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  • DYNAMO/CINDY/AMIE/LASP: Processes, Dynamics, and Prediction of MJO Initiation x
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James N. Moum, Simon P. de Szoeke, William D. Smyth, James B. Edson, H. Langley DeWitt, Aurélie J. Moulin, Elizabeth J. Thompson, Christopher J. Zappa, Steven A. Rutledge, Richard H. Johnson, and Christopher W. Fairall

(total) appears as a step function change from near-0 to 0.5 N m −2 in a few minutes. (b) Net surface heating. Net surface cooling lasted for more than one day, a rarity at the equator, though common during the passage of MJO events. (c) Zonal current. The eastward surface current (the Yoshida–Wyrtki jet) accelerated from <0.5 m s −1 in about one day, deepening with time. The mixed layer is indicated by the black line, the potential density surface 1024.5 is indicated by the white line. (d

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Aurélie J. Moulin, James N. Moum, and Emily L. Shroyer

increases the gravitational stability of the system, thereby dampening turbulence. For example, turbulence has been shown to decay by an order of magnitude when the near-surface stratifies, either through surface heating ( Brainerd and Gregg 1993 ; Caldwell et al. 1997 ) or precipitation ( Smyth et al. 1997 ). At the same time, increased stratification in the DWL is known to trap wind-driven momentum at the base of the surface mixed layer forming a diurnal jet ( Thorpe 1978 ; Price et al. 1986

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Kunio Yoneyama, Chidong Zhang, and Charles N. Long

is the only large tropical ocean that is bounded by land in three directions. It is therefore the ocean that experiences the strongest influence of the monsoons. The monsoon circulation and the trade winds over the Indian Ocean induce unusually shallow thermocline in the middle of the basin, known as the Seychelles–Chagos thermocline ridge ( Vialard et al. 2009 ), and strong eastward surface current along the equator, the Wyrtki jet, which appears semiannually during the monsoon transition

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Jean-Philippe Duvel

on the intensification process. It is likely that the MJO modulation of the background flow has a major role in the initiation of more numerous TDs. One can find an analogy with the background African easterly jet (AEJ) that produces African easterly waves (AEW) that later generate TDs in the North Atlantic (e.g., Landsea 1993 ; Dunkerton et al. 2009 ). The perturbation of the background flow by the MJO, and especially the westerly low-level jet developing in and after the active phase, may

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H. Bellenger, R. Wilson, J. L. Davison, J. P. Duvel, W. Xu, F. Lott, and M. Katsumata

-wavelength/higher-frequency waves are likely to be observed close to their source, whereas longer-wavelength/lower-frequency GWs can propagate great distance away from their sources (e.g., Hankinson et al. 2014a , b ). Over the central equatorial Indian Ocean, which lacks any significant orography, the most probable GW sources are convection and jet streams. Therefore, we anticipate an observable link between convective activity (both local and distant), GW characteristics, and turbulence. This study is based on radiosonde

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Michael S. Pritchard and Christopher S. Bretherton

vorticity anomalies causes a poleward shift of the midlatitude jets and decelerated upper-level flow. As α is decreased from unity, the reverse is true. Interestingly, upper-level equatorial superrotation decreases as α is increased from unity. This is opposite to the covariation of MJO amplitude and upper-level superrotation seen recently in aquaplanet sea surface temperature warming by Arnold et al. (2013) . Figure 15 shows that in the tropics the low-level wind response to increasing α from

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Ji-Hyun Oh, Xianan Jiang, Duane E. Waliser, Mitchell W. Moncrieff, Richard H. Johnson, and Paul Ciesielski

region, the mesoscale inflow jet brings westerly momentum downward, enhancing the surface westerlies. Numerical simulations by Lafore and Moncrieff (1989) showed that the strong midtropospheric inflow at the rear of mesoscale convective systems is driven by the horizontal pressure gradient arising from potential temperature gradients that are generated by latent heating in the convective region and unsaturated evaporation-driven mesoscale descent. On the basis of residual momentum budget analysis

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Nick Guy and David P. Jorgensen

mesoscale descent or ascent (i.e., rear inflow jet) was found, with perturbations in vertical flow corresponding to convective cell locations. There was a general weak descent below 5 km during this period. Fig . 8. (a) Horizontal reflectivity map at 2-km altitude collected by the tail radar during the second RCE module on 24 Nov 2011. Overlaid vector arrows indicated the horizontal wind solution from the quasi-dual-Doppler analysis (with reference vector at the top right) and the solid black line shows

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Hyodae Seo, Aneesh C. Subramanian, Arthur J. Miller, and Nicholas R. Cavanaugh

: Origins and dynamics of the 90-day and 30–60-day variations in the equatorial Indian Ocean . J. Phys. Oceanogr. , 35 , 708 – 728 , doi: 10.1175/JPO2725.1 . Han , W. , J. P. McCreary , D. L. T. Anderson , and A. J. Mariano , 1999 : Dynamics of the eastward surface jets in the equatorial Indian Ocean . J. Phys. Oceanogr. , 29 , 2191 – 2209 , doi: 10.1175/1520-0485(1999)029<2191:DOTESJ>2.0.CO;2 . Hendon , H. H. , B. Liebmann , M. Newman , J. D. Glick , and J. Schemm , 2000

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Sue Chen, Maria Flatau, Tommy G. Jensen, Toshiaki Shinoda, Jerome Schmidt, Paul May, James Cummings, Ming Liu, Paul E. Ciesielski, Christopher W. Fairall, Ren-Chieh Lien, Dariusz B. Baranowski, Nan-Hsun Chi, Simon de Szoeke, and James Edson

descending branches of the MRG circulation as well as regions of enhanced surface fluxes. The positive RH anomalies form a more continuous sinusoidal pattern that connects the separate maxima located in either hemisphere. This is similar to the positive anomalies in the zonal flow component, suggesting the development of an oscillating moist low-level zonal jet structure that straddles the equatorial region. Fig . 16. A horizontal plan view of the idealized MRG structure taken at 96 h into the simulation

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