Tropical Intraseasonal Oscillations in a Simple Nonlinear Model

Bladé, Ileana; Hartmann, Dennis L.

doi:10.1175/1520-0469(1993)050<2922:tioias>2.0.co;2

Cited by 220 publications

(190 citation statements)

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“…This regulatory cycle is likely at work on intraseasonal time scales, but is perhaps much less efficient for a period typical of the Kelvin wave. The development of Kelvin wave convection therefore proceeds without the help of an external thermodynamic driver similar to the discharge-recharge mechanism proposed to explain the MJO periodicity (Bladé and Hartmann 1993).…”

Section: Kelvin Wavesupporting

confidence: 88%

“…Radiative effects of high clouds may enhance the upper-tropospheric cooling (Hu and Randall 1994), promote the greenhouse effect (Stephens et al 2004), or simply induce an energy transfer from the ocean to the atmosphere (Sobel and Gildor 2003). A locally regulated thermodynamic cycle would be a key that controls the MJO period (Bladé and Hartmann 1993), since the interaction between the Kelvin and ER waves discussed above could explain the propagation of the MJO, but not its periodicity. …”

Section: Madden-julian Oscillationmentioning

confidence: 99%

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A 9-season TRMM Observation of the Austral Summer MJO and Low-frequency Equatorial Waves

Masunaga

2009

Journal of the Meteorological Society of Japan

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A long-term observation from the Tropical Rainfall Measuring Mission (TRMM) is analyzed to investigate the Madden-Julian Oscillation (MJO), Kelvin wave, and equatorial Rossby (ER) wave in austral summer seasons. TRMM Precipitation Radar (PR) and Visible/Infrared Scanner (VIRS) measurements are jointly used to clarify convective progression associated with individual modes of the tropical oscillations. Variability in the dynamic and thermodynamic environment involving sea surface temperature (SST), column relative humidity (CRH), and moisture convergence is also examined. A sea surface warming is found to precede the peak MJO convection by ~10 days, while a prior SST increase is not as evident for the Kelvin and ER waves. Moisture convergence and CRH exhibit a horseshoe-like pattern in the composite MJO map, constituted of a pair of off-equatorial maxima and a weak equatorial peak. The Kelvin wave has a moist anomaly on the equator leading the convective peak as theoretically expected, while the moist anomaly also extends poleward without being accompanied by moisture convergence. Moisture convergence leads CRH by a day or two for the Kelvin and ER waves. Moisture convergence is, in contrast, virtually concurrent with CRH for the MJO. The correlation between CRH and deep stratiform coverage is diverse among the three modes of the tropical oscillations. Shallow cumulus and cumulus congestus lead the MJO convective peak by ~1 day, followed by lingering non-precipitating high clouds. ER wave convection is led by moisture convergence but lagged by CRH. The convective progression appears not to proceed in a monotonic way for the ER wave.A possible mechanism to explain MJO propagation is discussed as suggested by a synthesis of the present findings. The Kelvin wave guides the eastward migration of MJO convection onset over the Indian Ocean. The role of the Kelvin wave in MJO propagation diminishes as the MJO enters the west Pacific with the convective area shifting away from the equator. Instead, the Kelvin wave convective heating induces poleward moisture transport and moistens the off-equatorial mid troposphere. The resultant moist anomaly is hypothesized to help trigger the MJO convective burst upon the arrival of ER wave disturbances. Such cooperative processes involving the Kelvin and ER waves could act as a driving engine of some, if not all, MJO episodes.

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Section: Kelvin Wavesupporting

confidence: 88%

Section: Madden-julian Oscillationmentioning

confidence: 99%

A 9-season TRMM Observation of the Austral Summer MJO and Low-frequency Equatorial Waves

Masunaga

2009

Journal of the Meteorological Society of Japan

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“…convergence, the boundary layer moisture convergence, the surface heat flux anomaly (latent plus sensible) due to wind variation, the local moisture tendency, the radiative heating, and the surface heat flux anomaly due to SST variation. These six components have been emphasized by wave-CISK (e.g., Lau and Peng 1987;Chang and Lim 1988;Hendon 1988;Dunkerton and Crum 1991), frictional wave-CISK (e.g., Wang and Rui 1990;Salby et al 1994), windinduced surface heat exchange (WISHE; e.g., Emanuel 1987;Neelin et al 1987), charge-discharge (e.g., Bladé and Hartmann 1993;Hayashi and Golder 1997;Majda 2006, 2007), cloud-radiation interaction (e.g., Raymond 2001;Lee et al 2001;Bony and Emanuel 2005;Zurovac-Jevtić et al 2006;Lin et al 2007), and air-sea coupling (e.g., Flatau et al 1997;Wang and Xie 1998;Waliser et al 1999) theories, respectively. These mechanisms also interact with one another, with the vertical heating structure (e.g., Mapes 2000; Majda and Shefter 2001;Haertel and Kiladis 2004;Khouider and Majda 2006), and with nonlinear effects of subscale perturbations (e.g., Majda and Klein 2003;Moncrieff 2004;Biello andMajda 2005, 2006;Majda 2007).…”

Section: Summary and Discussionmentioning

confidence: 99%

The Impacts of Convective Parameterization and Moisture Triggering on AGCM-Simulated Convectively Coupled Equatorial Waves

et al. 2008

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This study examines the impacts of convective parameterization and moisture convective trigger on convectively coupled equatorial waves simulated by the Seoul National University (SNU) atmospheric general circulation model (AGCM). Three different convection schemes are used, including the simplified Arakawa-Schubert (SAS) scheme, the Kuo (1974) scheme, and the moist convective adjustment (MCA) scheme, and a moisture convective trigger with variable strength is added to each scheme. The authors also conduct a "no convection" experiment with deep convection schemes turned off. Space-time spectral analysis is used to obtain the variance and phase speed of dominant convectively coupled equatorial waves, including the Madden-Julian oscillation (MJO), Kelvin, equatorial Rossby (ER), mixed Rossby-gravity (MRG), and eastward inertio-gravity (EIG) and westward inertio-gravity (WIG) waves.The results show that both convective parameterization and the moisture convective trigger have significant impacts on AGCM-simulated, convectively coupled equatorial waves. The MCA scheme generally produces larger variances of convectively coupled equatorial waves including the MJO, more coherent eastward propagation of the MJO, and a more prominent MJO spectral peak than the Kuo and SAS schemes. Increasing the strength of the moisture trigger significantly enhances the variances and slows down the phase speeds of all wave modes except the MJO, and usually improves the eastward propagation of the MJO for the Kuo and SAS schemes, but the effect for the MCA scheme is small. The no convection experiment always produces one of the best signals of convectively coupled equatorial waves and the MJO.

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“…Convective build-up is connected with the moistening process in the lower troposphere. Several theories have been proposed for the MJO moistening process, including frictional moisture convergence in the boundary layer (Wang 1988;Hendon and Salby 1994), and recharge process on the time-scale of the radiative-convective feedback (Bladé and Hartmann 1993;Hu and Randall 1994).…”

Section: Introductionmentioning

confidence: 69%

Role of Maritime Continent Convection during the Preconditioning Stage of the Madden-Julian Oscillation Observed in CINDY2011/DYNAMO

Kubota

Yoneyama

Hamada

et al. 2015

Journal of the Meteorological Society of Japan

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We investigated the role of Sumatra Island convection over the maritime continent during the preconditioning stage of the Madden-Julian Oscillation (MJO) using intensive observations of CINDY2011/DYNAMO and HARIMAU2011. CINDY2011/DYNAMO and HARIMAU2011 were conducted over the Indian Ocean from October 2011 to January 2012 and Sumatra Island, Indonesia in December 2011. Both observation datasets covered the preconditioning stage of the MJO in December 2011. We found that convection was activated over the Sumatra Island with diurnal cycle associated with the moist air mass, which originated from a tropical depression generated in the South China Sea. Then, two-day period disturbances that propagated westward to the central Indian Ocean were coupled with the diurnal cycle of convection over the Sumatra Island. The structure of the two-day period disturbances was consistent with that of westward propagating inertio-gravity waves. When the westward propagating disturbances arrived over the central Indian Ocean, low-level moisture advection was excited. Moistening process was promoted in Gan Island over the central Indian Ocean, which had a two-day period. After the favorable condition of large-scale convection was established, the MJO was activated in the central Indian Ocean. The two-day period westward disturbances were organized when large-scale moisture convergence became positive in Sumatra Island and continued until a strong low-level westerly wind of the active phase of the MJO was formed.

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Tropical Intraseasonal Oscillations in a Simple Nonlinear Model

Cited by 220 publications

References 0 publications

A 9-season TRMM Observation of the Austral Summer MJO and Low-frequency Equatorial Waves

A 9-season TRMM Observation of the Austral Summer MJO and Low-frequency Equatorial Waves

The Impacts of Convective Parameterization and Moisture Triggering on AGCM-Simulated Convectively Coupled Equatorial Waves

Role of Maritime Continent Convection during the Preconditioning Stage of the Madden-Julian Oscillation Observed in CINDY2011/DYNAMO

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