Weather conditions and warm air masses during active fire-periods in boreal forests

Hayasaka, Hiroshi; Yamazaki, Koji; Naito, Daisuke

doi:10.1016/j.polar.2019.07.002

Cited by 25 publications

(37 citation statements)

References 23 publications

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“…3). This was consistent with the observation that subsidence of the air is higher at the ridge edges, leading to more severe fire conditions through higher rates of fuel drying and stronger surface winds, both promoting fire spread (Fauria and Johnson, 2006;Hayasaka et al, 2019) and possibly also lightning activity (Price, 2009). We did not reveal a century-long trend in the synchrony of LFY occurrence across EBZ and, similarly, no trend was visible for the MDC values indicative of the periods with strong fire hazard (Fig.…”

Section: Regional Patterns Of Fire Activity Within Ebz and Its Climatic Controlssupporting

confidence: 88%

Trends and patterns in annually burned forest areas and fire weather across the European boreal zone in the 20th and early 21st centuries

Drobyshev¹,

Kitenberga²,

Ryzhkova³

et al. 2020

Preprint

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Fire remains the main natural disturbance factor in the European boreal zone (EBZ), which exhibits strong gradients in climate conditions, modern and historical patterns of forest use, and the modern human infrastructure density. Understanding climatic forcing on fire activity is important for projecting effects of climate change on multiple ecosystem services in this region. Here we analyzed available records of annually burned areas (ABA) in 16 administrative regions of EBZ (countries or sub-country units) and fire weather variability to test for their spatio-temporal patterns over 1901-2017. To define sub-regions of EBZ with similar fire activity we compiled 30-60 year long ABA chronologies and clustered them in Euclidian space to identify regions of EBZ with temporally synchronous fire activity. We then reconstructed 100-year long ABA chronologies for each cluster, capitalizing on its member with the highest correlation between observational fire record and climatological fire weather proxy (MDC, monthly drought code). The 100-year chronologies helped identified large fire years (LFY), i.e. years with the ABA being above 10% of its long-term distribution. The climatic forcing of these events was tested in superposed epoch analysis operated with gridded 500 hPa pressure fields. Finally, we tested trends in (a) synchrony of LFY's across clusters, (b) MDC values over the EBZ, and (c) spatial variability in July MDC over the EBZ geographic domain during 1901-2017.EBZ exhibits large variability in forest fire activity with the fire cycles varying from ~104 (Scandinavia) to 3*102 years (Russian Republic of Komi). Clustering of administrative units in respect to their ABA suggested the presence of sub-regions with synchronous dynamics of ABA, located&#160; along W-E and S-N gradients. LFYs in each of the cluster was associated with the development of the high pressure cell over the regions in question in July, indicating climatic forcing of LFYs. Contingency analysis indicated no long-term trend in the synchrony of LFYs observed simultaneously in several administrative units. We observed a trend towards higher values of MDC for the months of April and May in the western section of EBZ (April) and southern-eastern sections of the Baltic sea region and North sections of EBZ in Russia (May). Trends in MDC during the summer months were largely absent. We discuss teleconnections of fire activity in the EBZ with Atlantic SST.

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Section: Regional Patterns Of Fire Activity Within Ebz and Its Climatic Controlssupporting

confidence: 88%

Trends and patterns in annually burned forest areas and fire weather across the European boreal zone in the 20th and early 21st centuries

Drobyshev¹,

Kitenberga²,

Ryzhkova³

et al. 2020

Preprint

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“…Subsequently, we performed a daily fire analysis using daily hotspot (HS) data and weather maps, including temperature and wind, to understand fire weather during the active fire-period in eastern Siberia and Alaska. Our analysis results [26][27][28] clearly showed that fires during all active-fire periods became very active as warm air masses (cTe: continental temperate [29]) from the south approached the four study regions. These movements of warm air masses were mainly related to the meandering of large westerlies.…”

Section: Introductionmentioning

confidence: 99%

“…These movements of warm air masses were mainly related to the meandering of large westerlies. Strong wind conditions occurred when warm and dry air masses were approaching, stagnating, and passing over southern Sakha under various weather conditions at lower air level [26][27][28].…”

Section: Introductionmentioning

confidence: 99%

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Rare and Extreme Wildland Fire in Sakha in 2021

Hayasaka

2021

Atmosphere

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A large-scale wildland fire occurred in Sakha in 2021. The results of fire analysis showed that the total number of hotspots in 2021 exceeded 267,000. This is about 5.8 times the average number of fires over the last 19 years since 2002. The largest daily number of hotspots in 2021 was 16,226, detected on 2 August. On 7 August, about half of the daily hotspots (52.6% = 8175/15,537 × 100) were detected in a highest fire density area (HFA, 62.5–65° N, 125–130° E) near Yakutsk under strong southeasterly wind (wind velocity about 12 m/s (43 km/h)). The results of weather analysis using various weather maps are as follows: The large meandering westerlies due to stagnant low-pressure systems in the Barents Sea brought high-pressure systems and warm air masses from the south to high latitudes, creating warm, dry conditions that are favorable conditions for fire. In addition to these, strong southeasterly winds at lower air levels blew which were related to the development of high-pressure systems in the Arctic Ocean. The HFA was located in the strong wind region (>8 m/s) of the v-wind map. The record-breaking Sakha fire season of 2021 is an example of extreme phenomena wrought by rapid climate change.

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“…This is facilitated by an increase in the average annual air temperature and duration of growing season [2], an increase in frequency and intensity of weather anomalies associated with global climate change [3], affecting on natural physical environment and vegetation cover [4]. In this aspect, a very useful role in terms of preventing active fires is played by the developments of researchers based on information the detection of active hotspots from MODIS time-series dataset of low resolution (Terra and Aqua satellites) [5]. A new approach to predictive assessment of fires [6] is based on a comprehensive analysis of data on detection of hotspots and baric topography maps at levels 925, 850, and 500 hPa, constructed from NCEP and NCAR reanalysis data [7].…”

Section: Introductionmentioning

confidence: 99%

Hydrological consequences of changes forest cover on watersheds of the Amur river basin

2020

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Observing the geographic environment change of watersheds is very important for understanding problem of influence on streamflow, which ranks fourth out of 23 hydrological problems highlighted at Vienna Catchment Science Symposium in April 2018. Watersheds of the Middle and Lower Amur, where main part of streamflow is formed, are covered with forests of various structures. Annual forest fires in the Amur basin lead to sharp decrease in transpiration and summarize evaporation, an increase in volume and rate of surface streamflow (slope) into river beds and, as a consequence an increase in river runoff. An increase frequency of fires entails a change in forest species composition. Despite fact that species of the stand within watershed grow up in same conditions (environment, climate, weather, fires) – total value of the areas of coniferous forests has a decrease, in contrast to deciduous species. This is consistent with the conclusions of Russian hydrologists about shift in Russia of the boundaries of middle taiga on north, which is justified by them using climatic models. Reduction of coniferous forests, which have a deeper root system and larger area of contact with atmospheric precipitation, contributes to a faster runoff of rainwater, contributing an increase streamflow. Moreover, a positive trend is also noted in synchronous dynamics of peaks of rain floods on the Amur near Khabarovsk. This corresponds to assessment of spatio-temporal variations of global terrestrial water storage changes of the Amur according measurements of the Earth’s gravitational fields by GRACE satellite, carried out by foreign researchers. It has been suggested that with a descending trend in areas of coniferous forests, conditions will persist, contributing to increase in streamflow during the period of monsoon and frontal cyclonic rains.

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Weather conditions and warm air masses during active fire-periods in boreal forests

Cited by 25 publications

References 23 publications

Trends and patterns in annually burned forest areas and fire weather across the European boreal zone in the 20th and early 21st centuries

Trends and patterns in annually burned forest areas and fire weather across the European boreal zone in the 20th and early 21st centuries

Rare and Extreme Wildland Fire in Sakha in 2021

Hydrological consequences of changes forest cover on watersheds of the Amur river basin

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