<![CDATA[Inter-annual precipitation variability across tropical regions is driven by complex interactions between large-scale atmospheric circulation and local processes, yet the relative contributions of key moisture budget components remain insufficiently quantified. This study examines seasonal contrasts between DJF and JJA in the Tropical Region using a moisture budget framework, with northern Sumatra, Indonesia, as a representative tropical case study. By using 36 years (1981–2016) of ERA-Interim data, wet and dry years are identified based on standardized precipitation anomalies, with statistical significance assessed using a Student’s t-test. Composite analyses show that anomalous vertical moisture transport associated with vertical velocity anomalies (-〈ω^' ∂_p q ̅ 〉) is the dominant contributor in both seasons. However, its magnitude is weaker during DJF, indicating less coherent upward motion and weaker coupling between the large-scale circulation and convection than during JJA. In JJA, enhanced large-scale circulation strengthens moisture convergence and divergence, producing more organized convection. In contrast, DJF exhibits weaker circulation and a larger residual, suggesting stronger influences of transient and nonlinear processes. These findings highlight seasonal asymmetry in precipitation controls and provide insights applicable to tropical climate variability.]]>
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