Measurements of ClO (Brune et al., 1990) acquired during the Airborne Arctic Stratospheric Expedition are used to infer concentrations of reactive chlorine (ClO+2 × Cl 2 O 2 ). Observed fields of potential temperature and potential vorticity are used to extrapolate in situ data to larger regions of the vortex. Calculated values of the loss rate of O 3 , based on estimates of reactive chlorine and measurements of BrO (Toohey et al., 1990), suggest that the loss of O 3 was about 12% for levels of the atmosphere with potential temperatures between 440 and 470 K over the 39 day duration of the ER‐2 flights into the polar vortex. Calculated loss rates agree with observed rates of removal of O 3 , although significant uncertainties exist for each.
The absorption spectrum of nitrous oxide (N 2 O) has been determined at five temperatures from 194 to 302 K and over the wavelength range 173‐240 nm. The absorption cross sections as a function of wavelength and temperature are expressed by a nine‐term polynomial in a form useful for atmospheric models. The high resolution structure between 173 and 190 nm has been observed more clearly than by previous studies.
In the framework of the ACCLIP project (Asian summer monsoon Chemical and CLimate Impacts project), a measurement campaign was conducted during summer 2022 in the Western Pacific region, to investigate the impact of the Asian Summer Monsoon (ASM) on the composition of the upper troposphere and lower stratosphere (UTLS). Fifteen research flights were carried out by the NASA WB-57 stratospheric aircraft and 14 by the NCAR/NSF GV, with base in Osan (South Korea), covering a large region on the eastern edge of the ASM anticyclone.We report on the Carbon Monoxide (CO) measurements performed by three different mid-infrared absorption spectrometers (COLD2, COMA and ACOS) installed onboard the WB-57 and by two different infrared absorption spectrometers (Aerodyne-CO and Picarro G2401) installed on the GV. Positive CO anomalies, never measured before in the UTLS outside direct biomass burning plumes, were collected by all sensors, showing a very good agreement. During the flight of the 19th of August, CO mixing ratio values higher than 250 ppb were registered at altitude around 14-15 km.A comparison with the CO observations measured by the instrument COLD2 during the StratoClim (Stratospheric and upper tropospheric processes for better Climate predictions) campaign, conducted in summer 2017 from Kathmandu (Nepal), will be presented. Particular attention will be paid to the CO difference observed in the UTLS, by sampling the anticyclone directly from the Tibetan Plateau during StratoClim campaign or from the Western Pacific during ACCLIP.
Simultaneous measurements of CO 2 and N 2 O from the NASA ER‐2 aircraft during SPADE deployments in November 1992, April/May 1993, and October 1993 provide new information on transport rates in the lower stratosphere. The tropospheric seasonal cycle in CO 2 , superimposed on the long‐term trend, is observed to propagate into the stratosphere. The compact correlations observed between CO 2 and N 2 O indicate that meridional transport is sufficiently rapid to create a uniform set of relationships over the northern hemisphere up to at least 21 km even though CO 2 changes significantly on a time scale of 8 to 12 weeks. The observed seasonal dependence of the correlations indicates that vertical transport above 20 km is slower in northern summer than in winter and slow throughout the year between 19 km and the tropopause. The inferred amplitude of the seasonal CO 2 oscillation in the stratosphere, viewed relative to N 2 O, places constraints on the mean latitude for air entering the stratosphere.
Mid‐latitude ozone data from ER‐2 aircraft measurements in 1989, 1991 and 1992 were examined to determine how sulfate aerosols from the eruption of Mt. Pinatubo had affected ozone at about 18 km. N 2 O was used as a tracer to help distinguish between chemical and dynamical aerosol effects. At 20–45°N in February 1992, ozone was about 10–20% lower than February 1989 and 1991, with respect to N 2 O. Data from Aug. 1991‐Mar. 1992 showed changes in ozone with respect to N 2 O, but the magnitude of those changes was not correlated with the magnitude of the changes in aerosol surface area density.
Airborne water vapor lidar measurements are used to observe moisture variability in tropopause folds, characterize ice supersaturation regions, compare satellite and in situ water vapor measurements, and reveal wave structure in aerosol and cloud distributions.
Abstract. In the southeast Atlantic, well-defined smoke plumes from Africa advect over marine boundary layer cloud decks; both are most extensive around September, when most of the smoke resides in the free troposphere. A framework is put forth for evaluating the performance of a range of global and regional atmospheric composition models against observations made during the NASA ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) airborne mission in September 2016. A strength of the comparison is a focus on the spatial distribution of a wider range of aerosol composition and optical properties than has been done previously. The sparse airborne observations are aggregated into approximately 2∘ grid boxes and into three vertical layers: 3–6 km, the layer from cloud top to 3 km, and the cloud-topped marine boundary layer. Simulated aerosol extensive properties suggest that the flight-day observations are reasonably representative of the regional monthly average, with systematic deviations of 30 % or less. Evaluation against observations indicates that all models have strengths and weaknesses, and there is no single model that is superior to all the others in all metrics evaluated. Whereas all six models typically place the top of the smoke layer within 0–500 m of the airborne lidar observations, the models tend to place the smoke layer bottom 300–1400 m lower than the observations. A spatial pattern emerges, in which most models underestimate the mean of most smoke quantities (black carbon, extinction, carbon monoxide) on the diagonal corridor between 16∘ S, 6∘ E, and 10∘ S, 0∘ E, in the 3–6 km layer, and overestimate them further south, closer to the coast, where less aerosol is present. Model representations of the above-cloud aerosol optical depth differ more widely. Most models overestimate the organic aerosol mass concentrations relative to those of black carbon, and with less skill, indicating model uncertainties in secondary organic aerosol processes. Regional-mean free-tropospheric model ambient single scattering albedos vary widely, between 0.83 and 0.93 compared with in situ dry measurements centered at 0.86, despite minimal impact of humidification on particulate scattering. The modeled ratios of the particulate extinction to the sum of the black carbon and organic aerosol mass concentrations (a mass extinction efficiency proxy) are typically too low and vary too little spatially, with significant inter-model differences. Most models overestimate the carbonaceous mass within the offshore boundary layer. Overall, the diversity in the model biases suggests that different model processes are responsible. The wide range of model optical properties requires further scrutiny because of their importance for radiative effect estimates.
Abstract. We describe a method for removing systematic biases of column-averaged dry air mole fractions of CO2 (XCO2) and CH4 (XCH4) derived from short-wavelength infrared (SWIR) spectra of the Greenhouse gases Observing SATellite (GOSAT). We conduct correlation analyses between the GOSAT biases and simultaneously retrieved auxiliary parameters. We use these correlations to bias correct the GOSAT data, removing these spurious correlations. Data from the Total Carbon Column Observing Network (TCCON) were used as reference values for this regression analysis. To evaluate the effectiveness of this correction method, the uncorrected/corrected GOSAT data were compared to independent XCO2 and XCH4 data derived from aircraft measurements taken for the Comprehensive Observation Network for TRace gases by AIrLiner (CONTRAIL) project, the National Oceanic and Atmospheric Administration (NOAA), the US Department of Energy (DOE), the National Institute for Environmental Studies (NIES), the Japan Meteorological Agency (JMA), the HIAPER Pole-to-Pole observations (HIPPO) program, and the GOSAT validation aircraft observation campaign over Japan. These comparisons demonstrate that the empirically derived bias correction improves the agreement between GOSAT XCO2/XCH4 and the aircraft data. Finally, we present spatial distributions and temporal variations of the derived GOSAT biases.
Abstract Water vapor mass mixing ratio profiles from NASA's Lidar Atmospheric Sensing Experiment (LASE) system acquired during the Atmospheric Radiation Measurement (ARM)–First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment (FIRE) Water Vapor Experiment (AFWEX) are used as a reference to characterize upper-troposphere water vapor (UTWV) measured by ground-based Raman lidars, radiosondes, and in situ aircraft sensors over the Department of Energy (DOE) ARM Southern Great Plains (SGP) site in northern Oklahoma. LASE was deployed from the NASA DC-8 aircraft and measured water vapor over the ARM SGP Central Facility (CF) site during seven flights between 27 November and 10 December 2000. Initially, the DOE ARM SGP Cloud and Radiation Testbed (CART) Raman lidar (CARL) UTWV profiles were about 5%–7% wetter than LASE in the upper troposphere, and the Vaisala RS80-H radiosonde profiles were about 10% drier than LASE between 8 and 12 km. Scaling the Vaisala water vapor profiles to match the precipitable water vapor (PWV) measured by the ARM SGP microwave radiometer (MWR) did not change these results significantly. By accounting for an overlap correction of the CARL water vapor profiles and by employing schemes designed to correct the Vaisala RS80-H calibration method and account for the time response of the Vaisala RS80-H water vapor sensor, the average differences between the CARL and Vaisala radiosonde upper-troposphere water vapor profiles are reduced to about 5%, which is within the ARM goal of mean differences of less than 10%. The LASE and DC-8 in situ diode laser hygrometer (DLH) UTWV measurements generally agreed to within about 3%–4%. The DC-8 in situ frost point cryogenic hygrometer and Snow White chilled-mirror measurements were drier than the LASE, Raman lidars, and corrected Vaisala RS80H measurements by about 10%–25% and 10%–15%, respectively. Sippican (formerly VIZ Manufacturing) carbon hygristor radiosondes exhibited large variabilities and poor agreement with the other measurements. PWV derived from the LASE profiles agreed to within about 3% on average with PWV derived from the ARM SGP microwave radiometer. The agreement between the LASE and MWR PWV and the LASE and CARL UTWV measurements supports the hypotheses that MWR measurements of the 22-GHz water vapor line can accurately constrain the total water vapor amount and that the CART Raman lidar, when calibrated using the MWR PWV, can provide an accurate, stable reference for characterizing upper-troposphere water vapor.
We present a climatology of O 3 , CO, and H 2 O for the upper troposphere and lower stratosphere (UTLS), based on a large collection of high‐resolution research aircraft data taken between 1995 and 2008. To group aircraft observations with sparse horizontal coverage, the UTLS is divided into three regimes: the tropics, subtropics, and the polar region. These regimes are defined using a set of simple criteria based on tropopause height and multiple tropopause conditions. Tropopause‐referenced tracer profiles and tracer‐tracer correlations show distinct characteristics for each regime, which reflect the underlying transport processes. The UTLS climatology derived here shows many features of earlier climatologies. In addition, mixed air masses in the subtropics, identified by O 3 ‐CO correlations, show two characteristic modes in the tracer‐tracer space that are a result of mixed air masses in layers above and below the tropopause (TP). A thin layer of mixed air (1–2 km around the tropopause) is identified for all regions and seasons, where tracer gradients across the TP are largest. The most pronounced influence of mixing between the tropical transition layer and the subtropics was found in spring and summer in the region above 380 K potential temperature. The vertical extent of mixed air masses between UT and LS reaches up to 5 km above the TP. The tracer correlations and distributions in the UTLS derived here can serve as a reference for model and satellite data evaluation.
