Detecting and Tracking Coastal Precipitation in the Tropics: Methods and Insights into Multiscale Variability of Tropical Precipitation

Abstract

<jats:title>Abstract</jats:title> <jats:p>We propose an algorithm to detect and track coastal precipitation systems and we apply it to 18 years of the high-resolution (8 km and 30 min) Climate Prediction Center CMORPH precipitation estimates in the tropics. Coastal precipitation in the Maritime Continent and Central America contributes to up to 80% of the total rainfall. It also contributes strongly to the diurnal cycle over land with the largest contribution from systems lasting between 6 and 12 h and contributions from longer-lived systems peaking later in the day. While the diurnal cycle of coastal precipitation is more intense over land in the summer hemisphere, its timing is independent of seasons over both land and ocean because the relative contributions from systems of different lifespans are insensitive to the seasonal cycle. We investigate the hypothesis that coastal precipitation is enhanced prior to the arrival of the Madden–Julian oscillation (MJO) envelope over the Maritime Continent. Our results support this hypothesis and show that, when considering only coastal precipitation, the diurnal cycle appears reinforced even earlier over islands than previously reported. We discuss the respective roles of coastal and large-scale precipitation in the propagation of the MJO over the Maritime Continent. We also document a shift in diurnal cycle with the phases of the MJO, which results from changes in the relative contributions of short-lived versus long-lived coastal systems.</jats:p>

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

“…Previous studies have shown the importance of MCS lifetime on contribution to rainfall (e.g., Coppin et al ., 2020; Feng et al ., 2021; Roca et al ., 2014). Roca et al .…”

“…Previous studies have shown the importance of MCS lifetime on contribution to rainfall (e.g., Coppin et al, 2020;Feng et al, 2021;Roca et al, 2014) also suggested propagation distance has an impact on rainfall contribution, with MCSs propagating more than 250 km having the largest contribution. Also, fast-moving storms cause more problems for meteorological agencies, in that they can arrive at a location quickly without much warning; so, understanding these systems is important.…”

“…This earlier peak over land is associated with intensified surface heating and insolation, which in turn drives a strong land–sea breeze circulation (Birch et al ., 2016) and is particularly evident in regions where there is a strong diurnal cycle in rainfall; for example, over Sumatra, Borneo, and New Guinea (Peatman et al ., 2014). Part of this spatial variability is associated with an increase in longer lived systems over coastal regions when precipitation is favoured (Coppin et al ., 2020).…”