Analysis of Spatial and Seasonal Differences in the Diurnal Rainfall Cycle over Sumatera Revealed by 17-Year TRMM 3B42 Dataset

Abstract

We analyzed 3-hourly Tropical Rainfall Measuring Mission multi-satellite analysis (TRMM 3B42) version-7 data for the 17year period 1998−2014 to investigate seasonal and geographic characteristics of the diurnal rainfall cycle (DRC) over Sumatera, Indonesia. Dividing Sumatera into north, central, and south regions approximately perpendicular to the west coast, we point out for the first time early-afternoon initiation of daily rainfall not only in the Barisan Mountains but also in the east-coastal small islands (ECSIs) such as Bangka and Belitung. Westward and eastward migrations of rainfall areas from the Barisan Mountains are varied with seasons and regions, with the most remarkable being westward during September-October-November (SON) in the central region and the least remarkable occurring during June-July-August (JJA) in the southern region. In the central region, the DRC reaches a distance of ~700 km off the west coast during SON and of only 200 km during March-April-May (MAM). The other westward migrations from the ECSIs in the central and southern regions (except for JJA) have been confirmed by 5-year hourly Multi-functional Transport Satellite-1R (MTSAT-1R) cloud-top data. The results shown in this paper suggest that the rainfall distribution with respect to coastal distance, varying geographically and seasonally.

The Diurnal Cycle of Rainfall and Deep Convective Clouds Around Sumatra and the Associated MJO‐Induced Variability During Austral Summer in Himawari‐8

“…The DC of the satellite-derived RPA frequency over land and ocean shows an inhomogeneous spatial distribution of cloud populations during the Austral summer DJF between 2016 and 2021 (Figure 3), which is in agreement with previous findings based on satellite-based rainfall by Qian (2008), Kamimera et al (2012), As-syakur et al ( 2019), and Mori et al (2004). Our findings complement previous studies (As-syakur et al, 2019;Mori et al, 2004;Qian, 2020;Vincent & Lane, 2017) by providing an enhanced description of diurnally driven convection patterns and cloud physical properties over Sumatra with unprecedented fine-scale spatial and temporal detail as well as broad spatial extent.…”

“…Over the land and coastal regions, the diurnal cloud cycle is driven by convective heating at the lower levels of the troposphere and exhibits a maximum at night (Vincent & Lane, 2017). The land‐sea temperature contrast generates seaward pressure gradients along the coasts of Sumatra, driving inland propagation during the afternoon (As‐syakur et al., 2019; Mori et al., 2004). The DC of the convective cloud has been attributed to a thermodynamic response to a strong DC of the land surface temperature.…”

Diurnal variation of precipitation from the perspectives of precipitation amount, intensity and duration over Sumatra from rain gauge observations

“…About ten stations (5%) have an early‐morning peak (0400–1000 LST), and most of these stations are observed in the east‐coastal small islands such as Bangka, Belitung, and Riau Islands. This result is consistent to that obtained using 3‐hourly TRMM 3B42 data (As‐syakur et al ., 2019).…”

“…Recently, As‐syakur et al . (2019) re‐investigated the rainfall distribution over Sumatra concerning topography and coastal distances using 3‐hourly Tropical Rainfall Measuring Mission multi‐satellite analysis (TRMM 3B42) data during year period 1998–2014. The position of Sumatra Island which is almost perpendicular to cloud propagation from the Indian Ocean, and existence of mountains, block the movement of clouds from the Indian Ocean.…”

“…While there have been some studies on the diurnal cycle of rainfall in Sumatra, such studies are mainly based on the satellite measurement (Mori et al ., 2004; Sakurai et al ., 2005; As‐syakur et al ., 2019), and ground measurement for specific locations and campaign periods (e.g., Wu et al ., 2003; Marzuki et al ., 2016). Despite the usefulness of satellite‐based precipitation estimates in climate studies, the satellite data uncertainty is still considerable (Tian and Peters‐Lidard, 2010).…”