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concludes with further discussion in section 5 . 2. Theoretical considerations How can we, then, explain the MJO in terms the dry dynamics? Under the linear limit, the large-scale tropical atmospheric dynamics consists of a set of the equatorial waves ( Matsuno 1966 ; Yano and Bonazzola 2009 ). Thus, if the MJO is to be explained in terms of the linear dynamics, it must be explained in terms of the slowest-propagating equatorial planetary-scale waves: the Kelvin or the Rossby wave. At first sight, the
concludes with further discussion in section 5 . 2. Theoretical considerations How can we, then, explain the MJO in terms the dry dynamics? Under the linear limit, the large-scale tropical atmospheric dynamics consists of a set of the equatorial waves ( Matsuno 1966 ; Yano and Bonazzola 2009 ). Thus, if the MJO is to be explained in terms of the linear dynamics, it must be explained in terms of the slowest-propagating equatorial planetary-scale waves: the Kelvin or the Rossby wave. At first sight, the
1. Introduction The tropical atmosphere consists of weather systems spanning a wide range of spatial and temporal scales. At the planetary scale, the Madden–Julian oscillation (MJO) is found to be the dominant mode of intraseasonal variability with typical periods of 20–100 days ( Madden and Julian 1971 , 1972 ; Zhang 2005 ). The active phase of an MJO is characterized by enhanced deep convection and intense precipitation that propagates eastward at a speed around 5 m s −1 . Within the MJO
1. Introduction The tropical atmosphere consists of weather systems spanning a wide range of spatial and temporal scales. At the planetary scale, the Madden–Julian oscillation (MJO) is found to be the dominant mode of intraseasonal variability with typical periods of 20–100 days ( Madden and Julian 1971 , 1972 ; Zhang 2005 ). The active phase of an MJO is characterized by enhanced deep convection and intense precipitation that propagates eastward at a speed around 5 m s −1 . Within the MJO
Bretherton 2001 ; Tung and Yanai 2002a , b ; Lin et al. 2005 ). Using Doppler radar data, Houze et al. (2000) identified strong midlevel inflow in the stratiform regions of mesoscale convective systems (MCSs) during the westerly onset and in regions of strong westerly winds associated with the Kelvin–Rossby wave pattern. They postulated that the mesoscale inflow transports easterly momentum downward, reducing the westerlies near the surface in the westerly onset region, while in the strong westerly
Bretherton 2001 ; Tung and Yanai 2002a , b ; Lin et al. 2005 ). Using Doppler radar data, Houze et al. (2000) identified strong midlevel inflow in the stratiform regions of mesoscale convective systems (MCSs) during the westerly onset and in regions of strong westerly winds associated with the Kelvin–Rossby wave pattern. They postulated that the mesoscale inflow transports easterly momentum downward, reducing the westerlies near the surface in the westerly onset region, while in the strong westerly
MJO and high-frequency tropical wave modes are discussed in section 5 and conclusions summarized in section 6 . 2. Model description The baseline code used for all simulations is the prototype version of SPCAM, version 3.0, as archived [ https://svn.sdsc.edu/repo/cmmap/cam3_sp (rev. 80)] by the Center for Multiscale Modeling of Atmospheric Processes. The global scale is represented by a version of CAM that slightly predates the CAM3.0 release. Global dynamics are formulated spectrally, with a
MJO and high-frequency tropical wave modes are discussed in section 5 and conclusions summarized in section 6 . 2. Model description The baseline code used for all simulations is the prototype version of SPCAM, version 3.0, as archived [ https://svn.sdsc.edu/repo/cmmap/cam3_sp (rev. 80)] by the Center for Multiscale Modeling of Atmospheric Processes. The global scale is represented by a version of CAM that slightly predates the CAM3.0 release. Global dynamics are formulated spectrally, with a
a role in alternate theories for convective organization, including those based on frictionally driven convergence ( Wang 1988 ; Seo and Wang 2010 ; Hsu and Li 2012 ), or boundary layer moisture convergence as a Kelvin-wave response ( Wang and Rui 1990 ; Maloney and Hartmann 1998 ; Hsu and Li 2012 ). Here, we are concerned only with the convective–dynamical interactions, not with its application to the MJO or other large-scale circulations at this point. Furthermore, while our initial
a role in alternate theories for convective organization, including those based on frictionally driven convergence ( Wang 1988 ; Seo and Wang 2010 ; Hsu and Li 2012 ), or boundary layer moisture convergence as a Kelvin-wave response ( Wang and Rui 1990 ; Maloney and Hartmann 1998 ; Hsu and Li 2012 ). Here, we are concerned only with the convective–dynamical interactions, not with its application to the MJO or other large-scale circulations at this point. Furthermore, while our initial
developed by W10 to properly treat the instrumental-noise issue. Turbulence can originate from static instabilities or from Kelvin–Helmholtz instabilities. These instabilities can be associated with gravity wave (GW) activity ( Cadet 1977 ; Barat 1983 ; Chao and Schoeberl 1984 ; Fritts and Dunkerton 1985 ; Fritts and Rastogi 1985 ; Fritts et al. 1988b ; Pavelin et al. 2001 ; Sharman et al. 2012 ; Fritts et al. 2016 ). This suggests the possibility of GWs playing a role in the formation of the
developed by W10 to properly treat the instrumental-noise issue. Turbulence can originate from static instabilities or from Kelvin–Helmholtz instabilities. These instabilities can be associated with gravity wave (GW) activity ( Cadet 1977 ; Barat 1983 ; Chao and Schoeberl 1984 ; Fritts and Dunkerton 1985 ; Fritts and Rastogi 1985 ; Fritts et al. 1988b ; Pavelin et al. 2001 ; Sharman et al. 2012 ; Fritts et al. 2016 ). This suggests the possibility of GWs playing a role in the formation of the
1. Introduction The Madden–Julian oscillation (MJO; e.g., Madden and Julian 1971 , 1972 ) is an eastward-propagating, planetary-scale envelope of organized convective activity in the tropics. Characterized by gross features in the 20–90-day intraseasonal time range and zonal wavenumbers 1–4, it dominates tropical variability in subseasonal time scales. Moreover, through tropical–extratropical interactions, it influences global weather and climate variability, fundamentally linking short
1. Introduction The Madden–Julian oscillation (MJO; e.g., Madden and Julian 1971 , 1972 ) is an eastward-propagating, planetary-scale envelope of organized convective activity in the tropics. Characterized by gross features in the 20–90-day intraseasonal time range and zonal wavenumbers 1–4, it dominates tropical variability in subseasonal time scales. Moreover, through tropical–extratropical interactions, it influences global weather and climate variability, fundamentally linking short
2009 ; Chikira 2014 ) emphasize feedbacks to tropospheric moisture for creating unstable intraseasonal convective modes in the column MSE budget. The tropical intraseasonal skeleton model of Majda and Stechmann (2009) suggests that BL moisture east of the area of active MJO convection stimulates synoptic wave activity that supports the spatial structure of the MJO. The ( Wang et al. 2016 ) trio-interaction theory for the MJO explores interactions among convection, moisture, and BL wave dynamics
2009 ; Chikira 2014 ) emphasize feedbacks to tropospheric moisture for creating unstable intraseasonal convective modes in the column MSE budget. The tropical intraseasonal skeleton model of Majda and Stechmann (2009) suggests that BL moisture east of the area of active MJO convection stimulates synoptic wave activity that supports the spatial structure of the MJO. The ( Wang et al. 2016 ) trio-interaction theory for the MJO explores interactions among convection, moisture, and BL wave dynamics
1. Introduction The Madden–Julian oscillation (MJO) is a planetary-scale phenomenon that modulates convective activity in the tropics on intraseasonal time scales (30–100 days) ( Madden and Julian 1971 , 1972 ). The MJO is characterized by an envelope of increased rainfall and free-tropospheric water vapor that originates over the Indian Ocean, propagates eastward at 5–8 m s −1 , and dissipates over the central Pacific. This convective envelope modulates rainfall and tropical cyclogenesis as
1. Introduction The Madden–Julian oscillation (MJO) is a planetary-scale phenomenon that modulates convective activity in the tropics on intraseasonal time scales (30–100 days) ( Madden and Julian 1971 , 1972 ). The MJO is characterized by an envelope of increased rainfall and free-tropospheric water vapor that originates over the Indian Ocean, propagates eastward at 5–8 m s −1 , and dissipates over the central Pacific. This convective envelope modulates rainfall and tropical cyclogenesis as
, S. S. Babu , R. R. Reddy , and K. R. Gopal , 2009 : Large scale modulations of spectral aerosol optical depths by atmospheric planetary waves . Geophys. Res. Lett. , 36 , L03810 , doi: 10.1029/2008GL036509 . 10.1029/2008GL036509 Boccippio , D. J. , S. J. Goodman , and S. Heckman , 2000 : Regional differences in tropical lightning distributions . J. Appl. Meteor. , 39 , 2231 – 2248 , doi: 10.1175/1520-0450(2001)040<2231:RDITLD>2.0.CO;2 . 10
, S. S. Babu , R. R. Reddy , and K. R. Gopal , 2009 : Large scale modulations of spectral aerosol optical depths by atmospheric planetary waves . Geophys. Res. Lett. , 36 , L03810 , doi: 10.1029/2008GL036509 . 10.1029/2008GL036509 Boccippio , D. J. , S. J. Goodman , and S. Heckman , 2000 : Regional differences in tropical lightning distributions . J. Appl. Meteor. , 39 , 2231 – 2248 , doi: 10.1175/1520-0450(2001)040<2231:RDITLD>2.0.CO;2 . 10
