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Liu H.,Nanjing University of Information Science and Technology | Bao Y.,Nanjing University of Information Science and Technology | Yuan C.,Jiangsu Meteorological Institute | Xie X.,Nanjing University of Information Science and Technology
Journal of Natural Disasters | Year: 2014

Based on the observed data of the automatic weather monitoring system (AWMS) in Jiangsu section of the Yangtze River waterway during 2009 to 2012, in this paper, the spatiotemporal distribution characteristic of strong breeze and strong crosswind was analyzed to explore the impact of the atmospheric background, geographical environment on the two kinds of winds, and the wind pressure early warning mechanism applied to the waterway was established. The results are as follows: (1) The diurnal and seasonal variations of the strong breeze and strong crosswind are similar. (2) The extreme maximum wind speed of every month is more than 10m/s, both of which reaches the standards of the maximum wind event and extreme strong wind event. (3) Different local geographic environments have different impact on the occurrence frequencies of strong crosswind in different parts of Jiangsu Section of the waterway. (4)The prevailing direction of the strong breeze mostly belongs to the strong crosswind. On the whole, the frequencies of northerly winds are higher than that of southerly winds, and the frequencies of westerly winds are higher than that of the easterly winds. (5) Considering the temporal and spatial variations of wind direction and speed, a four-grade early-warning system of wind pressure in the transportation of this waterway is preliminarily established. The back substitutions displayed that the spatial distribution of wind pressure in this 4 grades was closely related to the terrain. The highest wind pressure grades and the most early-warning times distribute in the middle part, next highest grade and frequencies distribute in the east part, and the lowest grades and the least frequencies of strong crosswind are in the western part. Source

Low-frequency rainfall over the lower reaches of Yangtze river valley (LYRV) and the principal component of the global 850 hPa meridional wind anomalies are adopted to construct an extended complex autoregressive (ECAR) model, which can be applied to the daily forecasting of the low-frequency rainfall component over LYRV in 2013 for the extended range forecast. Results show that this model for the forecasting of the 20-30-day rainfalls over LYRV has a good predictive skill up to 43 days, which is able to well predict the nonlinear enhancement processes of low-frequency rainfall component associated with heavy rainstorm process. And the correlation skill of the extended range forecast produced form the ECAR model is superior to the autoregressive model (AR) forecast. This method, in which the complex autoregressive (CAR) models are set up via constructing the extended complex matrix (ECM) for the principal low-frequency time series, provides a new description for the emerging dynamic processes of the interactions between components in climate systems. Based on the development and evolution of the principal 20-30-day oscillations of the global circulation, it is help for better forecast the process of heavy rainfall in the early October of 2013 over LYRV for times ahead of about 27 days. In these low-frequency variabilities, the 20-30-day oscillation in extratropics over the Southern Hemisphere is one of the main factors causing the changes of the heavy rainfall over LYRV for the extended range during the summer and fall in 2013. ©2014 Chinese Physical Society Source

Yang Q.,Jiangsu Meteorological Institute | Li Y.,Jiangsu Meteorological Institute | Song J.,Jiangsu Meteorological Institute | Huang S.,Jiangsu Meteorological Institute
Acta Meteorologica Sinica | Year: 2012

Daily 850-hPa meridional wind fields in East Asia from March to September 2002 were used to establish a model of the principal oscillation pattern (POP). This model was then used to conduct independent extended-range forecasts of the principal temporal and spatial variations in the low-frequency meridional wind field on a time scale of 20-30 days. These variations affect the occurrence of heavy precipitation events in the lower reaches of the Yangtze River valley (LYRV). The results of 135 forecast experiments during the summer half year show that the predicted and observed anomalies are strongly correlated at a lead time of 20 days (mean correlation greater than 0.50). This strong correlation indicates that the model is capable of accurately forecasting the low-frequency variations in meridional wind that corresponded to the 3 heavy precipitation events in the LYRV during the summer of 2002. Further forecast experiments based on data from multiple years with significant 20-30-day oscillations show that these prediction modes are effective tools for forecasting the space-time evolution of the low-frequency circulation. These findings offer potential for improving the accuracy of forecasts of heavy precipitation over the LYRV at lead times of 3-4 weeks. © The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg 2012. Source

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