ESTIMASI NILAI PRECIPITABLE WATER VAPOR MENGGUNAKAN DATA VLBI

• Main Author: Chika Alifariani, Vegita
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/55801
• Institution: Institut Teknologi Bandung

Water vapor has high spatial and temporal variability. This makes the value of water vapor difficult to model and needs to be estimated directly through measurements. The presence of water vapor in the atmosphere has a very important role in global climate dynamics. However, it hinders geodetic measurement techniques, one of which is the Very Long Baseline Interferometry (VLBI) technique. The disturbance caused by the presence of water vapor is in the form of additional time required for wave propagation from extragalactic radio sources to reach the observer antenna which is commonly referred to as tropospheric wet delay or zenith wet delay (ZWD). Even so, the ZWD value can be reduced to a large amount of water vapor in the atmosphere in the form of precipitable water vapor (PWV). The VLBI data processing to get the ZWD value uses a software package called VieVS. ZWD estimation is carried out using a priori value to get slightly better results (Gipson and Macmillan, 2009). ZWD and PWV estimations were carried out in the first 10 months of 2020 in three locations, namely Fortaleza (Brazil) at the equator, Wettzell (Germany) at mid-latitudes, and Ny- Ålesund (Norway) at polar latitudes. This undergraduate thesis will show graphs of ZWD and PWV values to time in monthly average and hourly on one day time format. The results obtained will be compared with the ERA5 parameter data (ECMWF (European Center for Medium-Range Weather Forecast) Re-Analysis 5) by calculating the RMSE between the two. Fortaleza has the highest average PWV with a range of 1- 5 cm with the highest PWV occurring in April which is in the rainy season of Fortaleza, followed by Wettzell with a range of 0-2 cm, and ending with Ny-Ålesund with a range of -0.02 – 1.6 cm. The highest PWV for both locations located on four seasons latitude occurred in August for Wettzell and July for Ny-Ålesund which is where the two months are on the summer time span.