Proyeksi Awal Musim ..... (Haries Sa tyawa rdhana dan Armi Susa ndi) 1 PROYEKSI AWAL MUSIM DI JAWA BERBASIS HASIL DOWNSCALING CONFORMAL CUBIC ATMOSPHERIC MODEL (CCAM) (SEASON ONSET PROJECTION IN JAVA BASED ON CCAM DOWNSCALING OUTPUT) Haries Satyawardhana *)1 dan Armi Susandi **) *) Pusat Sains dan Teknologi Atmosfer Lembaga Penerbangan dan Antariksa Nasional Jl. Dr. Djundjunan 133 Bandung 40173 Indonesia **) Program Studi Sains Kebumian Institut Teknologi Bandung Jl. Ganesha No. 10 Bandung 40116 Indonesia 1 e-mail: hariessatha@gmail.com Diterima 14 Juli 2015, Direvisi 21 September 2015, Disetujui 24 Desember 2015 ABSTRACT Research on the season onset using BMKG (Meteorology, Climatology and Geophysics Agency) criteria, which using 10-day rainfall data so-called dasarian, in Indonesia has been widely done, but it still has limitations such as the analysis period, the spatial resolution and still not be able to generate for future projections. The use of climate models is the answer to overcome all these limitations. This study uses Conformal Cubic Atmospheric Model (CCAM) for downscaling from global climate model and NCEP/NCAR reanalysis (National Center for Environmental Prediction/National Center for Atmospheric Research) data. This research using two period, they are: 1991 - 2010 (20 years), which is the current state and 2011 – 2030 which is a future projection. The results of this study indicate that the projection period which is generated using IPCC A2 scenario concludes that in most parts of Java, the Dry Season Onset (AMK) is come earlier, while Wet Season Onset (AMH) tends to come lately comparing than AMH in the baseline period. In other words, Java is projected to have a longer dry season, and the rainy season is shorter than the current conditions. Keywords: CCAM, Downscaling, Dry season onset and rainy season onset