Evaluating the SEVIRI Fire Thermal Anomaly Detection Algorithm across the Central African Republic Using the MODIS Active Fire Product

Satellite-based remote sensing of active fires is the only practical way to consistently and continuously monitor diurnal fluctuations in biomass burning from regional, to continental, to global scales. Failure to understand, quantify, and communicate the performance of an active fire detection algorithm, however, can lead to improper interpretations of the spatiotemporal distribution of biomass burning, and flawed estimates of fuel consumption and trace gas and aerosol emissions. This work evaluates the performance of the Spinning Enhanced Visible and Infrared Imager (SEVIRI) Fire Thermal Anomaly (FTA) detection algorithm using seven months of active fire pixels detected by the Moderate Resolution Imaging Spectroradiometer (MODIS) across the Central African Republic (CAR). Results indicate that the omission rate of the SEVIRI FTA detection algorithm relative to MODIS varies spatially across the CAR, ranging from 25% in the south to 74% in the east. In the absence of confounding artifacts such as sunglint, uncertainties in the background thermal characterization, and cloud cover, the regional variation in SEVIRI's omission rate can be attributed to a coupling between SEVIRI's low spatial resolution detection bias (i.e., the inability to detect fires below a certain size and intensity) and a strong geographic gradient in active fire characteristics across the CAR. SEVIRI's commission rate relative to MODIS increases from 9% when evaluated near MODIS nadir to 53% near the MODIS scene edges, indicating that SEVIRI errors of commission at the MODIS scene edges may not be false alarms but rather true fires that MODIS failed to detect as a result of larger pixel sizes at extreme MODIS scan angles. Results from this work are expected to facilitate (i) future improvements to the SEVIRI FTA detection algorithm; (ii) the assimilation of the SEVIRI and MODIS active fire products; and (iii) the potential inclusion of SEVIRI into a network of geostationary sensors designed to achieve global diurnal active fire monitoring.

Introduction to the BASIN Special Issue: State of art, past present a view to the future

Marine ecosystems are complex networks of organisms interacting either directly or indirectly while under the influence of the physical and chemical properties of the medium they inhabit. The interplay between these biological agents and their abiotic environment results in complex non-linear responses to individual and multiple stressors, influenced by feedbacks between these organisms and their environment. These ecosystems provide key services that benefit humanity such as food provisioning via the transfer of energy to exploited fish populations or climate regulation via the sinking, subsequent mineralization and ultimately storage of carbon in the ocean interior. These key characteristics or emergent features of marine ecosystems are subject to rapid change (e.g. regime shifts; Alheit et al., 2005 and Scheffer et al., 2009), with outcomes that are largely unpredictable in a deterministic sense. The North Atlantic Ocean is host to a number of such systems which are collectively being influenced by the unique physical and chemical features of this ocean basin, such as the Atlantic Meridional Overturning Circulation (AMOC), the basin’s ventilation with the Arctic Ocean, the dynamics of heat transport via the Gulf Stream and the formation of deep water at high latitudes. These features drive the solubility and biological pumps and support the production and environments that results in large exploited fish stocks. Our knowledge of its functioning as a coupled system, and in particular how it will respond to change, is still limited despite the scientific effort exerted over more than 100 years. This is due in part to the difficulty of providing synoptic overviews of a vast area, and to the fact that most fieldwork provides only snapshots of the complex physical, chemical and biological processes and their interactions. These constraints have in the past limited the development of a mechanistic understanding of the basin as a whole, and thus of the services it provides.

Challenges and difficulties in assessing the Environmental Status under the requirements of the Ecosystem Approach in North-African countries, illustrated by eutrophication assessment

Marine ecosystems provide many ecosystem goods and services. However, these ecosystems and the benefits they create for humans are subject to competing uses and increasing pressures. As a consequence of the increasing threats to the marine environment, several regulations require applying an ecosystem-based approach for managing the marine environment. Within the Mediterranean Sea, in 2008, the Contracting Parties of the Mediterranean Action Plan decided to progressively apply the Ecosystem Approach (EcAp) with the objective of achieving Good Environmental Status (GES) for 2018. To assess the Environmental Status, the EcAp proposes 11 Ecological Objectives, each of which requires a set of relevant indicators to be integrated. Progress towards the EcAp entails a gradual and important challenge for North-African countries, and efforts have to be initiated to propose and discuss methods. Accordingly, to enhance the capacity of North-African countries to implement EcAp and particularly to propose and discuss indicators and methods to assess GES, the aim of this manuscript is to identify the practical problems and gaps found at each stage of the Environmental Status assessment process. For this purpose, a stepwise method has been proposed to assess the Environmental Status using Ecologic Objective 5-Eutrophication as example.

Challenges and difficulties in assessing the Environmental Status under the requirements of the Ecosystem Approach in North-African countries, illustrated by eutrophication assessment

Marine ecosystems provide many ecosystem goods and services. However, these ecosystems and the benefits they create for humans are subject to competing uses and increasing pressures. As a consequence of the increasing threats to the marine environment, several regulations require applying an ecosystem-based approach for managing the marine environment. Within the Mediterranean Sea, in 2008, the Contracting Parties of the Mediterranean Action Plan decided to progressively apply the Ecosystem Approach (EcAp) with the objective of achieving Good Environmental Status (GES) for 2018. To assess the Environmental Status, the EcAp proposes 11 Ecological Objectives, each of which requires a set of relevant indicators to be integrated. Progress towards the EcAp entails a gradual and important challenge for North-African countries, and efforts have to be initiated to propose and discuss methods. Accordingly, to enhance the capacity of North-African countries to implement EcAp and particularly to propose and discuss indicators and methods to assess GES, the aim of this manuscript is to identify the practical problems and gaps found at each stage of the Environmental Status assessment process. For this purpose, a stepwise method has been proposed to assess the Environmental Status using Ecologic Objective 5-Eutrophication as example.