A note on apparent solar time and the seasonal cycle of atmospheric solar tides

Hamilton, Kevin; Sakazaki, Takatoshi

doi:10.1002/qj.3076

Cited by 7 publications

(6 citation statements)

References 28 publications

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“…Although the SABER results are noisy, all data sets basically show that the amplitude max- imizes twice in December-January-February and in JuneJuly-August in the upper stratosphere and the lower mesosphere. In the lower and middle stratosphere, by contrast, the amplitude minimizes during June-July-August; notably, this is similar to the seasonality of surface pressure tides (e.g., Díaz-Argandoña et al, 2016;Hamilton and Sakazaki, 2017). Such seasonality in the stratosphere was reported earlier by Li et al (2015) using the CFSR reanalysis.…”

Section: Semidiurnal (S 2 ) Migrating Tidesupporting

confidence: 80%

“…For reanalyses, 3-or 6-hourly diurnal variations in UT are extracted at each grid point through composite analysis based on UT after the subtraction of the daily mean; in fact, we downloaded and analyzed the diurnal monthly mean (monthly mean for each UTC snapshot) data provided by each reanalysis center (e.g., for JRA-55, diurnal monthly mean data are the monthly averages for 00:00, 06:00, 12:00, and 18:00 UTC). Clearly the 6-hourly data (ERA-Interim, JRA-55, and CFSR) cannot resolve S 2 at each grid point, but the "migrating component" of S 2 can be extracted by using data at grid points on the same latitude belt, as explained in the following (Ray and Ponte, 2003;Díaz-Argandoña et al, 2016;Hamilton and Sakazaki, 2017).…”

Section: Migrating and Nonmigrating Tidesmentioning

confidence: 99%

“…Only a few studies have examined S 2 tides in reanalyses (although the solar S 2 surface pressure oscillation has been more extensively studied; e.g., Ray and Ponte, 2003;Saha et al, 2010;Díaz-Argandoña et al, 2016;Hamilton and Sakazaki, 2017). Hsu and Hoskins (1989) and Kohyama and Wallace (2014) derived S 2 migrating tides in the stratosphere by using the ECMWF operational analysis and the ERA-Interim, respectively.…”

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confidence: 99%

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Representation of solar tides in the stratosphere and lower mesosphere in state-of-the-art reanalyses and in satellite observations

2018

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Abstract. Atmospheric solar tides in the stratosphere and the lower mesosphere are investigated using temperature data from five state-of-the-art reanalysis data sets (MERRA-2, MERRA, JRA-55, ERA-Interim, and CFSR) as well as TIMED SABER and Aura MLS satellite measurements. The main focus is on the period 2006-2012 during which the satellite observations are available for direct comparison with the reanalyses. Diurnal migrating tides, semidiurnal migrating tides, and nonmigrating tides are diagnosed. Overall the reanalyses agree reasonably well with each other and with the satellite observations for both migrating and nonmigrating components, including their vertical structure and the seasonality. However, the agreement among reanalyses is more pronounced in the lower stratosphere and relatively weaker in the upper stratosphere and mesosphere. A systematic difference between SABER and the reanalyses is found for diurnal migrating tides in the upper stratosphere and the lower mesosphere; specifically, the amplitude of trapped modes in reanalyses is significantly smaller than that in SABER, although such difference is less clear between MLS and the reanalyses. The interannual variability and the possibility of long-term changes in migrating tides are also examined using the reanalyses during 1980-2012. All the reanalyses agree in exhibiting a clear quasi-biennial oscillation (QBO) in the tides, but the most significant indications of long-term changes in the tides represented in the reanalyses are most plausibly explained by the evolution of the satellite observing systems during this period. The tides are also compared in the full reanalyses produced by the Japan Meteorological Agency (i.e., JRA-55) and in two parallel data sets from this agency: one (JRA-55C) that repeats the reanalysis procedure but without any satellite data assimilated and one (JRA-55AMIP) that is a free-running integration of the model constrained only by observed sea surface temperatures. Many aspects of the tides are closer in JRA-55C and JRA-55AMIP than these are to the full reanalysis JRA-55, demonstrating the importance of the assimilation of satellite data in representing the diurnal variability of the middle atmosphere. In contrast to the assimilated data sets, the freerunning model has no QBO in equatorial stratospheric mean circulation and our results show that it displays no quasibiennial variability in the tides.

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Section: Semidiurnal (S 2 ) Migrating Tidesupporting

confidence: 80%

Section: Migrating and Nonmigrating Tidesmentioning

confidence: 99%

mentioning

confidence: 99%

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Representation of solar tides in the stratosphere and lower mesosphere in state-of-the-art reanalyses and in satellite observations

2018

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Section: Migrating and Nonmigrating Tidesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Representation of solar tides in the stratosphere and lower mesosphere in state-of-the-art reanalyses and in satellite observations

Sakazaki¹,

Fujiwara²,

Shiotani³

2017

Preprint

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<p><strong>Abstract.</strong> Atmospheric solar tides in the stratosphere and the lower mesosphere are investigated using temperature data from five state-of-the-art reanalysis data sets (MERRA-2, MERRA, JRA-55, ERA-Interim and CFSR) as well as TIMED/SABER and Aura/MLS satellite measurements. The main focus is on the period 2006&#8211;2012 during which the satellite observations are available for direct comparison with the reanalyses. Diurnal migrating tides, semidiurnal migrating tides, and nonmigrating tides are diagnosed. Overall the reanalyses agree reasonably well with each other and with the satellite observations for both migrating and nonmigrating components including their vertical structure and the seasonality. However, the agreement among reanalyses is more pronounced in the lower stratosphere and relatively weaker in the upper stratosphere and mesosphere. A systematic difference between SABER and reanalyses is found for diurnal migrating tides in the upper stratosphere and the lower mesosphere, specifically that the amplitude of trapped modes in reanalyses is significantly smaller than that in SABER, although such difference is less clear between MLS and reanalyses. The interannual variability and the possibility of long-term changes of migrating tides are also examined using the reanalyses during 1980-2012. All the reanalyses agree in exhibiting a clear quasi biennial oscillation (QBO) in the tides, but the most significant indications of long-term changes in the tides represented in the reanalyses are most plausibly explained by the evolution of the satellite observing systems during this period. The tides are also compared in the full reanalyses produced by the Japan Meteorological Agency (i.e. JRA-55) and in two parallel data sets from this agency: one (JRA-55C) which repeats the reanalysis procedure but without any satellite data assimilated, and one (JRA-55AMIP) that is a free-running integration of the model constrained only by observed sea surface temperatures. Many aspects of the tides are closer in JRA-55C and JRA-55AMIP than these are to the full reanalysis JRA-55, demonstrating the importance of the assimilation of satellite data in representing the diurnal variability of the middle atmosphere. In contrast to the assimilated data sets, the free running model has no QBO in equatorial stratospheric mean circulation and our results show that it displays no quasibiennial variability in the tides.</p>

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The diurnal cycle from observations and ERA5 in surface pressure, temperature, humidity, and winds

Dai

2023

Clim Dyn

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A note on apparent solar time and the seasonal cycle of atmospheric solar tides

Cited by 7 publications

References 28 publications

Representation of solar tides in the stratosphere and lower mesosphere in state-of-the-art reanalyses and in satellite observations

Representation of solar tides in the stratosphere and lower mesosphere in state-of-the-art reanalyses and in satellite observations

Representation of solar tides in the stratosphere and lower mesosphere in state-of-the-art reanalyses and in satellite observations

The diurnal cycle from observations and ERA5 in surface pressure, temperature, humidity, and winds

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