Water and ammonia vapors are known to be the major sources of spectral absorption at pressure levels observed by the microwave radiometer (MWR) on Juno. However, the brightness temperatures and limb darkening observed by the MWR at its longest-wavelength channel of 50 cm (600 MHz) in the first nine perijove passes indicate the existence of an additional source of opacity in the deep atmosphere of Jupiter (pressures beyond 100 bar). The absorption properties of ammonia and water vapor, and their relative abundances in Jupiter’s atmosphere, do not provide sufficient opacity in the deep atmosphere to explain the 600 MHz channel observation. Here we show that free electrons due to the ionization of alkali metals, i.e., sodium and potassium, with subsolar metallicity, [M/H] (log-based 10 relative concentration to solar) in the range of [M/H] = −2 to [M/H] = −5, can provide the missing source of opacity in the deep atmosphere. If the alkali metals are not the source of additional opacity in the MWR data, then their metallicity at 1000 bars can only be even lower. This upper bound of −2 on the metallicity of the alkali metals contrasts with the other heavy elements—C, N, S, Ar, Kr, and Xe—that are all enriched relative to their solar abundances, having a metallicity of approximately +0.5.

Jupiter's polar aurora exhibits low brightness temperatures in Juno Microwave Radiometer (MWR) observations when the Juno spacecraft passes over the high‐latitude region of the Northern Hemisphere. These cold features are observed predominantly at 0.6 GHz and show both long‐term hours and short‐term changes over time, that is, spans less than the 30‐s spacecraft spin period. The MWR “cold spot” observations are associated with polar ultraviolet emission features that are thought to originate from high energy electron precipitation into the Jovian high latitude atmosphere. The energetic electron precipitation produces strong absorptive characteristics at microwave frequencies due to the transient formation of high‐density electron regions in the lower stratosphere. In this paper, we describe progress on the analysis of Juno MWR observations of the northern aurora and simulate the effects of heating and electron impact ionization processes due to high energy particle precipitation events in Jupiter's auroral ionosphere. Electron precipitation intensities at energies up to 10 MeV inferred from the Jupiter Energetic‐Particle Detector Instrument (JEDI) and Ultraviolet Spectrograph (UVS) instruments are used as a Northern Hemisphere case study to understand the energy deposition and ionization processes in the lower stratosphere, and subsequently used to estimate the microwave and ultraviolet opacity of the auroral region. The northward progression of Juno's perijove during the mission reduces the overflight altitude and allows important insights into effects produced at different length scales with respect to the auroral oval.

We present radiative transfer analyses of IRTF-TEXES and SOFIA-EXES mid-infrared spectra of Jupiter's mid- to high latitudes recorded between 2019 April 16 and 2023 July 20. The spectra were inverted across a photochemical model grid of varying eddy diffusion coefficient profiles, and the quality of fit of the synthetic spectra to the observed was used to constrain the CH₄ homopause level. For a subset of latitudes/dates, we find that the CH₄ homopause level is elevated in the region enclosed inside of, or magnetospherically poleward of, the northern ultraviolet main auroral emissions (MAEs) in comparison to the region outside or equatorward of the MAE. For example, using SOFIA-EXES results on 2021 June 10, we derived a CH₄ homopause level of log(p _H(nbar)) = 1.54 − 0.69 + 0.51 or z _H = 453 − 76 + 128 km above 1 bar poleward of the northern MAE at 68^∘N compared to a lower limit of log(p _H) > 2.43 and upper limit of z _H < 322 km derived equatorward of the northern MAE. We therefore conclude that the region poleward of the northern MAE is, at times, subject to enhanced vertical transport resulting from auroral energy deposition. The exact mechanisms responsible for the enhanced vertical transport in Jupiter's auroral regions are uncertain: time-dependent circulation modeling of Jupiter's polar atmosphere is required to better understand this phenomenon. Poleward of the southern MAE, derived homopause levels agreed within uncertainty with those at equatorward locations. However, we consider this result a spatial sampling artifact rather than concluding that the southern auroral region is not subject to enhanced vertical transport.

Airborne dust plays an active role in determining the thermal structure and chemical composition of the present-day atmosphere of Mars and possibly the planet’s climate evolution over time through radiative–convective and cloud microphysics processes. Thus, accurate measurements of the distribution and variability of dust are required. Observations from the Mars Global Surveyor/Thermal Emission Spectrometer Mars Mars Reconnaissance Orbiter/Mars Climate Sounder and Mars Express/Fourier Transform Spectrometer and the Curiosity Rover have limited capability to measure dust. We show that spacecraft occultation of the Martian atmosphere at far-infrared frequencies between 1 and 10 THz can provide the needed global and temporal data on atmospheric dust by providing co-located measurements of temperature and dust opacity from the top of the atmosphere all the way down to the surface. In addition, spacecraft occultation by a small-satellite constellation could provide global measurements of the development of dust storms.

The Laurentian Great Lakes exhibit variations in lake water surface temperature and ice coverage on the time scale of days to weeks during the winter months. The hydrodynamics and thermodynamics of these freshwater lakes influence the cloud formation and snow deposition in downwind regions. Lake-effect snowfall forecasts are sensitive to the evolving water temperature and ice conditions, yet the dynamic evolution of lake conditions is not commonly considered for short-range forecasting models. We implement an asynchronous, one-way coupling that supplies hourly lake surface temperature, ice fraction, ice thickness, and ice-surface temperature from NOAA’s Great Lakes Operational Forecast System (GLOFS), based on the model FVCOM-CICE, to NOAA’s Unified Forecast System (UFS). UFS’ coupling infrastructure uses the Earth System Modeling Framework (ESMF) which we enhance with an “inline” functionality for ESMF’s Community Data Models for Earth Prediction Systems (CDEPS). The lake coupling is evaluated in a 3 km UFS Short-Range Weather (SRW) configuration that resembles the near-operational Rapid Refresh Forecast System version 1 (RRFSv1). To demonstrate the lake coupling capabilities we run 60-hour hindcast experiments for five lake-effect snow events from December 2022 to January 2026 using either hourly evolving or static, initial-time lake conditions. The predicted snow water equivalent is evaluated against observational data products over regions downwind of each lake. Dynamic lake conditions influence the surface heat fluxes, and impact of snowfall is shown to vary by lake and snowfall accumulation. These results demonstrate a computationally practical pathway for incorporating time-evolving Great Lakes conditions into the UFS-SRW/RRFSv1 for short-range forecasts.

Water and ammonia vapors are known to be the major sources of spectral absorption at pressure levels observed by the microwave radiometer (MWR) on Juno. However, the brightness temperatures and limb darkening observed by the MWR at its longest wavelength channel of 50 cm (600 MHz) in the first 9 perijove passes indicate the existence of an additional source of opacity in the deep atmosphere of Jupiter (pressures beyond 100 bar). The absorption properties of ammonia and water vapor, and their relative abundances in Jupiter's atmosphere do not provide sufficient opacity in deep atmosphere to explain the 600 MHz channel observation. Here we show that free electrons due to the ionization of alkali metals, i.e. sodium, and potassium, with sub-solar metallicity [M/H] (log based 10 relative concentration to solar) in the range of [M/H] = -2 to [M/H] = -5 can provide the missing source of opacity in the deep atmosphere. If the alkali metals are not the source of additional opacity in the MWR data, then their metallicity at 1000 bars can only be even lower. The upper bound of -2 on the metallicity of the alkali metals contrasts with the other heavy elements -- C, N, S, Ar, Kr, and Xe -- which are all enriched relative to their solar abundances having a metallicity of approximately +0.5.