| 1. |
- Haverd, Vanessa, et al.
(author)
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A stand-alone tree demography and landscape structure module for Earth system models
- 2013
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In: Geophysical Research Letters. - : American Geophysical Union (AGU). - 1944-8007 .- 0094-8276. ; 40:19, s. 5234-5239
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Journal article (peer-reviewed)abstract
- We propose and demonstrate a new approach for the simulation of woody ecosystem stand dynamics, demography, and disturbance-mediated heterogeneity suitable for continental to global applications and designed for coupling to the terrestrial ecosystem component of any earth system model. The approach is encoded in a model called Populations-Order-Physiology (POP). We demonstrate the behavior and performance of POP coupled to the Community Atmosphere Biosphere Land Exchange model (CABLE) applied along the Northern Australian Tropical Transect, featuring gradients in rainfall and fire disturbance. The model is able to simultaneously reproduce observation-based estimates of key functional and structural variables along the transect, namely gross primary production, tree foliage projective cover, basal area, and maximum tree height. Prospects for the use of POP to address current vegetation dynamic deficiencies in earth system modeling are discussed.
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| 2. |
- Hantson, Stijn, et al.
(author)
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Quantitative assessment of fire and vegetation properties in simulations with fire-enabled vegetation models from the Fire Model Intercomparison Project
- 2020
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In: Geoscientific Model Development. - : Copernicus GmbH. - 1991-959X .- 1991-9603. ; 13:7, s. 3299-3318
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Journal article (peer-reviewed)abstract
- Global fire-vegetation models are widely used to assess impacts of environmental change on fire regimes and the carbon cycle and to infer relationships between climate, land use and fire. However, differences in model structure and parameterizations, in both the vegetation and fire components of these models, could influence overall model performance, and to date there has been limited evaluation of how well different models represent various aspects of fire regimes. The Fire Model Intercomparison Project (FireMIP) is coordinating the evaluation of state-of-the-art global fire models, in order to improve projections of fire characteristics and fire impacts on ecosystems and human societies in the context of global environmental change. Here we perform a systematic evaluation of historical simulations made by nine FireMIP models to quantify their ability to reproduce a range of fire and vegetation benchmarks. The FireMIP models simulate a wide range in global annual total burnt area (39-536 Mha) and global annual fire carbon emission (0.91-4.75 Pg C yr-1) for modern conditions (2002-2012), but most of the range in burnt area is within observational uncertainty (345-468 Mha). Benchmarking scores indicate that seven out of nine FireMIP models are able to represent the spatial pattern in burnt area. The models also reproduce the seasonality in burnt area reasonably well but struggle to simulate fire season length and are largely unable to represent interannual variations in burnt area. However, models that represent cropland fires see improved simulation of fire seasonality in the Northern Hemisphere. The three FireMIP models which explicitly simulate individual fires are able to reproduce the spatial pattern in number of fires, but fire sizes are too small in key regions, and this results in an underestimation of burnt area. The correct representation of spatial and seasonal patterns in vegetation appears to correlate with a better representation of burnt area. The two older fire models included in the FireMIP ensemble (LPJ-GUESS-GlobFIRM, MC2) clearly perform less well globally than other models, but it is difficult to distinguish between the remaining ensemble members; some of these models are better at representing certain aspects of the fire regime; none clearly outperforms all other models across the full range of variables assessed.
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| 3. |
- Pellegrini, Adam F.A., et al.
(author)
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Fire frequency drives decadal changes in soil carbon and nitrogen and ecosystem productivity
- 2018
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 553:7687, s. 194-198
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Journal article (peer-reviewed)abstract
- Fire frequency is changing globally and is projected to affect the global carbon cycle and climate. However, uncertainty about how ecosystems respond to decadal changes in fire frequency makes it difficult to predict the effects of altered fire regimes on the carbon cycle; for instance, we do not fully understand the long-term effects of fire on soil carbon and nutrient storage, or whether fire-driven nutrient losses limit plant productivity. Here we analyse data from 48 sites in savanna grasslands, broadleaf forests and needleleaf forests spanning up to 65 years, during which time the frequency of fires was altered at each site. We find that frequently burned plots experienced a decline in surface soil carbon and nitrogen that was non-saturating through time, having 36 per cent (±13 per cent) less carbon and 38 per cent (±16 per cent) less nitrogen after 64 years than plots that were protected from fire. Fire-driven carbon and nitrogen losses were substantial in savanna grasslands and broadleaf forests, but not in temperate and boreal needleleaf forests. We also observe comparable soil carbon and nitrogen losses in an independent field dataset and in dynamic model simulations of global vegetation. The model study predicts that the long-term losses of soil nitrogen that result from more frequent burning may in turn decrease the carbon that is sequestered by net primary productivity by about 20 per cent of the total carbon that is emitted from burning biomass over the same period. Furthermore, we estimate that the effects of changes in fire frequency on ecosystem carbon storage may be 30 per cent too low if they do not include multidecadal changes in soil carbon, especially in drier savanna grasslands. Future changes in fire frequency may shift ecosystem carbon storage by changing soil carbon pools and nitrogen limitations on plant growth, altering the carbon sink capacity of frequently burning savanna grasslands and broadleaf forests.
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| 4. |
- Rowlinson, Matthew J., et al.
(author)
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Tropospheric ozone radiative forcing uncertainty due to pre-industrial fire and biogenic emissions
- 2020
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In: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 20:18, s. 10937-10951
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Journal article (peer-reviewed)abstract
- pTropospheric ozone concentrations are sensitive to natural emissions of precursor compounds. In contrast to existing assumptions, recent evidence indicates that terrestrial vegetation emissions in the pre-industrial era were larger than in the present day. We use a chemical transport model and a radiative transfer model to show that revised inventories of pre-industrial fire and biogenic emissions lead to an increase in simulated pre-industrial ozone concentrations, decreasing the estimated pre-industrial to present-day tropospheric ozone radiative forcing by up to 34 % (0.38 to 0.25 W mspan classCombining double low line"inline-formula"-2/span). We find that this change is sensitive to employing biomass burning and biogenic emissions inventories based on matching vegetation patterns, as the co-location of emission sources enhances the effect on ozone formation. Our forcing estimates are at the lower end of existing uncertainty range estimates (0.2-0.6 W mspan classCombining double low line"inline-formula"-2/span), without accounting for other sources of uncertainty. Thus, future work should focus on reassessing the uncertainty range of tropospheric ozone radiative forcing.
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| 5. |
- Svenhag, Carl, et al.
(author)
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Implementing detailed nucleation predictions in the Earth system model EC-Earth3.3.4: sulfuric acid–ammonia nucleation
- 2024
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In: Geoscientific Model Development. - Malmö : IVL Svenska Miljöinstitutet. - 1991-959X .- 1991-9603. ; 17:12, s. 4923-4942
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Journal article (peer-reviewed)abstract
- Representing detailed atmospheric aerosol processes in global Earth system models (ESMs) has proven to be challenging from both a computational and a parameterizationperspective. The representation of secondary organic aerosol (SOA) formation and new particle formation (NPF) in large ESMs is generally constructed with low detail to save computational costs. The simplification could result in losing the representation of some processes. In this study, we test and evaluate a new approach for improving the description of NPF processes in the ESM EC-Earth3 (ECE3) without significant additional computational burden.The current NPF scheme in EC-Earth3.3.4 is derived from the nucleation of low volatility organic vapors and sulfuric acid (H2SO4) together with a homogeneous water-H2SO4 nucleation scheme. We expand the existing schemes and introduce a new lookup table approach that incorporates detailed formation rate predictions through molecular modeling of sulfuric acid–ammonia nucleation (H2SO2–NH3). We apply tables of particle formation rates for H2SO2–NH3 nucleation, including dependence on temperature, atmospheric ion production rate, and molecular cluster scavenging sink.The resulting differences between using the H2SO4–NH3 nucleation in ECE3 and the original default ECE3 scheme are evaluated and compared with a focus on changes in the aerosol composition, cloud properties, and radiation balance. From this new nucleation scheme, EC-Earth3’s global average aerosol concentrations in the sub-100 nm sizes increased by 12 %–28 %. Aerosol concentrations above 100 nm and the direct radiative effect (in Wm?2) showed only minor differences upon changing of the nucleation scheme. However, the radiative effect from clouds affected by aerosols from the new nucleation scheme resulted in a global decrease (cooling effect) by 0.28–1Wm?2. The modeled aerosol concentrations were compared to observed measurements at various stations. In most cases, the new NPF predictions (H2SO2–NH3) performed better at stations where previous underestimations for aerosol concentrations occurred.
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