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Naoko Sakaeda, Scott W. Powell, Juliana Dias, and George N. Kiladis

1. Introduction Intraseasonal variability in the atmosphere bridges an important time scale between climate and weather. A key phenomenon that occurs on intraseasonal time scales in the tropics is the Madden–Julian oscillation (MJO; Madden and Julian 1971 , 1972 ). The MJO is known to influence a wide range of spatial and temporal weather and climate phenomena ( Lau and Waliser 2011 ), including the diurnal cycle of rain, which is the focus of this study. The diurnal cycle in precipitation is

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Wen-wen Tung, Dimitrios Giannakis, and Andrew J. Majda

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

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Kunio Yoneyama, Chidong Zhang, and Charles N. Long

decadal time scales . Quart. J. Roy. Meteor. Soc. , 134 , 1337 – 1351 . Benedict , J. J. , and D. A. Randall , 2007 : Observed characteristics of the MJO relative to maximum rainfall . J. Atmos. Sci. , 64 , 2332 – 2354 . Benedict , J. J. , and D. A. Randall , 2009 : Structure of the Madden–Julian oscillation in the superparameterized CAM . J. Atmos. Sci. , 66 , 3277 – 3296 . Brown , R. G. , and C. Zhang , 1997 : Variability of midtropospheric moisture and its effect on cloud

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Jean-Philippe Duvel

more TDs. As mentioned above, one may thus consider that large-scale cyclonic vorticity perturbation related to the MJO does not promote the intensification of existing TDs. Instead, the cyclonic shear of the zonal low-level jet generated by the MJO could be unstable and multiply the number of TD initiations. During the Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011 (CINDY2011)–DYNAMO experiment ( Yoneyama et al. 2013 ), many tropical depressions were observed

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Weixin Xu, Steven A. Rutledge, Courtney Schumacher, and Masaki Katsumata

1. Introduction The Madden–Julian oscillation (MJO) ( Madden and Julian 1971 , 1972 ) has broad impacts on the global weather and climate [see Zhang (2005 , 2013) and references therein] such as monsoon rainfall variability, storm tracks, tropical cyclone frequency, tornado outbreaks, ENSO, intertropical convergence zone (ITCZ) convection, and extratropical climate modes. Despite decades of study, the MJO is still not well understood and therefore MJO prediction skill is limited, especially

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

on rain variability with multiple variables: reflectivity Z h ; specific differential phase K dp ; attenuation of the horizontally polarized radar signal A h ; and differential reflectivity Z dr instead of one: horizontally polarized radar reflectivity Z h ( Seliga and Bringi 1976 ; Sachidananda and Zrnić 1987 ; Carey and Rutledge 2000 ; Carey et al. 2000 ; BC01 ; Schuur et al. 2001 ; Ryzhkov et al. 2005a , b , c ; Kumjian 2013a , b , c ). The quantities K dp , A h , Z dr , Z h

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Samson M. Hagos, Zhe Feng, Casey D. Burleyson, Chun Zhao, Matus N. Martini, and Larry K. Berg

1. Introduction Despite decades of work, simulating the Madden–Julian oscillation (MJO; Madden and Julian 1971 , 1972 ) in climate models and understanding the instabilities that drive it remain a significant challenge. However, some progress has been reported in recent years. For example, Hung et al. (2013) found that, in general, models participating in phase 5 of the Coupled Model Intercomparison Project (CMIP5) perform better than those that participated in phase 3 of CMIP (CMIP3) in

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Adam Sobel, Shuguang Wang, and Daehyun Kim

1. Introduction Though the Madden–Julian oscillation (MJO) was first discovered over four decades ago ( Madden and Julian 1971 , 1972 ; Julian and Madden 1981 ), its basic dynamics remain unexplained to the collective satisfaction of the research community. There is no fundamental agreement on what kind of dynamical entity the MJO is. We have been pursuing the notion that the MJO is a moisture mode. At the broadest level, we mean by this a mode of variability that would not exist in any

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

1. Introduction The discovery of 40–50-day oscillations in the zonal winds at 850 and 150 hPa in the tropical atmosphere over 45 years ago has incited a rich interest in researching and characterizing the Madden–Julian oscillation (MJO; Madden and Julian 1971 , 1972 ) (important acronyms in this paper are also listed and defined in the appendix ). The MJO influences patterns of variability of lower- and upper-tropospheric winds, humidity, and temperature on 30–90-day time scales, and

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

theory predicted, nonlinear WISHE is still viable ( Sobel et al. 2010 ). Moisture is also integral to the moisture-mode hypothesis (e.g., Raymond 2001 ; Sobel and Maloney 2012 , 2013 ). Feedbacks among surface fluxes, radiation, and cloud processes can conspire to maintain free-tropospheric moisture and enhance convection against the drying and dissipating effects of vertical and horizontal advection (e.g., Sobel et al. 2001 ). Despite decades of research, most GCMs fail to simulate MJO events

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