Altitudinal precipitation gradients in the tropics from tropical rainfall measuring mission (TRMM) precipitation radar


A Tropical Rainfall Measuring Mission (TRMM) climatology shows variability in surface precipitation rate-elevation relationships across the tropics. Vertical profiles of radar reflectivity and profiles of specific humidity and cross-barrier moisture fluxes during precipitation events from the Interim European Centre for Medium-Range Weather Forecasts Re-Analysis reveal four precipitation regimes with distinct precipitation mechanisms: 1) a tropical regime with a broad precipitation maximum at ∼ 1500m where convection is triggered by orographic lifting; 2) a trade winds regime with a near-sea level precipitation maximum dominated by forced ascent due to prevailing winds and the presence of dry air aloft; 3) a wet monsoon regime with a low-elevation precipitation maximum driven by efficient precipitation generation, large low-level crossbarrier moisture fluxes, and multiple convective modes; and 4) a dry monsoon regime with a high-elevation precipitation maximum reflecting intense convection and stratiform rain with a strong evaporation signature. In general, surface precipitation-elevation relationships across the tropics feature lower-elevation precipitation maxima relative to typical midlatitude regimes.

Journal of Hydrometeorology