53 research outputs found
The Prelude to the Deep Minimum between Solar Cycles 23 and 24: Interplanetary Scintillation Signatures in the Inner Heliosphere
Extensive interplanetary scintillation (IPS) observations at 327 MHz obtained
between 1983 and 2009 clearly show a steady and significant drop in the
turbulence levels in the entire inner heliosphere starting from around ~1995.
We believe that this large-scale IPS signature, in the inner heliosphere,
coupled with the fact that solar polar fields have also been declining since
~1995, provide a consistent result showing that the buildup to the deepest
minimum in 100 years actually began more than a decade earlier.Comment: 9 pages, 4 figures, accepted for publication in Geophysical Research
Letters on 28 September 201
Thresholds of fire response to moisture and fuel load differ between tropical savannas and grasslands across continents
Aim An emerging framework for tropical ecosystems states that fire activity is either âfuel buildâup limitedâ or âfuel moisture limitedâ, that is, as you move up along rainfall gradients, the major control on fire occurrence switches from being the amount of fuel, to the moisture content of the fuel. Here we used remotely sensed datasets to assess whether interannual variability of burned area is better explained by annual rainfall totals driving fuel buildâup, or by dry season rainfall driving fuel moisture. Location Pantropical savannas and grasslands. Time period 2002â2016. Methods We explored the response of annual burned area to interannual variability in rainfall. We compared several linear models to understand how fuel moisture and fuel buildâup effect (accumulated rainfall during 6 and 24 months prior to the end of the burning season, respectively) determine the interannual variability of burned area and explore if tree cover, dry season duration and human activity modified these relationships. Results Fuel and moisture controls on fire occurrence in tropical savannas varied across continents. Only 24% of South American savannas were fuel buildâup limited against 61% of Australian savannas and 47% of African savannas. On average, South America switched from fuel limited to moisture limited at 500 mm/year, Africa at 800 mm/year and Australia at 1,000 mm/year of mean annual rainfall. Main conclusions In 42% of tropical savannas (accounting for 41% of current area burned) increased drought and higher temperatures will not increase fire, but there are savannas, particularly in South America, that are likely to become more flammable with increasing temperatures. These findings highlight that we cannot transfer knowledge of fire responses to global change across ecosystems/regionsâlocal solutions to local fire management issues are required, and different tropical savanna regions may show contrasting responses to the same drivers of global change
Probabilistic fire spread forecast as a management tool in an operational setting
Background: An approach to predict fire growth in an operational setting, with the
potential to be used as a decision-support tool for fire management, is described and
evaluated. The operational use of fire behaviour models has mostly followed a deterministic
approach, however, the uncertainty associated with model predictions needs
to be quantified and included in wildfire planning and decision-making process during
fire suppression activities. We use FARSITE to simulate the growth of a large wildfire.
Probabilistic simulations of fire spread are performed, accounting for the uncertainty
of some model inputs and parameters. Deterministic simulations were performed for
comparison. We also assess the degree to which fire spread modelling and satellite
active fire data can be combined, to forecast fire spread during large wildfires events.
Results: Uncertainty was propagated through the FARSITE fire spread modelling system
by randomly defining 100 different combinations of the independent input variables
and parameters, and running the correspondent fire spread simulations in order
to produce fire spread probability maps. Simulations were initialized with the reported
ignition location and with satellite active fires. The probabilistic fire spread predictions
show great potential to be used as a fire management tool in an operational setting,
providing valuable information regarding the spatialâtemporal distribution of burn
probabilities. The advantage of probabilistic over deterministic simulations is clear
when both are compared. Re-initializing simulations with satellite active fires did not
improve simulations as expected.
Conclusion: This information can be useful to anticipate the growth of wildfires
through the landscape with an associated probability of occurrence. The additional
information regarding when, where and with what probability the fire might be in the
next few hours can ultimately help minimize the negative environmental, social and
economic impacts of these firesinfo:eu-repo/semantics/publishedVersio
Global percent tree cover at a spatial resolution of 500 meters: first results of the MODIS vegetation continuous fields algorithm
ABSTRACT: The first results of the Moderate Resolution Imaging Spectroradiometer (MODIS) vegetation continuous field algorithmâs global percent tree cover are presented. Percent tree cover per 500-m MODIS pixel i
The recipe for being a good military wife: how military wives managed OIF/OEF deployment
Interviews with 25 military wives to elicit their lived experience of OIF/OEF deployment found two main themes: the recipe for being a good military wife and managing split loyalties. Military wivesâ experience reflected a disenfranchised existence. Their stress was exacerbated by the reality of the composition of their marital relationship -- a couple-military threesome -- that they bore in silence. Their marginalization did not deter them from supporting their husbands the best they could, reflecting their inherent strength and resilience. The wives had a recipe that helped them manage the stresses inherent in deployment. Research and clinical implications are discussed
Development of an Operational Land Water Mask for MODIS Collection 6, and Influence on Downstream Data Products
Data from the Moderate Resolution Imaging Spectro-radiometer (MODIS)on-board the Earth Observing System Terra and Aqua satellites are processed using a land water mask to determine when an algorithm no longer needs to be run or when an algorithm needs to follow a different pathway. Entering the fourth reprocessing (Collection 6 (C6)) the MODIS team replaced the 1 km water mask with a 500 m water mask for improved representation of the continental surfaces. The new water mask represents more small water bodies for an overall increase in water surface from 1 to 2 of the continental surface. While this is still a small fraction of the overall global surface area the increase is more dramatic in certain areas such as the Arctic and Boreal regions where there are dramatic increases in water surface area in the new mask. MODIS products generated by the on-going C6 reprocessing using the new land water mask show significant impact in areas with high concentrations of change in the land water mask. Here differences between the Collection 5 (C5) and C6 water masks and the impact of these differences on the MOD04 aerosol product and the MOD11 land surface temperature product are shown
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