SPATIAL INTERPOLATION OF RAINFALL DATA USING COKRIGING AND RECURRENT NEURAL NETWORKS FOR HYDROLOGICAL APPLICATIONS IN SURABAYA, INDONESIA - Ariyanto, Danang; Sofro, A’yunin; Puspitasari, Riskyana Dewi I; Romadhonia, Riska Wahyu; Ombao, Hernando (BAREKENG: Jurnal Ilmu Matematika dan Terapan, 2026)