Validasi hubungan data hujan satelit TRMM dengan data observasi DAS Cokroyasan dalam analisis hujan rancangan

Limited rainfall data from the Cokroyasan watershed station hinders hydrological analysis. This study evaluates the accuracy and correlation of Cokroyasan watershed rainfall data against TRMM satellite rainfall data to assess TRMM's viability as an alternative to ground observations. The analysis employs rainfall data from three stations Gebang, Watujagir, and Kutoarjo spanning 2009 2018. Initial steps involve consistency testing via the RAPS method and stationarity checks. Thiessen Polygon method then computes areal average rainfall. Station data is compared with calibrated, verified, and validated TRMM data using Correlation Coefficient (R), Root Mean Square Error (RMSE), Nash-Sutchliffe Efficiency (NSE), and Relative Error (KR). Results from 9 years of validation and 1 year of verification show strong agreement: RMSE of 13,478 and NSE of 0,836 indicate TRMM effectively represents station data. The datasets exhibit very strong correlation (R = 0,929) and low bias (KR = 0,250), supporting linear regression modeling. Return period analysis reveals TRMM underestimates rainfall compared to stations, particularly for longer periods. Despite this limitation in extreme events, TRMM satellite data serves as a reliable alternative to sparse station data for hydrological applications in the Cokroyasan watershed.