Upper Ocean Response to the Atmospheric Cold Pools Associated With the Madden‐Julian Oscillation

Pei, Suyang; Shinoda, Toshiaki; Soloviev, Alexander; Lien, Ren‐Chieh

doi:10.1029/2018gl077825

Cited by 16 publications

(31 citation statements)

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“…Fresh‐water and momentum fluxes during an MJO active phase substantially affect upper‐ocean stratification and surface currents. Widespread freshening from rainfall stabilizes the upper ocean, yielding a shallower salt‐stratified layer over a deeper temperature‐stratified layer (e.g., Drushka et al, 2016; Pei et al, 2018) separated by an isothermal “barrier layer” (Sprintall & Tomczak, 1992) that resists mixing both from above and below. Sufficiently strong barrier layers can inhibit vertical mixing of MJO‐driven surface momentum fluxes, limiting them to the uppermost ocean, where they may drive anomalous surface currents that persist long after the wind forcing subsides, limiting further upper‐ocean stabilization and warming before the next MJO event (X. Hong, Reynolds, et al, 2017; Moum et al, 2016).…”

Section: Recent Progress In Understanding Modeling and Predicting Tmentioning

confidence: 99%

Fifty Years of Research on the Madden‐Julian Oscillation: Recent Progress, Challenges, and Perspectives

et al. 2020

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Since its discovery in the early 1970s, the crucial role of the Madden‐Julian Oscillation (MJO) in the global hydrological cycle and its tremendous influence on high‐impact climate and weather extremes have been well recognized. The MJO also serves as a primary source of predictability for global Earth system variability on subseasonal time scales. The MJO remains poorly represented in our state‐of‐the‐art climate and weather forecasting models, however. Moreover, despite the advances made in recent decades, theories for the MJO still disagree at a fundamental level. The problems of understanding and modeling the MJO have attracted significant interest from the research community. As a part of the AGU's Centennial collection, this article provides a review of recent progress, particularly over the last decade, in observational, modeling, and theoretical study of the MJO. A brief outlook for near‐future MJO research directions is also provided.

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Section: Recent Progress In Understanding Modeling and Predicting Tmentioning

confidence: 99%

Fifty Years of Research on the Madden‐Julian Oscillation: Recent Progress, Challenges, and Perspectives

et al. 2020

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“…SST variations in response to intense air‐sea interaction processes associated with atmospheric cold pools (ACPs) are of growing interest, but our understanding is still limited (Anderson & Riser, 2014; de Szoeke et al., 2017; Pei et al., 2018). Using high vertical resolution temperature (∼10 cm) measurements in the near‐surface layer, Anderson and Riser (2014) reported a reduction in the upper‐layer temperature of the magnitude of ∼0.1°C in response to rainfall events in the tropical western pacific.…”

Section: Introductionmentioning

confidence: 99%

Atmospheric Cold Pools and Their Influence on Sea Surface Temperature in the Bay of Bengal

et al. 2021

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Recent observations show that atmospheric cold pool (ACP) events are plentiful in the Bay of Bengal (BoB) during summer (May–September) and fall (October–November) and that these events can significantly modify local air‐sea interaction processes on sub‐daily time scales. In this study, we examine whether the magnitude of sea surface temperature (SST) drop associated with ACP events shows any diurnal variability during summer and fall. For this purpose, we use moored buoy data with a 10‐min temporal resolution at 8°, 12°, and 15°N along 90°E and a one‐dimensional mixed layer (ML) model. The analysis shows a reduction in SST (ΔSST) due to ACPs in the BoB during summer and fall, with a maximum magnitude of ΔSST during the afternoon (1200–1600 LST). However, the maximum magnitude of ΔSST during the afternoon is a factor of two higher during fall (∼−0.14°C) than summer (∼−0.07°C). Analysis based on observations and ACP sensitivity experiments indicates that the shallow daytime thermocline and associated thin surface ML is the primary factor regulating the day to night difference in ΔSST associated with ACPs. The presence of this shallow daytime thermocline and thin ML amplifies the effects on SST of net surface heat loss and entrainment of cold sub‐surface water associated with enhanced ACP wind speeds.

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“…The air within cold pools is also strongly affected by the recovery to ambient conditions. Cold pool recovery processes reflect the combined influences of surface fluxes from possibly cooled ocean surfaces (Pei et al, ) and entrainment and subsidence at the cold pool top (e.g., de Szoeke, ). While these processes are also important, they are not the focus of this study, which is on the impact of the initial convective downdrafts.…”

Section: Introductionmentioning

confidence: 99%

Moisture Distributions in Tropical Cold Pools From Equatorial Indian Ocean Observations and Cloud‐Resolving Simulations

et al. 2018

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The near-surface characteristics of approximately 300 convective cold pools over the equatorial Indian Ocean are studied using surface meteorological variables from two equatorial Indian Ocean sites, radar imagery, and constrained cloud-resolving simulations. The observed temperature drop at cold pool onset is typically accompanied by a drying and a decrease in moist static energy, signifying air transport from above the boundary layer through precipitation-induced downdrafts. The decrease in the surface water vapor mixing ratio is more pronounced for stronger temperature drops. Composites reveal a slight enhancement in moisture coincident with a slight enhancement in temperature prior to the cold pool frontal temperature drop. The slight enhancements occur prior to a gust of increased surface winds, suggesting that the immediate cause is wind convergence. A statistical analysis combined with a focus on selected case studies is consistent with a view that the strongest cold pools occur in intermediate column water vapor paths with drier midtropospheres. Such conditions are more likely to occur during convectively suppressed phases of the Madden-Julian Oscillation, when cold pool mesoscale organization facilitates the ability of cumulus congestus to reach the middle troposphere. Cold pools thus help explain why tropical cumulus congestus are common. Cloud-resolving simulations capture realistic rain rates and surface wind changes (and thereby surface fluxes). The evolution in the model near-surface moisture field is unrealistic, however, with an erroneous moisture enhancement inside the cold pool edge that is attributed to rain evaporation. This supports a further focus on the model representation of cold pool frontal dynamics and mixing.Plain Language Summary Cold pools of air develop near the surface over the ocean when it rains. This colder air can move along the surface because it is denser and cause new raining clouds to form. They help modify the types of clouds and convection present over the tropical oceans, and their depiction in climate models may help improve climate model simulations of tropical climate. In this study we use observations of cold pools, combined with radar imagery, to confirm that cold pools are more pronounced when the middle of the atmosphere, between 2 and 5 km, is also drier. Cold pools, because they help support updrafts, can also help explain why seemingly isolated clouds reaching ∼5 km, are relatively common in the Tropics. Modeling simulations have instead focused on how anomalous moisture near the surface from previous convection, through, for example, rain evaporation, may spawn more convection. We find that in one cloud-resolving simulation, the rain evaporation is too much, leading to an unrealistic moisture distribution. This may explain why to date the understanding of cold pool processes through models and observations have not always agreed.

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Upper Ocean Response to the Atmospheric Cold Pools Associated With the Madden‐Julian Oscillation

Cited by 16 publications

References 50 publications

Fifty Years of Research on the Madden‐Julian Oscillation: Recent Progress, Challenges, and Perspectives

Fifty Years of Research on the Madden‐Julian Oscillation: Recent Progress, Challenges, and Perspectives

Atmospheric Cold Pools and Their Influence on Sea Surface Temperature in the Bay of Bengal

Moisture Distributions in Tropical Cold Pools From Equatorial Indian Ocean Observations and Cloud‐Resolving Simulations

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