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  • Boundary currents x
  • DYNAMO/CINDY/AMIE/LASP: Processes, Dynamics, and Prediction of MJO Initiation x
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Yue Ying and Fuqing Zhang

other modeling systems that account for additional error sources (e.g., model dynamics, physics parameterizations, and low-boundary-condition forcings). The predictability estimates from the MJO active phase event in this study may also differ from those estimated for other events. The current study only simulates a 15-day period within an MJO active phase, which is not long enough to estimate the predictability of MJO itself. In previous MJO predictability studies using global model simulations

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Douglas C. Stolz, Steven A. Rutledge, Weixin Xu, and Jeffrey R. Pierce

Arabian Sea, Bay of Bengal, and the tropical Indian Ocean ( Satheesh et al. 1999 ; Ramanathan et al. 2001 ). Hence, we represent CCN for our study by the boundary layer average for 1000–850 hPa. Background thermodynamics and low-level winds (1000–850-hPa average) derived from the Modern-Era Retrospective Analysis for Research and Applications (MERRA; ) are analyzed at 0000, 0600, 1200, and 1800 UTC and subsequently averaged over each full day in the current study

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David M. Zermeño-Díaz, Chidong Zhang, Pavlos Kollias, and Heike Kalesse

UTC (2100 and 0900 local time). Their averages were used to represent daily means. Soundings with melting-level heights outside the typical range of 3.5–5.5 km ( Geerts and Dawei 2004 ) were considered unreliable and excluded from our study. Sounding estimates of boundary layer heights from four methods (C. Sivaraman et al. 2012, meeting presentation) were averaged to provide a daily mean best estimate. There are six MMCR profiles per minute in the ARSCL data over different vertical ranges with a

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Emily M. Riley Dellaripa, Eric Maloney, and Susan C. van den Heever

simulation was initialized on 1200 UTC 30 October 2011 and run with 36 h of domainwide nudging to ERA-I. This second 4-km control simulation is referred to as “4Ctrl12” ( Table 1 ). For all of the control simulations, the time period with domainwide nudging is considered model spinup and not included in analysis. Starting on 0000 UTC 1 November (i.e., after domainwide nudging has ceased in all control simulations), lateral boundary nudging was applied to the seven outermost grid points with a 30-min time

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Simon P. de Szoeke, Eric D. Skyllingstad, Paquita Zuidema, and Arunchandra S. Chandra

capable of accelerating the air downward, forming a downdraft. Continued evaporative cooling and moistening by rain keeps the downdraft nearly saturated when it reaches the planetary boundary layer (BL), where it spreads horizontally along the surface in a cold pool ( Zipser 1977 ). Cold pools have become a topic of renewed fascination because of their potential role in assisting the shallow-to-deep convective transition (e.g., Rowe and Houze 2015 ) and to correct erroneous convective diurnal cycles

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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

increase in the boundary layer moisture near the central and eastern axis of the MJO convection and the development of westerly wind anomalies along the equator ( Wang and Xie 1998 ; Kemball-Cook and Wang 2001 ; Weare 2003 ; Maloney and Hartmann 2000 ; Sperber 2003 ; Seo and Kim 2003 ). More recent studies ( Tian et al. 2010 ; Benedict and Randall 2007 ) have shown the moisture distribution during the MJO cycle consists of large-scale alternating dry and moist anomalies. Results from Benedict

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Hungjui Yu, Richard H. Johnson, Paul E. Ciesielski, and Hung-Chi Kuo

conceptual mesoscale process was proposed involving the nonlinear interaction between clouds, radiation, and surface processes, the so-called “diurnal dancing” of convective systems, to explain the near 2-day periodicity. In their scenario, despite diurnal radiative forcing, boundary layer (BL) recovery extends to a second day, likely due to the expanded stratiform clouds of MCSs, which impacts the timing of the next round of convection. The BL recovery for a future convective event over a given region

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James H. Ruppert Jr. and Fuqing Zhang

distinction in phase speed remains unclear; however, density current theory may at least shed light on the propagation rate of individual rainfall systems. This is explored next. Cross sections depicting the low-level atmospheric structure, both in the zonal and in the diagonal (cross-Sumatra) contexts, are provided in Figs. 11 and 12 . In the boundary layer over and west of Borneo, low-level isentropes (of constant θ υ ) reveal a localized surface-based cold anomaly extending from the landmass across

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Elizabeth J. Thompson, Steven A. Rutledge, Brenda Dolan, and Merhala Thurai

across the warm pool ( Johnson et al. 1999 ; Rauber et al. 2007 ; Jakob and Schumacher 2008 ; Barnes and Houze 2013 ), where the atmosphere is conditionally unstable below the equivalent potential temperature θ e minimum ( Lilly 1960 ). However, this relatively shallow and weak oceanic convection is not dominant in coastal or continental boundary layers, which likely explains its underrepresentation in BR03 , BR09 , and TH10 , which consist of data mostly from midlatitude and subtropical land

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Rachel C. Zelinsky, Chidong Zhang, and Chuntao Liu

-interaction theory emphasizes the role of feedbacks among boundary layer frictional convergence, moisture, and wave dynamics ( Wang et al. 2016 ). These and other theories (e.g., Majda and Stechmann 2009 ; Yang and Ingersoll 2013 ; Fuchs and Raymond 2017 ) explain the propagation and scale selection of the MJO. No theory currently explains why it initiates in the first place or why it initiates over the Indian Ocean most of the time ( Zhang and Ling 2017 ). There are hypotheses on convective initiation of the

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