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Anthropogenic activities on land will affect the carbon system in coastal waters. This condition will affect the role of coastal waters as a source or sink of carbon. This research will examine the distribution of carbonate systems and estimate CO2fluxes. Water samples were taken at 30 stations as well as measuring in situ water parameters including pH, temperature, salinity, and pressure. Alkalinity was analysed based on the titration method, chl-a using the fluorometer method, and carbonate system parameters (pCO2(sea) and DIC) calculated using CO2SYS.xlsm. The pCO2(atm) value is calculated based on atmospheric data from satellite data, including the saturation vapour pressure of sea air in the atmosphere, fraction mol of CO2, and sea level pressure. Pearson correlation analysis was used to see the correlation between the measured parameters and CO2flux. Carbon flux is determined based on the difference between atmospheric and oceanic pCO2. The DIC calculation result was in the range of 1,946.09 µmol/kg - 2,061.65 µmol/kg and the total alkalinity was 2,156.86 µmol/kg - 2,264.71 µmol/kg. Based on this value, Jepara coastal waters have pCO2(sea) of 573,800 micro-atmospheric (µatm) which is higher than pCO2(atm) (i.e., 386,772 µatm). The input of organic/inorganic carbon resulting from anthropogenic processes on land has influenced Jepara coastal waters which act as a source of CO2into the atmosphere amounting to 103,799 mmol/m2/day. The results of this research can be used as a reference for managing coastal areas to achieve low carbon emissions.

We investigate the distribution of various fractions phosphorus (P) in sediments at the coastal area of Semarang City. Samples were collected from thirteen locations at the Banjir Kanal Barat, port and Banjir Kanal Timur. Sedimentary parameters such as sand, silt, clay, and organic carbon were analysed in order to find out their relation with various P fractions. The sediment types are predominantly sandy and silty with low clay content. Among all fractions (loosely bound/Ads-P), bound calcium/Ca-P), iron bound/Fe-P), and organic fraction/OP), Ca-P fractions constitute the largest portion (71.2 %) followed by iron-bound (17.0 %), organic fraction (10.4 %) and loosely bound (1.4 %). The bioavailable P fractions range from 20.2 % to 42.0 % of the total P (TP) content with average 28.8 %. Relatively high Ads-P content is observed in offshore locations with comparatively high mud percentage as compared with the near-shore locations. The order of abundance of the main forms of P in the Semarang coastal surface sediments is as follows: Ca-P > Fe-P > OP > Ads-P. The concentration of this fraction causes the abundance of chlorophyll-afrom 9.09 to 21.09 mg/m3.

Tidal data monitoring is an important component for onshore and offshore activities. This study designs a low-cost tide gauge and an architecture that combines the Internet of Things with numerical processing to record tidal and ocean wave data from a single sensor without compromising data quality. The location of tide gauge test is located in Timbulsloko Village, Sayung District, Demak Regency, Central Java, Indonesia. The tide gauge test was carried out for 13 days from January 1, 2022, to January 14, 2022. This tide gauge study used a Heltec LoRa 32,433 MHz microcontroller. The A01NYUB type UART ultrasonic sensor is used to measure sea level and wave height. Tidal data is filtered using the Kalman method until the tidal and residual signals are obtained. Timbulsloko is a micro-tidal region, the tidal range is less than 2 m. The mean high water spring (MHWS) is 1.15 m while the mean low water spring (MLWS) is 0.15 m. The type of tide that occurs in the Timbulsloko area, Demak is a mixed tide prevailing diurnal. The mean wave height of the recorded residuals is 22.82 cm. This tide gauge system produces good quality data when compared to other studies that use standardized observation and instrumentation.

We investigated the atmospheric processes over high sea surface temperature called Hot Event (HE) in the western equatorial Pacific from climatological analysis and a case study of the HE which began on 28 May 2003 (hereafter, HE030528). Climatological analysis shows that during the development stage of HE, solar radiation inside the HE area is higher than its climatology and wind speed is lower than the decay stage. During the decay stage, strong westerly wind often occurs inside HE area. The case study of HE030528 shows that the suppressed convection above high SST area resulted from the deep convection from the northern and southern areas outside HE. The suppressed convection created a band‐shaped structure of low cloud cover along HE area increasing solar radiation during the development stage. Thus, the theory of “remote convection” was supported for the HE030528 formation mechanisms. The large sea level pressure gradient magnitude between the southern side of the terrain gap and the northern coast of the Solomon Islands, through which strong wind blew, indicated the role of land topography for the increase of wind speed during the decay of HE030528. Moreover, surface wind had an important role to influence the variability of solar radiation during the occurrence of HE030528 by controlling the water vapor supply in the upper troposphere through surface evaporation and surface convergence variation. Thus, surface wind was the key factor for HE030528 occurrence. The representativeness of HE030528 and the possible relation between HE and Madden‐Julian Oscillation are also discussed. The suppressed phase of MJO may also contribute for the development of HEThe suppressed convection generated from the deep convection outside of HE area increase solar radiation during the development stageDuring the development and decay stage of HE, the variability of convection at the upper layer is influenced by surface wind