With the method of Hough mode decomposition(HMD),the tidal sources of the three main tidal components,namely,the migrating components DW1(diurnal westward propagating wavenumber 1)and SW2(semidiurnal westward propagat...With the method of Hough mode decomposition(HMD),the tidal sources of the three main tidal components,namely,the migrating components DW1(diurnal westward propagating wavenumber 1)and SW2(semidiurnal westward propagating wavenumber 2)and the non-migrating component DE3(diurnal eastward propagating wavenumber 3),at the tropospheric altitudes(1–12 km)and in the latitude range of±60°,were obtained from National Centers for Environmental Prediction(NCEP)Climate Forecast System Reanalysis(CFSR)data during the interval from 1988 to 2011.We analyzed these sources in detail at 6 km and obtained the main properties of their yearly variations.The DW1 source was found to present a weak seasonal variation in the lower latitudes(about±10°–15°).That is,the amplitudes of the DW1 sources were larger in the summer months than in the winter months,and DW1 presented semi-annual variation near the equator(±10°)such that the DW1 source was larger at the equinoxes than at the solstices.In addition,the SW2 source was symmetric and was stronger in the southern hemisphere than in the northern hemisphere.The SW2 source presented remarkable annual and semi-annual variation such that the amplitudes were largest during the March equinox months and larger during the June solstice months.In contrast,DE3 appeared mainly around the equatorial latitudes within about±30°.The DE3 source presented remarkable semiannual variation that was larger around the solstices than the equinoxes in the southern hemisphere,and it was opposite in the northern hemisphere.By HMD,we found that the tropospheric tides were primarily dominated by some leading propagating Hough modes,specifically,the(1,1),(2,3),and(3,3)modes;the influences of the other Hough modes were negligible.The consequences of an El Niño–Southern Oscillation modulation of tidal amplitudes for the energy and momentum budgets of the troposphere may now be expected to attract attention.In summary,the above yearly variations of the main tidal sources and the Hough coefficients demonstrate that an HMD analysis can be used to investigate the tropospheric tides.展开更多
The Hough mode decomposition (HMD) is used to investigate the global structures of the eastward propagating diurnal tide of zonal wavenumber 3 (DE3). The tide is delineated by using the SABER/ TIMED temperatures colle...The Hough mode decomposition (HMD) is used to investigate the global structures of the eastward propagating diurnal tide of zonal wavenumber 3 (DE3). The tide is delineated by using the SABER/ TIMED temperatures collected during 2002―2006. The HMD analysis results show that the DE3 tide is primarily dominated by two leading propagating Hough modes, i.e., (-3, 3) and (-3, 4) modes; the in-fluences .of the other Hough modes including trapped modes can be neglected. Based upon the HMD analysis results, this paper first reported the maximum of the tidal activity in the MLT region. The re-sults show that the DE3 tide exhibits annual unimodal distribution with the maximal amplitude occur-ring at 110 km in late summer (around July each year). Moreover, characteristic 2-year period variation is observed in the (-3, 3) Hough mode. And this type of inter-annual variation is further reflected in the tidal amplitude at 110 km height. For example, corresponding to the 2-year variation of the (-3, 3) mode, the DE3 tidal amplitude exhibits two substantially enhanced activities with maximal amplitude exceed-ing 12 K in 2002 and 2004, respectively. Moreover, current investigation results indicate that the influ-ence of the second propagating Hough mode, (-3, 4) mode, is important, in particular at the height un-der 100 km, where the DE3 amplitudes exhibit antisymmetric distribution with respect to the equator. The (-3, 4) mode exhibits bimodal distribution over a yearly course, which dominates the DE3 tide in the lower mesosphere. For example, two maximal DE3 activities were observed in late-winter-to-early- spring and late-autumn-to-early-winter, respectively. The first maximum is seen in the south of the equator, and the second maximum is in the north of it.展开更多
基金The present work is supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(grant no.XDA17010201)the National Science Foundation of China(grant nos.41604138,41427901,41621063,41474133,41674158,41874179,and 41322030).
文摘With the method of Hough mode decomposition(HMD),the tidal sources of the three main tidal components,namely,the migrating components DW1(diurnal westward propagating wavenumber 1)and SW2(semidiurnal westward propagating wavenumber 2)and the non-migrating component DE3(diurnal eastward propagating wavenumber 3),at the tropospheric altitudes(1–12 km)and in the latitude range of±60°,were obtained from National Centers for Environmental Prediction(NCEP)Climate Forecast System Reanalysis(CFSR)data during the interval from 1988 to 2011.We analyzed these sources in detail at 6 km and obtained the main properties of their yearly variations.The DW1 source was found to present a weak seasonal variation in the lower latitudes(about±10°–15°).That is,the amplitudes of the DW1 sources were larger in the summer months than in the winter months,and DW1 presented semi-annual variation near the equator(±10°)such that the DW1 source was larger at the equinoxes than at the solstices.In addition,the SW2 source was symmetric and was stronger in the southern hemisphere than in the northern hemisphere.The SW2 source presented remarkable annual and semi-annual variation such that the amplitudes were largest during the March equinox months and larger during the June solstice months.In contrast,DE3 appeared mainly around the equatorial latitudes within about±30°.The DE3 source presented remarkable semiannual variation that was larger around the solstices than the equinoxes in the southern hemisphere,and it was opposite in the northern hemisphere.By HMD,we found that the tropospheric tides were primarily dominated by some leading propagating Hough modes,specifically,the(1,1),(2,3),and(3,3)modes;the influences of the other Hough modes were negligible.The consequences of an El Niño–Southern Oscillation modulation of tidal amplitudes for the energy and momentum budgets of the troposphere may now be expected to attract attention.In summary,the above yearly variations of the main tidal sources and the Hough coefficients demonstrate that an HMD analysis can be used to investigate the tropospheric tides.
基金Supported by Knowledge Innovation Project of the Chinese Academy of Sciences (CAS) (Grant Nos. KZCX2-YW-123 and KGCX3-SYW-403)National Natural Science Foundation of China (Grant No. 40333034)Institute of Atmospheric Physics of CAS (Grant No. IAP07212)
文摘The Hough mode decomposition (HMD) is used to investigate the global structures of the eastward propagating diurnal tide of zonal wavenumber 3 (DE3). The tide is delineated by using the SABER/ TIMED temperatures collected during 2002―2006. The HMD analysis results show that the DE3 tide is primarily dominated by two leading propagating Hough modes, i.e., (-3, 3) and (-3, 4) modes; the in-fluences .of the other Hough modes including trapped modes can be neglected. Based upon the HMD analysis results, this paper first reported the maximum of the tidal activity in the MLT region. The re-sults show that the DE3 tide exhibits annual unimodal distribution with the maximal amplitude occur-ring at 110 km in late summer (around July each year). Moreover, characteristic 2-year period variation is observed in the (-3, 3) Hough mode. And this type of inter-annual variation is further reflected in the tidal amplitude at 110 km height. For example, corresponding to the 2-year variation of the (-3, 3) mode, the DE3 tidal amplitude exhibits two substantially enhanced activities with maximal amplitude exceed-ing 12 K in 2002 and 2004, respectively. Moreover, current investigation results indicate that the influ-ence of the second propagating Hough mode, (-3, 4) mode, is important, in particular at the height un-der 100 km, where the DE3 amplitudes exhibit antisymmetric distribution with respect to the equator. The (-3, 4) mode exhibits bimodal distribution over a yearly course, which dominates the DE3 tide in the lower mesosphere. For example, two maximal DE3 activities were observed in late-winter-to-early- spring and late-autumn-to-early-winter, respectively. The first maximum is seen in the south of the equator, and the second maximum is in the north of it.
