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Archimedean Copulas function in arid Analysis

Author: ZhangYu
Tutor: SongSongBai
School: Northwest University of Science and Technology
Course: Hydrology and Water Resources
Keywords: Weihe Drought Characteristics Joint distribution Archimedean Copulas Functions
CLC: P333.1
Type: Master's thesis
Year: 2010
Downloads: 144
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Abstract


Based on Copulas function theory, select the Weihe 90 weather stations monthly precipitation data, the application of Archimedean Copulas function constructs the joint distribution of drought characteristic variables, analysis of the basin drought occurrence, the rational allocation of water resources for the Weihe River, water conservancy project planning, design and management, and drought mitigation study has important significance and guidance. This paper mainly achieved the following conclusions: (1) through the edge of the preferred distribution model and the Kolmogorov-Smirnov (KS) test, Weihe arid marginal distribution type characteristic variables were: drought duration with exponential distribution, drought intensity obey the Gamma distribution, intensity Peak obey generalized Pareto distribution based. (2) through the analysis of the correlation measure, Weihe each station as well as the peak intensity of drought intensity and drought duration and drought intensity exists between the high correlation; drought duration and intensity of the peak correlation between low. (3), respectively, using the maximum likelihood method and the fitting method for 20 kinds of two-dimensional Archimedean Copulas functions and four kinds of three-dimensional Archimedean Copulas function of the parameter estimates, and RMSE, AIC and Bias for the goodness of fit evaluation results showed that: Parameter estimation fitting method is better than the maximum likelihood method. (4) the right of the Weihe River is preferably applied Archimedean Copula function. Drought duration and drought intensity for the joint distribution, Gumbel Copula function in Tongchuan, Weinan, Xi'an, Xianyang and other regions of the optimal fitting effect, Frank Copula function fitting in Baoji optimal effect, for the entire Weihe 90 weather terms, Gumbel Copula function applicability best fit optimal effect. Drought duration and intensity of the peak for the joint distribution, Nelsen No 20 Copula function fitting in the whole Weihe best, followed by the effect of fitting followed Nelsen 13 Copula and Frank Copula function. Drought intensity and peak intensity for the joint distribution, Nelsen No 20 Copula function Baoji and Xianyang optimal degree of fit, but for the whole Weihe concerned, Clayton Copula function fitting optimal effect. For drought duration, drought intensity and peak intensity between the three-dimensional joint distribution, Clayton Copula function fitting optimal effect. (5) By optimizing out Archimedean Copula functions are established corresponding joint distribution of drought variable model to calculate the two-dimensional and three-dimensional case the joint probability of the case, the joint return period, with the current conditions of the return period and return period and draw the corresponding graph, can be found from the diagram under different combinations of probability and return period, the system can be analyzed to provide a basis Weihe drought characteristics. (6) For the two-dimensional distribution under the same conditions with the current joint return period is greater than the return period; For the three-dimensional distribution of the drought in the same variable under the same present value of the return period is greater than joint return period, given the Drought particular variable is greater than a certain value, etc. The other two variables of drought conditions combined return period greater than a given variable is less than or equal to this arid the same time to determine the value of the other two variables in terms of drought combined return period. (7) for many years the average monthly rainfall interception level variables drawn Weihe conditional probability of drought, shows a typical combination of conditions, spatial distribution of probability. Conditional probability P (S ≥ 100 / D ≥ 3), P (M ≥ 50 / D ≥ 3) the overall spatial distribution of the southeast to the northwest by increments; conditional probability P (S ≥ 100 / M ≥ 50) the spatial distribution characterized in Jinghe River upstream tributary of Weihe combined water, Qingyang, Xifeng, the original town, as well as Gansu Huating, Zhuanglang, Zhangjiachuan and Jingyuan County and other areas of the center, conditional probability to four weeks showed an increasing trend, in northwest regional growth trends over the southeast region growth was evident.

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CLC: > Astronomy,Earth Sciences > Geophysics > Hydrological Sciences (water sector physics) > Hydrological analysis and calculation > Water balance
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