A new approach of using only the north component of gravity change from Gravity Recovery and Climate Experiment (GRACE) data reveals that a substantially higher spatial resolution of the observed seismic deformation following the 2011 Tohoku earthquake is achievable at 333 km or longer. Here we show that GRACE-observed north component of gravity change, À17.6 ± 1.1 μGal, and the corresponding gravity gradient change, e.g., Txz at 1.25 ± 0.09 mEötvös, agree well with seismic/GPS model predictions. Localized Slepian spectrum analysis further confirms that the GRACE gravity and gravity gradient changes agree well with seismic model spectra and have powers up to the limit of the GRACE solution complete to spherical harmonic degree 60. Using the gravity observations for the fault parameter inversion via simulated annealing algorithm, we show that the estimated slip orientation and centroid location are different from GPS/seismic solutions and potentially due to the additional offshore constraint from GRACE data.

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ArcticDEM is an open-access collection of high-resolution (2 m), repeat, digital surface models, created from submeter resolution, stereoscopic satellite imagery, covering the entire Arctic landmass. To demonstrate the application of this powerful new data source for measuring Earth surface change, we measure elevation changes resulting from the 2012-2013 eruption of Tolbachik volcano in Kamchatka, Russia, which reveals detailed variations in lava thickness. We estimate a total lava volume of 0.573 ± 0.007 km 3 emplaced over an area of 45.8 km 2 at a mean rate of 21 m 3 /s. Furthermore, the size and timing of eruptions over the past 2,000 years support the hypothesis that the combined eruptions of 1976-77 and 2012-2013 ejected much or all of the magma stored over the previous~1,000 years, so that a multicentury repose is expected. The approaches developed in this study will guide future, expanded applications of ArcticDEM to mapping terrain change.

ArcticDEM is a collection of 2‐m resolution, repeat digital surface models created from stereoscopic satellite imagery. To demonstrate the potential of ArcticDEM for measuring river stages and discharges, we estimate river surface heights along a reach of Tanana River near Fairbanks, Alaska, by the precise detection of river shorelines and mapping of shorelines to land surface elevation. The river height profiles over a 15‐km reach agree with in situ measurements to a standard deviation less than 30 cm. The time series of ArcticDEM‐derived river heights agree with the U.S. Geological Survey gage measurements with a standard deviation of 32 cm. Using the rating curve for that gage, we obtain discharges with a validation accuracy (root‐mean‐square error) of 234 m3/s (23% of the mean discharge). Our results demonstrate that ArcticDEM can accurately measure spatial and temporal variations of river surfaces, providing a new and powerful data set for hydrologic analysis.

To investigate the combustion performance of RP-3 aviation kerosene, n-decane was chosen as a one-component surrogate fuel. Sensitivity analysis and the reaction-path analysis method were used to simplify the detailed reaction mechanism of n-decane, and a simplified mechanism including 36 species and 62 elementary reaction steps was obtained. A Bunsen burner for the combustion of premixed, pre-evaporated RP-3 aviation kerosene was designed to verify the simplified mechanism, and the temperature and gas component concentrations in the axial and radial directions at different heights were measured. The combustion process of the premixed, pre-evaporated RP-3 aviation kerosene in the Bunsen burner was also simulated on the basis of the simplified mechanism, and the numerical results were compared to the experimental data. The results show that the simulated distributions of the temperature and O2 concentration are in good agreement with the experimental data in all cases. In addition, the simulated distribution of the CO2 concentration is in general agreement with the experimental data. Thus, the simplified mechanism can accurately predict the trend in the CO2 concentration near the outer flame. Therefore, n-decane can be used as a one-component surrogate fuel for RP-3 aviation kerosene, and the simplified mechanism of n-decane with 36 species and 62 elementary reaction steps can accurately predict the combustion performance of RP-3 aviation kerosene over a wide range of conditions.

Climate change will have a significant effect on crop water requirement (ETc). The spatial and temporal variations of water requirement of maize under climate change are essential elements when conducting a global water security assessment. In this paper, annual reference crop evapotranspiration (ET0) and the crop water requirement of maize were calculated by the single crop coefficient method. The crop water surplus deficit index (CWSDI) and coupling degree of ETc and effective precipitation (Pe) were calculated to analyze the relationship between ETc, ET0, and Pe. The result shows that maize average annual ET0, ETc, and precipitation were 552.97, 383.05, and 264.97 mm, respectively. Moreover, ET0, ETc, and Pe decreased by 3.28, 2.56, and 6.25 mm every decade from 1960 to 2015. The ETc decreased less than Pe did, which led to the decreasing of both CWSDI and the coupling degree of ETc and Pe. The tendency of ET0, ETc decreased first and then increased, while Pe and CWSDI increased first and then decreased, from west to east of the Heilongjiang Province. In addition, the highest ET0, ETc, and lowest CWSDI and Pe were found in the western part of Heilongjiang Province. This study indicated that even though the water deficit in the western region was alleviated and the water deficit in the eastern region grew gradually serious from 1960 to 2015, the drought situation in western Heilongjiang Province should still be taken seriously.

The innovative processing of Gravity Recovery And Climate Experiment (GRACE) data using only the north component of gravity change and its corresponding gravity gradient changes allows the enhancement of the spatial resolution for coseismic deformation signals. Here, we report the study of five undersea earthquakes using this technique: the 2004 Sumatra-Andaman earthquake, the 2007 Bengkulu earthquake, the 2010 Maule, Chile earthquake, the 2011 Tohoku earthquake, and the 2012 Indian Ocean earthquakes.By using the high spherical harmonic degree (up to degree 96) data products and the associated GRACE data processing techniques, the retrieved north component of gravity change is up to -34±1.4 μGal for the 2004 Sumatra-Andaman earthquake, which illustrates by far the highest amplitude of the coseismic signal retrieved from satellite gravimetry among previous studies. We creatively apply the localized spectral analysis as an efficient method to empirically determine the practical spherical harmonic truncation degree. By combining least squares adjustment with the simulated annealing algorithm, point source parameters are estimated, which demonstrates the unique constraint on source model from GRACE data compared to other data sources. For the 2004 Sumatra-Andaman earthquake, GRACE data produce a shallower centroid depth (9.1 km), as compared to the depth (28.3 km) from GPS data. For the 2011 Tohoku earthquake, the GRACE-estimated centroid location is southwest of the GPS/seismic solutions, and the slip orientation is about 10° clockwise from the published GPS/seismic slip models. We concluded that these differences demonstrate the additional and critical offshore constraint by GRACE on source parameters, as compared to GPS/seismic data.We acknowledge Frederik Simons, Princeton University, for providing his software on localized spectral analysis, and useful discussions. We thank Jeff Freymueller, University of Alaska, for his helpful suggestions and comments. We thank Shengji Wei, Han Yue, David Sandwell, and authors of the eQuake-RC, http://equake-rc.info, for providing various coseismic and postseismic slip models. We would like to thank Seiichi Miura who generously shares the velocity structure at the Japan Trench subduction zone.

Many studies have found that damming a river can change downstream hydrology, sediment transport, channel morphology, and fish habitat. However, little is known about river dam effects on downstream riparian wetland dynamics and their quantitative relationship with hydrological alterations. In this study, hydrological time series and wetland distribution data spanning nearly 40 years (1978–2016) before and after the construction of a large dam in 2005 across the Nenjiang River in Northeast China were used to reveal the impact of dam on the downstream discharge regime and wetland degradation. Hydro-statistical and stepwise multiple regression analyses were performed to quantify the relationship of riparian wetland area with a metrics of 33 hydrological indicators. Dam construction caused decline in peak discharge, flood frequency, and magnitude. Moreover, 150 km riparian wetlands along the downstream of the dam was largely reduced. The count and duration of high flow pulses, 1-day maximum, and date of maximum discharge changed significantly after the dam construction. The hydrological changes have made a significant contribution to the 44% reduction in riparian wetlands following the dam construction. Our results indicated that hydrological alterations caused by dam regulation led to the area reduction of downstream riparian wetlands. The findings provide relevant information for developing best dam operation practices to protect and restore downstream wetland ecosystems.