In this study, we update and integrate a line-by-line (LBL) module for calculating the O2 cross section (6O2) within the Schumann-Runge Bands (SRB, 175.4-206.2 nm) into the Tropospheric Ultraviolet Visible (TUV) model V5.4. This coupling allows us to analyze the impact of precise 6O2 calculations on the photolysis rate coefficient of O2 (JO2) and over 20 other molecules (J-values) at different altitudes. To compute 6O2 within the SRB, the LBL module uses the HIgh-resolution TRANsmission molecular absorption (HITRAN) 2020 database and the local O2 absorption, while the standard TUV model uses the Koppers and Murtagh (K&M) parameterization, which considers the overhead O2 slant path. In addition to correcting previously unnoticed errors in HITRAN and K&M datasets, the updated model now allows a separate handling of the underlying Herzberg (HZC) and SchumannRunge (SRC) continuum in the wavelength region where they overlap with SRB (175.4-180 nm and 190-206.2 nm). Through TUV calculations, we found that JO2 differences between the standard K&M and LBL versions are up to 6% in the upper mesosphere and -2 % in the middle-upper stratosphere. These variations affect the tropospheric and/or stratospheric J-values of several long-lived and short-lived halogenated species differently, depending on their individual cross sections and the extent of overlap with SRB. Despite variability, persistent altitude-dependent patterns are identified and explained by absorption contributions within the underlying SRC and HZC ranges. In particular, the LBL J-values of HCFC-22, CFC-115 and CHCl3 are 12%, 8% and 2% lower in the middle-upper stratosphere, respectively, and up to 24% larger in the lower stratosphere, which is of relevance for the evolution of the ozone layer.

Abstract. Methane (CH4) is a powerful greenhouse gas with a global warming potential 84 times higher than carbon dioxide (CO2) over 20 years. CH4 is produced from many natural and anthropogenic sources which can be further classified as biogenic or thermogenic in origin. The largest biogenic sources result from anaerobic decay such as wetlands, melting permafrost, or the breakdown of organic matter in the guts of ruminant animals. Thermogenic CH4 is generated during the breakdown of organic matter at high temperatures and pressure within the Earth's crust, a process which also produces more complex trace hydrocarbons such as ethane (C2H6) and propane (C3H8). Emissions of thermogenic CH4 are dominated by the fossil fuel energy sector, and the presence of elevated C2H6 along with CH4 can be used to distinguish oil and gas emissions from biogenic sources. This work outlines the development and deployment of an Unmanned Aerial System (UAS) outfitted with a fast (1 Hz) and sensitive (1–2 ppb s-1) CH4 & C2H6 sensor and ultrasonic anemometer. The UAV platform is a vertical-takeoff, hexarotor vehicle capable of vertical profiling to 120 m altitude and plume sampling across scales up to 1 km. This system has been used for direct quantification of point sources, as well as distributed emitters such as landfills, with source rates as low as 0.04 kg h-1 and up to 1500 kg h-1. Simultaneous measurements of CH4 and C2H6 mixing ratios, vector winds, and positional data allows for source classification (biogenic versus thermogenic), differentiation, and emission rates without the need for modeling or a priori assumptions about winds, vertical mixing, or other environmental conditions. The UAS has been deployed throughout the Southwest United States for system validation and targeted quantification of various sources emitting at or below the detection limits of other aircraft and satellite systems. This system offers a direct, repeatable method of horizontal and vertical profiling of emission plumes at scales that provide complementary information for regional aerial surveys as well as local ground-based monitoring.

A recent study comparing ozone column depths and methane lifetimes at varied atmospheric O-2 (pO(2)) levels calculated in the Kasting-group 1-D photochemical model and the Whole Atmosphere Community Climate Model version 6 (WACCM6) 3-D model (Ji, Kasting, et al., 2023; ) has exposed weaknesses in both models in parameterizing photolysis in the O-2 Schumann-Runge bands, 175-205 nm. WACCM6 does a good job for Earth's present atmosphere but neglects scattering, which becomes important at low pO(2). The 1-D model includes scattering but is based on an out-of-date band model, and it neglects the temperature dependence of photolysis at low pO(2). We have revised and improved the 1-D photochemical model by replacing the old O-2 photolysis algorithm with a new correlated-k parameterization, which improves accuracy for all O(2)levels and all temperature profiles. The WACCM6 parameterization was also included in the 1-D model for comparative purposes. The correlated-k and WACCM6 photolysis algorithms agree well for both the present atmosphere and for an atmosphere containing 10(-3) times the present O-2 level, but only if multiple scattering is included at low pO(2). The correlated-k parameterization will be made available to photochemical modeling groups who might choose to adopt it.

Methane (CH4) is a powerful greenhouse gas that is produced by a diverse set of natural and anthropogenic emission sources. Biogenic methane sources generally involve anaerobic decay processes such as those occurring in wetlands, melting permafrost, or the digestion of organic matter in the guts of ruminant animals. Thermogenic CH4 sources originate from the breakdown of organic material at high temperatures and pressure within the Earth's crust, a process which also produces more complex trace hydrocarbons such as ethane (C2H6). Here, we present the development and deployment of an uncrewed aerial system (UAS) that employs a fast (1 Hz) and sensitive (1–0.5 ppb s−1) CH4 and C2H6 sensor and ultrasonic anemometer. The UAS platform is a vertical-takeoff, hexarotor drone (DJI Matrice 600 Pro, M600P) capable of vertical profiling to 120 m altitude and plume sampling across scales up to 1 km. Simultaneous measurements of CH4 and C2H6 concentrations, vector winds, and positional data allow for source classification (biogenic versus thermogenic), differentiation, and emission rates without the need for modeling or a priori assumptions about winds, vertical mixing, or other environmental conditions. The system has been used for direct quantification of methane point sources, such as orphan wells, and distributed emitters, such as landfills and wastewater treatment facilities. With detectable source rates as low as 0.04 and up to ∼ 1500 kg h−1, this UAS offers a direct and repeatable method of horizontal and vertical profiling of emission plumes at scales that are complementary to regional aerial surveys and localized ground-based monitoring.

Annually, ~ 3.6 million abandoned oil and gas wells in the U.S. emit a combined ~ 3.2 Tg methane (CH4), adversely affecting climate and regional air quality. However, these estimates depend on emission factors derived from inventorying sub-populations of wells, but which vary by orders of magnitude due to inadequate sampling numbers. This problem is exacerbated by regional differences requiring independent emission inventories and the recent identification of poorly characterized super-emitters that skew the distribution. Currently, U.S. funding to remediate orphaned wells lacks standardized quantification methods needed to both prioritize plugging and account for emission reductions. Sensitive, reliable, affordable, and scalable CH4 flux quantification methods are needed. We evaluate a simple Gaussian plume method constrained by in situ ground measurements of CH4 concentrations and winds to estimate the leak rate from an orphan well in the Permian basin. We derive a flux of 10.53 ± 1.16 kg CH4 h-1 during a venting procedure that agrees with the directly measured volumetric flow rate of 9.0 ± 0.25 kg CH4 h-1. This is 71% greater than the flux measured 7-months prior which induces a bias between bottom-up and top-down estimates. Additionally, we discovered a secondary leak through the surface-casing inferred as 0.43-0.67 kg CH4 h-1 by both our ground Gaussian analysis and by transecting the plume with an uncrewed aerial system (UAS). Our technique addresses operational needs by reducing sampling time of leak detection and quantification and good sensitivity to characterize wells emitting below the detection limit of satellites.

Precipitable water vapor (PWV) is the vertically integrated amount of water vapor in the atmosphere, and it is a valuable predictor for weather forecasting. Currently, the use of sophisticated instrumentation can limit the number of PWV measurement sites, which affects the accuracy of forecast models in regards to storm formation, strength, and the potential for precipitation. We have analyzed relationships between PWV and zenith sky temperature measurements for the dry climate zone found in the North American Desert Southwest, specifically over Socorro, New Mexico (34∘ N, 107∘ W). Daily measurements of the ground and zenith sky temperatures have been made at Socorro for two complete annual cycles using low-cost infrared thermal sensors. Radiosonde measurements of PWV from National Weather Service stations located in nearby Albuquerque and Santa Teresa, New Mexico, are input into our dataset and analyzed via a newly developed computational tool. Our results show that an exponential relationship between PWV and zenith sky temperature holds for the Desert Southwest, but with parameters that are different than those obtained previously over the more moist climate zone of the North American Gulf Coast. Model simulations can accurately reproduce the observed relationship between PWV and temperature, and the results suggest that half of the signal in temperature is directly related to changes in opacity due to changes in PWV, while the other half is due to changes in air temperature that usually accompany changes in PWV.

Total precipitable water (TPW) in the atmosphere ::::::::: Precipitable ::::: water ::::: vapor :::::: (PWV) : is the vertically integrated amount of atmospheric water in all of its phases. TPW :::: water :::::: vapor :: in ::: the :::::::::: atmosphere, ::: and :: it : is a valuable predictor for weather forecasting, and it is routinely measured using radiosondes, ground-based global positioning systems (GPS), sun photometers, or microwave radiometers. The use of these sophisticated instruments limits : . :::::::: Currently, ::: the ::: use ::: of ::::::::::: sophisticated ::::::::::::: instrumentation ::: can :::: limit the number of TPW ::::: PWV measurement sites, which affects the accuracy of forecast models in regards to storm forma5 tion, strength, and the potential for precipitation. We have analyzed this relationship for the much drier ::::::::::: relationships ::::::: between :::: PWV :::: and :::::: zenith ::: sky :::::::::: temperature ::::::::::::: measurements ::: for ::: the ::: dry : climate zone found in the ::::: North :::::::: American : Desert Southwest, specifically over Socorro, New Mexico (34◦N, 107◦W). Daily measurements of the ground and zenith sky temperatures have been made at Socorro for two complete annual cycles using ::::::: low-cost : infrared thermal sensors. Radiosonde TPW measurements ::::::::::: measurements ::: of :::: PWV : from National Weather Service stations located in nearby Albuquerque, and Santa Theresa ::::: Teresa, New 10 Mexico, are input into our dataset and analysed via a newly developed computational tool. Our results show that an exponential relationship between TPW :::: PWV : and zenith sky temperature also holds for the Desert Southwest, but with parameters that are different than those obtained for the :::::::: previously :::: over ::: the ::::: more ::::: moist ::::::: climate :::: zone :: of ::: the ::::: North ::::::::: American : Gulf Coast. Model simulations can accurately reproduce the observed relationship between TPW ::::: PWV and temperature, and the results suggest that half of the signal in temperature is directly related to direct changes in opacity due to changes in TPW :::: PWV, while the 15 other half is due to changes in air temperature that usually accompany changes in TPW :::: PWV.

Abstract. We quantify ozone variability in the upper troposphere and lower stratosphere (UTLS) by investigating lamination features in balloon measurements of ozone mixing ratio and potential temperature. Laminae are defined as stratified variations in ozone that meet or exceed a 10 % threshold for deviations from a basic state vertical profile of ozone. The basic state profiles are derived for each sounding using smoothing methods applied within a vertical coordinate system relative to the World Meteorological Organization (WMO) tropopause. We present results of this analysis for the 25-year record of ozonesonde measurements from Boulder, Colorado. The mean number of ozone laminae identified per sounding is about 9±2 (1σ). The root-mean-square relative amplitude is 20 %, and laminae with much larger amplitudes (>40 %) are seen in ∼ 2 % of the profiles. The vertical scale of detected ozone laminae typically ranges between 0.5 and 1.2 km. The lamina occurrence frequency varies significantly with altitude and is largest within ∼2 km of the tropopause. Overall, ozone laminae identified in our analysis account for more than one-third of the total intra-seasonal variability in ozone. A correlation technique between ozone and potential temperature is used to classify the subset of ozone laminae that are associated with gravity wave (GW) phenomena, which accounts for 28 % of all laminar ozone features. The remaining 72 % of laminae arise from non-gravity wave (NGW) phenomena. There are differences in both the vertical distribution and seasonality of GW versus NGW ozone laminae that are linked to the contrast in main generating mechanisms for each laminae type.

We validate the Ozone Monitoring Instrument (OMI) Ozone Profile (PROFOZ) product from October 2004 through December 2014 retrieved by the Smithsonian Astrophysical Observatory (SAO) algorithm against ozonesonde observations. We also evaluate the effects of OMI row anomaly (RA) on the retrieval by dividing the dataset into before and after the occurrence of serious OMI RA, i.e., pre-RA (2004–2008) and post-RA (2009–2014). The retrieval shows good agreement with ozonesondes in the tropics and midlatitudes and for pressure < ∼ 50 hPa in the high latitudes. It demonstrates clear improvement over the a priori down to the lower troposphere in the tropics and down to an average of ∼ 550 (300) hPa at middle (high) latitudes. In the tropics and midlatitudes, the profile mean biases (MBs) are less than 6 %, and the standard deviations (SDs) range from 5 to 10 % for pressure < ∼ 50 hPa to less than 18 % (27 %) in the tropics (midlatitudes) for pressure > ∼ 50 hPa after applying OMI averaging kernels to ozonesonde data. The MBs of the stratospheric ozone column (SOC, the ozone column from the tropopause pressure to the ozonesonde burst pressure) are within 2 % with SDs of < 5 % and the MBs of the tropospheric ozone column (TOC) are within 6 % with SDs of 15 %. In the high latitudes, the profile MBs are within 10 % with SDs of 5–15 % for pressure < ∼ 50 hPa but increase to 30 % with SDs as great as 40 % for pressure > ∼ 50 hPa. The SOC MBs increase up to 3 % with SDs as great as 6 % and the TOC SDs increase up to 30 %. The comparison generally degrades at larger solar zenith angles (SZA) due to weaker signals and additional sources of error, leading to worse performance at high latitudes and during the midlatitude winter. Agreement also degrades with increasing cloudiness for pressure > ∼ 100 hPa and varies with cross-track position, especially with large MBs and SDs at extreme off-nadir positions. In the tropics and midlatitudes, the post-RA comparison is considerably worse with larger SDs reaching 2 % in the stratosphere and 8 % in the troposphere and up to 6 % in TOC. There are systematic differences that vary with latitude compared to the pre-RA comparison. The retrieval comparison demonstrates good long-term stability during the pre-RA period but exhibits a statistically significant trend of 0.14–0.7 % year−1 for pressure < ∼ 80 hPa, 0.7 DU year−1 in SOC, and −0. 33 DU year−1 in TOC during the post-RA period. The spatiotemporal variation of retrieval performance suggests the need to improve OMI's radiometric calibration especially during the post-RA period to maintain the long-term stability and reduce the latitude/season/SZA and cross-track dependency of retrieval quality.

The vertical distributions of water vapor (H2O) and carbon monoxide (CO) in the tropical lower stratosphere are controlled largely by their mixing ratios near the tropopause and by ascending motions as part of the Brewer-Dobson circulation (BDC). The upward propagation of seasonal variations imprinted on H2O and CO vertical profiles, often referred to as the tropical tape recorder, can be used to derive the mean vertical velocity, (w) over bar*, in this region of the lower stratosphere where quasi-horizontal mixing is not strong enough to erase the seasonal tape recorder signals. We used Aura Microwave Limb Sounder observations of the tropical tape recorders from 2004 to 2014 to derive values of (w) over bar* at pressures between 90 and 16hPa (about 18 to 28km altitude). Mean vertical profiles of (w) over bar* are consistent with calculated velocities derived from net radiative heating rates based on observed temperature, humidity, cloud, and trace gas amounts. Temporal variations in (w) over bar* are dominated by a quasi-biennial oscillation (QBO) and seasonal cycles, with maximum upwelling coinciding with easterly phases of the QBO in zonal wind shear and during the November-December period of the seasonal cycle. Both the QBO and annual modes emphasize the importance of wave phenomena in modulating the strength of tropical upwelling in the BDC. Interannual anomalies in (w) over bar* are correlated with variations in the El Nino-Southern Oscillation (ENSO), with enhanced stratospheric upwelling during El Nino phases and reduced upwelling during La Nina. A small decreasing linear trend (similar to 6%/decade) in (w) over bar* is observed from 2005 to 2014, although confidence is low in identifying such a trend as part of a long-term change due to the influence of ENSO over this period.

We present a comprehensive comparison of polar processing diagnostics derived from the National Aeronautics and Space Administration (NASA) Modern Era Retrospective-analysis for Research and Applications (MERRA) and the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Reanalysis (ERA-Interim). We use diagnostics that focus on meteorological conditions related to stratospheric chemical ozone loss based on temperatures, polar vortex dynamics, and air parcel trajectories to evaluate the effects these reanalyses might have on polar processing studies. Our results show that the agreement between MERRA and ERA-Interim changes significantly over the 34 years from 1979 to 2013 in both hemispheres and in many cases improves. By comparing our diagnostics during five time periods when an increasing number of higher-quality observations were brought into these reanalyses, we show how changes in the data assimilation systems (DAS) of MERRA and ERA-Interim affected their meteorological data. Many of our stratospheric temperature diagnostics show a convergence toward significantly better agreement, in both hemispheres, after 2001 when Aqua and GOES (Geostationary Operational Environmental Satellite) radiances were introduced into the DAS. Other diagnostics, such as the winter mean volume of air with temperatures below polar stratospheric cloud formation thresholds (VPSC) and some diagnostics of polar vortex size and strength, do not show improved agreement between the two reanalyses in recent years when data inputs into the DAS were more comprehensive. The polar processing diagnostics calculated from MERRA and ERA-Interim agree much better than those calculated from earlier reanalysis data sets. We still, however, see fairly large differences in many of the diagnostics in years prior to 2002, raising the possibility that the choice of one reanalysis over another could significantly influence the results of polar processing studies. After 2002, we see overall good agreement among the diagnostics, which demonstrates that the ERA-Interim and MERRA reanalyses are equally appropriate choices for polar processing studies of recent Arctic and Antarctic winters.

Global water vapor (H2O) measurements from Microwave Limb Sounder (MLS) are used to evaluate upper tropospheric (UT) and lower stratospheric (LS) H2O products produced by NASA Modern-Era Retrospective Analysis for Research and Applications (MERRA), its newest release MERRA2, and European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Reanalyses. Focusing on the H2O amount and transport from UT to LS, we show that all reanalyses overestimate annual global mean UT H2O by up to similar to 150% compared to MLS observations. Substantial differences in H2O transport are also found between the observations and reanalyses. Vertically, H2O transport across the tropical tropopause (16-20 km) in the reanalyses is faster by up to similar to 86% compared to MLS observations. In the tropical LS (21-25 km), the mean vertical transport from ECMWF is 168% faster than the MLS estimate, while MERRA and MERRA2 have vertical transport velocities within 10% of MLS values. Horizontally at 100 hPa, both observation and reanalyses show faster poleward transport in the Northern Hemisphere (NH) than in the Southern Hemisphere (SH). Compared to MLS observations, the H2O horizontal transport for both MERRA and MERRA2 is 106% faster in the NH but about 42-45% slower in the SH. ECMWF horizontal transport is 16% faster than MLS observations in both hemispheres. The ratio of northward to southward transport velocities for ECMWF is 1.4, which agrees with MLS observation, while the corresponding ratios for MERRA and MERRA2 are about 3.5 times larger.

We present a case study based on balloon-borne ozone measurements during the SouthEast American Consortium for Intensive Ozonesonde Network Study in August-September 2013. Data from Socorro, NM (34 degrees N, 107 degrees W) show a layer of anomalously low ozone in the upper troposphere (UT) during 8-14 August. Back trajectories, UT jet analyses, and data from the Microwave Limb Sounder (MLS) on the Aura satellite indicate that this feature originated from the marine boundary layer in the eastern/central tropical Pacific, where several disturbances and one hurricane (Henriette) formed within an active region of the Intertropical Convergence Zone in early August 2013. The hurricane and nearby convection pumped boundary layer air with low ozone (20-30 ppbv) into the UT. This outflow was advected to North America 3-5 days later by a strong subtropical jet, forming a tongue of low ozone observed in MLS fields and a corresponding layer of low ozone in Socorro vertical profiles.

The global distribution of methane (CH4) in the stratosphere and lower mesosphere has been derived using coincident measurements of water vapor (H2O), carbon monoxide (CO), and nitrous oxide (N2O) from the Microwave Limb Sounder (MLS) instrument on the Aura satellite. The derivation method is based on empirical relationships between these species established using observations from the Atmospheric Chemistry Experiment—Fourier Transform Spectrometer (ACE-FTS) on the SCISAT I satellite. The observed correlation between CH4 and N2O from ACE-FTS is used to derive CH4 from MLS measurements of N2O in the lower stratosphere, extending from a pressure of 100 hPa to a range of 30–10 hPa, depending on atmospheric conditions. In the upper stratosphere and lower mesosphere, between 30–10 hPa and 0.1 hPa, correlations between CH4 and H2O are used to derive CH4 from MLS measurements of H2O. Coincident MLS measurements of CO are utilized to separate two distinct air mass regimes in the CH4 - H2O relationship. This new methane data set covers all seasons and latitudes observed by MLS over the course of the Aura mission from 2004 to 2014. Examples are shown demonstrating the consistency of MLS derived CH4 with other trace gas measurements.