Mesosphere-Lower-Thermosphere Neutral Density Measurements from Low-cost COTS Accelerometers and Ionization Gauge

Measurements of aerodynamic drag on objects can be used to determine the density of the medium provided other variables are known. The Space and Atmospheric Instrumentation Laboratory launched a midlatitude sounding rocket named SpEED Demon from Wallops Flight Facility in August 2022. Among the instruments onboard were sensitive low-cost MEMS accelerometers allowing for neutral density measurements through the drag technique up to 100km in altitude. In addition to sensitive accelerometers on the main payload, four ejectable subpayloads also carry an accelerometer providing simultaneous multi-point neutral density measurements, akin to a ‘falling cylinder’ experiment. We present the flight performance and results of this drag-based density measurement technique from the SpEED Demon launch. Drag-derived density results are compared with density measurements from an ionization gauge instrument and the MSIS atmospheric model to provide validation of the technique, showing agreement within 10% in the 80-100km altitude range

On the Short-Term Variability of Turbulence and Temperature in the Winter Mesosphere

Four mesosphere–lower thermosphere temperature and turbulence profiles were obtained in situ within ∼30 min and over an area of about 100 by 100 km during a sounding rocket experiment conducted on 26 January 2015 at Poker Flat Research Range in Alaska. In this paper we examine the spatial and temporal variability of mesospheric turbulence in relationship to the static stability of the background atmosphere. Using active payload attitude control, neutral density fluctuations, a tracer for turbulence, were observed with very little interference from the payload spin motion, and with high precision (%) at sub-meter resolution. The large-scale vertical temperature structure was very consistent between the four soundings. The mesosphere was almost isothermal, which means more stratified, between 60 and 80 km, and again between 88 and 95 km. The stratified regions adjoined quasi-adiabatic regions assumed to be well mixed. Additional evidence of vertical transport and convective activity comes from sodium densities and trimethyl aluminum trail development, respectively, which were both observed simultaneously with the in situ measurements. We found considerable kilometer-scale temperature variability with amplitudes of 20 K in the stratified region below 80 km. Several thin turbulent layers were embedded in this region, differing in width and altitude for each profile. Energy dissipation rates varied between 0.1 and 10 mW kg−1, which is typical for the winter mesosphere. Very little turbulence was observed above 82 km, consistent with very weak small-scale gravity wave activity in the upper mesosphere during the launch night. On the other hand, above the cold and prominent mesopause at 102 km, large temperature excursions of +40 to +70 K were observed. Simultaneous wind measurements revealed extreme wind shears near 108 km, and combined with the observed temperature gradient, isolated regions of unstable Richardson numbers (0Kp∼5)

Gravity Wave Ducting Observed in the Mesosphere Over Jicamarca, Peru

Short-period gravity waves are ubiquitous in the mesosphere, but the vertical structures of their perturbations are difficult to observe. The Jicamarca 50-MHz very high frequency radar allows observations of winds and turbulent scatter with high temporal and vertical resolution. We present a case of a quasi-monochromatic gravity wave with period 520 (±40) s that is likely ducted below a southward wind jet between 68 and 74 km. Above this layer of evanescence, a northward wind enables it to emerge into a more stable layer, where it is refracted to a short vertical wavelength of 2.2 (±0.2) km; data show evidence of weak nonlinearity, and possible overturning or partial reflection from higher altitudes, above the observable region, in the form of a standing wave structure in vertical velocity at approximately 75 km. Based on the dispersion relation, and with help of a two-dimensional model, we determine that most likely the wave is propagating northward and is being ducted below and tunneling through the regions of evanescence created by the wind flow and typical mesospheric thermal structure. This is the first time that such an event has been identified in the Jicamarca mesospheric echoes, and it is distinct from Kelvin-Helmholtz billows also commonly seen with this sensitive radar—instead apparently revealing tunneling of the gravity wave through ambient winds

Observations of Reduced Turbulence and Wave Activity in the Arctic Middle Atmosphere Following the January 2015 Sudden Stratospheric Warming

Measurements of turbulence and waves were made as part of the Mesosphere-Lower Thermosphere Turbulence Experiment (MTeX) on the night of 25–26 January 2015 at Poker Flat Research Range, Chatanika, Alaska (65°N, 147°W). Rocket-borne ionization gauge measurements revealed turbulence in the 70- to 88-km altitude region with energy dissipation rates between 0.1 and 24 mW/kg with an average value of 2.6 mW/kg. The eddy diffusion coefficient varied between 0.3 and 134 m2/s with an average value of 10 m2/s. Turbulence was detected around mesospheric inversion layers (MILs) in both the topside and bottomside of the MILs. These low levels of turbulence were measured after a minor sudden stratospheric warming when the circulation continued to be disturbed by planetary waves and winds remained weak in the stratosphere and mesosphere. Ground-based lidar measurements characterized the ensemble of inertia-gravity waves and monochromatic gravity waves. The ensemble of inertia-gravity waves had a specific potential energy of 0.8 J/kg over the 40- to 50-km altitude region, one of the lowest values recorded at Chatanika. The turbulence measurements coincided with the overturning of a 2.5-hr monochromatic gravity wave in a depth of 3 km at 85 km. The energy dissipation rates were estimated to be 3 mW/kg for the ensemble of waves and 18 mW/kg for the monochromatic wave. The MTeX observations reveal low levels of turbulence associated with low levels of gravity wave activity. In the light of other Arctic observations and model studies, these observations suggest that there may be reduced turbulence during disturbed winters

Observations of Reduced Turbulence and Wave Activity in the Arctic Middle Atmosphere Following the January 2015 Sudden Stratospheric Warming

Measurements of turbulence and waves were made as part of the Mesosphere-Lower Thermosphere Turbulence Experiment (MTeX) on the night of 25–26 January 2015 at Poker Flat Research Range, Chatanika, Alaska (65°N, 147°W). Rocket-borne ionization gauge measurements revealed turbulence in the 70- to 88-km altitude region with energy dissipation rates between 0.1 and 24 mW/kg with an average value of 2.6 mW/kg. The eddy diffusion coefficient varied between 0.3 and 134 m2/s with an average value of 10 m2/s. Turbulence was detected around mesospheric inversion layers (MILs) in both the topside and bottomside of the MILs. These low levels of turbulence were measured after a minor sudden stratospheric warming when the circulation continued to be disturbed by planetary waves and winds remained weak in the stratosphere and mesosphere. Ground-based lidar measurements characterized the ensemble of inertia-gravity waves and monochromatic gravity waves. The ensemble of inertia-gravity waves had a specific potential energy of 0.8 J/kg over the 40- to 50-km altitude region, one of the lowest values recorded at Chatanika. The turbulence measurements coincided with the overturning of a 2.5-hr monochromatic gravity wave in a depth of 3 km at 85 km. The energy dissipation rates were estimated to be 3 mW/kg for the ensemble of waves and 18 mW/kg for the monochromatic wave. The MTeX observations reveal low levels of turbulence associated with low levels of gravity wave activity. In the light of other Arctic observations and model studies, these observations suggest that there may be reduced turbulence during disturbed winters

On the Short-Term Variability of Turbulence and Temperature in the Winter Mesosphere

Four mesosphere–lower thermosphere temperature and turbulence profiles were obtained in situ within ∼30 min and over an area of about 100 by 100 km during a sounding rocket experiment conducted on 26 January 2015 at Poker Flat Research Range in Alaska. In this paper we examine the spatial and temporal variability of mesospheric turbulence in relationship to the static stability of the background atmosphere. Using active payload attitude control, neutral density fluctuations, a tracer for turbulence, were observed with very little interference from the payload spin motion, and with high precision (%) at sub-meter resolution. The large-scale vertical temperature structure was very consistent between the four soundings. The mesosphere was almost isothermal, which means more stratified, between 60 and 80 km, and again between 88 and 95 km. The stratified regions adjoined quasi-adiabatic regions assumed to be well mixed. Additional evidence of vertical transport and convective activity comes from sodium densities and trimethyl aluminum trail development, respectively, which were both observed simultaneously with the in situ measurements. We found considerable kilometer-scale temperature variability with amplitudes of 20 K in the stratified region below 80 km. Several thin turbulent layers were embedded in this region, differing in width and altitude for each profile. Energy dissipation rates varied between 0.1 and 10 mW kg−1, which is typical for the winter mesosphere. Very little turbulence was observed above 82 km, consistent with very weak small-scale gravity wave activity in the upper mesosphere during the launch night. On the other hand, above the cold and prominent mesopause at 102 km, large temperature excursions of +40 to +70 K were observed. Simultaneous wind measurements revealed extreme wind shears near 108 km, and combined with the observed temperature gradient, isolated regions of unstable Richardson numbers (0Kp∼5)

Gravity Wave Ducting Observed in the Mesosphere Over Jicamarca, Peru

Short-period gravity waves are ubiquitous in the mesosphere, but the vertical structures of their perturbations are difficult to observe. The Jicamarca 50-MHz very high frequency radar allows observations of winds and turbulent scatter with high temporal and vertical resolution. We present a case of a quasi-monochromatic gravity wave with period 520 (±40) s that is likely ducted below a southward wind jet between 68 and 74 km. Above this layer of evanescence, a northward wind enables it to emerge into a more stable layer, where it is refracted to a short vertical wavelength of 2.2 (±0.2) km; data show evidence of weak nonlinearity, and possible overturning or partial reflection from higher altitudes, above the observable region, in the form of a standing wave structure in vertical velocity at approximately 75 km. Based on the dispersion relation, and with help of a two-dimensional model, we determine that most likely the wave is propagating northward and is being ducted below and tunneling through the regions of evanescence created by the wind flow and typical mesospheric thermal structure. This is the first time that such an event has been identified in the Jicamarca mesospheric echoes, and it is distinct from Kelvin-Helmholtz billows also commonly seen with this sensitive radar—instead apparently revealing tunneling of the gravity wave through ambient winds

Vortex: A New Rocketexperiment to Studymesoscale Dynamics at the Turbopause

The goal of this new investigation is to better understand gravity waves and their interactions as they propagate from the mesosphere into the lower thermosphere, to characterize the mesoscale wind field, and to identify regions of divergence, vorticity, and stratified turbulence. The Vorticity Experiment (VortEx) will comprise two salvoes of each two sounding rockets scheduled to be launched from Andøya Space Center, Norway in February 2022. The rockets will observe horizontally spaced wind profiles, neutral density and temperature profiles, and plasma densities. Additional information about the background conditions and mesoscale dynamics will be obtained by lidars, meteor radars and a hydroxyl temperature mapper. The observational data will be combined with numerical modeling for a comprehensive look at gravity wave propagation, instability and turbulence generation

Vortex: A New Rocketexperiment to Studymesoscale Dynamics at the Turbopause

The goal of this new investigation is to better understand gravity waves and their interactions as they propagate from the mesosphere into the lower thermosphere, to characterize the mesoscale wind field, and to identify regions of divergence, vorticity, and stratified turbulence. The Vorticity Experiment (VortEx) will comprise two salvoes of each two sounding rockets scheduled to be launched from Andøya Space Center, Norway in February 2022. The rockets will observe horizontally spaced wind profiles, neutral density and temperature profiles, and plasma densities. Additional information about the background conditions and mesoscale dynamics will be obtained by lidars, meteor radars and a hydroxyl temperature mapper. The observational data will be combined with numerical modeling for a comprehensive look at gravity wave propagation, instability and turbulence generation