The Use of MODIS and Sentinel-1 Data Fusion to Estimate Precipitable Water Vapor Values

Precipitable Water Vapor (PWV) describes the amount of water vapor in the atmosphere that potentially becomes rain. Along with the development of the space geodetic technique, water vapor can be observed using the remote sensing technology. This research uses an integration of active and optical remote sensing data which are Sentinel-1 and MODIS. Since interferogram generated by Sentinel-1 SAR images contains tropospheric delay, it can be substracted as Short Wavelength Delay (SWD) which a part of PWV value. Furthermore, the absolute PWV value is obtained by extracting parameters from MODIS atmosphere level-2. MODIS provides PWV values for reconstructing the Elevation Dependent Delay (EDD) and Long Wavelength Delay (LWD) components. We used 118 epochs to represent the rainy and dry seasons between March 2017-February 2021. The result shows that a maximum absolute PWV value of 68 mm occurred on 22/2/2020 which belongs to the time of rainy season. The estimation recorded a minimum PWV value of 20 mm on 7/6/2017 and 14/6/2018. June is when Indonesia usually experiences a dry season. Generally, the maximum and minimum daily average absolute PWV values are 68.6845 mm and 1.5884 mm, respectively.