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Radio Occultation (RO) using the Global Navigation Satellite Systems (GNSS) can be used to infer atmospheric profiles of microwave refractivity in the Earth's atmosphere. GNSS RO data are now assimilated into numerical weather prediction models and used for climate monitoring. New remote sensing applications are being considered that fuse GNSS RO soundings and passive nadir-scanned radiance soundings. Collocating RO soundings and nadir-scanned radiance soundings, however, is computationally expensive, especially as new commercial GNSS RO constellations greatly increase the number of global daily RO soundings. This paper develops a new and efficient technique, called the "rotation-collocation-method", for collocating RO and nadir-scanned radiance soundings in which all soundings are rotated into the time-dependent reference frame in which the nadir sounder's scan pattern is stationary. Collocations with RO soundings are then found when the track of an RO sounding crosses the line corresponding to the nadir sounder's scan pattern. When applied to finding collocations between RO soundings from COSMIC-2, Metop-B-GRAS, and Metop-C-GRAS and the passive microwave soundings of ATMS on NOAA-20, Suomi-NPP, and AMSU-A on Metop-B and Metop-C for the month of January, 2021, the rotation- collocation method proves to be 99.0 % accurate and is hundreds to thousands of times faster than traditional approaches to finding collocations. [ABSTRACT FROM AUTHOR]

Radio scintillations in Pioneer Venus radio occultation data are simulated assuming that the index of refraction fluctuations in Venus's atmosphere responsible for the scintillations are directly caused by gravity wave fluctuations. The gravity waves are created by a global convection layer between 50- and 55-km altitude in Venus's atmosphere and propagate vertically. The authors compare the simulated scintillations with data from Pioneer Venus. These gravity waves can explain the spectral shape and amplitude of the radio scintillations. The shape at high frequencies is controlled by wave breaking, which yields a saturated spectrum. The amplitude is subject to parameters such as the intensity of the convection, the angle between the zonal winds and the beam path, and the zonal wind profile at polar latitudes. To match the observed amplitude of the scintillations, the velocity variations of the energy-bearing eddies in the convection must be at least 2 [ms.sup.-1]. This value is consistent with the Venus balloon results of Sagdeev et al. and is in the middle of the range considered by Leroy and Ingersoll in their study of convectively generated gravity waves. The latter study, combined with the lower bound on velocity from the present study, then yields lower bounds on the vertical fluxes of momentum and energy in the Venus atmosphere.

The emission of internal gravity waves from a layer of dry convection embedded within a stable atmosphere with static stability and zonal winds varying in height is calculated. This theory is applied to Venus to investigate whether these waves can help support the westward maximum of angular momentum of Venus's middle atmosphere. The emission mechanism is similar to that suggested for driving the gravity modes of the Sun and relates the amplitude and spectrum of the waves to the amplitude and spectrum of the convection. Waves are damped by several mechanisms: wavebreaking in the stable atmosphere, critical layer absorption, reabsorption by the convection, and wave radiation to space. The authors use plane parallel geometry without rotation and assume sinusoidal wave fluctuations in the horizontal dimensions. The vertical dependence is determined using the WKBJ approximation. It is found that convectively generated gravity waves do not exert an acceleration where the westward winds are greatest. Instead, they deposit westward momentum in a 1-km thick layer just above the convection. Other waves deposit eastward momentum far above the westward wind maximum where decelerations can exceed 20 m [s.sup.-1] [day.sup.-1], comparable to deceleration amplitudes in Earth's mesosphere. Although the momentum fluxes by gravity waves are substantial, the vertical profile of acceleration does not match what is required for supporting Venus's atmospheric superrotation.

We present observations defining (i) the frequency and depth of convective penetration of water into the stratosphere over the United States in summer using the Next-Generation Radar system; (ii) the altitude-dependent distribution of inorganic chlorine established in the same coordinate system as the radar observations; (iii) the high resolution temperature structure in the stratosphere over the United States in summer that resolves spatial and structural variability, including the impact of gravity waves; and (iv) the resulting amplification in the catalytic loss rates of ozone for the dominant halogen, hydrogen, and nitrogen catalytic cycles. The weather radar observations of ~2,000 storms, on average, each summer that reach the altitude of rapidly increasing available inorganic chlorine, coupled with observed temperatures, portend a risk of initiating rapid heterogeneous catalytic conversion of inorganic chlorine to free radical form on ubiquitous sulfate-water aerosols; this, in turn, engages the element of risk associated with ozone loss in the stratosphere over the central United States in summer based upon the same reaction network that reduces stratospheric ozone over the Arctic. The summertime development of the upper-level anticyclonic flow over the United States, driven by the North American Monsoon, provides a means of retaining convectively injected water, thereby extending the time for catalytic ozone loss over the Great Plains. Trusted decadal forecasts of UV dosage over the United States in summer require understanding the response of this dynamical and photochemical system to increased forcing of the climate by increasing levels of CO2 and CH4. [ABSTRACT FROM AUTHOR]

High‐resolution measurements from Global Navigation Satellite System (GNSS) radio occultation (RO) provide atmospheric profiles with independent information on altitude and pressure. This unique property is of crucial advantage when analyzing atmospheric characteristics that require joint knowledge of altitude and pressure or other thermodynamic atmospheric variables. Here we introduce and demonstrate the utility of this independent information from RO and discuss the computation, uncertainty, and use of RO atmospheric profiles on isohypsic coordinates—mean sea level altitude and geopotential height—as well as on thermodynamic coordinates (pressure and potential temperature). Using geopotential height as vertical grid, we give information on errors of RO‐derived temperature, pressure, and potential temperature profiles and provide an empirical error model which accounts for seasonal and latitudinal variations. The observational uncertainty of individual temperature/pressure/potential temperature profiles is about 0.7 K/0.15%/1.4 K in the tropopause region. It gradually increases into the stratosphere and decreases toward the lower troposphere. This decrease is due to the increasing influence of background information. The total climatological error of mean atmospheric fields is, in general, dominated by the systematic error component. We use sampling error‐corrected climatological fields to demonstrate the power of having different and accurate vertical coordinates available. As examples we analyze characteristics of the location of the tropopause for geopotential height, pressure, and potential temperature coordinates as well as seasonal variations of the midlatitude jet stream core. This highlights the broad applicability of RO and the utility of its versatile vertical geolocation for investigating the vertical structure of the troposphere and stratosphere.