Papers by Carlos C. DaCamara
Complex interactions of extreme events in Southern Europe and Brazil: a compound event perspective
<p>Record-breaking natural hazards occur regularly throughout the world, leading to... more <p>Record-breaking natural hazards occur regularly throughout the world, leading to a variety of impacts [1]. According to the WMO, since 1970 there were more than 11000 reported disasters attributed to these hazards globally, with just over 2 million deaths and US$ 3.64 trillion in losses [2]. From 1970 to 2019, weather, climate and water hazards accounted for 50% of all disasters, 45% of all reported deaths and 74% of all reported economic losses [2]. Droughts and heatwaves are both included in the top 4 disasters in terms of human losses [2], with uneven impacts throughout the world and a high likelihood that anthropogenic climate forcing will increase economic inequality between countries [3].</p><p>Nowadays there is strong evidence that droughts and heatwaves are at times synergetic and that their combined occurrence is largely caused by land-atmosphere feedbacks [4]. In fact, increasing trends of Compound Dry and Hot (CDH) events have been observed in both South America [5,6] and Europe [7,8], some of them with aggravated impacts. Specifically, the severe 2020 Pantanal extreme fire season (Brazil) resulted from the interplay between extreme and persistent temperatures (maximum temperatures 6 ºC above-average) and long-term soil dryness conditions [6]. Similarly, in the Iberian Peninsula, CDH events were shown to have an influence on the dramatic 2017 fire season [9] and also on crop losses [8]. Moreover, future climate projections suggest that CDH conditions are expected to become more common in a warming climate [4]. Therefore, it is very important to address weather events in a compound manner, identifying synergies, driving mechanisms and dominant atmospheric modes controlling single and combined hazards.</p><p>[1] IPCC, 2021: Climate Change 2021: The Physical Science Basis. Contribution of WGI to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte  V. et al., (eds.)]. Cambridge University Press. </p><p>[2] WHO, 2021. Weather-related disasters increase over past 50 years, causing more damage but fewer deaths, https://public.wmo.int/en/media/press-release/weather-related-disasters-increase-over-past-50-years-causing-more-damage-fewer</p><p>[3] Diffenbaugh N.S., Burke M. (2019) Global warming has increased global economic inequality, PNAS, 116, 20, 9808-9813</p><p>[4] Zscheischler J. et al. (2018). Future climate risk from compound events. Nat. Clim. Change, 8, 469–477.</p><p>[5] Geirinhas J.L. et al. (2021). Recent increasing frequency of compound summer drought and heatwaves in Southeast Brazil. Environ. Res.  Lett., 16(3).</p><p>[6] Libonati R. <em>et al</em> (2022) Assessing the role of compound drought and heatwave events on unprecedented 2020 wildfires in the Pantanal,<em> Environ. </em><em>Res. Lett.</em> <strong>17</strong> 015005.</p><p>[7] Geirinhas J.L. et al. (2020) Heat-related mortality at the beginning of the twenty-first century in Rio de Janeiro, Brazil. Int. J. Biometeorol., 64, 1319–1332</p><p>[8] Russo A. et al. (2019) The synergy between drought and extremely hot summers in the Mediterranean. Environ. Res. Lett., 14, 014011</p><p>[9] Ribeiro A.F.S. et al. (2020) Risk of crop failure due to compound dry and hot extremes estimated with nested copulas. Biogeosciences, 17, 4815–4830</p><p>[10] Turco M. et al. (2019) Climate drivers of the 2017 devastating fires in Portugal. Sci. Rep., 9, 1</p><p> </p><p><em>This work was supported by Fundação para a Ciência e a Tecnologia (Portugal) under projects PTDC/CTA-CLI/28902/2017, PTDC/CTA-CLI/28902/2017 and FCT- UIDB/50019/2020 –IDL. </em></p><p><em> </em></p><p> </p>
Putting fire on the map of Brazilian savanna ecoregions
Journal of Environmental Management, 2021
The Brazilian savanna (Cerrado) is considered the most floristically diverse savanna in the world... more The Brazilian savanna (Cerrado) is considered the most floristically diverse savanna in the world, home to more than seven thousand species. The region is a mosaic of savannas, grasslands and forests whose unique biophysical and landscape attributes are on the basis of a recent ecoregional map, paving the way to improved region-based strategies for land management actions. However, as a fire-prone ecosystem, Cerrado owes much of its distribution and ecological properties to the fire regime and contributes to an important parcel of South America burned area. Accordingly, any attempt to use ecoregion geography as a guide for management strategies should take fire into account, as an essential variable. The main aim of this study is to complement the ecoregional map of the Cerrado with information related to the fire component. Using remotely sensed information, we identify patterns and trends of fire frequency, intensity, seasonality, extent and scar size, and combine this information for each ecoregion, relying on a simple classification that summarizes the main fire characteristics over the last two decades. Results show a marked north-south fire activity gradient, with increased contributions from MATOPIBA, the latest agricultural frontier. Five ecoregions alone account for two thirds of yearly burned area. More intense fires are found in the Arc of Deforestation and eastern ecoregions, while ecoregions in MATOPIBA display decreasing fire intensity. An innovative analysis of fire scars stratified by size class shows that infrequent large fires are responsible for the majority of burned area. These large fires display positive trends over many ecoregions, whereas smaller fires, albeit more frequent, have been decreasing in number. The final fire classification scheme shows well defined spatially-aggregated groups, where trends are found to be the key factor to evaluate fire within their regional contexts. Results presented here provide new insights to improve fire management strategies under a changing climate.
Ecological Indicators, 2020
Precipitation decline and vegetation fires in the Amazon region associated with climate change an... more Precipitation decline and vegetation fires in the Amazon region associated with climate change and deforestation expose local communities to hazardous air quality that may lead to damages in human health such as diseases of the respiratory system. Since 2000, drought incidence over the Amazon has been observed at a higher frequency than during the last century, and the effects of the drier climate and fires on human health remain uncertain. Understanding the roles played by precipitation decline and fire activity as well as associated changes of atmospheric parameters on the incidence of respiratory diseases hospitalizations (RDH) is a very complex task, and it is likely that the relative importance of those factors depends on the temporal and spatial variability used in the analysis. This work aims at serving as an updated reference that covers the impact of fire incidence on respiratory diseases in Porto Velho, the third most populated city of Brazilian Amazon, with emphasis on drought events from 2000 to 2016. For this purpose, we compare remote sensing data, meteorological variables and health indicators, that include RDH, in particular for children under five years old (RDH5) and people aged more than sixty (RDH60), as well as Asthma and Bronchitis hospitalizations. Here we show an increase of 27% in RDH (except for Asthma that decreased 75%) in drought years as described by the positive (negative for Asthma) relationship with rainfall. Rainfall and humidity exert a primary control in diseases of the respiratory system in the region. Hotspots, burned areas and smoke concentrate in August and September, and have a secondary influence of fire on RDH. Smoke production is strongly related to fire and temperature, which are associated with an increase in the number of hospitalizations during the fire season. RDH5 and RDH60 are respectively 11 and 22 times higher than RDH (for all ages), confirming the higher vulnerability for children and elderlies. Based on the observed data, we highlight the role of regional precipitation trends in driving respiratory hospitalizations, which are crucial ecological indicators for humans in the context of climate change.
Remote Sensing of Environment, 2018
Land surface temperature (LST) values retrieved from satellite measurements in the thermal infrar... more Land surface temperature (LST) values retrieved from satellite measurements in the thermal infrared (TIR) may be strongly affected by spatial anisotropy. Different parametric approaches have been proposed to simulate such effects. These are relatively simple models requiring few input data and therefore appropriate to simulate directional effects in satellite LST retrievals over large areas. The purpose of this study is to consistently evaluate the performance of two parametric models (the so-called Kernel and Hotspot models), and to assess their respective potential to correct directional effects on LST for a wide range of surface conditions, in terms of tree coverage, vegetation density, surface emissivity. We also propose an optimization of the correction of directional effects through a synergistic use of both models. The Kernel model allows an effective simulation of LST directionality associated with shadowing effects and emissivity anisotropy, but results show that it significantly underestimates the amplitude of the angular corrections. The Hotspot model performs better in simulating anisotropy related to shadowing effects. However, it is unable to account for emissivity anisotropy, showing lower performance than the Kernel model for nighttime data and for low tree coverage. The combined Kernel-Hotspot model provides corrections on LST directionality with reliable quality, with particularly improved performance during nighttime and for low tree densities.
Agricultural and Forest Meteorology, 2017
Southern European countries are particularly affected by summer wildfires and drought events. The... more Southern European countries are particularly affected by summer wildfires and drought events. The occurrence of extreme meteorological conditions during preceding and contemporaneous months amplifies the risk of summer wildfires. The main scope of this study was to investigate the impact of drought periods on burned areas in the Iberian Peninsula. This will be achieved through the comparison of time series of two widely used multiscalar drought indices (SPI and SPEI) calculated for each province and then associated with the time series of the standardized logarithm of normalized burned areas during the fire summer season. The SPI and SPEI were both calculated for the time scales spanning between 2 to 12 months and for each month from January to August, between 1980 and 2005. Based on the regression analysis between drought indicators and burned areas, the months that present lowest errors were identified for each province. From the obtained results two main conclusions were reached: (i) the association between drought and fires is a local scale process and should be analyzed at the province or sub-province level rather than at the country or continental level; (ii) the relation between wildfires and drought is better explained by the influence of the spring precipitation on the central sector and by the influence of temperature and precipitation during summer on most of the Portuguese provinces.
Terrestrial, Atmospheric and Oceanic Sciences, 1993
From a 34-year data period, twelve major winter blocking episodes in the northern hemisphere are ... more From a 34-year data period, twelve major winter blocking episodes in the northern hemisphere are selected for examination: four episodes for each category of Pacific, Atlantic and double blocking. It is shown that the single blockings in the Pacifi c or Atlantic are formed through constructive inter ference of the traveling zonal wave of n=l and stationary wave of n=2. The n=l is supported by the energy input through the nonlinear wave-wave in• teraction, and the n=2 by in situ warming over the Pacific and Atlantic. The concurrent double blocking in the Pacific and Atlantic are formed by the stationary n=2 when the traveling n=l is weak. The negative anomaly fields of sea surface temperatures in the Pacific and Atlantic are associated with the single blocking in the Pacific and Atlantic. On the contrary, the positive ve anomalies in both the Pacific and Atlantic are associated with concurrent Pacifi c and Atlantic blockings, indicating the baroclinic nature of the double blocking.
A User-Oriented Simplification of the ($V,W$) Burn-Sensitive Vegetation Index System
IEEE Geoscience and Remote Sensing Letters, 2016
Remote sensing from spaceborne sensors combining near- and middle-infrared information has proved... more Remote sensing from spaceborne sensors combining near- and middle-infrared information has proved to be an efficient means to monitor the effects of vegetation fires. Burn-sensitive spectral indices, such as the (V, W) index system, have been developed and successfully applied for burned area discrimination. The (V, W) index system provides useful capability to discriminate burned pixels, but the elaborate numerical computations involved are a major drawback in operational applications. This letter presents a simplified algorithm to compute the approximate values of indices V and W. The methodology developed is tested in a region located in the Brazilian Cerrado using remote-sensed data from the MODIS instrument. The simplification allows performing burned area discrimination with the same quality as the original algorithm. The methodology may be extended to other sensors and different combinations of bands and opens new perspectives to the generation of synergic longterm databases of burned area.
Supporting FIRE-suppression strategies combining fire spread MODelling and SATellite data in an operational context in Portugal: the FIRE-MODSAT project
Tellus A: Dynamic Meteorology and Oceanography, 1999
The vertical structure equation (VSE) is solved by a Galerkin method as used by Kasahara. The sen... more The vertical structure equation (VSE) is solved by a Galerkin method as used by Kasahara. The sensitivity of the vertical decomposition to the truncation order of the Legendre polynomials series is studied, with the aim of finding an adequate truncation order for a given data set. Obtained results show that: (1) the vertical scale decomposition presents little sensitivity to the truncation order; (2) the order of truncation may be greater than the number of discrete levels in the data set. It is finally shown that the proposed choice of truncation order may overcome the problem of aliasing in the higher internal modes.
Citeseer
Abstract–Identification of cloud systems over continental regions is a difficult task given on th... more Abstract–Identification of cloud systems over continental regions is a difficult task given on the one hand the variability in space and time of the radiative properties of the land surface and on the other the non-homogeneous character of the background. Cloud systems also ...
Revista Brasileira de Meteorologia, 2009
Nesse artigo é apresentada uma comparação entre o diagnóstico de bloqueios para o Hemisfério Sul,... more Nesse artigo é apresentada uma comparação entre o diagnóstico de bloqueios para o Hemisfério Sul, identificados em uma simulação com o modelo de circulação geral do Hadley Centre (HadCM3), e aqueles obtidos das reanálises do NCEP/NCAR, para o período de 1960 a 2000. A definição de bloqueio usada baseia-se no cálculo de dois gradientes meridionais da altura geopotencial em 500 hPa. O ciclo sazonal e as regiões preferenciais de ocorrência dos bloqueios foi bem simulada pelo modelo. Semelhante ao que foi encontrado a partir das reanálises, o modelo identificou como área preferencial de ocorrência de bloqueios o Pacífico Sul e Oceania. A freqüência dos bloqueios simulada pelo modelo foi semelhante à observada, com maior atividade verificada no inverno e início da primavera (junho até setembro).
Pure and Applied Geophysics, 2008
This work presents an updated climatology of blocking episodes for the Southern Hemisphere betwee... more This work presents an updated climatology of blocking episodes for the Southern Hemisphere between 1960 and 2000, based on data from NCEP/NCAR reanalysis. Five contiguous areas of blocking activity are considered; Southeastern Pacific, Southwestern Pacific, Atlantic, Indian and Oceania. The impact of the three most important areas of onset blocking episodes (Southeastern Pacific, Atlantic and Oceania) upon the climate of the adjacent continental areas (South America and Australia) was evaluated. Composites of the meteorological variables (temperature and precipitation) were obtained for periods of diagnosed blockings. The impact of the blocking episodes over the climate of South America and Australia is highlighted whenever anomaly fields of temperature and precipitation are significant at the 5% and 10% levels, respectively. Impacts of Southeastern Pacific and Atlantic blockings are observed on the temperature field over several regions of South America. Significantly higher (lower) temperatures than climatology occur in southern Brazil, northern Argentina, Uruguay and Paraguay, and lower (higher) than climatology in the extreme south of South America for the Southeastern Pacific (Atlantic) blocking episodes. Precipitation over South America is also affected by the Southeastern Pacific and Atlantic blockings in different ways. The Southeastern Pacific blocking has higher impact on precipitation in summer (dry conditions in northeast Brazil) and spring (wet conditions in central and southern Brazil), while the Atlantic blocking affects precipitation in autumn and winter (wet conditions in parts of central and southern Brazil). The blocking cases over Oceania affect southeastern Australia with normal to higher than climatological precipitation and with negative temperature anomalies in that region. Finally we provide a detailed analysis of a South Atlantic blocking episode, which occurred between the 4 th and the 8 th of June 1997. This event shows clearly the split of the jet stream into two branches (subtropical and polar) surrounding the anticyclonic sector, and satellite imagery revealed the presence of transient systems in the periphery of the blocking anticyclone responsible for high values of precipitation in the southeastern sector of South America.
Ozone concentrations observed in a background station located in a rural region in the North of P... more Ozone concentrations observed in a background station located in a rural region in the North of Portugal reveal several episodes of extremely high concentration values, raising the question of whether such extreme episodes result mainly from stratospheric intrusion events or from local scale air-pollution transport and transformation processes. An extensive analysis is performed on the atmospheric circulation over the North Atlantic and the European sectors in order to identify the physical mechanisms that may account for recorded exceedances during the period 2004-2007. The study relies on thermohydrodynamical fields from the reanalysis data set of NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) and obtained results provide evidence of the contribution from cross-tropopause exchanges. In particular, it will be shown that Stratosphere to Troposphere Transport (STT) events take place over the Atlantic Ocean and Europe, move east with...
Journal of the Atmospheric Sciences, 2002
The 3D structures of the free oscillations of an adiabatic and hydrostatic atmosphere around a ba... more The 3D structures of the free oscillations of an adiabatic and hydrostatic atmosphere around a basic state at rest were used as a physical filtering for atmospheric data. This filtering procedure allows for the consideration of the three primitive variables (u, ,) over the whole atmosphere simultaneously. Accordingly, the computed statistics do not simply rely on the information provided by a single variable of circulation, such as the 500-hPa geopotential field. Using this method, two classical patterns were isolated in the barotropic component of the circulation, one resembling the Pacific-North America (PNA) pattern, the other similar to the North Atlantic Oscillation (NAO) pattern in summer. Associating the barotropic and the second baroclinic components, a coupling in variability was retrieved between the strength of the winter stratospheric polar vortex and the tropospheric circulation over the North Atlantic. Until now these modes had only been recovered by means of statistical analysis. This study shows their existence in physically filtered fields. The obtained results make clear that the observed winter pattern of NAO is not a simple variability mode of the atmosphere, but results instead from mean flow wave interaction that modulates tropospheric planetary Rossby waves. The association between the NAO circulation variability patterns and the anomalies of the 850-hPa temperature field was also investigated.
Journal of the Atmospheric Sciences, 2009
An analysis is performed on the dynamical coupling between the variability of the extratropical s... more An analysis is performed on the dynamical coupling between the variability of the extratropical stratospheric and tropospheric circulations during the Northern Hemisphere winter. Obtained results provide evidence that in addition to the well-known Charney and Drazin mechanism by which vertical propagation of baroclinic Rossby waves is nonlinearly influenced by the zonal mean zonal wind, topographic forcing constitutes another important mechanism by which nonlinearity is introduced in the troposphere–stratosphere wave-driven coupled variability. On the one hand, vortex variability is forced by baroclinic Rossby wave bursts, with positive (negative) peaks of baroclinic Rossby wave energy occurring during rapid vortex decelerations (accelerations). On the other hand, barotropic Rossby waves of zonal wavenumbers s = 1 and 3 respond to the vortex state, and strong evidence is presented that such a response is mediated by changes of the topographic forcing due to zonal mean zonal wind ano...
A Synergetic Use of Remote-Sensed Data to Assess the Evolution of Burnt Area by Wildfires in Portugal
eumetsat.int
... Teresa J. Calado and Carlos C. DaCamara ... Operational Phase (CDOP) information from new sen... more ... Teresa J. Calado and Carlos C. DaCamara ... Operational Phase (CDOP) information from new sensors will be incorporated in the LSA SAF system, namely from the AVHRR and MODIS sensors, respectively on-board the NOAA and Metop series and the TERRA and AQUA ...
Monitoring Burnt Areas in Portugal Using NOAA/AVHRR Imagery
Intercalibration of NOAA and Meteosat window channel brightness temperatures
International Journal of Remote Sensing, 2005
This study presents an intercalibration of Meteosat‐5 11 µm channel and NOAA‐14 10.8 µm and 12.0 ... more This study presents an intercalibration of Meteosat‐5 11 µm channel and NOAA‐14 10.8 µm and 12.0 µm channels, and their comparison for sea and land pixels. The intercalibration empirical relation is derived for clear‐sky sea measurements, with similar zenith viewing angles. The root mean square difference between NOAA‐14 and Meteosat‐5 intercalibrated brightness temperatures is about 1.4 K (4.7 K) for all clear‐sky sea (land) pixels.
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Papers by Carlos C. DaCamara