During the Monsoon Asian Hydro−Atmosphere Scientific Research and Prediction Initiative (MAHASRI; 2006–16), we carried out two projects over the Indonesian maritime continent (IMC), constructing the Hydrometeorological Array for Intraseasonal Variation−Monsoon Automonitoring (HARIMAU; 2005–10) radar network and setting up a prototype institute for climate studies, the Maritime Continent Center of Excellence (MCCOE; 2009–14). Here, we review the climatological features of the world’s largest “regional” rainfall over the IMC studied in these projects. The fundamental mode of atmospheric variability over the IMC is the diurnal cycle generated along coastlines by land−sea temperature contrast: afternoon land becomes hotter than sea by clear-sky insolation before noon, with the opposite contrast before sunrise caused by evening rainfall-induced “sprinkler”-like land cooling (different from the extratropical infrared cooling on clear nights). Thus, unlike the extratropics, the diurnal cycle over the IMC is more important in the rainy season. The intraseasonal, seasonal to annual, and interannual climate variabilities appear as amplitude modulations of the diurnal cycle. For example, in Jawa and Bali the rainy season is the southern hemispheric summer, because land heating in the clear morning and water vapor transport by afternoon sea breeze is strongest in the season of maximum insolation. During El Nino, cooler sea water surrounding the IMC makes morning maritime convection and rainfall weaker than normal. Because the diurnal cycle is almost the only mechanism generating convective clouds systematically near the equator with little cyclone activity, the local annual rainfall amount in the tropics is a steeply decreasing function of coastal distance (e-folding scale 100–300 km), and regional annual rainfall is an increasing function of “coastline density” (coastal length/land area) measured at a horizontal resolution of 100 km. The coastline density effect explains why rainfall and latent heating over the IMC are twice the global mean for an area that makes up only 4% of the Earth’s surface. The diurnal cycles appearing almost synchronously over the whole IMC generate teleconnections between the IMC convection and the global climate. Thus, high-resolution (<< 100 km; << 1 day) observations and models over the IMC are essential to improve both local disaster prevention and global climate prediction.

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Maritime continent coastlines controlling Earth’s climate

Influence of spatial and temporal scales on statistical analyses of rainfall variability in the river Nile basin

This study evaluates the sensitivity of precipitation in Southeast Asia (SEA) to the choice of land-surface schemes available in RegCM4, that is BATS1e (BATS) and CLM4.5 (CLM), over the CORDEX SEA domain. Two similar simulations using different land-surface schemes were conducted for the period 1989 to 2007, with a horizontal resolution of 25× 25 km. Four different types of observational data were used to evaluate the performance of these simulations. It was found that both of these simulations reproduced the SEA precipitation climatology spatial patterns reasonably well. However, the BATS simulation systematically produced higher frequency and more intense precipitation over land. The CLM simulation, although overestimating the precipitation frequency, produced a lower amount of on-land precipitation. The precipitation annual cycle and interannual variability were both insensitive to the choice of land-surface scheme. The errors in the precipitation simulation were found to originate from the simulated convective precipitation (CPr). Large-scale precipitation was found to be less sensitive to the choice of land-surface scheme. The influence of the land-surface scheme on SEA precipitation simulation took place through the interaction between soil moisture content and CPr. The soil moisture content was consistently higher in the BATS simulation, as was the CPr simulated. During December to February (DJF), the difference in the precipitation amount simulated by BATS and CLM simulations was lower over the SEA mainland, even though the soil moisture content in both simulations was very different. This difference was due to the inactivity of the convective activities over the SEA mainland during DJF. This study concludes that the simulation of SEA precipitation amount was sensitive to the choice of land-surface scheme, and recommend the use of CLM4.5 land-surface scheme for simulation of SEA precipitation.

Performances of BATS and CLM land-surface schemes in RegCM4 in simulating precipitation over CORDEX Southeast Asia domain

Current movement in Benoa Bay water, Bali, Indonesia: Pattern of tidal current changes simulated for the condition before, during, and after reclamation

Understanding the changes in gross primary production (GPP), which is the total carbon fixation by terrestrial ecosystems through vegetation photosynthesis, due to land use conversion in a tourism city is important for carbon cycle studies. Satellite data from Landsat 5, Landsat 7 and Landsat 8 and meteorological data are used to calculate annual GPP for 1995, 2003 and 2014, respectively, using the vegetation production model (VPM) in the tourism city Denpasar, Bali, Indonesia. Five land use types generated from topographic maps in three different years over the past two decades are used to quantify the impacts of land use changes on GPP estimation values. Analysis was performed for two periods to determine changes in land use and GPP value as well as their speed. The results demonstrated that urban land development, namely, the increase of settlement areas due to tourism activity, had overall negative effects on terrestrial GPP. The total GPP of the whole area decreased by 7793.96 tC year−1 (12.65%) during the study period. The decline is due to the conversion of agriculture and grassland area into settlements, which caused the city to lose half of its ability to uptake carbon through vegetation. However, although forest area is declining, forest maintenance and restoration by making them protection areas has been helpful in preventing a drastic decline in GPP value over the past two decades. This study provides information that is useful for carbon resource management, tourism, policy making and scholars concerned about carbon reduction in a tourism city.

Changes in Gross Primary Production (GPP) over the Past Two Decades Due to Land Use Conversion in a Tourism City

Maritime Continent rainfall variability during the TRMM era: The role of monsoon, topography and El Niño Modoki

Benoa Bay is a micro tidal semi-enclosed water with a size of 10 km x 15 km of the inner bay with a narrow gap formed by Serangan Island and Benoa Peninsula. Benoa Bay is a strategic area in south of Bali Province linked to the Indian Ocean through a narrow entrance. Recently, a large amount of siltation occurred in this area, which is caused by sedimentation from five rivers discharged into the bay. The sedimentation in the lagoon is of ecological and physical concern due to the mangrove ecosystem disturbing and operation of Benoa port for the necessity of increased dredging. This paper deals with tide-induced flows in a semi-enclosed water body in a micro-tidal environment that is subjected to tide and river discharge conditions. In this study, The Coastal Modeling System (CMS) developed by Coastal Inlets Research Program was used for simulating flow, waves, sediment transport, and morphology changes in coastal areas. This CMS has effectively calibrate the data set supplemented by field observations.

Hydrodynamics and Sediment Transport of Benoa Bay, Semi-Enclosed Bay in Bali, Indonesia

The Bali Strait is one of Indonesia's territorial waters that have high natural resource potential. The area is only about 2,500 km 2 but has a high potential fishing ground. The Bali Strait has unique and dynamic waters that can cause fluctuations in fish production amount each year. The largest type of fish caught in the Bali Strait is lemuru (Sardinella lemuru), a fish found only in the Bali Strait. This fish plays a significant role in the economy of fishers in the Bali Strait. Each year the catch of lemuru has fluctuated, making fishing locations challenging to predict. Sea Surface Temperature (SST) and Chlorophyll-a (Chl-a) are oceanographic parameters that can affect the resources of the ocean. Oceanographic phenomena, such as upwelling, can also influence the condition of fish resources. Therefore, understanding the relationships between these factors is essential in practical fisheries management. Observation of oceanographic factors is very hard with the field observation due to time and cost limitations. The remote sensing technique is an efficient method to determine SST distributions and Chl-a concentrations using satellite imagery. This study analyzes SST and Chl-a concentration in the Bali Strait using the Global Change Observation Mission(GCOM-C) satellite and determines the correlation between Chl-a and SST with a total fish catch(lemuru) during 2019. The results showed the maximum average Chl-a concentration observed on August 1.62 mg/m 3 and the lowest concentration observed on January 0.45 mg/m 3 , the maximum SST on March was 28.12° C, and on August (Dry season) with 22.40° C. The SST variable's influence provides a negative correlation (R = -0.209) with changes in lemuru catch, while the Chl-a parameter has a positive correlation (R = 0.375) with changes in the catch. The pattern of relationship between Chl-a with fish catching had a good relationship than the SST in 2019.

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RELATIONSHIP BETWEEN CHLOROPHYLL-A AND SEA SURFACE TEMPERATUR WITH Sardinella lemuru CATCHING IN BALI STRAIT

Beach nourishment, or also commonly known as beach fill, is a technique widely used in coastal engineering to rehabilitate eroded beaches or create new beaches and widen existing beaches. However, once an instance of beach filling has occurred, it needs to be repeated on a regular basis because the new beach would be more prone to abrasion than natural beaches. This paper describes the of beach change based on numerical modeling in the study of the evolution of a beach nourishment project. The measured beach profile, wave height and sediment in Sanur beach, Bali are used for the numerical analysis based on the existing studies are applied in the analysis of the beach. The simulation results show that there are three segment of the coastal area in between the groin need to be overcome.

Study of the Evolution of Sanur Beach Nourishment Project for Beach Enhancement

The provision of rural drinking water in Bali Province is mostly managed independently by the community. The rural drinking water supply system is sufficient to contribute to community drinking water services. Preservation of raw water sources and the environment through the application of local wisdom Tri Hita Karana greatly determines the sustainability of raw water source management in rural drinking water supply systems in Bali Province. The method of analyzing the sustainability status of raw water management from the social, economic, ecological, technological, and institutional dimensions uses the Multi-Dimensional Scaling (MDS) method. The sustainability index on the analysis results on the ecological dimension is 63.52%, the economic dimension is 51.82%, the social dimension is 55.59%, the technological dimension is 49.30% and the institutional dimension is 51.20%. The status of sustainability with sufficient categories is found in the ecological, economic, social, and institutional dimensions. The lever factor on the sustainability dimension of raw water management in the rural drinking water supply system in Bali Province is 21 attributes of the lever factor. The leverage factor attribute in each sustainability dimension is very sensitive to the sustainability index value. In the dimension of technology sustainability, there are 5 attributes of lever factors that need to be repaired, refined, and improved, including facilities and infrastructure for rural drinking water supply systems for the sustainability of the technological dimension. 

I. Gusti Bagus Sila Dharma

Papers

Maritime Continent rainfall variability during the TRMM era: The role of monsoon, topography and El Niño Modoki

Hydrodynamics and Sediment Transport of Benoa Bay, Semi-Enclosed Bay in Bali, Indonesia

RELATIONSHIP BETWEEN CHLOROPHYLL-A AND SEA SURFACE TEMPERATUR WITH Sardinella lemuru CATCHING IN BALI STRAIT

Study of the Evolution of Sanur Beach Nourishment Project for Beach Enhancement

Status of Raw Water Management Sustainability Based on Local Wisdom on Rural Water Supply in Bali, Indonesia