Two different mesoscale convective system (MCS) events that produced the heavy rainfall over the Greater Jakarta (GJ) during 15–18 January 2013 period were investigated. The purpose of the present study is to analyze the atmospheric conditions of two different MCSs during the heavy rainfall. Data consist of 3 hourly rainfalls of meteorological stations, infrared satellite, sounding, 6-hourly surface wind and reanalysis data. The first MCS was developed at 16:00 LT on 14 January 2013 over the eastern coast of Sumatra covered an area of 249,732 km² at maximum size, with about 16 h durations. The next MCS was developed at 22:00 LT on 16 January 2013 over the northern coast of the GJ in 9 h of duration, and maximum covered area around 55,829 km². A warmer and moist air was observed on the low-level layer in the evening of 16 January 2013 (prior of second MCS), in comparison to 14 January 2013 event. Combination of both the surface strong wind perturbation and equivalent potential temperature in the second MCS might be contributed to heavy rainfall over the GJ than the first one.

The forest fires smoke event of 7 March 2014 in Sumatera-Indonesia has been simulated using WRF-Chem with the Fire Inventory from NCAR (FINN) fire emissions dataset. These simulations begun 6 March 2014 at 12 UTC until 9 March 2014 at 00 UTC. The results show that the smoke moved to southwest direction covering Riau Province. Moreover, the source of the smoke was also detected from Malaysia which could be seen from both satellite images and the output model. This simulations model have revealed most of the location of forest fires and the spreading of the smoke were properly captured

Flash flooding is an important issue as it has a devastating impact over a short time and in a limited area. However, predicting flash floods is challenging because they are connected to convection systems that rapidly evolve and require a high-resolution forecasting system. In addition, modeling a case study of a mesoscale convective complex (MCC) is the key to improving our understanding of the heavy rainfall systems that trigger flash floods. In this study, we aim at improving modeling skills to simulate a heavy rainfall system related to flash-flood-producing MCCs. We simulated a heavy rainfall event related to a severe flash flood in Luwu, Sulawesi, Indonesia, on 13 July 2020. This flood was preceded by persistent heavy rainfall from 11 to 13 July 2020. In this case, we investigated the role of sea surface temperature (SST) in producing the persistent heavy rainfall over the region. Therefore, we explore the physical and dynamic processes that caused the heavy rainfall using a convection-permitting model with 1 km resolution and an experiment comparing the situation with and without updated SST. The results show that the heavy rainfall was modulated by the development of a pair of MCCs during the night. The pair of MCCs was triggered by a meso-low-pressure system with an anti-cyclonic circulation anomaly over the Makassar Strait and was maintained by the warm front passing between the sea and land over central Sulawesi. This front was characterized by moist–warm and cold–dry low-level air, which may have helped extend the lifetime of the MCCs. The north-westward propagation of the MCCs was due to the interaction between predominantly a south-easterly monsoon and SST anomalies. This study suggested that the long-lived (>10 h) MCCs (>80,000 km² cloud shield) and persistent precipitation are reproduced well in the updated SST scenario in the WRF model. This relatively simple technique in the running model provides a new strategy for improving flash flood forecasting by better predicting rainfall as an input in the hydrological model. Our findings also indicated a long-lived MCC maintained by back-building mechanisms from night to morning inland as an exceptional MCC, which does not correspond to a previous study.

Mesoscale convective complexes (MCC) systems produce a wide variety of severe convective weather such as heavy rainfall. The MCC is a subclass of mesoscale convective systems (MCSs) defining as a convective cloud system that is large, long lived, and exhibits a quasi-circular cloud shield. This study evaluates spatial distributions of heavy rainfall over Java Sea region during wet season conditions; namely, December January February (DJF). Rainfall data set obtained from Tropical Rainfall Measuring Mission (TRMM) measurements for period 1998 - 2013. Heavy rainfall is represented by amount of maximum rainfall. Diurnal cycles of rainfall features present that the development and movement of convective rainfall is mainly related to the land and sea breezes. The evolution of hourly rainfall at 3 hourly intervals, illustrates a clear diurnal variation over Java Sea region. From 22 Local Time (LT) to 10 LT the large average rainfall mainly located in the Java Sea. Then from 13 LT to 19 LT the large average rainfall mainly located in the inland. While from 10 LT to 13 LT the large average rainfall located in both the Java Sea and the inland. And from 19 LT to 22 LT the large average rainfall located in Java coastwise. This situation has agreement with the formation of its maximum and standard deviation in diurnal cycles. The daily convective rainfall in the inland region is much more than that in the sea region, but heavy rainfall is often found over the sea

Haze is one of the impacts caused by forest and land fires. In order to determine how far the movement of haze from forest and land fires including in peatland, this research aims to determine the haze trajectory patterns from peatland fires in Riau Province in 2015 using HYSPLIT model. Furthermore, the haze trajectory patterns were grouped using the K-Means algorithm. The results show that the trajectory consists of 4887 positions of haze that moves to the northeast and northwest. The clustering results using K-Means show that the largest cluster has 3702 positions of haze and these haze movements are located at the average of height of 23.554 m AGL. Those haze positions were located in Riau, North Sumatra, Malaysia, and Malacca Strait.