Browsing by Author "Kumar, Shailendra"
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Item Open Access Analysis of extreme meteorological events in the central Andes of Peru using a set of specialized instruments(MDPI, 2021-03-21) Flores Rojas, José Luis; Silva Vidal, Yamina; Suárez Salas, Luis; Estevan, René; Valdivia Prado, Jairo Michael; Saavedra Huanca, Miguel; Giráldez, Lucy; Piñas-Laura, Manuel; Scipión, Danny; Milla, Marco; Kumar, Shailendra; Martínez Castro, DanielA 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 (12.04º S, 75.32º 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...Item Open Access Analysis of possible triggering mechanisms of severe thunderstorms in the Tropical Central Andes of Peru, Mantaro Valley(MDPI, 2019-06-01) Flores Rojas, José Luis; Moya Álvarez, Aldo Saturnino; Kumar, Shailendra; Martínez Castro, Daniel; Villalobos Puma, Elver Edmundo; Silva Vidal, YaminaThe 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 results show that at synoptic scale, the TSs are characterized by the southern displacement of the South-east Pacific Subtropical Anticyclone up to latitudes higher than 35º S, by the weakening and south-eastern displacement of the Bolivian high–North east low system and by the intrusion of westerly winds along the west side of the central Andes at upper and medium levels of the atmosphere. At meso-scale, apparently, two important moisture fluxes from opposite directions are filtered through the passes along the Andes: one from the north-west and the other from the south-east directions converge and trigger the deep convection into the Mantaro valley. These moisture fluxes are generated by the intrusion of the sea-breeze from the Pacific ocean along the west of the Andes coupling with upper and middle westerly winds and by the thermally induced moisture fluxes coming from the South American low level jet at the east side of the Andes. At the local scale, there is a low-level conditional instability in the previous hours as well as during the occurrence of the TSs above the Huancayo observatory. In addition, the simulation results indicated the possibility of generation of inertial gravity waves in the Amazon basin, associated with geostrophic adjustment which transports energy and moisture into the central Andes plateau and consequently intensifies the thunderstorms above the Mantaro valley.Item Restricted Distribution of hydrometeors in monsoonal clouds over the South American continent during the austral summer monsoon: GPM observations(Taylor & Francis, 2020-01-15) Kumar, Shailendra; Silva Vidal, YaminaThe Global precipitation measurement (GPM) was launched in February 2014 and provides the three-dimensional attenuated corrected radar reflectivity factor (Zₑ) along with the raindrop size distribution (DSD) parameters. The DSD parameters consist of the mass-weighted hydrometeors size (Dm in mm) and normalized hydrometeors concentration (Nw in mm⁻¹ m⁻³). The present study investigates the vertical and spatial distribution of hydrometeors in intense convective clouds that form over South America (SA) during Austral summer monsoon seasons. We defined Cumulonimbus towers (CbTs) and intense convective cells based on 8 km (ICC8s) and 3 km (ICC3s), using vertical profile of radar reflectivity algorithm and then their properties are explored over eight selected areas over SA. CbT is defined by using the Zₑ≥20 dBZ at 12 km with base height less than 3 km altitude. The ICCs are defined by using the Zₑ thresholds at 8 and 3 km altitude, and Zₑ threshold value belongs to the top 5% of the Zₑ value at the reference height. Subtropical areas including Sierra de Cordoba (SDC) and La Plata basin (LPB) consist of a higher frequency of CbTs and ICC8s, whereas ICC3 is nearly uniformly distributed over the SA continent and the Atlantic Ocean (AO). Eastern foothills of the Andes mountain also consist of a higher frequency of CbTs and ICC8s. Irrespective of the height and Zₑ thresholds used in the present study, the SDC and LPB consist of the most intense convective clouds with higher echo top altitude, and similar to that observed over Western Himalaya foothills over South Asia. Land and ocean differences are visible in the cloud cells based on the 3 km reference height, which is well below the freezing level. CbTs and ICC8s do not show the land and ocean differences as in both the cases the AO has comparable Zₑ in average vertical profiles compared to the land areas, but in ICC3, the AO has the weakest cloud cells with the least cloud top height. The absolute slope of Zₑ in mixed-phase altitude is highest in ICC3 and reflect the local precipitation fallout in mixed-phase regions and suggested that fewer hydrometeors of larger sized are lifted in the upper atmosphere. The least slope over SDC and Central Foothills indicates that higher sized of hydrometeors are lifted in the upper atmosphere in the monsoonal clouds compared to other parts of SA continent. The DSD parameters indicate that in general, intense cloud cells consist of large-sized hydrometeors although their concentration is low. The spatial averages of the DSD parameters also indicate larger sized of hydrometeors exist on average for all types of clouds at 3 and 8 km in southeastern areas of SA including SDC, LPB, and Brazilian highlands. The single meteorological feature is not responsible for the intense and deep convection, but the combined meteorological variables are responsible for producing the intense and deeper convection.Item Restricted Effect of the surface wind flow and topography on precipitating cloud systems over the Andes and associated Amazon basin: GPM observations(Elsevier, 2019-09-01) Kumar, Shailendra; Silva Vidal, Yamina; Moya Álvarez, Aldo Saturnino; Martínez Castro, DanielThe characteristics of the precipitation under the influence of topography and surface wind flow are investigated over South America. Here the precipitating cloud systems (PCSs) are identified using the Global Precipitation MeasurementPrecipitation Radar (GPM-PR) data, which provides the three dimensional radar reflectivity factor (Zₑ), rain rate, drop size and droplet concentration. For each PCSs the surface wind properties are estimated using European Center for Medium-Range Weather Forecast Interim data. Based on the direction of surface flow the PCSs are classified into five categories. Over the South America the near surface wind flow transports the moisture from Amazon basin to east flank of Andes and validated here. The directional surface flow decides the occurrences of the PCSs, as upslope consists of the higher and larger PCSs at the peak of Andes compared to downslope flow. The directional flow suggests that northern Andes consists of pronounced bright band characteristics compared to southern Andes, and upslope and easterly flow have higher probability of rain at the eastern slope of Andes compared to westerly and downslope flow in northern Andes. The results show that orography also modulates the precipitation characteristics under different directional flow over and near the Andes. Eastern slope of Andes has higher rain rate compared to western slope of Andes in most of the directional flow. Orographically forced moisture loaded flow, over the eastern slope of Andes causing the higher rain rate, drop radius and droplet concentration in northern Andes. At the low lands, effective drop radius and droplet concentration show the opposite characteristics, and effective drop radius (concentration) is least (highest) except for the downslope flow over the northern Andes. The results of DSD parameters along with rainfall intensity show the microphysical evolution of the precipitation under the complex orography over the Andes mountain. The present study suggests that in future, surface flow must be considered for studying the orographic precipitation in numerical modeling.Item Open Access Estudio de las tormentas convectivas a través de observación instrumental y modelado numérico en los Andes Centrales del Perú(Universidad Nacional Mayor de San Marcos, 2019) Villalobos Puma, Elver Edmundo; Martínez Castro, Daniel; Kumar, Shailendra; Silva Vidal, YaminaLa agricultura local en los Andes Centrales del Perú es sensible a episodios extremos, por ejemplo, la precipitación intensa asociada a tormentas convectivas perjudican los sembríos por el exceso de agua, mientras que los granizos rompen las hojas de los cultivos cuando alcanzan el suelo. Aquí se estudió la distribución espacial y la estructura vertical de las tormentas convectivas mediante el método del análisis complejo. El área de estudio se fraccionó en 4 sub-áreas (3 áreas sobre los Andes y una que comprende la transición Andes-Amazonía), en los cuales se realizó la estadística de la reflectividad, la intensidad de lluvia y los parámetros microfísicos, determinados usando los sensores del PR-TRMM, el núcleo GPM, y el modelo WRF. Como resultado se tiene que en las regiones de los Andes ocurren sistemas de nubes convectivas más profundas que en la región de transición Andes-Amazonía. De modo que la diferencia del promedio vertical de la reflectividad presenta alrededor de 5dBZ entre Andes y Amazonía-Andes. El ciclo diurno de la lluvia es diferente entre las regiones de Andes y Amazonía-Andes. En promedio llueve en los intervalos 13-23 horas local y 18-6 horas local respectivamente. Los porcentajes de ocurrencia de precipitación convectiva y estratiforme en áreas de los Andes están en proporción 30% y 70% respectivamente y sus contribuciones relativas a la lluvia acumulada son equivalentes, en cambio en la transición Amazonía-Andes los porcentajes de ocurrencia son 31% y 69% y sus contribuciones acumulativas a la lluvia son 53% y 47% respectivamente. Se concluye que la precipitación convectiva en las sub-áreas de los Andes dependen fundamentalmente del mecanismo de forzamiento orográfico que fortalece el crecimiento de los hidrometeoros por encima del nivel de congelación entre 6 y 12km de altura y propicia mayor acumulado de lluvia.Item Open Access Evaluación de los algoritmos del GPM para estimar los parámetros DSD usando múltiples observaciones in situ sobre el Observatorio de Huancayo, Junín-Perú(Universidad Nacional Mayor de San Marcos, 2019) Del Castillo Velarde, Carlos Manuel; Kumar, Shailendra; Fashe Raymundo, OctavioLa cuenca del Mantaro está ubicada en el centro de Perú y es un área compleja para estudiar diversos fenómenos atmosféricos, que son causados principalmente por su compleja orografía. Otros factores, como la condición sinóptica, el transporte de humedad, la dirección y fuerza del viento, dan como resultado una distribución compleja de las precipitaciones durante el monzón austral de verano. Monitorear las precipitaciones requiere una densa red de estaciones meteorológicas que permitan observar estos patrones espaciales. En el caso de la cuenca del Mantaro, las estaciones son limitadas, por lo que es necesario utilizar otras formas de recopilación de datos. Por tal motivo se recurre al radar de precipitación (PR) abordo del Global Precipitation Measurement (GPM) el cual nos permite observar la precipitación en una estructura 3D. En esta investigación se evalúan los algoritmos que emplea el satélite GPM para determinar los parámetros Dm y Nw que parametrizan la distribución del tamaño de gotas (DSD), por ello a partir de datos in situ del radar MIRA35c y disdrómetro óptico PARSIVEL2 y con ayuda del método de la matriz T se calculó las secciones eficaces de dispersión de una gota para simular las mediciones de reflectividad en las bandas Ku y Ka que luego se emplearon en los algoritmos single frequency (SF) y dual frequency (DF) y a su vez compararlos con los parámetros del DSD determinados experimentalmente. Se determinó que el algoritmo SF presento mejor correlación de los parámetros Dm y Nw alcanzando 0.95 y 0.94 superando los 0.94 y 0.84 del algoritmo DF respectivamente. a su vez el algoritmo SF presento un mejor rendimiento de los parámetros Dm y Nw para intensidades de lluvia menores a 2 mm/h y mayores a 8 mm/h por otro lado el algoritmo DF destaco en intensidades entre 2 y 8 mm/h.Item Restricted Evaluation of GPM Dual-Frequency Precipitation Radar algorithms to estimate drop size distribution parameters, using ground-based measurement over the Central Andes of Peru(Springer, 2021-09) Del Castillo-Velarde, Carlos; Kumar, Shailendra; Valdivia Prado, Jairo Michael; Moya Álvarez, Aldo Saturnino; Flores Rojas, José Luis; Villalobos Puma, Elver Edmundo; Martínez Castro, Daniel; Silva Vidal, YaminaThe raindrop size distribution (DSD) parameters, which consists of the mass-weighted average diameter (Dm) and the scaling parameter for the concentration (Nw) are essential to estimate precipitation in numerical modelling and other research areas such as the Global Precipitation Measurement (GPM) core satellite. In the present work, we used the GPM Dual-Frequency Precipitation Radar algorithms (GPM-DPR), single (SF) and dual (DF) frequency, and in situ observations to derive the DSD parameters and evaluate the performance of algorithms under the complex orography and climate regime of the central Andes. We used data from optical disdrometer and Ka-band profiler radar over Huancayo Observatory during the austral summer monsoon. Our results indicate that the GPM-DPR algorithms have problems to correctly estimate the DSD parameters of convective rains due to the high variability in time and space of this type of rain and is the result of fixing the shape parameter (µ). The estimation of DSD parameters in stratiform rains, which are very common in the central Andes, is strongly affected by the limitation of the DF algorithm in light rain rates caused by its inability to estimate Dm < 1 mm.Item Open Access Extreme Rainfall Forecast with the WRF-ARW Model in the Central Andes of Peru(MDPI, 2018-09-18) Moya Álvarez, Aldo Saturnino; Gálvez, José; Holguín, Andrea; Estevan, René; Kumar, Shailendra; Villalobos Puma, Elver Edmundo; Martínez Castro, Daniel; Silva Vidal, YaminaThe 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 “Bolivian high” was present, with its northern divergent flank over the Mantaro basin. Simulation results show that the Weather Research and Forecasting (WRF) model underestimates rainfall totals in approximately 50–60% of cases, mainly in the south of the basin and in the extreme west along the mountain range. The analysis of two case studies shows that the underestimation by the model is probably due to three reasons: inability to generate convection in the upstream Amazon during early morning hours, apparently related to processes of larger scales; limitations on describing mesoscale processes that lead to vertical movements capable of producing extreme rainfall; and limitations on the microphysics scheme to generate heavy rainfall.Item Restricted Frequency of a state of cloud systems over tropical warm ocean(IOP Publishing, 2019-07-01) Kumar, Shailendra; Bhat, G. S.The knowledge of how long a mesoscale convective system stays in a given stage of life cycle is an important information for many practical applications. A unique approach has been adopted here to find the stage of development of convective cloud systems (CCSs) over tropical oceanic areas. We use the Tropical Rainfall Measuring Mission (TRMM) data products, and define a cloud system (CS) based on criteria that depend on TRMM precipitation radar equivalent radar reflectivity factor (Zₑ) and TRMM Microwave Imager polarization corrected temperature data. Average vertical profile of Zₑ and convective area fraction (CAF) of a CS are used to identify its state which is a proxy for life stage. We use two parameters, namely reflectivity differences (RD) and convective area fraction (CAF) and defined 5 states of CS life cycle. Our results show that majority of CSs are found in mature stage and formative and dissipation stages are relatively short over the twelve warm tropical oceanic areas selected for analysis. Each ocean has a distinct signature in the RD-CAF phase space, and, there are regional/seasonal differences within an ocean basin. Bay of Bengal has less CAF compared to the equatorial Indian ocean. In the tropical Pacific Ocean, majority of the CSs lie in mature stage with CAF between 0.3 to 0.6, whereas, CSs in mature stage over the Atlantic Ocean have their CAF between 0.2 and 0.3. CS characteristics over the Atlantic Ocean during the Boreal summer and winter are different.Item Open Access Hydrometeors Distribution in Intense Precipitating Cloud Cells Over the Earth’s During Two Rainfall Seasons(Springer, 2024-01-25) Kumar, Shailendra; Flores Rojas, José Luis; Moya Álvarez, Aldo Saturnino; Martínez Castro, Daniel; Silva Vidal, YaminaIn the present study, we used attenuated corrected radar refectivity factor (Zₑ) and rain-drop size distribution (DSD) to investigate the hydrometeors distribution in the intense precipitating cloud cells (PCCs) from precipitation radar (PR) onboard on Global Precipitation Measurement (GPM). The DSD parameters consist of two variables, namely, mass-weighted mean diameter (Dₘ) in mm and normalized scaling parameters for hydrometeors concentration (Nw) in mm⁻¹ m⁻³. We defned two types of PCCs, which are the proxies for the intense rainfall events. First PCC is termed as Cumulonimbus Towers (CbTs), which consist of Zₑ> =20 dBZ at 12 km altitude, and its base height must be less than 3 km altitude. We also defned intense convective clouds (ICCs), which consist of Zₑ>30 (40) dBZ at 8 km (3 km), respectively, and are termed as ICC8 and ICC3, respectively. The spatial distribution reveals that continental areas consist of a higher frequency of CbTs and ICC8s compared to oceanic areas, whereas ICC3s are uniformly distributed over tropical land and oceanic areas. The DSD parameters reveal that intense PCCs have larger hydrometeors (Dₘ), whereas weaker (less Zₑ) vertical profles consist of higher concentration (Nw) of smaller hydrometeors (Dₘ). Land consists of larger hydrometeors (Dₘ) compared to oceanic areas, and diferences are higher in liquid phase regimes compared to mixed phase regimes. The vertical profles of Zₑ, Dₘ and Nw are showing the higher regional diferences among the diferent land-based areas, compared to various tropical ocean basins. Western Himalaya Foothills and Sierra De Cordoba consist of the strongest vertical profles with the largest Dₘ on the Earth’s áreas during JJAS and DJFM months, respectively.Item Open Access El impacto de la parametrización de procesos microfísicos en la simulación de dos eventos de lluvia convectiva sobre los Andes centrales del Perú usando el modelo numérico WRF-ARW(Instituto Geofísico del Perú, 2020-09) Martínez-Castro, Daniel; Kumar, Shailendra; Flores Rojas, José Luis; Moya Álvarez, Aldo Saturnino; Valdivia Prado, Jairo Michael; Villalobos Puma, Elver Edmundo; Del Castillo Velarde, Carlos; Silva Vidal, YaminaEl 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 nubes de banda Ka instalado en el Observatorio de Huancayo y variables meteorológicas medidas en superficie. Todas las parametrizaciones microfísicas describieron aproximadamente el comportamiento de la temperatura durante el paso del sistema, aunque en uno de los casos se subestimó la temperatura y en otros dos se subestimó la precipitación acumulada en 24 h. En particular, las configuraciones del modelo con parametrizaciones de Morrison y Lin reprodujeron la dinámica general del desarrollo de los sistemas de nubes para los dos estudios de caso. No obstante, el análisis del campo horizontal y los perfiles verticales de la masa de agua del sistema, así como los diferentes hidrometeoros muestran que la parametrización de Morrison reprodujo los sistemas convectivos de manera más consistente con las observaciones que los otros métodos.Item Open Access Incertidumbre causada por el parámetro de forma (µ) en los algoritmos del GPM-DPR para estimar los parámetros del DSD(Instituto Geofísico del Perú, 2020-05) Del Castillo Velarde, Carlos; Kumar, ShailendraEl valle del río Mantaro, ubicado en los Andes centrales del Perú, Junín, es caracterizado por flujos de humedad provenientes de la Amazonía que, combinada con su compleja topografía, genera una distribución espacial y temporal de las lluvias muy variable. El monitoreo de lluvias mediante el satélite Global Precipitation Measurement (GPM), equipado con un radar de precipitación de frecuencia dual (DPR, por sus siglas en inglés), ayuda a tener datos espaciales ante el limitado número de estaciones meteorológicas dentro del valle. El GPM, para estimar la precipitación, aplica ciertas asunciones, una de estas es restringir el parámetro de forma (μ) en la distribución del tamaño de gotas (DSD, por sus siglas en inglés) a 3, lo que podría introducir errores en la estimación de la lluvia. En este trabajo se busca evaluar el impacto de μ en el algoritmo de estimación de precipitación del satélite GPM para la región de los Andes, mediante mediciones in situ con un disdrómetro óptico. El periodo de análisis corresponde a los meses que van de diciembre de 2017 a marzo de 2018. Los resultados preliminares indican que en los algoritmos SF (Single Frequency) y DF (Dual Frequency) el mayor error debido a la restricción del parámetro de forma de DSD está relacionado a las gotas con diámetro entre 2 y 3 mm; además, se identificó que el algoritmo DF es más sensible a las variaciones del parámetro de forma, incrementando el error de las gotas con diámetro entre 1 y 2 mm.Item Restricted Influence of PBL parameterization schemes in WRF_ARW model on short - range precipitation's forecasts in the complex orography of Peruvian Central Andes(Elsevier, 2020-03-01) Moya Álvarez, Aldo Saturnino; Estevan, René; Kumar, Shailendra; Flores Rojas, José Luis; Ticse, Joel J.; Martínez Castro, Daniel; Silva Vidal, YaminaThe study evaluated the sensitivity of the precipitation forecast in the central Andes of Peru of Weather Research and Forecasting (WRF) model to change the planetary boundary layer (PBL) schemes. In that region is located the Mantaro basin, which is one of the most important in the region. Here, the rainfall is very important to the agriculture and to the reserves of drinking water. The simulations were carried out with ten PBL schemes for 19 days in January, February, and March, between 2009 and 2012. Based on the statistical analysis (model vs. observation), the more efficient schemes were determined and analyses of the vertical profiles of some variables are shown. As a result, the schemes that most helped the model in rainfall forecasting were MYNN3 (general and north sector of the basin), Bou-Lac (central sector) and Bretherton-Park (southern sector). The model generally overestimated rainfall in the northern basin, underestimated in the center, and in the south some schemes overestimated and others underestimated. In addition, it was concluded that the boundary layer is more stable in the model than in the observations. The schemes that generated the most rainfall were those that generated a more unstable boundary layer with weaker wind speeds, at least with easterly winds. Another conclusion is that the height of the boundary layer for rainy days in the region at 18 UTC oscillates around 1000 m and that, generally, the wind's velocity changes very little or decreases within the boundary layer and increases above it.Item Restricted On the dynamic mechanisms of intense rainfall events in the central Andes of Peru, Mantaro valley(Elsevier, 2021-01-15) Flores Rojas, José Luis; Moya Álvarez, Aldo Saturnino; Valdivia Prado, Jairo Michael; Piñas-Laura, Manuel; Kumar, Shailendra; Karam, Hugo Abi; Villalobos Puma, Elver Edmundo; Martínez Castro, Daniel; Silva Vidal, YaminaThe present study was aimed at analysing the main atmospheric dynamic mechanisms associated with the occurrence of intense rainfall events above the Huancayo observatory (12.05°S, 75.32°W, 3313 m asl) in the central Andes of Perú (Mantaro valley) from January 2018 to April 2019. To identify the rainfall events, we used a set of instruments from the laboratory of physics, microphysics and radiation (LAMAR) composed by in-situ pluviometric observations, satellite remote sensing data (GPM), Cloud Radar (MIRA-35c), Boundary Layer Tropospheric Radar (BLTR) and downscaling model simulations with WRF (resolutions: 18 km, 6 km and 2 km) and ARPS (0.5 km) models to analyse the dynamics of the atmosphere for the synoptic, meso and local processes that control the occurrence of these rainfall events. The results showed that all intense rainfall events are associated with the presence of thermal meso-scale circulations that transport moisture fluxes through passes with gentle slopes along both sides of the Andes. The easterly moisture fluxes come in from the South America Low Level Jet (SALLJ) and the westerly moisture fluxes from the Pacific Ocean. The arrival of these moisture flows to regions within the Mantaro valley depends on their coupling with the circulations at medium and high levels of the atmosphere. At the synoptic scale, the results show that the rainfall events can be separated into two groups: the first one associated with westerly circulations (WC) at the mid and upper levels of the atmosphere, generated by the weakening and eastern displacement of the anticyclonic Bolivian high-North east low (BH-NE) system, and the second associated with easterly circulations (EC) at the mid and upper levels of the atmosphere, generated by the intensification of the BH-NE system. The observed and simulated results showed that multicell convective systems of WC events are more extensive and deeper than EC events. This situation can be explained as the convergence of moisture fluxes from opposite directions occurred within the Mantaro basin for WC events. In contrast, for EC events, the convergence develops at the east Andes mountain range, following which the multicell storm system propagates westward, driven by easterly circulations. The EC events occur mostly in the summer months, while the WC events occur mostly in the autumn and spring months. Moreover, apparently the inertia gravity waves (IGWs) formed in the Amazon basin transport moisture and energy to the central Andes plateau and intensify the convection processes.Item Restricted Precipitation structure during various phases the life cycle of precipitating cloud systems using geostationary satellite and space-based precipitation radar over Peru(Bellweather Publishing, 2020-11-27) Kumar, Shailendra; Del Castillo-Velarde, Carlos; Flores Rojas, José Luis; Moya Álvarez, Aldo Saturnino; Martínez Castro, Daniel; Srivastava, Shweta; Silva Vidal, YaminaThe life cycle of clouds consists of mainly into three phases, namely developing, mature, and dissipating phases. The information about the vertical structure of the precipitation during different phases of development will improve their representation in the cloud models. Whether specific regimes over Peru favor the formation or decay of the cloud systems and how their intensity varies during different phases of development will provide the insight into the precipitation structure over Peru. We used two satellite-based data, namely from Global Precipitation Measurement dual Precipitation Radar (GPM-DPR) and GOES (Geostationary Operational Environmental Satellite) to expose the vertical structure of precipitation during different phases of the precipitating cloud systems (PCSs). A PCS is defined using the GPM based near surface rainfall data and then GOES-based brightness temperature (BT) is used to identify a specific phase of PCS. In particular 9 hours of BT (e.g., time series of BT) data for a GPM DPR overpass is used to a specific phase of PCS. Once, all the PCSs are identified into a specific phase, their statistical properties are studied. The highest convective fraction area (~26%) and near surface rain rate (RR; 4.97 mm hr⁻¹) are observed in developing phase of PCSs. Also, the convective fraction area and near surface RR decreases as cloud matures, and, least convective fraction area and RR (~4.11 mm hr⁻¹) are observed in dissipating phase PCSs. The vertical structure of precipitation consists of more complex relation among different phases of PCSs. The vertical distributors of hydrometeors (e.g., radar reflectivity, RR, and DSD parameters) during various phases have different characteristics above and below the freezing height (~5 km). For example, convective precipitation has small concentration of higher sized hydrometeors below the freezing height, whereas mature has PCSs show different behavior. The total amount of water analysis shows that liquid and ice water amount varies during different phases and affect the rainfall characteristics. It is observed that precipitation characteristics during different phases are influenced by the Andes Mountain and developing phase PCSs have higher sized of hydrometeors with higher near surface RR at the north-eastern continent of Peru.Item Open Access Rainfall characteristics in the Mantaro basin over tropical Andes from a vertically pointed profile rain radar and in-situ field campaign(MDPI, 2020-03-02) Kumar, Shailendra; Del Castillo Velarde, Carlos Manuel; Valdivia Prado, Jairo Michael; Flores Rojas, José Luis; Callañaupa Gutierrez, Stephany Magaly; Moya Álvarez, Aldo Saturnino; Martínez Castro, Daniel; Silva Vidal, YaminaInformation 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 below the melting level (ML) and depend on the near-surface rain rate. For example, the average Zₑ profiles have a negative gradient above the ML, whereas below, the ML, the gradient depends on the near-surface rain rate. The rain rate and LWC show the opposite behavior, and both consist of a positive (negative) gradient below (above) the ML. The vertical growth of DSD parameters depend on the near-surface rain rate, and a higher concentration of large-sized of droplets are observed for higher near surface rain rate, however, the dominant modes of droplets are <1 mm throughout the vertical column. However, the most significant variation in DSD growth is observed for near-surface rain rate ≥20 mm/h. These findings suggest using different retrieval techniques for near surface rain estimation than the rest of the vertical profile and high rain rate events. The improved understanding of the tropical Andes precipitation would be very important for assessing climate variability and to forecast the precipitation using the numerical models.Item Restricted Response of the WRF model to different resolutions in the rainfall forecast over the complex Peruvian orography(Springer Nature, 2019-08-01) Moya Álvarez, Aldo Saturnino; Martínez Castro, Daniel; Kumar, Shailendra; Estevan, René; Silva Vidal, YaminaThe 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 TRMMdata. 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 thatWRF overestimates precipitation in the study region. It was observed that the 3-km domain simulate effectively the accumulated rainfall, while the 0.75-km domain reproduces better the process at local scale. The results in the domain with the coarsest resolution of 18 km showed the lowest skill in simulating rainfall compared to the higher resolutions. Thus, it is concluded that an increase of resolution leads to an improvement of the results of rainfall forecast in the region and the structure of clouds systems. At the same time, the domains with resolutions of 18 km showed poorer results.Item Open Access Seasonal and diurnal cycles of surface boundary layer and energy balance in the Central Andes of Perú, Mantaro Valley(MDPI, 2019-12-05) Flores Rojas, José Luis; Cuxart, Joan; Piñas-Laura, Manuel; Callañaupa, Stephany; Suárez Salas, Luis; Kumar, Shailendra; Moya Álvarez, Aldo Saturnino; Silva Vidal, YaminaThe 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 results show minimum mean monthly temperatures and more stable conditions were observed in June and July before sunrise, while maximum mean monthly temperatures in October and November and more unstable conditions in February and March. From May to August inverted water vapor profiles near the surface were observed (more intense in July) at night hours, which indicate a transfer of water vapor as dewfall on the surface. The patterns of wind direction indicate well-defined mountain–valley circulation from south-east to south-west especially in fall–winter months (April–August). The maximum mean monthly sensible heat fluxes were found in June and September while minimum in February and March. Maximum mean monthly latent heat fluxes were found in February and March while minimum in June and July. The surface albedo and the Bowen ratio indicate semi-arid conditions in wet summer months and extreme arid conditions in dry winter months. The comparisons between sensible heat flux (QH) and latent heat flux (QE), estimated by the two methods show a good agreement (R² above 0.8). The comparison between available energy and the sum of QE and QH fluxes shows a good level of agreement (R² = 0.86) with important imbalance contributions after sunrise and around noon, probably by advection processes generated by heterogeneities on the surface around the Huancayo observatory and intensified by the mountain–valley circulation.Item Open Access Seasonal and regional differences in extreme rainfall events and their contribution to the world’s precipitation: GPM observations(Hindawi, 2019-05-30) Kumar, Shailendra; Silva Vidal, Yamina; Moya Álvarez, Aldo Saturnino; Martínez Castro, DanielIn 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 oceans, and spatial distribution shows that a deepest ERE belongs to intense EREs in the tropical land areas. Large differences between the precipitation contribution from the largest and deepest EREs are seen; for example, the top 1% of largest EREs contribute to ∼80.7% of Earth’s precipitation, whereas the corresponding percentage for deepest EREs is only 53%. On the regional and seasonal scale, South Asia (SAsia) and South America (SA) nearly show common features, as oceanic and land areas consist of largest and deepest EREs, respectively, and contribute to higher precipitation. Subtropical latitudes over South America, including Sierra de Cordoba and La Plata basin, consist of deepest and intense EREs and match with those of the Indo-Gangetic plain over South Asia, which also shows the similar characteristics. EREs based on various parameters are strongly linked over SAsia compared to SA. For example, the largest top 10% EREs have a higher probability to be part of the top 10% deepest and intense EREs over SAsia. The seasonal and regional water budget reveals different characteristics, as in the southern hemisphere, the deeper EREs contribute to the higher fraction of rainfall, but over SAsia, the shallower EREs could also contribute to significant rainfall.Item Restricted Statistical characterization of vertical meteorological profiles obtained with the WRF-ARW model on the central Andes of Peru and its relationship with the occurrence of precipitation on the region(Elsevier, 2020-07-15) Moya Álvarez, Aldo Saturnino; Martínez Castro, Daniel; Kumar, Shailendra; Flores Rojas, José Luis; Estevan, René; Saavedra Huanca, Miguel; Silva Vidal, YaminaThe work carried out a characterization of tropospheric vertical profiles in rainy and dry seasons by behavior of thermodynamic indices obtained with the WRF model for the period January 2018–March 2019 on the central Andes of Peru and its relationship with rainfall in the region. A case study was also analyzed using sounding observation data. The precipitation observed were taken from 8 meteorological stations located in the Mantaro basin belonging to the National Meteorological Service of Peru. As a results, it was found that the behavior of the thermodynamic parameters responds to the general characteristics of each period. The level of condensation was always higher in the dry period, in which the lower troposphere was also more stable. The KI, TT, Sweat and CAPE indices were always higher in the rainy season, as was water vapor mixing ratio. The vertical shear was mostly higher in the dry period. The parameters that were most informative to precipitation forecasting in rainy period were the precipitation predicted by the model WRF, the average relative humidity of the 600–400 hPa layer and the water vapor mixing ratio in the layer itself. The shear in the 650–500 hPa and 550–400 hPa layer was also informative for two locations. In general, the indices were not very informative for the forecast of extreme rains. For the dry season, the relationship between thermodynamic indices and rainfall was not analyzed because it is very scarce at this time of year. The case study showed that in general, the thermodynamic parameters analyzed for each day, responded to the fact of a rainy day in relation to another dry day.