Urban emissions of water vapor in winter

Abstract

Elevated water vapor (H2Ov) mole fractions were occasionally observed downwind of Indianapolis, IN, and the Washington, D.C.‐Baltimore, MD, area during airborne mass balance experiments conducted during winter months between 2012 and 2015. On days when an urban H2Ov excess signal was observed, H2Ov emission estimates range between 1.6 × 104 and 1.7 × 105 kg s−1 and account for up to 8.4% of the total (background + urban excess) advected flow of atmospheric boundary layer H2Ov from the urban study sites. Estimates of H2Ov emissions from combustion sources and electricity generation facility cooling towers are 1–2 orders of magnitude smaller than the urban H2Ov emission rates estimated from observations. Instances of urban H2Ov enhancement could be a result of differences in snowmelt and evaporation rates within the urban area, due in part to larger wintertime anthropogenic heat flux and land cover differences, relative to surrounding rural areas. More study is needed to understand why the urban H2Ov excess signal is observed on some days, and not others. Radiative transfer modeling indicates that the observed urban enhancements in H2Ov and other greenhouse gas mole fractions contribute only 0.1°C d−1 to the urban heat island at the surface. This integrated warming through the boundary layer is offset by longwave cooling by H2Ov at the top of the boundary layer. While the radiative impacts of urban H2Ov emissions do not meaningfully influence urban heat island intensity, urban H2Ov emissions may have the potential to alter downwind aerosol and cloud properties.

Observational Constraints on the Formation of Cl2 From the Reactive Uptake of ClNO2 on Aerosols in the Polluted Marine Boundary Layer

“…All observations presented in this work are 10‐s averages of the data collected at 1–2 Hz to improve the signal to noise ratio while maintaining temporal resolution. More information on the WINTER campaign and instrumentation can be found in papers published as a special collection (Guo et al, ; Salmon et al, ; Fibiger et al, ; Jaeglé et al, ; Haskins et al, ; Kenagy et al, ; Lee, Lopez‐Hilfiker, Schroder, et al, ; Lee, Lopez‐Hilfiker, Veres, et al, ; McDuffie, Fibiger, Dubé, Lopez Hilfiker, et al, ; McDuffie, Fibiger, Dubé, Lopez‐Hilfiker, et al, ; Ren et al, ; Salmon et al, ; Schroder et al, ; Sullivan et al, ).…”

Methane Emissions From the Baltimore‐Washington Area Based on Airborne Observations: Comparison to Emissions Inventories

“…The equipment on the Purdue Duchess aircraft included a global positioning system and inertial navigation system (GPS/INS), a Best Air Turbulence (BAT) probe for 3‐D wind measurements, a Picarro cavity ring‐down spectroscopy analyzer (Model G2301‐m) for CH 4 , CO 2 , and water vapor (H 2 O) measurements, and a Los Gatos Research Model RMT‐200 nitrogen dioxide (NO 2 ) analyzer based on cavity enhanced absorption spectroscopy. Further details about the instrumentation on the Duchess have been provided elsewhere (Salmon et al, , ).…”

“…It is possible that there are some seasonal variations in CH 4 emissions from landfills and the estimated CH 4 emission rates in winter in this study may not be representative of other seasons. Ground-based studies have shown that CH 4 emissions from landfills are higher in winter than in summer mainly due to lower biological CH 4 oxidation in winter (Borjesson & Svensson, 1997;Christophersen et al, 2001;Rachor et al, 2013) and can be influenced by changes in barometric pressure, soil temperature, soil moisture, and wind (Lu & Kunz, 1981;Rachor et al, 2013;Xu et al, 2014;Young, 1992…”

Vertical profile observations of water vapor deuterium excess in the lower troposphere

“…Local-scale studies have examined the role of moisture source, condensation history, and land surface evapotranspiration on d-excess signatures (Benetti et al, 2014;Delattre et al, 2015;Griffis et al, 2016;Kelsey et al, 2018;Lai and Ehleringer, 2011;Uemura et al, 2008;Welp et al, 2012). Measurements of d excess in precipitation have been used to investigate below-cloud evaporation (Aemisegger et al, 2015;Froehlich et al, 2008;Wang et al, 2016) and mixing between the boundary layer (BL) and FT from stationary platforms near the surface or at high-altitude mountain sites (Bailey et al, 2015;Benetti et al, 2015;Froehlich et al, 2008;Galewsky, 2015;Lowenthal et al, 2016;Samuels-Crow et al, 2014). Kelsey et al (2018) conducted mobile traverses along leeward and windward slope roads of a mountain in an instrumented vehicle to report vertical profiles of d excess.…”