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.

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.

Ocean acidification has different effects on the production of DMS and DMSP measured in cultures of Emiliania huxleyi and a mesocosm study: a comparison of laboratory monocultures and community interactions

The human-induced rise in atmospheric carbon dioxide since the industrial revolution has led to increasing oceanic carbon uptake and changes in seawater carbonate chemistry, resulting in lowering of surface water pH. In this study we investigated the effect of increasing CO2 partial pressure (pCO2) on concentrations of volatile biogenic dimethylsulfide (DMS) and its precursor dimethylsulfoniopropionate (DMSP), through monoculture studies and community pCO2 perturbation. DMS is a climatically important gas produced by many marine algae: it transfers sulfur into the atmosphere and is a major influence on biogeochemical climate regulation through breakdown to sulfate and formation of subsequent cloud condensation nuclei (CCN). Overall, production of DMS and DMSP by the coccolithophore Emiliania huxleyi strain RCC1229 was unaffected by growth at 900 matm pCO2, but DMSP production normalised to cell volume was 12% lower at the higher pCO2 treatment. These cultures were compared with community DMS and DMSP production during an elevated pCO2 mesocosm experiment with the aim of studying E. huxleyi in the natural environment. Results contrasted with the culture experiments and showed reductions in community DMS and DMSP concentrations of up to 60 and 32% respectively at pCO2 up to 3000 matm, with changes attributed to poorer growth of DMSP-producing nanophytoplankton species, including E. huxleyi, and potentially increased microbial consumption of DMSand dissolvedDMSPat higher pCO2.DMSandDMSPproduction differences between culture and community likely arise from pH affecting the inter-species responses between microbial producers and consumers.