Understanding atmospheric organic aerosols via factor analysis of aerosol mass spectrometry: a review

Organic species are an important but poorly characterized constituent of airborne particulate matter. A quantitative understanding of the organic fraction of particles (organic aerosol, OA) is necessary to reduce some of the largest uncertainties that confound the assessment of the radiative forcing of climate and air quality management policies. In recent years, aerosol mass spectrometry has been increasingly relied upon for highly time-resolved characterization of OA chemistry and for elucidation of aerosol sources and lifecycle processes. Aerodyne aerosol mass spectrometers (AMS) are particularly widely used, because of their ability to quantitatively characterize the size-resolved composition of submicron particles (PM1). AMS report the bulk composition and temporal variations of OA in the form of ensemble mass spectra (MS) acquired over short time intervals. Because each MS represents the linear superposition of the spectra of individual components weighed by their concentrations, multivariate factor analysis of the MS matrix has proved effective at retrieving OA factors that offer a quantitative and simplified description of the thousands of individual organic species. The sum of the factors accounts for nearly 100% of the OA mass and each individual factor typically corresponds to a large group of OA constituents with similar chemical composition and temporal behavior that are characteristic of different sources and/or atmospheric processes. The application of this technique in aerosol mass spectrometry has grown rapidly in the last six years. Here we review multivariate factor analysis techniques applied to AMS and other aerosol mass spectrometers, and summarize key findings from field observations. Results that provide valuable information about aerosol sources and, in particular, secondary OA evolution on regional and global scales are highlighted. Advanced methods, for example a-priori constraints on factor mass spectra and the application of factor analysis to combined aerosol and gas phase data are discussed. Integrated analysis of worldwide OA factors is used to present a holistic regional and global description of OA. Finally, different ways in which OA factors can constrain global and regional models are discussed

Transforming fire suppression into an intercultural and participative fire management policy in Canaima National Park, Venezuela. A learning together and Indigenous, academic and institutional knowledge integration process

Canaima National Park (CNP, Venezuela), located in the core of Guiana Shield and inhabited by the Pemón indigenous people, is an area of great value due to its biological and cultural singularity. High incidence of fires, together with increased forest vulnerability to fire as a result of global climate and socio-environmental changes, have been considered threats, since they could put at risk, both ecosystems and human well-being. The conflict over fire use is exacerbated by the fact that whereas the Pemón depend for their livelihood on the use of fire, the policy of CNP government agencies has been fire exclusion (although this is not effectively enforced). The aim of this work is to present the experience gained during the development, for almost 20 years, of three participative and trans-disciplinary research-action areas: 1) long-term indigenous, fire-fighters and scientists collaborative fire experiments to study fire behavior and effects on bio-geo-chemical cycles and biodiversity; 2) facilitation of the process of collection, systematization and transmission of ancestral knowledge inside the very same Pemón Indigenous communities, regarding to the origin, use and fire management techniques, and 3) articulation of knowledge and experiences for the formulation of a legitimate intercultural fire management policy, and the participation of different actors involved in the socio-ecological issues of the Park (Indigenous people, environmental managers, fire-fighters, academics, etc.). Our results reveal a sophisticated Indigenous knowledge system about the use of fire for the main subsistence activities, especially shifting cultivation, and collaborative burning practices in savanna-forests borders to protect forest from catastrophic wildfires. Furthermore, ecological studies showed fire exclusion promotes "megafires" by accumulation of fuel material enhanced by current drier and hotter climatic conditions. Thus, through the development of a systemic approach, based on learning together and long-term cooperative fire experiments with Pemón Indigenous communities, forest fire-fighters and the collaboration and exchange of different stakeholders, a shift of the fire paradigm was successfully negotiated that valorise the relevance of Pemón millenary culture for a sustainable resources management as well as adaptation to climate change

The High Resolution Imaging Science Experiment (HiRISE) during MRO’s Primary Science Phase (PSP)

The High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter (MRO) acquired 8 terapixels of data in 9137 images of Mars between October 2006 and December 2008, covering ~0.55% of the surface. Images are typically 5–6 km wide with 3-color coverage over the central 20% of the swath, and their scales usually range from 25 to 60 cm/pixel. Nine hundred and sixty stereo pairs were acquired and more than 50 digital terrain models (DTMs) completed; these data have led to some of the most significant science results. New methods to measure and correct distortions due to pointing jitter facilitate topographic and change-detection studies at sub-meter scales. Recent results address Noachian bedrock stratigraphy, fluvially deposited fans in craters and in or near Valles Marineris, groundwater flow in fractures and porous media, quasi-periodic layering in polar and non-polar deposits, tectonic history of west Candor Chasma, geometry of clay-rich deposits near and within Mawrth Vallis, dynamics of flood lavas in the Cerberus Palus region, evidence for pyroclastic deposits, columnar jointing in lava flows, recent collapse pits, evidence for water in well-preserved impact craters, newly discovered large rayed craters, and glacial and periglacial processes. Of particular interest are ongoing processes such as those driven by the wind, impact cratering, avalanches of dust and/or frost, relatively bright deposits on steep gullied slopes, and the dynamic seasonal processes over polar regions. HiRISE has acquired hundreds of large images of past, present and potential future landing sites and has contributed to scientific and engineering studies of those sites. Warming the focal-plane electronics prior to imaging has mitigated an instrument anomaly that produces bad data under cold operating conditions