The main objective of the research is to evaluate the response of the WRF model to the domains and resolutions that are used in complex orographic conditions like the central Andes of Peru for the forecast of short- and medium-term rainfall. To do this, the model was configured with four domains and the verifications were made using data from meteorological stations located within the study area and TRMM data. Experiments were conducted for nine 10-day periods of rainy days, five cases of extreme rainfall, and one event with hail fall on the region. In general, the model overestimates precipitation, but, in the five cases of extreme rainfall, and in the case of the hailstorm, underestimation was observed, so it is not accurate to assert in an absolute way that WRF overestimates precipitation in the study region. It was observed that the 3-km domain simulate effectively the accumulated ra...

Se construye un modelo estadístico de pronóstico mensual de precipitaciones para Perú, basado en la relación de varios índices climáticos oceánicos y atmosféricos, así como de los índices de la oscilación de Madden-Julian, con la variabilidad estacional de la precipitación en el país, a inicializar en el mes de junio de cada año. Se aplicó la técnica de regresión lineal entre los índices y la precipitación grillada de la fuente de datos de PISCO para el período diciembre marzo, meses que corresponden a la estación lluviosa en Perú. El modelo se construyó con datos correspondientes al período 1981-2016 y se verificó con los registros de precipitación correspondientes a los años 2017-2022 para 15 zonas dentro de la costa, sierra y selva. El valor del error medio absoluto (MAE, por sus siglas en inglés) fue mejor para la selva, con excepción de los pronósticos ...

Se muestran dos modelos estadísticos de pronóstico, uno para el Índice Costero El Niño (ICEN) y el otro para el Índice Niño Oceánico (ONI, por sus siglas en inglés), los que se enfocan para la temporada de lluvias en Perú, usando datos del período 1975-2016. Como resultado, se obtuvieron dos modelos con versiones a inicializar en los meses de julio, agosto, septiembre y octubre. Los predictores más informativos para los primeros 2-3 meses de pronóstico fueron el comportamiento de los propios índices en meses anteriores, la profundidad de la isoterma de 20 ºC y los vientos zonales en superficie. Los índices climáticos juegan un papel más importante en plazos más largos. Para el ICEN, los vientos zonales resultaron más informativos en el Pacífico este; mientras que, para el ONI, los vientos zonales en el Pacífico oeste. Los coeficientes de correlación (R) de las ecuac...

En el presente trabajo, se llevó a cabo una investigación para evaluar cómo el modelo WRF pronostica la lluvia en los Andes centrales peruanos. Para ello, las salidas numéricas se comparan con datos de observación “in situ” de 19 estaciones en la región (Figura 1c), así como con datos satelitales. La mayor parte de la lluvia en el Perú se concentra en el período comprendido entre los meses de septiembre y abril (Silva et al., 2008), definiendo una marcada estacionalidad, que cuenta con una estación seca entre mayo y agosto (Aceituno, 1989; Vuille, 2008). En los Andes centrales peruanos, la lluvia juega un papel económico importante, ya que el 71% de la tierra cultivable en la cuenca del Mantaro, una de las más importantes de la zona, depende de ella para los cultivos.

A sensitivity study of the performance of the Weather Research and Forecasting regional model (WRF, version 3.7) to the use of different microphysics, cumulus, and boundary layer parameterizations for short- and medium-term precipitation forecast is conducted in the Central Andes of Peru. Lin-Purdué, Thompson, and Morrison microphysics schemes were tested, as well as the Grell–Freitas, Grell 3d, and Betts–Miller–Janjic cumulus parameterizations. The tested boundary layer schemes were the Yonsei University and Mellor–Yamada–Janjic. A control configuration was defined, using the Thompson, Grell–Freitas, and Yonsei University schemes, and a set of numerical experiments is made, using different combinations of parameterizations. Data from 19 local meteorological stations and regional and global gridded were used for verification. It was concluded that all the configurations over...

The ability of the WRF-ARW (Weather Research and Forecasting-Advanced Research WRF) model to forecast extreme rainfall in the Central Andes of Peru is evaluated in this study, using observations from stations located in the Mantaro basin and GOES (Geostationary Operational Environmental Satellite) images. The evaluation analyzes the synoptic conditions averaged over 40 extreme event cases, and considers model simulations organized in 4 nested domains. We first establish that atypical events in the region are those with more than 27 mm of rainfall per day when averaging over all the stations. More than 50% of the selected cases occurred during January, February, and April, with the most extreme occurring during February. The average synoptic conditions show negative geopotential anomalies and positive humidity anomalies in 700 and 500 hPa. At 200 hPa, the subtropical upper ridge or “Bol...

Las lluvias extremas ocurridas en el verano austral del 2017 en el centro y norte del Perú, han evidenciado que aún falta entender los procesos dinámicos que ocurren en esta zona, ya que no pudo ser pronosticado con antelación. Por otro lado, las ciudades costeras de Piura, Chiclayo, Trujillo y Lima, que tienen gran densidad poblacional y con alto desarrollo económico, están diseñadas para un clima de costa sin muchas lluvias. En la presente investigación, se evalúa la capacidad de respuesta del Modelo de Investigación y Pronóstico del Tiempo-WRF, por sus siglas en inglés (Skamarock, et al., 2008), para reproducir las lluvias extremas ocurridas en el verano de 2017, en las regiones costeras del centro y norte del Perú, vertiente del Pacífico, 3°S-10°S y 76°W-82°W (VNP). En los avances de esta investigación, se identificaron los periodos de lluvia mayores al percentil 9...

This study assesses the influence of PM₁₀ on the optical thickness of aerosols in the central Andes of Peru, in addition to analyzing and establishing their circulation patterns from July to October 2017. This particular period is considered herein because the largest biomass burning events are usually recorded during these months. The regional meteorological-chemistry transport model WRF-Chem (version 3.7) was used with the Fire Inventory from NCAR (FINN) fire emissions dataset and aerosol optical depth (AOD) data from the Aerosol Robotic Network monitoring network (AERONET), which has a CIMEL sun photometer located at the Huancayo Observatory, the most important city in the central highlands of Peru. The simulation used a single domain with a grid size of 18 km and 32 vertical levels. Results showed an increase in PM₁₀ concentrations with an increase in the number of fire outbr...

In the present study, five-year of precipitation features (PFs) datasets, based on Global Precipitation Measurement (GPM), are used to investigate the global and regional characteristics of extreme rainfall events (EREs). The EREs are defined based on the PFs area, depth (maximum height of radar reflectivity), and the rain rate and called them largest, deepest, and intense EREs, respectively. The EREs are divided into top 10%, 1%, 0.1%, and 0.01% based on their frequency of occurrences. It is observed that occurrences of EREs belonging to less than top 0.01% EREs follow the tropical rainfall climatology over the tropics based on all the parameters. Subtropical oceanic areas consist of a higher frequency of largest EREs, whereas tropical land areas consist of the higher number of deepest EREs. The most intense EREs (top 0.01%) are uniformly distributed over tropical areas and subtropical ...

Direct sun measurements with a CIMEL sunphotometer belonging to the AERONET network have been performed in the Huancayo Observatory, Peru, from March 2015 to August 2017, two and a half years, providing for the first time information about aerosols in the specific area. The prevalence of background conditions in the measurement site has been determined for the period of study. These conditions, which constitute more than 80% of cases, are occasionally altered, mainly by high aerosols loading, as a consequence of biomass-burning events. Biomass-burning periods cover every year from mid-July to mid-October. The identification of these periods has been possible through the classification of aerosols in 6 subtypes. The month with the maximum AOD monthly average is September, and in 2016, the absolute maximum value of 0.91 was registered. The mean AOD value for the study period is 0.10 ± 0.0...

Los aerosoles en la atmósfera juegan un papel importante en la transferencia de radiación solar, ya que, dependiendo del tipo, pueden reflejar o dispersar dicha radiación. Cabe resaltar también que algunos aerosoles son nocivos para la salud humana. En el Observatorio de Huancayo se vienen realizando mediciones de aerosoles con un fotómetro solar perteneciente a la red AERONET (AErosol RObotic NETwork) de la NASA. En este estudio se analizaron los datos desde marzo de 2015 hasta agosto de 2017, con el objetivo de evaluar los tipos de aerosoles y las regiones fuentes de los mismos. Se determinó la prevalencia de condiciones de fondo durante el período analizado. Estas condiciones, que constituyen más del 80 % de los casos, se alteran ocasionalmente debido a altas concentraciones de aerosoles generadas por la quema de biomasa que tienen lugar, no sólo en el Perú, sino también, e...

We acknowledge financial support from the International Foundation for Science, Sweden, Concejo Nacional de Ciencia y Tecnologia CONCYTEC, Peru, and the Wellcome Trust, U.K

The aim of the present study is to analyze the triggering mechanisms of three thunderstorms (TSs) associated with severe rainfall, hail and lightening in the tropical central Andes of Peru, specifically above the Huancayo observatory (12.04º S, 75.32º W, 3313 m a.s.l.) located in the Mantaro valley during the spring-summer season (2015–2016). For this purpose, we used a set of in-situ pluviometric observations, satellite remote sensing data, the Compact Meteorological Ka-Band Cloud Radar (MIRA-35C), the Boundary Layer Tropospheric Radar and downscaling model simulations with the Weather Research and Forecasting (WRF) Model (resolutions: 18 km, 6 km and 2 km), and the Advance Regional Prediction System (ARPS) (resolution: 0.5 km) models in order to analyze the dynamic of the atmosphere in the synoptic, meso and local scales processes that control the occurrence of the three TS events....

The present study presents a detailed analysis of the diurnal and monthly cycles the surface boundary layer and of surface energy balance in a sparse natural vegetation canopy on Huancayo observatory (12.04◦ S, 75.32◦ W, 3313 m ASL), which is located in the central Andes of Perú (Mantaro Valley) during an entire year (May 2018–April 2019). We used a set of meteorological sensors (temperature, relative humidity, wind) installed in a gradient tower 30 m high, a set of radiative sensors to measure all irradiance components, and a set of tensiometers and heat flux plate to measure soil moisture, soil temperatures and soil heat flux. To estimate turbulent energy fluxes (sensible and latent), two flux–gradient methods: the aerodynamic method and the Bowen-ratio energy-balance method were used. The ground heat flux at surface was estimated using a molecular heat transfer equation. The ...

El presente estudio explora el impacto del método de expresar los procesos microfísicos en las nubes en la simulación numérica de eventos de lluvia convectiva sobre los Andes centrales, utilizando el modelo numérico de Investigación y Pronóstico del Tiempo (WRF, por sus siglas en inglés). Se probaron seis métodos de parametrización de los procesos microfísicos, a partir de la anidación sucesiva unidireccional de cuatro dominios (18, 6, 3 y 0.75 km de resolución). Las parametrizaciones de otros procesos físicos se mantuvieron invariables en los diferentes experimentos. Se integró durante 36 h con los datos globales del Centro Nacional de Predicción Ambiental de Estados Unidos (NCEP, por sus siglas en inglés) con condiciones iniciales de las 07:00, hora local (GMT-5). Las simulaciones se verificaron utilizando datos de satélite GOES, información del radar perfilador de n...

The present study explores the cloud microphysics (MPs) impact on the simulation of two convective rainfall events (CREs) over the complex topography of Andes mountains, using the Weather Research and Forecasting- Advanced Research (WRF-ARW) model. The events occurred on December 29 2015 (CRE1) and January 7 2016 (CRE2). Six microphysical parameterizations (MPPs) (Thompson, WSM6, Morrison, Goddard, Milbrandt and Lin) were tested, which had been previously applied in complex orography areas. The one-way nesting technique was applied to four domains, with horizontal resolutions of 18, 6, and 3 km for the outer ones, in which cumulus and MP parameterizations were applied, while for the innermost domain, with a resolution of 0.75 km, only MP parameterization was used. It was integrated for 36 h with National Centers for Environmental Prediction (NCEP Final Operational Global Analysis (NFL) i...

Information on the vertical structure of rain, especially near the surface is important for accurate quantitative precipitation estimation from weather and space-borne radars. In the present study, the rainfall characteristics, from a vertically pointed profile Radar in the Mantaro basin (Huancayo, Peru) are observed. In summary, diurnal variation of near-surface rainfall and bright band height, average vertical profiles of the drop size distribution (DSD), rain rate, radar reflectivity (Zₑ) and liquid water content (LWC) are investigated to derive the rainfall characteristics. Diurnal variation of rain rate and bright band height show the bimodal distribution, where frequent and higher rain rate occurred during the afternoon and nighttime, and more than 70% bright band height found between 4.3–4.7 km. The average vertical profiles of Zₑ show the opposite characteristics above and ...