymethyl thioformate (HPMTF, HOOCHSCHO), identified through global-scale airborne observations that demonstrate it to be a major reservoir of marine sulfur.

Efficient transport of tropospheric aerosol into the stratosphere via the Asian summer monsoon anticyclone.

An enhanced aerosol layer near the tropopause over Asia during the June-September period of the Asian summer monsoon (ASM) was recently identified using satellite observations. Its sources and climate impact are presently not well-characterized. To improve understanding of this phenomenon, we made in situ aerosol measurements during summer 2015 from Kunming, China, then followed with a modeling study to assess the global significance.

Persistent Water-Nitric Acid Condensate with Saturation Water Vapor Pressure Greater than That of Hexagonal Ice.

A laboratory chilled mirror hygrometer (CMH), exposed to an airstream containing water vapor (H2O) and nitric acid (HNO3), has been used to demonstrate the existence of a persistent water-nitric acid condensate that has a saturation H2O vapor pressure greater than that of hexagonal ice (Ih). The condensate was routinely formed on the mirror by removing HNO3 from the airstream following the formation of an initial condensate on the mirror that resembled nitric acid trihydrate (NAT). Typical conditions for the formation of the persistent condensate were a H2O mixing ratio greater than 18 ppm, pressure of 128 hPa, and mirror temperature between 202 and 216 K.

A measurement of total reactive nitrogen, NOy, together with NO₂, NO, and O₃ via cavity ring-down spectroscopy.

We present a sensitive, compact detector that measures total reactive nitrogen (NOy), as well as NO2, NO, and O3. In all channels, NO2 is directly detected by laser diode based cavity ring-down spectroscopy (CRDS) at 405 nm. Ambient O3 is converted to NO2 in excess NO for the O3 measurement channel.

Real time in situ detection of organic nitrates in atmospheric aerosols.

A novel instrument is described that quantifies total particle-phase organic nitrates in real time with a detection limit of 0.11 microg m(-3) min(-1), 45 ppt min(-1) (-ONO(2)). Aerosol nitrates are separated from gas-phase nitrates with a short residence time activated carbon denuder.