Evaporation duct is an ubiquitous natural phenomenon over the ocean and can be diagnosed by evaporation duct model.The model proposed by Paulus and Jeske and another model established by the American naval postgraduat...Evaporation duct is an ubiquitous natural phenomenon over the ocean and can be diagnosed by evaporation duct model.The model proposed by Paulus and Jeske and another model established by the American naval postgraduate school are the most widely used.They are called PJ model and NPS model,respectively.Two methods are used to investigate the global sensitivity of PJ model and NPS model in China Seas.The first method is based on meteorological and oceanographic observation data in China Seas.Considering the system random error caused by sensor measurement inaccuracies,the mean relative error and mean absolute error are used as criterion for sensitivity analysis.The second method,called Extended Fourier Amplitude Sensitivity Test(EFAST),takes into account the interaction between input parameters and is used for sensitivity analysis.The results show that NPS model is more sensitive to the random errors of sensors than PJ model.The mean relative errors of PJ model and NPS model are 11.43%and 14.81%,respectively.The results of global sensitivity parameter analysis indicate that wind speed is the key factor of PJ model,while all input parameter of NPS model have relatively large total sensitivity index.In addition,sensitivity analysis results confirm that wind speed is one of main driving factors for the formation of evaporation duct.These results are valuable for the selection of diagnosis models for evaporation duct,the evaluation of radio wave propagation in the marine atmospheric surface layer,and the prediction technique of evaporation duct based on numerical weather prediction(NWP)in China seas.展开更多
Evaporation duct is an abnormal refractive phenomenon in the marine atmosphere boundary layer. It has been generally accepted that the evaporation duct prominently affects the performance of the electronic equipment o...Evaporation duct is an abnormal refractive phenomenon in the marine atmosphere boundary layer. It has been generally accepted that the evaporation duct prominently affects the performance of the electronic equipment over the sea because of its wide distribution and frequent occurrence. It has become a research focus of the navies all over the world. At present, the diagnostic models of the evaporation duct are all based on the Monin-Obukhov similarity theory, with only differences in the flux and character scale calculations in the surface layer. These models are applicable to the stationary and uniform open sea areas without considering the alongshore effect. This paper introduces the nonlinear factor a and the gust wind item wg into the Babin model, and thus extends the evaporation duct diagnostic model to the offshore area under extremely low wind speed. In addition, an evaporation duct prediction model is designed and coupled with the fifth generation mesoscale model （MMS）. The tower observational data and radar data at the Pingtan island of Fujian Province on May 25-26, 2002 were used to validate the forecast results. The outputs of the prediction model agree with the observations from 0 to 48 h. The relative error of the predicted evaporation duct height is 19.3% and the prediction results are consistent with the radar detection.展开更多
基金supported by the National Natural Science Foundation of China (No. 61471329)
文摘Evaporation duct is an ubiquitous natural phenomenon over the ocean and can be diagnosed by evaporation duct model.The model proposed by Paulus and Jeske and another model established by the American naval postgraduate school are the most widely used.They are called PJ model and NPS model,respectively.Two methods are used to investigate the global sensitivity of PJ model and NPS model in China Seas.The first method is based on meteorological and oceanographic observation data in China Seas.Considering the system random error caused by sensor measurement inaccuracies,the mean relative error and mean absolute error are used as criterion for sensitivity analysis.The second method,called Extended Fourier Amplitude Sensitivity Test(EFAST),takes into account the interaction between input parameters and is used for sensitivity analysis.The results show that NPS model is more sensitive to the random errors of sensors than PJ model.The mean relative errors of PJ model and NPS model are 11.43%and 14.81%,respectively.The results of global sensitivity parameter analysis indicate that wind speed is the key factor of PJ model,while all input parameter of NPS model have relatively large total sensitivity index.In addition,sensitivity analysis results confirm that wind speed is one of main driving factors for the formation of evaporation duct.These results are valuable for the selection of diagnosis models for evaporation duct,the evaluation of radio wave propagation in the marine atmospheric surface layer,and the prediction technique of evaporation duct based on numerical weather prediction(NWP)in China seas.
文摘Evaporation duct is an abnormal refractive phenomenon in the marine atmosphere boundary layer. It has been generally accepted that the evaporation duct prominently affects the performance of the electronic equipment over the sea because of its wide distribution and frequent occurrence. It has become a research focus of the navies all over the world. At present, the diagnostic models of the evaporation duct are all based on the Monin-Obukhov similarity theory, with only differences in the flux and character scale calculations in the surface layer. These models are applicable to the stationary and uniform open sea areas without considering the alongshore effect. This paper introduces the nonlinear factor a and the gust wind item wg into the Babin model, and thus extends the evaporation duct diagnostic model to the offshore area under extremely low wind speed. In addition, an evaporation duct prediction model is designed and coupled with the fifth generation mesoscale model （MMS）. The tower observational data and radar data at the Pingtan island of Fujian Province on May 25-26, 2002 were used to validate the forecast results. The outputs of the prediction model agree with the observations from 0 to 48 h. The relative error of the predicted evaporation duct height is 19.3% and the prediction results are consistent with the radar detection.
