This study analyzes the forest flammability hazard in the south of Tyumen Oblast (Western Siberia, Russia) and identifies variation patterns in fire areas depending on weather and climate characteristics in 2008-2023. Using correlation analysis, we proved that the area of forest fires is primarily affected by maximum temperature, relative air humidity, and the amount of precipitation, as well as by global climate change associated with an increase in carbon dioxide in the atmosphere and the maximum height of snow cover. As a rule, a year before the period of severe forest fires in the south of Tyumen Oblast, the height of snow cover is insignificant, which leads to insufficient soil moisture in the following spring, less or no time for the vegetation to enter the vegetative phase, and the forest leaf floor remaining dry and easily flammable, which contributes to an increase in the fire area. According to the estimates of the CMIP6 project climate models under the SSP2-4.5 scenario, by the end of the 21st century, a gradual increase in the number of summer temperatures above 35 degrees C is expected, whereas the extreme SSP5-8.5 scenario forecasts the tripling in the number of such hot days. The forecast shows an increase of fire hazardous conditions in the south of Tyumen Oblast by the late 21st century, which should be taken into account in the territory's economic development.

The frequency of forest fires has increased dramatically due to climate change. The occurrence of forest fires affects the carbon and nitrogen cycles and react to climate change to form a positive feedback mechanism. These effects further impact the distribution of microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) and the soil microbial community structure. In addition, permafrost degradation can significantly affect the microorganisms in the soil. Based on these findings, this review examines the effects of fire intensity and post-fire recovery time on permafrost, the soil microbial community, MBC, MBN, and their interrelationships. This review demonstrated that (1) fires alter the condition of surface vegetation, reduce the organic layer thickness, redistribute snow, accelerate permafrost degradation, and even lead to permanent changes, where the restoration of the pre-fire state would require several decades or even centuries; (2) soil microbial community structure, soil MBC, and MBN negatively correlate with fire intensity, and the effects become more pronounced with increasing fire intensity; and (3) the structural diversity and stability of the soil microbial community were improved with time, and the amount of MBC and MBN increases as the years after a fire go by; it would still take more than ten years to recover to the pre-fire level. However, the relationship between permafrost degradation and soil microbes after forest fires is still unclear due to a lack of quantitative research on the mechanisms underlying the changes in soil microorganisms resulting from fire-induced permafrost degradation. Therefore, expanding quantitative studies and analyses of the mechanisms of interactions between forest fires, permafrost, and soil microorganisms can provide a scientific basis for understanding ecosystem carbon pools and dual-carbon targets in Arctic-boreal permafrost regions.

According to the monitoring data of the optical and microphysical characteristics of smoke aerosol at AERONET stations during forest fires in the summer of 2019 in Alaska, the anomalous selective absorption of smoke aerosol has been detected in the visible and near-infrared spectral range from 440 to 1020 nm. With anomalous selective absorption, the imaginary part of the refractive index of smoke aerosol reached 0.315 at a wavelength of 1020 nm. A power-law approximation of the spectral dependence of the imaginary part of the refractive index with an exponent from 0.26 to 2.35 is proposed. It is shown that, for anomalous selective absorption, power-law approximations of the spectral dependences of the aerosol optical extinction and absorption depths are applicable with an angstrom ngstrom exponent from 0.96 to 1.65 for the aerosol optical extinction depth and from 0.97 to -0.89 for the aerosol optical absorption depth, which reached 0.72. Single scattering albedo varied from 0.62 to 0.96. In the size distribution of smoke aerosol particles with anomalous selective absorption, the fine fraction of particles of condensation origin dominated. The similarity of the fraction of particles distinguished by anomalous selective absorption with the fraction of tar balls (TBs) detected by electron microscopy in smoke aerosol, which, apparently, arise during the condensation of terpenes and their oxygen-containing derivatives, is noted.

Throughout the larch range, warming leads to frequent fires and an increase in burned areas. We test the hypothesis that fires are an essential natural factor that reset larch regeneration and support the existence of larch forests. The study area included Larix sibirica and L. gmelinii ranges within the permafrost zone. We used satellite-derived and field data, dendrochronology, and climate variables analysis. We found that warming led to an increase in fire frequency and intensity, mean, and extreme (>10,000 ha) burned areas. The burned area is increasing in the northward direction, while fire frequency is decreasing. The fire rate exponentially increases with decreasing soil moisture and increasing air temperature and air drought. We found a contrasting effect of wildfire on regeneration within continuous permafrost and within the southern lowland boundary of the larch range. In the first case, burnt areas regenerated via abounded larch seedlings (up to 500,000+ per ha), whereas the south burns regenerated mostly via broadleaf species or turned into grass communities. After the fire, vegetation GPP was restored to pre-fire levels within 3-15 years, which may indicate that larch forests continue to serve as carbon stock. At the southern edge of the larch range, an amplified fire rate led to the transformation of larch forests into grass and shrub communities. We suggested that the thawing of continuous permafrost would lead to shrinking larch-dominance in the south. Data obtained indicated that recurrent fires are a prerequisite for larch forests' successful regeneration and resilience within continuous permafrost. It is therefore not necessary to suppress all fires within the zone of larch dominance. Instead, we must focus fire suppression on areas of high natural, social, and economic importance, permitting fires to burn in vast, larch-dominant permafrost landscapes.

The work is devoted to the study of the climatic effects of black carbon (BC) transferred from forest fires to the Arctic zone. The HYSPLIT (The Hybrid Single-Particle Lagrangian Integrated Trajectory model) trajectory model was used to initially assess the potential for particle transport from fires. The results of the trajectory analysis of the 2019 fires showed that the probability of the transfer of particles to the Arctic ranges from 1% to 10%, and in some cases increases to 20%. Detailed studies of the possible influence of BC ejected as a result of fires became possible by using the climate model of the INMCM5 (Institute of Numerical Mathematics Climate Model). The results of the numerical experiments have shown that the maximum concentration of BC in the Arctic atmosphere is observed in July and August and is associated with emissions from fires. The deposition of BC in the Arctic increases by about 1.5-2 times in the same months, in comparison with simulation without forest fire emissions. This caused an average decrease in solar radiation forcing of 0.3-0.4 Wt/m(2) and an increase in atmospheric radiation heating of up to 5-6 Wt/m(2). To assess the radiation forcing from BC contaminated snow, we used the dependences of the change in the snow albedo on the snow depth, and the albedo of the underlying surface for a given amount of BC fallen on the snow. These dependences were constructed on the basis of the SNICAR (Snow, Ice, and Aerosol Radiative) model. According to our calculations, the direct radiative forcing from BC in the atmosphere with a clear sky is a maximum of 4-5 W/m(2) in July and August.

In boreal and arctic regions, forest fires exert great influences on biogeochemical processes, hydrothermal dynamics of the active layer and near-surface permafrost, and subsequent nutrient cycles. In this article, the studies on impacts of forest fires on the permafrost environment are reviewed. These studies indicate that forest fires could result in an irreversible degradation of permafrost, successions of boreal forests, rapid losses of soil carbon stock, and increased hazardous periglacial landforms. After forest fires, soil temperatures rise; active layer thickens; the release of soil carbon and nitrogen enhances, and; vegetation changes from coniferous forests to broad-leaved forests, shrublands or grasslands. It may take decades or even centuries for the fire-disturbed ecosystems and permafrost environment to return to pre-fire conditions, if ever possible. In boreal forest, the thickness of organic layer has a key influence on changes in permafrost and vegetation. In addition, climate warming, change of vegetation, shortening of fire return intervals, and extent of fire range and increasing of fire severity may all modify the change trajectory of the fire-impacted permafrost environment. However, the observations and research on the relationships and interactive mechanisms among the forest fires, vegetation, carbon cycle and permafrost under a changing climate are still inadequate for a systematic impact evaluation. Using the chronosequence approach of evaluating the temporal changes by measuring changes in the permafrost environment at different stages at various sites (possibly representing varied stages of permafrost degradation and modes), multi-source data assimilation and model predictions and simulations should be integrated with the results from long- and short-term field investigations, geophysical investigations and airborne surveys, laboratory testing and remote sensing. Future studies may enable quantitatively assess and predict the feed-back relationship and influence mechanism among organic layer, permafrost and active layer processes, vegetation and soil carbon under a warming climate at desired spatial and temporal scales. The irreversible changes in the boreal and artic forest ecosystem and their ecological and hydrothermal thresholds, such as those induced by forest fires, should be better and systematically studied.

Forest fires have significantly impacted the permafrost environment, and many research programs looking at this have been undertaken at higher latitudes. However, their impacts have not yet been systematically studied and evaluated in the northern part of northeast China at mid-latitudes. This study simultaneously measured ecological and geocryological changes at various sites in the boreal forest at different stages after forest fires (chronosequence approach) in the northern Da Xing'anling (Hinggan) Mountains, Northeast China. We obtained results through field investigations, monitoring and observations, remote sensing interpretations, and laboratory tests. The results show that forest fires have resulted in a decreased Normalized Difference Vegetation Index (NDVI) and soil moisture contents in the active layer, increased active layer thickness (ALT) and ground temperatures, and the release of a large amount of C and N from the soils in the active layer and at shallow depths of permafrost. NDVI and species biodiversity have gradually increased in the years since forest fires. However, the vegetation has not fully recovered to the climax community structures and functions of the boreal forest ecosystems. For example, ground temperatures, ALT, and soil C and N contents have been slowly recovering in the 30years after the forest fires, but they have not yet been restored to pre-fire levels. This study provides important scientific bases for assessment of the impacts of forest fires on the boreal forest ecosystems in permafrost regions, environmental restoration and management, and changes in the carbon stock of soils at shallow (<3m) depths in the Da Xingan'ling Mountains in northeast China.

The purpose of this work is to obtain estimates of the probability of black carbon transfer originated from simulated forest fires in European and Asian boreal taiga to Arctic region, to assess its concentration and deposition to ice surface and its contribution to shortwave radiative forcing. To obtain a primary qualitative estimate of the transfer possibility of particles from forest fires in Russia to the area covered with sea ice, the trajectory model HYSPLIT was used. The climatic impact of black carbon on the Arctic from simulated forest fires was estimated using a climate model developed by the Institute of Numerical Mathematics (INMCM4) of the Russian Academy of Sciences. It was shown that the probability that the particle injected in northern Russia in the area of boreal taiga, would move through areas of the Arctic Ocean covered with sea ice, is estimated to be in the range 1-10%. The impact of the black carbon on the balance of shortwave radiation was estimated: an increase of 1.5-2% compared with the no-emission scenario.

Atmospheric aerosols are important aspects of climate research due to their impact on radiative forcing. In the present study, the aerosol optical depth (ADD), the Angstrom exponent (alpha) and the single scattering albedo (SSA) over the urban region of Hyderabad, India, were examined using Sun/Sky radiometer measurements during January-December, 2008. AOD showed higher values on certain Julian days coinciding with the occurrence of wintertime dust storm events in the Gulf Region and biomass burning due to forest fires over Indian Region. The AOD values during wintertime dust event are about similar to 55% higher than those on normal days. The SSAs show positive and negative trends in alpha (R-2 = 0.71) and black carbon (BC) aerosols (R-2 = 0.44), respectively. The aerosol size distribution shows a bimodal pattern with fine (similar to 0.15 mu m) and coarse (similar to>7 mu m) mode during January-December, 2008. The MODIS AOD showed positive correlation with sky radiometer-derived AOD values (R-2 = 0.68). (C) 2011 Elsevier B.V. All rights reserved.

Forest fires are frequent in the Siberian taiga and are predicted to increase in frequency as a result of increased fire risk under drought conditions, and prolonged fire seasons caused by climate change. There is, however, some uncertainty as to the extent to which drought influences forest fire frequency at a regional scale. Here, we present an analysis of satellite derived soil moisture anomaly data from ERS-1/2 (ERS: Earth Resources Satellite) scatterometer data and burned area maps from MODIS/AVHRR/ATSR (Moderate Resolution Imaging Spectroradiometer/Advanced Very High Resolution Radiometer/Along-Track Scanning Radiometer) over Central Siberia for the years 1992-2000. The purpose of this study is to investigate the relationship of remotely sensed soil moisture deviations from the long-term mean and fire within the boreal biome on a sub-continental scale. Results show that wet surface soil moisture conditions limit the extent of burned area. They can prevent the outbreak of fires but the magnitude of a negative (dry) deviation does not determine the maximum size of fire affected areas. It is known from the literature, however, that an ignition is more likely to occur under low surface wetness conditions, such as those that we observed during July and August in both permafrost and non-permafrost regions. Although the burned area under drier conditions in July is lowest over non-permafrost, the actual number of fires is as high as over continuous permafrost. Approximately 80% of all events occurred under such conditions during that month. The fire size was below 50 km(2) under moist conditions. Larger burned areas have in general not been detected when the surface wetness deviation exceeded +5%.