Radar-Observed Characteristics of Precipitation in the Tropical High Andes of Southern Peru and Bolivia
06 Jul 2018-Journal of Applied Meteorology and Climatology (American Meteorological Society)-Vol. 57, Iss: 7, pp 1441-1458
TL;DR: In this article, the vertical structure of precipitation in the tropical Andes of southern Peru and Bolivia was investigated using a vertically pointing 24.1 GHz Micro Rain Radar in Cusco, Peru and La Paz, Bolivia.
Abstract: This study investigates precipitation delivery using the first detailed radar measurements of the vertical structure of precipitation obtained in the tropical Andes of southern Peru and Bolivia. A vertically pointing 24.1 GHz Micro Rain Radar in Cusco, Peru (3,350 m asl, August 2014-February 2015) and La Paz, Bolivia (3,440 m asl, October 2015-February 2017) provided continuous 1-min profiles of reflectivity and Doppler velocity during the respective time periods. Additional datasets collected include thermodynamic profiles from rawinsonde releases, hourly observations of various meteorological variables, and backward air trajectories from the NOAA HYSPLIT model. The vertically-pointing radar time-height data reveal a bimodal diurnal cycle in precipitation with cellular convection predominant in the afternoon and stratiform precipitation predominant overnight. Backward air trajectories for two stratiform case studies indicate that low-level flow originated in the Amazon basin three days prior to the events. Median melting layer heights were above the altitude of nearby glacier termini (~5,000 m) approximately 17% of the time in Cusco and 30% of the time in La Paz, indicating that some precipitation is falling as rain rather than snow on nearby glacier surfaces. Melting layer heights were highest in La Paz during the 2015-16 El Nino (47% above 5,000 m).
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01 Jan 2013
TL;DR: In this article, the authors used 158 multi-spectral satellite images spanning almost 4 decades, from 1975 to 2012, to obtain glacial and lake-area outlines for the understudied Cordillera Vilcanota region, including the Quelccaya Ice Cap.
Abstract: Glaciers in the tropical Andes of southern Peru have received limited attention compared to glaciers in other regions (both near and far), yet remain of vital importance to agriculture, fresh water, and hydropower supplies of downstream communities. Little is known about recent glacial-area changes and how the glaciers in this region respond to climate changes, and, ultimately, how these changes will affect lake and water supplies. To remedy this, we have used 158 multi-spectral satellite images spanning almost 4 decades, from 1975 to 2012, to obtain glacial- and lake-area outlines for the understudied Cordillera Vilcanota region, including the Quelccaya Ice Cap. Additionally, we have estimated the snow-line altitude of the Quelccaya Ice Cap using spectral unmixing methods. We have made the following four key observations: first, since 1988 glacial areas throughout the Cordillera Vilcanota (1988 glacial area: 361 km 2 ) have been declining at a rate of 3.99 ± 1.15 km 2 yr −1 (22 year average, 1988–2010, with 95% confidence interval (CI), n = 8 images). Since 1980, the Quelccaya Ice Cap (1980 glacial area: 63.1 km 2 ) has been declining at a rate of 0.57 ± 0.10 km 2 yr −1 (30 year average, 1980–2010, with 95% CI, n = 14). Second, decline rates for individual glacierized regions have been accelerating during the past decade (2000–2010) as compared to the preceding decade (1988–1999) with an average increase from 37.5 to 42.3 × 10 −3 km 2 yr −1 km −2 (13%). Third, glaciers with lower median elevations are declining at higher rates than those with higher median elevations. Specifically, glaciers with median elevations around 5200 m a.s.l. are retreating to higher elevations at a rate of ~1 m yr −1 faster than glaciers with median elevations around 5400 m a.s.l. Fourth, as glacial regions have decreased, 77% of lakes connected to glacial watersheds have either remained stable or shown a roughly synchronous increase in lake area, while 42% of lakes not connected to glacial watersheds have declined in area (58% have remained stable). Our new and detailed data on glacial and lake areas over 37 years provide an important spatiotemporal assessment of climate variability in this area. These data can be integrated into further studies to analyze inter-annual glacial and lake-area changes and assess hydrologic dependence and consequences for downstream populations.
83 citations
02 Mar 2020
TL;DR: In this paper, a vertically pointed profile radar in the Mantaro basin (Huancayo, Peru) is used to estimate the vertical structure of rain, especially near the surface, for accurate quantitative precipitation estimation.
Abstract: 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 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.
18 citations
Cites background or methods from "Radar-Observed Characteristics of P..."
...[18] developed an algorithm to calculate the top and bottom of the melting layer....
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...[16] showed that a correct estimation of bright band height is essential and can be used in the numerical models to predict the melting of glaciers in the tropical Andes [17,18]....
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...Basically, the most negative gradient in Ze profile is used to estimate the bright band height [18,60]....
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...[18] also used ground-based radar data over the central Andes of southern Peru and Bolivia, and, revealed maxima in rain rate during the afternoon and overnight with short periods of strong convective activity....
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...The altitude with the most negative gradient in Ze and Doppler velocity is termed as the top and bottom of the ML, respectively [18,61]....
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TL;DR: In this paper, four irregularity indices of precipitation, namely concentration index, entropy, persistence index and fractal dimension, were determined according to observed values and then determined their spatial distribution by interpolating following multivariate regression models that consider different geographical variables such as latitude, distance to the Amazon basin, elevation, orientation and curvature.
Abstract: . Northern Chile is one of the most arid regions in the world, as includes the Atacama Desert, but in high altitudes, precipitation is recorded in a very constricted season every year. This makes that water availability is one of the main concerns for policymakers. Accumulated rainfall presents very high differences from one year to another, and this makes that climate projections have a very low degree of confidence in this area. So to this region it is more interesting to study the irregularity of precipitation itself instead of the accumulated rainfall values. According to daily data of 161 meteorological stations, 4 irregularity indices of precipitation were calculated: concentration index, entropy, persistence index and fractal dimension. These indices were determined according to observed values, and then determined their spatial distribution by interpolating following multivariate regression models that consider different geographical variables such as latitude, distance to the Amazon basin, elevation, orientation and curvature. The temporal trends of each index and for each meteorological station were also calculated, and showed different results depending on the latitude and the elevation. These changes agree with the observed modifications on the intertropical atmospheric circulation and with the changes in the precipitation diurnal cycle. These results will help to improve climate projections for these region and to inform the development of water management policies.
16 citations
Cites background or result from "Radar-Observed Characteristics of P..."
...Focusing on the diurnal cycle, sub-daily behaviours are also identified (Endries et al., 2018; Junquas et al., 2018), exposing differences in distribution between day and night, and also linking it to changes in the altitude where the dew point is reached (Wasko et al., 2018)....
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...The regional-scale cyclonic circulation may be strengthened during the afternoon and drive thermal circulations, in accordance with the results of Endries et al. (2018) and Junquas et al. (2018)....
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TL;DR: The tropical Andes of southern Peru and northern Bolivia have several major mountain summits suitable for ice core paleoclimatic investigations as discussed by the authors, however, incomplete understanding of the con...
Abstract: The tropical Andes of southern Peru and northern Bolivia have several major mountain summits suitable for ice core paleoclimatic investigations. However, incomplete understanding of the con...
13 citations
TL;DR: In this paper, the diurnal cycle of convective storms was investigated using ground-based X-band radar, Tropical Rainfall Measuring Mission Precipitation Radar, and reanalysis data during the summer monsoon (June-September of 2014) over complex mountain terrain of Western Ghats, India.
Abstract: Diurnal variation of convective storms (CSs) during monsoon season and associated physical mechanisms are significantly important for accurate forecast of short-time and extreme precipitation. The diurnal cycle of CSs is investigated using ground-based X-band radar, Tropical Rainfall Measuring Mission Precipitation Radar, and reanalysis data during the summer monsoon (June–September of 2014) over complex mountain terrain of Western Ghats, India. Diurnally, CSs show a bimodal distribution in the coastal areas, but this bimodality became weak along the upslope regions and on the mountain top. The first occurrence mode of CSs is in the afternoon–evening hours, while the second peak is in the early-morning hours. The diurnal cycle’s intensity varies with location, such that it reaches maximum in the afternoon–evening hours and early morning on the mountain top and coastal areas, respectively. Two possible mechanisms are proposed for the observed diurnal variation in CSs (a) the radiative cooling effect and (b) the surface wind convergence induced by the interaction between land-sea breeze, local topography and large-scale monsoon winds. It is also observed that the CSs developed on the mountain top during afternoon–evening hours are deeper than those along the coast. The higher moisture in the lower- and mid-troposphere, higher instability and strong upward motion facilitate deeper CSs during afternoon–evening hours.
11 citations
References
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TL;DR: ERA-Interim as discussed by the authors is the latest global atmospheric reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF), which will extend back to the early part of the twentieth century.
Abstract: ERA-Interim is the latest global atmospheric reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF). The ERA-Interim project was conducted in part to prepare for a new atmospheric reanalysis to replace ERA-40, which will extend back to the early part of the twentieth century. This article describes the forecast model, data assimilation method, and input datasets used to produce ERA-Interim, and discusses the performance of the system. Special emphasis is placed on various difficulties encountered in the production of ERA-40, including the representation of the hydrological cycle, the quality of the stratospheric circulation, and the consistency in time of the reanalysed fields. We provide evidence for substantial improvements in each of these aspects. We also identify areas where further work is needed and describe opportunities and objectives for future reanalysis projects at ECMWF. Copyright © 2011 Royal Meteorological Society
22,055 citations
TL;DR: In this article, the authors present a reference guide to users wishing to make use of the Tropical Rainfall Measuring Mission data, which covers each of the three primary rainfall instruments: the passive microwave radiometer, the precipitation radar, and the Visible and Infrared Radiometer System on board the spacecraft.
Abstract: This note is intended to serve primarily as a reference guide to users wishing to make use of the Tropical Rainfall Measuring Mission data. It covers each of the three primary rainfall instruments: the passive microwave radiometer, the precipitation radar, and the Visible and Infrared Radiometer System on board the spacecraft. Radiometric characteristics, scanning geometry, calibration procedures, and data products are described for each of these three sensors.
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TL;DR: This article showed that a doubling in the occurrence of such extreme episodes is caused by increased surface warming of the eastern equatorial Pacific Ocean, which results in the atmospheric conditions required for these event to occur.
Abstract: Extreme El Nino events cause global disruption of weather patterns and affect ecosystems and agriculture through changes in rainfall. Model projections show that a doubling in the occurrence of such extreme episodes is caused by increased surface warming of the eastern equatorial Pacific Ocean, which results in the atmospheric conditions required for these event to occur.
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01 Jan 2013
958 citations
TL;DR: Early radar observations in the Tropics, however, showed large radar echoes composed of convective rain alongside stratiform precipitation, with the stratiform echoes covering great areas and accounting for a large portion of the tropical rainfall as mentioned in this paper.
Abstract: It was once generally thought that stratiform precipitation was something occurring primarily, if not exclusively, in middle latitudes—in baroclinic cyclones and fronts. Early radar observations in the Tropics, however, showed large radar echoes composed of convective rain alongside stratiform precipitation, with the stratiform echoes covering great areas and accounting for a large portion of the tropical rainfall. These observations seemed paradoxical, since stratiform precipitation should not have been occurring in the Tropics, where baroclinic cyclones do not occur. Instead it was falling from convection-generated clouds, generally thought to be too violent to be compatible with the layered, gently settling behavior of stratiform precipitation. In meteorology, convection is a dynamic concept; specifically, it is the rapid, efficient, vigorous overturning of the atmosphere required to neutralize an unstable vertical distribution of moist static energy. Most clouds in the Tropics are convection-generated...
742 citations