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Summertime precipitation extremes and the influence of atmospheric flows on the western slopes of the southern Andes of Perú
(John Wiley and Sons Ltd, 2022)
Martínez Castro, Daniel
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Silva Vidal, Yamina F.
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Villalobos Puma, Elver
Although climatologically dry, the western slopes of the southern Andes of Peru (WSA) can experience precipitation extremes (PEs) during the summer (December–February) resulting in great economic and human losses. Generally, WSA has a positive upslope gradient in precipitation, meaning more rain falls at higher elevations, but observations have shown this gradient can become negative with higher rainfall near the coastal cities. In this study we analyse 2000–2019 regional atmospheric patterns associated with different upslope precipitation gradients and PEs in WSA using principal component analysis methods and surface station observations. Results show important changes in the atmospheric circulation patterns during the occurrence of PE events. A prevailing pattern of negative southerly wind anomalies and regional warming of the southeastern Pacific Ocean leads to significant increases in moisture along the coast of WSA. Eastern moisture flows associated with the presence of the Bolivian High are observed at upper levels of the atmosphere and transport water vapour from the Amazon to the western side of the Andes. Additionally, there is a blocking effect aloft in response to an intense gradient of geopotential height that attenuates the easterly circulations. These large-scale mechanisms act to concentrate high precipitable water amounts and high levels of convective available potential energy in the troposphere which favours the vertical velocities essential to trigger PEs. These results increase our knowledge of the large-scale characteristics of PEs to help with forecasting these impactful events and protecting the more than 1.8 million people living in WSA.
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Hailstorm events in the Central Andes of Peru: Insights from historical data and radar microphysics
(Copernicus Publications, 2024)
Callañaupa Gutierrez, Stephany
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Villalobos Puma, Elver
Hailstorms, while fascinating from a meteorological perspective, pose significant risks to communities, agriculture, and infrastructure. In regions such as the Central Andes of Peru, the characteristics and frequency of these extreme weather events remain largely uncharted. This study fills this gap by investigating the historical frequency and vertical structure of hailstorms in this region. We analyzed historical hailstorm records dating back to 1958 alongside 4 years of observations (2017–2021) from the Parsivel2 disdrometer and a cloud-profiling radar MIRA35c. Our findings indicate a trend of decreasing hail frequency (−0.5 events per decade). However, the p value of 0.07 suggests the need for further investigation, particularly in relation to environmental changes and reporting methods. The results show that hailstorms predominantly occur during the austral summer months, with peak frequency in December, and are most common during the afternoon and early evening hours. The analysis of radar variables such as reflectivity, radial velocity, spectral width, and linear depolarization ratio (LDR) reveals distinct vertical profiles for hail events. Two case studies highlight the diversity in the radar measurements of hailstorms, underscoring the complexity of accurate hail detection. This study suggests the need for refining the Parsivel2 algorithm and further understanding its classification of hydrometeors. Additionally, the limitations of conventional radar variables for hail detection are discussed, recommending the use of LDR and Doppler spectrum analysis for future research. Our findings lay the groundwork for the development of more efficient hail detection algorithms and improved understanding of hailstorms in the Central Andes of Peru.
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Dynamic atmospheric mechanisms associated with the diurnal cycle of hydrometeors and precipitation in the Andes–Amazon transition zone of central Peru during the summer season
(Springer, 2024)
Martínez Castro, Daniel
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Santiago Martel, Alexzander
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Villalobos Puma, Elver
The diurnal cycle of total hydrometeor availability and its associated patterns of atmospheric circulation is studied over a connected Andes–Amazon (A–A) system in the central region of Peru during the summer season. Surface precipitation depends on the amount of hydrometeors that occur in the atmosphere and its atmospheric dynamics. Hydrometeors and the precipitation efficiency index were estimated using radar of the core satellite of the GPM system (N-GPM) for the period 2014–2022. The atmospheric dynamics were analyzed using the regional Weather Research and Forecasting (WRF) model. According to the results, the Andes mountain range produces precipitation at a surface level more efficiently during the afternoon and early evening hours (12–19 LT) due to the convergence of the thermal mesoscale circulations transporting moisture fluxes from the east and west. Both generate convective multicells along the Andes mountain range. The circulation from the west intensifies during the day, causing the displacement of the chain of convective multicells towards the east and producing hydrometeors and intense precipitations in the inter-Andean valleys. The A–A transition zone is more efficient in producing precipitation during the early hours of the day (00–07 LT) due to an increase in the northern circulation associated with the low-level jets and a change in the magnitude of the horizontal winds. Northerly winds enter the A–A transition zone with increased intensity and leave with reduced intensity. This mechanism is driven by the effect of the topographical barrier and the masses of cold air located in high areas on the eastern flank of the Andes. These factors generate significant updrafts and, therefore, the formation of storm clouds with high concentrations of hydrometeors and precipitation on the surface.
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Future changes of precipitation types in the Peruvian Andes
(Nature Research, 2024)
Alvarado Lugo, Robert A.
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Callañaupa Gutierrez, Stephany
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Llactayo Peña, Valeria
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Villalobos Puma, Elver
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Yarlequé, Christian
In high-altitude regions, such as the Peruvian Andes, understanding the transformation of precipitation types under climate change is critical to the sustainability of water resources and the survival of glaciers. In this study, we investigate the distribution and types of precipitation on a tropical glacier in the Peruvian Central Andes. We utilized data from an optical-laser disdrometer and compact weather station installed at 4709 m ASL, combined with future climate scenarios from the CMIP6 project, to model potential future changes in precipitation types. Our findings highlight that increasing temperatures could lead to significant reductions in solid-phase precipitation, including snow, graupel and hail, with implications for the mass balance of Andean glaciers. For instance, a 2 °C rise might result in less than 10% of precipitation as solid, in regard to the present day, transforming the hydrological processes of the region. The two future climate scenarios from the CMIP6 project, SSP2-4.5 and SSP5-8.5, offer a broad perspective on potential climate outcomes that could impact precipitation patterns in the Andes. Our study underscores the need to revisit and expand our understanding of high-altitude precipitation in the face of climate change, paving the way for improved water resource management strategies and sustainable glacier preservation efforts in these fragile ecosystems.
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Surface energy exchanges and stability conditions associated with convective intense rainfall events on the central Andes of Peru
(Elsevier B.V., 2025)
Silva Vidal, Yamina F.
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Villalobos Puma, Elver
El estudio analiza los patrones de precipitación, el balance de energía superficial y los gradientes atmosféricos verticales en el Observatorio Geofísico de Huancayo, ubicado en el valle del Mantaro, en los Andes centrales del Perú, utilizando datos entre 2018 y 2022, además de registros climáticos históricos desde 1965. Los resultados muestran que las lluvias ocurren principalmente durante la tarde y primeras horas de la noche, con una marcada diferencia entre las estaciones seca y lluviosa. Asimismo, se investigaron 21 eventos de precipitación intensa asociados a actividad convectiva mediante pluviómetros, radar MIRA-35c y datos satelitales GPM-IMERG. El trabajo también evaluó los flujos turbulentos de energía y el desempeño del modelo atmosférico ARPS, encontrando diferencias entre las estimaciones del modelo y las observaciones reales. Antes de los eventos convectivos intensos se identificaron aumentos en el flujo de calor sensible y en el flujo horizontal de momento, así como cambios en la humedad y en la dinámica de la capa límite atmosférica, lo que sugiere que estas variables pueden servir como indicadores tempranos de lluvias intensas. En conjunto, el estudio resalta la importancia de comprender la dinámica atmosférica para mejorar la predicción meteorológica y la preparación frente a eventos climáticos extremos.

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