Characteristics of Precipitation and Mesoscale Convective Systems over
the Peruvian Central Andes in Multi 5-Year Convection-Permitting
Simulations
Abstract
Using the Weather Research and Forecasting (WRF) model with two
planetary boundary layer schemes, ACM2 and MYNN, convection-permitting
model (CPM) regional climate simulations were conducted for a 6-year
period at a 15-km grid spacing covering entire South America and a
nested convection-permitting 3-km grid spacing covering the Peruvian
central Andes region. These two CPM simulations along with a 4-km
simulation covering South America produced by National Center for
Atmospheric Research, three gridded global precipitation datasets, and
rain gauge data in Peru and Brazil, are used to document the
characteristics of precipitation and MCSs in the Peruvian central Andes
region. Results show that all km-scale simulations generally capture the
spatiotemporal patterns of precipitation and MCSs at both seasonal and
diurnal scales, although biases exist in aspects such as precipitation
intensity and MCS frequency, size, propagation speed, and associated
precipitation intensity. The 3-km simulation using MYNN scheme generally
outperforms the other simulations in capturing seasonal and diurnal
precipitation over the mountain, while both it and the 4-km simulation
demonstrate superior performance in the western Amazon Basin, based on
the comparison to the gridded precipitation products and gauge data.
Dynamic factors, primarily low-level jet and terrain-induced uplift, are
the key drivers for precipitation and MCS genesis along the east slope
of the Andes, while thermodynamic factors control the precipitation and
MCS activity in the western Amazon Basin and over elevated mountainous
regions. The study suggests aspects of the model needing improvement and
the choice of better model configurations for future regional climate
projections.