Droughts Over Amazonia in 2005, 2010, and 2015: A Cloud Cover Perspective

Amazon forests experienced recent severe droughts in an anomalous short period induced by different mechanisms and had different length periods and spatial patterns. Droughts of 2005 and 2010 were attributed to anomalous Sea Surface Temperature (SST) over the Tropical North Atlantic (TNA) during the dry season, but the 2010 drought was more severe and remained for a longer period because it was also induced in late 2009 by a moderate to strong El Niño (EN). Drought in 2015 led to unprecedented warming and extreme soil moisture deficits over some regions, and it was attributed to a very strong EN. Several studies analyzed these drought events regarding different climatic factors such as anomalies in SST, vegetation, temperature, precipitation, soil moisture deficits, solar radiation, etc. However, we have not identified a complete analysis of total cloud cover (TCC) over Amazonia during these drought events in the context of long-term trends and past strong EN events. This brief report aims to present a preliminary analysis of anomalies in TCC over Amazon using reanalysis data with a focus on the last recent drought events into a long-term context. Results show a significant decreasing trend (p < 0.05) for TCC over southern Amazonia during the dry season (around −2% per decade), in contrast to the significant increasing trend found over northern Amazonia during this season and the significant widespread increasing trend during the wet season (between +2 and +4% per decade). Correlation analysis between SST and TCC anomalies is also indicative of the different West-East and North-South patterns linked to EN events or drought episodes driven by TNA warm anomalies

Future Projections of Fire Occurrence in Brazil Using EC-Earth Climate Model

Fire has a fundamental role in the Earth system as it influences global and local ecosystem patterns and processes, such as vegetation distribution and structure, the carbon cycle and climate. Since, in the global context, Brazil is one of the regions with higher fire activity, an assessment is here performed of the sensitivity of the wildfire regime in Brazilian savanna and shrubland areas to changes in regional climate during the 21st Century, for an intermediate scenario (RCP4.5) of climate change. The assessment is based on a spatial and temporal analysis of a meteorological fire danger index specifically developed for Brazilian biomes, which was evaluated based on regional climate simulations of temperature, relative humidity and precipitation using the Rossby Centre Regional Climate Model (RCA4) forced by the EC-Earth earth system model. Results show a systematic increase in the extreme levels of fire danger throughout the 21st Century that mainly results from the increase in maximum daily temperature, which rises by about 2 °C between 2005 and 2100. This study provides new insights about projected fire activity in Brazilian woody savannas associated to climate change and is expected to benefit the user community, from governmental policies to land management and climate researches

Near- and Middle-Infrared Monitoring of Burned Areas from Space

We describe a methodology to discriminate burned areas and date burning events that use a burn-sensitive (V, W) index system defined in near-/mid-infrared space. Discrimination of burned areas relies on a monthly composite of minimum of W and on the difference between this composite and that of the previous month. The rationale is to identify pixels with high confidence of having burned and aggregate new burned pixels on a contextual basis. Dating of burning events is based on the analysis of time series of W, and searching for the day before maximum temporal separability is achieved. The procedure is applied to the fire of Monchique, a large event that took place in the southwest of Portugal in August 2018. When the obtained pattern of burned pixels is compared against a reference map, the overall accuracy is larger than 99%; the commission and omission errors are lower than 5 and 10%, respectively; and the bias and the Dice coefficient are above 0.95 and 0.9, respectively. Differences between estimated dates of burning and reference dates derived from remote-sensed observations of active fires show a bias of 0.03 day and a root mean square difference of 0.24 day

The North Atlantic oscillation and European vegetation dynamics

The relationship between vegetation greenness and the North Atlantic Oscillation (NAO) is assessed over Europe. The study covers the 21-year period from 1982 to 2002 and is based on monthly composites of the Normalised Difference Vegetation Index (NDVI) and Brightness Temperature from the Global Inventory Monitoring and Modelling System (GIMMS) as well as on monthly precipitation from the Global Precipitation Climatology Centre (GPCC). A systematic analysis is first performed of point correlation fields over the 21-year period between the winter NAO index and spring and summer NDVI, followed by an assessment of the vegetation response to precipitation and temperature conditions in winter, over two contrasting regions, namely the Iberian Peninsula and Northeastern Europe. Finally, the impact of NAO on vegetation dynamics over the two regions is evaluated by studying the corresponding annual cycles of NDVI and comparing their behaviour for years associated with opposite NAO phases. Over the Iberian Peninsula there is strong evidence that positive (negative) values of winter NAO induce low (high) vegetation activity in the following spring and summer seasons. This feature is mainly associated with the impact of NAO on winter precipitation, together with the strong dependence of spring and summer NDVI on water availability during the previous winter. Northeastern Europe shows a different behaviour, with positive (negative) values of winter NAO inducing high (low) values of NDVI in spring, but low (high) values of NDVI in summer. This behaviour mainly results from the strong impact of NAO on winter temperature, associated with the critical dependence of vegetation growth on the combined effect of warm conditions and water availability during the winter seaso

Recent increasing frequency of compound summer drought and heatwaves in Southeast Brazil

An increase in the frequency of extremely hot and dry events has been experienced over the past few decades in South America, and particularly in Brazil. Regional climate change projections indicate a future aggravation of this trend. However, a comprehensive characterization of drought and heatwave compound events, as well as of the main land-atmosphere mechanisms involved, is still lacking for most of South America. This study aims to fill this gap, assessing for the first time the historical evolution of compound summer drought and heatwave events for the heavily populated region of Southeast Brazil and for the period of 1980-2018. The main goal is to undertake a detailed analysis of the surface and synoptic conditions, as well as of the land-atmosphere coupling processes that led to the occurrence of individual and compound dry and hot extremes. Our results confirm that the Sao Paulo, Rio de Janeiro and Minas Gerais states have recorded pronounced and statistically significant increases in the number of compound summer drought and heatwave episodes. In particular, the last decade was characterized by two austral summer seasons (2013/14 and 2014/15) with outstanding concurrent drought and heatwave conditions stemmed by severe precipitation deficits and a higher-than-average occurrence of blocking patterns. As result of these land and atmosphere conditions, a high coupling (water-limited) regime was imposed, promoting the re-amplification of hot spells that resulted in mega heatwave episodes. Our findings reveal a substantial contribution of persistent dry conditions to heatwave episodes, highlighting the vulnerability of the region to climate change

Mapeamento de Áreas Queimadas em Unidades de Conservação da Região Serrana do Rio de Janeiro Utilizando o Satélite Landsat-8 Durante a Seca de 2014

Entre janeiro de 2014 e fevereiro de 2015, a região Sudeste do Brasil experimentou uma das maiores secas de sua história, favorecendo um aumento significativo no número de incêndios florestais na Região Serrana do Rio de Janeiro (RSRJ). Neste contexto, o objetivo deste trabalho é mapear a extensão das áreas queimadas via sensoriamento remoto, em três Unidades de Conservação da RSRJ: Área de Proteção Ambiental (APA) de Petrópolis, Parque Nacional da Serra dos Órgãos (PARNASO) e Reserva Biológica (REBIO) de Araras. A estimativa das áreas queimadas é feita com base no índice de queimadas W utilizando imagens pré e pós-fogo das bandas 5 (0,88 μm) e 7 (2,11 μm) do sensor OLI/Landsat-8. Limiares espaciais e temporais de W foram estabelecidos e o mapeamento foi realizado considerando a superfície modelada através do Modelo Digital de Elevação SRTM Plus. O total de área queimada estimada foi de 3904 ha, a APA, PARNASO e REBIO com 2819 ha, 850 ha e 236 ha respectivamente. Os resultados foram corroborados pelos focos de calor obtidos por satélites provenientes do Banco de Dados de Queimadas do INPE e pelos pareceres técnicos oficiais elaborados in situ pelo Instituto Chico Mendes de Conservação da Biodiversidade (ICMBio)

Changes in land use enhance the sensitivity of tropical ecosystems to fire-climate extremes

The Pantanal, the largest contiguous wetland in the world with a high diversity of ecosystems and habitat for several endangered species, was impacted by record-breaking wildfires in 2020. In this study, we integrate satellite and modeling data that enable exploration of natural and human contributing factors to the unprecedented 2020 fires. We demonstrate that the fires were fueled by an exceptional multi-year drought, but dry conditions solely could not explain the spatial patterns of burning. Our analysis reveals how human-caused fires exacerbated drought effects on natural ecosystem within the Pantanal, with large burned fractions primarily over natural (52%), and low cattle density areas (44%) in 2020. The post-fire ecosystem and hydrology changes also had strong ecological effects, with vegetation productivity less than − 1.5 σ over more than 30% of the natural and conservation areas. In contrast to more managed areas, there was a clear decrease in evaporation (by ~ 9%) and an increase in runoff (by ~ 5%) over the natural areas, with long-term impacts on ecosystem recovery and fire risk. This study provides the first tropical evidence outside rainforests of the synergy between climate, land management and fires, and the associated impacts on the ecosystem and hydrology over the largest contiguous wetlands in the world

Climatic characterization of heat waves in Brazil

De acordo com a última geração de modelos climáticos, a probabilidade de ocorrência de grandes ondas de calor nas próximas décadas tende a subir de forma significativa. Atualmente existem inúmeros estudos relativos a esta problemática no Hemisfério Norte, particularmente para a Europa e para a América do Norte, devido aos seus impactos significativos em áreas como a saúde, economia e agricultura. Em relação ao Hemisfério Sul e especialmente ao Brasil, este problema apresenta-se como uma questão ainda pouco desenvolvida, apesar da sua enorme área geográfica e população potencialmente afetada. Com este trabalho pretende-se realizar um estudo diagnóstico das ondas de calor observadas em algumas das grandes cidades brasileiras, incluindo a sua frequência, distribuição sazonal e evolução temporal desde a década de 1960. Os resultados obtidos evidenciam a presença de uma tendência positiva na frequência e duração das ondas de calor a partir de 1980, particularmente para as cidades de São Paulo, Manaus e Recife. Brasília registrou maior número de ondas de calor nas últimas décadas, enquanto o Rio de Janeiro apresentou o menor número de eventos. Quanto à variabilidade sazonal os meses de Outono/Inverno foram aqueles em que se verificou maior número de ondas de calor-----------------------------------------------------------Abstract According to the state-of-the-art global and circulation models the probability of occurrence of large heat waves in the following decades will increase significantly. Currently, due to their significant impacts in several socio-economic areas such as public health, energy production and consumption and agriculture, there are numerous studies for the Northern Hemisphere regions evaluating this problem. However, for the southern hemisphere and especially Brazil, a similar analysis is lacking, despite its huge geographical area and large population potentially affected. The main goal of this work is to provide a comprehensive diagnostic study of heat waves observed in several large Brazilian cities, including heat waves frequency, seasonal distribution and temporal evolution since the 1960s decade. In general, results indicate the presence of a positive trend in the frequency and duration of heat waves since the 1980s, with special emphasis to cities like São Paulo, Manaus and Recife. Brasília was the city that in the last decades recorded the highest number of heat waves while Rio de Janeiro was the city with the smallest number recorded. In respect to seasonal variability the Autumn/Winter months were the months with the largest number of heat waves recordedinfo:eu-repo/semantics/publishedVersio

Burned area mapping in the brazilian savanna using a one-class support vector machine trained by active fires

We used the Visible Infrared Imaging Radiometer Suite (VIIRS) active fire data (375 m spatial resolution) to automatically extract multispectral samples and train a One-Class Support Vector Machine for burned area mapping, and applied the resulting classification algorithm to 300-m spatial resolution imagery from the Project for On-Board Autonomy-Vegetation (PROBA-V). The active fire data were screened to prevent extraction of unrepresentative burned area samples and combined with surface reflectance bi-weekly composites to produce burned area maps. The procedure was applied over the Brazilian Cerrado savanna, validated with reference maps obtained from Landsat images and compared with the Collection 6 Moderate Resolution Imaging Spectrometer (MODIS) Burned Area product (MCD64A1) Results show that the algorithm developed improved the detection of small-sized scars and displayed results more similar to the reference data than MCD64A1. Unlike active fire-based region growing algorithms, the proposed approach allows for the detection and mapping of burn scars without active fires, thus eliminating a potential source of omission error. The burned area mapping approach presented here should facilitate the development of operational-automated burned area algorithms, and is very straightforward for implementation with other sensorsinfo:eu-repo/semantics/publishedVersio

Compound effects of drought and heat waves on fire incidence over the Amazon

Extreme drought events merely are no longer enough to provide the framework that explains exacerbated impacts of atmospheric conditions in vegetation fires. In particular, the coupled effect of Heat Waves (HW) induced by positive feedbacks between soil and atmosphere caused by drought patterns, is shown to be more likely to enhance flammability conditions. Thus, understanding the concurrence of both extreme climatic events (droughts and HWs) is crucial to quantify ecological and socioeconomic impacts of fire related to ecosystem services, human health, climate and conservation. Although these compound events are increasingly being subject of study around the globe, they are poorly explored over South America, in particular over the Amazon.Therefore, our first goal here is to analyze the simultaneous occurrence of heat waves during two major extreme droughts in Amazon rainforest, namely during the outstanding 2005 and 2010 events. Moreover, we aim to quantify the impact of these compound events on fire incidence and intensity. To accomplish these goals, we use meteorological fields from ERA-5 reanalysis, remote sensing platforms and in-situ data. HW events were assessed by analyzing the associated synoptic patterns and heat wave indexes based on temperature data from surface meteorological stations, from 1961 to 2014. The spatial and temporal patterns of fire activity were analyzed between 2003 and 2017, based on information obtained from AQUA MODIS Standard Fire products 1 km collection 6 of active fire (AF) and fire radiative power (FRP) datasets.Results show an increase of HWs during drought periods along with a rise in number of these events over the last two decades at the Amazon, presenting pikes of occurrence and extension on 2005 and 2010. We show that fire occurs more frequently during these compound events than if these events occur independently. Moreover, an enhancement in fire intensity is also verified when HWs and drought occur simultaneously