| 1. |
- Liu, Yage, et al.
(författare)
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Estimating the impact of shelterbelt structure on corn yield at a large scale using Google Earth and Sentinel 2 data
- 2022
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 17:4
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Tidskriftsartikel (refereegranskat)abstract
- A shelterbelt is an important measure to protect farmland and increase crop yield. However, how a shelterbelt structure affects crop yield is still unclear due to the difficulties accessing sufficient data from traditional field observations. To address this problem, we developed an innovative framework to estimate the shelterbelt structure and crop yield profile at a regional scale based on Google Earth and Sentinel-2 data. Using this method, we quantified the impact of the shelterbelt structure on the corn yield at 302 shelterbelts in the Northeast Plain of China. Generally, the corn yield increased (by 2.41% on average) within a distance of 1.2-15 times the tree height from the shelterbelt. Such an effect was particularly prominent within a distance of two to five times the tree height, where the corn yield was significantly increased by up to 4.63%. The structure of the shelterbelt has a significant effect on the magnitude of increase in yield of the surrounding corn. The increment of corn yields with high-, medium-high-, medium- and low-width-gap grade shelterbelt were 2.01%, 2.21%, 1.99%, and 0.91%, respectively. The medium-high grade shelterbelt achieved the largest yield increase effect. The location of the farmland relative to the shelterbelt also affected the yield, with a yield increase of 2.39% on the leeward side and 1.89% on the windward side, but it did not change the relationship between the yield increase effect and the shelterbelt structure. Our findings highlight the optimal shelterbelt structure for increasing corn yield, providing practical guidance on the design and management of farmland shelterbelts for maximizing yield.
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| 2. |
- Liu, Yage, et al.
(författare)
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Estimating the Legacy Effect of Post-Cutting Shelterbelt on Crop Yield Using Google Earth and Sentinel-2 Data
- 2022
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Ingår i: Remote Sensing. - : MDPI AG. - 2072-4292. ; 14:19
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Tidskriftsartikel (refereegranskat)abstract
- Shelterbelts (or windbreaks) can effectively improve the microclimate and soil conditions of adjacent farmland and thus increase crop yield. However, the individual contribution of these two factors to yield changes is still unclear since the short-term effect from the microclimate and the accumulated effect from the soil jointly affect crop yield. The latter (soil effect) is supposed to remain after shelterbelt-cutting, thus inducing a post-cutting legacy effect on yield, which can be used to decompose the shelterbelt-induced yield increase. Here, we develop an innovative framework to investigate the legacy effect of post-cutting shelterbelt on corn yield by combining Google Earth and Sentinel-2 data in Northeastern China. Using this framework, for the first time, we decompose the shelterbelt-induced yield increase effect into microclimate and soil effects by comparing the yield profiles before and after shelterbelt-cutting. We find that on average, the intensity of the legacy effect, namely the crop yield increment of post-cutting shelterbelts, is 0.98 ± 0.03%. The legacy effect varies depending on the shelterbelt–farmland relative location and shelterbelt density. The leeward side of the shelterbelt-adjacent farmland has a more remarkable legacy effect compared to the windward side. Shelterbelts with medium–high density have the largest legacy effect (1.94 ± 0.05%). Overall, the legacy effect accounts for 47% of the yield increment of the shelterbelt before cutting, implying that the soil effect is almost equally important for increasing crop yield compared to the microclimate effect. Our findings deepen the understanding of the mechanism of shelterbelt-induced yield increase effects and can help to guide shelterbelt management.
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| 3. |
- Ahlström, Anders, et al.
(författare)
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Hydrologic resilience and Amazon productivity
- 2017
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- The Amazon rainforest is disproportionately important for global carbon storage and biodiversity. The system couples the atmosphere and land, with moist forest that depends on convection to sustain gross primary productivity and growth. Earth system models that estimate future climate and vegetation show little agreement in Amazon simulations. Here we show that biases in internally generated climate, primarily precipitation, explain most of the uncertainty in Earth system model results; models, empirical data and theory converge when precipitation biases are accounted for. Gross primary productivity, above-ground biomass and tree cover align on a hydrological relationship with a breakpoint at ~2000 mm annual precipitation, where the system transitions between water and radiation limitation of evapotranspiration. The breakpoint appears to be fairly stable in the future, suggesting resilience of the Amazon to climate change. Changes in precipitation and land use are therefore more likely to govern biomass and vegetation structure in Amazonia.
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| 4. |
- Li, Huidong, et al.
(författare)
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Attributing the impacts of ecological engineering and climate change on carbon uptake in Northeastern China
- 2023
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Ingår i: Landscape Ecology. - 0921-2973 .- 1572-9761. ; 38:12, s. 3945-3960
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Tidskriftsartikel (refereegranskat)abstract
- Context: In the past decades, several ecological engineering (eco-engineering) programs have been conducted in China, leading to a significant increase in regional carbon sink. However, the contribution of different eco-engineering programs to carbon uptake is still not clear, as the location of different programs is difficult to identify, and their impacts are concurrent with climate change. Objectives: We aim to detect the location of eco-engineering programs and attribute the impacts of eco-engineering and climate change on vegetation dynamics and carbon uptake in Northeastern China during 2000–2020. Methods: We developed a new framework to detect the location of eco-engineering programs by combining a temporal pattern analysis method and Markov model, and to attribute the impacts of eco-engineering and climate change on vegetation greenness and carbon uptake by combining a neighbor contrast method within a sliding window and trend analysis on the normalized difference vegetation index (NDVI) and gross primary production (GPP). Results: We identified four main forestry eco-engineering programs: croplands to forest (CtoF), grasslands to forest (GtoF), savannas to forest (StoF), and natural forest conservation (NFC) programs, whose areas accounted for 2.11%, 1.89%, 3.41%, and 1.72% of the total study area, respectively. Both eco-engineering and climate change contributed to the increase in greenness and carbon uptake. Compared to climate change effect, eco-engineering increased NDVI and GPP by 121% and 21.43% on average, respectively. Specifically, the eco-engineering-induced increases in GPP were 54.1%, 9.46%, 8.13%, and 24.20% for CtoF, GtoF, StoF, and NFC, respectively. Conclusions: These findings highlight the important and direct contribution of eco-engineering on vegetation greening with positive effects on carbon sequestration at a fine scale, providing an important implication for eco-engineering planning and management towards a carbon-neutral future.
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| 5. |
- Lipzig, Nicole P.M.van, et al.
(författare)
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Representation of precipitation and top-of-atmosphere radiation in a multi-model convection-permitting ensemble for the Lake Victoria Basin (East-Africa)
- 2023
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Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 60:11-12, s. 4033-4054
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Tidskriftsartikel (refereegranskat)abstract
- The CORDEX Flagship Pilot Study ELVIC (climate Extremes in the Lake VICtoria basin) was recently established to investigate how extreme weather events will evolve in this region of the world and to provide improved information for the climate impact community. Here we assess the added value of the convection-permitting scale simulations on the representation of moist convective systems over and around Lake Victoria. With this aim, 10 year present-day model simulations were carried out with five regional climate models at both PARameterized (PAR) scales (12–25 km) and Convection-Permitting (CP) scales (2.5–4.5 km), with COSMO-CLM, RegCM, AROME, WRF and UKMO. Most substantial systematic improvements were found in metrics related to deep convection. For example, the timing of the daily maximum in precipitation is systematically delayed in CP compared to PAR models, thereby improving the agreement with observations. The large overestimation in the total number of rainy events is alleviated in the CP models. Systematic improvements were found in the diurnal cycle in Top-Of-Atmosphere (TOA) radiation and in some metrics for precipitation intensity. No unanimous improvement nor deterioration was found in the representation of the spatial distribution of total rainfall and the seasonal cycle when going to the CP scale. Furthermore, some substantial biases in TOA upward radiative fluxes remain. Generally our analysis indicates that the representation of the convective systems is strongly improved in CP compared to PAR models, giving confidence that the models are valuable tools for studying how extreme precipitation events may evolve in the future in the Lake Victoria basin and its surroundings.
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| 6. |
- Messori, Gabriele, et al.
(författare)
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Atmospheric jet stream variability reflects vegetation activity in Europe
- 2022
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Ingår i: Agricultural and Forest Meteorology. - : Elsevier. - 0168-1923 .- 1873-2240. ; 322
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Tidskriftsartikel (refereegranskat)abstract
- Jet streams are a key component of the climate system, whose dynamics couple closely to regional climate variability. Yet, the link between jet stream variability and vegetation activity has received little attention. Here, we leverage our understanding of the mid-latitude jet stream dynamics over the Euro-Atlantic sector to probe climate-vegetation interactions across Europe. We link indices related to the meridional location of the jet and the large-scale zonal wind speed with remotely-sensed vegetation greenness anomalies during locally-defined growing seasons. Correlations between greenness anomalies and jet latitude anomalies point to a control of the jet stream's variability on vegetation activity over large parts of Europe. This potential control is mediated by the jet latitude anomalies' correlations with temperature, soil moisture and downward surface solar radiation. The sign and strength of these correlations depend on location and time of the year. Furthermore, jet stream variability modulates conditions at the onset and end of the growing season. The link between jet latitude anomalies and vegetation greenness is not only specific to the climate zone, but also to the landclass and subperiod within the growing season. It is thus important to use a locally-defined growing season for interpreting the atmospheric controls on regional vegetation phenology. Results consistent with the correlation analysis emerge when focussing on local high or low greenness months only or on zonal wind speed anomalies, confirming the relevance of jet variability for vegetation activity.
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| 7. |
- Tamoffo, Alain T., et al.
(författare)
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Process-based assessment of the impact of reduced turbulent mixing on Congo Basin precipitation in the RCA4 Regional Climate Model
- 2021
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Ingår i: Climate Dynamics. - : Springer. - 0930-7575 .- 1432-0894. ; 56:5-6, s. 1951-1965
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Tidskriftsartikel (refereegranskat)abstract
- In regions featuring strong convective activity (such as the Congo Basin, CB), turbulent mixing in the planetary boundary layer strongly affects the water budget. In this study, we use a process-based evaluation to assess the performance of the Rossby Centre Regional Climate Model (RCM) RCA4 in simulating the September-November CB rainfall, under conditions of strong and weak turbulent mixing. To this regard, results from two different versions of model are analysed: the version used in the COordinated Regional climate Downscaling EXperiment framework (RCA4-v1), and a modified version (RCA4-v4), in which turbulent mixing is reduced. Experiments are driven with boundary conditions from the ERA-Interim reanalysis. Results show that RCA4-v4 improves the CB rainfall climatology compared to RCA4-v1. This result is further related to the models' different representations of the relevant driving mechanisms and processes. The model version with a reduced turbulent mixing (RCA4-v4) shifts less moisture from the lower troposphere towards the free troposphere. As the shallow convective mixing is reduced (owing to the reduction of the turbulent mixing), lower layers are moistened, and low level cloud fraction increases over Equatorial Africa. This increase is stronger over the West Equatorial African (WEA) coast than over the CB. The result is that surface solar radiation decreases more over the WEA coast than over the CB, which would result in a lower surface temperature over WEA coast than over the CB. An enhanced pressure gradient between the WEA and the CB is created as a result, thus enhancing the Congo low level cell, and low level westerlies (LLWs). LLWs are faster, meaning that more moisture flows through the CB Cell, is uplifted in eastern up-branch, and enters African Easterly Jets (AEJs), which, in turn, are intensified due to the increase in the surface temperature gradient. Intensification of the CB cell and mesoscale convective systems (MCSs) is the cause of the higher rainfall and is what improves the CB rainfall climatology in RCA4-v4. In addition, the increase in rainfall causes an increase in soil moisture in RCA4-v4 in both the north and south of the CB. Higher soil moisture does not affect evaporation in the north as soils are already saturated in RCA4-v1. However, the increase in rainfall increases soil moisture in the south in RCA4-v4, which increases evaporation as soils were initially unsaturated. This higher evaporation is exported out of the basin towards Southern Africa, does not recirculate through the Cell, and does not therefore contribute to further improving the rainfall bias over the Congo. Our results show that reducing turbulent mixing results in a better representation of the dynamics of the climate system over the CB and, in turn, improved precipitation.
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| 8. |
- Thonicke, Kirsten, et al.
(författare)
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Modeling vegetation and ecosystem responses to climate change and fire regime
- 2014
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Ingår i: Forest fires under climate, social and economic changes in Europe, the Mediterranean and other fire-affected areas of the world. - 9788469597590 ; , s. 32-33
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Bokkapitel (populärvet., debatt m.m.)abstract
- Climatic fire danger will likely increase because more droughts and heat-waves are caused by climate change. Climate change can shift fires from occurring only rarely to regularly in ecosystems not until now adapted to fire. We applied dynamic vegetation-fire models to investigate these future responses. The future of fire in Mediterranean-type ecosystems depends strongly on changes in vegetation productivity, thus fuel availability, if burned area increases as much as fire danger. Temperate ecosystems might be exposed to Mediterranean-like fire regimes. In high altitudes, Mediterranean trees might migrate up-hill and cause feedbacks between diversity and fire under climate change.
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| 9. |
- Thonicke, Kirsten, et al.
(författare)
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Threats of projected changes in fire regime for newly affected areas in Europe and Northern Africa
- 2014
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Ingår i: Forest fires under climate, social and economic changes in Europe, the Mediterranean and other fire-affected areas of the world. - 9788469597590 ; , s. 34-35
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Bokkapitel (populärvet., debatt m.m.)abstract
- Under climate change conditions, climatic wildfire danger could also increase in ecosystems not dominated by fires until now. This increasing trend could lead to more area burned in the future. We have developed an algorithm to map new fire-prone areas in Europe and Northern Africa that identifies grid points where a rare fire event is becoming the mean at the end of the 21st century. When applying the model to simulated changes in future fire regimes it revealed that these new fire-prone areas would be found mostly in Eastern Europe. Depending on the climate scenario and vegetation-fire model used, it could also extend to central and South-Eastern Europe.
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| 10. |
- Van Loon, Anne F., et al.
(författare)
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Review article: Drought as a continuum: memory effects in interlinked hydrological, ecological, and social systems
- 2024
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Droughts are often long lasting phenomena, without a distinct start or end, and with impacts cascading across sectors and systems, creating long-term legacies. Nevertheless, our current perception and management of droughts and their impacts is often event-based, which can limit the effective assessment of drought risks and reduction of drought impacts. Here, we advocate for changing this perspective and viewing drought as a hydro-eco-social continuum. We take a systems theory perspective and focus on how “memory” causes feedback and interactions between parts of the interconnected systems at different time scales. We first discuss the characteristics of the drought continuum with a focus on the hydrological, ecological, and social systems separately; and then study the system of systems. Our analysis is based on a review of the literature and a study of five cases: Chile, the Colorado River Basin in the US, Northeast Brazil, Kenya, and the Rhine River Basin in Northwest Europe. We find that the memories of past dry and wet periods, carried by both bio-physical (e.g. groundwater, vegetation) and social systems (e.g. people, governance), influence how future drought risk manifests. We identify four archetypes of drought dynamics: Impact & recovery; Slow resilience-building; Gradual collapse; and High resilience, big shock. The interactions between the hydrological, ecological and social systems result in systems shifting between these types, which plays out differently in the five case studies. We call for more research on drought preconditions and recovery in different systems, on dynamics cascading between systems and triggering system changes, and on dynamic vulnerability and maladaptation. Additionally, we argue for more continuous monitoring of drought hazards and impacts, modelling tools that better incorporate memories and adaptation responses, and management strategies that increase social and institutional memory to better deal with the complex hydro-eco-social drought continuum and identify effective pathways to adaptation.
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| 11. |
- Wu, Minchao, et al.
(författare)
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Drought Legacy in Sub-Seasonal Vegetation State and Sensitivity to Climate Over the Northern Hemisphere
- 2022
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 49:15
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Tidskriftsartikel (refereegranskat)abstract
- Droughts affect ecosystems at multiple time scales, but their sub-seasonal legacy effects on vegetation activity remain unclear. Combining the satellite-based enhanced vegetation index MODIS EVI with a novel location-specific definition of the growing season, we quantify drought impacts on sub-seasonal vegetation activity and the subsequent recovery in the Northern Hemisphere. Drought legacy effects are quantified as changes in post-drought greenness and sensitivity to climate. We find that greenness losses under severe drought are partially compensated by a ∼+5% greening within 2–6 growing-season months following the droughts, both in woody and herbaceous vegetation but at different timings. In addition, post-drought sensitivity of herbaceous vegetation to hydrological conditions increases noticeably at high latitudes compared with the local normal conditions, regardless of the choice of drought time scales. In general, the legacy effects on sensitivity are larger in herbaceous vegetation than in woody vegetation.
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| 12. |
- Wu, Minchao, et al.
(författare)
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Drought legacy in sub‐seasonal vegetation state and sensitivity to climate over the Northern Hemisphere
- 2022
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Ingår i: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 49:15
-
Tidskriftsartikel (refereegranskat)abstract
- Droughts affect ecosystems at multiple time scales, but their sub-seasonal legacy effects on vegetation activity remain unclear. Combining the satellite-based enhanced vegetation index MODIS EVI with a novel location-specific definition of the growing season, we quantify drought impacts on sub-seasonal vegetation activity and the subsequent recovery in the Northern Hemisphere. Drought legacy effects are quantified as changes in post-drought greenness and sensitivity to climate. We find that greenness losses under severe drought are partially compensated by a similar to+5% greening within 2-6 growing-season months following the droughts, both in woody and herbaceous vegetation but at different timings. In addition, post-drought sensitivity of herbaceous vegetation to hydrological conditions increases noticeably at high latitudes compared with the local normal conditions, regardless of the choice of drought time scales. In general, the legacy effects on sensitivity are larger in herbaceous vegetation than in woody vegetation.
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| 13. |
- Wu, Minchao, et al.
(författare)
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Early growing season anomalies in vegetation activity determine the large‐scale climate‐vegetation coupling in Europe
- 2021
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Ingår i: Journal of Geophysical Research: Biogeosciences. - : American Geophysical Union (AGU). - 2169-8961 .- 2169-8953. ; 126:5
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Tidskriftsartikel (refereegranskat)abstract
- The climate-vegetation coupling exerts a strong control on terrestrial carbon budgets and will affect the future evolution of global climate under continued anthropogenic forcing. Nonetheless, the effects of climatic conditions on such coupling at specific times in the growing season remain poorly understood. We quantify the climate-vegetation coupling in Europe over 1982–2014 at multiple spatial and temporal scales, by decomposing sub-seasonal anomalies of vegetation greenness using a grid-wise definition of the growing season. We base our analysis on long-term vegetation indices (Normalized Difference Vegetation Index and two-band Enhanced Vegetation Index), growing conditions (including 2m temperature, downwards surface solar radiation, and root-zone soil moisture), and multiple teleconnection indices that reflect the large-scale climatic conditions over Europe. We find that the large-scale climate-vegetation coupling during the first two months of the growing season largely determines the full-year coupling. The North Atlantic Oscillation and Scandinavian Pattern phases one-to-two months before the start of the growing season are the dominant and contrasting drivers of the early growing season climate-vegetation coupling over large parts of boreal and temperate Europe. The East Atlantic Pattern several months in advance of the growing season exerts a strong control on the temperate belt and the Mediterranean region. The strong role of early growing season anomalies in vegetative activity within the growing season emphasizes the importance of a grid-wise definition of the growing season when studying the large-scale climate-vegetation coupling in Europe.
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| 14. |
- Wu, Minchao, et al.
(författare)
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Impacts of land use on climate and ecosystem productivity over the Amazon and the South American continent
- 2017
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 12:5
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Tidskriftsartikel (refereegranskat)abstract
- The Amazon basin is characterized by a strong interplay between the atmosphere and vegetation. Anthropogenic land use and land cover change (LULCC) affects vegetation and the exchange of energy and water with the atmosphere. Here we have assessed potential LULCC impacts on climate and natural vegetation dynamics over South America with a regional Earth system model that also accounts for vegetation dynamics. The biophysical and biogeochemical impacts from LULCC were addressed with two simulations over the CORDEX-South America domain. The results show that LULCC imposes local and remote influences on South American climate. These include significant local warming over the LULCC-affected area, changes in circulation patterns over the Amazon basin during the dry season, and an intensified hydrological cycle over much of the LULCC-affected area during the wet season. These changes affect the natural vegetation productivity which shows contrasting and significant changes between northwestern (around 10% increase) and southeastern (up to 10% decrease) parts of the Amazon basin caused by mesoscale circulation changes during the dry season, and increased productivity in parts of the LULCC-affected areas. We conclude that ongoing deforestation around the fringes of the Amazon could impact pristine forest by changing mesoscale circulation patterns, amplifying the degradation of natural vegetation caused by direct, local impacts of land use activities.
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| 15. |
- Wu, Minchao
(författare)
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Land-atmosphere interactions and regional Earth system dynamics due to natural and anthropogenic vegetation changes
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Observation and modelling studies have indicated that the global land surfaces have been undergoing significant changes in the past few decades, driven by both natural and anthropogenic factors, such as changes in ecosystem productivity, fire and land use. Land surface changes can potentially influence local and regional climate through land-atmosphere interactions. Continued greenhouse gas emissions and current socioeconomic trends are expected to drive further land cover changes in the future, thus further understanding of land-atmosphere interactions including different feedback mechanisms is necessary to understand how future climate change will continue unfolding. Land-atmosphere interactions vary under different conditions. The strength of local land-atmosphere interactions depends on the capabilities of different land covers to control surface energy and mass exchanges, including latent and sensible heat, water and carbon. Local feedbacks can also influence regional to global climate, such as circulation changes that affect regional energy and moisture transport, or cloud cover that affects incoming radiation. Regional Earth system models (RESMs) with high resolution dynamical downscaling approaches and incorporating individual-based vegetation dynamics add value to the traditional global climate modelling studies for regions with highly complex topography or/and pronounced seasonal water deficits, potentially allowing for more refined land-atmosphere interactions studies thanks to more realistic vegetation dynamics and biophysical feedbacks, more accurate regional climate dynamics and overall richer spatial detail.In this thesis, I investigated regional land surface changes due to natural and anthropogenic vegetation changes and their impacts on land-atmosphere interactions, by applying a dynamical downscaling approach with RCA-GUESS, a RESM that couples the Rossby Centre regional climate model RCA4 to LPJ-GUESS, an ecosystem model that combines an individual-based representation of vegetation structure and dynamics with process-based physiology and biogeochemistry. Europe, Africa and South America were chosen as research domains. In the land surface study based on LPJ-GUESS simulations, I showed that future changes in the fire regime over Europe, driven by climate and socioeconomic change, were important for projecting future land surface changes. Fire-vegetation interactions and socioeconomic effects emerged as important uncertainties for future burned area. My study on land-atmosphere interactions based on RCA-GUESS simulations indicated that the hydrological cycle in the tropics was sensitive to land cover changes over semi-arid regions in Africa, and that biophysical feedbacks were important through their modulation of regional circulation patterns. A study based on the analysis of empirical datasets and CMIP5 ESMs outputs revealed that simulated climate biases are the main cause of model-data discrepancies. Models and data shared a marked hydrological relationship that suggested that decreased precipitation and land use change constituted the largest threats to the future Amazon forest. A study based on RCA-GUESS simulations with a realistic land use scenario identified both positive and negative impacts of land use on natural ecosystem productivity in the Amazon through its effects on the local and the regional climate.
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| 16. |
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| 17. |
- Wu, Minchao, et al.
(författare)
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Sensitivity of burned area in Europe to climate change, atmospheric CO2 levels, and demography: A comparison of two fire-vegetation models
- 2015
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Ingår i: Journal of Geophysical Research - Biogeosciences. - 2169-8953. ; 120:11, s. 2256-2272
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Tidskriftsartikel (refereegranskat)abstract
- Global environmental changes and human activity influence wildland fires worldwide, but the relative importance of the individual factors varies regionally and their interplay can be difficult to disentangle. Here we evaluate projected future changes in burned area at the European and sub-European scale, and we investigate uncertainties in the relative importance of the determining factors. We simulated future burned area with LPJ-GUESS-SIMFIRE, a patch-dynamic global vegetation model with a semiempirical fire model, and LPJmL-SPITFIRE, a dynamic global vegetation model with a process-based fire model. Applying a range of future projections that combine different scenarios for climate changes, enhanced CO2 concentrations, and population growth, we investigated the individual and combined effects of these drivers on the total area and regions affected by fire in the 21st century. The two models differed notably with respect to the dominating drivers and underlying processes. Fire-vegetation interactions and socioeconomic effects emerged as important uncertainties for future burned area in some European regions. Burned area of eastern Europe increased in both models, pointing at an emerging new fire-prone region that should gain further attention for future fire management.
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| 18. |
- Wu, Minchao, et al.
(författare)
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The impact of regional climate model formulation and resolution on simulated precipitation in Africa
- 2020
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Ingår i: Earth System Dynamics. - : Copernicus GmbH. - 2190-4979 .- 2190-4987. ; 11:2, s. 377-394
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the impact of model formulation and horizontal resolution on the ability of Regional Climate Models (RCMs) to simulate precipitation in Africa. Two RCMs (SMHI-RCA4 and HCLIM38-ALADIN) are utilized for downscaling the ERA-Interim reanalysis over Africa at four different resolutions: 25, 50, 100, and 200 km. In addition to the two RCMs, two different parameter settings (configurations) of the same RCA4 are used. By contrasting different downscaling experiments, it is found that model formulation has the primary control over many aspects of the precipitation climatology in Africa. Patterns of spatial biases in seasonal mean precipitation are mostly defined by model formulation, while the magnitude of the biases is controlled by resolution. In a similar way, the phase of the diurnal cycle in precipitation is completely controlled by model formulation (convection scheme), while its amplitude is a function of resolution. However, the impact of higher resolution on the time-mean climate is mixed. An improvement in one region/season (e.g. reduction in dry biases) often corresponds to a deterioration in another region/season (e.g. amplification of wet biases). At the same time, higher resolution leads to a more realistic distribution of daily precipitation. Consequently, even if the time-mean climate is not always greatly sensitive to resolution, the realism of the simulated precipitation increases as resolution increases. Our results show that improvements in the ability of RCMs to simulate precipitation in Africa compared to their driving reanalysis in many cases are simply related to model formulation and not necessarily to higher resolution. Such model formulation related improvements are strongly model dependent and can, in general, not be considered as an added value of downscaling.
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| 19. |
- Wu, Minchao, et al.
(författare)
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Vegetation-Climate Feedbacks Enhance Spatial Heterogeneity of Pan-Amazonian Ecosystem States Under Climate Change
- 2021
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Ingår i: Geophysical Research Letters. - 0094-8276. ; 48:8
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Tidskriftsartikel (refereegranskat)abstract
- Amazonian ecosystems range from rainforest to open dryland vegetation, with a following decrease in biomass along the moisture gradient. Biomass can vary greatly at the ecological transition zone between grass dominated savannahs and the forest. It is not well understood if the transition zone could expand under climate change, and thereby reduce ecosystem stability and carbon storage in biomass. Here, we quantify such changes by using a high-resolution regional Earth system model under RCP 8.5 climate scenario. We disentangle the effects of climate, CO2, and land use by considering vegetation-climate feedbacks. Our results suggest that future climate change combined with elevated atmospheric CO2 concentration tends to induce a larger spatial gradient of ecosystem states, increasing the transition area by ∼110% at the end of the century. Vegetation feedbacks generally amplify the climate effect by intensifying the climate-induced warming and drought, further enhancing spatial heterogeneity.
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| 20. |
- Wu, Minchao, et al.
(författare)
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Vegetation-climate feedbacks modulate rainfall patterns in Africa under future climate change
- 2016
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Ingår i: Earth System Dynamics. - : Copernicus GmbH. - 2190-4979 .- 2190-4987. ; 7:3, s. 627-647
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Tidskriftsartikel (refereegranskat)abstract
- Africa has been undergoing significant changes in climate and vegetation in recent decades, and continued changes may be expected over this century. Vegetation cover and composition impose important influences on the regional climate in Africa. Climate-driven changes in vegetation structure and the distribution of forests versus savannah and grassland may feed back to climate via shifts in the surface energy balance, hydrological cycle and resultant effects on surface pressure and larger-scale atmospheric circulation. We used a regional Earth system model incorporating interactive vegetation-atmosphere coupling to investigate the potential role of vegetation-mediated biophysical feedbacks on climate dynamics in Africa in an RCP8.5-based future climate scenario. The model was applied at high resolution (0.44 × 0.44°) for the CORDEX-Africa domain with boundary conditions from the CanESM2 general circulation model. We found that increased tree cover and leaf-area index (LAI) associated with a CO2 and climate-driven increase in net primary productivity, particularly over subtropical savannah areas, not only imposed important local effect on the regional climate by altering surface energy fluxes but also resulted in remote effects over central Africa by modulating the land-ocean temperature contrast, Atlantic Walker circulation and moisture inflow feeding the central African tropical rainforest region with precipitation. The vegetation-mediated feedbacks were in general negative with respect to temperature, dampening the warming trend simulated in the absence of feedbacks, and positive with respect to precipitation, enhancing rainfall reduction over the rainforest areas. Our results highlight the importance of accounting for vegetation-atmosphere interactions in climate projections for tropical and subtropical Africa.
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| 21. |
- Wu, Minchao, et al.
(författare)
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Vegetation‐climate feedbacks enhance spatial heterogeneity of pan‐amazonian ecosystem states under climate change
- 2021
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Ingår i: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 48:8
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Tidskriftsartikel (refereegranskat)abstract
- Amazonian ecosystems range from rainforest to open dryland vegetation, with a following decrease in biomass along the moisture gradient. Biomass can vary greatly at the ecological transition zone between grass dominated savannahs and the forest. It is not well understood if the transition zone could expand under climate change, and thereby reduce ecosystem stability and carbon storage in biomass. Here, we quantify such changes by using a high-resolution regional Earth system model under RCP 8.5 climate scenario. We disentangle the effects of climate, CO2, and land use by considering vegetation-climate feedbacks. Our results suggest that future climate change combined with elevated atmospheric CO2 concentration tends to induce a larger spatial gradient of ecosystem states, increasing the transition area by 110% at the end of the century. Vegetation feedbacks generally amplify the climate effect by intensifying the climate-induced warming and drought, further enhancing spatial heterogeneity.
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