Journal Earth and Space Science-
Earth and Space Science; doi:10.1029/2019ea000624
Abstract:The stability and longevity of the Ozone Monitoring Instrument (OMI), flying on board the (active) Aura Earth‐observing satellite since July 2004, facilitates creation of accurate, long‐term record of relative (normalized to a solar minimum) solar spectral irradiances (SSI). Here we discuss technical details of the most recent version (V3) of the SSI product that provides ~daily measurements for the period July 2006 ‐ April 2018 in the 265‐500 nm domain with average 0.5 nm resolution. We compare OMI SSIs with concurrent independent observations and model estimates. The short‐term (solar rotational cycle) observations and model predictions mostly agree to ~0.1‐0.2% in the UV domain, with an excellent, down to ~0.01% agreement in the visible range. The long‐term (solar cycle) comparisons pose more challenges in the UV domain, where the differences between observations and models frequently exceed the rather conservative ~ 0.1% (both point‐to‐point and long‐term) OMI uncertainties. In the visible range, these differences gradually diminish to < 0.05%, yet again pointing to reliability and robustness of the amassed SSI data in this domain.
Earth and Space Science; doi:10.1029/2019ea000658
Earth and Space Science; doi:10.1029/2019ea000655
Abstract:In the past years, large particle‐physics experiments have shown that muon rate variations detected in underground laboratories are sensitive to regional, middle‐atmosphere temperature variations. Potential applications include tracking short‐term atmosphere dynamics, such as Sudden Stratospheric Warmings. We report here that such sensitivity is not only limited to large surface detectors under high‐opacity conditions. We use a portable muon detector conceived for muon tomography for geophysical applications and we study muon rate variations observed over one year of measurements at the Mont Terri Underground Rock Laboratory, Switzerland (opacity of ∼700 meter water equivalent). We observe a direct correlation between middle‐atmosphere seasonal temperature variations and muon rate. Muon rate variations are also sensitive to the abnormal atmosphere heating in January‐February 2017, associated to a Sudden Stratospheric Warming. Estimates of the effective temperature coefficient for our particular case agree with theoretical models and with those calculated from large neutrino experiments under comparable conditions. Thus, portable muon detectors may be useful to 1) study seasonal and short‐term middle atmosphere dynamics, especially in locations where data is lacking such as mid‐latitudes; and 2) improve the calibration of the effective temperature coefficient for different opacity conditions. Furthermore, we highlight the importance of assessing the impact of temperature on muon rate variations when considering geophysical applications. Depending on latitude and opacity conditions, this effect may be large enough to hide subsurface density variations due to changes in groundwater content, and should therefore be removed from the time‐series.
Earth and Space Science; doi:10.1029/2019ea000727
Abstract:This study describes the simulation characteristics of a newly developed Global/Regional Integrated Model system–Chemistry Climate Model (GRIMs–CCM), which is listed in Chemistry Climate Model Initiative (CCMI) as a participating model. The GRIMs–CCM was run using a standard set of forcings, and historical sea surface temperatures (SST) and sea ice concentration from the Hadley Centre were prescribed. The simulation results of GRIMs–CCM were compared to the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis dataset 1. The GRIMs–CCM satisfactorily simulated the climatological (1960‐2010) atmospheric features as well as atmospheric teleconnections resulting from tropical SST forcing. However, the GRIMs–CCM also had some regional biases; for instance, particularly, the temperature bias over the Antarctic was noticeable. We further analyzed physical processes that caused such biases and the influence of coupled chemistry‐climate processes in the GRIMs–CCM, which may provide further guidance to improve an earlier version of the GRIMs–CCM as well as other climate‐chemistry models participating in the CCMI.
Earth and Space Science; doi:10.1029/2019ea000671
Abstract:We apply singular spectral analysis to series of monthly mean values of surface air temperatures T, sunspots ISSN and polar faculae PF (1850‐2017 for T and ISSN). The efficiency of the SSA algorithm that we use has been regularly improved. For the T, ISSN and PF series, the SSA eigenvalues and first components are shown with their Fourier spectrum. Components of T, ISSN or PF share similar periods. Most are found in solar activity. The ~22 and ~11‐yr components are modulated and drift in phase, reflecting slight differences in spectra. On the shorter period side, components at ~9, ~5.5 and ~4.7 years are in good agreement. They have been identified in solar activity. The 60 year component is prominent in T. It is not immediately apparent in ISSN but can be extracted with an appropriate choice of SSA window. Other types of data allow one to explore longer periods and confirm climatic variations at ~60, ~35 and ~22 years and at 50‐150 and 200‐500 years. When we consider a longer ISSN series starting in 1700 and recalculate the SSA first component, the trends of solar activity and temperature over the time span from 1850 to 2017 are very similar, with slower rise before 1900 and after the late 1900s, separating a faster rise in much of the 20th century. These trends, extracted over only 150 years, could be parts of longer, multi‐centennial changes in solar activity. Much of the variability of surface temperatures could be linked to the Sun.
Earth and Space Science; doi:10.1029/2019ea000674
Abstract:The Rossby wave source (RWS) in the upper troposphere plays an important role in the tropical ‐ extratropical teleconnections. Using the daily outputs from the phase 5 of the Coupled Model Inter‐comparison Project (CMIP5) models, the overall model performances in simulating the climatological Rossby wave sources in both winter and summer are evaluated. The ensemble mean of the CMIP5 models can simulate the large‐scale geographical distributions of the RWS reasonably close to the observations, with the simulations of RWS in general better in the Southern Hemisphere. For the Northern Hemisphere, most models overestimate the subtropical RWS but underestimate the midlatitude RWS in both winter and summer. Many models even fail to simulate the seasonal source‐sink shift of RWS in East Asia. Greatest intermodel differences are shown in East Asia, western North America in both seasons and in the subtropical belt in winter hemisphere. Possible reasons for the model biases in RWS are further investigated. In the NH, our analysis shows that model performance in simulating the local divergence, which might relate to the overly smoothed topography in Asia and western North America in the model, is most responsible for the biases of the RWS simulations. In the SH, the bias in subtropical divergence pattern and tropical convection all contribute to the intermodel divergence of RWS simulation.
Earth and Space Science; doi:10.1029/2019ea000596
Abstract:The Lambert Glacier‐Amery Ice Shelf System (LG‐AIS) is the largest glacial system in East Antarctica. Accurate estimation of its mass balance is imperative for reducing the uncertainty in evaluating the sea level contribution from the East Antarctic Ice Sheet. Here, we present a comprehensive investigation of the mass balance of the AIS basin. We measured the ice velocity with Sentinel‐1 Synthetic Aperture Radar (SAR) data acquired in 2016. The ice thickness data from the radio echo sounding measurements were combined with the surface mass balance data from the new Regional Atmospheric Climate Model, from which the mass balance of the AIS basin was estimated. Our estimates suggest a slight positive mass balance of 3.1 ± 9.4 Gt year‐1 in 2016. We found that the short‐term fluctuations in the surface mass balance dramatically affect the AIS mass balance. A comparison with previous estimates confirms the long‐term positive mass balance trend.
Earth and Space Science; doi:10.1029/2019ea000646
Abstract:Linear array cameras are widely used in the fields of aerial and space remote sensing. The ground‐to‐image transformation plays a significant role in the geometric processing procedures of linear pushbroom images, which is time‐consuming due to multiple iterative calculations. Moreover, the detectors of the linear array may exhibit a curved shape due to distortions, resulting in a more complex ground‐to‐image transformation. This paper presents a novel ground‐to‐image transformation algorithm for linear pushbroom images based on a rigorous sensor model. We regard the distance between the back‐projected image point and the curved shape linear array as the “generalized distance”. The idea of generalized distance prediction (GDP) was developed to efficiently determine the best scan line corresponding to the ground point. The plane analytic geometry is employed to solve the practical problems of the ground‐to‐image transformation, including the iterative direction, convergence condition and sub‐pixel interpolation. The applications of the proposed method in orthorectification and image matching were investigated. The proposed method was comprehensively tested using airborne images, Earth observation satellite images and planetary images. The experimental results demonstrate that the proposed method: (1) delivers high accuracy (better than 1 × 10−4 pixels) and efficiency; (2) is better than the cutting‐edge method based on the geometric constraints of central perspective plane for the linear pushbroom images with distortions; and (3) provides promising applications for generating orthophotos and image matching. The proposed method is easy to implement and efficient, which can greatly enhance the geometric processing abilities for various types of linear pushbroom images.
Earth and Space Science; doi:10.1029/2019ea000653
Abstract:Using high‐frequency tide gauge observations from 1980‐2017, we analyzed changes in extreme sea levels (ESLs) along the Chinese coast to examine whether extreme sea‐level rise acceleration could be observed. The results indicated that the extreme sea level has risen with fluctuations along the Chinese coast. The extreme sea level also featured significant decadal variabilities. The extreme sea level rise was accelerated at most tide gauges throughout the whole study period, especially after the 1980s, while the acceleration patterns varied with station location. The mean sea level change was confirmed as the major driver of the extreme sea level change according to the analysis. However, the skew surge may also have affected the extremes at many of the tide gauges, which was observed after detrending. The extreme/mean sea level had a significant positive correlation with the Atlantic Multidecadal Oscillation (AMO), which is supposed to affect the mean sea level through a combination of variation in SST, pressure system and wind. That sea level oscillation is dominated by AMO should be taken into consideration when studying accelerations in the rate of extreme sea levels and of mean sea levels along the Chinese coast.
Earth and Space Science; doi:10.1029/2019ea000566