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The Andes account for the largest source of orographic gravity waves (GWs) in the middle atmosphere. This results from persistent, strong zonal winds at the surface encountering the north‐south mountain chain, producing strong orographic lift, and resulting GWs. Here, we consider GWs in the stratosphere and mesosphere above the Andes as observed by the Cloud Imaging and Particle Size instrument, the Solar Occultation for Ice Experiment on the AIM satellite, and the Sounding of the Atmosphere using Broadband Emission Radiometry instrument onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite. GW variability is considered in the context of the location of the stratospheric wintertime westerly jet and planetary wave (PW) amplitude and phase. The occurrence of GWs in the middle and upper atmosphere depends not only on tropospheric sources, like the Andes, but also on the background winds through which they propagate. Results suggest that the propagation of GWs into the mesosphere is well correlated with winds throughout the middle and upper stratosphere. PWs cause the westerly jet to move over the Andes, resulting in an increase in GW amplitude throughout the middle and upper stratosphere. The evolution and variability of GWs are tied closely to the phase of the PW‐1 and are linked to PW‐2 when the PW amplitudes are sufficiently large. GW amplitude, as observed by all three data sets, increases in the upper stratosphere and lower mesosphere when the trough of the PW‐1 in the stratosphere is over the Andes. Plain Language Summary: In the Southern Hemisphere, strong wintertime winds continuously flow west to east at mid‐latitudes (40°–50°S). As these winds flow over surface features like the Andes Mountains, the air is forced upwards, creating waves in the atmosphere that propagate both horizontally and vertically. These gravity waves (GWs) transport energy from the surface to the upper atmosphere, where they break and deposit their momentum, causing either turbulent mixing, an acceleration of the winds, or the generation of additional waves. The energy deposited from GWs has a significant impact on the circulation in the upper atmosphere, so it is important to understand where they break and to characterize sources of variability. As GWs propagate vertically, they encounter horizontal wind shear associated with a band of strong winds in the middle atmosphere, causing them to turn toward the area of strong winds. The latitude where these strong winds occur can change significantly, driven by planetary‐scale waves. This work shows that the occurrence of GWs in the middle atmosphere, observed by several NASA instruments, strongly depends on the amplitude and orientation of the planetary scale waves and the resulting location of the middle atmospheric winds. Key Points: Gravity waves (GWs) at the stratopause show significant variability over the Andes associated with stratospheric winds and planetary wave (PW) phaseEnhanced GW activity follows the trough of the PW‐1 and strong stratospheric winds at mid‐southern latitudesGW activity is enhanced over the Andes when the PW trough and the polar night jet are over the Andes [ABSTRACT FROM AUTHOR]

Our solar system is filled with meteoric particles, or cosmic dust, which is either interplanetary or interstellar in origin. Interstellar dust (ISD) enters the heliosphere due to the relative motion of the sun and the interstellar flow. Interplanetary dust (IPD) comes primarily from asteroid collisions or comet sublimation, and comprises the bulk of material entering Earth's atmosphere. This study examines variations in ISD and the IPD flux at Earth using observations from three different satellite techniques. First are size-resolved in situ meteoroid detections by the Ulysses spacecraft, and second are in situ indirect dust observations by Wind. Third are measurements of meteoric smoke in the mesosphere by the Solar Occultation For Ice Experiment (SOFIE). Wind and Ulysses observations are sorted into the interstellar and interplanetary components. Wind ISD show the anticipated correlation to the 22-year solar magnetic cycle, and are consistent with model predictions of ISD. Because Wind does not discriminate particle size, the IPD measurements were interpreted using meteoric mass distributions from Ulysses observations and from different models. Wind observations during 2007–2020 indicate a total meteoric influx at Earth of 22 metric tons per day (t d−1), in reasonable agreement with long-term averages from SOFIE (25 t d−1) and Ulysses (32 t d−1). The SOFIE and Wind influx time series both show an unexpected correlation to the 22-year solar cycle. This relationship could be an artifact, or may indicate that IPD responds to changes in the solar magnetic field. [ABSTRACT FROM AUTHOR]

Measurements from the Solar Occultation For Ice Experiment (SOFIE) in both hemispheres are used to characterize meteoric smoke in the mesosphere and to estimate the meteoric flux into Earth's atmosphere. New smoke extinction retrievals from sunrise measurements in the Northern Hemisphere (NH) are presented, which complement the previously reported sunset observations in the Southern Hemisphere (SH). The sunrise observations are in good agreement with simulations from the Whole Atmosphere Community Climate Model (WACCM), for both the seasonal and height dependence of smoke in the mesosphere. The SOFIE‐WACCM comparisons assumed that smoke in the mesosphere exists purely as Fe‐rich olivine. This is justified because olivine is detected optically by SOFIE, meteoric ablation is predicted to inject similar quantities of the most abundant elements (Fe, Mg, and Si) into the mesosphere, and olivine is anticipated by theory and laboratory experiments. In addition, the ablated meteoric influx (AMI) and total meteoric influx determined from SOFIE assuming Fe‐rich olivine is in agreement with a recent and independent investigation based on models and observations. SOFIE observations from 2007 to 2021 indicate a global AMI of 7.3 ± 2.2 metric tons per day (t d−1), which corresponds to a total influx (ablated plus surviving material) of 24.7 ± 7.3 t d−1. Finally, the results indicate stronger descent in the NH polar winter mesosphere than in the SH winter. This hemispheric asymmetry at polar latitudes is indicated by smoke and water vapor results from both SOFIE and WACCM. Plain Language Summary: Satellite observations from the Solar Occultation For Ice Experiment (SOFIE) detect meteoric remnants in Earth's mesosphere. Known as meteoric smoke, these nanometer sized aerosols are made primarily of iron, silica, and magnesium. SOFIE smoke observations in the Southern and Northern polar regions during 2007 ‐ 2021 are in good agreement with simulations from the Whole Atmosphere Community Climate Model (WACCM). While SOFIE Indicates several smoke compositions, the present study suggests only Fe‐rich olivine. This is justified because (a) olivine is optically detected by SOFIE, (b) meteor ablation injects similar quantities of Fe, Mg and Si, and (c) olivine is anticipated by theory and laboratory experiments. Additionally, the meteoric influx determined from SOFIE assuming olivine agrees with a recent and independent investigation based on models and observations. SOFIE indicates a global ablated meteoric influx of 7 metric tons/day (25 tons/day total influx). SOFIE and WACCM show hemispheric asymmetries in smoke and water vapor that are consistent with stronger transport in the Northern winter mesosphere than in the South. SOFIE shows a larger smoke asymmetry than the model, however, and this unresolved issue might be related to a missing asymmetry in the current model description of meteoric influx or smoke physics Key Points: The composition of smoke in the mesosphere is consistent with iron‐rich olivineGlobal ablated meteoric influx is estimated to be 7.3 ± 2.2 metric tons/day, with a total influx of 24.7 ± 7.3 tons/dayHemispheric asymmetries in smoke and H2O are consistent with stronger winter descent in the Northern polar mesosphere relative to the South [ABSTRACT FROM AUTHOR]

Using an 8‐year (2007–2014) data set from two different limb‐viewing instruments, we evaluate the relative roles of vertically versus obliquely propagating gravity waves (GWs) as sources of GWs in the polar summer mesosphere. Obliquely propagating waves are of interest because they are presumed to be generated by the summer monsoons. In the high‐latitude upper mesosphere, the correlation coefficient between the time series of ice water content (IWC) and GW amplitude is 0.48, indicating that the observed GWs enhance polar mesospheric clouds (PMCs). For vertically propagating waves, the correlation coefficient between IWC and stratospheric/lower mesospheric (20–70 km) GW amplitude at the same high latitudes becomes more negative with increasing altitude. This change in correlation from negative in the lower mesosphere to positive at PMC altitudes suggests the presence of another source of GWs. The positive correlation coefficient between the time series of IWC and GW amplitude from 0–50°N, 20–90 km shows a slanted structure suggesting oblique propagation. This slanted structure is more robust in some seasons compared to others, and this interannual variability may be due to the latitudinal gradient of the mesospheric easterly jet where steeper gradients allow for low‐latitude tropospheric GWs to be refracted to the high‐latitude mesosphere more efficiently. Gravity‐Wave Regional or Global Ray Tracer (GROGRAT) ray tracing simulations show that more GWs propagate obliquely compared to vertically propagating waves that reach PMC altitudes. For obliquely propagating waves, GROGRAT simulations indicate that nonorographic tropospheric GWs with faster phase speed (>20 m/s) and longer horizontal wavelength (>400 km) have a higher probability of reaching the polar summer mesosphere. Key Points: Obliquely propagating gravity waves influence the polar summer mesosphereSteeper gradient of the mesospheric easterly jet allows for more efficient oblique propagation of gravity wavesLow‐latitude tropospheric gravity waves with faster phase speeds have a higher probability of reaching the polar summer mesosphere [ABSTRACT FROM AUTHOR]

The response of the polar mesosphere to the 11‐year solar cycle is investigated using satellite observations from 1979 to 2018. Solar maximum is expected to cause higher temperatures and lower water vapor in the upper mesosphere, thus reducing the amount of ice in polar mesospheric clouds (PMCs). While PMCs showed a clear anticorrelation with the solar cycle before roughly 2002, this response is absent during recent years. PMCs are controlled by temperature and water vapor, which were examined using mesospheric observations during 1992–2018. The main cause of the diminished solar cycle in PMCs near 68°S and 68°N appears to be a dramatic suppression of the solar cycle response of water vapor. The solar cycle response of temperature also decreases after 2002, but calculations show that the decreased H2O response had more than 3 times the impact on PMCs than the reduction in temperature response. Key Points: The response of PMCs to the 11‐year solar cycle was strong before ~2002 but is absent afterThe change in PMCs is mostly due to a suppression of the solar cycle response of water vaporThe solar cycle in temperature is reduced after ~2002 but has a secondary effect on PMCs [ABSTRACT FROM AUTHOR]

Abstract: The altitude‐ and latitude‐dependent responses of neutral temperature in the lower thermosphere to the 2013 St. Patrick's Day geomagnetic storm have been studied using neutral temperature measurements from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the TIMED satellite and the Solar Occultation For Ice Experiment (SOFIE) instrument onboard the AIM satellite. Both SABER and SOFIE observations revealed that both temperature increase (having peaks of ~15–25 K) and decrease (having peak of ~15 K), which were associated with the storm, occurred in the two hemispheres. The magnitudes of temperature variations changed with latitude, altitude, and the phase of the storm. The peaks of the temperature increase occurred 0.5–1.5 days later than the peak of the AE index, depending on latitude and height. Global circulation changes initiated due to heating and ion drag in the auroral region are likely responsible for the temperature increases or decreases in the lower thermosphere. [ABSTRACT FROM AUTHOR]

Abstract: The composition of meteoric smoke particles in the mesosphere is constrained using measurements from the Solar Occultation For Ice Experiment (SOFIE) in conjunction with models. Comparing the multiwavelength observations with models suggests smoke compositions of magnetite, wüstite, magnesiowüstite, or iron‐rich olivine. Smoke compositions of pure pyroxene, hematite, iron‐poor olivine, magnesium silicate, and silica are excluded, although this may be because these materials have weak signatures at the SOFIE wavelengths. Information concerning smoke composition allows the SOFIE extinction measurements to be converted to smoke volume density. Comparing the observed volume density with model results for varying meteoric influx (MI) provides constraints on the ablated fraction of incoming meteoric material. The results indicate a global ablated MI of 3.3 ± 1.9 t d−1, which represents only iron, magnesium, and possibly silica, given the smoke compositions indicated here. Considering the optics and iron content of individual smoke compositions gives an ablated Fe influx of 1.8 ± 0.9 t d−1. Finally, the global total meteoric influx (ablated plus surviving) is estimated to be 30 ± 18 t d−1, when considering the present results and a recent description of the speciation of meteoric material. [ABSTRACT FROM AUTHOR]