Observation of El Niño and La Niña Phenomena, on the island of Sulawesi - Indonesia, based on the Global Positioning System (GPS)

This paper studies precipitable water vapor (PWV) in 2015-2016, an El Niño-Southern Oscillation episode (ENSO), and causes drought in Indonesia. Using the Global Positioning System (GPS), we obtained the PWV value. Expected can detect ENSO phenomenon through PWV value. We processed the GPS observation data by Precise Point Positioning (PPP) method using the goGPS software. The obtained values of Zenith Troposphere Delay (ZTD) and PWV were validated by comparing with the ZTD values from four IGS stations (BAKO, PIMO, NTUS, ALIC), i.e., there was a mean difference of -3.48, the average standard deviation is 13.36 mm, and the correlation coefficient was 0.94. The variation between the IGS ZTD and PPP ZTD estimates is within the measurement error. Our results can be used to study PWV behaviors for meteorological and climatological purposes in Indonesia. The values of PWV obtained from station GPS CMAK and CBIT were compared with PWV by radiosonde observations. The results showed a good agreement with the coefficient correlation is 0.86 at CMAK Station and 0.85 at CBIT station. The PWV values at CBIT stations varied between 37.08 and 76.01 mm with an average of 57.05 mm. For CTOL, CMAK, and CKEN stations, their average PWV is 61.17, 50.84, and 51.75 mm. The standard deviation (STD) value of the PWV at CMAK stations was 11.79 mm, higher than the other stations. During the El Niño event, the correlation between SSTa and PWV became weak at the four stations.