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  1. Article ; Online: A New HASM-Based Downscaling Method for High-Resolution Precipitation Estimates

    Na Zhao / Yimeng Jiao

    Remote Sensing, Vol 13, Iss 2693, p

    2021  Volume 2693

    Abstract: Obtaining high-quality precipitation datasets with a fine spatial resolution is of great importance for a variety of hydrological, meteorological and environmental applications. Satellite-based remote sensing can measure precipitation in large areas but ... ...

    Abstract Obtaining high-quality precipitation datasets with a fine spatial resolution is of great importance for a variety of hydrological, meteorological and environmental applications. Satellite-based remote sensing can measure precipitation in large areas but suffers from inherent bias and relatively coarse resolutions. Based on the high accuracy surface modeling method (HASM), this study proposed a new downscaling method, the high accuracy surface modeling-based downscaling method (HASMD), to derive high-quality monthly precipitation estimates at a spatial resolution of 0.01° by downscaling the Integrated Multi-satellitE Retrievals for Global Precipitation Measurement (IMERG) precipitation estimates in China. A scale transformation equation was introduced in HASMD, and the initial value was set by including the explanatory variables related to precipitation. The performance of HASMD was evaluated by comparing the results yielded by HASM and the combined method of HASM, Kriging, IDW and the geographical weighted regression (GWR) method (GWR-HASM, GWR-Kriging, GWR-IDW). Analysis results indicated that HASMD performed better than the other four methods. High agreement was achieved for HASMD, with bias values ranging from 0.07 to 0.29, root mean square error (RMSE) values ranging from 9.53 mm to 47.03 mm, and R 2 values ranging from 0.75 to 0.96. Compared with the original IMERG precipitation products, the downscaling accuracy with HASMD improved up to 47%, 47%, and 14% according to bias, RMSE and R 2 , respectively. HASMD was able to capture the spatial variation in monthly precipitation in a vast region, and it might be potentially applicable for enhancing the spatial resolution and accuracy of remotely sensed precipitation data and facilitating their application at large scales.
    Keywords satellite precipitation estimates ; downscaling ; IMERG ; Science ; Q
    Subject code 333
    Language English
    Publishing date 2021-07-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: Projections of precipitation change from CMIP6 based on a new downscaling method in the Poyang Lake basin, China

    Na Zhao / Yimeng Jiao / Lili Zhang

    Journal of Hydrology: Regional Studies, Vol 42, Iss , Pp 101138- (2022)

    2022  

    Abstract: Study region: The Poyang Lake (PL) basin, located in the middle and lower reaches of the Yangtze River, China. Study focus: This study investigated the future precipitation variations during 2020–2100 under four shared socioeconomic pathways (SSPs) by ... ...

    Abstract Study region: The Poyang Lake (PL) basin, located in the middle and lower reaches of the Yangtze River, China. Study focus: This study investigated the future precipitation variations during 2020–2100 under four shared socioeconomic pathways (SSPs) by downscaling the CMIP6 outputs using a new scale-based downscaling method, which integrated the GWR-KED method and time transfer matrices by linking the precipitation in the historical and future periods. New hydrological insights: Compared with the original CMIP6 outputs, the downscaled precipitation predictions exhibited large improvements, with mean absolute errors (MAEs) improved by a range of 37.49~66.81% and 74.95~75.38% on the seasonal and annual scale, respectively. The downscaled projections showed that the basin would be wetter at the annual scale during the next 80 years. Precipitation in spring would be increase over the entire basin under all future scenarios except SSP1–2.6. Parts of the PL basin exhibit drier trends under the four scenarios in summer, with the largest drying area occurring in the SSP2–4.5 scenario. Except in the SSP2–4.5 scenario, precipitation in autumn has increasing trends in all scenarios across the PL basin. Precipitation in winter shows a drying trend in some areas except in the SSP1–2.6 scenario, with the largest area occurring in SSP5–8.5. The results provide improved precipitation information for policy-making in water resource management and adaptation planning to mitigate Yangtze River floods in the future.
    Keywords Precipitation change ; CMIP6 scenarios ; Downscaling ; Poyang Lake basin ; Physical geography ; GB3-5030 ; Geology ; QE1-996.5
    Subject code 910 ; 550
    Language English
    Publishing date 2022-08-01T00:00:00Z
    Publisher Elsevier
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Article ; Online: Global future population exposure to heatwaves

    Yuwei Wang / Na Zhao / Xiaozhe Yin / Chaoyang Wu / Mingxing Chen / Yimeng Jiao / Tianxiang Yue

    Environment International, Vol 178, Iss , Pp 108049- (2023)

    2023  

    Abstract: The increasing exposure to extreme heatwaves in urban areas from both climate change and the urban heat island (UHI) effect poses multiple threats and challenges to human society. Despite a growing number of studies focusing on extreme exposure, research ...

    Abstract The increasing exposure to extreme heatwaves in urban areas from both climate change and the urban heat island (UHI) effect poses multiple threats and challenges to human society. Despite a growing number of studies focusing on extreme exposure, research advances are still limited in some aspects such as oversimplification of human exposure to heatwaves and neglect of perceived temperature as well as actual body comfort, resulting in unreliable and unrealistic estimates of future results. In addition, little research has performed comprehensive and fine-resolution global analyses in future scenarios. In this study, we present the first global fine-resolution projection of future changing urban population exposure to heatwaves by 2100 under four shared socioeconomic pathways (SSPs) considering urban expansion at global, regional, and national scales. Overall, global urban population exposure to heatwaves is rising under the four SSPs. Temperate and tropical zones predictably have the greatest exposure among all climate zones. Coastal cities are projected to have the greatest exposure, followed closely by cities at low altitudes. Middle-income countries have the lowest exposure and the lowest inequality of exposure among countries. Individual climate effects contributed the most (approximately 46.4%) to future changes in exposure, followed by the interactive effect between climate and urbanization (approximately 18.5%). Our results indicate that more attention needs to be paid to policy improvements and sustainable development planning of global coastal cities and some low-altitude cities, especially in low- and high-income countries. Meanwhile, this study also highlights the impact of continued future urban expansion on population exposure to heatwaves.
    Keywords Climate change ; Heatwaves ; Population exposure ; Urbanization ; Environmental sciences ; GE1-350
    Subject code 333
    Language English
    Publishing date 2023-08-01T00:00:00Z
    Publisher Elsevier
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article ; Online: The Geological History of the Chang’e-5 Sample Return Region

    Jiayin Deng / Weiming Cheng / Yimeng Jiao / Jianzhong Liu / Jianping Chen / Baixue Wang

    Remote Sensing, Vol 13, Iss 4679, p

    2021  Volume 4679

    Abstract: Chang’e-5 (CE-5), China’s first sample-return mission, has successfully landed in Oceanus Procellarum near Mons Rümker. It is important to have a detailed study of the geological evolution of the CE-5 sample return region. This work aims to study the ... ...

    Abstract Chang’e-5 (CE-5), China’s first sample-return mission, has successfully landed in Oceanus Procellarum near Mons Rümker. It is important to have a detailed study of the geological evolution of the CE-5 sample return region. This work aims to study the geological background, topography, geomorphology, major chemical composition, mineralogy, and chronology of the landing site region. First, we used the map of topography obtained by the Kaguya TC merged Digital Terrain Model (DTM) to analyze the topographic characteristics. Then, we used the Kaguya Multiband Imager (MI) reflectance data to derive FeO and TiO 2 abundance and the hyperspectral data of the Moon Mineralogy Mapper (M 3 ) onboard the Chandrayaan-1 spacecraft to study the mineralogy of the landing site region. Later, we defined and dated the geological units of the landing area using the crater size–frequency distribution (CSFD) method. Finally, we conducted a detailed analysis of the volcanism and tectonism that occurred in the CE-5 landing area. The study region has experienced multi-stage magmatic activities (~3.36 Ga to ~1.22 Ga) and formed multiple mare units with different chemical and mineral compositions. The relationship between the wrinkle ridges cut by small impact craters suggests that the U7/Em5 has experienced Copernican aged tectonism recently ~320 Ma. The U7/Em5 unit where the Chang’e-5 sample return mission landed is dominantly composed of mature pyroxene and the basalts are mainly high-iron and mid-titanium basalts. Additionally, the analysis of pure basalt in the U7/Em5 suggests that the samples returned by the CE-5 mission may contain the ejecta and ray materials of young craters, including sharp B, Harding, Copernicus, and Aristarchus.
    Keywords Moon ; CE-5 ; geological features ; volcanism ; tectonism ; Science ; Q
    Subject code 910
    Language English
    Publishing date 2021-11-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Article ; Online: Mapping bamboo forest and expansion intensity in China by coupling vegetation phenology and C-band SAR with Sentinel-1 and Sentinel-2 images

    Saibo Li / Shaoyang He / Tianxiang Yue / Zhengping Du / Na Zhao / Yapeng Zhao / Yimeng Jiao / Bin Fan / Yi Liu / Zhe Xu / Yang Yang

    International Journal of Applied Earth Observations and Geoinformation, Vol 121, Iss , Pp 103384- (2023)

    2023  

    Abstract: Bamboo forest has undergone dramatic expansion due to climate changes and human activities, and its direct effects on both carbon storage and biodiversity of the forest ecosystem have occurred in tropical and subtropical regions, especially in China. ... ...

    Abstract Bamboo forest has undergone dramatic expansion due to climate changes and human activities, and its direct effects on both carbon storage and biodiversity of the forest ecosystem have occurred in tropical and subtropical regions, especially in China. However, the uncertainty in tracking bamboo forest extent and expansion intensity substantially influenced our assessment of them due to the poor resolution and persistent cloud covers in optical images (e.g., Landsat and Sentinel-2). We developed a straightforward and superior algorithm by coupling vegetation phenology and cloud-free SAR using Sentinel-1 and -2 images to identify bamboo forest at large scales and higher spatial resolution. Specifically, (1) this study analyzed the spectral and phenological characteristics during the bamboo forest growth season; (2) the optimum parameter sets for the SAR backscatter were calibrated against field data by using the genetic algorithm; (3) and then we generated bamboo forest and expansion intensity maps at 10 m spatial resolution for seven study regions in China in 2020. The results showed that the Kappa of the maps was 0.89, and the OA was 94.7% in all study areas, compared with the field data. The accuracy among each study area also performed well in mapping bamboo forest, indicated by Kappa varying from 0.82 to 0.94, and OA ranging from 91.1% to 97.33%. Compared to the national forestry inventory map, our results showed a significant positive linear relationship, with a higher R2 (0.96, p < 0.001). With the high-resolution results, we found that the tree was most severely affected by bamboo forest, followed by grassland, sparse vegetation, and shrubland. This product can be a key input for many carbon cycles, climate, and vegetation models.
    Keywords Bamboo forest ; Expansion intensity ; Vegetation phenology ; SAR ; Google Earth Engine ; Physical geography ; GB3-5030 ; Environmental sciences ; GE1-350
    Subject code 910
    Language English
    Publishing date 2023-07-01T00:00:00Z
    Publisher Elsevier
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  6. Article ; Online: Retrieval and Validation of XCO 2 from TanSat Target Mode Observations in Beijing

    Zhengyi Bao / Xingying Zhang / Tianxiang Yue / Lili Zhang / Zong Wang / Yimeng Jiao / Wenguang Bai / Xiaoyang Meng

    Remote Sensing, Vol 12, Iss 3063, p

    2020  Volume 3063

    Abstract: Satellite observation is one of the main methods used to monitor the global distribution and variation of atmospheric carbon dioxide (CO 2 ). Several CO 2 monitoring satellites have been successfully launched, including Japan’s Greenhouse Gases Observing ...

    Abstract Satellite observation is one of the main methods used to monitor the global distribution and variation of atmospheric carbon dioxide (CO 2 ). Several CO 2 monitoring satellites have been successfully launched, including Japan’s Greenhouse Gases Observing SATellite (GOSAT), the USA’s Orbiting Carbon Observatory-2 (OCO-2), and China’s Carbon Dioxide Observation Satellite Mission (TanSat). Satellite observation targeting the ground-based Fourier transform spectrometer (FTS) station is the most effective technique for validating satellite CO 2 measurement precision. In this study, the coincident observations from TanSat and ground-based FTS were performed numerous times in Beijing under a clear sky. The column-averaged dry-air mole fraction of carbon dioxide (XCO 2 ) obtained from TanSat was retrieved by the Department for Eco-Environmental Informatics (DEEI) of China’s State Key Laboratory of Resources and Environmental Information System based on a full physical model. The comparison and validation of the TanSat target mode observations revealed that the average of the XCO 2 bias between TanSat retrievals and ground-based FTS measurements was 2.62 ppm, with a standard deviation (SD) of the mean difference of 1.41 ppm, which met the accuracy standard of 1% required by the mission tasks. With bias correction, the mean absolute error (MAE) improved to 1.11 ppm and the SD of the mean difference fell to 1.35 ppm. We compared simultaneous observations from GOSAT and OCO-2 Level 2 (L2) bias-corrected products within a ±1° latitude and longitude box centered at the ground-based FTS station in Beijing. The results indicated that measurements from GOSAT and OCO-2 were 1.8 ppm and 1.76 ppm higher than the FTS measurements on 20 June 2018, on which the daily observation bias of the TanSat XOC 2 results was 1.87 ppm. These validation efforts have proven that TanSat can measure XCO 2 effectively. In addition, the DEEI-retrieved XCO 2 results agreed well with measurements from GOSAT, OCO-2, and the Beijing ground-based FTS.
    Keywords TanSat ; target mode ; XCO2 retrieval ; validation ; Beijing FTS ; Science ; Q
    Subject code 290
    Language English
    Publishing date 2020-09-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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