Global fire size distribution: from power law to log-normal

2016 ◽  
Vol 25 (4) ◽  
pp. 403 ◽  
Author(s):  
Stijn Hantson ◽  
Salvador Pueyo ◽  
Emilio Chuvieco
Keyword(s):  
Size Distribution ◽  
Frequency Distribution ◽  
Power Law ◽  
Likelihood Estimation ◽  
Fire Size ◽  
Chi Square ◽  
Size Frequency Distribution ◽  
Size Frequency ◽  
Fire Size Distribution ◽  
Log Normal

Wildland fires are one of the main alleged examples of Self-Organised Criticality (SOC), with simple SOC models resulting in the expectation of a power-law fire size frequency distribution. Here, we test whether fire size distributions systematically follow a power law and analyse their spatial variation for eight distinct areas over the globe. For each of the areas, we examine the fire size frequency distribution using two types of plots, maximum likelihood estimation and chi-square tests. Log-normal emerges as a suitable option to fit the fire size distribution in this variety of environments. In only two of eight areas was the power law (which is a particular case of the log-normal) not rejected. Notably, the two parameters of log-normal are related to each other, displaying a general linear relation, which extends to the sites that can be described with a power law. These results do not necessarily refute the SOC hypothesis, but reveal the presence of other processes that are, at least, modulating the outcome of SOC in some areas.

scholarly journals Blocks Size Frequency Distribution in the Enceladus Tiger Stripes Area: Implications on Their Formative Processes

Universe ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 82
Author(s):  
Maurizio Pajola ◽  
Alice Lucchetti ◽  
Lara Senter ◽  
Gabriele Cremonese
Keyword(s):  
Frequency Distribution ◽  
Power Law ◽  
Size Frequency Distribution ◽  
Surface Stresses ◽  
Size Frequency ◽  
The One ◽  
Power Law Index ◽  
Comet 67P ◽  
South Polar ◽  
Degree Of Fragmentation

We study the size frequency distribution of the blocks located in the deeply fractured, geologically active Enceladus South Polar Terrain with the aim to suggest their formative mechanisms. Through the Cassini ISS images, we identify ~17,000 blocks with sizes ranging from ~25 m to 366 m, and located at different distances from the Damascus, Baghdad and Cairo Sulci. On all counts and for both Damascus and Baghdad cases, the power-law fitting curve has an index that is similar to the one obtained on the deeply fractured, actively sublimating Hathor cliff on comet 67P/Churyumov-Gerasimenko, where several non-dislodged blocks are observed. This suggests that as for 67P, sublimation and surface stresses favor similar fractures development in the Enceladus icy matrix, hence resulting in comparable block disaggregation. A steeper power-law index for Cairo counts may suggest a higher degree of fragmentation, which could be the result of localized, stronger tectonic disruption of lithospheric ice. Eventually, we show that the smallest blocks identified are located from tens of m to 20–25 km from the Sulci fissures, while the largest blocks are found closer to the tiger stripes. This result supports the ejection hypothesis mechanism as the possible source of blocks.

An analysis of size frequency distribution of oil and gas reserves of Western Canada

1969 ◽  
Vol 6 (2) ◽  
pp. 201-211 ◽  
Author(s):  
R. G. McCrossan
Keyword(s):  
Frequency Distribution ◽  
Oil And Gas ◽  
Sufficient Information ◽  
Western Canada ◽  
Size Frequency Distribution ◽  
Normal Distributions ◽  
Size Frequency ◽  
Log Normal ◽  
The Individual ◽  
Normally Distributed

Both the oil and gas reserves of Western Canada are log-normally distributed. If the total reserves are separated into groups made up of single types of occurrence, these all display log-normal distributions as well. The parameters of the distributions vary considerably for different groups of genetically related accumulations. Many of the distributions also appear to be heterogeneous, showing distinct bimodality. Several hypotheses can be offered to explain this. For instance, the reserves of the group of smaller sized pools may be under-estimated for lack of sufficient information; secondly, geologically unlike types of pools may be grouped together. If the former is the case, an estimate can be made of the additional oil and gas in aggregate that may be undeveloped in the smaller under-estimated pools. The degree of bimodality may also indicate the maturity of an exploration play. Other possibilities are also considered. The distribution curves for the total reserves show only a generalized picture and obscure the characteristics of the individual distributions of the several types of oil or gas accumulations.

Assessing the power law hypothesis for the size–frequency distribution of terrestrial and martian dust devils

Icarus ◽  
2010 ◽  
Vol 209 (2) ◽  
pp. 851-853 ◽  
Author(s):  
A.V. Pathare ◽  
M.R. Balme ◽  
S.M. Metzger ◽  
A. Spiga ◽  
M.C. Towner ◽  
...  
Keyword(s):  
Frequency Distribution ◽  
Power Law ◽  
Dust Devils ◽  
Size Frequency Distribution ◽  
Size Frequency

Narrow size regime among individuals favors rapid growth in Arctic char (Salvelinus alpinus) juveniles

1999 ◽  
Vol 56 (10) ◽  
pp. 1891-1897 ◽  
Author(s):  
Teija Seppä ◽  
Nina Peuhkuri ◽  
Heikki Hirvonen ◽  
Anssi Laurila ◽  
Jorma Piironen ◽  
...  
Keyword(s):  
Size Distribution ◽  
Frequency Distribution ◽  
Salvelinus Alpinus ◽  
Growth Period ◽  
Arctic Char ◽  
Total Biomass ◽  
Narrow Size Distribution ◽  
Size Frequency Distribution ◽  
Size Regime ◽  
Size Frequency

We studied whether social environment in the form of different body size regimes in rearing groups affects the growth of juvenile Arctic char (Salvelinus alpinus) in hatchery conditions. Young-of-the-year Arctic char were divided into groups of three different compositions (a wide, a bimodal, and a narrow size-frequency distribution) in which individuals would be subjected to different dominance and competitive relationships. After a 9-month growth period the fish in the narrow size distribution had grown the fastest in both length and weight. Also, total biomass gains were highest for fish originating from the narrow size distribution treatment. The adjusted mean biomasses for wide, bimodal, and narrow size regime treatments were 5400, 5000, and 5900 g, respectively. Our results give support to the hypothesis that individuals in size-sorted groups should show enhanced growth compared with individuals originating from a wider size-frequency distribution where more aggressive interactions are to be expected.

On Determination of the Intensity and Size Frequency Distribution of Convective Vortices: Applications to Martian Dust Devils

2020 ◽  
Author(s):  
Michael Kurgansky
Keyword(s):  
Frequency Distribution ◽  
Power Law ◽  
Dust Devils ◽  
Size Frequency Distribution ◽  
Pressure Drops ◽  
Size Frequency ◽  
Pressure Time ◽  
Vortex Size ◽  
Convective Vortices

<p>Dust devils play a major role on Mars, providing a significant proportion of the total dust removal from the surface and its injection into the atmosphere, thus largely determining the overall radiative regime and the climatic state of the Martian atmosphere. The amount of dust lifted to the atmosphere by a population of dust devils is determined by the number density of dust devils (their number per unit area) and by their size-frequency and intensity-frequency distributions. Using the Abel transform, a two-step methodology has been developed to determine the marginal statistical distributions of convective vortices, including dust devils, on their intensity (pressure drop in the vortex center) and size (diameter), based on statistics of transient pressure drops recorded when the vortices pass near a pressure sensor placed on the surface of the planet. In a first step, if the pressure profile within the vortex is realistically modeled then the intensity-frequency distribution in the population of vortices can be inferred from the statistics of peak pressure drops recorded alone. If the observed statistics can be approximated with a truncated power-law distribution and in the absence of an apparent correlation between the vortex diameter and the maximum pressure drop at its center, then the measurements provide an unbiased power-law estimate of the actual intensity-frequency distribution. In a second step and in a practically important case when the distribution of vortices on their intensity follows the power law, the problem of determining the vortex size-frequency distribution is solved from data obtained in pressure time-series surveys. This two-step technique has been applied with success to Mars Science Laboratory (MSL) convective vortices.</p><p>This work was supported by the Presidium of the Russian Academy of Sciences, project no. 19-270. The method of inferring the vortex size-frequency distribution was developed with the support from the Russian Science Foundation (grant no. 18-77-10076).</p><p>References:</p><p>Kurgansky M.V. On the statistical distribution of pressure drops in convective vortices: Applications to Martian dust devils // Icarus. Volume 317, 1 January 2019, Pages 209-214. https://doi.org/10.1016/j.icarus.2018.08.004.</p><p>Kurgansky M.V. On determination of the size-frequency distribution of convective vortices in pressure time-series surveys on Mars // Icarus. Volume 335, 1 January 2020, 113389. https://doi.org/10.1016/j.icarus.2019.113389.</p>

Effects of Predation and Trophic Conditions on the Reproduction of Tylototriton verrucosus (Caudata: Salamandridae) in Darjeeling

2011 ◽  
Vol 4 (2) ◽  
pp. 163-169 ◽  
Author(s):  
Ritwik Dasgupta
Keyword(s):  
Frequency Distribution ◽  
Primary Productivity ◽  
Egg Size ◽  
Zooplankton Abundance ◽  
Trophic Conditions ◽  
Size Frequency Distribution ◽  
Size Frequency ◽  
High Predation ◽  
Hatchling Size ◽  
Predation Rates

The facts that small hatchlings emerged from small eggs laid under high predation levels prevailing at the lower altitudes of distribution of this species in Darjeeling while larger hatchlings emerged from larger eggs laid under lower levels of predation at higher altitudes, show that predation is not selected for large egg and initial hatchling size in this salamandrid species. Metamorphic size was small under high predation rates because this species relied on crypsis for evading predators. Egg and hatchling size are related inversely to levels of primary productivity and zooplankton abundance in lentic habitats. Hatchling sizes are related positively to egg size and size frequency distribution of zooplankton. Small egg and small hatchling size have been selected for at the lower altitudes of distribution of this salamandrid in Darjeeling because predation rates increased in step with improvement in trophic conditions at the lower altitudes.

SIZE FREQUENCY DISTRIBUTION BIASES IN HORSESHOE CRAB MOLT ASSEMBLAGES: IMPLICATIONS FOR THE FOSSIL RECORD

2016 ◽  
Author(s):  
Shelly J. Wernette ◽  
◽  
Scott Evans ◽  
Christine Hall ◽  
Mary L. Droser ◽  
...  
Keyword(s):  
Frequency Distribution ◽  
Fossil Record ◽  
Horseshoe Crab ◽  
Size Frequency Distribution ◽  
Size Frequency

scholarly journals A New Tool to Account for Crater Obliteration Effects in Crater Size-Frequency Distribution Measurements

2018 ◽  
Vol 5 (6) ◽  
pp. 258-267 ◽  
Author(s):  
Christian Riedel ◽  
Gregory Michael ◽  
Thomas Kneissl ◽  
Csilla Orgel ◽  
Harald Hiesinger ◽  
...  
Keyword(s):  
Frequency Distribution ◽  
Size Frequency Distribution ◽  
Crater Size ◽  
Size Frequency
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