A study of parameter uncertainties causing uncertainties in modeling a grassland ecosystem using the conditional nonlinear optimal perturbation method     

GuoDong Sun  DongDong Xie 《中国科学:地球科学(英文版)》2017,60(9):1674-1684

In this paper, we apply the approach of conditional nonlinear optimal perturbation related to the parameter (CNOP-P) to study parameter uncertainties that lead to the stability (maintenance or degradation) of a grassland ecosystem. The maintenance of the grassland ecosystem refers to the unchanged or increased quantity of living biomass and wilted biomass in the ecosystem, and the degradation of the grassland ecosystem refers to the reduction in the quantity of living biomass and wilted biomass or its transformation into a desert ecosystem. Based on a theoretical five-variable grassland ecosystem model, 32 physical model parameters are selected for numerical experiments. Two types of parameter uncertainties could be obtained. The first type of parameter uncertainty is the linear combination of each parameter uncertainty that is computed using the CNOP-P method. The second type is the parameter uncertainty from multi-parameter optimization using the CNOP-P method. The results show that for the 32 model parameters, at a given optimization time and with greater parameter uncertainty, the patterns of the two types of parameter uncertainties are different. The different patterns represent physical processes of soil wetness. This implies that the variations in soil wetness (surface layer and root zone) are the primary reasons for uncertainty in the maintenance or degradation of grassland ecosystems, especially for the soil moisture of the surface layer. The above results show that the CNOP-P method is a useful tool for discussing the abovementioned problems.  相似文献   

Scientific prospects for spectroscopy of the gamma-ray burst prompt emission with SVOM     

M. G. Bernardini  F. Xie  P. Sizun  F. Piron  Y. Dong  J.-L. Atteia  S. Antier  F. Daigne  O. Godet  B. Cordier  J. Wei 《Experimental Astronomy》2017,44(1):113-127

SVOM (Space-based multi-band astronomical Variable Objects Monitor) is a Sino-French space mission dedicated to the study of Gamma-Ray Bursts (GRBs) in the next decade, capable to detect and localise the GRB emission, and to follow its evolution in the high-energy and X-ray domains, and in the visible and NIR bands. The satellite carries two wide-field high-energy instruments: a coded-mask gamma-ray imager (ECLAIRs; 4–150 keV), and a gamma-ray spectrometer (GRM; 15–5500 keV) that, together, will characterise the GRB prompt emission spectrum over a wide energy range. In this paper we describe the performances of the ECLAIRs and GRM system with different populations of GRBs from existing catalogues, from the classical ones to those with a possible thermal component superimposed to their non-thermal emission. The combination of ECLAIRs and the GRM will provide new insights also on other GRB properties, as for example the spectral characterisation of the subclass of short GRBs showing an extended emission after the initial spike.  相似文献   

Coherent spectroscopy of a strongly driven triple quantum dot molecule     

解研  段素青  楚卫东  杨宁 《海洋学报(英文版)》2010,29(11)

Based on a calculation model, we study the interference phenomena of serially coupled V-type and Λ-type triple quantum dots (CTQDs) driven simultaneously by a strong driving field and a weak probe field. Strongly depending on the configuration of the three-level CTQD, the probe absorption spectra, which are shown in the tunneling current, exhibit various quantum coherence properties. In the case where the two pairs of transitions of the CTQD have a small eigenfrequency difference Δω, the double-coupling effect of the driving field results in two Autler-Townes doublets and one weak Mollow triplet in one spectrum. With the value of Δω increasing, only one Autler-Townes splitting remains due to the single-coupling of the field. We also find that the effect of spontaneous emission of phonons may lead to an obvious background current, which can be used to distinguish which transition is driven by the driving field in experiment. The interesting quantum property of a CTQD revealed in our results suggests its potential applications in quantum modulators and quantum logic devices.  相似文献   

Simulated various characteristic waves in acoustic full waveform relating to cement bond on the secondary interface     

Hongbing Zhang  Danyan Xie  Zuoping Shang  Xuebing Yang  Hongjian Wang  Honggen Tao 《Journal of Applied Geophysics》2011,73(2):139-154

Bad cement bond with water channeling or low strength cement is usually generated on the first and/or secondary interfaces which lie between the cement and casing, and the cement and formation, respectively. It is an inherently complicated problem to evaluate cement bond on the secondary interface (SICB) in a cased borehole. So we need to find a useful wave for evaluating SICB and provide its propagation features. To achieve this, we simulated the acoustic full waveform, 2-D spectrum and dispersion curves in cased boreholes based on the real axis integration method, and a propagator matrix. Simulation results indicated that “casing-cement mode” wave can be utilized to evaluate SICB, as it is most sensitive to water channeling on the secondary interface. Velocity of this mode wave is in between that of the casing wave and the formation wave, so that it is easy to extract it in time. The dispersion curves showed that the casing-cement wave is a dispersion wave, but not a pseudo-Rayleigh wave. Its velocity is obviously larger than v_s of cement. Simulation results further indicated that the amplitude of casing-cement wave is decreasing with increasing cement sheath thickness, but not water channeling thickness, and its travel time is influenced by casing and cement together. Moreover, we investigated factors influencing the casing–cement wave and found that casing diameter and peak frequency are major factors influencing the amplitude and the travel time, while other factors, such as P-wave velocities of cement and wall thickness of casing, are minor factors. But none of these factors greatly influence bond index which is computed from the amplitude. So the bond index has an advantage over the amplitude during evaluating SICB. Formation wave is a helpful signal to evaluate low strength cement without water channeling, and its amplitude is mainly related to the velocities (or impedances) of both cement and formation except for formation attenuation and disturbance wave. Experimental data in calibration pits and field data detecting channeling demonstrated the simulation results.  相似文献   

Decreasing predictability as a precursor indicator for abrupt climate change     

He  Wenping  Xie  Xiaoqiang  Mei  Ying  Wan  Shiquan  Zhao  Shanshan 《Climate Dynamics》2021,56(11):3899-3908

Abrupt climate change has an important impact on sustainable economic and social development, as well as ecosystem. However, it is very difficult to predict abrupt climate changes because the climate system is a complex and nonlinear system. In the present paper, the nonlinear local Lyapunov exponent (NLLE) is proposed as a new early warning signal for an abrupt climate change. The performance of NLLE as an early warning signal is first verified by those simulated abrupt changes based on four folding models. That is, NLLE in all experiments showed an almost monotonous increasing trend as a dynamic system approached its tipping point. For a well-studied abrupt climate change in North Pacific in 1976/1977, it is also found that NLLE shows an almost monotonous increasing trend since 1970 which give up to 6 years warning before the abrupt climate change. The limit of the predictability for a nonlinear dynamic system can be quantitatively estimated by NLLE, and lager NLLE of the system means less predictability. Therefore, the decreasing predictability may be an effective precursor indicator for abrupt climate change.

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Comparison in diversity of eukaryotic algae in surface sediments from different functional sea areas of Qingdao coast,the Yellow Sea,China: a metabarcoding approach     

Wang  Zhaohui  Lei  Mingdan  Ji  Shuanghui  Xie  Changliang  Chen  Jiazhuo  Li  Weiguo  Jiang  Tao 《中国海洋湖沼学报》2022,40(6):2322-2342

Journal of Oceanology and Limnology - Surface sediment samples were collected in three different functional sea areas in Qingdao coast, East China, including the inner Jiaozhou Bay, the Laoshan...  相似文献   

Summer Arctic sea fog     

Xie Simei  Xue Zhenhe  Jiang Dezhong  Zou Bin  Qu Shaohou 《海洋学报(英文版)》2001,20(2):183-196

I~IOXSea fog is a kind of dangerous weather. Chinese sea fog experts, Wang Binhua (1983),Hu Ruijin and Zhou Faxiu (1998) and Hu Jifu et al. (1996) studied sea fog rather Systematically. FOreign Experts also Paid great attention to sea fog. Ernlnons and Montgomery(1974), chipper (1994) and Rayrnond et al. (1989) have studied sea fog thorOUghly.HOwever, studies on Arctic sea ice have rarely been carried Out becauSe of the sever environment and less htnnan activity in the region. There …  相似文献   

东南亚10°—25°N,105°—130°E海区热带风暴异常路径的分析     

谢玲娟 《台湾海峡》1994,13(4):346-352

本文４１ａ（１９４９－１９８９年）的资料，对东南亚１０°－２５°Ｎ，１０５°－１３０°Ｅ范围７－９月出现的热带风暴异常路长进行了普查统计和气候分析。结果表明：产生异常路径热风暴的机率约占区域内热带风暴总数的２０％；异常路径的产生与热带风暴所处的地理位置，季节，环下等因素有关。正确地考虑气候规律和具体的天气条件相结合是预报带式风暴异常路径成败的关键。  相似文献   

A new type of Shipboard Meteorological Satellite Receiving-processing System   总被引：1，自引：0，他引：1  

Xie Simei  Hao Chunjiang  Zou Bin  Jing Qiyi  Liao Xiaohong  Sheng Xiaowen  Zhang Canrong 《海洋学报(英文版)》2000,19(1):35-46

INTRODUCTIONTheSMSRPSisstalledontheshipnavigatingovertheseaandreceivessatellitecloudmapsatanytimetoprovidereliablereal-timedataofmeteorologyandocean.Itisanimportantequipmentforsafeguardofshipnavigation.Chinahasthousandsofoceanicships.Butalmostallships,withonlyveryfewexception,arenotstalledbySMSRPS.Thecausesareasfollows:1.Thetechniqueisverycomplicated.2.Thedevelopmentcostisveryhigh.3.Ifweintroduceforeignequipment,thecostistooexpensive.4.Foreignequipmentanditssoftwarearecompletelyclo…  相似文献   

南极海冰与西北太平洋台风     

张林  薛振和 《海洋预报》1996,13(1):34-40

本文利用最大熵谱分别计算了南极４个区海冰和西北太平洋台风发生频数的变化周期，并对前３年的南极海冰强弱和当年的台风发生频率数进行了逐月时间序列相关分析。  相似文献