73 results on '"Watts, Jennifer D."'
Search Results
52. Remote Sensing of Environmental Changes in Cold Regions: Methods, Achievements and Challenges
- Author
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Du, Jinyang, primary, Watts, Jennifer D., additional, Jiang, Lingmei, additional, Lu, Hui, additional, Cheng, Xiao, additional, Duguay, Claude, additional, Farina, Mary, additional, Qiu, Yubao, additional, Kim, Youngwook, additional, Kimball, John S., additional, and Tarolli, Paolo, additional
- Published
- 2019
- Full Text
- View/download PDF
53. Investigating the sensitivity of soil respiration to recent snow cover changes in Alaska using a satellite-based permafrost carbon model.
- Author
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Yonghong Yi, Kimball, John S., Watts, Jennifer D., Natali, Susan M., Zona, Donatella, Liu, Junjie, Ueyama, Masahito, Hideki Kobayashi, Oechel, Walter, and Miller, Charles E.
- Subjects
TUNDRAS ,SOIL respiration ,SNOW cover ,HETEROTROPHIC respiration ,PERMAFROST ,CLIMATE feedbacks ,SEASONAL temperature variations - Abstract
The contribution of soil heterotrophic respiration to the boreal-Arctic carbon (CO
2 ) cycle and its potential feedback to climate change remain poorly quantified. We developed a remote sensing driven permafrost carbon model at intermediate scale (~ 1 km) to investigate how environmental factors affect the magnitude and seasonality of soil heterotrophic respiration in Alaska. The permafrost carbon model simulates snow and soil thermal dynamics, and accounts for vertical soil carbon transport and decomposition at depths up to 3 m below surface. Model outputs include soil temperature profiles and carbon fluxes at 1-km resolution spanning the recent satellite era (2001-2017) across Alaska. Comparisons with eddy covariance tower measurements show that the model captures the seasonality of carbon fluxes, with favorable accuracy in predicting net ecosystem CO2 exchange (NEE) in both tundra (R > 0.8, RMSE = 0.34 g C m-2 d-1 ) and boreal forest (R > 0.73, RMSE = 0.51 g C m-2 d-1 ). Benchmark assessments using two regional in-situ datasets indicate that the model captures the complex influence of snow insulation on soil temperature, and the temperature sensitivity of cold-season soil respiration. Across Alaska, we find that seasonal snow cover imposes strong controls on the contribution from different soil depths to total soil carbon emissions. Earlier snow melt in spring promotes deeper soil warming and enhances the contribution of deeper soils to total soil respiration during the later growing season, thereby reducing net ecosystem carbon uptake. Early cold-season soil respiration is closely linked to the number of snow-free days after land surface freezes (R = -0.48, p < 0.1), i.e. the delay in snow onset relative to surface freeze onset. Recent trends toward earlier autumn snow onset in northern Alaska promote a longer zero-curtain period and enhanced cold-season respiration. In contrast, southwestern Alaska shows a strong reduction in the number of snow-free days after land surface freeze onset, leading to earlier soil freezing and a large reduction in cold-season soil respiration. Our results also show non-negligible influences of sub-grid variability of surface conditions on the model simulated CO2 seasonal cycle, especially during the early cold season at 10-km scale. Our results demonstrate the critical role of snow cover affecting the seasonality of soil temperature and respiration and highlight the challenges of incorporating these complex processes into future projections of boreal-Arctic carbon cycle. [ABSTRACT FROM AUTHOR]- Published
- 2020
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54. Increased high‐latitude photosynthetic carbon gain offset by respiration carbon loss during an anomalous warm winter to spring transition.
- Author
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Liu, Zhihua, Kimball, John S., Parazoo, Nicholas C., Ballantyne, Ashley P., Wang, Wen J., Madani, Nima, Pan, Caleb G., Watts, Jennifer D., Reichle, Rolf H., Sonnentag, Oliver, Marsh, Philip, Hurkuck, Miriam, Helbig, Manuel, Quinton, William L., Zona, Donatella, Ueyama, Masahito, Kobayashi, Hideki, and Euskirchen, Eugénie S.
- Subjects
CARBON offsetting ,ATMOSPHERIC circulation ,ATMOSPHERIC temperature ,CLIMATE change ,HYDROLOGY ,WINTER - Abstract
Arctic and boreal ecosystems play an important role in the global carbon (C) budget, and whether they act as a future net C sink or source depends on climate and environmental change. Here, we used complementary in situ measurements, model simulations, and satellite observations to investigate the net carbon dioxide (CO2) seasonal cycle and its climatic and environmental controls across Alaska and northwestern Canada during the anomalously warm winter to spring conditions of 2015 and 2016 (relative to 2010–2014). In the warm spring, we found that photosynthesis was enhanced more than respiration, leading to greater CO2 uptake. However, photosynthetic enhancement from spring warming was partially offset by greater ecosystem respiration during the preceding anomalously warm winter, resulting in nearly neutral effects on the annual net CO2 balance. Eddy covariance CO2 flux measurements showed that air temperature has a primary influence on net CO2 exchange in winter and spring, while soil moisture has a primary control on net CO2 exchange in the fall. The net CO2 exchange was generally more moisture limited in the boreal region than in the Arctic tundra. Our analysis indicates complex seasonal interactions of underlying C cycle processes in response to changing climate and hydrology that may not manifest in changes in net annual CO2 exchange. Therefore, a better understanding of the seasonal response of C cycle processes may provide important insights for predicting future carbon–climate feedbacks and their consequences on atmospheric CO2 dynamics in the northern high latitudes. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
55. A global satellite environmental data record derived from AMSR-E and AMSR2 microwave Earth observations
- Author
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Du, Jinyang, primary, Kimball, John S., additional, Jones, Lucas A., additional, Kim, Youngwook, additional, Glassy, Joseph, additional, and Watts, Jennifer D., additional
- Published
- 2017
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56. POTENTIAL CONTRASTS IN CO2 AND CH4 FLUX RESPONSE UNDER CHANGING CLIMATE CONDITIONS: A SATELLITE REMOTE SENSING DRIVEN ANALYSIS OF THE NET ECOSYSTEM CARBON BUDGET FOR ARCTIC AND BOREAL REGIONS
- Author
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Watts, Jennifer D. and Watts, Jennifer D.
- Abstract
The impact of warming on the net ecosystem carbon budget (NECB) in Arctic-boreal regions remains highly uncertain. Heightened CH4 emissions from Arctic-boreal ecosystems could shift the northern NECB from an annual carbon sink further towards net carbon source. Northern wetland CH4 fluxes may be particularly sensitive to climate warming, increased soil temperatures and duration of the soil non-frozen period. Changes in northern high latitude surface hydrology will also impact the NECB, with surface and soil wetting resulting from thawing permafrost landscapes and shifts in precipitation patterns; summer drought conditions can potentially reduce vegetation productivity and land sink of atmospheric CO2 but also moderate the magnitude of CH4 increase. The first component of this work develops methods to assess seasonal variability and longer term trends in Arctic-boreal surface water inundation from satellite microwave observations, and quantifies estimate uncertainty. The second component of this work uses this information to improve understanding of impacts associated with changing environmental conditions on high latitude wetland CH4 emissions. The third component focuses on the development of a satellite remote sensing data informed Terrestrial Carbon Flux (TCF) model for northern wetland regions to quantify daily CH4 emissions and the NECB, in addition to vegetation productivity and landscape CO2 respiration loss. Finally, the fourth component of this work features further enhancement of the TCF model by improving representation of diverse tundra and boreal wetland ecosystem land cover types. A comprehensive database for tower eddy covariance CO2 and CH4 flux observations for the Arctic-boreal region was developed to support these efforts, providing an assessment of the TCF model ability to accurately quantify contemporary changes in regional terrestrial carbon sink/source strength.
- Published
- 2017
57. Supplementary material to "A global satellite environmental data record derived from AMSR-E and AMSR2 microwave earth observations"
- Author
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Du, Jinyang, primary, Kimball, John S., additional, Jones, Lucas A., additional, Kim, Youngwook, additional, Glassy, Joseph, additional, and Watts, Jennifer D., additional
- Published
- 2017
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58. Satellite microwave assessment of Northern Hemisphere lake ice phenology from 2002 to 2015
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Du, Jinyang, primary, Kimball, John S., additional, Duguay, Claude, additional, Kim, Youngwook, additional, and Watts, Jennifer D., additional
- Published
- 2017
- Full Text
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59. Large loss of CO2in winter observed across the northern permafrost region
- Author
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Natali, Susan M., Watts, Jennifer D., Rogers, Brendan M., Potter, Stefano, Ludwig, Sarah M., Selbmann, Anne-Katrin, Sullivan, Patrick F., Abbott, Benjamin W., Arndt, Kyle A., Birch, Leah, Bjo¨rkman, Mats P., Bloom, A. Anthony, Celis, Gerardo, Christensen, Torben R., Christiansen, Casper T., Commane, Roisin, Cooper, Elisabeth J., Crill, Patrick, Czimczik, Claudia, Davydov, Sergey, Du, Jinyang, Egan, Jocelyn E., Elberling, Bo, Euskirchen, Eugenie S., Friborg, Thomas, Genet, Hélène, Göckede, Mathias, Goodrich, Jordan P., Grogan, Paul, Helbig, Manuel, Jafarov, Elchin E., Jastrow, Julie D., Kalhori, Aram A. M., Kim, Yongwon, Kimball, John S., Kutzbach, Lars, Lara, Mark J., Larsen, Klaus S., Lee, Bang-Yong, Liu, Zhihua, Loranty, Michael M., Lund, Magnus, Lupascu, Massimo, Madani, Nima, Malhotra, Avni, Matamala, Roser, McFarland, Jack, McGuire, A. David, Michelsen, Anders, Minions, Christina, Oechel, Walter C., Olefeldt, David, Parmentier, Frans-Jan W., Pirk, Norbert, Poulter, Ben, Quinton, William, Rezanezhad, Fereidoun, Risk, David, Sachs, Torsten, Schaefer, Kevin, Schmidt, Niels M., Schuur, Edward A. G., Semenchuk, Philipp R., Shaver, Gaius, Sonnentag, Oliver, Starr, Gregory, Treat, Claire C., Waldrop, Mark P., Wang, Yihui, Welker, Jeffrey, Wille, Christian, Xu, Xiaofeng, Zhang, Zhen, Zhuang, Qianlai, and Zona, Donatella
- Abstract
Recent warming in the Arctic, which has been amplified during the winter1–3, greatly enhances microbial decomposition of soil organic matter and subsequent release of carbon dioxide (CO2)4. However, the amount of CO2released in winter is not known and has not been well represented by ecosystem models or empirically based estimates5,6. Here we synthesize regional in situ observations of CO2flux from Arctic and boreal soils to assess current and future winter carbon losses from the northern permafrost domain. We estimate a contemporary loss of 1,662?TgC per year from the permafrost region during the winter season (October–April). This loss is greater than the average growing season carbon uptake for this region estimated from process models (-1,032?TgC per year). Extending model predictions to warmer conditions up to 2100 indicates that winter CO2emissions will increase 17% under a moderate mitigation scenario—Representative Concentration Pathway 4.5—and 41% under business-as-usual emissions scenario—Representative Concentration Pathway 8.5. Our results provide a baseline for winter CO2emissions from northern terrestrial regions and indicate that enhanced soil CO2loss due to winter warming may offset growing season carbon uptake under future climatic conditions.
- Published
- 2019
- Full Text
- View/download PDF
60. Environmental Research Letters / Surface water inundation in the boreal-Arctic : potential impacts on regional methane emissions
- Author
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Watts, Jennifer D, Kimball, John S, Bartsch, Annett, and McDonald, Kyle C
- Abstract
Northern wetlands may be vulnerable to increased carbon losses from methane (CH4), a potent greenhouse gas, under current warming trends. However, the dynamic nature of open water inundation and wetting/drying patterns may constrain regional emissions, offsetting the potential magnitude of methane release. Here we conduct a satellite data driven model investigation of the combined effects of surface warming and moisture variability on high northern latitude (45 N) wetland CH4 emissions, by considering (1) sub-grid scale changes in fractional water inundation (Fw) at 15 day, monthly and annual intervals using 25 km resolution satellite microwave retrievals, and (2) the impact of recent (200311) wetting/drying on northern CH4 emissions. The model simulations indicate mean summer contributions of 53 Tg CH4 yr1 from boreal-Arctic wetlands. Approximately 10% and 16% of the emissions originate from open water and landscapes with emergent vegetation, as determined from respective 15 day Fw means or maximums, and significant increases in regional CH4 efflux were observed when incorporating satellite observed inundated land fractions into the model simulations at monthly or annual time scales. The satellite Fw record reveals widespread wetting across the Arctic continuous permafrost zone, contrasting with surface drying in boreal Canada, Alaska and western Eurasia. Arctic wetting and summer warming increased wetland emissions by 0.56 Tg CH4 yr1 compared to the 200311 mean, but this was mainly offset by decreasing emissions (0.38 Tg CH4 yr1) in sub-Arctic areas experiencing surface drying or cooling. These findings underscore the importance of monitoring changes in surface moisture and temperature when assessing the vulnerability of boreal-Arctic wetlands to enhanced greenhouse gas emissions under a shifting climate.
- Published
- 2014
61. Satellite Microwave Assessment of Northern Hemisphere Lake Ice Phenology from 2002 to 2015
- Author
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Du, Jinyang, primary, Kimball, John S., additional, Duguay, Claude, additional, Kim, Youngwook, additional, and Watts, Jennifer D., additional
- Published
- 2016
- Full Text
- View/download PDF
62. Cold season emissions dominate the Arctic tundra methane budget
- Author
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Zona, Donatella, primary, Gioli, Beniamino, additional, Commane, Róisín, additional, Lindaas, Jakob, additional, Wofsy, Steven C., additional, Miller, Charles E., additional, Dinardo, Steven J., additional, Dengel, Sigrid, additional, Sweeney, Colm, additional, Karion, Anna, additional, Chang, Rachel Y.-W., additional, Henderson, John M., additional, Murphy, Patrick C., additional, Goodrich, Jordan P., additional, Moreaux, Virginie, additional, Liljedahl, Anna, additional, Watts, Jennifer D., additional, Kimball, John S., additional, Lipson, David A., additional, and Oechel, Walter C., additional
- Published
- 2015
- Full Text
- View/download PDF
63. Resolving the Carbon‐Climate Feedback Potential of Wetland CO2and CH4Fluxes in Alaska
- Author
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Ma, Shuang, Bloom, A. Anthony, Watts, Jennifer D., Quetin, Gregory R., Donatella, Zona, Euskirchen, Eugénie S., Norton, Alexander J., Yin, Yi, Levine, Paul A., Braghiere, Renato K., Parazoo, Nicholas C., Worden, John R., Schimel, David S., and Miller, Charles E.
- Abstract
Boreal‐Arctic regions are key stores of organic carbon (C) and play a major role in the greenhouse gas balance of high‐latitude ecosystems. The carbon‐climate (C‐climate) feedback potential of northern high‐latitude ecosystems remains poorly understood due to uncertainty in temperature and precipitation controls on carbon dioxide (CO2) uptake and the decomposition of soil C into CO2and methane (CH4) fluxes. While CH4fluxes account for a smaller component of the C balance, the climatic impact of CH4outweighs CO2(28–34 times larger global warming potential on a 100‐year scale), highlighting the need to jointly resolve the climatic sensitivities of both CO2and CH4. Here, we jointly constrain a terrestrial biosphere model with in situ CO2and CH4flux observations at seven eddy covariance sites using a data‐model integration approach to resolve the integrated environmental controls on land‐atmosphere CO2and CH4exchanges in Alaska. Based on the combined CO2and CH4flux responses to climate variables, we find that 1970‐present climate trends will induce positive C‐climate feedback at all tundra sites, and negative C‐climate feedback at the boreal and shrub fen sites. The positive C‐climate feedback at the tundra sites is predominantly driven by increased CH4emissions while the negative C‐climate feedback at the boreal site is predominantly driven by increased CO2uptake (80% from decreased heterotrophic respiration, and 20% from increased photosynthesis). Our study demonstrates the need for joint observational constraints on CO2and CH4biogeochemical processes—and their associated climatic sensitivities—for resolving the sign and magnitude of high‐latitude ecosystem C‐climate feedback in the coming decades. We use in situ measurements to constrain the modeled joint climatic sensitivity of land‐atmosphere CH4and CO2exchangesA continued 1970‐present climate trend leads to positive C‐climate feedback in wet tundra sites but negative feedback in boreal and shrub fen sitesCH4respiration dominates the positive tundra site feedback, CO2respiration dominates the negative boreal and shrub fen sites feedback We use in situ measurements to constrain the modeled joint climatic sensitivity of land‐atmosphere CH4and CO2exchanges A continued 1970‐present climate trend leads to positive C‐climate feedback in wet tundra sites but negative feedback in boreal and shrub fen sites CH4respiration dominates the positive tundra site feedback, CO2respiration dominates the negative boreal and shrub fen sites feedback
- Published
- 2023
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64. Satellite microwave assessment of Northern Hemisphere lake ice phenology from 2002 to 2015.
- Author
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Jinyang Du, Kimball, John S., Duguay, Claude, Youngwook Kim, and Watts, Jennifer D.
- Subjects
ICE on rivers, lakes, etc. ,PHENOLOGY ,RADIOMETERS ,MICROWAVE imaging - Abstract
A new automated method enabling consistent satellite assessment of seasonal lake ice phenology at 5 km resolution was developed for all lake pixels (water coverage ≥90 %) in the Northern Hemisphere using 36.5 GHz H-polarized brightness temperature (T
b ) observations from the Advanced Microwave Scanning Radiometer for EOS and Advanced Microwave Scanning Radiometer 2 (AMSR-E/2) sensors. The lake phenology metrics include seasonal timing and duration of annual ice cover. A moving t test (MTT) algorithm allows for automated lake ice retrievals with daily temporal fidelity and 5 km resolution gridding. The resulting ice phenology record shows strong agreement with available ground-based observations from the Global Lake and River Ice Phenology Database (95.4% temporal agreement) and favorable correlations (R) with alternative ice phenology records from the Interactive Multisensor Snow and Ice Mapping System (R = 0:84 for water clear of ice (WCI) dates; R = 0:41 for complete freeze over (CFO) dates) and Canadian Ice Service (R = 0:86 for WCI dates; R = 0:69 for CFO dates). Analysis of the resulting 12-year (2002-2015) AMSR-E/2 ice record indicates increasingly shorter ice cover duration for 43 out of 71 (60.6 %) Northern Hemisphere lakes examined, with significant (p <0.05) regional trends toward earlier ice melting for only five lakes. Higherlatitude lakes reveal more widespread and larger trends toward shorter ice cover duration than lower-latitude lakes, consistent with enhanced polar warming. This study documents a new satellite-based approach for rapid assessment and regional monitoring of seasonal ice cover changes over large lakes, with resulting accuracy suitable for global change studies. [ABSTRACT FROM AUTHOR]- Published
- 2017
- Full Text
- View/download PDF
65. Mapping Arctic Tundra Vegetation Communities Using Field Spectroscopy and Multispectral Satellite Data in North Alaska, USA.
- Author
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Davidson, Scott J., Santos, Maria J., Sloan, Victoria L., Watts, Jennifer D., Phoenix, Gareth K., Oechel, Walter C., and Zona, Donatella
- Subjects
SPECTRUM analysis ,BOTANY ,CLIMATE change ,REMOTE sensing ,ELECTROMAGNETIC wave absorption - Abstract
The Arctic is currently undergoing intense changes in climate; vegetation composition and productivity are expected to respond to such changes. To understand the impacts of climate change on the function of Arctic tundra ecosystems within the global carbon cycle, it is crucial to improve the understanding of vegetation distribution and heterogeneity at multiple scales. Information detailing the fine-scale spatial distribution of tundra communities provided by high resolution vegetation mapping, is needed to understand the relative contributions of and relationships between single vegetation community measurements of greenhouse gas fluxes (e.g., ∼1 m chamber flux) and those encompassing multiple vegetation communities (e.g., ∼300 m eddy covariance measurements). The objectives of this study were: (1) to determine whether dominant Arctic tundra vegetation communities found in different locations are spectrally distinct and distinguishable using field spectroscopy methods; and (2) to test which combination of raw reflectance and vegetation indices retrieved from field and satellite data resulted in accurate vegetation maps and whether these were transferable across locations to develop a systematic method to map dominant vegetation communities within larger eddy covariance tower footprints distributed along a 300 km transect in northern Alaska. We showed vegetation community separability primarily in the 450-510 nm, 630-690 nm and 705-745 nm regions of the spectrum with the field spectroscopy data. This is line with the different traits of these arctic tundra communities, with the drier, often non-vascular plant dominated communities having much higher reflectance in the 450-510 nm and 630-690 nm regions due to the lack of photosynthetic material, whereas the low reflectance values of the vascular plant dominated communities highlight the strong light absorption found here. High classification accuracies of 92% to 96% were achieved using linear discriminant analysis with raw and rescaled spectroscopy reflectance data and derived vegetation indices. However, lower classification accuracies (∼70%) resulted when using the coarser 2.0 m WorldView-2 data inputs. The results from this study suggest that tundra vegetation communities are separable using plot-level spectroscopy with hand-held sensors. These results also show that tundra vegetation mapping can be scaled from the plot level (<1 m) to patch level (<500 m) using spectroscopy data rescaled to match the wavebands of the multispectral satellite remote sensing. We find that developing a consistent method for classification of vegetation communities across the flux tower sites is a challenging process, given the spatial variability in vegetation communities and the need for detailed vegetation survey data for training and validating classification algorithms. This study highlights the benefits of using fine-scale field spectroscopy measurements to obtain tundra vegetation classifications for landscape analyses and use in carbon flux scaling studies. Improved understanding of tundra vegetation distributions will also provide necessary insight into the ecological processes driving plant community assemblages in Arctic environments. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
66. Surface water inundation in the boreal-Arctic: potential impacts on regional methane emissions
- Author
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Watts, Jennifer D, primary, Kimball, John S, additional, Bartsch, Annett, additional, and McDonald, Kyle C, additional
- Published
- 2014
- Full Text
- View/download PDF
67. UNDERSTANDING HIGH-LATITUDE METHANE IN A WARMING CLIMATE.
- Author
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Miller, Scot M., Taylor, Meghan A., and Watts, Jennifer D.
- Published
- 2018
68. Improved classification of conservation tillage adoption using high temporal and synthetic satellite imagery
- Author
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Watts, Jennifer D., primary, Powell, Scott L., additional, Lawrence, Rick L., additional, and Hilker, Thomas, additional
- Published
- 2011
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- View/download PDF
69. Monitoring of cropland practices for carbon sequestration purposes in north central Montana by Landsat remote sensing
- Author
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Watts, Jennifer D., primary, Lawrence, Rick L., additional, Miller, Perry R., additional, and Montagne, Cliff, additional
- Published
- 2009
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- View/download PDF
70. THE POTENTIAL FOR CARBON SEQUESTRATION ON DEGRADED LANDS WITHIN NORTH CENTRAL MONTANA
- Author
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Watts, Jennifer D., primary
- Published
- 2009
- Full Text
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71. Author Correction: Large loss of CO2in winter observed across the northern permafrost region
- Author
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Natali, Susan M., Watts, Jennifer D., Rogers, Brendan M., Potter, Stefano, Ludwig, Sarah M., Selbmann, Anne-Katrin, Sullivan, Patrick F., Abbott, Benjamin W., Arndt, Kyle A., Birch, Leah, Björkman, Mats P., Bloom, A. Anthony, Celis, Gerardo, Christensen, Torben R., Christiansen, Casper T., Commane, Roisin, Cooper, Elisabeth J., Crill, Patrick, Czimczik, Claudia, Davydov, Sergey, Du, Jinyang, Egan, Jocelyn E., Elberling, Bo, Euskirchen, Eugenie S., Friborg, Thomas, Genet, Hélène, Göckede, Mathias, Goodrich, Jordan P., Grogan, Paul, Helbig, Manuel, Jafarov, Elchin E., Jastrow, Julie D., Kalhori, Aram A. M., Kim, Yongwon, Kimball, John S., Kutzbach, Lars, Lara, Mark J., Larsen, Klaus S., Lee, Bang-Yong, Liu, Zhihua, Loranty, Michael M., Lund, Magnus, Lupascu, Massimo, Madani, Nima, Malhotra, Avni, Matamala, Roser, McFarland, Jack, McGuire, A. David, Michelsen, Anders, Minions, Christina, Oechel, Walter C., Olefeldt, David, Parmentier, Frans-Jan W., Pirk, Norbert, Poulter, Ben, Quinton, William, Rezanezhad, Fereidoun, Risk, David, Sachs, Torsten, Schaefer, Kevin, Schmidt, Niels M., Schuur, Edward A. G., Semenchuk, Philipp R., Shaver, Gaius, Sonnentag, Oliver, Starr, Gregory, Treat, Claire C., Waldrop, Mark P., Wang, Yihui, Welker, Jeffrey, Wille, Christian, Xu, Xiaofeng, Zhang, Zhen, Zhuang, Qianlai, and Zona, Donatella
- Abstract
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
- Published
- 2019
- Full Text
- View/download PDF
72. Global Satellite Retrievals of the Near-Surface Atmospheric Vapor Pressure Deficit from AMSR-E and AMSR2.
- Author
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Du, Jinyang, Kimball, John S., Reichle, Rolf H., Jones, Lucas A., Watts, Jennifer D., and Kim, Youngwook
- Subjects
TELECOMMUNICATION satellites ,VAPOR pressure ,EVAPOTRANSPIRATION ,METEOROLOGICAL stations ,STANDARD deviations - Abstract
Near-surface atmospheric Vapor Pressure Deficit (VPD) is a key environmental variable affecting vegetation water stress, evapotranspiration, and atmospheric moisture demand. Although VPD is readily derived from in situ standard weather station measurements, more spatially continuous global observations for regional monitoring of VPD are lacking. Here, we document a new method to estimate daily (both a.m. and p.m.) global land surface VPD at a 25-km resolution using a satellite passive microwave remotely sensed Land Parameter Data Record (LPDR) derived from the Advanced Microwave Scanning Radiometer (AMSR) sensors. The AMSR-derived VPD record shows strong correspondence (correlation coefficient ≥ 0.80,
p -value < 0.001) and overall good performance (0.48 kPa ≤ Root Mean Square Error ≤ 0.69 kPa) against independent VPD observations from the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) data. The estimated AMSR VPD retrieval uncertainties vary with land cover type, satellite observation time, and underlying LPDR data quality. These results provide new satellite capabilities for global mapping and monitoring of land surface VPD dynamics from ongoing AMSR2 operations. Overall good accuracy and similar observations from both AMSR2 and AMSR-E allow for the development of climate data records documenting recent (from 2002) VPD trends and potential impacts on vegetation, land surface evaporation, and energy budgets. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
73. Large loss of CO 2 in winter observed across the northern permafrost region.
- Author
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Natali SM, Watts JD, Rogers BM, Potter S, Ludwig SM, Selbmann AK, Sullivan PF, Abbott BW, Arndt KA, Birch L, Björkman MP, Bloom AA, Celis G, Christensen TR, Christiansen CT, Commane R, Cooper EJ, Crill P, Czimczik C, Davydov S, Du J, Egan JE, Elberling B, Euskirchen ES, Friborg T, Genet H, Göckede M, Goodrich JP, Grogan P, Helbig M, Jafarov EE, Jastrow JD, Kalhori AAM, Kim Y, Kimball J, Kutzbach L, Lara MJ, Larsen KS, Lee BY, Liu Z, Loranty MM, Lund M, Lupascu M, Madani N, Malhotra A, Matamala R, McFarland J, McGuire AD, Michelsen A, Minions C, Oechel WC, Olefeldt D, Parmentier FW, Pirk N, Poulter B, Quinton W, Rezanezhad F, Risk D, Sachs T, Schaefer K, Schmidt NM, Schuur EAG, Semenchuk PR, Shaver G, Sonnentag O, Starr G, Treat CC, Waldrop MP, Wang Y, Welker J, Wille C, Xu X, Zhang Z, Zhuang Q, and Zona D
- Abstract
Recent warming in the Arctic, which has been amplified during the winter
1-3 , greatly enhances microbial decomposition of soil organic matter and subsequent release of carbon dioxide (CO2 )4 . However, the amount of CO2 released in winter is highly uncertain and has not been well represented by ecosystem models or by empirically-based estimates5,6 . Here we synthesize regional in situ observations of CO2 flux from arctic and boreal soils to assess current and future winter carbon losses from the northern permafrost domain. We estimate a contemporary loss of 1662 Tg C yr-1 from the permafrost region during the winter season (October through April). This loss is greater than the average growing season carbon uptake for this region estimated from process models (-1032 Tg C yr-1 ). Extending model predictions to warmer conditions in 2100 indicates that winter CO2 emissions will increase 17% under a moderate mitigation scenario-Representative Concentration Pathway (RCP) 4.5-and 41% under business-as-usual emissions scenario-RCP 8.5. Our results provide a new baseline for winter CO2 emissions from northern terrestrial regions and indicate that enhanced soil CO2 loss due to winter warming may offset growing season carbon uptake under future climatic conditions.- Published
- 2019
- Full Text
- View/download PDF
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