The quasi‐2 day wave activities during 2007 boreal summer period as revealed by Whole Atmosphere Community Climate Model

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The temperature and wind data sets from the ensemble data assimilation version of the Whole Atmosphere Community Climate Model + Data Assimilation Research Testbed (WACCM + DART) developed at the National Center for Atmospheric Research (NCAR) are utilized to study the seasonal variability of the eastward quasi 2 day wave (QTDW) with zonal wave number 2 (E2) during 2007. The aliasing ratio of E2 from wave number 3 (W3) in the synoptic WACCM data set is a constant value of 4 × 10−6% due to its uniform sampling pattern, whereas the aliasing is latitudinally dependent if the WACCM fields are sampled asynoptically based on the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) sampling. The aliasing ratio based on SABER sampling is 75% at 40°S during late January, where and when W3 peaks. The analysis of the synoptic WACCM data set shows that the E2 is in fact a winter phenomenon, which peaks in the stratosphere and lower mesosphere at high latitudes. In the austral winter period, the amplitudes of E2 can reach ~10 K, 20 m/s, and 30 m/s for temperature, zonal, and meridional winds, respectively. In the boreal winter period, the wave perturbations are only one third as strong as those in austral winter. Diagnostic analysis also shows that the mean flow instabilities in the winter upper mesosphere polar region provide sources for the amplification of E2. This is different from the westward QTDWs, whose amplifications are related to the summer easterly jet. In addition, the E2 also peaks at lower altitude than the westward modes.

Section: Waccmsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

On the wave number 2 eastward propagating quasi 2 day wave at middle and high latitudes

Liu

Pedatella

et al. 2017

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“…The Advanced Level Physics High Altitude version of the Navy Operational Global Atmospheric Prediction System (NOGAPS‐ALPHA) reanalysis data set shows that the interannual variations of the QTDW during the boreal summer period are dependent on the strength of the summer easterlies, and stronger summer easterlies provide larger forcing for its amplification (McCormack et al, ). Recently, Gu, Liu, Pedatella, Dou, & Shu () found that the strength of the summer easterlies is also responsible for selective amplification of the QTDWs with different zonal wave numbers. The W2 QTDW peaks with stronger summer easterlies than the W3 mode.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Abnormal Quasi 2‐Day Wave Activities During the Sudden Stratospheric Warming Period of January 2006

Dou

Pancheva

et al. 2018

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A quasi 2‐day wave (QTDW) during the austral summer period usually coincides with a sudden stratospheric warming (SSW) event in the winter hemisphere, while the SSW influences on QTDWs are not totally understood. In this work, the hourly Navy Operational Global Atmospheric Prediction System‐Advanced Level Physics High Altitude reanalysis data sets during January/February 2006 are utilized to study the contribution of a major SSW on the anomalous QTDW activities during the same period. Our new findings are generalized as follows: (1) The summer easterly is enhanced during a SSW event due to the interhemispheric coupling, which is clearly indicated by the anomalous cross‐equator circulation from the winter to summer mesosphere. (2) The enhanced summer easterly could sustain critical layers for QTDWs with larger phase speeds (e.g., smaller zonal wave number or shortwave period) and strengthen the summer easterly barotropic/baroclinic instabilities, which are essential for the QTDW amplification through wave‐mean flow interactions. This is why a strong westward QTDW with zonal wave number 2 is identified besides the conventionally dominant wave mode of wave number 3, and their periods are only ~42–45 hr during January 2006. (3) The strong winter planetary waves during SSW periods facilitate the occurrence of the nonlinear interaction between QTDWs and stationary planetary waves, which is strongly suggested by the abnormal temporal variations of wave number 2 and wave number 3 QTDWs. We conclude that the anomalous QTDW behaviors in summer mesosphere during January 2006 are associated with the major SSW event in the winter stratosphere.

“…Weaker wave number 2 (W2) and 4 (W4) modes have also been identified (Gu, Liu, Li, Dou, Wu, et al, ; Gu, Liu, Pedatella, Dou, Li, et al, ; Tunbridge et al, ). In the Northern Hemisphere, the QTDW peaks intermittently from June to August with the W3 and W4 modes being equally strong (Gu, Liu, Pedatella, Dou, & Shu, ; McCormack et al, ; Pancheva et al, ). Generally, the QTDWs during the austral summer period are stronger than those during the boreal summer period.…”

Section: Introductionmentioning

confidence: 99%

The Modulation of the Quasi‐Two‐Day Wave on Total Electron Content as Revealed by BeiDou GEO and Meteor Radar Observations Over Central China

Lei

Dou

et al. 2017

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The ground‐based total electron content (TEC) observations from BeiDou Geostationary Orbit (GEO) satellites provide more accurate temporal ionospheric variations nearly at the fixed ionospheric pierce points as compared with the non‐GEO TEC. BeiDou GEO TEC measurements during 2016, along with the horizontal wind observations from a collocated meteor radar, are utilized to quantitatively study the ionospheric response to the quasi‐two‐day wave (QTDW) in the neutral atmosphere at Meng Cheng (116.6°E, 33.3°N) over central China. The QTDW peaks during July with amplitudes of ~25–30 m/s for both zonal and meridional winds. It is suggested that the nonlinear interactions between the QTDW and tides and their influences on TEC are insignificant for this QTDW event. Nevertheless, the diurnal tide decreases by ~40–60% during the QTDW episode, which is most likely related to the change of background wind induced by the QTDW. Correspondingly, the 24 h oscillations in TEC decrease by ~18%. In addition, the wind perturbations of the QTDW can also possibly modulate the midlatitude electric dynamo and result in a quasi‐two‐day oscillation (QTDO) of ~1.2 total electron content unit (TECU), about ~10% of the background TEC. Our analysis also shows that the background TEC decreases by ~1 TECU (~8%) when the QTDW reaches maximum amplitude. This is probably related to the thermospheric composition changes (e.g., O and N2) induced by the QTDW dissipation.