Search

This study hybridizes the background error covariance (BEC) of the hourly atmospheric three-dimensional variational data assimilation (3DVar) in Local Analysis (LA) operated at Japan Meteorological Agency using the flow-dependent BEC derived from the singular vector-based Mesoscale Ensemble Prediction System (MEPS) and the static BEC. The impact of introducing the hybrid BEC into the 3DVar is examined, along with its sensitivities to various factors like the ensemble size that is augmented by using lagged ensemble forecasts, the weight given to the ensemble-based component of BEC, the localization scales, and the use (or not) of the cross-variable correlation. This hybrid 3DVar system can be operated with small additional computational cost because it has no coupling with another ensemble data assimilation system. In sensitivity experiments, this hybrid 3DVar is shown to yield smaller forecast root mean square errors than the pure 3DVar, especially for surface variables. Moreover, the hybrid 3DVar shows a better equitable threat score for strong precipitation. These improvements were greater in the experiments with larger ensemble sizes that were increased by using lagged ensemble forecasts because of the reduced sampling errors in the ensemble-based BEC. These results were sensitive to the weight given to the ensemble-based BEC and the horizontal localization scale, whose optimal values were found to be approximately 0.5 and 100 km, respectively. The longer vertical correlation scale and the cross-variable correlation were also found important to create dynamically-balanced analysis, which is especially true for heavy rain cases. [ABSTRACT FROM AUTHOR]

The research conducted was aimed at developing a comprehensive method to evaluate the technical performance of an operator-centered Operation. The study was conducted under different water supply shortage conditions. The NekooAbad irrigation District was selected for simulation purposes using the Integral-Delay model to simulate flow distribution in the canals. The boundary conditions were based on historical statistics of surface water supply at the source. Seven scenarios were created, ranging from normal to severe water shortage. The technical assessment was based on two aspects: temporal analysis of the daily average water distribution adequacy in 13 main and 149 secondary off-takes. The second aspect included spatial analysis of the distribution of the mentioned index throughout the district. The study classified water distribution adequacy under each scenario. The results showed a pattern of reduced water distribution adequacy from the source to the downstream in all 13 secondary and the main canal. The daily average of the surface water distribution adequacy index ranged from over 10% in the normal scenario to less than 40% in the water scarcity scenarios. The percentage changes ranged from -95% to 64%, 90% to 56%, 89% to 54%, 89% to 50%, 86% to 49%, 86% to 46%, and 33% to 77%. The study also revealed a clear pattern of the operational system's inefficiency in the adequate distribution of surface water under water scarcity scenarios. Furthermore, it identified the vulnerable areas of the district through spatial regionalization maps of water distribution adequacy. [ABSTRACT FROM AUTHOR]

Comprehensive resilience management schemes are vital to urban risk governance and sustainable development. In this study, we decompose the urban physical system into the built environment subsystem (BES), information subsystem (IS), and metabolic flow subsystem (MFS), then construct a microscopic mechanism model of the urban system to quantify urban resilience, characterize the dynamics of urban resilience, and analyze the effect of network topology on urban resilience with the complex network method. The results provide several points: (1) There is a tipping point of the system, which crashes at 104.74% times the observed shock intensity in the case of Typhoon Morakot, taking the model parameters unchanged; (2) The topology of resource allocation network has a significant effect on urban resilience; (3) The externality of subsystem varies with the losses caused by negative shocks; and (4) The effects of network topology are contingent on the levels of urban resilience; therefore, for emergency management, city managers need to select resource allocation strategies based on urban resilience, by balancing the functional levels of operational and defensive parts. This study proposes a set of integrated management solutions based on resource deployment relationships among subsystems that can help urban systems better cope with shocks and increase resilience. • A new, multi-dimensional approach to urban resilience assessment was developed. • The topology of resource allocation network was validated as effective for urban resilience. • BES provides an important foundation and plays a stable role in the construction of urban resilience. • Resource allocation should adjust with resilience changes during shock periods. • A cross-system emergency management solution was constructed to cope with shocks. [ABSTRACT FROM AUTHOR]