Browsing by Autor "Javier Mendoza"

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A New Database of Meteorological and Glaciological Observations: Tarija Glacier, Tropical Andes
(2021) Pablo Fuchs; Javier Mendoza
&lt;p&gt;We present a numerical and geographical database for the Tarija Glacier in the Tropical Andes (68.2&amp;#176; W, 16.2&amp;#176; S, 4820-5380 m.a.s.l.). The database consists of meteorological data, mass balance observations, and variations in glacier front positions. Meteorological data was obtained by an automatic weather station (AWS) located on the glacier surface that includes the following variables: precipitation, temperature, incoming shortwave radiation, relative humidity, wind speed and wind direction. Mass balance for this glacier was observed on a monthly basis in an ablation stake network and annually in a snow pit at 5230 m.a.s.l. The glacier front topography was monitored annually using a DGPS survey. We set up the database using the relational database engine PostgreSQL which is capable of managing geospatial data through the PostGIS extension. The SAGA system was used for image analysis and mapping. Data quality control and further processing was carried out in the R environment which has interfaces to the PostgreSQL database system and SAGA, as well as several additional packages for statistical analyses and modelling. The database contains data spanning the 2011-2018 period and would be useful for multiple applications including environmental and ecological modeling, water resources assessment, and climate change studies.&lt;/p&gt;
Age-growth relationships, temperature sensitivity and palaeoclimate-archive potential of the threatened Altiplano cactusEchinopsis atacamensis
(Oxford University Press, 2020) Nathan B. English; David L. Dettman; Quan Hua; Javier Mendoza; D.M. Muir; Kevin R. Hultine; David G. Williams
The tall (>4 m), charismatic and threatened columnar cacti, pasacana [Echinopsis atacamensis (Vaupel) Friedrich & G.D. Rowley)], grows on the Bolivian Altiplano and provides environmental and economic value to these extremely cold, arid and high-elevation (~4000 m) ecosystems. Yet very little is known about their growth rates, ages, demography and climate sensitivity. Using radiocarbon in spine dating time series, we quantitatively estimate the growth rate (5.8 and 8.3 cm yr-1) and age of these cacti (up to 430 years). These data and our field measurements yield a survivorship curve that suggests precipitation on the Altiplano is important for this species' recruitment. Our results also reveal a relationship between nighttime temperatures on the Altiplano and the variation in oxygen isotope values in spines (δ18O). The annual δ18O minimums from 58 years of in-series spine tissue from pasacana on the Altiplano provides at least decadal proxy records of temperature (r = 0.58; P < 0.0001), and evidence suggests that there are longer records connecting modern Altiplano temperatures to sea-surface temperatures (SSTs) in the Atlantic Ocean. While the role of Atlantic SSTs on the South American Summer Monsoon (SASM) and precipitation on the Bolivian Altiplano is well described, the impact of SSTs on Altiplano temperatures is disputed. Understanding the modern impact of SSTs on temperature on the Altiplano is important to both understand the impact of future climate change on pasacana cactus and to understand past climate changes on the Altiplano. This is the best quantitative evidence to date of one of the oldest known cactus in the world, although there are likely many older cacti on the Altiplano, or elsewhere, that have not been sampled yet. Together with growth, isotope and age data, this information should lead to better management and conservation outcomes for this threatened species and the Altiplano ecosystem.
BACKSCATTER CHARASTARISTICS OF A TROPICAL GLACIER DERIVED FROM C-BAND SAR IMAGERY
(2018) Shota Funaki; Yoshihiro ASAOKA; Hiroyuki Wakabayashi; Tuyoshi KINOUCHI; Javier Mendoza
雨季の短期・中期的な氷河融解量推定の精度向上に資するため，C-band SARを用いて2015年から2016年の熱帯氷河の後方散乱特性の解析および雪線高度の推定を行った．HuaynaPotosi West氷河を対象として，空間平均の後方散乱係数は，雨季の前半期間(11月～1月)に減少し，後半期間(2月～4月)に増加，乾季の期間は減少する傾向を示した．次に，氷河の縦断線上の後方散乱係数を抽出し，4パターンの階級値(階級幅4, 2, 1, 0.5dB)のヒストグラムを作成し，後方散乱係数の累積相対度数(0.5以上)を用いて乾季および雨季の平均的な雪線を決定する閾値を決定した．累積相対度数の階級幅を1dBおよび0.5dBとして，雨季と乾季の両時期の雪線高度を推定した．以上よりSentinel-1A, B C-band SARから得られる後方散乱係数が熱帯氷河における雪線高度の抽出に有効であることを示した．
Clima y variabilidad espacial de la ceja de monte y andino húmedo
(2019) Jorge Molina‐Carpio; Daniel Espinoza; Enrique Coritza; Franklin Salcedo; Cristian Farfán; Leonardo Mamani; Javier Mendoza
Climate and spatial variability of the humid upper Andes
(2019) Jorge Molina‐Carpio; Daniel Espinoza; Enrique Coritza; Franklin Salcedo; Cristian Farfán; Leonardo Mamani; Javier Mendoza
Glacier Mass Balance and Catchment-Scale Water Balance in Bolivian Andes
(Fuji Technology Press Ltd., 2016) Tong Liu; Tsuyoshi Kinouchi; Javier Mendoza; Yoichi Iwami
In investigating glacier mass balance and water balance at Huayna Potosi West, a glacierized basin in the Bolivian Andes (Cordillera Real), we used a remote sensing method with empirical area-volume relationships, a hydrological method with runoff coefficients, and water balance method. Results suggest that remote sensing method based on the glacier area from satellite images and area-volume relationships is too imprecise to use in performing analysis in short time intervals. Glacier mass balance obtained using a new area-volume relationship was, however, similar to that obtained by the water balance method, thus proving that the new area-volume relationship is reasonable to use for analyzing glaciers within a certain size range. The hydrological method with a runoff coefficient considered glacier as the only storage for saving or contributing to runoff and nonglacier area as the only source of evaporation. We applied a fixed runoff coefficient of 0.8 without considering wet or dry seasons in nonglacier areas – a method thus sensitive to meteorological and hydrological data. We also did not consider glacier sublimation. The water balance method is applicable to the study region and excelled other methods in terms of resolution, having no empirical coefficients, and considering sublimation and evaporation. Among its few limitations are possibly underestimating evaporation and runoff over nonglacier areas during wet months and thus possibly overestimating glacier contribution at mean time.
IMPACT OF GLACIER DISAPPEARANCE ON RUNOFF FROM A GLACIERIZED CATCHMENT IN THE ANDES
(2013) Tsuyoshi Kinouchi; Fabiola Ledezma; Tong Liu; Javier Mendoza
We predicted the hydrological impact of glacier retreat in the glacierized catchment located in Bolivian Andes by applying a grid-based physically distributed runoff model. The capability of the model was improved by including snow and ice melt processes, in which temperature, solar radiation and humidity were taken into accounts based on our field observation. Runoff retarding by the freezing soil was also considered. Given hourly meteorological conditions and spatial distributions of land cover, precipitation and air temperature, the model result agreed well with observed flow rates. After the full glacier retreat, the flow rate is estimated to be significantly reduced in the dry season while the impact is less in the wet season. We found that glacier melts mostly occurred in the early stage of the wet season. In addition to glacier disappearance, the rise in air temperature increased the discharge during major precipitation events but reduced the amount of snow accumulated over the catchment.
Small glaciers disappearing in the tropical Andes: a case-study in Bolivia: Glaciar Chacaltaya (16o S)
(Cambridge University Press, 2001) Edson Ramírez; Bernard Francou; Pierre Ribstein; Marc Descloîtres; Roger Guérin; Javier Mendoza; Robert Gallaire; Bernard Pouyaud; Ekkehard Jordan
Abstract Glaciar Chacaltaya is an easily accessible glacier located close to La Paz, Bolivia. Since 1991, information has been collected about the evolution of this glacier since the Little Ice Age, with a focus on the last six decades. The data considered in this study are monthly mass-balance measurements, yearly mappings of the surface topography and a map of the glacier bed given by ground-penetrating radar survey. A drastic shrinkage of ice has been observed since the early 1980s, with a mean deficit about 1 m a −1 w.e. From 1992 to 1998, the glacier lost 40% of its average thickness and two-thirds of its total volume, and the surface area was reduced by >40%. With a mean estimated equilibrium-line altitude lying above its upper reach, the glacier has been continuously exposed to a dominant ablation on the whole surface area. If the recent climatic conditions continue, a complete extinction of this glacier in the next 15 years can be expected. Glaciar Chacaltaya is representative of the glaciers of the Bolivian eastern cordilleras, 80% of which are small glaciers (<0.5 km 2 ). A probable extinction of these glaciers in the near future could seriously affect the hydrological regime and the water resources of the high-elevation basins.
Tropical climate change recorded by a glacier in the central Andes during the last decades of the twentieth century: Chacaltaya, Bolivia, 16°S
(American Geophysical Union, 2003) Bernard Francou; Mathias Vuille; Patrick Wagnon; Javier Mendoza; Jean‐Emmanuel Sicart
The reasons for the accelerated glacier retreat observed since the early 1980s in the tropical Andes are analyzed based on the well‐documented Chacaltaya glacier (Bolivia). Monthly mass balance measurements available over the entire 1991–2001 decade are interpreted in the light of a recent energy balance study performed on nearby Zongo glacier and further put into a larger‐scale context by analyzing the relationship with ocean‐atmosphere dynamics over the tropical Pacific‐South American domain. The strong interannual variability observed in the mass balance is mainly dependent on variations in ablation rates during the austral summer months, in particular during DJF. Since high humidity levels during the summer allow melting to be distinctly predominant over sublimation, net all‐wave radiation, via albedo and incoming long‐wave radiation, is the main factor that governs ablation. Albedo depends on snowfall and a deficit during the transition period and in the core of the wet season (DJF) maintains low albedo surfaces of bare ice, which in turn leads to enhanced absorption of solar radiation and thus to increased melt rates. On a larger spatial scale, interannual glacier evolution is predominantly controlled by sea surface temperature anomalies (SSTA) in the eastern equatorial Pacific (Niño 1+2 region). The glacier mass balance is influenced by tropical Pacific SSTA primarily through changes in precipitation, which is significantly reduced during El Niño events. The more frequent occurrence of El Niño events and changes in the characteristics of its evolution, combined with an increase of near‐surface temperature in the Andes, are identified as the main factors responsible for the accelerated retreat of Chacaltaya glacier.
Water security in high mountain cities of the Andes under a growing population and climate change: A case study of La Paz and El Alto, Bolivia
(Elsevier BV, 2019) Tsuyoshi Kinouchi; Takashi Y. Nakajima; Javier Mendoza; Pablo Fuchs; Yoshihiro ASAOKA