A method for estimating the wind speed of a great wind in a northern offshore sea area

Abstract

The application belongs to the technical field of meteorological detection, and particularly relates to a method for estimating maximum wind speed in northern offshore sea area, wherein an initial field of maximum wind speed prediction is built based on an EC-thin mode predicted wind field and a multi-source observed actual wind field, and terrain amplification correction is based on different times, different regions and different wind directions. The method for estimating maximum wind speed provided by the application is obtained without relying on personal experience, and is more objective and quantitative, which not only reduces dynamic error of a numerical prediction mode, but also reduces missed reports of strong wind caused by weak cold air, and the terrain wind speed amplification further accurately and finely predicts the distribution of a mesoscale strong wind area, so that the prediction result is closer to the actual situation.

Description

Technical Field

[0001] This invention belongs to the field of meteorological detection technology, specifically relating to a method for estimating the maximum wind speed in northern coastal waters. Background Technology

[0002] The Yellow and Bohai Seas are important sea areas for my country's shipping, energy development, and marine fisheries. Their combined continental and maritime climate characteristics lead to frequent strong wind disasters in both the sea areas and along the coast. Winds with an average wind speed of 6 or higher (10.8–13.8 m / s) are classified as strong winds, with the most severe damage typically caused by the highest wind speeds within a specific time period. Along the northern coast of the Bohai and Yellow Seas, there are nearly 80 days a year with maximum wind speeds of 6 or higher, and nearly 70 days with wind speeds of 8 or higher (≥17.2 m / s), with some exceeding 100 days. Strong winds are a dangerous weather phenomenon in the northern sea areas and their coastal regions, seriously affecting maritime transport, offshore operations, and marine resource development such as aquaculture. With the development of the coastal economy in the northern sea areas, accurate forecasting of strong winds is of great importance.

[0003] Currently, methods for forecasting maximum wind speeds include statistical methods, meteorological methods, numerical weather prediction methods, and numerical weather prediction correction methods. Statistical methods typically use air pressure, temperature, wind direction, and wind speed as independent variables, establishing a mathematical expression for maximum wind speed and meteorological influencing factors through multiple regression, and using this as the forecast for maximum wind speed. However, this method neglects the influence of different underlying surfaces on strong winds, and its accuracy needs improvement.

[0004] The meteorological method conducts meteorological classification and diagnostic studies based on the main surface influencing systems and upper-level circulation characteristics that cause strong winds, extracts forecast indicators under different influencing systems, and combines this with actual coastal wind conditions to predict maximum wind speeds. This method provides an in-depth study of the weather background and physical processes that trigger strong winds. However, similar to statistical methods, it cannot consider the amplifying effect of the underlying surface on wind speeds, and it relies heavily on the subjective experience of forecasters, as individual differences among forecasters significantly affect forecast accuracy.

[0005] Numerical weather prediction (NMR) methods utilize partial differential equations describing atmospheric motion characteristics and the mathematical relationships between wind speed and meteorological influencing factors to perform numerical calculations. It is an objective, quantitative, and refined forecasting method, widely used in operational gale forecasting. However, because the parameterization schemes relied upon by various models do not fully describe the underlying surface, air-sea coupling, and mesoscale physical processes of maximum winds, the maximum wind speeds output by the models deviate significantly from the actual wind fields. Therefore, the accuracy of these models still falls short of the requirements for forecasting and early warning.

[0006] Numerical weather forecast correction methods often utilize multi-source data, including wind fields retrieved from coastal monitoring stations, offshore oil platform stations, island stations, buoy stations, and remote sensing products in northern sea areas. Based on different models and algorithms, they correct biases on gust forecasts, determine weighting coefficients, and establish forecast equations. While this method incorporates field corrections, it relies heavily on numerical weather forecast products and shares the limitations of traditional numerical weather forecast methods. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a method for estimating maximum wind speeds in northern coastal waters. This forecasting method considers both strong and weak cold air storms, as well as the increase in wind speeds within mesoscale strong wind zones, thereby improving the accuracy of gale forecasts in northern sea areas.

[0008] This invention is implemented by providing a method for estimating the maximum wind speed in northern coastal waters, comprising the following steps:

[0009] Step 1): Based on the comparison between the actual wind speed of the maximum wind field in the northern coastal waters and the wind speed predicted by the EC-thin model under different pressure conditions, select the pressure condition with the wind speed that has the smallest average absolute error with the actual wind speed of the maximum wind field.

[0010] Step 2): Select the actual wind speeds measured by several radiosonde stations in the northern coastal waters under the pressure conditions selected in Step 1), and compare them with the wind speeds at the same time and at the same pressure conditions predicted by the EC-thin model, and calculate the wind speed deviations.

[0011] Step 3): Using the wind speed deviation obtained in Step 2), the wind speed at the grid point closest to several radiosonde stations under the same pressure conditions predicted by the EC-thin model at the next moment is corrected. The corrected grid point wind field data is used as the initial forecast field for maximum wind in the northern coastal waters.

[0012] Step 4): Based on the different topographic conditions of the northern coastal waters and the amplification effect of different wind directions at different times of the year on the maximum wind, different dynamic amplification thresholds are set. The gridded wind field data of the initial forecast field of the maximum wind obtained in Step 3) is corrected using the dynamic amplification thresholds to estimate the wind speed of the maximum wind in the northern coastal waters.

[0013] Preferably, in step 1), the actual wind speed of the maximum wind field measured by automatic stations, island stations, buoy stations and drilling platform stations in the northern coastal waters is compared with the gust wind speed, 925hPa and 850hPa wind speed predicted by the EC-thin model. The wind speed under the 925hPa pressure condition has the smallest average absolute error with the actual wind speed of the maximum wind field.

[0014] Compared with the prior art, the advantages of the present invention are as follows:

[0015] The initial field for maximum wind speed forecast is built based on the wind field forecast by the EC-thin model and the actual wind field observed by multiple sources. The acquisition process does not rely on personal experience, making it more objective and quantitative. The topographic amplification correction is based on different times, regions, and wind directions, which reduces the dynamic error of numerical forecast models and reduces the underreporting of strong winds caused by weak cold air. Furthermore, the topographic wind speed amplification further accurately and precisely forecasts the distribution of mesoscale strong wind areas, making the forecast results closer to reality. Detailed Implementation

[0016] The present invention will be further explained below with reference to specific implementation schemes, but this is not intended to limit the scope of protection of the present invention.

[0017] The triggering mechanism for northerly gales in the northern sea areas is the movement across isobars in a large-scale environmental field. Whether the gales are sustained depends primarily on the kinetic energy and vorticity conversion between lower-level synoptic and subsynoptic scale systems. When the lower atmosphere gains kinetic energy and consumes positive vorticity, it facilitates the replenishment of surface kinetic energy, thus maintaining or even amplifying gales in areas receiving kinetic energy. Conversely, when kinetic energy is consumed, the gales cease. Simultaneously, the topography of the Bohai Rim region amplifies southerly gales in the Bohai Sea and northerly gales in the northern Yellow Sea, while the topography of the Shandong Peninsula amplifies both southerly and northerly gales in the Bohai Strait and the northern Yellow Sea. The amplification is greatest in the northeastern Bohai Sea and the northeastern Shandong Peninsula, reaching up to 4 m / s, while the amplification is 2 m / s in the eastern Liaodong Peninsula and the northeastern Shandong Peninsula.

[0018] During periods of strong winds, distinct subsynoptic-scale fluctuations were observed over the northern sea areas. Strong divergence, propagating from the middle and lower atmosphere down to below the boundary layer, was a key factor in triggering and sustaining strong winds. The boundary layer received significantly increased kinetic energy from subsynoptic-scale systems, leading to mesoscale strong wind regions along the coast. The boundary layer's consumption of subsynoptic-scale positive vorticity and gain of kinetic energy further facilitated the formation, maintenance, and even amplification of strong winds. The amount of kinetic energy gained by the lower atmosphere below 850 hPa from subsynoptic-scale systems was closely related to the intensity of the northerly winds.

[0019] A comparative analysis was conducted based on the actual maximum wind field data from automatic weather stations, island stations, buoy stations, and drilling platform stations along the Yellow and Bohai Seas, and the gust wind speeds, 925 hPa wind speeds, and 850 hPa wind speeds predicted by the European Centre for Medium-Range Weather Forecasts (EC-thin) model. The results showed that the average absolute error between the 925 hPa wind speed and the maximum wind speed was the smallest, and the correlation was the best. First, the actual wind speeds at 925 hPa from three radiosonde stations (Dalian, Jinzhou, and Rongcheng) along the northern coast were extracted. These wind speeds were then compared with the wind speeds predicted by the EC-thin model at the three nearest 925 hPa grid points (121.5°E, 41.25°N, 121.5°E, 39.0°N, 122.25°E, 37.5°N) at the same time. The wind speed difference was calculated, and the wind speed deviation was used to correct the deviation of the 925 hPa grid point wind speed at the next moment. The corrected 925 hPa grid point wind field data was then used as the initial forecast field for maximum winds in the northern sea area.

[0020] Coastal topography in northern sea areas significantly amplifies strong winds. The topography of the Liaodong Peninsula amplifies southerly winds in the Bohai Sea and northerly winds in the northern Yellow Sea, while the topography of the Shandong Peninsula amplifies both southerly and northerly winds in the Bohai Strait and the northern Yellow Sea. The amplification is greatest in the northern Bohai Sea and the northeastern Shandong Peninsula, reaching 4 m / s, while the amplification is 2 m / s in the eastern Liaodong Peninsula and the northeastern Shandong Peninsula. The amplification effect of coastal topography on strong winds in northern sea areas varies seasonally; therefore, a dynamic amplification threshold is used for grid point correction. From November to March of the following year, the effect of topographic amplification is significantly higher than in other seasons. Amplification is applied to the corrected 925hPa grid wind speed by sea area and wind direction. When there are northerly winds, the wind speed in the Bohai Sea increases by 2-4 m / s, while the wind speed in the Bohai Strait and the northern Yellow Sea increases by 4-6 m / s. When there are southerly winds, the wind speed in the Bohai Sea increases by 2-4 m / s, while the wind speed in the Bohai Strait and the northern Yellow Sea remains the same as the 925hPa grid wind speed. From April to October, the maximum wind speed in each sea area remains the same as the corrected 925hPa grid wind speed.

[0021] Combining the aforementioned forecasting method, the 925 hPa wind speed is corrected based on EC-thin. The corrected 925 hPa wind speed is used as the initial forecast field for the maximum wind speed. Wind speed amplification corrections are made for different seasons, different sea areas, and different wind directions to finally determine the maximum wind speed.

[0022] Example 1

[0023] In daily wind forecasts, northerly winds triggered by strong or weak cold air masses over northern sea areas in winter are prone to being overestimated or missed. From 01:00 to evening on April 4, 2020; from 20:00 to evening on March 5, 2021; from 01:00 to 21:00 on January 19, 2022; from 08:00 to 17:00 on February 26, 2022; and from 20:00 on March 18, 2022 to 09:00 on March 19, 2022, northerly winds occurred in the Bohai Sea, the Bohai Strait, and the northern Yellow Sea. The maximum gusts reached level 8-9 in the first four instances and level 9-11 in the fifth. For these five gale events, the numerical weather prediction products provided accurate forecasts of the surface pressure field. For the first two gale events, the model forecasts indicated average northerly winds of force 5-6 with gusts of force 7-8 over the Yellow and Bohai Seas. For the latter three gale events, the model forecasts indicated average northerly winds of force 6-7 with gusts of force 8-9 over the Yellow and Bohai Seas. There were significant discrepancies between the numerical and empirical forecasts and the actual conditions.

[0024] During the five gale events, the boundary layer atmosphere in the Yellow and Bohai Sea regions consumed sub-synoptic-scale positive vorticity, gaining kinetic energy, which was conducive to the formation, maintenance, and even amplification of the gales.

[0025] Using the correction method described in this invention, the 925 hPa wind speed is corrected based on EC-thin, and the corrected 925 hPa wind speed is used as the initial forecast field for the maximum wind speed. Based on the occurrence time and wind direction of several gale events, wind speed amplification corrections are made for different sea areas, ultimately determining the maximum wind speeds for the first four events to be 20–24 m / s (level 8–9), and the last to be 24–30 m / s (level 9–11), which is closer to the actual wind speed. Based on numerical forecast products of the lower tropospheric wind field and divergence field, and utilizing the sub-synoptic-scale characteristics of kinetic energy and vorticity conversion during winter northerly gales in the Yellow and Bohai Seas, and according to the characteristics of the Yellow and Bohai Sea coastlines and the correction threshold for gales in the forecast sea areas, a quantitative forecast of gales in the Yellow and Bohai Seas is output. This improves the applicability of numerical forecast products to gales in the Yellow and Bohai Seas, thereby improving the accuracy of gale forecasts in northern sea areas.

Claims

1. A method for estimating the maximum wind speed in northern coastal waters, characterized in that, Includes the following steps: Step 1): Based on the comparison between the actual wind speed of the maximum wind field in the northern coastal waters and the wind speed predicted by the EC-thin model under different pressure conditions, select the pressure condition with the wind speed that has the smallest average absolute error with the actual wind speed of the maximum wind field. Step 2): Select the actual wind speeds measured by several radiosonde stations in the northern coastal waters under the pressure conditions selected in Step 1), and compare them with the wind speeds at the same time and at the same pressure conditions predicted by the EC-thin model, and calculate the wind speed deviations. Step 3): Using the wind speed deviation obtained in Step 2), the wind speed at the grid point closest to several radiosonde stations under the same pressure conditions predicted by the EC-thin model at the next moment is corrected. The corrected grid point wind field data is used as the initial forecast field for maximum wind in the northern coastal waters. Step 4): Based on the different topographic conditions of the northern coastal waters and the amplification effect of different wind directions at different times of the year on the maximum wind, different dynamic amplification thresholds are set. The gridded wind field data of the initial forecast field of the maximum wind obtained in Step 3) is corrected using the dynamic amplification thresholds to estimate the wind speed of the maximum wind in the northern coastal waters.

2. The method for estimating the maximum wind speed in the northern coastal waters according to claim 1, characterized in that, In step 1), the actual wind speed of the maximum wind field measured by automatic stations, island stations, buoy stations and drilling platform stations in the northern coastal waters is compared with the gust wind speed, 925 hPa and 850 hPa wind speed predicted by the EC-thin model. The wind speed under the 925 hPa pressure condition has the smallest average absolute error with the actual wind speed of the maximum wind field.