G & A Technical Software (United States)

Abstract. In recent years, the need for high-quality long-term mesospheric ozone records has become increasingly evident, as they are essential for understanding chemical, dynamical, and radiative processes in the middle and upper atmosphere and their coupling with the lower layers. Here, we present a new merged dataset of ozone profiles in the mesosphere and lower thermosphere (METEOR-O₃), created from several limb-viewing satellite instruments: HALOE, GOMOS, MIPAS, ACE-FTS, MLS, and SOFIE. The dataset covers the period from 1991 to 2023 and provides deseasonalized ozone anomalies in 10° latitude bins between 80° S and 80° N, from approximately 22 km to 100 km. The deseasonalized ozone anomalies are used for global and seasonal trend analysis. The results show positive upper stratospheric ozone trends in both hemispheres, with magnitudes of 1–2 % per decade between 35 and 45 km, indicating continued ozone recovery consistent with previous assessments. In contrast, mesospheric ozone (above ~60 km) exhibits negative trends of 1–3 % per decade, with the strongest decreases of about 8–10 % per decade near the mesopause. Seasonal analyses confirm positive trends in the upper stratosphere across all seasons and persistent negative trends in the upper mesosphere, strongest at high latitudes above 80 km. The METEOR-O₃ dataset provides the first global, long-term merged record suitable for detailed studies of mesospheric/lower thermospheric ozone variability and trend evaluation, providing valuable information for model validation and assessments of upper atmospheric changes.

The Doppler Wind and Temperature Sounder (DWTS) is being developed for flight on NASA’s Dynamical Neutral Atmosphere-Ionosphere Coupling (DYNAMIC) satellite. DWTS will view the Earth limb orthogonal to the spacecraft ram and uses gas-filter correlation radiometry to detect the Doppler shift of atmospheric emission. The observations yield horizontal winds and kinetic temperature with high precision, excellent spatial resolution, and altitude coverage from 40–250 km. DWTS detects Doppler shifting of NO and 13CO2 atmospheric emission lines by passing the incident light through an onboard cell containing both gases that is cooled to near cryogenic temperatures. This work describes the DWTS instrument, and the results of a recent program completed to space qualify the gas cell. This effort integrated a flight-like gas cell into a prototype DWTS optical bench assembly (OBA) and subjected it to extended periods in thermal vacuum, repeated thermal cycling, and vibrational testing, all consistent with anticipated launch and flight conditions. Detailed observations of the DWTS gas cell indicate that it survived testing without compromise and justify a technology readiness level (TRL) of six.

Abstract A very high‐spatial resolution (∼21–23 m pixel at 85 km altitude) OH airglow imager at the Andes Lidar Observatory at Cerro Pachón, Chile observed considerable ducted wave activity on the night of 29–30 October 2016. This instrument was collocated with a Na wind‐temperature lidar that provided data revealing the occurrence of strong ducts. A large field of view OH and greenline airglow imager showed waves present over a vertical extent consistent with the altitudes of the ducting features identified in the lidar profiles. While waves that appeared to be ducted were seen in all imagers throughout the observation interval, the wave train seen in the OH images at earlier times had a distinct leading nonsinusoidal phase followed by several, lower‐amplitude, more sinusoidal phases, suggesting a likely bore. The leading phase exhibited significant dissipation via small‐scale secondary instabilities suggesting vortex rings that progressed rapidly to smaller scales and turbulence (the latter not fully resolved) thereafter. The motions of these small‐scale features were consistent with their location in the duct at or below ∼83–84 km. Bore dissipation caused a momentum flux divergence and a local acceleration of the mean flow within the duct along the direction of the initial bore propagation. A number of these features are consistent with mesospheric bores observed or modeled in previous studies.

Tube & knot (T&K) dynamics yield faster, more aggressive instability evolutions than axially uniform KHI in stratified shear environments.• T&K-induced twist waves drive the turbulent transition and preclude secondary CI/KHI that dominate prior laboratory and simulation studies.• T&K-induced turbulence yields faster/larger kinetic energy depletion and entropy production, producing more mixing with weaker efficiency.

The Atmospheric Waves Experiment (AWE) is a new NASA mission aimed at investigating the effects of tropospheric weather on space weather. An Advanced Mesospheric Temperature Mapper (AMTM) airglow imager will be deployed on the International Space Station (ISS) in December 2023. This proven instrument will map the nighttime mesospheric temperature at the altitude of the hydroxyl (OH) layer (~87 km) during two years, providing 2D gravity wave (GW) fields over a 600 km field-of-view, every second.Four state-of-the-art models will also help achieving the three science objectives:Quantify the seasonal and regional variabilities and influences of GWs near the mesopause, Identify the dominant dynamical processes controlling GWs observed near the mesopause, Estimate the wider role of GWs in the Ionosphere-Thermosphere-Mesosphere (ITM). This presentation will give an overview of the AWE mission and describe the future data levels using synthetic images.

<strong class="journal-contentHeaderColor">Abstract.</strong> Kelvin Helmholtz instability (KHI) is most likely to be the primary source for clear-air turbulence that is of importance in pollution transfer and diffusion and aircraft safety. It is exemplarily indicated by the critical value of Richardson (<em>Ri</em>) number, which is typically taken as 1/4. However, <em>Ri</em> is fairly sensitive to the vertical resolution of the dataset: a higher resolution systematically leads to a finer structure. The study aims to evaluate the performance of ERA5 reanalysis (137 model levels) in determining KHI spatial-temporal variabilities, by comparing it against a near-global high-resolution (10-m) radiosonde dataset during years 2017 to 2022, and to further highlight the global climatology and dynamical environment of KHIs. Overall, the occurrence frequency of <em>Ri </em>&lt; 1/4 in the free atmosphere is inevitably underestimated by the ERA5 reanalysis over all climate zones, compared to radiosonde, due largely to the severe underestimation in wind shears. Otherwise, the occurrence frequency of KHI indicated by <em>Ri </em>&lt; 1 in ERA5 is climatologically consistent with that from radiosondes in the free troposphere, especially over the midlatitude and subtropics in the Northern/Southern Hemisphere. Therefore, we infer that the threshold value of <em>Ri</em> should be approximated as 1, rather than 1/4, when using ERA5 for the KHI estimation. KHI occurrence frequencies revealed by both datasets exhibit significant seasonal cycles over polar, midlatitude, and subtropics regions, and they are consistently strong at heights of 10&ndash;15 km in the tropic region. In addition, the frequency at low-levels is positively correlated with the standard derivation of orography, and it is exceptionally strong over the Ni&ntilde;o 3 region at heights of 6&ndash;13 km. Furthermore, the dynamical environment of KHI favors strong wind shears probably induced by the mean flows and the propagation of orographic or non-orographic gravity waves.

Abstract Gravity waves (GWs) and their associated multi-scale dynamics are known to play fundamental roles in energy and momentum transport and deposition processes throughout the atmosphere. GWs are well described by the Navier-Stokes equations, but solving these equations extending to very small scales remains daunting, and is limited by the computational costs of resolving the smallest important spatio-temporal features in a large-scale environment. This has led to developments of a wide variety of GW parameterization schemes for regional and global atmospheric models. Traditionally, GW parameterizations are based on linear theory, and no parameterization of secondary GWs (SGWs) has been developed to date. In addition, there remain many aspects of GW dynamics (e.g., GW self-acceleration, instability, GW breaking, SGW generation, and multi-scale interactions) that are important to describe, but cannot be addressed by linear theory or existing schemes. Here we describe an initial, two-dimensional (2-D), machine learning model – the Compressible Atmosphere Model Neural Network (CAMNet) - intended as a first step toward a more general, three-dimensional, highly-efficient, model for applications to nonlinear GW dynamics description. CAMNet employs a physics-informed neural operator and GPU hardware to dramatically accelerate GW and SGW simulations applied to two GW sources to date. CAMNet is trained on high-resolution simulations by the state-of-the-art model Complex Geometry Compressible Atmosphere Model (CGCAM). Two initial applications to a Kelvin-Helmholtz instability source and mountain wave generation, propagation, breaking, and SGW generation in two wind environments are described here. Results show that CAMNet can capture the key 2-D dynamics modeled by CGCAM with high precision. Spectral characteristics of primary and SGWs estimated by CAMNet agree well with those from CGCAM. Our results show that CAMNet can achieve a several order-of-magnitude acceleration relative to CGCAM without sacrificing accuracy and suggests a potential for machine learning to enable efficient and accurate descriptions of primary and secondary GWs in global atmospheric models.

The Balloon Lidar Experiment (BOLIDE) which was part of the PMC Turbo balloon mission has captured near-vertical profiles of polar mesospheric clouds (PMC) during a 6-day flight along the Arctic circle in July 2018. The high-resolution soundings (20 m vertical and 10 s temporal resolution) reveal highly structured layers with large gradients in volume backscatter coefficient. We systematically screen the BOLIDE dataset for small-scale variability by assessing these gradients at high resolution. We find longer tails of the probability density distributions of these gradients compared to a normal distribution, indicating intermittent behaviour. The high occurrence rate of large gradients is assessed in relation to the 15-min-averaged layer brightness and the spectral power of short-period (5–62 min) gravity waves based on PMC layer altitude variations. We find that variability on small scales occurs during weak, moderate and strong gravity wave activity. Layers with below-average brightness are less likely to show small-scale variability in conditions of strong gravity wave activity. We present and discuss signatures of this small-scale variability and possibly related dynamical processes, and identify potential cases for future case studies and modelling efforts.

The first Doppler Wind and Temperature Sensor (DWTS) using the Doppler Scanning with a Gas Filter (DSGF) measurement technique has been constructed. It is now ready for performance testing in a Virginia Tech Laboratory. The DSGF approach promises extraordinary signal-to-noise and spatial resolution by simultaneously modulating the emission from an entire spectral band. The modulation is measured over typically 100 seconds without affecting spatial resolution. The port or starboard measurement resolution is characteristic of an Earth limb imager: 2km in the vertical (potentially continuous from 20 to 250 km), 10 km along-track and 150 km in the observed limb direction.

Abstract Kjellstrand et al. (2022), https://10.1029/2021JD036232 describes the evolution and dynamics of a strong, large‐scale Kelvin‐Helmholtz instability (KHI) event observed in polar mesospheric clouds (PMCs) on 12 July 2018 by high‐resolution imagers aboard the PMC Turbulence (PMC Turbo) stratospheric long‐duration balloon experiment. The imaging provides evidence of KH billow interactions and instabilities that are strongly influenced by gravity waves at larger scales. Specific features include initially separated regions of KHI, secondary convective and KH instabilities of individual billows, and “tubes” and “knots” that arise where billow cores are mis‐aligned or discontinuous along their axes. This study describes a direct numerical simulation of KH billow interactions in a periodic domain seeded with random initial noise that enables excitation of multiple KH billows exhibiting variable phase structures that capture multiple features of the observed KHI dynamics. Variable KH billow phases along their axes yield initial vortex tubes having diagonal alignments that link adjacent, but mis‐aligned, billow cores. Weak initial vortex tubes and billow cores having nearly orthogonal alignments amplify, interact strongly, and drive intense vortex knots at these sites. These vortex tube and knot (T&amp;K) dynamics excite “twist waves” that unravel the initial vortex tubes, and drive increasingly strong vortex interactions and a cascade of energy and enstrophy to successively smaller scales in the turbulence inertial range. The implications of T&amp;K dynamics are much more rapid and intense breakdown and decay of the KH billows, and significantly enhanced energy dissipation rates, where these interactions occur.