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| 1 | The impacts of climate extremes on the terrestrial carbon cycle:A review显示文摘The increased frequency of climate extremes in recent years has profoundly affected terrestrial ecosystem functions and the welfare of human society. The carbon cycle is a key process of terrestrial ecosystem changes. Therefore, a better understanding and assessment of the impacts of climate extremes on the terrestrial carbon cycle could provide an important scientific basis to facilitate the mitigation and adaption of our society to climate change. In this paper, we systematically review the impacts of climate extremes(e.g. drought, extreme precipitation, extreme hot and extreme cold) on terrestrial ecosystems and their mechanisms. Existing studies have suggested that drought is one of the most important stressors on the terrestrial carbon sink, and that it can inhibit both ecosystem productivity and respiration. Because ecosystem productivity is usually more sensitive to drought than respiration, drought can significantly reduce the strength of terrestrial ecosystem carbon sinks and even turn them into carbon sources. Large inter-model variations have been found in the simulations of drought-induced changes in the carbon cycle, suggesting the existence of a large gap in current understanding of the mechanisms behind the responses of ecosystem carbon balance to drought, especially for tropical vegetation. The effects of extreme precipitation on the carbon cycle vary across different regions. In general, extreme precipitation enhances carbon accumulation in arid ecosystems, but restrains carbon sequestration in moist ecosystems. However, current knowledge on the indirect effects of extreme precipitation on the carbon cycle through regulating processes such as soil carbon lateral transportation and nutrient loss is still limited. This knowledge gap has caused large uncertainties in assessing the total carbon cycle impact of extreme precipitation. Extreme hot and extreme cold can affect the terrestrial carbon cycle through various ecosystem processes. Note that the severity of such climate extremes depends greatly on their timing, which needs to be investigated thoroughly in future studies. In light of current knowledge and gaps in the understanding of how extreme climates affect the terrestrial carbon cycle, we strongly recommend that future studies should place more attention on the long-term impacts and on the driving mechanisms at different time scales.Studies based on multi-source data, methods and across multiple spatial-temporal scales, are also necessary to better characterize the response of terrestrial ecosystems to climate extremes. | Shilong PIAO Xinping ZHANG Anping CHEN Qiang LIU Xu LIAN Xuhui WANG Shushi PENG Xiuchen WU | 2019 | Science China Earth Sciences2019，62，10： | 16 |
| 2 | On the Key Dynamical Processes Supporting the 21.7 Zhengzhou Record-breaking Hourly Rainfall in China显示文摘An extremely heavy rainfall event occurred in Zhengzhou,China,on 20 July 2021 and produced an hourly rainfall rate of 201.9 mm,which broke the station record for China's Mainland.Based on radar observations and a convection-permitting simulation using the WRF-ARW model,this paper investigates the multiscale processes,especially those at the mesoscale,that support the extreme observed hourly rainfall.Results show that the extreme rainfall occurred in an environment characteristic of warm-sector heavy rainfall,with abundant warm moist air transported from the ocean by an abnormally northward-displaced western Pacific subtropical high and Typhoon In-Fa(2021).However,rather than through back building and echo training of convective cells often found in warm-sector heavy rainfall events,this extreme hourly rainfall event was caused by a single,quasi-stationary storm in Zhengzhou.Scale separation analysis reveals that the extreme-rainproducing storm was supported and maintained by the dynamic lifting of low-level converging flows from the north,south,and east of the storm.The low-level northerly flow originated from a mesoscale barrier jet on the eastern slope of the Taihang Mountain due to terrain blocking of large-scale easterly flows,which reached an overall balance with the southerly winds in association with a low-level meso-β-scale vortex located to the west of Zhengzhou.The large-scale easterly inflows that fed the deep convection via transport of thermodynamically unstable air into the storm prevented the eastward propagation of the weak,shallow cold pool.As a result,the convective storm was nearly stationary over Zhengzhou,resulting in record-breaking hourly precipitation. | Peng WEI Xin XU Ming XUE Chenyue ZHANG Yuan WANG Kun ZHAO Ang ZHOU Shushi ZHANG Kefeng ZHU | 2023 | Advances in Atmospheric Sciences2023，40，3： | 9 |
| 3 | Linear FM Signal Parameter Estimation Using STFT and FRFT显示文摘 | SHEN Liran YIN Qingbo LU Mingyu ZHANG Qi GUO Lili SHEN Tianen ZHAO Guoku NING Shushi | 2013 | Chinese Journal of Electronics2013，22，2： | 8 |
| 4 | Variability of microphysical characteristics in the “21·7” Henan extremely heavy rainfall event显示文摘In this study, significant rainfall microphysical variability is revealed for the extremely heavy rainfall event over Henan Province in July 2021(the “21·7” Henan EHR event) using a dense network of disdrometers and two polarimetric radars.The broad distributions of specific drop size distribution(DSD) parameters are identified in heavy rainfall from the disdrometer observations, indicating obvious microphysical variability on the surface. A K-means clustering algorithm is adopted to objectively classify the disdrometer datasets into separate groups, and distinct DSD characteristics are found among these heavy rainfall groups. Combined with the supporting microphysical structures obtained through radar observations, comprehensive microphysical features of the DSD groups are derived. An extreme rainfall group is dominantly formed in the deep convection over the plain regions, where the high number of concentrations and large mean sizes of surface raindrops are underpinned by both active ice-phase processes and efficient warm-rain collision-coalescence processes in the vertical direction. Convection located near orographic regions is characterized by restricted ice-phase processes and high coalescence efficiency of liquid hydrometeors, causing the dominant DSD group to comprise negligible large raindrops. Multiple DSD groups can coexist within certain precipitation episodes at the disdrometer stations, indicating the potential microphysical variability during the passage of convective system on the plain regions. | Gang CHEN Kun ZHAO Yinghui LU Yuanyuan ZHENG Ming XUE Zhe-Min TAN Xin XU Hao HUANG Haonan CHEN Fen XU Ji YANG Shushi ZHANG Xueqi FAN | 2022 | Science China Earth Sciences2022，65，10： | 4 |
| 5 | Scalable local reconstruction code design for hot data reads in cloud storage systems显示文摘Since demand for data is significantly heterogeneous in cloud storage systems(CSSs),there is traffic congestion in nodes storing hot data.In erasure-coded CSSs,traffic congestion can be alleviated by degraded reads sacrificing the bandwidth of surviving nodes.Local reconstruction codes(LRCs)reduce the bandwidth consumption of degraded reads,but cannot provide skewed throughput gain for the hot data.In this paper,we propose a scalable local reconstruction code(SLRC)that relies on LRCs but is more flexible in improving the throughput of a specific data block.First,we develop the local maximum throughput(LMT)to measure the maximum throughput of the hot data blocks by analyzing the actual read arrival rate of LRCs.Further,we elaborate on the structure of SLRC and analyze their performance metrics,which include storage overhead,reconstruction cost,and LMT.To select the appropriate code,we present the minimum reconstruction cost,minimum storage overhead,and minimum penalty algorithms.Finally,we implement extensive experiments on several typical SLRCs on the Hadoop distributed file system.Higher LMT and lower bandwidth consumption can be provided by SLRCs for hot data block degraded reads in CSSs compared with RS codes and LRCs. | Zhikai ZHANG Shushi GU Qinyu ZHANG | 2022 | Science China(Information Sciences)2022，65，12： | 1 |
| 6 | A NOVEL APPROACH OF LIMITED-RANDOMNESS FOUNTAIN CODES IN DEEP SPACE COMMUNICATION显示文摘Digital fountain is applied into deep space communication for its rateless and non-feedback forward error correction.However,the long code length and encoding overhead are confined factors to guarantee a considerable recovery probability as power and buffer-limited equipment in deep space environment.At the same time,the typical fountain decoding is sub-optimum decoding algorithm.We propose a new approach,Dependent Sequences Compensation Algorithm(DSCA),to improve the encoding efficiency by restricting the randomness in fountain encoding.While decoding algorithm is also optimized by redundant information in stopping set.The results show that the optimized method can obtain a 10-4 decoding failure rate with overhead under 0.20 for code length 500,which indicates the usefulness of the proposed approach in deep space communication. | Gu Shushi Zhang Qinyu Jiao Jian | 2011 | Journal of Electronics(China)2011，28，2： | 1 |
| 7 | Multi-objective network optimization combining topology and routing algorithms in multi-layered satellite networks显示文摘In satellite communication studies, the multi-layered satellite network (MLSN) can take advan-tage of both wide coverage and low time delay.Furthermore, the issue of stable networking anddynamic reconstructing methods is still worth ex-ploring. However, current studies rarely involvethe combination of the routing algorithm and thenetwork topology. | Zhuoming LI Huiyun XIA Yu ZHANG Junqing QI Shaohua WU Shushi GU | 2018 | Science China(Information Sciences)2018，61，8： | 0 |
| 8 | Layered Coded Cache Placement and Cooperative Delivery with Sharing Links in Satellite-Terrestrial Integrated Networks显示文摘Cooperative utilization of multidimensional resources including cache, power and spectrum in satellite-terrestrial integrated networks(STINs) can provide a feasible approach for massive streaming media content delivery over the seamless global coverage area. However, the on-board supportable resources of a single satellite are extremely limited and lack of interaction with others. In this paper, we design a network model with two-layered cache deployment, i.e., satellite layer and ground base station layer, and two types of sharing links, i.e., terrestrial-satellite sharing(TSS) links and inter-satellite sharing(ISS) links, to enhance the capability of cooperative delivery over STINs. Thus, we use rateless codes for the content divided-packet transmission, and derive the total energy efficiency(EE) in the whole transmission procedure, which is defined as the ratio of traffic offloading and energy consumption. We formulate two optimization problems about maximizing EE in different sharing scenarios(only TSS and TSS-ISS),and propose two optimized algorithms to obtain the optimal content placement matrixes, respectively.Simulation results demonstrate that, enabling sharing links with optimized cache placement have more than 2 times improvement of EE performance than other traditional placement schemes. Particularly, TSS-ISS schemes have the higher EE performance than only TSS schemes under the conditions of enough number of satellites and smaller inter-satellite distances. | Gu Shushi Chen Zihan Wu Yaonan Zhang Qinyu Wang Ye | 2024 | China Communications2024，21，3： | 0 |
| 9 | Seasonal compensation implied no weakening of the land carbon sink in the Northern Hemisphere under the 2015/2016 El Niño显示文摘The recurrent extreme El Niño events are commonly linked to reduced vegetation growth and the land carbon sink over many but discrete regions of the Northern Hemisphere(NH).However,we reported here a pervasive and continuous vegetation greening and no weakened land carbon sink in the maturation phase of the 2015/2016 El Niño event over the NH(mainly in the extra-tropics),based on multiple evidences from remote sensing observations,global ecosystem model simulations and atmospheric CO_(2)inversions.We discovered a significant compensation effect of the enhanced vegetation growth in spring on subsequent summer/autumn vegetation growth that sustained vegetation greening and led to a slight increase in the land carbon sink over the spring and summer of 2015(average increases of 23.34%and 0.63%in net ecosystem exchange from two independent datasets relative to a 5-years average before the El Niño event,respectively)and spring of 2016(6.82%),especially in the extra-tropics of the NH,where the water supply during the pre-growing-season(November of the previous year to March of the current year)had a positive anomaly.This seasonal compensation effect was much stronger than that in 1997 and 1998 and significantly alleviated the adverse impacts of the 2015/2016 El Niño event on vegetation growth during its maturation phase.The legacy effect of water supply during the pre-growing-season on subsequent vegetation growth lasted up to approximately six months.Our findings highlight the role of seasonal compensation effects on mediating the land carbon sink in response to episodic extreme El Niño events. | Fangzhong SHI Xiuchen WU Xiaoyan LI Philippe CIAIS Hongyan LIU Chao YUE Yuting YANG Shulei ZHANG Shushi PENG Yi YIN Benjamin POULTER Deliang CHEN | 2024 | Science China Earth Sciences2024，67，1： | 0 |
| 10 | APOD mission status and preliminary results显示文摘On September 20 th, 2015, twenty satellites were successfully deployed into a near-polar circular orbit at 520 km altitude by the Chinese CZ-6 test rocket, which was launched from the Tai Yuan Satellite Launch Center. Among these satellites, a set of 4 Cube Sats conform the atmospheric density detection and precise orbit determination(APOD) mission, which is projected for atmospheric density estimation from in-situ detection and precise orbit products. The APOD satellites are manufactured by China Spacesat Co. Ltd. and the payload instruments include an atmospheric density detector(ADD), a dual-frequency dualmode global navigation satellite system(GNSS) receiver(GPS and Beidou), a satellite laser ranging(SLR) reflector, and an S/Xband very long baseline interferometry(VLBI) beacon. In this paper, we compare the GNSS precise orbit products with colocated SLR observations, and the 3 D orbit accuracy shows better than 10 cm RMS. These results reveal the great potential of the onboard micro-electro-mechanical system(MEMS) GNSS receiver. After calibrating ADD density estimates with precise orbit products, the accuracy of our density products can reach about 10% with respect to the background density. Density estimates from APOD are of a great importance for scientific studies on upper atmosphere variations and useful for model data assimilation. | Geshi TANG Xie LI Jianfeng CAO Shushi LIU Guangming CHEN Haijun MAN Xiaomin ZHANG Sihan SHI Ji SUN Yongping LI Andres CALABIA | 2020 | Science China Earth Sciences2020，63，2： | 0 |
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