A new Cloud Imaging and Particle Size (CIPS) gravity wave (GW) variance data set is available that facilitates automated analysis of GWs entering the mesosphere. This work examines several years of CIPS GW variances from 50 to 55 km in the context of the Arctic and Antarctic polar vortices. CIPS observes highest GW activity in the vortex edge region where horizontal wind speeds are largest, consistent with previously published GW climatologies in the stratosphere and mesosphere. CIPS observes the well‐documented planetary wave (PW)‐1 patterns in GW activity in both hemispheres. In the Northern Hemisphere, maximum GW activity occurs over the North Atlantic and western Europe. In the Southern Hemisphere, maximum GW activity stretches from the Andes over the South Atlantic and Indian Oceans, as expected. In the NH, CIPS GW spatial patterns are highly correlated with horizontal wind speed. In the SH, CIPS GW patterns are less positively correlated with the winds due to increased zonal symmetry and orographic forcing. The Andes Mountains and Antarctic Peninsula, South Georgia Island, Kerguelen/Heard Islands, New Zealand, and Tasmania are persistent sources of orographic GWs. Atmospheric Infrared sounder observations of stratospheric GWs are analyzed alongside CIPS to explore vertical GW coherence and to infer GW propagation and sources. NH midlatitude GW activity is reduced during the January 2021 SSW, as expected. This reduction in GWs leads to a simultaneous reduction in traveling ionospheric disturbances (TIDs), providing more evidence that weak polar vortex events with weak GW activity leads to reduced daytime TID activity.
The energetic particle precipitation (EPP) indirect effect (IE) refers to the downward transport of reactive odd nitrogen (NOx = NO + NO2) produced by EPP (EPP‐NOx) from the polar winter mesosphere and lower thermosphere to the stratosphere where it can destroy ozone. Previous studies of the EPP IE examined NOxdescent averaged over the polar region, but the work presented here considers longitudinal variations. We report that the January 2009 split Arctic vortex in the stratosphere left an imprint on the distribution of NO near the mesopause, and that the magnitude of EPP‐NOxdescent in the upper mesosphere depends strongly on the planetary wave (PW) phase. We focus on an 11‐day case study in late January immediately following the 2009 sudden stratospheric warming during which regional‐scale Lagrangian coherent structures (LCSs) formed atop the strengthening mesospheric vortex. The LCSs emerged over the north Atlantic in the vicinity of the trough of a 10‐day westward traveling planetary wave. Over the next week, the LCSs acted to confine NO‐rich air to polar latitudes, effectively prolonging its lifetime as it descended into the top of the polar vortex. Both a whole atmosphere data assimilation model and satellite observations show that the PW trough remained coincident in space and time with the NO‐rich air as both migrated westward over the Canadian Arctic. Estimates of descent rates indicate five times stronger descent inside the PW trough compared to other longitudes. This case serves to set the stage for future climatological analysis of NO transport via LCSs.
more » « less- NSF-PAR ID:
- 10374604
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Atmospheres
- Volume:
- 126
- Issue:
- 11
- ISSN:
- 2169-897X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract -
more » « less
Abstract It is well known that stratospheric sudden warmings (SSWs) are a result of the interaction between planetary waves (PWs) and the stratospheric polar vortex. SSWs occur when breaking PWs slow down or even reverse this zonal wind jet and induce a sinking motion that adiabatically warms the stratosphere and lowers the stratopause. In this paper we characterize this downward progression of stratospheric temperature anomalies using 18 years (2003–2020) of Sounding of the Atmosphere using Broadband Radiometry (SABER) observations. SABER temperatures, derived zonal winds, PW activity and gravity wave (GW) activity during January and February of each year indicate a high‐degree of year‐to‐year variability. From 11 stratospheric warming events (9 major and 2 minor events), the descent rate of the stratopause altitude varies from 0.5 to 2 km/day and the lowest altitude the stratopause descends to varies from <20 to ∼50 km (i.e., no descent). A composite analysis of temperature and squared GW amplitude anomalies indicate that the downward descent of temperature anomalies from 50 to ∼25 km lags the downward progression of increased GW activity. This increased GW activity coincides with the weakening and reversal of the westward zonal winds in agreement with previous studies. Our study suggests that although PWs drive the onset of SSWs at 30 km, GWs also play a role in contributing to the descent of temperature anomalies from the stratopause to the middle and lower stratosphere.
-
more » « less
Abstract This paper investigates the lower‐to‐upper atmosphere coupling at high latitudes (>60°N) during the northern winter months of 2012–2013 years, which includes a period of major Sudden “Stratospheric” Warming (SSW). We perform statistical analysis of thermosphere wind disturbances with periods of 30–70 min, known as the medium scale traveling atmospheric disturbances (MSTADs) in atomic oxygen green line (557.7 nm) near ∼120 km and red line (630.0 nm) emissions near ∼250 km observed from Scanning Doppler Imagers (SDIs) over Alaska. The SDI MSTADs observations (60°–75°N) are interpreted in conjunction with the previous daytime medium‐scale traveling ionospheric disturbance (MSTID) observations by SuperDARN midlatitudes (35°–65°N) radars in the
F ‐region ionosphere and western hemisphere, which confirm findings from the SDI instruments. Increases in MSTAD activity from SDIs show correlations with the increasing meridional planetary wave (PW) amplitudes in the stratosphere derived from MERRA2 winds. Furthermore, a detailed study of the lower atmospheric conditions from MERRA2 winds indicates that the lower atmospheric sources of MSTADs are likely due to the stratospheric generated Gravity Waves (GWs) and not orographic GWs. Favorable stratospheric propagation conditions and polar vortex disturbances resulting from the increased PW activity in the stratospheric region both appear to contribute to increased MSTAD activity in the thermosphere. Additionally, the results show that the MSTID activity from SuperDARN HF radars at mid latitudes during the January 2013 SSW is lower than the MSTAD activity in SDI winds at high latitudes. -
more » « less
Abstract Eastward‐propagating planetary waves (EPWs) were investigated prior to the boreal January 2009 major sudden stratospheric warming (SSW) event simulated by the National Center for Atmospheric Research's Whole Atmosphere Community Climate Model with specified dynamics. About 22 days before SSW onset, a background flow with jet maxima around the upper polar stratosphere and subtropical mesosphere developed due to the net forcing by gravity and planetary waves. The mesospheric wind structure was largely unstable and supported a wave geometry conducive to overreflection. With a zonal phase speed of ∼10 m s−1, EPWs appeared near their turning and critical layers as wavenumber‐2 perturbations in the stratosphere and mesosphere. Accompanied by upward EPW activity from the lower stratosphere, EPW growth exhibited characteristics of wave instability and overreflection.
-
more » « less
Abstract The Hunga Tonga Hunga‐Ha'apai (HTHH) volcanic eruption on 15 January 2022 injected water vapor and SO2into the stratosphere. Several months after the eruption, significantly stronger westerlies, and a weaker Brewer‐Dobson circulation developed in the stratosphere of the Southern Hemisphere and were accompanied by unprecedented temperature anomalies in the stratosphere and mesosphere. In August 2022, the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite instrument observed record‐breaking temperature anomalies in the stratosphere and mesosphere that alternate signs with altitude. Ensemble simulations carried out with the Whole Atmosphere Community Climate Model (WACCM6) indicate that the strengthening of the stratospheric westerlies explains the mesospheric temperature changes. The stronger westerlies cause stronger westward gravity wave drag in the mesosphere. Although the enhanced gravity wave drag is partly balanced by a weakening of planetary wave forcing, the net result is an acceleration of the mesospheric mean meridional circulation. The stronger mesospheric circulation, in turn, plays a dominant role in driving the changes in mesospheric temperatures. This study highlights the impact of large volcanic eruptions on middle atmospheric dynamics and provides insight into their long‐term effects in the mesosphere. On the other hand, we could not discern a clear mechanism for the observed changes in stratospheric circulation. In fact, an examination of the WACCM ensemble reveals that not every member reproduces the large changes observed by SABER. We conclude that there is a stochastic component to the stratospheric response to the HTHH eruption.
