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- Wang, Sifan, et al.
(författare)
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Fire carbon emissions over Equatorial Asia reduced by shortened dry seasons
- 2023
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Ingår i: npj Climate and Atmospheric Science. - 2397-3722. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- Fire carbon emissions over Equatorial Asia (EQAS) play a critical role in the global carbon cycle. Most regional fire emissions (89.0%) occur in the dry season, but how changes in the dry-season length affect the fire emissions remains poorly understood. Here we show that, the length of the EQAS dry season has decreased significantly during 1979–2021, and the delayed dry season onset (5.4 ± 1.6 (± one standard error) days decade−1) due to increased precipitation (36.4 ± 9.1 mm decade−1) in the early dry season is the main reason. The dry season length is strongly correlated with the length of the fire season. Increased precipitation during the early dry season led to a significant reduction (May: −0.7 ± 0.4 Tg C decade−1; August: −12.9 ± 6.7 Tg C decade−1) in fire carbon emissions during the early and peak fire season. Climate models from the Coupled Model Intercomparison Project Phase 6 project a continued decline in future dry season length in EQAS under medium and high-emission scenarios, implying further reductions in fire carbon emissions.
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| 2. |
- Tang, R., et al.
(författare)
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Increasing terrestrial ecosystem carbon release in response to autumn cooling and warming
- 2022
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Ingår i: Nature Climate Change. - : Springer Science and Business Media LLC. - 1758-678X .- 1758-6798. ; 12, s. 380-385
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Tidskriftsartikel (refereegranskat)abstract
- Despite overall warming, many regions in the Northern Hemisphere have been cooling in autumn. This cooling resulted in an increasing release of net CO2 2004-2018 as primary production decreased more than respiration in cooling and respiration increased more than production in warming areas. Part of the Northern Hemisphere has experienced widespread autumn cooling during the most recent decades despite overall warming, but how this contrasting temperature change has influenced the ecosystem carbon exchange remains unclear. Here, we show that autumn cooling has occurred over about half of the area north of 25 degrees N since 2004, producing a weak cooling trend over the period 2004-2018. Multiple lines of evidence suggest an increasing net CO2 release in autumn during 2004-2018. In cooling areas, the increasing autumn CO2 release is due to the larger decrease of gross primary productivity (GPP) growth than total ecosystem respiration (TER) growth suppressed by cooling. In the warming areas, TER increased more than GPP because the warming and wetting conditions are more favourable for TER growth than GPP increase. Despite the opposite temperature trends, there has been a systematic increase in ecosystem carbon release across the Northern Hemisphere middle and high latitudes.
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| 3. |
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| 4. |
- Chen, Yuqian, et al.
(författare)
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Experimental study on combustion and flow resistance characteristics of an afterburner with air-cooled bluff-body flameholder
- 2022
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Ingår i: Aerospace Science and Technology. - : Elsevier BV. - 1270-9638. ; 123
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Tidskriftsartikel (refereegranskat)abstract
- In the afterburner assembled with an air-cooled bluff-body flameholder, cooling air is directly injected into the recirculation zone behind the bluff-body, which can reduce the local temperature and increase the oxygen concentration of the gas mixture in the wake of the bluff-body, thereby affecting the total pressure loss and combustion characteristics. To better understand the flow and combustion process of the system, the exhaust gas temperature, cold and hot total pressure losses in a rectangular premixed combustor are investigated under different cooling air jet conditions. Experimental results show that the added cooling air could improve the combustion efficiency and widen the blowout limit, whereas it could also give rise to an extra total pressure loss. However, when the cooling air flow rate was higher than a critical value, i.e., after the blowing ratio reached 2.5, the recirculation zone could be blown away, resulting in a failed ignition in the afterburner. Notably, the decreased temperature difference between the mainstream and the cooling air could improve the combustion efficiency and reduce the thermal resistance loss but enlarge the cold flow loss and hot total pressure loss. Moreover, since the oxygen content declined and autoignition appeared after the mainstream temperature reached 1100 K, the exhaust gas temperature and combustion efficiency declined rapidly, and the hot total pressure loss also decreased. In addition, with the fuel-gas ratio increasing, the combustion efficiency significantly dropped, the exhaust gas temperature and thermal resistance loss firstly increased to a peak value (at the equivalence ratio of 1.14) and then decreased for excessively fuel-rich combustion.
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