On the dynamic mechanisms of intense rainfall events in the central Andes of Peru, Mantaro valley

Rojas, José Luis Flores; Moya-Álvarez, Aldo S.; Valdivia, Jairo M.; Piñas-Laura, Manuel; Kumar, Shailendra; Karam, Hugo Abi; Villalobos‐Puma, Elver; Martinez‐Castro, Daniel; Silva, Yamina

doi:10.1016/j.atmosres.2020.105188

Cited by 17 publications

(17 citation statements)

References 58 publications

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“…In the central Andes of Peru, it has been found that the most intense precipitation events occur during the afternoons and early nights when the convergence of thermally driven moisture fluxes that come from the Pacific Ocean and the Amazon Basin [6,7]. Even more, it has been seen that the strong moisture convergence generated by the interaction between thermally driven westerly winds, coupled with mid and upper-level westerly circulations and thermally driven easterly winds, cause some severe thunderstorms inside the Mantaro valley during the afternoons [8,9].…”

Section: Introductionmentioning

confidence: 99%

Analysis of Extreme Meteorological Events in the Central Andes of Peru Using a Set of Specialized Instruments

et al. 2021

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A set of instruments to measure several physical, microphysical, and radiative properties of the atmosphere and clouds are essential to identify, understand and, subsequently, forecast and prevent the effects of extreme meteorological events, such as severe rainfall, hailstorms, frost events and high pollution events, that can occur with some regularity in the central Andes of Peru. However, like many other Latin American countries, Peru lacks an adequate network of meteorological stations to identify and analyze extreme meteorological events. To partially remedy this deficiency, the Geophysical Institute of Peru has installed a set of specialized sensors (LAMAR) on the Huancayo observatory (12.04° S, 75.32° W, 3350 m ASL), located in the Mantaro river basin, which is a part of the central Andes of Peru, especially in agricultural areas. LAMAR consists of a set of sensors that are used to measure the main atmosphere and soil variables located in a 30-meter-high tower. It also has a set of high-quality radiation sensors (BSRN station) that helps measure the components of short-wave (SW) (global, diffuse, direct and reflected) and long-wave (LW) (emitted and incident) irradiance mounted in a 6-meter-high tower. Moreover, to analyze the microphysics properties of clouds and rainfall, LAMAR includes a set of profiler radars: A Ka-band cloud profiler (MIRA-35c), a UHF wind profiler (CLAIRE), and a VHF wind profiler (BLTR), along with two disdrometers (PARSIVEL2) and two rain gauges pluviometers. The present study performs a detailed dynamic and energetic analysis of two extreme rainfall events, two intense frost events, and three high-pollution events occurring on the Huancayo observatory between 2018 and 2019. The results show that the rainfall events are similar to the 1965–2019 climatological 90th percentile of the daily accumulated rainfall. The results also highlighted the patterns of reflectivity in function of height for both events, which is measured by highlighting the presence of convective and stratiform rainfall types for both events. The first intense rainfall event was associated with strong easterly circulations at high levels of the atmosphere, and the second one was associated with the presence of strong westerly circulations and the absence of BH-NL system around the central Andes. The first frost event was mainly associated with continuous clear sky conditions in the few previous days, corresponding to a radiative frost event. The second one was mainly associated with the intrusion of cold surges from extra-tropical South America. For both events, the energy budget components were strong-lower in comparison to the mean monthly values during early morning hours. Finally, for the high pollution events, the study identified that the main source of aerosols were the forest fires that took place in Peru with certain contributions from the fires in the northern area of Bolivia.

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Section: Introductionmentioning

confidence: 99%

Analysis of Extreme Meteorological Events in the Central Andes of Peru Using a Set of Specialized Instruments

et al. 2021

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“…The impacts of these flows vary annually. In addition, both flows regionally transport water vapour from both sides of the Andes, and the convergence of both flows explains the generation of intense precipitation in WSA and contributes significantly to the total accumulated precipitation (Junquas et al, 2018;Flores Rojas et al, 2019). The highest fraction of precipitation above 80% is found for the summers of 2008, 2009.…”

Section: Discussionmentioning

confidence: 95%

“…Third, at 650-200 hPa the EMFs transport water vapour from the Amazon (east side of the Andes) over the WSA region. In particular, the magnitude of these flows intensifies (Figure 9f) in the interior of the Andes due to diurnal effects in association with the synoptic circulation that predominate in this tropical region (Junquas et al, 2018;Flores Rojas et al, 2019). At these levels, the atmosphere is warmer because it is strongly influenced by the position of the BH.…”

Section: Discussionmentioning

confidence: 99%

“…Northern flows at low levels of the troposphere (Figure 10a) play an important role in the transport of water vapour along the Peruvian coast. The NWMF between 10°S and 15°S penetrates deeper towards the western slopes of the Andes and in association with the upslope winds, managed to surpass the Andes mountain range, producing intense events in the Central Andes of Peru (Flores‐Rojas et al ., 2021). In this study we reveal that the NWMF has an impact on precipitation between 15°S and 20°S on the western slopes of the Andes, it would be interesting to extend the analysis from 15°S to low latitudes to understand the flow impact on precipitation in the western slope of the Andes.…”

Section: Discussionmentioning

confidence: 99%

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Summertime precipitation extremes and the influence of atmospheric flows on the western slopes of the southern Andes of Perú

Villalobos‐Puma

Rojas

Martinez‐Castro

et al. 2022

Intl Journal of Climatology

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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 largescale 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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“…At higher spatial resolutions, RCMs in the tropical Andean region significatively improve precipitation features such as the spatial pattern, mesoscale processes linked to the diurnal cycle of convection (Gómez‐Ríos et al., 2023; Junquas et al., 2022, 2018; Rosales et al., 2022; Sierra et al., 2022), and the internal structure of mesoscale convective systems and hailstorms (Flores‐Rojas et al., 2021; Moya‐Alvarez et al., 2019). However, as these spatial resolutions range within the so‐called “gray zone” of convection, some local convection processes can be explicitly resolved, while others still require the use of a convection parameterization (Kendon et al., 2021).…”

Section: Discussionmentioning

confidence: 99%

Performance of Regional Climate Model Precipitation Simulations Over the Terrain‐Complex Andes‐Amazon Transition Region

Gutierrez,

Junquas,

Armijos

et al. 2024

JGR Atmospheres

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Regional climate models (RCMs) are widely used to assess future impacts associated with climate change at regional and local scales. RCMs must represent relevant climate variables in the present‐day climate to be considered fit‐for‐purpose for impact assessment. This condition is particularly difficult to meet over complex regions such as the Andes‐Amazon transition region, where the Andean topography and abundance of tropical rainfall regimes remain a challenge for numerical climate models. In this study, we evaluate the ability of 30 regional climate simulations (6 RCMs driven by 10 global climate models) to reproduce historical (1981–2005) rainfall climatology and temporal variability over the Andes‐Amazon transition region. We assess spatio‐temporal features such as spatial distribution of rainfall, focusing on the orographic effects over the Andes‐Amazon “rainfall hotspots” region, and seasonal and interannual precipitation variability. The Eta RCM exhibits the highest spatial correlation (up to 0.6) and accurately reproduces mean annual precipitation and orographic precipitation patterns across the region, while some other RCMs have good performances at specific locations. Most RCMs simulate a wet bias over the highlands, particularly at the eastern Andean summits, as evidenced by the 100%–2,500% overestimations of precipitation in these regions. Annual cycles are well represented by most RCMs, but peak seasons are exaggerated, especially at equatorial locations. No RCM is particularly skillful in reproducing the interannual variability patterns. Results highlight skills and weaknesses of the different regional climate simulations, and can assist in the selection of regional climate simulations for impact studies in the Andes‐Amazon transition zone.

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On the dynamic mechanisms of intense rainfall events in the central Andes of Peru, Mantaro valley

Cited by 17 publications

References 58 publications

Analysis of Extreme Meteorological Events in the Central Andes of Peru Using a Set of Specialized Instruments

Analysis of Extreme Meteorological Events in the Central Andes of Peru Using a Set of Specialized Instruments

Summertime precipitation extremes and the influence of atmospheric flows on the western slopes of the southern Andes of Perú

Performance of Regional Climate Model Precipitation Simulations Over the Terrain‐Complex Andes‐Amazon Transition Region

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