Diurnal Cycle of Tropical Oceanic Mesoscale Cold Pools

Garg, Piyush; Nesbitt, Stephen W.; Lang, Timothy J.; Priftis, George

doi:10.1175/jcli-d-20-0909.1

Cited by 3 publications

(11 citation statements)

References 85 publications

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“…This afternoon peak in the frequency of cold pools is also found by Garg et al. (2021) based on their cold pools that are identified from buoys in global ocean basins.…”

Section: Methodssupporting

confidence: 81%

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The Observed Effects of Cold Pools on Convection Triggering and Organization During DYNAMO/AMIE

Sakaeda

Torri

2023

JGR Atmospheres

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Cold pools that form from existing convection can generate new clouds nearby, a process that has been suggested to contribute to cloud organization. However, some disagreement exists on the role of cold pools in cloud organization over tropical oceans, and much remains to be understood on how this role depends on the state of large‐scale disturbances such as the Madden‐Julian Oscillation (MJO). This study addresses this question by examining the intraseasonal variability in the properties of cold pools and their effects on convection triggering using observations. The unique set of surface meteorology data and ground‐based radars deployed during the DYNAMO/AMIE field campaign are used to identify cold pools and the associated spatiotemporal evolution of rainfall. The results suggest that cold pools enhance rainfall at their expected speed of 3–8 m s−1, which includes the Doppler‐shifting effect by the background wind. The cold pools also enhance rainfall mainly within a 20 km radius, especially in the direction of boundary‐layer vertical wind shear. However, gravity waves appear to contribute predominantly to the propagation of convection over a wider range of distances due to their faster propagation speeds. The interface of convection triggering and propagation at different speeds of cold pools and gravity waves seems to contribute to cloud organization. The effectiveness of cold pools and gravity waves on cloud organization also depends highly on the MJO due to the combined effects of changes in environmental humidity and boundary to lower‐tropospheric wind.

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“…This afternoon peak in the frequency of cold pools is also found by Garg et al. (2021) based on their cold pools that are identified from buoys in global ocean basins.…”

Section: Methodssupporting

confidence: 81%

“…In fact, we find that the frequency and magnitude of cold pools are higher during the day than at night at Addu Atoll (not shown). This afternoon peak in the frequency of cold pools is also found by Garg et al (2021) based on their cold pools that are identified from buoys in global ocean basins.…”

Section: Cold Pool Identificationsupporting

confidence: 59%

The Observed Effects of Cold Pools on Convection Triggering and Organization During DYNAMO/AMIE

Sakaeda

Torri

2023

JGR Atmospheres

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“…In the evening, the cold pool reached close to the coast and travelled along the southeast coast. In a recent study by Garg et al (2021), small cold pools were associated with shallower convection due to relatively drier environmental conditions (less total column water vapour). In view of the drier conditions over the southeast coast as well as the predominant stratiform precipitation type, we can expect a small cold pool to form over these regions in India.…”

Section: Discussionmentioning

confidence: 90%

“…In view of the drier conditions over the southeast coast as well as the predominant stratiform precipitation type, we can expect a small cold pool to form over these regions in India. Thus, the nocturnal precipitation peak offshore of the southeast coast may be related to cold pool movement under the mean environmental flow and their interactions (e.g., Garg et al, 2021; Ruppert & Hohenegger, 2018); however, further research is needed to explain how cold pools interact in this region.…”

Section: Discussionmentioning

confidence: 99%

Climatological characteristics of nocturnal eastward‐propagating diurnal precipitation peak over South India during summer monsoon: Role of monsoon low‐level circulation and gravity waves

Konduru

Matsumoto

Yokoi

et al. 2022

Meteorological Applications

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This study explores the climatological diurnal cycle of precipitation during the summer monsoon season over southeast India using the Tropical Rainfall Measuring Mission (TRMM) 3G68 precipitation product from 2000 to 2014. The primary area of focus is the leeward side of the Western Ghats. We found that the climatological diurnal cycle over this area exhibits a bimodal peak with an afternoon/evening peak near the eastern slopes of the Western Ghats and a nocturnal peak near the southeast coast. This nocturnal peak near the southeast coast propagated offshore in the eastward direction with a phase speed of 18–20 m s−1 and attained an offshore peak in the late night/early morning. The afternoon diurnal peak is associated with daytime convection and propagates eastward over southeast India. The nocturnal peak is due to the convergence of intensified monsoon low‐level westerly winds along the land–sea boundary over the leeward side and supports the nocturnal diurnal peak to cross the coast at late night. The eastward‐propagating gravity waves support further eastward offshore propagation of nocturnal diurnal precipitation patterns. Altogether, the leeward‐side climatological diurnal peaks and diurnal variability in southeast India are controlled by complex precipitation types and their formation mechanisms due to monsoon low‐level westerly winds and gravity waves.

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“…Cold pools occur when evaporatively‐cooled air sinks to the surface and expands horizontally in all directions, resulting in local air temperature and moisture fronts that alter the surrounding environment (Betts & Silva Dias, 1979; Fournier & Haerter, 2019; Glickman & Zenk, 2000; Haerter & Schlemmer, 2018; Lafore & Moncrieff, 1989; Rochetin et al., 2021; Tompkins, 2001). These frontal regions are also accompanied by large variations in wind speed (i.e., the “gust” front) that drive air‐sea fluxes, or surface exchanges of energy between the ocean and the atmosphere (Garg et al., 2020, 2021; Grant & van den Heever, 2016; Gentine et al., 2016; Langhans & Romps, 2015; Ross et al., 2004; Saxen & Rutledge, 1998; Skyllingstad & de Szoeke, 2015; Young et al., 1995).…”

Section: Introductionmentioning

confidence: 99%

Air‐Sea Heat Fluxes Associated With Convective Cold Pools

Wills,

Cronin,

Zhang

2023

JGR Atmospheres

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High‐resolution air‐sea observations collected by a suite of remotely‐piloted uncrewed surface vehicles (USV) provide new insight on surface latent and sensible heat fluxes associated with convective cold pools over the eastern Pacific Intertropical Convergence Zone (ITCZ). Convective cold pools are linked to isolated, heavily precipitating cells over the ocean that yield downdrafts of evaporatively‐cooled air that spreads out horizontally in all directions and are characterized by strong air temperature gradients and horizontal wind speeds. Cold pool frontal signatures are identified based on air temperature depression criteria of −1.5°C in 10 min or less, resulting in a total of 276 events observed within the eastern Pacific ITCZ across 590 total seadays of data from 10 drones over the course of 3 years. Composite analysis reveals enhanced latent and sensible heat fluxes from the ocean to the atmosphere immediately following the frontal passage, and a decomposition of the bulk flux formulas indicates that variations in latent heat flux are largely influenced by the anomalous wind field (i.e., the cold pool gust front) acting on the mean background air‐sea moisture gradient, while variations in sensible heat flux are largely influenced by the mean background wind acting on the anomalous air‐sea temperature gradient (i.e., the cold pool temperature front). High‐frequency variations in wind speed and velocity are further explored in the context of “gustiness” and averaging intervals used in bulk flux algorithms. A case study is also presented for a convective cold pool event captured by a traveling mesoscale network, or mesonet, of USVs.

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Diurnal Cycle of Tropical Oceanic Mesoscale Cold Pools

Cited by 3 publications

References 85 publications

The Observed Effects of Cold Pools on Convection Triggering and Organization During DYNAMO/AMIE

The Observed Effects of Cold Pools on Convection Triggering and Organization During DYNAMO/AMIE

Climatological characteristics of nocturnal eastward‐propagating diurnal precipitation peak over South India during summer monsoon: Role of monsoon low‐level circulation and gravity waves

Air‐Sea Heat Fluxes Associated With Convective Cold Pools

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