Retrievals of atmospheric composition from near-infrared measurements require measurements of airmass to better than the desired precision of the composition. The oxygen bands are obvious choices to quantify airmass since the mixing ratio of oxygen is fixed over the full range of atmospheric conditions. The OCO-2 mission is currently retrieving carbon dioxide concentration using the oxygen A-band for airmass normalization. The 0.25% accuracy desired for the carbon dioxide concentration has pushed the required state-of-the-art for oxygen spectroscopy. To measure O2 A-band cross-sections with such accuracy through the full range of atmospheric pressure requires a sophisticated line-shape model (Rautian or Speed-Dependent Voigt) with line mixing (LM) and collision induced absorption (CIA). Models of each of these phenomena exist, however, this work presents an integrated self-consistent model developed to ensure the best accuracy. It is also important to consider multiple sources of spectroscopic data for such a study in order to improve the dynamic range of the model and to minimize effects of instrumentation and associated systematic errors. The techniques of Fourier Transform Spectroscopy (FTS) and Cavity Ring-Down Spectroscopy (CRDS) allow complimentary information for such an analysis. We utilize multispectrum fitting software to generate a comprehensive new database with improved accuracy based on these datasets. The extensive information will be made available as a multi-dimensional cross-section (ABSCO) table and the parameterization will be offered for inclusion in the HITRANonline database.

The complex susceptibility was measured on CoFe2O4 nanoparticle suspensions in the frequency range between 1 kHz and 1 MHz for different values of a superimposed static magnetic field. The maximum in the imaginary part χ″ of the ac susceptibility shifts to higher frequencies with increasing static magnetic field. The shift is theoretically modeled utilizing the magnetic field dependence of the Brownian relaxation time constant and assuming a distribution of hydrodynamic particle sizes. The mean hydrodynamic size as determined from the maximum of χ″ in zero field and the mean core size as obtained from the shift of the χ″ peak with static field agree very well with the data from transmission electron microscopy and dynamic light scattering measurements, respectively. The results indicate that both core and hydrodynamic size distributions can be determined from measurements on nanoparticle suspensions proposed that magnetic dipole-dipole interactions are negligible.

Jovian lightning flashes were characterized by a number of missions that visited Jupiter over the past several decades. Imagery from the Voyager 1 and Galileo spacecraft led to a flash rate estimate of ~4×10 -3 flashes/km 2 /yr on Jupiter. 1,2 The spatial extent of Voyager flashes was estimated to be ~30 km at half-width half-maximum intensity (HWHM), but the camera was unlikely to have detected the dim outer edges of the flashes given weak response to the brightest spectral line of Jovian lightning emission, the 656.3 nm H-alpha line of atomic hydrogen (known from lab experiments). 1,3-6 The spatial resolution of Galileo and New Horizons cameras allowed investigators to confirm twenty-two flashes with HWHM >42 km and estimate one between 37-45 km. 1,7,8,9 These flashes, with optical energies only comparable to terrestrial "superbolts" (2×10 8 -1.6×10 10 Joules), have historically been interpreted as tracers of moist convection originating near the 5 bar level of Jupiter's atmosphere (assuming photon scattering from points beneath the clouds). 1-3,7,8,10-12 All previous optical observations of Jovian lightning have been limited by camera sensitivity, proximity to Jupiter, and long exposures (~680 ms to 85 s) hence some measurements were likely superimposed flashes reported as one. 1,2,7,9,10,13 Here we report optical observations of lightning flashes by Juno's Stellar Reference Unit 14 with energies of ~10 5 -10 8 Joules, flash durations as short as 5.4 ms, and inter-flash separations of tens of milliseconds. The observations exposed Jovian flashes with typical terrestrial energies. The flash rate is ~6.1×10 -2 flashes/km 2 /yr, more than an order of magnitude greater than hitherto seen. Several flashes are of such small spatial extent they must originate above the 2 bar level, where there is no liquid water. 15,16 Juno's Stellar Reference Unit (SRU) captured images of Jovian lightning on the dark side of Jupiter from a unique perspective of as close as 53,000 km above the 1 bar level (30 km/pixel resolution). The SRU is a broadband (450 -1100 nm) imager designed to detect dim stars in support of spacecraft attitude determination. The camera's point spread function (PSF) spreads the optical signal of a point source over ~5 × 5 pixels, allowing unambiguous identification of small optical sources (see Extended Data Fig. 1). Fourteen lightning flashes (see Extended Data

The precision, accuracy, and potential sampling biases of temperature T and water vapor q vertical profiles obtained by satellite infrared sounding instruments are highly cloud-state dependent and poorly quantified. The authors describe progress toward a comprehensive T and q climatology derived from the Atmospheric Infrared Sounder (AIRS) suite that is a function of cloud state based on collocated CloudSat observations. The AIRS sampling rates, biases, and center root-mean-square differences (CRMSD) are determined through comparisons of pixel-scale collocated ECMWF model analysis data. The results show that AIRS provides a realistic representation of most meteorological regimes in most geographical regions, including those dominated by high thin cirrus and shallow boundary layer clouds. The mean AIRS observational biases relative to the ECMWF analysis between the surface and 200 hPa are within 61 K in T and from 21 to 10.5 g kg 21 in q. Biases because of cloud-state-dependent sampling dominate the total biases in the AIRS data and are largest in the presence of deep convective (DC) and nimbostratus (Ns) clouds. Systematic cold and dry biases are found throughout the free troposphere for DC and Ns. Somewhat larger biases are found over land and in the midlatitudes than over the oceans and in the tropics, respectively. Tropical and oceanic regions generally have a smaller CRMSD than the midlatitudes and over land, suggesting agreement of T and q variability between AIRS and ECMWF in these regions. The magnitude of CRMSD is also strongly dependent on cloud type.

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