Research Line:

Water and extremes

This research line studies extreme hydrometeorological events and their impact on society and ecosystems, both natural and non-natural, analyzing the roles played by natural variability and anthropogenic climate change.

For the 2024-2025 period, the line aims to deepen the characterization of extreme events and their socio-environmental impacts, especially heat waves, mega-fires, and hyper-droughts, by evaluating their natural and anthropogenic drivers, projecting their future occurrence and formally attributing human-induced climate change to such impacts.

Simultaneously, it proposes to determine how climate change, natural climate variability, and increasing water demand affect water security in central-southern Chile. Additionally, it seeks to evaluate the ranges of hydrological memory, the main hydroclimatic characteristics and processes that control it, and how the propagation of extreme precipitation events is modulated under warmer climatic conditions.

Work is also being done to characterize the dynamics and interconnections of crucial aspects that determine the regional hydroclimate in Chile, which currently present signals of climate change alteration, such as the strengthening of the South Pacific Anticyclone, the strengthening and southward migration of the westerly winds, patterns of atmospheric blocking in the Southern Ocean and Antarctica, and the temporal stability between El Niño-Southern Oscillation (ENSO) and the precipitation regime in central Chile.

Review the research achievements of this line in our institutional report.

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Título	Autores	Línea de Investigación	Año	DOI	Abstract	Revista	ISSN	Acceso	Páginas	Volumen	Index	Key Words
Using the Weather Research and Forecasting (WRF) Model for Precipitation Forecasting in an Andean Region with Complex Topography	Yáñez-Morroni, Gonzalo; Gironás, Jorge; Caneo, Marta; Delgado, Rodrigo; Garreaud, René	Agua y Extremos	2018.0	10.3390/atmos9080304	The Weather Research and Forecasting (WRF) model has been successfully used in weather prediction, but its ability to simulate precipitation over areas with complex topography is not optimal. Consequently, WRF has problems forecasting rainfall events over Chilean mountainous terrain and foothills, where some of the main cities are located, and where intense rainfall occurs due to cutoff lows. This work analyzes an ensemble of microphysics schemes to enhance initial forecasts made by the Chilean Weather Agency in the front range of Santiago. We first tested different vertical levels resolution, land use and land surface models, as well as meteorological forcing (GFS/FNL). The final ensemble configuration considered three microphysics schemes and lead times over three rainfall events between 2015 and 2017. Cutoff low complex meteorological characteristics impede the temporal simulation of rainfall properties. With three days of lead time, WRF properly forecasts the rainiest N-hours and temperatures during the event, although more accuracy is obtained when the rainfall is caused by a meteorological frontal system. Finally, the WSM6 microphysics option had the best performance, although further analysis using other storms and locations in the area are needed to strengthen this result.	Atmosphere	2073-4433	http://www.mdpi.com/2073-4433/9/8/304	304	9	Thomson Reuters ISI	land use, rain, topography, complex topographies, flash flood, land surface models, meteorological forcing, mountainous terrain, precipitation forecasting, temporal simulation, weather research and forecasting models, weather forecasting, atmospheric modeling, computer simulation, ensemble forecasting, precipitation (climatology), regional climate, temporal analysis, topography, urban atmosphere, weather forecasting
Development and resilience of deciduous Nothofagus forests since the Last Glacial Termination and deglaciation of the central Patagonian Andes	Villa-Martínez, Rodrigo; Moreno, Patricio I.	Agua y Extremos	2021.0	10.1016/j.palaeo.2021.110459	Resolving the history of vegetation, fire, and glaciation on the eastern slope of the central Patagonian Andes (44°-49°S) since the Last Glacial Termination (T1) has proved difficult. This is due to the steep environmental gradients, vegetation heterogeneity, and scarcity of dated glacial deposits and geomorphic features. Unsurprisingly, published records show important heterogeneities which limit our understanding of the timing and magnitude of climate and vegetation changes, and their driving mechanisms since T1. In this paper, we describe sediment cores from small closed-basin lakes located in the deciduous Nothofagus forest zone near Coyhaique, Chile. Our results indicate that the Coyhaique glacier lobe abandoned its final Last Glacial Maximum position just before ~17.9 cal kyr BP and underwent a step-wise recession that included a halt/readvance that culminated at ~16.8 cal kyr BP, contemporaneous with the formation of an ice-dammed proglacial lake in the Coyhaique/Balmaceda sector. This glacial lake stood at its highest level between ~17.9–17.2 cal kyr BP (<726 and > 650 m.a.s.l.), lowered between ~17.2–16.2 cal kyr BP (<650 and > 570 m.a.s.l.), and disappeared thereafter. Herbs and shrubs, currently dominant in high Andean and Patagonian steppe environments, colonized the ice-free terrains distal to the glacier margins and proglacial lakes under cold and dry conditions. This was followed by a steady increase in Nothofagus between ~16.6–14.8 cal kyr BP that led to the establishment of forests starting at ~14.8 cal kyr BP. The Holocene started with a sudden increase in Nothofagus and disappearance of conifers in the context of increase fire activity between ~11.7–9.4 cal kyr BP. Closed-canopy Nothofagus forests persisted virtually unaltered from ~9.4 cal kyr BP to the present day, despite frequent explosive volcanism and millennial-scale variations in fire regimes, attesting to their extraordinary postglacial resilience which contrasts with their behavior during T1. Recent large-scale deforestation by fire, livestock grazing, and the spread of non-native invasive plant species drove the fastest and largest-magnitude shifts seen during the last ~16,500 years.	Palaeogeography, Palaeoclimatology, Palaeoecology	00310182	https://linkinghub.elsevier.com/retrieve/pii/S0031018221002443	110459	574.0	Thomson Reuters ISI	deciduous forest, deglaciation, ecosystem resilience, forest canopy, glacial lake, holocene, last glacial maximum, proglacial environment, sediment core, andes, coihaique, patagonia, coniferophyta, nothofagus
The last glacial termination in the Coyhaique sector of central Patagonia	Vilanova, I.; Moreno, P.I.; Miranda, C.G.; Villa-Martínez, R.P.	Agua y Extremos	2019.0	10.1016/j.quascirev.2019.105976		Quaternary Science Reviews	0277-3791	https://linkinghub.elsevier.com/retrieve/pii/S0277379119306572	105976	224.0	Thomson Reuters ISI	glacial geology, lakes, reforestation, vegetation, biological productivity, continental landmass, deep water convection, glacial terminations, last glacial maximum, last glacial terminations, southern south america, southern westerly winds, climate change, climate change, glacial-interglacial cycle, global climate, ice-dammed lake, last glacial, last glacial maximum, precipitation (climatology), proglacial environment, treeline, upwelling, westerly, aisen, andes, chile, coihaique, patagonia, southern ocean
The Chilean Tornado Outbreak of May 2019: Synoptic, mesoscale, and historical contexts	Vicencio, José; Rondanelli, Roberto; Campos, Diego; Valenzuela, Raúl; Garreaud, René; Reyes, Alejandra; Padilla, Rodrigo; Abarca, Ricardo; Barahona, Camilo; Delgado, Rodrigo; Nicora, Gabriela	Zonas Costeras; Agua y Extremos	2020.0	10.1175/BAMS-D-19-0218.1	Capsule An unprecedented tornado outbreak occurred in Southern Chile, with at least seven tornadoes reported over a period of 24 hours, causing substantial damage, dozens of injuries, and one fatality.	Bulletin of the American Meteorological Society	0003-0007, 1520-0477	https://journals.ametsoc.org/view/journals/bams/aop/BAMS-D-19-0218.1/BAMS-D-19-0218.1.xml	1-52		Thomson Reuters ISI	potential energy, storms, anecdotal evidences, convective available potential energies, lightning datum, low-level winds, mid-latitude storms, tornado outbreak, vorticity generation, western south america, tornadoes
Impacts of Atmospheric Rivers on Precipitation in Southern South America	Viale, Maximiliano; Valenzuela, Raúl; Garreaud, René D.; Ralph, F. Martin	Agua y Extremos	2018.0	10.1175/JHM-D-18-0006.1	This study quantifies the impact of atmospheric rivers (ARs) on precipitation in southern South America. An AR detection algorithm was developed based on integrated water vapor transport (IVT) from 6-hourly CFSR reanalysis data over a 16-yr period (2001-16). AR landfalls were linked to precipitation using a comprehensive observing network that spanned large variations in terrain along and across the Andes from 27° to 55°S, including some sites with hourly data. Along the Pacific (west) coast, AR landfalls are most frequent between 38° and 50°S, averaging 35-40 days yr-1. This decreases rapidly to the south and north of this maximum, as well as to the east of the Andes. Landfalling ARs are more frequent in winter/spring (summer/fall) to the north (south) of ~43°S. ARs contribute 45%-60% of the annual precipitation in subtropical Chile (37°-32°S) and 40%-55% along the midlatitude west coast (37°-47°S). These values significantly exceed those in western North America, likely due to the Andes being taller. In subtropical and midlatitude regions, roughly half of all events with top-quartile precipitation rates occur under AR conditions. Median daily and hourly precipitation in ARs is 2-3 times that of other storms. The results of this study extend knowledge of the key roles of ARs on precipitation, weather, and climate in the South American region. They enable comparisons with other areas globally, provide context for specific events, and support local nowcasting and forecasting. © 2018 American Meteorological Society.	Journal of Hydrometeorology	1525-755X	http://journals.ametsoc.org/doi/10.1175/JHM-D-18-0006.1	1671-1687	19	Thomson Reuters ISI	atmospheric transport, extratropical cyclone, precipitation (climatology), regional climate, topographic effect, water vapor, pacific ocean, pacific ocean (south), south america
Geo-climatic hazards in the eastern subtropical Andes: distribution, climate drivers and trends	Vergara, Iván; Moreiras, Stella M.; Araneo, Diego; Garreaud, René	Agua y Extremos	2020.0	10.5194/nhess-20-1353-2020	Abstract. Detecting and understanding historical changes in the frequency of geo-climatic hazards (G-CHs) is crucial for the quantification of current hazards and project them into the future. Here we focus in the eastern subtropical Andes (32–33∘ S), using meteorological data and a century-long inventory of 553 G-CHs triggered by rainfall or snowfall. We first analyse their spatio-temporal distributions and the role of climate variability in the year-to-year changes in the number of days per season with G-CHs. Precipitation is positively correlated with the number of G-CHs across the region and year-round; mean temperature is negatively correlated with snowfall-driven hazards in the western (higher) half of the study region during winter and with rainfall-driven hazards in the eastern zone during summer. The trends of the G-CH frequency since the mid-20th century were calculated, paying attention to their non-systematic monitoring. The G-CH series for the different triggers, zones and seasons were generally stationary. Nonetheless, there is a small positive trend in rainfall-driven G-CHs in the eastern zone during summer, congruent with a rainfall increase there. We also found a decrease in snowfall-driven G-CHs in the western zone from the late 1990s onwards, most likely due to a reduction in winter precipitation rather than to an increase in temperature.	Natural Hazards and Earth System Sciences	1684-9981	https://www.nat-hazards-earth-syst-sci.net/20/1353/2020/	1353-1367	20.0	Thomson Reuters ISI	climate conditions, detection method, precipitation intensity, seasonal variation, snow, spatiotemporal analysis, subtropical region, trend analysis, andes
Environmental costs of water transfers	Vargas, Cristian A.; Garreaud, Rene; Barra, Ricardo; Vásquez-Lavin, Felipe; Saldías, Gonzalo S.; Parra, Oscar	Agua y Extremos	2020.0	10.1038/s41893-020-0526-5		Nature Sustainability	2398-9629	http://www.nature.com/articles/s41893-020-0526-5			Thomson Reuters ISI
Extreme Daily Rainfall in Central-Southern Chile and Its Relationship with Low-Level Horizontal Water Vapor Fluxes	Valenzuela, Raúl A.; Garreaud, René D.	Agua y Extremos	2019.0	10.1175/JHM-D-19-0036.1	Extreme rainfall events are thought to be one of the major threats of climate change given an increase of water vapor available in the atmosphere. However, before projecting future changes in extreme rainfall events, it is mandatory to know current patterns. In this study we explore extreme daily rainfall events along central-southern Chile with emphasis in their spatial distribution and concurrent synoptic-scale circulation. Surface rain gauges and reanalysis products from the Climate Forecast System Reanalysis are employed to unravel the dependency between extreme rainfall and horizontal water vapor fluxes. Results indicate that extreme rainfall events can occur everywhere, from the subtropical to extratropical latitudes, but their frequency increases where terrain has higher altitude, especially over the Andes Mountains. The majority of these events concentrate in austral winter, last a single day, and encompass a north–south band of about 200 km in length. Composited synoptic analyses identified extreme rainfall cases dominated by northwesterly (NW) and westerly (W) moisture fluxes. Some features of the NW group include a 300-hPa trough projecting from the extratropics to subtropics, a surface-level depression, and cyclonic winds at 850 hPa along the coast associated with integrated water vapor (IWV) > 30 mm. Conversely, features in the W group include both a very weak 300-hPa trough and surface depression, as well as coastal westerly winds associated with IWV > 30 mm. About half of extreme daily rainfall is associated with an atmospheric river. Extreme rainfall observed in W (NW) cases has a strong orographic (synoptic) forcing. In addition, W cases are, on average, warmer than NW cases, leading to an amplified hydrological response.	Journal of Hydrometeorology	1525-755X	http://journals.ametsoc.org/doi/10.1175/JHM-D-19-0036.1	1829-1850	20.0	Thomson Reuters ISI	diurnal variation, extreme event, precipitation assessment, precipitation intensity, raingauge, spatiotemporal analysis, water flux, water vapor, chile
Terrain-Trapped Airflows and Orographic Rainfall along the Coast of Northern California. Part II: Horizontal and Vertical Structures Observed by a Scanning Doppler Radar	Valenzuela, Raul A.; Kingsmill, David E.	Agua y Extremos	2018.0	10.1175/MWR-D-17-0227.1	This study documents the mean properties and variability of kinematic and precipitation structures associated with orographic precipitation along the coast of Northern California in the context of terrain-trapped airflows (TTAs). TTAs are defined as relatively narrow air masses that consistently flow in close proximity and approximately parallel to an orographic barrier. Seven land-falling winter storms are examined with observations from a scanning X-band Doppler radar deployed on the coast at Fort Ross, California. Additional information is provided by a 915-MHz wind-profiling radar, surface meteorology, a GPS receiver, and balloon soundings. The composite kinematic structure during TTA conditions exhibits a significant horizontal gradient of wind direction from the coast to approximately 50 km offshore and a low-level jet (LLJ) that surmounts a weaker airflow offshore corresponding to the TTA, with a zone of enhanced precipitation evident between ~5 and 25 km offshore and oriented nearly parallel to the coastline. Conversely, the composite kinematic structure during NO-TTA conditions exhibits a smaller offshore horizontal gradient of wind direction and precipitation structures are generally enhanced within ~15 km of the coastline. Interstorm variability analysis reveals significant variations in kinematic structures during both TTA and NO-TTA conditions, whereas significant variations in precipitation structures are only evident during TTA conditions. The interstorm analysis also illustrates more clearly how LLJ vertical structures evident during NO-TTA conditions exhibit ascent along the coast and over the coastal mountains, which is in contrast to TTA conditions where the ascent occurs offshore and over the TTA.	Monthly Weather Review	0027-0644	http://journals.ametsoc.org/doi/10.1175/MWR-D-17-0227.1	2381-2402	146	Thomson Reuters ISI	atmospheric movements, channel flow, doppler radar, global positioning system, kinematics, landforms, precipitation (chemical), storms, coastal meteorologies, horizontal gradients, kinematic structures, orographic effects, orographic precipitation, orographic rainfalls, precipitation structure, radars/radar observations, precipitation (meteorology), airflow, channel flow, coastal zone, doppler radar, hydrometeorology, orographic effect, precipitation assessment, rainfall, terrain, wind direction, california, united states
Climate variability and forest fires in central and south-central Chile	Urrutia-Jalabert, Rocío; González, Mauro E.; González-Reyes, Álvaro; Lara, Antonio; Garreaud, René	Cambio de Uso de Suelo; Agua y Extremos	2018.0	10.1002/ecs2.2171	This paper evaluates the relationship between fire occurrence (number and burned area) and climate variability (precipitation and maximum temperatures) across central and south-central Chile (32°–43° S) during recent decades (1976–2013). This region sustains the largest proportion of the Chilean population, contains ecologically important remnants of endemic ecosystems, the largest extension of forest exotic plantations, and concentrates most of the fire activity in the country. Fire activity in central Chile was mainly associated with above-average precipitation during winter of the previous year and with dry conditions during spring to summer. The later association was particularly strong in the southern, wetter part of the study region. Maximum temperature had a positive significant relationship with burned area across the study region, with stronger correlations toward the south. Fires in central Chile were significantly related to El Nino~ –Southern Oscillation, through rainfall anomalies during the year previous to the fire season. The Antarctic Oscillation during winter through summer was positively related to fires across the study area due to drier/warmer conditions associated with the positive polarity of this oscillation. Climate change projections for the region reveal an all-season decrease in precipitation and increases in temperature, that may likely result in an increment of the occurrence and the area affected by fires, as it has been observed during a multi-year drought afflicting central Chile since 2010.	Ecosphere	2150-8925	http://doi.wiley.com/10.1002/ecs2.2171	e02171	9	Thomson Reuters ISI	antarctic oscillation, climate change, el niño–southern oscillation (enso), exotic plantations, forest fires, mediterranean forests, temperate forests

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