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When Forests Hold Their Breath: Will Increasing Drought Further Disrupt Carbon Sequestration?
When Forests Hold Their Breath: Will Increasing Drought Further Disrupt Carbon Sequestration?
Chen, et al., (2024) Environmental Research Letters, in press (PDF)
The study, which meticulously combines in-situ data, satellite observations, and ecological derivations, reveals the drastic effects of severe drought on the carbon sequestration capacity of Taiwan's subtropical forests. At a time when the island nation's high-tech sector faced critical shortages due to water scarcity—a unique challenge of its own—the research also points to an ecological emergency: forests releasing more carbon than they absorb, thus ceasing their inherent function as a carbon sink. As the warming future implicates more drought, forests are more likely to cease taking out carbon temporarily.
Taiwan's wildfire projected to amplify due to increased drought
Taiwan's wildfire projected to amplify due to increased drought
Yu, et al., 2024: Estimating Wildfire Potential in Taiwan Under Different Climate Change Scenarios. Climatic Change, DOI: 10.1007/s10584-023-03669-z.
This study shows that climate change is increasing wildfire risk in Taiwan, mainly due to rising temperatures and variability in rainfall and humidity. Wildfires are more influenced by dryness rather than extreme heat. Future projections suggest a significant increase in wildfire occurrences, but reducing global warming could help mitigate this risk. These insights are crucial for developing strategies to manage the growing wildfire threat in Taiwan.
Decoding Utah's Complex Drought Patterns: Beyond El Niño
Decoding Utah's Complex Drought Patterns: Beyond El Niño
The talk summarizes drought variability in the Intermountain West, introducing analytical tools like correlation maps to study meteorological patterns. The researchers emphasize Utah's lack of ENSO signals. The concept of "quasi-decadal oscillations" is introduced, describing long-lasting droughts. The talk concludes by discussing "droughtanut events," intensified by these oscillations, which have broader, yet not fully understood, ecological impacts.
Feasibility of Adding Twitter Data to Aid Drought Depiction: Case Study in Colorado. https://doi.org/10.3390/w14182773
The use of social media has changed the information landscape for citizens’ participation in crisis response. A contemporary analysis of how social media data was conducted towards improvement in the detection of drought and its progression. The integration of data resources is viable given that the Twitter-based model outperformed the control run which did not include social media input. This study found that Twitter-based model was superior in predicting drought severity. Future work lies in expanding this method to depict drought in the western U.S.
Son, R., et al., 2022: Machine Learning provides substantial improvements to county-level fire weather forecasting over the western United States. Journal of Advances in Modeling Earth Systems, (PDF)
Fire weather prediction is significantly improved by a hybrid approach combining a weather forecast model and a machine learning algorithm. We train a deep learning technique with the model fields to directly produce a fire hazard estimate based solely on predicted weather conditions. The predictability of extreme danger fire conditions is enhanced which can be useful in reducing fire pre-suppression activities. The applied deep learning method also successfully produces a higher spatial resolution (4km) product useful for county-level fire forecasting. This approach shows that deep learning can be integrated into weather/climate models to produce a better quality of weather/climate-related products.
Son, R. et al., 2021: Recurrent pattern of extreme fire weather in California. Environmental Research Letters, DOI:10.1088/1748-9326/ac1f44
Historical wildfire events in California have shown a tendency to occur every five to seven years with a rapidly increasing tendency in recent decades. This oscillation is evident in multiple historical climate records, some more than a century long, and appears to be continuing. Analysis shows that this 5-7-year oscillation is linked to a sequence of anomalous large-scale climate patterns with an eastward propagation in both the ocean and atmosphere. While warmer temperature emerges from the northern central Pacific to the west coast of California, La Niña pattern develops simultaneously, implying that the lifecycle of the El Niño-Southern Oscillation that takes multiple years could be a trigger. The evolving patterns of the Pacific-to-North America atmospheric teleconnection suggest the role of tropical and subtropical forcing. The implications of this study lie in the amplification of hydrological cycle coupled with a semi-cyclical behavior of climate drivers for wildfire variability in California.
Stuivenvolt Allen, J., S.-Y. Wang, M. LaPlante, and J.-H. Yoon, 2020: Three western pacific typhoons strengthened fire weather in the recent northwest U.S. conflagration. Geophysical Research Letters, DOI:10.1029/2020GL091430
The weather pattern that contributed to rapidly spreading fires in Oregon in early September 2020 can be traced back to an unexpected source: Three typhoons in the western Pacific that ran into the Korean Peninsula within two weeks of each other. Together, Typhoon Bavi, Typhoon Maysak, and Typhoon Haishen each contained enough energy to perturb the jet stream – creating an atmospheric wave train that enhanced the hot, dry weather of the western United States. This study uses forecast models and weather observations to show that these typhoons amplified areas of high and low pressure in North America leading to the intense winds which rapidly spread fire in Oregon, Washington, and California. While the impacts of climate change on these events were not evaluated in this study, the implication is that the effect of weather extremes that are known to be exasperated by climate warming are not always limited to the region in which those extremes occur.
Son, R., H. Kim, S.-Y. Wang, J.-H. Jeong, S. Woo, J.-Y. Jeong, B.-D. Lee, S.-H. Kim, M. LaPlante, C.-G. Kwon, and J.-H. Yoon, 2021: Changes in fire weather climatology under 1.5°C and 2.0°C warming. Environmental Research Letters, DOI:10.1088/1748-9326/abe675
The Paris Agreement led to a number of studies that assessed the impact of the 1.5℃ and 2.0℃ increases in global temperature. In view of a recent series of high-profile wildfire events worldwide, we analyzed fire weather sensitivity based on a set of multi-model large ensemble climate simulations for these low-emission scenarios. The results indicate that the half degree difference between these two thresholds may lead to a significantly increased hazard of wildfire in certain parts of the world, particularly the Amazon, African savanna and Mediterranean. Although further experiments with human land use are needed to depict future fire activity, considering that rising temperatures are the most influential factor in augmenting the danger of fire weather, limiting global warming to 1.5℃ would alleviate some risk in these parts of the world.
Zhang, et al., 2020: Abrupt shift to hotter and drier climate over inner East Asia beyond the tipping point. Science, DOI: 10.1126/science.abb3368
Unprecedented heatwave-drought concurrences in the past two decades have been reported over inner East Asia. Tree-ring–based reconstructions of heatwaves and soil moisture for the past 260 years reveal an abrupt shift to hotter and drier climate over this region. Enhanced land-atmosphere coupling, associated with persistent soil moisture deficit, appears to intensify surface warming and anticyclonic circulation anomalies, fueling heatwaves that exacerbate soil drying. Our analysis demonstrates that the magnitude of the warm and dry anomalies compounding in the recent two decades is unprecedented over the quarter of a millennium, and this trend clearly exceeds the natural variability range. The “hockey stick”–like change warns that the warming and drying concurrence is potentially irreversible beyond a tipping point in the East Asian climate system.
The fire season in northern California during 2014 was the second longest in terms of burned areas since 1996. An increase in fire risk in California is attributable to human-induced climate change.
Yoon, J.-H., Wang, S.-Y., et al., 2015: Extreme Fire Season in California: A Glimpse into the Future? Bulletin of the American Meteorological Society, 96, DOI: 10.1175/BAMS-D-15-00114.1
A new paper was (in 2015) published which provides a glimpse into the future of wildfires. The paper is titled “Extreme fire season in California: A glimpse into the future?” It was published as the second chapter of “Explaining Extreme Events of 2014” which is from by the American Meteorological Society and it is available here. The lead-in summary to the article is very much to the point. It states,
Xu, C., W. An, S.-Y. Wang, Liang Yi et al., 2019: Increased drought events in Southwest China revealed by tree ring oxygen isotopes and potential role of Indian Ocean Dipole. Science of the Total Environment, DOI:10.1016/j.scitotenv.2019.01.186
Fosu, B., S.-Y. Wang, and J.-H. Yoon, 2016: The 2014/15 snowpack drought in Washington State and its climate forcing. Bulletin of the American Meteorological Society, S19-S24.
The Washington snowpack drought resulted from exceedingly high temperatures notwithstanding normal precipitation—a drought type that may re-occur due to accelerated anthropogenic warming and aggravated by naturally driven low precipitation. A significant portion of the snowpack drought can be explained by the cyclical relationship between temperature and precipitation that is apparently driven by the low frequency variability of the NPI.
Wang, S.-Y., Y.-H. Lin, R. R. Gillies, and K. Hakala, 2016: Indications for protracted groundwater depletion after drought over the Central Valley of California. Journal of Hydrometeorology. DOI: 10.1175/JHM-D-15-0105.1
Within California’s Central Valley, drought and increased groundwater depletion occurs almost hand in hand, but this relationship appears to have changed over the last decade. Well data have revealed a continued depletion of groundwater lasting a full year after drought, a phenomenon that was not observed in earlier records before the twenty-first century. Possible causes include 1) lengthening of drought associated with amplification in the drought-El Niño covariability since the late 1990s and 2) intensification of drought and increased pumping that enhances depletion. In the future, groundwater storage in the Central Valley will likely continue to diminish even further the drought has eased.
Wang, S.-Y., et al., 2015: An intensified seasonal transition in the central U.S. that enhances summer drought. Journal of Geophysical Research-A, 120, 8804–8816.
During the seasonal transition from June to July, average precipitation in the Central U.S. decreases by 25%. This precipitation decrease has intensified and this trend enhances spring drought occurrences in the Central U.S., in which conditions quickly evolve from being abnormally dry to exceptionally dry. The intensified June–July precipitation reduction is accompanied by increased downward shortwave radiation flux, tropospheric subsidence, enhanced evaporative fraction, and elevated planetary boundary layer height, all of which can lead to surface drying. The change in tropospheric circulation was characterized by an anomalous ridge over the western U.S. and a trough on either side—a pattern similar with the 2012 flash drought.
=see also=> Wang, S.-Y., et al., 2014: Could the 2012 drought in central U.S. have been anticipated? J. Earth Sci. Engineering, 4, 428-437.
Rao, M. P., ...S.-Y. Wang, et al., 2015: Dzuds, droughts, and livestock mortality in Mongolia. Environmental Research Letters, 10, 074012
Incidences of mass livestock mortality, known as dzud, have caused 20 million head of livestock to perish in 2000–2002 and 2009–2010. Data collected from 21 Mongolian aimags (provinces) between 1955 and 2013 show that livestock mortality is most strongly linked to winter temperatures, with anomalously cold winter and prior summer drought and precipitation deficit being the triggers for mortality. A density independent mortality model based on winter temperature, summer drought, summer precipitation, and summer potential evaporanspiration explains 48.4% of the total variability in the mortality dataset.
Wang, S.-Y., et al., 2014: Probable causes of the abnormal ridge accompanying the 2013-14 California drought: ENSO precursor and anthropogenic warming footprint. Geophysical Research Letters. DOI: 10.1002/2014GL059748
The 2013–2014 California drought was initiated by an anomalous high‐amplitude ridge that emerged from sources of Rossby wave energy in the western North Pacific. Further, the ridge deepened the trough over the northeast U.S., forming a dipole. The dipole and associated circulation pattern is not linked directly with either ENSO or PDO; instead, it has increasingly correlated with a type of ENSO precursor due to greenhouse-gas warming. There is a traceable anthropogenic footprint in the enormous intensity of the anomalous ridge during the 2013–2014 winter and the associated California drought.
Nature (509, page10, 2014):
Barandiaran, D., S.-Y. Wang, and K. Hilburn, 2013: Observed trends in the Great Plains low-level jet and associated precipitation changes in relation to recent droughts. Geophysical Research Letters, 40, 6247–6251.
The Great Plains drought tends to start in late spring and progress into summer. Trends in the Great Plains low‐level jet (GPLLJ) during April–June and associated precipitation analyzed for 1979–2012 show that (1) the GPLLJ has strengthened and expanded northward and (2) precipitation has decreased substantially in the Southern Plains while increasing in the Northern Plains. Particularly in May, the rainy season in the Oklahoma‐Texas region, precipitation has migrated northward in correspondence to the shifted northern edge of the GPLLJ, leading to near 50% declines in precipitation. These observed changes may have exacerbated the recent droughts.
Wang, S.-Y., J.-H. Yoon, R. R. Gillies, and C. Cho, 2013: What caused the winter drought in western Nepal during recent years? Journal of Climate. 26, 8241-8256
Western Nepal experienced consecutive and worsening winter drought conditions since 2000, culminating in a severe drought episode during 2008/09. In this study, the climate diagnosis revealed that 1) winter drought in western Nepal is linked decadal variability of the Arctic Oscillation, which initiates a tropospheric short-wave train across Eurasia and South Asia; and that 2) the persistent warming of the Indian Ocean contributes to the suppression of rainfall through enhanced local Hadley circulation. CMIP5 historical single-forcing experiments indicated that the increased loading of anthropogenic aerosols is compounding the precipitation decline. Given the observations that winter precipitation has declined to near zero while groundwater has hardly been replenished, appropriate management of western Nepal's water resources is both critical and necessary.
Wang, S.-Y., R. R. Gillies, and T. Reichler, 2012: Multi-decadal drought cycles in the Great Basin recorded by the Great Salt Lake: Modulation from a transition-phase teleconnection. Journal of Climate, 25, 1711-1721.
The multidecadal drought cycles as revealed by lake level fluctuation of the Great Salt Lake (GSL) point to a phase shift amounting to 6–9 years between the wet–dry cycles in the Great Basin and the warm–cool phases of the interdecadal Pacific oscillation (IPO). Diagnoses of the sea surface temperature and atmospheric circulation anomalies attribute such a phase shift to a distinctive teleconnection wave train that develops during the transition points between the IPO’s warm and cool phases. This teleconnection wave train forms recurrent circulation anomalies centered over the southeastern Gulf of Alaska; this directs moisture flux across the Great Basin and subsequently drives wet–dry conditions over the Great Basin and the GSL watershed.
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