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231 results on '"Steele-Dunne, Susan"'

2. Achieving Breakthroughs in Global Hydrologic Science by Unlocking the Power of Multisensor, Multidisciplinary Earth Observations

Author

Durand, Michael, Barros, Ana, Dozier, Jeff, Adler, Robert, Cooley, Sarah, Entekhabi, Dara, Forman, Barton A, Konings, Alexandra G, Kustas, William P, Lundquist, Jessica D, Pavelsky, Tamlin M, Rodell, Matthew, and Steele‐Dunne, Susan

Subjects
Earth Sciences, Atmospheric Sciences, remote sensing, hydrology, Climate change science, Geology, Physical geography and environmental geoscience
Abstract

Abstract: Over the last half century, remote sensing has transformed hydrologic science. Whereas early efforts were devoted to observation of discrete variables, we now consider spaceborne missions dedicated to interlinked global hydrologic processes. Furthermore, cloud computing and computational techniques are accelerating analyses of these data. How will the hydrologic community use these new resources to better understand the world's water and related challenges facing society? In this commentary, we suggest that optimizing the benefits of remote sensing for advancing hydrologic research will happen by integrating multidisciplinary and multisensor data, leveraging commercial satellite measurements, and employing data assimilation, cloud computing, and machine learning. We provide several recommendations to these ends.

Published
2021

3. Detecting forest response to droughts with global observations of vegetation water content

Author

Konings, Alexandra G, Saatchi, Sassan S, Frankenberg, Christian, Keller, Michael, Leshyk, Victor, Anderegg, William RL, Humphrey, Vincent, Matheny, Ashley M, Trugman, Anna, Sack, Lawren, Agee, Elizabeth, Barnes, Mallory L, Binks, Oliver, Cawse‐Nicholson, Kerry, Christoffersen, Bradley O, Entekhabi, Dara, Gentine, Pierre, Holtzman, Nataniel M, Katul, Gabriel G, Liu, Yanlan, Longo, Marcos, Martinez‐Vilalta, Jordi, McDowell, Nate, Meir, Patrick, Mencuccini, Maurizio, Mrad, Assaad, Novick, Kimberly A, Oliveira, Rafael S, Siqueira, Paul, Steele‐Dunne, Susan C, Thompson, David R, Wang, Yujie, Wehr, Richard, Wood, Jeffrey D, Xu, Xiangtao, and Zuidema, Pieter A

Subjects
Climate Action, Droughts, Ecosystem, Forests, Plant Leaves, Trees, Xylem, drought response, drought-induced tree mortality, microwave remote sensing, pressure-volume, vegetation optical depth, vegetation water content, water potential, Environmental Sciences, Biological Sciences, Ecology
Abstract

Droughts in a warming climate have become more common and more extreme, making understanding forest responses to water stress increasingly pressing. Analysis of water stress in trees has long focused on water potential in xylem and leaves, which influences stomatal closure and water flow through the soil-plant-atmosphere continuum. At the same time, changes of vegetation water content (VWC) are linked to a range of tree responses, including fluxes of water and carbon, mortality, flammability, and more. Unlike water potential, which requires demanding in situ measurements, VWC can be retrieved from remote sensing measurements, particularly at microwave frequencies using radar and radiometry. Here, we highlight key frontiers through which VWC has the potential to significantly increase our understanding of forest responses to water stress. To validate remote sensing observations of VWC at landscape scale and to better relate them to data assimilation model parameters, we introduce an ecosystem-scale analog of the pressure-volume curve, the non-linear relationship between average leaf or branch water potential and water content commonly used in plant hydraulics. The sources of variability in these ecosystem-scale pressure-volume curves and their relationship to forest response to water stress are discussed. We further show to what extent diel, seasonal, and decadal dynamics of VWC reflect variations in different processes relating the tree response to water stress. VWC can also be used for inferring belowground conditions-which are difficult to impossible to observe directly. Lastly, we discuss how a dedicated geostationary spaceborne observational system for VWC, when combined with existing datasets, can capture diel and seasonal water dynamics to advance the science and applications of global forest vulnerability to future droughts.

Published
2021

5. Soil hydrology in the Earth system

Author

Vereecken, Harry, Amelung, Wulf, Bauke, Sara L., Bogena, Heye, Brüggemann, Nicolas, Montzka, Carsten, Vanderborght, Jan, Bechtold, Michel, Blöschl, Günter, Carminati, Andrea, Javaux, Mathieu, Konings, Alexandra G., Kusche, Jürgen, Neuweiler, Insa, Or, Dani, Steele-Dunne, Susan, Verhoef, Anne, Young, Michael, and Zhang, Yonggen

Published
2022
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22. Seven Frozen Trees in Sodankyla: Relating ASCAT slope to water and carbon processes over a Boreal forest using in-situ, model and reanalysis data

Author

Vreugdenhil, Mariette, primary, Steele-Dunne, Susan, additional, Shan, Xu, additional, Kaminski, Thomas, additional, Aurela, Mika, additional, Bueechi, Emanuel, additional, Dorigo, Wouter, additional, Knorr, Wolfgang, additional, Lemmetyinen, Juha, additional, Rodriguez-Fernandez, Nemesio, additional, Scholze, Marko, additional, Thum, Tea, additional, and Williams, Mathew, additional

Published
2023
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25. Ground-Based Soil Moisture Retrieval Using the Correlation Between Dual-Polarization GNSS-R Interference Patterns

Author

El Hajj, Marcel M., Steele-Dunne, Susan C., Almashharawi, Samer K., Tian, Xuemeng, Johansen, Kasper, Camargo, Omar A. Lopez, Amezaga-Sarries, Adria, Mas-Vinolas, Andreu, and McCabe, Matthew F.

Abstract

Soil moisture (SM) is an important state variable in land surface models. Here, we investigate the potential of a ground-based global navigation satellite system receiver with two linearly polarized antennas that measure the interference power (IP) of direct and reflected signals in horizontal polarization (H-pol) and vertical polarization (V-pol) to estimate SM. The coefficient of determination between the IP waveforms at H-pol and V-pol ( $\boldsymbol {R}_{ \boldsymbol {v}\mathbf {/} \boldsymbol {h}}^{\mathbf {2}}$ ) was used as a predictor of SM. A coherent specular reflection model was employed to first explore the relationship between $\boldsymbol {R}_{ \boldsymbol {v}\mathbf {/} \boldsymbol {h}}^{\mathbf {2}}$ and SM for different values of soil roughness. That relationship was subsequently applied to estimate SM from $\boldsymbol {R}_{ \boldsymbol {v}\mathbf {/} \boldsymbol {h}}^{\mathbf {2}}$ determined from global positioning system (GPS) signals acquired continuously by a ground-based receiver between May and December 2022 for an area with very smooth bare soil. The results show that the proposed method can estimate the SM of the upper 10-cm layer with high accuracy (with a root-mean-square error (RMSE) of approximately 1.5 vol.%) and demonstrate the potential of the ground-based IP technique as a practical system solution for proximal remote sensing of SM over bare soils.

Published
2024
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30. Sentinel-1 Backscatter Time Series for Characterization of Evapotranspiration Dynamics over Temperate Coniferous Forests

Author

Müller, Marlin, Dubois, Clémence, Jagdhuber, Thomas, Hellwig, Florian M., Pathe, Carsten, Schmullius, C., and Steele-Dunne, Susan C.

Subjects
remote sensing, MODIS, Evapotranspiration, ddc:550, single spectrum analysis, Sentinel-1, Forest, time series, backscatter, thuringia, coniferous forests, SAR
Abstract

Forests’ ecosystems are an essential part of the global carbon cycle with vast carbon storage potential. These systems are currently under external pressures showing increasing change due to climate change. A better understanding of the biophysical properties of forests is, therefore, of paramount importance for research and monitoring purposes. While there are many biophysical properties, the focus of this study is on the in-depth analysis of the connection between the C-band Copernicus Sentinel-1 SAR backscatter and evapotranspiration (ET) estimates based on in situ meteorological data and the FAO-based Penman–Monteith equation as well as the well-established global terrestrial ET product from the Terra and Aqua MODIS sensors. The analysis was performed in the Free State of Thuringia, central Germany, over coniferous forests within an area of 2452 km2, considering a 5-year time series (June 2016–July 2021) of 6- to 12-day Sentinel-1 backscatter acquisitions/observations, daily in situ meteorological measurements of four weather stations as well as an 8-day composite of ET products of the MODIS sensors. Correlation analyses of the three datasets were implemented independently for each of the microwave sensor’s acquisition parameters, ascending and descending overpass direction and co- or cross-polarization, investigating different time series seasonality filters. The Sentinel-1 backscatter and both ET time series datasets show a similar multiannual seasonally fluctuating behavior with increasing values in the spring, peaks in the summer, decreases in the autumn and troughs in the winter months. The backscatter difference between summer and winter reaches over 1.5 dB, while the evapotranspiration difference reaches 8 mm/day for the in situ measurements and 300 kg/m2/8-day for the MODIS product. The best correlation between the Sentinel-1 backscatter and both ET products is achieved in the ascending overpass direction, with datasets acquired in the late afternoon, and reaches an R2-value of over 0.8. The correlation for the descending overpass direction reaches values of up to 0.6. These results suggest that the SAR backscatter signal of coniferous forests is sensitive to the biophysical property evapotranspiration under some scenarios.

Published
2022

34. An Agenda for Land Data Assimilation Priorities: Realizing the Promise of Terrestrial Water, Energy, and Vegetation Observations From Space

Author

Kumar, Sujay, primary, Kolassa, Jana, additional, Reichle, Rolf, additional, Crow, Wade, additional, de Lannoy, Gabrielle, additional, de Rosnay, Patricia, additional, MacBean, Natasha, additional, Girotto, Manuela, additional, Fox, Andy, additional, Quaife, Tristan, additional, Draper, Clara, additional, Forman, Barton, additional, Balsamo, Gianpaolo, additional, Steele‐Dunne, Susan, additional, Albergel, Clement, additional, Bonan, Bertrand, additional, Calvet, Jean‐Christophe, additional, Dong, Jianzhi, additional, Liddy, Hannah, additional, and Ruston, Benjamin, additional

Published
2022
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35. Perspective on satellite-based land data assimilation to estimate water cycle components in an era of advanced data availability and model sophistication

Author

De Lannoy, Gabriëlle J. M., primary, Bechtold, Michel, additional, Albergel, Clément, additional, Brocca, Luca, additional, Calvet, Jean-Christophe, additional, Carrassi, Alberto, additional, Crow, Wade T., additional, de Rosnay, Patricia, additional, Durand, Michael, additional, Forman, Barton, additional, Geppert, Gernot, additional, Girotto, Manuela, additional, Hendricks Franssen, Harrie-Jan, additional, Jonas, Tobias, additional, Kumar, Sujay, additional, Lievens, Hans, additional, Lu, Yang, additional, Massari, Christian, additional, Pauwels, Valentijn R. N., additional, Reichle, Rolf H., additional, and Steele-Dunne, Susan, additional

Published
2022
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