edu.ucar.opensky::articles:24472 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-24T23:08:43.948634 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d7pr80db https://doi.org/10.5281/zenodo.4776977 https Related Dataset #1 PACT-1D model version v1 for the CALNEX case study - output files Quantifying nitrous acid formation mechanisms using measured vertical profiles during the CalNex 2010 campaign and 1D column modeling 2021-07-16T00:00:00Z publication https://n2t.org/ark:/85065/d7pr80db https://doi.org/10.1029/2021JD034689 Tuite, K. author Thomas, J. L. author Veres, P. R. author Roberts, J. M. author Stevens, P. S. author Griffith, S. M. author Dusanter, S. author Flynn, J. H. author Ahmed, S. author Emmons, Louisa K. author Kim, S. author Washenfelder, R. author Young, C. author Tsai, C. author Pikelnaya, O. author Stutz, J. author UCAR/NCAR - Library publisher Nitrous acid (HONO) is an important radical precursor that can impact secondary pollutant levels, especially in urban environments. Due to uncertainties in its heterogeneous formation mechanisms, models often under predict HONO concentrations. A number of heterogeneous sources at the ground have been proposed but there is no consensus about which play a significant role in the urban boundary layer. We present a new one-dimensional chemistry and transport model which performs surface chemistry based on molecular collisions and chemical conversion, allowing us to add detailed HONO formation chemistry at the ground. We conducted model runs for the 2010 CalNex campaign, finding good agreement with observations for key species such as O3, NOx, and HOx. With the ground sources implemented, the model captures the diurnal and vertical profile of the HONO observations. Primary HOx production from HONO photolysis is 2–3 times more important than O3 or HCHO photolysis at mid-day, below 10 m. The HONO concentration, and its contribution to HOx, decreases quickly with altitude. Heterogeneous chemistry at the ground provided a HONO source of 2.5 × 1011 molecules cm−2 s−1 during the day and 5 × 1010 molecules cm−2 s−1 at night. The night time source was dominated by NO2 hydrolysis. During the day, photolysis of surface HNO3/nitrate contributed 45%–60% and photo-enhanced conversion of NO2 contributed 20%–45%. Sensitivity studies addressing the uncertainties in both photolytic mechanisms show that, while the relative contribution of either source can vary, HNO3/nitrate is required to produce a surface HONO source that is strong enough to explain observations. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication Copyright 2021 American Geophysical Union. None eng geoscientificInformation