We present a detailed budget of formic and acetic acids, two of the most abundant trace gases in the atmosphere. Our bottom-up estimate of the global source of formic and acetic acids are ~1200 and ~1400 Gmol yr⁻¹, dominated by photochemical oxidation of biogenic volatile organic compounds, in particular isoprene. Their sinks are dominated by wet and dry deposition. We use the GEOS-Chem chemical transport model to evaluate this budget against an extensive suite of measurements from ground, ship and satellite-based Fourier transform spectrometers, as well as from several aircraft campaigns over North America. The model captures the seasonality of formic and acetic acids well but generally underestimates their concentration, particularly in the Northern midlatitudes. We infer that the source of both carboxylic acids may be up to 50% greater than our estimate and report evidence for a long-lived missing secondary source of carboxylic acids that may be associated with the aging of organic aerosols. Vertical profiles of formic acid in the upper troposphere support a negative temperature dependence of the reaction between formic acid and the hydroxyl radical as suggested by several theoretical studies

[1] High Resolution Dynamics Limb Sounder (HIRDLS) temperature profiles are analyzed to derive global properties of gravity waves. We describe a wavelet analysis technique that determines covarying wave temperature amplitude in adjacent temperature profile pairs, the wave vertical wavelength as a function of height, and the horizontal wave number along the line joining each profile pair. The analysis allows a local estimate of the magnitude of gravity wave momentum flux as a function of geographic location and height on a daily basis. We examine global distributions of these gravity wave properties in the monthly mean and on an individual day, and we also show sample instantaneous wave events observed by HIRDLS. The results are discussed in terms of previous satellite and radiosonde observational analyses and middle atmosphere general circulation model studies that parameterize gravity wave effects on the mean flow. The high vertical and horizontal resolution afforded by the HIRDLS measurements allows the analysis of a wider range of wave vertical and horizontal wavelengths than previous studies and begins to show individual wave events associated with mountains and convection in high detail. Mountain wave observations show clear propagation to altitudes in the mesosphere.

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( 1 and Fig. 1(a)). These trends are primarily due to stricter air quality emission controls that candidate species for studying hemispheric gradients and long-term changes. 57We analyzed ten years of NMHC data collected at 44 remote global sampling sites from NOAA's 58 Global Greenhouse Gas Reference Network (GGGRN). We also include data from in-situ moni-59 toring at Summit, Greenland 8 , at Hohenpeissenberg (HPB) in Southern Germany 9 , Jungfraujoch resolved in-situ record from HPB has its minimum in 2009 ( Fig. 1 (e)), in agreement with the JFJ 78 FTIR column observations ( Fig. 1(c)). Focusing on the most recent five years (2009.5 -2014.5) 79 we find variable results in the observed rate of change; however, a consistent picture emerges 80 that shows the largest increases at NH sites (Fig. 3). Of 33 NH sites, 7 exhibit ethane growth 81 rates > 50 pmol mol -1 yr -1 , and 10 sites exhibit growth rates between 25-50 pmol -1 yr -1 (Table S1). one from JFJ ( Fig. 1(c)) 12 , and the other one from Lauder, New Zealand ( Fig. 1(d) emission increases outside of NA that currently cannot be well defined due to the sparsity of 170 observations in those regions (for instance in the middle-East, Africa, and Asia).

Sharp rises in the atmospheric abundance of ethane (C 2 H 6 ) have been detected from 2009 onwards in the Northern Hemisphere as a result of the unprecedented growth in the exploitation of shale gas and tight oil reservoirs in North America. Using time series of C 2 H 6 total columns derived from groundbased Fourier transform infrared (FTIR) observations made at five selected Network for the Detection of Atmospheric Composition Change sites, we characterize the recent C 2 H 6 evolution and determine growth rates of ∼5% yr −1 at mid-latitudes and of ∼3% yr −1 at remote sites. Results from CAM-chem simulations with the Hemispheric Transport of Air Pollutants, Phase II bottom-up inventory for anthropogenic emissions are found to greatly underestimate the current C 2 H 6 abundances. Doubling global emissions is required to reconcile the simulations and the observations prior to 2009. We further estimate that North American anthropogenic C 2 H 6 emissions have increased from 1.6 Tg yr −1 in 2008 to 2.8 Tg yr −1 in 2014, i.e. by 75% over these six years. We also completed a second simulation with new top-down emissions of C 2 H 6 from North American oil and gas activities, biofuel consumption and biomass burning, inferred from space-borne observations of methane (CH 4 ) from Greenhouse Gases Observing SATellite. In this simulation, GEOS-Chem is able to reproduce FTIR measurements at the mid-latitudinal sites, underscoring the impact of the North American oil and gas development on the current C 2 H 6 abundance. Finally we estimate that the North American oil and gas emissions of CH 4 , a major greenhouse gas, grew from 20 to 35 Tg yr −1 over the period 2008-2014, in association with the recent C 2 H 6 rise.