Akademik Veri Yönetim Sistemi
JOURNAL OF APPLIED GEODESY, cilt.1, sa.1, ss.1-15, 2026 (ESCI, Scopus)
Abstract: The Global Navigation Satellite System (GNSS)-
Radio Occultation (RO) is a satellite-based technique providing
significant advantages for improving weather forecasts
and investigating climatic variations. In this study,
precipitable water vapor (PWV) derived from FORMOSAT-
7/COSMIC-2 GNSS-RO wet profiles was compared with that
calculated from radiosonde (RS) observations and the fifthgeneration
global reanalysis dataset (ERA5). For this purpose,
RS stations situated in Samsun, Istanbul, Izmir, and
Adana over Türkiye were selected as reference locations.
Two horizontal collocation distances, 300 km and 150 km,
were applied to examine the sensitivity of the results to
spatial matching. The performance of COSMIC-2 RO PWV
was evaluated using root mean square error (RMSE), linear
regression, Pearson correlation, and the R-squared coefficient
(R2). For both collocation distances, RMSE values are
about 3 mm for RO-RS and about 2 mm for RO-ERA5, and
correlation coefficients are generally above 0.8. Regression
slopes are lower for RO-RS, ranging between 0.6 and 0.8, and
closer to unity for RO-ERA5, ranging between 0.8 and 1.0.
Reducing the collocation distance leads to a small increase
in correlation. However, it does not result in a consistent
improvement in RMSE, indicating the influence of vertical
sampling characteristics. Overall, GNSS-RO shows reasonable
consistency with RS observations. When used in combination
with reanalysis products, it can provide reliable
atmospheric moisture estimates over Türkiye.
Keywords: GNSS-RO; radiosonde; ECMWF ERA5; precipitable
water vapor