The Influences of Convectively Coupled Kelvin Waves on Multiscale Rainfall Variability over the South China Sea and Maritime Continent in December 2016

Chen, Wei‐Ting; Hsu, Shih-Pei; Tsai, Wayne Yuan-Huai; Sui, C.-H.

doi:10.1175/jcli-d-18-0471.1

Cited by 10 publications

(6 citation statements)

References 57 publications

(70 reference statements)

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“…Both Baranowski et al (2016) and Sakaeda et al (2020) respectively show that the diurnal cycle is intensified by Kelvin waves and Rossby waves, the latter especially over the ocean. Chen et al (2019) further emphasise the intensification of the diurnal cycle over land by Kelvin waves. Ferrett et al (2020) show that equatorial wave activity is linked to extreme rainfall in the region.…”

Section: Introductionmentioning

confidence: 94%

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Impact of the Madden–Julian oscillation and equatorial waves on tracked mesoscale convective systems over southeast Asia

Crook,

Morris,

Fitzpatrick

et al. 2024

Quart J Royal Meteoro Soc

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Southeast Asia is a region dominated by high‐impact weather, but numerical weather prediction here is a challenge owing to the complex orography and interactions between small‐ and large‐scale phenomena. Localised mesoscale convective systems (MCSs) can produce intense precipitation. Here, we track MCSs over a 5‐year period in Himawari satellite data, characterise the distribution of MCSs in the region, and investigate how they are modulated by the Madden–Julian oscillation (MJO) and equatorial waves. Between 10°S and 10°N in southeast Asia, MCSs account for 45–70% of the precipitation during boreal extended winter (November–April). Over most of the region, the fractional MCS contribution to rainfall is higher than average on days with extreme rainfall (>55%). Long‐lived (>12 hr) MCSs contribute disproportionately, providing 85% of the rainfall despite comprising only 34% of all MCSs. Variability in MCS rainfall accounts for >50% of the total rainfall variability during an MJO cycle, mostly due to larger numbers of MCSs in convectively active MJO phases. Variations in MCS size and mean rain rate due to shifts in the stratiform proportion provide compensating effects. In the west of the region, a shift to faster moving MCSs in active MJO phases and slower moving MCSs in inactive phases resulted in fast‐moving MCSs having the greatest impact on the MJO‐associated variability. Variability is larger in the west than in the east. Equatorial Kelvin waves modulate MCS rainfall, with MCSs accounting for 20–50% of local rainfall anomalies. This variability is again enhanced in the west. By contrast, rainfall anomalies due to westward‐propagating mixed Rossby–gravity waves and Rossby‐1 waves are dominated by tropical‐cyclone‐related rainfall. Skill at local scales may be extracted from forecasts of subseasonal drivers such as the MJO and Kelvin waves, by understanding how these modulate the number and characteristics of MCSs.

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Section: Introductionmentioning

confidence: 94%

“…Chen et al . (2019) further emphasise the intensification of the diurnal cycle over land by Kelvin waves.…”

Section: Introductionmentioning

confidence: 99%

Impact of the Madden–Julian oscillation and equatorial waves on tracked mesoscale convective systems over southeast Asia

Crook,

Morris,

Fitzpatrick

et al. 2024

Quart J Royal Meteoro Soc

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“…Convectively coupled Kelvin waves (KWs) are a dominant force in tropical subseasonal precipitation variability (Murata et al 2006;Wang and Fu 2007;Sinclaire et al 2015;Chen et al 2019;Latos et al 2021). These waves exert significant influence on global weather extremes and climate variability across multiple scales (Flatau et al 2003;Bessafi and Wheeler 2006;Straub et al 2006;Roundy 2008;Lawton and Majumdar 2023;Cheng et al 2023).…”

Section: Introductionmentioning

confidence: 99%

Response of convectively coupled Kelvin waves to surface temperature forcing in aquaplanet simulations

Chien,

Kim

2024

Preprint

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This study investigates changes in the propagation and maintenance of convectively coupled Kelvin waves (KWs) in response to surface warming. We use a set of three aquaplanet simulations made with the Community Atmospheric Model version 6 by varying the sea surface temperature boundary conditions, representing the current climate, a warmer (+4K), and a cooler (-4K) climate. Results show that KWs accelerate at the rate of about 7.1%/K and their amplitudes decrease by 4.7%/K. The dampening of KWs with warming is found to be associated with a weakening of the internal thermodynamic feedback between diabatic heating and temperature anomalies that generates KW eddy available potential energy (EAPE). The phase speed of KWs closely matches that of the second baroclinic mode KW in -4K, while the phase speed of KWs is approximately that of the first baroclinic mode KW in +4K. Meanwhile, the coupling between the two baroclinic modes weakens with warming. We hypothesize that in -4K, as the first and second modes are strongly coupled, KWs destabilize by positive EAPE generation within the second mode, and they propagate slower following the second mode KW phase speed. In +4K, as the first and second modes decouple, KWs are damped by negative EAPE generation within the first mode, and they propagate faster following the first mode KW phase speed.

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“…Studies show a considerable variance of tropical convection is found to be controlled by convectively coupled equatorial waves (Roundy and Frank, 2004;Kiladis et al, 2009). In the MC, for instance, the convectively coupled Kelvin waves in the lower level of the troposphere have an important impact on rainfall variability in the MC (Chen et al, 2019). Ferrett et al (2020) show various extreme rainfall events in southeast Asia are linked to various modes of the equatorial wave.…”

Section: Introductionmentioning

confidence: 99%

Equatorial Rossby waves on cold surge days and their impact on rainfall

Diong¹,

Xavier

Woolnough

et al. 2023

Quart J Royal Meteoro Soc

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This study aims to understand the process that determines the regional rainfall distribution in the equatorial South China Sea (SCS) and its surrounding during the cold surge (CS) days by looking at the different vorticity phases of active equatorial Rossby (R1) waves and the dynamics of the CSs related to the R1 wave. The CS can be thought of as an anticyclonic outflow from midlatitude and behaves like a dispersive group of R1 meridional modes. From the study, it shows the vorticity of the R1 wave arranges itself in such a way that the anticyclonic phase is located to the west and the cyclonic phase is located to the east of the cold CS axis. The CS winds in the equatorial SCS occur early, remain longer, and possess a larger zonal component in the active cyclonic phase compared with the active anticyclonic phase. During the active cyclonic vorticity phase, the rainfall anomalies pattern in the equatorial SCS changes from a “tick‐mark‐like” pattern to a “V‐shape” pattern as a consequence of the westward propagation of the wave. The probability of rainfall increases near the centre of cyclonic vorticity, but for anticyclonic vorticity the probability increases in the southern part of the vorticity centre. There is both increased (decreased) intensity and probability of extreme rainfall events during the active cyclonic (anticyclonic) vorticity phase on CS days. Overall, the rainfall anomalies are largely dominated by changes in the intensity on wet days rather than the number of wet days. These changes indicate the roles of the R1 wave vorticity phase in the rainfall distribution during CS days. The timing of enhancement and suppression of rain will provide additional valuable information to help improve forecast extreme weather events.

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The Influences of Convectively Coupled Kelvin Waves on Multiscale Rainfall Variability over the South China Sea and Maritime Continent in December 2016

Cited by 10 publications

References 57 publications

Impact of the Madden–Julian oscillation and equatorial waves on tracked mesoscale convective systems over southeast Asia

Impact of the Madden–Julian oscillation and equatorial waves on tracked mesoscale convective systems over southeast Asia

Response of convectively coupled Kelvin waves to surface temperature forcing in aquaplanet simulations

Equatorial Rossby waves on cold surge days and their impact on rainfall

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