Earth and Space Science

Journal Information
ISSN / EISSN : 23335084 / 23335084
Current Publisher: American Geophysical Union (AGU) (10.1029)
Former Publisher: Wiley (10.1002)
Total articles ≅ 381
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M. Snow, J. Machol, R. Viereck, T. Woods, M. Weber, D. Woodraska, J. Elliott
Earth and Space Science; doi:10.1029/2019ea000652

Abstract:The Magnesium II core–wing ratio (also known as the Mg II index) is a widely used proxy for ultraviolet solar spectral irradiance variability. We have developed a new algorithm for calculating this index from the SOLar‐STellar Irradiance Comparison Experiment (SOLSTICE) on the SOlar Radiation and Climate Experiment (SORCE). The new method uses weighted sums of the core and wing regions of the spectrum calculated from the daily level three high‐resolution spectrum. We also describe a new method of scaling the results in order to compare to other measurements. This new method scales each dataset to a standard spectral resolution rather than scaling to other datasets during periods of overlapping measurements. Finally, we quantify the effect of long‐term instrument degradation on the Mg II index. In the case of SORCE SOLSTICE, using uncorrected data would produce an error of less than 0.6% of the solar cycle amplitude over a decade.
Matthew T. Deland, Greg Kopp, David B. Considine
Earth and Space Science; doi:10.1029/2019ea000773

Abstract:Solar irradiance represents the dominant energy source heating the Earth's atmosphere and climate. Both total solar irradiance (TSI) and spectral solar irradiance (SSI) vary over the 11‐year solar cycle. Characterizing these variations with sufficient accuracy for climate studies over multi‐decadal timescales requires a combination of multiple observational data sets, solar activity proxies, and irradiance models. NASA established the Solar Irradiance Science Team (SIST) program in 2015 to pursue this goal using a range of technical approaches. This paper summarizes those investigations, whose results are reported in separate papers in a special section of this journal.
Xueheng Shi, Colin Gallagher
Earth and Space Science; doi:10.1029/2018ea000451

Abstract:Examples of cyclic (periodic) behavior in geophysical data abound. In many cases the primary period is known, such as in daily measurements of rain, temperature, and sea level. However, many time series of measurements contain cycles of unknown or varying length. We consider the problem of estimating the unknown period in a time series. We review the basic methods, {compare their performance through a simulation study using observed sea level data, apply them to an astronomical} data set, and discuss generalizations of the methods.
N. W. Watkins
Earth and Space Science; doi:10.1029/2019ea000598

Abstract:I survey and illustrate the main time series models that Mandelbrot introduced into time series analysis in the 1960s and 1970s. I focus particularly on the members of the additive fractional stable family including Lévy flights and fractional Brownian motion (fBm), noting some of the less well‐known aspects of this family, such as the cases when the self‐similarity exponent H and the Hurst exponent J differ. I briefly discuss the role of multiplicative models in modelling the physics of cascades. I then recount the still little‐known story of Mandelbrot's work on fractional renewal models in the late 1960s, explaining how these differ from their more familiar fBm counterpart, and form a “missing link” between fBm and the problem of random changepoints. I conclude by highlighting the frontier problem of damped fractional models.
F.J. Gordillo‐Vázquez, F.J. Pérez‐Invernón, H. Huntrieser, A.K. Smith
Earth and Space Science; doi:10.1029/2019ea000873

S.F. Tebbens
Earth and Space Science; doi:10.1029/2019ea000662

Abstract:This paper is a review of landslide and rockfall studies of hilly and mountainous regions worldwide. Repositories of landslide inventories are available online [e.g., Tanyaş et al., 2017]. The landslide inventories predominantly record deep‐seated, fast‐moving, landslides, generally triggered by an earthquake or rainfall event, and such landslides are the primary focus of this review. The size‐frequency distributions of landslides and rockfalls are well‐described by a power function for larger (generally for the largest two orders of magnitude) of event sizes [e.g., Malamud et al., 2004; Tanyaş et al., 2018]. Smaller event sizes are under‐represented by the power function that describes the larger events [e.g., Stark and Hovius, 2001]. The deviation from a power function at smaller sizes is arguably not a simple detection issue and possible explanations include lack of temporal resolution in sampling, and amalgamation of smaller events into larger events when mapping [e.g., Tanyaş et al., 2019]. Self‐organized criticality (SOC) models and cellular automata models have been developed that replicate the power scaling behavior [e.g, Hergarten, 2013]. The SOC models are alluring in their simplicity, but have shortcomings such as failing to recreate the same scaling exponent as observed in nature [e.g, Hergarten, 2002]. Parameterized cellular automata models include one or more relevant variables that affect shear stress in the surface materials and come closer to replicating the scaling exponents observed for natural systems [e.g, D’Ambrosio et al., 2003]. Mechanical models have also successfully replicated the observed power scaling [e.g., Jeandet et al., 2019].
Xinming Tang, Junfeng Xie, Ren Liu, Genghua Huang, Chenguang Zhao, Ying Zhen, Hongzhao Tang, Xianhui Dou
Earth and Space Science; doi:10.1029/2019ea000777

Abstract:The Gao Fen 7 (GF‐7) satellite is China's first submeter, high‐resolution Earth observation and remote sensing satellite for natural resource monitoring, land surveying and other industrial applications in China. The GF‐7 laser altimeter system is the successor of the ZiYuan3‐02 (ZY3‐02 satellite) laser altimeter. The key objective of the GF‐7 laser altimetry system is to provide high‐precision ground elevation control points that assist in optical imaging to achieve 1:10000 mapping in China. This paper introduces the GF‐7 laser altimeter system payload specifications, mission objectives, in‐orbit calibration plan, data products and service policy. In the future, the GF‐7 laser altimeter system will also serve multidisciplinary and professional applications through its precise elevation measurement capabilities. In addition, it will play a vital role in Earth observation, climate change monitoring, and environmental protection.
O. Coddington, J. Lean, P. Pilewskie, M. Snow, E. Richard, G. Kopp, C. Lindholm, M. Deland, S. Marchenko, M. Haberreiter, et al.
Earth and Space Science; doi:10.1029/2019ea000693

Abstract:The Earth system responds to solar variability on a wide range of timescales. Knowledge of total solar irradiance (TSI) and solar spectral irradiance (SSI) spanning minutes to centuries is needed by scientists studying a broad array of research applications. For these purposes, the NOAA National Centers for Environmental Information (NCEI) Climate Data Record Program established the Solar Irradiance Climate Data Record (CDR). Version 2 of the Naval Research Laboratory's (NRL) solar variability models that are derived from and demonstrate consistency with irradiance observations specify TSI and SSI for the Solar Irradiance CDR. We establish the veracity of the NRL models on the timescales and over the wavelength range for which the Sun is known to vary and, thereby, specify the utility of these models. Through comparisons with irradiance observations and independent models, we validate NRLTSI2 estimates of TSI on solar‐rotational (~ 27‐day), solar‐cycle (~ 11‐year), and multi‐decadal (spacecraft‐era) variability timescales. Similarly, we validate NRLSSI2 estimates of SSI rotational variability in the ultraviolet through the mid‐visible spectrum. Validation of NRLSSI2 estimates at longer wavelengths, particularly in the near‐infrared, and for the full spectrum at solar cycle timescales and longer is not possible with the current observational record due to instrumental noise and instrument instability. We identify where key new datasets, such as observations from the Total and Spectral Solar Irradiance Sensor (TSIS‐1), are expected to provide a fuller understanding of total and spectral solar irradiance variability on multiple timescales.
Han Wang, Meiru Zhao, Leiku Yang, Pei Liu, Weibing Du, Xiaobing Sun
Earth and Space Science; doi:10.1029/2019ea000903

Abstract:North China has one of the world's largest densities of atmospheric aerosol particles. The surface and aerosol properties in this area are complex. We evaluated the spectral relationship between surface polarized reflectances (SPR) and introduced specific types of aerosol to improve the remote sensing of aerosols in this area. First, we searched for low‐aerosol‐loading areas (clean areas) based on Moderate resolution Imaging Spectroradiometer (MODIS) measurements between 2009 and 2011. Then, we recalculated the spectral relationships of SPR from corrected Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar (PARASOL) measurements. Finally, the re‐derived relationships and aerosol clustering modes for East Asia were applied using the adaptive land‐atmospheric decoupling (ALAD) algorithm to retrieve aerosol optical depth (AOD). We collected 914 PARASOL measured samples matched the site data of the aerosol robotic network (AERONET), within a wide AOD range between 2005 and 2013. The AOD trends from AERONET and PARASOL were similar. The slope of the regression line was 0.836, with a low intercept (0.032) and high correlation coefficient (0.854), and 53.6% of the retrieved AODs were within the range of the expected error (EE). Compared with the MODIS daily AOD, we found that the variation in PARASOL results displayed a smooth tendency with the increase of AODs. The 914 sampling points were classified according to location and season to identify any discrepancies in the retrieved results. It was found that vegetation surfaces were responsible for most of the uncertainty due to their seasonal characteristics.
ZhengJie Li, Wendell W. Walters, Meredith G. Hastings, Yanlin Zhang, Linlin Song, Dongwei Liu, Wenqi Zhang, Yuepeng Pan, Pingqing Fu, Yunting Fang
Earth and Space Science; doi:10.1029/2019ea000759

Abstract:Nitrogen stable isotope composition (δ15N) of nitrate (NO3‐) deposition can aid in source apportionment of its precursor emissions, nitrogen oxides (NOx), with implications in mitigation policy to address serious air pollution. However, potential δ15N fractionation during atmospheric NO3‐ formation may hinder accurate quantification of NOx contributions. Previously, NOx photochemical reactions have been suggested to be the dominant δ15N fractionation process in NO3‐ formation. Here, we have quantified the potential fractionation effects associated with NOx photochemical reactions based upon δ15N‐NO3‐ measured in one year of daily‐based bulk deposition samples in Shenyang, a megacity with distinct seasonal fossil fuel combustion in northeastern China. The mean δ15N was 0.9 ± 4.0‰ and ranged from ‐4.9 to 8.3‰, with the lowest and highest values observed during summer and winter, respectively. Calculated NOx photochemical equilibrium fractionation may account for up to 42% of the observed seasonal δ15N change in NO3‐ deposition. However, the relative NOx source contribution trends, estimated based upon a δ15N Bayesian mixing model, were insensitive to NOx photochemical fractionation considerations. Overall, NOx source partitioning based upon averaged year‐long δ15N of bulk NO3‐ deposition estimated the following relative trend in NOx emission sources: coal combustion > biomass burning = vehicle emissions >> soil emissions. Seasonally, the increase of coal combustion emissions from summer to winter drives the seasonality of δ15N in NO3‐ deposition, indicating a necessity to control NOx emissions from coal combustion to improve wintertime air quality.