Browsing by Autor "Marcos Andrade"

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A decade of atmospheric composition observations in the undersampled Central Andes
(2022) Marcos Andrade; Diego Aliaga; Luis Blacutt; Ricardo Forno; René Gutierrez; Fernando Velarde; Isabel Moreno; Laura Ticona; Alfred Wiedensohler; Radovan Krejčí
&lt;p&gt;Ten years of almost continuous observations at the highest Global Atmosphere Watch Regional station in the world are presented here. The Chacaltaya observatory (5240 m asl, 16.3&amp;#186;S, 68.1&amp;#186;W) was set up in December 2011. It is currently the only operational station characterizing optical and chemical properties of climate-relevant aerosol and gases in Bolivia and in a radius of about 1500 kilometers from the station. The observations show a clear influence of the well-marked dry and wet meteorological seasons. In addition, the impact on the Andean mountains of long and mid-range transport of biomass burning products from the lowlands is clearly recorded in different parameters measured at the station. Furthermore, the nearby presence of the largest metropolitan area in the region (~1.8 million inhabitants) is observed almost on a daily basis, and therefore different campaigns were carried out to characterize the area and its influence on our measurements. Specific results from these campaigns are discussed elsewhere. Finally, the topographic complexity represents an important challenge for modeling efforts in order to understand sources and sinks (and associated processes) of the observed parameters, requiring not only high spatial resolution and the correct choice of model options, but a novel way of interpreting these results. The decade of collaboration of an international consortium made it possible to keep the station running successfully. The challenge is now to preserve its functioning for the coming decades in a region with historically few high-quality observations while disrupting environmental and socio-economic changes take place.&lt;/p&gt;
A European aerosol phenomenology – 6: scattering properties of atmospheric aerosol particles from 28 ACTRIS sites
(Copernicus Publications, 2018) Marco Pandolfi; Lucas Alados‐Arboledas; Andrés Alástuey; Marcos Andrade; Christo Angelov; Begoña Artı́ñano; John Backman; Urs Baltensperger; Paolo Bonasoni; Nicolas Bukowiecki
Abstract. This paper presents the light-scattering properties of atmospheric aerosol particles measured over the past decade at 28 ACTRIS observatories, which are located mainly in Europe. The data include particle light scattering (σsp) and hemispheric backscattering (σbsp) coefficients, scattering Ångström exponent (SAE), backscatter fraction (BF) and asymmetry parameter (g). An increasing gradient of σsp is observed when moving from remote environments (arctic/mountain) to regional and to urban environments. At a regional level in Europe, σsp also increases when moving from Nordic and Baltic countries and from western Europe to central/eastern Europe, whereas no clear spatial gradient is observed for other station environments. The SAE does not show a clear gradient as a function of the placement of the station. However, a west-to-east-increasing gradient is observed for both regional and mountain placements, suggesting a lower fraction of fine-mode particle in western/south-western Europe compared to central and eastern Europe, where the fine-mode particles dominate the scattering. The g does not show any clear gradient by station placement or geographical location reflecting the complex relationship of this parameter with the physical properties of the aerosol particles. Both the station placement and the geographical location are important factors affecting the intra-annual variability. At mountain sites, higher σsp and SAE values are measured in the summer due to the enhanced boundary layer influence and/or new particle-formation episodes. Conversely, the lower horizontal and vertical dispersion during winter leads to higher σsp values at all low-altitude sites in central and eastern Europe compared to summer. These sites also show SAE maxima in the summer (with corresponding g minima). At all sites, both SAE and g show a strong variation with aerosol particle loading. The lowest values of g are always observed together with low σsp values, indicating a larger contribution from particles in the smaller accumulation mode. During periods of high σsp values, the variation of g is less pronounced, whereas the SAE increases or decreases, suggesting changes mostly in the coarse aerosol particle mode rather than in the fine mode. Statistically significant decreasing trends of σsp are observed at 5 out of the 13 stations included in the trend analyses. The total reductions of σsp are consistent with those reported for PM2.5 and PM10 mass concentrations over similar periods across Europe.
A European aerosol phenomenology – 6: scattering properties of atmospheric aerosol particles from 28 ACTRIS sites
(European Organization for Nuclear Research, 2018) Marco Pandolfi; Lucas Alados‐Arboledas; Andrés Alástuey; Marcos Andrade; Christo Angelov; Begoña Artı́ñano; John Backman; Urs Baltensperger; Paolo Bonasoni; Nicolas Bukowiecki
This paper presents the light-scattering properties of atmospheric aerosol particles measured over the past decade at 28 ACTRIS observatories, which are located mainly in Europe. The data include particle light scattering (sp) and hemispheric backscattering (bsp) coefficients, scattering Ångström exponent (SAE), backscatter fraction (BF) and asymmetry parameter (g). An increasing gradient of sp is observed when moving from remote environments (arctic/mountain) to regional and to urban environments. At a regional level in Europe, sp also increases when moving from Nordic and Baltic countries and from western Europe to central/eastern Europe, whereas no clear spatial gradient is observed for other station environments. The SAE does not show a clear gradient as a function of the placement of the station. However, a west-to-east-increasing gradient is observed for both regional and mountain placements, suggesting a lower fraction of fine-mode particle in western/south-western Europe compared to central and eastern Europe, where the fine-mode particles dominate the scattering. The g does not show any clear gradient by station placement or geographical location reflecting the complex relationship of this parameter with the physical properties of the aerosol particles. Both the station placement and the geographical location are important factors affecting the intraannual variability. At mountain sites, higher sp and SAE values are measured in the summer due to the enhanced boundary layer influence and/or new particle-formation episodes. Conversely, the lower horizontal and vertical dispersion during winter leads to higher sp values at all low-altitude sites in central and eastern Europe compared to summer. These sites also show SAE maxima in the summer (with corresponding g minima). At all sites, both SAE and g show a strong variation with aerosol particle loading. The lowest values of g are always observed together with low sp values, indicating a larger contribution from particles in the smaller accumulation mode. During periods of high sp values, the variation of g is less pronounced, whereas the SAE increases or decreases, suggesting changes mostly in the coarse aerosol particle mode rather than in the fine mode. Statistically significant decreasing trends of sp are observed at 5 out of the 13 stations included in the trend analyses. The total reductions of sp are consistent with those reported for PM2:5 and PM10 mass concentrations over similar periods across Europe.
A European aerosol phenomenology-6: Scattering properties of atmospheric aerosolparticles from 28 ACTRIS sites
(2017) Marco Pandolfi; Lucas Alados‐Arboledas; Andrés Alástuey; Marcos Andrade; Begoña Artı́ñano; John Backman; Urs Baltensperger; Paolo Bonasoni; Nicolas Bukowiecki; Martine Collaud Coen
Abstract. This paper presents the light scattering properties of atmospheric aerosol particles measured over the past decade at 28 ACTRIS observatories, located mainly in Europe. The data include particle light scattering (σsp) and hemispheric backscattering (σbsp) coefficients, scattering Ångström exponent (SAE), backscatter fraction (BF) and asymmetry parameter (g). A large range of ssp was observed across the network. Low ssp values were on average measured in Nordic and Baltic countries and in Western Europe whereas the highest σsp were measured at regional sites in eastern and central Europe. In these regional areas the SAE was also high indicating the predominance of fine-mode particles. On average, the SAE was lower in the Nordic and Baltic, western and southern countries suggesting a lower fraction of fine-mode particle compared to central and eastern Europe. An increasing gradient of ssp was observed when moving from mountain to regional and to urban sites. Conversely, the mass-independent SAE and g parameters did not show the same gradient. At all sites, both SAE and g varied greatly with aerosol particle loading. The lowest values of g were always observed under low ssp indicating a larger contribution from particles in the smaller accumulation mode. Then, g steeply increased with increasing ssp indicating a progressive shift of the particle size distribution toward the larger end of the accumulation mode. Under periods of high particle mass concentrations, the variation of g was less pronounced whereas the SAE increased or decreased suggesting changes mostly in the coarse aerosol particles mode rather than in the fine mode. The station placement seemed to be the main parameter affecting the intra-annual variability. At mountain sites, higher σsp was measured in summer mainly because of the enhanced boundary layer influence. Conversely, less horizontal and vertical dispersion in winter led to higher σsp at all low altitude sites in central and eastern Europe compared to summer. On average, these sites also showed SAE maxima in summer (and correspondingly g minima). Large intra-annual variability of SAE and g was observed also at Nordic and Baltic countries due to seasonal-dependent transport of different air masses to these remote sites. Statistically significant decreasing trends of σsp were observed at 5 out of 13 stations included in trend analyses. The total reductions of ssp were consistent with those reported for PM2.5 and PM10 mass concentrations over similar periods across Europe.
Air pollution levels in South America
(Elsevier BV, 2025) Néstor Y. Rojas; S.Enrique Puliafito; María Cazorla; Andrea Pineda-Rojas; Thiago Nogueira; Caroline Wikuats; Valeria Mardoñez-Balderrama; Marcos Andrade; Rodrigo Seguel; Jhojan Rojas
Antimicrobial resistance genes are enriched in aerosols near impacted urban surface waters in La Paz, Bolivia
(Elsevier BV, 2021) Olivia Ginn; Dennis Nichols; Lucas Rocha-Melogno; Aaron Bivins; David Berendes; Freddy Soria; Marcos Andrade; Marc A. Deshusses; Mike Bergin; Joe Brown
Bioaerosol sampling optimization for community exposure assessment in cities with poor sanitation: A one health cross-sectional study
(Elsevier BV, 2020) Lucas Rocha-Melogno; Olivia Ginn; Emily S. Bailey; Freddy Soria; Marcos Andrade; Michael Bergin; Joe Brown; Gregory C. Gray; Marc A. Deshusses
Biomass-burning and urban emission impacts in the Andes Cordillera region based on in-situ measurements from the Chacaltaya observatory, Bolivia (5240 m a.s.l.)
(2019) Chauvigné Aurélien; Diego Aliaga; Marcos Andrade; Patrick Ginot; Radovan Krejčí; Griša Močnik; Nadège Montoux; Isabel Moreno; Thomas Müller; Marco Pandolfi
Abstract. We present the variability of aerosol particle optical properties measured at the global Atmosphere Watch (GAW) station Chacaltaya (5240 m a.s.l.). The in-situ mountain site is ideally located to study regional impacts of the densely populated urban area of La Paz/El Alto, and the intensive activity in the Amazonian basin. Four year measurements allow to study aerosol particle properties for distinct atmospheric conditions as stable and turbulent layers, different airmass origins, as well as for wet and dry seasons, including biomass-burning influenced periods. The absorption, scattering and extinction coefficients (median annual values of 0.74, 12.14 and 12.96 Mm−1 respectively) show a clear seasonal variation with low values during the wet season (0.57, 7.94 and 8.68 Mm−1 respectively) and higher values during the dry season (0.80, 11.23 and 14.51 Mm−1 respectively). These parameters also show a pronounced diurnal variation (maximum during daytime, minimum during night-time, as a result of the dynamic and convective effects of leading to lower atmospheric layers reaching the site during daytime. Retrieved intensive optical properties are significantly different from one season to the other, showing the influence of different sources of aerosols according to the season. Both intensive and extensive optical properties of aerosols were found to be different among the different atmospheric layers. The particle light absorption, scattering and extinction coefficients are in average 1.94, 1.49 and 1.55 times higher, respectively, in the turbulent layer compared to the stable layer. We observe that the difference is highest during the wet season and lowest during the dry season. Using wavelength dependence of aerosol particle optical properties, we discriminated contributions from natural (mainly mineral dust) and anthropogenic (mainly biomass-burning and urban transport or industries) emissions according to seasons and tropospheric layers. The main sources influencing measurements at CHC are arising from the urban area of La Paz/El Alto, and regional biomass-burning from the Amazonian basin. Results show a 28 % to 80 % increase of the extinction coefficients during the biomass-burning season with respect to the dry season, which is observed in both tropospheric layers. From this analyse, long-term observations at CHC provides the first direct evidence of the impact of emissions in the Amazonian basin on atmospheric optical properties far away from their sources, all the way to the stable layer.
Black carbon emission and transport mechanisms to the free troposphere at the La Paz/El Alto (Bolivia) metropolitan area based on the Day of Census (2012)
(Elsevier BV, 2018) Alfred Wiedensohler; Marcos Andrade; Kay Weinhold; Thomas Müller; W. Birmili; Fernando Velarde; Isabel Moreno; Ricardo Forno; Maria Fernanda Sanchez Barrero; Paolo Laj
Urban development, growing industrialization, and increasing demand for mobility have led to elevated levels of air pollution in many large cities in Latin America, where air quality standards and WHO guidelines are frequently exceeded. The conurbation of the metropolitan area of La Paz/El Alto is one of the fastest growing urban settlements in South America with the particularity of being located in a very complex terrain at a high altitude. As many large cities or metropolitan areas, the metropolitan area of La Paz/El Alto and the Altiplano region are facing air quality deterioration. Long-term measurement data of the equivalent black carbon (eBC) mass concentrations and particle number size distributions (PNSD) from the Global Atmosphere Watch Observatory Chacaltaya (CHC; 5240 m a.s.l., above sea level) indicated a systematic transport of particle matter from the metropolitan area of La Paz/El Alto to this high altitude station and subsequently to the lower free troposphere. To better understand the sources and the transport mechanisms, we conducted eBC and PNSDs measurements during an intensive campaign at two locations in the urban area of La Paz/El Alto from September to November 2012. While the airport of El Alto site (4040 m a.s.l.) can be seen as representative of the urban and Altiplano background, the road site located in Central La Paz (3590 m a.s.l.) is representative for heavy traffic-dominated conditions. Peaks of eBC mass concentrations up to 5 μg m−3 were observed at the El Alto background site in the early morning and evening, while minimum values were detected in the early afternoon, mainly due to thermal convection and change of the planetary boundary layer height. The traffic-related eBC mass concentrations at the road site reached maximum values of 10–20 μg m−3. A complete traffic ban on the specific Bolivian Day of Census (November 21, 2012) led to a decrease of eBC below 1 μg m−3 at the road site for the entire day. Compared to the day before and after, particle number concentrations decreased by a factor between 5 and 25 over the particle size range from 10 to 800 nm, while the submicrometer particle mass concentration dropped by approximately 80%. These results indicate that traffic is the dominating source of BC and particulate air pollution in the metropolitan area of La Paz/El Alto. In general, the diurnal cycle of eBC mass concentration at the Chacaltaya observatory is anti-correlated to the observations at the El Alto background site. This pattern indicates that the traffic-related particulate matter, including BC, is transported to higher altitudes with the developing of the boundary layer during daytime. The metropolitan area of La Paz/El Alto seems to be a significant source for BC of the regional lower free troposphere. From there, BC can be transported over long distances and exert impact on climate and composition of remote southern hemisphere.
Breakdown of a Nocturnal Inversion Measured with a Low-Cost Tethersonde System: A High School Student Experiment
(American Meteorological Society, 2022) David N. Whiteman; Kofi Boateng; Sara Harbison; Hadijat Oke; Audrey Rappaport; Monique Watson; Ayomiposi Ajayi; Oluwafisayo Okunuga; Ricardo Forno; Marcos Andrade
Abstract For the past 4 years, four different cohorts of students from the Science and Technology program at Eleanor Roosevelt High School in Greenbelt, Maryland, have performed their senior research projects at the Howard University Beltsville Research Campus in Beltsville, Maryland. The projects have focused generally on the testing and correction of low-cost sensors and development of instrumentation for use in profiling the lower atmosphere. Specifically, we have developed a low-cost tethersonde system and used it to carry aloft a low-cost instrument that measures particulate matter (PM) as well as a standard radiosonde measuring temperature, pressure, and relative humidity. The low-cost PM sensor was found to provide artificially high values of PM under conditions of elevated relative humidity, likely due to the presence of hygroscopic aerosols. Reference measurements of PM were used to develop a correction technique for the low-cost PM sensor. Profiling measurements of temperature and PM during the breakdown of a nocturnal inversion were performed using the tethersonde system on 30 August 2019. The evolution of temperature during the breakdown of the inversion was studied and compared with model forecasts. The attempt to measure PM during the tethersonde experiment was not successful, we believe, due to the packaging of the low-cost sensor. Future cohorts of students from Eleanor Roosevelt High School students will work on improving the instrumentation and measurements shown here as we continue the collaboration between the Howard University Beltsville Campus and the local school system.
CAMPAÑA DE MEDICIONES ATMOSFÉRICAS EN LOS ANDES BOLIVIANOS REALIZADA POR EQUIPO ESTUDIANTIL BOLIVIANO-ESTADOUNIDENSE
(2024) David N. Whiteman; Marcos Andrade; Ricardo Forno; MAMANI-PACO; BLACUTT; René Gutierrez; Decker Guzmán Zabalaga
A student-focused field measurement campaign was held in the vicinity of Mt. Chacaltaya in the Bolivian Andes near the city of La Paz on May 24, 2022. The campaign was part of a program funded by the US Department of State, the main goal of which was to foster cultural and scientific exchange among Bolivian and US students. As part of this exchange, a group of eight Bolivian and four U.S. students worked together to plan and execute measurements which focused on quantifying the flow of particulate matter from the city of La Paz toward the summit of Mt. Chacaltaya, where the world’s highest elevation Global Atmosphere Watch site is located. Measurements were performed at three locations along a canyon that leads toward the summit of Mt. Chacaltaya and is a natural pathway for city-generated pollutants to travel toward the GAW station. The measurements indicated the presence of regular, solarheating-generated, downslope/upslope wind flow that aids the movement of particles near the mountain surface. The development of convection during the afternoon regularly decreased the concentrations measured at the surface and thus complicated the interpretation of particle flows. A novel, low-cost tethersonde apparatus was developed by members of the Laboratory for Atmospheric Physics (LFA) at the Universidad Mayor de San Andres (UM- ´ SA). Use of this tethersonde permitted vertical profiles of winds, temperature, pressure and relative humidity to be acquired thus allowing the investigation of the vertical structure of the transition between downslope and upslope flow. Outside of the measurement campaign, the students engaged in cultural activities together to enjoy local Bolivian sites and get to know each other better. One of the goals of the experiment was to increase interest in the atmospheric sciences among UMSA students. The results of a post-campaign survey indicate that participation in this joint field campaign has increased the number of physics students participating in the activities of the LFA at UMSA
CARACTERIZACIÓN DE LA CONCENTRACIÓN DE OZONO SUPERFICIAL EN LA CIUDAD DE LA PAZ EN EL RÉGIMEN DE MADRUGADA
(2011) Wilmer Tapia Portugal; Marcos Andrade
Se estudi´o el comportamiento del ozono superficial medido en la zona central de la ciudad de La Paz (3630 msnm, 16◦29′01′′ S 68◦08′01′′ O) en el r´egimen de madrugada definido por el periodo de 00 : 00 a 06 : 00 a.m. La raz´on para elegir este periodo se debe a la presencia de un m´aximo relativo alrededor de las 03 : 00 a.m. que aparece de manera casi permanente en las observaciones. Este pico no es evidente en datos de una estaci´on ubicada en las afueras de la ciudad. Para el estudio se usaron datos horarios entre los a ˜nos 2007 y 2010. Los resultados obtenidos sugieren que la concentraci´on de ozono observada durante la madrugada es producto de la generaci´on de ozono durante el r´egimen diurno del d´ia anterior el cual ser´ia transportado hacia las partes altas de la ciudad por los vientos de valle. La masa de aire que conteniendo este aire contaminado ser´ia atrapada en esta regi´on y transportada de retorno hacia el centro de la ciudad en horas de la madrugada del d´ia siguiente. El comportamiento t´ipico del pico an´omalo de ozono muestra una fuerte anticorrelaci´on entre ozono superficial ymon´oxido de nitr´ogeno. Por otro lado,medidas del tr´afico vehicular en el r´egimen de madrugada muestran claramente a una correlaci´on positiva con la concentraci´on de NO. Esto sugiere que la reducci´on observada del pico de ozono de la madrugada durante los fines de semana est ´a relacionada con el incremento de tr´afico vehicular en ese periodo
CCN production by new particle formation in the free troposphere
(Copernicus Publications, 2017) Clémence Rose; Karine Sellegri; Isabel Moreno; Fernando Velarde; Michel Ramonet; Kay Weinhold; Radovan Krejčí; Marcos Andrade; Alfred Wiedensohler; Patrick Ginot
Abstract. Global models predict that new particle formation (NPF) is, in some environments, responsible for a substantial fraction of the total atmospheric particle number concentration and subsequently contributes significantly to cloud condensation nuclei (CCN) concentrations. NPF events were frequently observed at the highest atmospheric observatory in the world, on Chacaltaya (5240 m a.s.l.), Bolivia. The present study focuses on the impact of NPF on CCN population. Neutral cluster and Air Ion Spectrometer and mobility particle size spectrometer measurements were simultaneously used to follow the growth of particles from cluster sizes down to ∼ 2 nm up to CCN threshold sizes set to 50, 80 and 100 nm. Using measurements performed between 1 January and 31 December 2012, we found that 61 % of the 94 analysed events showed a clear particle growth and significant enhancement of the CCN-relevant particle number concentration. We evaluated the contribution of NPF, relative to the transport and growth of pre-existing particles, to CCN size. The averaged production of 50 nm particles during those events was 5072, and 1481 cm−3 for 100 nm particles, with a larger contribution of NPF compared to transport, especially during the wet season. The data set was further segregated into boundary layer (BL) and free troposphere (FT) conditions at the site. The NPF frequency of occurrence was higher in the BL (48 %) compared to the FT (39 %). Particle condensational growth was more frequently observed for events initiated in the FT, but on average faster for those initiated in the BL, when the amount of condensable species was most probably larger. As a result, the potential to form new CCN was higher for events initiated in the BL (67 % against 53 % in the FT). In contrast, higher CCN number concentration increases were found when the NPF process initially occurred in the FT, under less polluted conditions. This work highlights the competition between particle growth and the removal of freshly nucleated particles by coagulation processes. The results support model predictions which suggest that NPF is an effective source of CCN in some environments, and thus may influence regional climate through cloud-related radiative processes.
Characteristics of Precipitating Storms in Glacierized Tropical Andean Cordilleras of Peru and Bolivia
(Taylor & Francis, 2017) L. Baker Perry; Anton Seimon; Marcos Andrade; Jason L. Endries; Sandra E. Yuter; Fernando Velarde; Sandro Arias; Martí Bonshoms; Eric J. Burton; I. Ronald Winkelmann
Precipitation variability in tropical high mountains is a fundamental yet poorly understood factor influencing local climatic expression and a variety of environmental processes, including glacier behavior and water resources. Precipitation type, diurnality, frequency, and amount influence hydrological runoff, surface albedo, and soil moisture, whereas cloud cover associated with precipitation events reduces solar irradiance at the surface. Considerable uncertainty remains in the multiscale atmospheric processes influencing precipitation patterns and their associated regional variability in the tropical Andes—particularly related to precipitation phase, timing, and vertical structure. Using data from a variety of sources—including new citizen science precipitation stations; new high-elevation comprehensive precipitation monitoring stations at Chacaltaya, Bolivia, and the Quelccaya Ice Cap, Peru; and a vertically pointing Micro Rain Radar—this article synthesizes findings from interdisciplinary research activities in the Cordillera Real of Bolivia and the Cordillera Vilcanota of Peru related to the following two research questions: (1) How do the temporal patterns, moisture source regions, and El Niño-Southern Oscillation relationships with precipitation occurrence vary? (2) What is the vertical structure (e.g., reflectivity, Doppler velocity, melting layer heights) of tropical Andean precipitation and how does it evolve temporally? Results indicate that much of the heavy precipitation occurs at night, is stratiform rather than convective in structure, and is associated with Amazonian moisture influx from the north and northwest. Improving scientific understanding of tropical Andean precipitation is of considerable importance to assessing climate variability and change, glacier behavior, hydrology, agriculture, ecosystems, and paleoclimatic reconstructions.
Climate regionalization in Bolivia: A combination of non‐hierarchical and consensus clustering analyses based on precipitation and temperature
(Wiley, 2019) Azar M. Abadi; Clinton M. Rowe; Marcos Andrade
Abstract Climate regionalization is an inseparable part of many climate change and environmental studies. Delineating climatologically homogeneous regions enhances the utility of such studies and reduces the biases due to the uncertainties associated with climate model outputs at individual grid points which both lead to better understanding of the atmospheric mechanisms affecting a region's climate. Throughout time, researchers and statisticians have developed different methods to perform regionalization in which the techniques are highly dependent on the nature and accessibility of the data. This research aims to divide Bolivia into smaller, coherent climate subdivisions. To achieve this goal, we first apply the non‐hierarchical k ‐means clustering method to climatologies of monthly accumulated precipitation and monthly average temperature separately using a gridded observation dataset for Bolivia spanning from 1979 to 2010. The clustering is performed on the two variables separately to avoid arbitrary attribute scaling and information redundancy as well as to gain a better understanding of these individual variables across Bolivia. Consensus clustering then finds the categorical intersection of the two independent clusters to create homogeneous climate regions. Results from this study show that Bolivia can be divided into 10 climatically distinguishable subdivisions largely explicable by topography and latitude, which are the key climate control factors in the region.
Comment on egusphere-2023-1298
(2023) Isabel Moreno; Radovan Krejčí; Jean‐Luc Jaffrezo; Gaëlle Uzu; Andrés Alástuey; Marcos Andrade; Valeria Mardóñez; Alkuin Maximilian Koenig; Diego Aliaga; Claudia Mohr
Abstract. The chemical composition of PM10 and PM2.5 was studied at the summit of Mt. Chacaltaya (5380 masl, lat.-16.346950º, lon. -68.128250º) providing a unique long-term record spanning from December 2011 to March 2020. The chemical composition of aerosol at the Chacaltaya GAW site is representative of the regional background, seasonally affected by biomass burning practices and by nearby anthropogenic emissions from the metropolitan area of La Paz – El Alto. Concentration levels are clearly influenced by seasons with minimum occurring during the wet season (December to March) and maxima occurring during the dry and transition seasons (April to November). Ions, total carbon (EC+OC) and saccharide concentrations range between 558–1785, 384–1120 and 4.3–25.5 ng m-3 for bulk PM10 and 917–2308, 519–1175 and 3.9–24.1 ng m-3 for PM2.5, respectively. Such concentrations are overall lower compared to other high-altitude stations around the globe, but higher than Amazonian remote sites (except for OC). For PM10, there is dominance of insoluble mineral matter (33–56 % of the mass), organic matter (7–34 %) and secondary inorganic aerosol (15–26 %). Chemical composition profiles were identified for different origins: EC, NO3-, NH4+, glucose, C2O4-2 for the nearby urban and rural areas; OC, EC, NO3-, K+, acetate, formiate, levoglucosan, some F- and Br- for biomass burning; MeSO3-, Na+, Mg2+, Br- for aged marine emissions from the Pacific Ocean; arabitol, mannitol, K+ for biogenic emissions; Na+, Ca2+, Mg2+ for soil dust, and SO42-, F-, and some Cl- for volcanism. Regional biomass-burning practices influence the soluble fraction of the aerosol particularly between July and September. The organic fraction is present all year round and has both anthropogenic (biomass burning and other combustion sources) and natural (primary and secondary biogenic emissions) origins, with the OC/EC mass ratio being practically constant all year round (10.5±38.9). Peruvian volcanism dominates the SO42- concentration since 2014, though it presents a strong temporal variability due to the intermittence of the sources and seasonal changes on the transport patterns. These measurements represent some of the first long-term observations of aerosol chemical composition at a continental high-altitude site in the tropical Southern hemisphere.
Comment on egusphere-2023-1298
(2023) Isabel Moreno; Radovan Krejčí; Jean‐Luc Jaffrezo; Gaëlle Uzu; Andrés Alástuey; Marcos Andrade; Valeria Mardóñez; Alkuin Maximilian Koenig; Diego Aliaga; Claudia Mohr
Abstract. The chemical composition of PM10 and PM2.5 was studied at the summit of Mt. Chacaltaya (5380 masl, lat.-16.346950º, lon. -68.128250º) providing a unique long-term record spanning from December 2011 to March 2020. The chemical composition of aerosol at the Chacaltaya GAW site is representative of the regional background, seasonally affected by biomass burning practices and by nearby anthropogenic emissions from the metropolitan area of La Paz – El Alto. Concentration levels are clearly influenced by seasons with minimum occurring during the wet season (December to March) and maxima occurring during the dry and transition seasons (April to November). Ions, total carbon (EC+OC) and saccharide concentrations range between 558–1785, 384–1120 and 4.3–25.5 ng m-3 for bulk PM10 and 917–2308, 519–1175 and 3.9–24.1 ng m-3 for PM2.5, respectively. Such concentrations are overall lower compared to other high-altitude stations around the globe, but higher than Amazonian remote sites (except for OC). For PM10, there is dominance of insoluble mineral matter (33–56 % of the mass), organic matter (7–34 %) and secondary inorganic aerosol (15–26 %). Chemical composition profiles were identified for different origins: EC, NO3-, NH4+, glucose, C2O4-2 for the nearby urban and rural areas; OC, EC, NO3-, K+, acetate, formiate, levoglucosan, some F- and Br- for biomass burning; MeSO3-, Na+, Mg2+, Br- for aged marine emissions from the Pacific Ocean; arabitol, mannitol, K+ for biogenic emissions; Na+, Ca2+, Mg2+ for soil dust, and SO42-, F-, and some Cl- for volcanism. Regional biomass-burning practices influence the soluble fraction of the aerosol particularly between July and September. The organic fraction is present all year round and has both anthropogenic (biomass burning and other combustion sources) and natural (primary and secondary biogenic emissions) origins, with the OC/EC mass ratio being practically constant all year round (10.5±38.9). Peruvian volcanism dominates the SO42- concentration since 2014, though it presents a strong temporal variability due to the intermittence of the sources and seasonal changes on the transport patterns. These measurements represent some of the first long-term observations of aerosol chemical composition at a continental high-altitude site in the tropical Southern hemisphere.
Deforestation Impacts on Amazon-Andes Hydroclimatic Connectivity
(2021) Juan Pablo Sierra; Clémentine Junquas; Jhan Carlo Espinoza; Hans Segura; Thomas Condom; Marcos Andrade; Jorge Molina‐Carpio; Laura Ticona; Valeria Mardóñez; Luis Blacutt
<title>Abstract</title> Amazonian deforestation has accelerated during the last decade, threatening an ecosystem where almost one third of the regional rainfall is transpired by the local rainforest. Due to the precipitation recycling, the southwestern Amazon, including the Amazon-Andes transition region, is particularly sensitive to forest loss. This study evaluates the impacts of Amazonian deforestation in the hydro-climatic connectivity between the Amazon and the eastern tropical Andes during the austral summer (December-January-February) in terms of hydrological and energetic balances. Using 10-year high-resolution simulations (2001–2011) with the Weather Research and Forecasting Model, we analyze control and deforestation scenario simulations. Regionally, deforestation leads to a reduction in the surface net radiation, evaporation, moisture convergence and precipitation (~ 20%) over the entire Amazon basin. In addition, during this season, deforestation increases the atmospheric subsidence over the southern Amazon and weakens the regional Hadley cell. Atmospheric stability increases over the western Amazon and the tropical Andes inhibiting convection in these areas. Consequently, major deforestation impacts are observed over the hydro-climate of the Amazon-Andes transition region. At local scale, nighttime precipitation decreases in Bolivian valleys (~ 20–30%) due to a strong reduction in the humidity transport from the Amazon plains toward Andes linked to the South American low-level jet. Over these valleys, a weakening of the daytime upslope winds is caused by local deforestation, which reduces the turbulent fluxes at lowlands. These alterations in rainfall and atmospheric circulation could impact the rich Andean ecosystems and its tropical glaciers.
Deforestation impacts on Amazon-Andes hydroclimatic connectivity
(2021) Juan Pablo Sierra; Jhan Carlo Espinoza; Clémentine Junquas; Jan Polcher‬; Miguel Saavedra; Jorge Molina‐Carpio; Marcos Andrade; Thomas Condom; Laura Ticona
&lt;p&gt;The Amazon rainforest is a key component of the climate system and one of the main planetary evapotranspiration sources. Over the entire Amazon basin, strong land-atmosphere feedbacks cause almost one third of the regional rainfall to be transpired by the local rainforest. Maximum precipitation recycling ratio takes place on the southwestern edge of the Amazon basin (a.k.a. Amazon-Andes transition region), an area recognized as the rainiest and biologically richest of the whole watershed. Here, high precipitation rates lead to large values of runoff per unit area providing most of the sediment load to Amazon rivers. As a consequence, the transition region can potentially be very sensitive to Amazonian forest loss. In fact, recent acceleration in deforestation rates has been reported over tropical South America. These sustained land-cover changes can alter the regional water and energy balances, as well as the regional circulation and rainfall patterns. In this sense, the use of regional climate models can help to understand the possible impacts of deforestation on the Amazon-Andes zone.&lt;/p&gt;&lt;p&gt;This work aims to assess the projected Amazonian deforestation effects on the moisture transport and rainfall behavior over tropical South America and the Amazon-Andes transition region. We perform 10-year austral summer simulations with the Weather Research and Forecasting model (WRF) using 3 one-way nested domains. Our finest domain is located over the south-western part of the basin, comprising two instrumented Andean Valleys (Zongo and Coroico river Valleys). Convective permitting high horizontal resolution (1km) is used over this domain. The outcomes presented here enhance the understanding of biosphere-atmosphere coupling and its deforestation induced disturbances.&lt;/p&gt;
Deforestation impacts on Amazon-Andes hydroclimatic connectivity
(Springer Science+Business Media, 2021) Juan Pablo Sierra; Clémentine Junquas; Jhan Carlo Espinoza; Hans Segura; Thomas Condom; Marcos Andrade; Jorge Molina‐Carpio; Laura Ticona; Valeria Mardóñez; Luis Blacutt