Interaction of Air and Sea above Seamount in the Halmahera Sea

Abstract

The interaction of sea and air plays a very important role in the early stages of cloud formation. In certain cases, changes in temperature in the sea surface layer and the atmospheric layer closest to the sea will affect the initiation of the formation of water vapor which can become cloud. To monitor the sea-air temperature interaction above Seamount in Halmahera Sea, we took an expedition of Jala Citra-I 2021 Aurora from August 28 to September 9, 2021 using The Indonesian Navy Center for Hydrography and Oceanography research vessel, the Navy’s KRI Spica-934. Weather condition was observed using two installed Automatic Weather Stations (AWS) mounted on a vessel, radiosonde in Sorong, West Papua, and Outgoing Longwave Radiation (OLR) data from NOAA (National Oceanic and Atmospheric Administration), while the profile of sea surface temperature (SST) were observed using a 24-hour CTD measurement. Both AWS data were analyzed using two samples Kolmogorov-Smirnov test with h=1 and showed low correlations (r2 = 0.2-0.4, p-value <0.01) for the parameters of temperature, relative humidity, and wind speed. The hourly SST ranged 29°C – 30°C from 0-50 meter and the Lifting Condensation Level ranged about 939 to 985 mb in the morning on 1 - 2 September. The OLR was a neutral and positive values. These conditions indicated that a strong local effect dominantly created by a strong sea-air interaction in the study area. A warm SST with a strong divergence wind leads a warm air layer developed on the sea surface to rise. A low OLR with a moderate CAPE is enough to support the updraft of water vapor, rising from sea surface and then support convective activity formed in the region. In addition, it shows that the changes activity of convective clouds, developing over warm waters, are dominant mode of diurnal variability. However, investigation of intra-seasonal variability in Halmahera Sea was not clear. Further investigation on spatiotemporal of sea-air interaction on a local scale are needed to capture the phenomena on its season.