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Bias characterization of ATMS low-level channels under clear-sky and cloudy conditions
Qi LI, Xiaolei ZOU
Front. Earth Sci.    https://doi.org/10.1007/s11707-019-0750-3
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The Advanced Technology Microwave Sounder (ATMS) onboard the Suomi National Polar-Orbiting Partnership satellite is a cross-track scanning instrument containing 22 sounding channels in total. In this study, the bias characteristics of channels 1–6, which could have significant cloud contamination in heavy precipitation, are first analyzed based on the differences between ATMS observations (O) and model simulations (B) under clear-sky conditions over oceans. Latitudinal dependencies of the biases of window channels 1–3 are greater than those of channels 4–6. Biases of all nadir-only observations examined in different latitudinal bands [μ1(φ)] are positive and no more than 7.0 K. Biases at higher latitudes are larger. Channels 1–5 have a generally symmetric scan bias pattern [μ2(α)]. The global distributions of brightness temperature differences after subtracting the biases, i.e., O-B-m1(φ)-μ2(α), for channels 3–6 spatially match the liquid water path distributions. Excluding ice-affected observations, channel 3–6 O-B differences systematically increase as the liquid water path increases under cloudy conditions. Further investigation is needed to apply these findings for ATMS data assimilation under both clear-sky and cloudy conditions.

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Effects of sea level rise on storm surge and waves within the Yangtze River Estuary
Yongming SHEN, Gefei DENG, Zhihao XU, Jun TANG
Front. Earth Sci.    https://doi.org/10.1007/s11707-018-0746-4
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Sea level rise (SLR) can cause water depth increase (WDI) and coastal inundation (CI). By applying the coupled FVCOM+SWAN model, this study investigates the potential impacts of WDI and CI, induced by a 1.0 m SLR, on storm surge and waves within the Yangtze River Estuary. A 1.0 m WDI decreases the maximum storm surge by 0.15 m and increases the maximum significant wave height by 0.35 m. The CI effect size is smaller when compared with WDI. CI decreases the maximum storm surge and significant wave height by 0.04 and 0.07 m, respectively. In the near-shore area, WDI significantly alters the local hydrodynamic environment, thereby stimulating changes in maximum storm surges and wave heights. Low-lying regions are negatively impacted by CI. Conversely, in deep-water areas, the relative change in water depth is minimal and the effect of CI is gradually enhanced. The combined effect of WDI and CI decreases the maximum surge by 0.31 m and increases the maximum significant wave height by 0.21 m. As a result, CI may be neglected when designing deep-water infrastructures. Nonetheless, the complex interactions between adoption and neglect of CI should be simulated to achieve the best seawall flood control standards and design parameters.

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The barrier river reach identification and classification in the Middle Yangtze River
Jinwu TANG, Chunyan HU, Xingying YOU, Yunping YANG, Xiaofeng ZHANG, Jinyun DENG, Meng CHEN
Front. Earth Sci.    https://doi.org/10.1007/s11707-018-0689-9
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Adjustments of upstream river regimes are one of the main factors affecting downstream fluvial processes. However, not all adjustments of river regimes will propagate downstream. There are some distinctive river reaches where upstream and downstream adjustments have no relevance. However, the irrelevance is neither caused by different river types nor by the different conditions of water and sediment; but rather, the channel boundaries and riverbed morphologies block the propagation effect. These are referred to here as the barrier river reach phenomena. The migration of the thalweg line is the essential reason for causing the propagation effect. Numerous influencing factors for thalweg migration exist, including 1) the average flow rate above the critical bankfull discharge, the average flow rate below the critical bankfull discharge, and their ratio, 2) the ratio of the duration of the aforementioned two periods, 3) the thalweg displacement at the entrance of the river reach, 4) the deflecting flow intensity of the node, 5) the ratio of the river width to water depth, 6) the relative width of the floodplain, and 7) the Shields number. In this study, the correlativity between the measured distances and the restricting indicators of thalweg migration in the Middle Yangtze River over the years was established. The barrier degree of 27 single-thread river reaches was subsequently assessed. These reaches included 4 barrier river reaches; 5 transitional reaches transforming from barrier to non-barrier; 10 transitional reaches transforming from non-barrier to barrier; and 8 non-barrier river reaches. Barrier river reaches were found to be important for maintaining the stability of the river regime and the transverse equilibrium of sediment transport in the downstream reaches. To some extent, the barrier river reaches may protect the natural dynamical properties from being destroyed by artificial river regulation works. Thus, they are of great significance for river management.

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Spatiotemporal influences of land use/cover changes on the heat island effect in rapid urbanization area
Ying XIONG, Fen PENG, Bin ZOU
Front. Earth Sci.    https://doi.org/10.1007/s11707-018-0747-3
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Rapid urban sprawl and growth led to substantial urban thermal environment changes and influenced the local climate, environment, and quality of life of residents. Taking the Chang-Zhu-Tan urban agglomeration in China as a case, this study firstly identified the spatiotemporal patterns of surface urban heat island intensity (SUHII) and the land use/cover changes (LUCC) based on multi-temporal Landsat TM satellite data over 21 years, and then investigated the relationship between LUCC and SUHII by methods of logistic regression model and centroid shift analysis. The results showed that green spaces (e.g., cropland, forestland) of 899.13 km2 had been converted to built-up land during the 1994–2015 period, which caused significant urban expansion. The SUHII was the highest for built-up land, high for unused land, low for cropland and grassland, and the lowest for forestland and open water. Many areas experienced extensive rapid urbanization because of the emergence of the urban agglomeration, which resulted in the loss of green spaces and increased SUHI effects over the 21-year study period. In addition, the results of centroid shift analysis found that the growth of SUHII and the expansion of high SUHII areas are closely related to the expansion of an existing urban area in Xiangtan, while the increases of building density and height in Changsha resulted in the decrease of SUHII and spatiotemporal change of high SUHII areas. The analysis of the effects of land use/cover types on the SUHII in this study will contribute to future urban land use allocation for the mitigation of SUHI formation.

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Vegetation and soil wind erosion dynamics of sandstorm control programs in the agro-pastoral transitional zone of northern China
Zhitao WU, Mingyue WANG, Hong ZHANG, Ziqiang DU
Front. Earth Sci.    https://doi.org/10.1007/s11707-018-0715-y
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To combat soil erosion and desertification, large-scale sandstorm control programs have been put in place since 2000 in the agro-pastoral transitional zone of northern China. Vegetation dynamics as well as soil wind erosion control effects are very important for assessing the ecological success of sandstorm control programs in China. However, no comprehensive evaluation of vegetation dynamics and soil wind erosion control effects in this region has been achieved. In this study, we illustrate the vegetation and soil wind erosion dynamics of sandstorm control programs in the northern Shanxi Province using remote sensing data and soil wind erosion models. There was a significant increase in vegetation cover for 63.59% of the study area from 2001 to 2014 and a significant decrease for 2.00% of the study area. The normalized difference vegetation index (NDVI) showed that the largest increase occurred in autumn. Soil wind erosion mass decreased from 20.90 million tons in 2001 to 7.65 million tons in 2014. Compared with 2001, the soil wind erosion moduli were reduced by 43.05%, 36.16%, and 62.66% in 2005, 2010, and 2014, respectively. Spatially, soil wind erosion in most of the study area was alleviated between 2001 and 2014. The relationship between NDVI and soil wind erosion mass showed that the increased vegetation coverage reduced the soil wind erosion mass. In addition, wind was the main driving force behind the soil wind erosion dynamics. The results indicate that the vegetation coverage has increased and soil wind erosion mass has been reduced following the implementation of the sandstorm control programs. However, the ecological effects of the sandstorm control programs may vary over different periods. While the programs appear to be beneficial in the short term, there may be unintended consequences in the long term. Research on the sustainability of the ecological benefits of sandstorm control programs needs to be conducted in the future.

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The 2015/16 El Niño-related glacier changes in the tropical Andes
Bijeesh Kozhikkodan VEETTIL, Jefferson Cardia SIMÕES
Front. Earth Sci.    https://doi.org/10.1007/s11707-018-0738-4
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Significant changes in the area and snowline altitude of two glacierized mountains – Nevado Champara (Cordillera Blanca, Peru) and Cerro Tilata (Cordillera Real, Bolivia) – in the tropical Andes, before and after the recent El Niño in 2015/16 period, have been analysed using Sentinel 2A and Landsat data. It is seen that the recent El Niño has been accompanied by higher fluctuation in glacier coverage on Nevado Champara and the loss of glacier coverage on Cerro Tilata was very high during the past 16 years. Rise in snowline altitude of selected glaciers was very high after the 2015/16 El Niño. Increase in the area covered by snow and ice during the La Niña periods were not enough to cover the ice loss occurred during the previous El Niño events and the strongest El Niño in 2015/16 was followed by a significant loss of ice-covered areas in the tropical Andes. Freshwater resources in this region will be affected in the near future if the current trends in glacier decline continue. Adaptation strategies needs to be implemented to reduce the impacts of the continuing loss of glacierized on regional communities in the tropical Andean region.

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Detection of short-term urban land use changes by combining SAR time series images and spectral angle mapping
Zhuokun PAN, Yueming HU, Guangxing WANG
Front. Earth Sci.    https://doi.org/10.1007/s11707-018-0744-6
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Rapid urban sprawl and re-construction of old towns have been leading to great changes of land use in cities of China. To witness short-term urban land use changes, rapid or real time remote sensing images and effective detection methods are required. With the availability of short repeat cycle, relatively high spatial resolution, and weather-independent Synthetic Aperture Radar (SAR) remotely sensed data, detection of short-term urban land use changes becomes possible. This paper adopts newly released Sentinel-1 SAR data for urban change detection in Tianhe District of Guangzhou City in Southern China, where dramatic urban redevelopment practices have been taking place in past years. An integrative method that combines the SAR time series data and a spectral angle mapping (SAM) was developed and applied to detect the short-term land use changes. Linear trend transformations of the SAR time series data were first conducted to reveal patterns of substantial changes. Spectral mixture analysis was then conducted to extract temporal endmembers to reflect the land development patterns based on the SAR backscattering intensities over time. Moreover, SAM was applied to extract the information of significant increase and decrease patterns. The results of validation and method comparison showed a significant capability of both the proposed method and the SAR time series images for detecting the short-term urban land use changes. The method received an overall accuracy of 78%, being more accurate than that using a bi-temporal image change detection method. The results revealed land use conversions due to the removal of old buildings and their replacement by new construction. This implies that SAR time series data reflects the spatiotemporal evolution of urban constructed areas within a short time period and this study provided the potential for detecting changes that requires continuously short-term capability, and could be potential in other landscapes.

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Analysis of ship wake features and extraction of ship motion parameters from SAR images in the Yellow Sea
Kaiguo FAN, Huaguo ZHANG, Jianjun LIANG, Peng CHEN, Bojian XU, Ming ZHANG
Front. Earth Sci.    https://doi.org/10.1007/s11707-018-0743-7
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The identifying features of ship wakes in synthetic aperture radar (SAR) remote sensing images are of great importance for detecting ships and for extracting ship motion parameters. A statistical analysis was conducted on the identifying features of ship wakes in SAR images in the Yellow Sea. In this study, 1091 ship wake sub-images were selected from 327 SAR images in the Yellow Sea near Qingdao. Analysis of the identifying features of ship wakes in SAR images revealed that both turbulent wakes and Kelvin wakes account for the majority of ship wakes, with turbulent wakes occurring approximately four times as frequently as Kelvin wakes. Narrow-V wakes and internal wave wakes were comparatively rare, which is due to the peculiarities of the radar system parameters and marine environments required to observe these wakes. Additionally, we extracted ship motion parameters from four types of ship wakes in the SAR images. Specifically, internal wave wakes in SAR images in the Yellow Sea were also used to extract ship motion parameters. Validation of the extracted parameters indicated that the extraction of these parameters from ship wakes is a viable and accurate approach for the acquisition of ship motion parameters. These results provide a solid foundation for the commercialization of SAR-based technologies for detecting ships and extracting ship motion parameters.

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Chemical and minero-petrographical changes on granulite rocks affected by weathering processes
Carmine APOLLARO, Francesco PERRI, Emilia LE PERA, Ilaria FUOCO, Teresa CRITELLI
Front. Earth Sci.    https://doi.org/10.1007/s11707-018-0745-5
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The purpose of this work is to study the weathering processes of the granulite rocks of the Serre Massif (southern Calabria, Italy) using a multidisciplinary approach based on field studies, geochemical modeling, and minero-petrographical analyses. The granulite rocks are plagioclase-rich with minor amphibole, clinopyroxene, orthopyroxene, biotite, and garnet and their texture are coarse-grained. The reaction path modeling was performed to simulate the evolution of groundwaters upon interaction with local granulite by means of the software package EQ3/6, version 8.0a. Simulations were performed in kinetic (time) mode under a closed system at a constant temperature of 11.5°C, (which reproduces the average temperature of local area) and fixing the fugacity of CO2 at 10−2.34 bar (mean value). During the most advanced stage of weathering the main mineralogical changes are: partial destruction and transformation of biotite and plagioclase associated with neoformation of ferruginous products and secondary clay minerals producing a change in the origin rock fabric. The secondary solid phases observed during the geochemical modeling (kaolinite, vermiculite and ferrihydrite) are similar to those found in this natural system. Thus, the soil-like material mainly characterized by mostly sand to gravel grain-size fractions is the final result of the weathering processes.

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Comparison of C- and L-band simulated compact polarized SAR in oil spill detection
Xiaochen WANG, Yun SHAO, Fengli ZHANG, Wei TIAN
Front. Earth Sci.    https://doi.org/10.1007/s11707-018-0733-9
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This paper presents the compact polarized (CP) pseudo quad-pol parameters for the detection of marine oil spills and segregation of lookalikes using simulated CP SAR data from full-polarized (FP) SAR imagery. According to the CP theory, 11 polarized parameters generally used for the detection of oil spills were derived from reconstructed pseudo quad-pol data for both C and L bands. In addition, the reconstruction performance between C and L bands was also compared by evaluating the reconstruction accuracy of retrieved polarized parameters. The results show that apart from σHV and RH, other polarized parameters of σHH, σVV, H, α, φH-V, r, ρH-V, and γ can be reconstructed with satisfactory accuracy for both C and L bands. Furthermore, C band has a higher reconstruction accuracy than L band, especially for φH-V. Moreover, the effect of reconstruction of polarized parameters on oil spill classification was also evaluated using the maximum likelihood classification (MLC) method. According to the evaluation of kappa coefficients and mapping accuracy, it is recommended to use σ HH, σVV, H, ρH-V, and γ of the C band CP SAR for marine oil spill classification.

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