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- Title
A Local-to-Large Scale View of Maritime Continent Rainfall: Control by ENSO, MJO, and Equatorial Waves.
- Authors
Peatman, Simon C.; Schwendike, Juliane; Birch, Cathryn E.; Marsham, John H.; Matthews, Adrian J.; Yang, Gui-Ying
- Abstract
The canonical view of the Maritime Continent (MC) diurnal cycle is deep convection occurring over land during the afternoon and evening, tending to propagate offshore overnight. However, there is considerable day-to-day variability in the convection, and the mechanism of the offshore propagation is not well understood. We test the hypothesis that large-scale drivers such as ENSO, the MJO, and equatorial waves, through their modification of the local circulation, can modify the direction or strength of the propagation, or prevent the deep convection from triggering in the first place. Taking a local-to-large scale approach, we use in situ observations, satellite data, and reanalyses for five MC coastal regions, and show that the occurrence of the diurnal convection and its offshore propagation is closely tied to coastal wind regimes that we define using the k-means cluster algorithm. Strong prevailing onshore winds are associated with a suppressed diurnal cycle of precipitation, while prevailing offshore winds are associated with an active diurnal cycle, offshore propagation of convection, and a greater risk of extreme rainfall. ENSO, the MJO, equatorial Rossby waves, and westward mixed Rossby–gravity waves have varying levels of control over which coastal wind regime occurs, and therefore on precipitation, depending on the MC coastline in question. The large-scale drivers associated with dry and wet regimes are summarized for each location as a reference for forecasters. Significance Statement: Extreme precipitation can be life-threatening in the Maritime Continent region, for example, due to flash floods and landslides. The main form of variability of convective storms is the diurnal cycle, but this can be modulated by large-scale weather drivers. By quantifying the effect of these drivers on local-scale weather regimes for a range of Maritime Continent locations, we identify which drivers are most important (and in which phase) to consider when understanding the local risk of extreme rainfall. Given that these large-scale drivers may be forecast with greater skill than is possible for quantitative precipitation forecasts, this study provides crucial extra information for forecasters to aid prediction of life-threatening weather conditions.
- Subjects
EL Nino; THUNDERSTORMS; WEATHER; ROSSBY waves; PRECIPITATION forecasting; LANDSLIDES; WEATHER forecasting
- Publication
Journal of Climate, 2021, Vol 34, Issue 22, p8933
- ISSN
0894-8755
- Publication type
Article
- DOI
10.1175/JCLI-D-21-0263.1