Juan F. Salazar

University of Antioquia | UdeA · Escuela Ambiental

Increasing climatic and human pressures are changing the world's water resources and hydrological processes at unprecedented rates. Understanding these changes requires comprehensive monitoring of water resources. Hydrogeodesy, the science that measures the Earth's solid and aquatic surfaces, gravity field, and their changes over time, delivers a r...

Transboundary assessments of water security typically adopt an ‘upstream’ perspective, focusing on hazards and vulnerabilities occurring within a given hydrological basin. However, as the moisture that provides precipitation in the hydrological basin probably originates ‘upwind’, hazards and vulnerabilities potentially altering the moisture supply...

Global change is altering hydrologic regimes worldwide, including large basins that play a central role in the sustainability of human societies and ecosystems. The basin water budget is a fundamental framework for understanding these basins' sensitivity and future dynamics under changing forcings. In this budget, studies often treat atmospheric pr...

Study region: Tropical watershed in the Colombian Andes, the Chico River (CR) watershed. Study focus: Hydrological models are widely used to project the impacts of LULC (Land Use/Land Cover) change on water budget. However, their ability to produce reliable predictions depends on how accurately they represent the role of vegetation in the watershed...

The forest–savanna transition is the most widespread ecotone in the tropics, with important ecological, climatic, and biogeochemical implications at local to global scales. However, the factors and mechanisms that control this transition vary among continents and regions. Here, we analyzed which factors best explain the transition in northern South...

Global change is altering hydrologic regimes worldwide, including large basins that play a central role in the sustainability of human societies and ecosystems. The basin water budget is a fundamental framework for understanding these basins' sensitivity and future dynamics under changing forcings. In this budget, studies often treat atmospheric pr...

Plain Language Summary El Niño is recognized as a climate variability phenomenon with significant impacts on precipitation worldwide. However, the mechanisms behind these impacts are not fully understood. Here we use model simulations to argue that one of those mechanisms is the effect of El Niño on terrestrial moisture recycling (TMR), that is, th...

Gridded precipitation products (GPPs) represent an alternative to and a complement to gauge-based observations of precipitation, improving the representation of spatio-temporal precipitation variability in regions with scarce gauge networks. However, GPPs' accuracy varies among products, temporal resolution, and regions, indicating the need for par...

Las Comunicaciones Nacionales sobre Cambio Climático (CNCC) son un mecanismo para que los países informen sus avances en mitigación y adaptación, y constituyen uno de los elementos de base para la política sobre cambio climático a escala nacional. Colombia ha emitido tres CNCC. La tercera plantea un escenario que considera las proyecciones de diver...

Precipitation is a key hydrological variable for understanding streamflow response in a river basin, thus its suitable spatio-temporal representation is crucial for modeling multiple hydrological processes. Generally, precipitation inputs used in hydrological modeling come from gauge-based observations. However, these measurements, which are only r...

In democracies around the world, societies have demonstrated that elections can have major consequences for the environment. In Colombia, the 2022 presidential elections will take place at a time when progress towards peace has stalled and socioeconomic, security, and environmental conditions have deteriorated. The recent declines in these conditio...

Forests are under pressure globally. How deforestation affects river flow is essential for water security in many regions. Here we conduct a meta-analysis of studies investigating this question in large basins of South America and show that different modeling approaches lead to opposite conclusions about deforestation effects on river flow. A widel...

The evaluation of remote precipitation estimates (RPE) performance is key before any use in hydrological or climatic applications. In this study, we evaluated the performance of 7 RPE products (TRMM, CHIRPSv2, CMORPH, PERSIANN-CDR, PERSIAN-CCS, ERA5, and MSWEPv2.6) over Colombian Orinoquía and Amazonía regions for the period 2004-2015. Continuous (...

Governments' responses to the COVID-19 pandemic provide a unique opportunity to study the effects of restricted socioeconomic activity on air quality. Here, we study the changes in air pollution levels during the lockdown in Medellín and its metropolitan area, Colombia, for periods with and without enhanced regional fire activity, considering the e...

Some of the main problems in hydrological sciences are related to how and why river flows change as a result of environmental change, and what are the corresponding implications for society. This has been described as the Panta Rhei context, which refers to the challenge of understanding and quantifying hydrological dynamics in a changing environme...

The savanna - forest transition in the tropics has a large and complex variation in vegetation structure both vertically and horizontally. 3D-imaging technologies provide detailed high-resolution measurements of the vegetation structure. However, the use of these observations globally faces practical challenges due to spatio-temporal gaps and opera...

Vegetation dynamics are key to understanding and simulating water balance in hydrological models. The Soil and Water Assessment Tool (SWAT) model represents these dynamics through a plant growth module that was originally developed based on temperate regions. Alemayehu et al. (2017) developed SWAT-T, a SWAT variant that is better suited for represe...

Dynamics of terrestrial water storage are determinant for many natural and social phenomena, with implications for water security and environmental sustainability. Here we use 2002–2017 data from the Gravity Recovery and Climate Experiment (GRACE) to study these dynamics in the Magdalena-Cauca river basin in northwestern South America. Through comp...

Transport of air pollutants emitted from urban valleys can be strongly restricted by interactions between static and dynamic factors including topographic forcing, low-level atmospheric stability related to temperature inversions, and urban heat island-induced circulations. Interplay between these processes has a complex and dynamic nature, and is...

The number of studies on urban cooling strategies has been continuously growing. A common premise is that urban heat island (UHI) mitigation has a net beneficial effect on urban environmental quality and sustainability. Here we evaluate how UHI mitigation affects air quality in an idealized urban valley by means of large-eddy simulations. A passive...

Air quality planning and management can benefit from the ability of numerical models to produce skillful forecasts. However, obtaining these forecasts is a continuing challenge, particularly in complex terrain. Here we examine the dispersion of traffic emissions in the Aburrá valley (located in the Colombian Andes) during an episode of severe air p...

Some large-scale components of the Earth's climate system have been identified as policy-relevant “tipping elements”, meaning that anthropogenic forcing and perturbations may push them across a tipping point threshold, with potential global scale impact on ecosystems and concomitant environmental and social phenomena. A pronounced change in the amp...

Some large-scale components of the Earth's climate system have been identified as policy-relevant tipping elements, meaning that anthropogenic forcing and perturbations may push them across a tipping point threshold, with potential global scale impact on ecosystems and concomitant environmental and social phenomena. A pronounced change in the ampli...

The Amazon forests and climatological precipitation patterns in South America are interrelated. A fundamental question is how these patterns depend on the presence of forests. Here we investigate this relationship by studying how precipitation varies with distance from the ocean along wind streamlines linking the Atlantic Ocean to northwestern and...

Precipitation in the tropical Andes is strongly influenced by the ENSO phases and orographic effects. In particular, precipitation can be drastically reduced during El Niño. Decision-making about water resources relies on modelling precipitation as the main source for water availability. Here we evaluate ERA-Interim´s capacity to represent precipit...

For decades, scientists have debated the relation between physical attributes and vegetation and the partitioning of rainfall (P) into evaporation (E) and runoff (R) in basins. Physical and ecological processes explain the long‐term behavior of E via water or energy limitations. Needed are similar globally‐applicable frameworks for describing the p...

Some of the main environmental impacts of cities occur through the Urban Heat Island (UHI) phenomenon. Importantly, the UHI can exert strong effects on wind dynamics and, therefore, on the transport of air pollutants emitted from urban areas. This transport is critical for air quality, especially when cities are located in complex terrains where or...

Colombia, one of the world’s most species- rich nations, is currently undergoing a profound social transition: the end of a decades- long conflict with the Revolutionary Armed Forces of Colombia, known as FARC. The peace agreement process will likely trans-form the country’s physical and socioeconomic landscapes at a time when humans are altering E...

Climate models are essential tools for predicting climate change impacts. In Colombia, it is key that these models predict the hydrological effects associated with El Niño. In this study, we conducted a quantitative evaluation of the performance of CMIP3 and CMIP3 models to represent the occurrence of El Niño and its effects on Colombian hydrology....

The ability to predict streamflow regimes is fundamental for decision-making in water resources planning. In this study, the capacity of semi-distributed SWAT model (Soil and Water Assessment Tool) was evaluated to predict mean and extreme streamflows in the Chico river Andean watershed. SWAT-CUP program and daily streamflow data for 1990-2004 and...

Extreme flows are key components of river flow regimes that affect manifold hydrological, geomorphological and ecological processes with societal relevance. One fundamental characteristic of extreme flows in river basins is that they exhibit scaling properties which can be identified through scaling (power) laws. Understanding the physical mechanis...

Groundwater is becoming increasingly important as a strategic water resource in many regions of the world, and particularly in Colombia where some regions are already facing surface water scarcity and drought-related problems. Global change-related decreases of terrestrial water storages can have strong effects on the sustainability of groundwater...

Many natural and social phenomena depend on river flow regimes that are being altered by global change. Understanding the mechanisms behind such alterations is crucial for predicting river flow regimes in a changing environment. Here we introduce a novel physical interpretation of the scaling properties of river flows and show that it leads to a pa...

Global changes in forest cover have been related to major scientific and social challenges. There are important uncertainties about the potential effects of ongoing forest loss on continental water balances. Here we present an observation-based analysis of long-term water balance partitioning (precipitation divided into evaporation and runoff) in 2...

As a result of the combination of limited ventilation and high emission of pollutants, urban valleys may experience serious air pollution problems. Ventilation can be limited not only by orographic barriers, but also by the capping effect associated with a low level temperature inversion. Temperature inversion can strongly affect the air quality of...

* Precipitation in the complex terrain of the tropical Andes of South America can be strongly reduced during El Niño events, with impacts on numerous societally-relevant services. * Simulating precipitation patterns and behavior in such areas of complex terrain has remained a challenge for regional climate models. * Current data products such as ER...

In last decades, there has been increasing debate about the hydrological and meteorological role of forests, particularly regarding its role in the regulation of the energy and water balances. Here we summarize results from an ongoing research program studying this problem. First, we introduce the notion of ecohydrological scaling to show the exist...

Ecosystem dynamics are a fundamental driver of the water cycle, with their influence operating on multiple spatial and temporal scales1, 2, 3. For decades, hydrologists and environmental scientists have debated the influence of forests in the water cycle4, 5, 6 and particularly their effect in the regulation of rainfall-runoff dynamics that result...

The vegetation plays an important role in the hydrological cycle of region (Seller, 1997). The scientific discussion about the magnitude of the effects of a forest in the water cycle is still unresolved (Andreassian, 2004; Troch et al., 2013), because this influence interferes in multiple spatial and temporal scales (Bonan, 2008; Seller, 1997; Spra...

A simple model of temperature inversion breakup in mountain valleys is developed. This model is an exten-sion of the conceptual model of D. Whiteman (1981), and its main features are: (1) The topography is repre-sented by a digital elevation model, thus leading to a spatially-distributed model. (2) A simplified, yet rea-listic, representation of th...

Urban valleys can experience serious air pollution problems as a combined result of their limited ventilation and the high emission of pollutants from the urban areas. Idealized simulations were analysed in order to elucidate the breakup of an inversion layer in urban valleys subject to a strong low-level temperature inversion and topographic effec...

Land cover changes associated with both human activities and global change processes (such as drought, fire and invasive species) can lead to changes in biophysical processes that support hydrological processes in watersheds, leading to potential changes in longterm streamflow regimes. Traditional hydrological approaches have successfully associate...

In this paper we discuss and illustrate the hypothesis that life substantially alters the state of a planetary environment and therefore, modifies the limits of the HZ as estimated for an uninhabited planet. This hypothesis lead to the introduction of the Habitable Zone for Inhabited planets (hereafter InHZ), defined here as the region where the co...

In this paper we discuss and illustrate the hypothesis that life substantially alters the state of a planetary environment and therefore, modifies the limits of the HZ as estimated for an uninhabited planet. This hypothesis lead to the introduction of the Habitable Zone for Inhabited planets (hereafter InHZ), defined here as the region where the co...

Many cities located in valleys with limited ventilation experience serious air pollution problems. The ventilation of an urban valley can be limited not only by orographic barriers, but also by urban heat island–induced circulations and/or the capping effect of temperature inversions. Furthermore, land-use/-cover changes caused by urbanization alte...

Many cities located in valleys with limited ventilation experience serious air pollution problems. The ventilation of an urban valley can be limited not only by orographic barriers, but also by urban heat island–induced circulations and/or the capping effect of temperature inversions. Furthermore, land-use/-cover changes caused by urbanization alte...

In this paper we discuss and illustrate the hypothesis that life substantially alters the state of a planetary environment and therefore, modifies the limits of the HZ as estimated for an uninhabited planet. This hypothesis lead to the introduction of the Habitable Zone for Inhabited planets (hereafter InHZ), defined here as the region where the co...

Urban valleys can experience serious air pollution problems of concern for public health. The venting of pollution out of an urban valley is limited by the topography and can be further restricted by low-level temperature inversions and/or local circulations such as those induced by the Urban Heat Island (UHI) effect. The combined effects of a temp...

The role of a simplified hydrological cycle and a physical representation of clouds is investigated in the Daisyworld model, subject to constant and variable solar forcing and varying cloud albedo and height. Under constant forcing, properties of the cloudy hydrologic cycle control the long-term system dynamics to non-oscillatory, oscillatory, abio...

The role of a simplified hydrological cycle and a physical representation of clouds is investigated in the Daisyworld model, subject to constant and variable solar forcing and varying cloud albedo and height. Under constant forcing, properties of the cloudy hydrologic cycle control the long-term system dynamics to non-oscillatory, oscillatory, abio...

El clima de la Tierra es un sistema dinámico no lineal que opera a través de ciclos complejos de retroalimentación, y que funciona como un sistema único, autorregulado, compuesto por elementos físicos, químicos, biológicos y antrópicos. La teoría de Gaia ha propuesto la existencia de una retroalimetación de doble vía entre el clima y la biota de la...