Cristian Mattar

University of Chile · Laboratorio para el Análisis de la Biósfera (LAB)

Una escasez hídrica ha estado afectando a Chile en los últimos años. Debido a los efectos negativos que puede generar el déficit de agua en el medio ambiente y en la población, es necesario mejorar nuestro entendimiento sobre la influencia de los factores climáticos y antropogénicos en la reducción hídrica, especialmente en regiones áridas como el...

The Chilean Western Patagonia has the highest wind potential resources in South America. Its complex terrain deserves a special attention for wind modeling and assessments. In this work, we have performed a comprehensive meso-scale climate simulation on Weather Research and Forecasting (WRF) in order to provide new insights into the wind climatolog...

El recurso global asociado a energía undimotriz (wave) y energía mareomotriz (tidal stream), ha sido estimado en 32000 TWh/yr y 640 TWh/yr, respectivamente, que podría satisfacer el consumo mundial de electricidad de 21372 TWh/yr (IEA, 2017). En el año 2016 el Banco Mundial reportó que 889,7 millones de personas no tienen acceso a la electricidad,...

This research evaluates the impact of information sources on the feasibility of a Hybrid Renewable Energy System (HRES). Due to their isolation and low population density, island communities satisfy their demand for electricity through thermoelectric plants. Diesel is the main fossil fuel used. This fuel must be imported, which translates into high...

Snow cover area is dramatically decreasing across the Los Andes Mountains and the most relevant water reservoir under drought conditions. In this sense, monitoring of snow cover is key to analyzing the hydrologic balance in snowmelt-driven basins. MODIS Snow Cover daily products (MOD10A1 and MYD10A1) allow snow cover to be monitored at regular time...

The effects and consequences of global warming on the productivity of the Patagonian forest are still unknown. The use of Unmanned Aerial Vehicles (UAV) promotes new knowledge of the most pristine and unknown sub-antarctic forests located in Chilean Patagonia. This work presents an initial approach to spatialize biochemicals over the Patagonian for...

Evapotranspiration (ET) is key to assess crop water balance and optimize water-use efficiency. To attain sustainability in cropping systems, especially in semi-arid ecosystems, it is necessary to improve methodologies of ET estimation. A method to predict ET is by using land surface temperature (LST) from remote sensing data and applying the Operat...

Offshore wind energy continues to be a potential candidate for meeting the electricity consumption needs of the Chilean population for decades to come. However, the Chilean energy market is skeptical about exploiting offshore marine energy. At present, there are no offshore marine energy farms. This is probably attributable to the current legal fra...

The objective of this review is to present the characteristics and trends in hybrid renewable energy systems for remote off-grid communities. Traditionally, remote off-grid communities have used diesel oil-based system to generate electricity. Increased technological options and lower costs have resulted in the adoption of hybrid renewable energy-b...

Seasonal snow and glaciers in arid mountain regions are essential in sustaining human populations, economic activity, and ecosystems, especially in their role as reservoirs. However, they are threatened by global atmospheric changes, in particular by variations in air temperature and their effects on precipitation phase, snow dynamics, and mass bal...

Farmers in the temperate zone of southern Chile have started to irrigate historically rainfed pastures during recent years to reduce dairy productivity losses against increasingly severe summer droughts. The lack of information on pasture water requirements (i.e., evapotranspiration), however, hampers the implementation of efficient irrigation prog...

We present the characteristics and trends in hybrid renewable energy systems for remote off-grid communities. We evaluated 168 studies from the period 2002-2019 considered energy developments in Asia, northern Europe, Africa and South America, with the great majority in the northern hemisphere (n = 152, 90.5%). Many of the studied systems were loca...

One of the most important components of the earth's surface water balance is evapotranspiration, which regulates the exchange of energy between ground and atmosphere. The effects of global warming intensify the water demand and therefore, the potential scarcity of water could affect several landscapes and agricultural systems. Therefore, it is esse...

Antarctica is among the most important regions when it comes to observing the effects of climate change. One important part of the variability of the land surface temperature (LST) observed on this continent is related to the sea surface temperature of the Tropical Pacific Ocean, which is associated with El Niño-Southern Oscillation (ENSO). This la...

p>The estimation of the biophysical parameters of vegetation such as LAI (Leaf Area Index), FAPAR (Fraction of Absorbed Photosynthetically Active Radiation) and FCOVER (Fraction of Green Vegetation) have many climatic, hydrologic, ecosystem and silvo-agricultural applications. Despite the various satellite products that estimate these parameters co...

The forests in the Aysén region (ca. 43-49 °S, Chile) have a high degree of wilderness and cover more than 4.8 million hectares, making it one of the largest areas of subantarctic forest in the Southern Hemisphere. The impact of global warming on this region is poorly documented. The main objective of this work was to analyze the normalized differe...

The recent 2015–2016 El Niño (EN) event was considered as strong as the EN in 1997–1998. Given such magnitude, it was expected to result in extreme warming and moisture anomalies in tropical areas. Here we characterize the spatial patterns of temperature anomalies and drought over tropical forests, including tropical South America (Amazonia), Afric...

The evidence for global warming can be seen in various forms, such as glacier shrinkage, sea ice retreat, sea level rise and air temperature increases. The magnitude of these changes tends to be critical over pristine and extreme biomes. Chilean Patagonia is one of the most pristine and uninhabited regions in the world, home to some of the most imp...

This presentation was done in the Scientific Groups Meeting for London Convention and Protocol (LC/SG 41 & LP/SG 12) Valparíso, Chile. Here we pitch about the impact of human activities and the consequences of marine litter on the environment, and how the remote sensing tools can help to improve our understanding about this enormous challenge.

This work presents the preliminary results of the first field calibration campaign performed in the Atacama Desert, Chile, between the 18 and 22 August 2014, called the Atacama Field Campaign (ATAFIC 2014). In situ measurements were performed in order to spectrally characterize the surface reflectance spectra between 0.3 and 2.5 µm, radiometric tem...

Land surface temperature (LST) is one of the sources of input data for modeling land surface processes. The Landsat satellite series is the only operational mission with more than 30 years of archived thermal infrared imagery from which we can retrieve LST. Unfortunately, stray light artifacts were observed in Landsat-8 TIRS data, mostly affecting...

p>Torres del Paine National Park (PNTP) is characterized as a representative geographical area of the world’s ecosystems, containing high scenic beauty and wide variety of ecosystems. The aim of this work is to analyze the spatial and temporal trends of vegetation at PNTP using remote images from the Landsat platforms, the MOD13A3 product from the...

Disponible: http://repositorio.uchile.cl/handle/2250/147838

Monitoring evapotranspiration in arid and semi-arid environments plays a key role in water irrigation scheduling for water use efficiency. This work presents an operational method for evapotranspiration retrievals based on disaggregated Land Surface Temperature (LST). The retrieved LSTs from Landsat-8 and MODIS data were merged in order to provide...

Offshore wind energy potential and its technical and economic feasibility were determined in Chile. Wind speed data from ERA-Interim reanalysis 10 m above the sea surface between 1979 and 2014 was used. The capacity factor and performance of the V164–8.0 MW wind generator was also determined. Using this information along with data from other studie...

El poliestireno expandido comúnmente llamado “plumavit” es uno de los principales Residuos Antropogénicos Marinos (RAM) generados por la actividad salmonícola y mitícola en la zona de Chiloé. Uno de los impactos negativos de este material cuándo deriva en playas y costas, es que a la intemperie sufre un proceso de meteorización ambiental (agua, sol...

The remotely sensed land surface temperature (LST) is a key parameter to monitor surface energy and water fluxes but the strong impact of topography on LST has limited its use to mostly flat areas. To fill the gap, this study proposes a physically-based method to normalize LST data for topographic - namely illumination and elevation - effects over...

This paper presents a spectral reflectance characterization of the specie Quillaja saponaria (Mol.), endemic tree of Chile and valued by society due to its provision of several ecosystem services that gives to society and also for its high concentration of saponins in cortex widely used in the pharmacological industry. For spectral characterization...

p align="justify">In remote sensing, validation exercises are essential to ensure the quality of the products originated from satellite Earth observations. To assess the measurement uncertainty derived from satellite products, several ground field data from different ecosystems must be available for use. In the same order of importance, it is neces...

The El Niño-Southern Oscillation (ENSO) is the main driver of interannual climate extremes in Amazonia and other tropical regions. The current 2015/2016 EN event was expected to be as strong as the EN of the century in 1997/98, with extreme heat and drought over most of Amazonian rainforests. Here we show that this protracted EN event, combined wit...

The absolute radiometric calibration of a satellite sensor is the critical factor that ensures the usefulness of the acquired data for quantitative applications on remote sensing. This work presents the results of the first cross-calibration of the sensor on board the Sistema Satelital de Observación de la Tierra (SSOT) Chilean satellite or Air For...

A set of Essential Climate Variables (ECV) have been defined to be monitored by current and new remote sensing missions. The ECV retrieved at global scale need to be validated in order to provide reliable products to be used in remote sensing applications. For this, test sites are required to use in calibration and validation of the remote sensing...

With the current remote sensing technology developments, and in particular those at L-band (1.2–1.4 GHz) frequencies such as the Soil Moisture and Ocean Salinity and the Soil Moisture Active and Passive missions, new approaches concerning passive microwave and its combination with existing optical technologies have become of special interest for th...

This work presents the calibration and evaluation of an optical–passive microwave method for retrieving soil moisture (SM) at regional scale using remote sensing and reanalysis data. Several data sets were used, such as the bipolarized brightness temperature provided by SM and Ocean Salinity (SMOS) L3 brightness temperature product, the Normalized...

The application of Earth observation sensor data in quantitative approaches calls on the conversion of original digital numbers to radiometric quantities such as radiance or reflectance. This conversion depends on the sensor absolute calibration. One of the postlaunch methods adopted to calibrate orbital sensors is the reflectance-based approach. A...

Remote sensing and climate digital products have become increasingly available in recent years. Access to these products has favored a variety of Digital Earth studies, such as the analysis of the impact of global warming over different biomes. The study of the Amazon forest response to drought has recently received particular attention from the sc...

The Meteosat Second Generation-Spinning Enhanced Visible and Infrared Imager (MSG-SEVIRI) instrument provides observations of half the globe every 15 min, at low spatial resolution. These data are an invaluable tool to observe daily to yearly cycle of land surface temperature (LST), as well as for various early warning systems. However, advanced al...

Soil moisture is one of the biosphere's most essential climatic variables. However, its periodical monitoring at regional scales using in-situ measurements is complex. In this context, L-band microwaves observations from passive remote sensors appear as an important tool for the periodical estimation of soil moisture at regional scales. In this wor...

This document describes the intensive field campaign and vegetation ground data (LAI, FAPAR, FCover) collected at San Fernando site - Chile during the 19th-20th of January 2015, and the up-scaling of the ground data using high resolution Fasat-C imagery to derive ground-based maps of the biophysical variables.

Soil moisture is one of the biosphere's most essential climatic variables. However, its periodical monitoring at regional scales using in-situ measurements is complex. In this context, L-band microwaves observations from passive remote sensors appear as an important tool for the periodical estimation of soil moisture at regional scales. In this wor...

Evapotranspiration is an essential component for the assessment of water dynamic in agriculture and the estimation of water demand by crops. Its estimation becomes more difficult over row crops due to differences between canopy and inter-row space. In this work, lysimeter data was combined and integrated with radiative and meteorological data to ev...

This paper presents the Global Atmospheric Profiles derived from Reanalysis Information (GAPRI) database, which was designed for earth surface temperature retrieval. GAPRI is a comprehensive compilation of selected atmospheric vertical profiles at global scale which can be used for radiative transfer simulation in order to obtain generalized algori...

Advances in information technologies and accessibility to climate and satellite data in recent years have favored the development of web-based tools with user-friendly interfaces in order to facilitate the dissemination of geo/biophysical products. These products are useful for the analysis of the impact of global warming over different biomes. In...

The Cordillera Blanca, located in the central zone of the Andes Mountains in Peru, has shown a retreat in its glaciers. This paper presents a trend analysis of the glacier area over the groups of Nevados Caullaraju-Pastoruri from 1975 to 2010 using Landsat-5 Thematic Mapper (TM) imagery. In the case of the Nevados Pastoruri/Tuco, the study period w...

Ground vegetation measurements (i.e., LAI, FAPAR, FCover) were collected over the agricultural site of San Fernando ( 34º 43’ 23.88’’ S; 71º 0’ 5.42’’ W) in Chile (January 19-20th). Digital Hemispherical photos were used to estimate the biophysical variables using the CAN-EYE software. The protocol for sampling the site (5x5 km2) and each Elementar...

The calibration/validation of remote sensing products is a key step that needs to be done before its use in dif- ferent kinds of environmental applications and to ensure the success of remote sensing missions. In order to compare the measurements from remote sensors on spacecrafts and airborne platforms with in-situ data, it is necessary to per- fo...

Remote sensing techniques are a useful tool for continuous observation of the Earth at global scale. However, products derived from remote sensing data require a rigorous validation using in situ data. Moderate Resolution Imaging Spectroradiometer (MODIS) is not really a sounding instrument, but it does have 16 infrared bands (bands 20-36 covering...

The importance of land surface temperature (LST) retrieved from high to medium spatial resolution remote sensing data for many environmental studies, particularly the applications related to water resources management over agricultural sites, was a key factor for the final decision of including a thermal infrared (TIR) instrument on board the Lands...

This work presents a statistical calibration of a semi-empirical combined optical-passive microwave remote sensing method to estimate surface soil moisture at regional scale. The proposed method uses satellite data provided by different sensors such as: bi-polarized brightness temperature (HV polarizations) at L-band given by the Soil Moisture and...

Provision of reliable ground reference datasets is mandatory for the validation of satellite products. The ground data should be collected considering the spatial variability of the sites in agreement with the recommendations of the CEOS WGCV Land Product Validation subgroup for validation of moderate resolution satellite products. This paper descr...

In this paper, we analyze the feasibility of applying the temperature and emissivity separation (TES) algorithm to thermal-infrared data acquired with three bands of the Spinning Enhanced Visible and Infrared Imager (SEVIRI) onboard the Meteosat Second Generation platform (SEVTES). The performance of the SEVTES algorithm was tested using data simul...

Evaluation of evapotranspiration (ET) estimates over large areas is necessary before they can be used. This work presents the preliminary results of the “Hydric demand model for improving basin water management” project carried out in the Copiapó Basin, which is located in the southern boundary of the Atacama Desert, Chile. As a first approach to e...

Soil moisture has been defined as one of the essential climate variables by several worldwide climate and earth observation expert panels. During the last decades several explorer mission have been launched in order to obtain reliable results of soil moisture at global scale. The most recent and successfully lunched project is the Soil Moisture and...

This work presents the first offshore wind potential estimation over the coast of Chile using long term data series from “QuikSCAT (V04) wind vectors” and ERA-interim’s wind product between 1999-2009 and 1979-2012, respectively. Weibull and Rayleigh’s distribution were used to adjust the data series from the study period to find the probability den...

This work describes the first in-flight absolute calibration of the “Sistema Satelital para la Observación de la Tierra” (SSOT or Fasat-C). It was performed on January 29th 2013 at Antumapu site located in the southern area of Santiago, Chile. A description of the procedure is presented which includes both ground measurement and atmospheric charact...

The semi-arid region of Chile has gained great relevance in the recent decades mainly due to the constant desertif ication process it's suffering, the increase of climatic extreme events occurrence and the decrease in the precipitation volume. This scenario makes the region a zone of great scientific relevance to the scientific community for the st...

The Intergovernmental Panel on Climate Change (IPCC) reported a significant rise of the global mean surface temperature over the last 100. years, with a rate of warming over the last few decades almost double that over the last 100. years. The rate of warming is higher at land surfaces over the Northern Hemisphere (NH), and particularly extreme war...