A method for monitoring double indexes of south china sea summer monsoon based on FY-2 polar orbit meteorological satellite

Abstract

The application discloses a kind of based on Fengyun polar orbit meteorological satellite South China Sea summer monsoon double-index monitoring method, this method obtains 850hPa atmospheric temperature and specific humidity by polar orbit meteorological satellite FY-3D vertical detection instrument group VASS, 850hPa false equivalent potential temperature index is calculated;Ocean surface wind speed and wind direction are obtained by ocean surface wind field data of the wind field measurement radar WindRAD inversion of polar orbit meteorological satellite FY-3E, average zonal wind index is calculated;By evaluating the accuracy of FY-3D / VASS temperature and specific humidity relative to ERA5, and the accuracy of ocean surface wind of FY-3E / WindRAD relative to MetOp-C / ASCAT is evaluated index, the accuracy of the double-index monitoring South China Sea summer monsoon outbreak process is verified from the evaluation result.The application uses FY-3D to calculate false equivalent potential temperature and FY-3E ocean surface wind double-index monitoring South China Sea summer monsoon, double-index is well monitored 2022 South China Sea summer monsoon outbreak process temperature and humidity field and wind field conversion, so as to verify the application ability of two kinds of satellite data in South China Sea summer monsoon climate monitoring.

Description

Technical Field

[0001] This invention relates to the field of meteorological data monitoring and forecasting technology, and in particular to a dual-indicator monitoring method for the South China Sea summer monsoon based on Fengyun polar-orbiting meteorological satellites. Background Technology

[0002] Asia and Australia are typical monsoon regions, forming the Australasian monsoon system. The onset of the Asian summer monsoon indicates a shift in atmospheric circulation from a winter-type to a summer-type. The Asian summer monsoon is divided into the tropical summer monsoon and the subtropical summer monsoon. The onset of the tropical summer monsoon generally goes through three stages. Typically, the Asian summer monsoon first establishes itself in the southern Bay of Bengal, then moves eastward across the Indochina Peninsula, extending to the South China Sea summer monsoon region by mid-May, and finally, the South Asian summer monsoon intensifies. The onset of the South China Sea summer monsoon indicates the beginning of the East Asian subtropical summer monsoon and the start of the main rainy season. The timing of the South China Sea summer monsoon's onset is an important indicator of climate anomalies in China.

[0003] Currently, most meteorological monitoring indicators for the South China Sea summer monsoon region are defined using meteorological numerical model data. The accuracy of these indicators is affected by model performance, leading to discrepancies with actual observations. Secondly, the satellite cloud-guided wind and TBB (Total Bipolar Wind) indicators currently used in operations provide accurate observations of upper-level wind fields and convective activity in the South China Sea summer monsoon region, effectively reflecting the monsoon's activity characteristics. However, cloud-guided wind only provides information on upper-tropospheric wind direction changes and cannot capture lower-tropospheric wind direction changes, which are crucial during the onset of the South China Sea summer monsoon. There is currently no satisfactory solution for using lower-tropospheric indicators to monitor the South China Sea summer monsoon. Summary of the Invention

[0004] The purpose of this invention is to provide a dual-indicator monitoring method for the South China Sea summer monsoon based on Fengyun polar-orbiting meteorological satellites, so as to solve the practical problems existing in the above-mentioned prior art.

[0005] To achieve the above objectives, this invention provides a dual-indicator monitoring method for the South China Sea summer monsoon based on Fengyun polar-orbiting meteorological satellites, mainly comprising the following steps:

[0006] S1. The atmospheric temperature and specific humidity at 850 hPa were obtained by the VASS instrument group of the polar-orbiting meteorological satellite FY-3D, and the data were processed into daily average data to calculate the pseudo equivalent potential temperature index at 850 hPa.

[0007] S2, uses the WindRAD radar of the polar-orbiting meteorological satellite FY-3E to acquire ocean wind field data, processes it into daily average data, obtains ocean wind speed and direction, and obtains average zonal wind index;

[0008] S3, assess the accuracy of FY-3D / VASS temperature and specific humidity relative to ERA5 data;

[0009] S4, Evaluate the accuracy of FY-3E / WindRAD ocean winds relative to Metop-C / ASCAT data;

[0010] S5 is used to verify the accuracy of monitoring the onset of the South China Sea summer monsoon using the dual indicators S1 and S2, based on the evaluation results of S3 and S4.

[0011] Furthermore, the South China Sea summer monsoon region is (10°N-20°N; 110°E-120°E).

[0012] Furthermore, the daily average data needs to be spatially gridded within the South China Sea summer monsoon region.

[0013] Furthermore, the calculation formula for the accuracy evaluation index mentioned in S3 and S4 is as follows:

[0014]

[0015] Where Y is the variable being tested, X is the reference value variable, and n is the matched sample size. Let n be the average of the tested variables. The average value of the reference variable for testing n samples.

[0016] Furthermore, in S3, comparing FY-3D / VASS and ERA5, the pseudo-equivalent potential temperature distribution and seasonal progression trend are consistent, thus the Fengyun polar-orbiting meteorological satellite can monitor the changes in atmospheric temperature and humidity index during the onset of the South China Sea summer monsoon.

[0017] Furthermore, in S4, comparing FY-3E / WindRAD and Metop-C / ASCAT, the ocean surface wind flow field distribution is consistent, and the location and intensity of the high wind speed area are similar. Thus, the Fengyun polar-orbiting meteorological satellite can monitor the wind field transformation characteristics during the onset of the South China Sea summer monsoon.

[0018] Furthermore, the accuracy of monitoring the onset process of the South China Sea summer monsoon using both S1 and S2 indicators was compared and verified with the onset time of the South China Sea summer monsoon published operationally by the National Climate Center.

[0019] Furthermore, when the polar-orbiting meteorological satellite monitors global coverage, the average FY-3D pseudo-equivalent potential temperature and FY-3E ocean wind distribution can also be used to monitor cross-equatorial airflow, warm and humid water vapor transport, tropical depressions or cyclones in the southern Indian Ocean, vortices or cyclones in the Bay of Bengal, and the triggering effect of synoptic-scale systems on the onset of the summer monsoon, which are important indicators of the establishment of the Asian summer monsoon before the outbreak of the South China Sea summer monsoon.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] (1) The activity characteristics of the South China Sea summer monsoon are monitored by using temperature, humidity and ocean wind (low-level wind) retrieved from the FY-3 polar-orbiting meteorological satellite, thereby enabling the monitoring of different meteorological elements during the South China Sea summer monsoon activity. This invention will add the low-level tropospheric ocean wind field index and temperature and humidity index to the monitoring of South China Sea summer monsoon activity based on satellite remote sensing cloud-guided wind and TBB dual indexes, so as to have a more comprehensive identification of the intensity information of the summer monsoon outbreak and activity process.

[0022] (2) For the first time, the observation data of FY-3 satellite was applied to summer monsoon monitoring. The evaluation of FY-3E ocean wind was added, and the inversion products of similar instruments of European meteorological satellites were selected as the verification source. The influence of the diurnal variation characteristics of wind speed on the verification results was also considered. Attached Figure Description

[0023] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0024] Figure 1 A flowchart of a dual-indicator monitoring method for the South China Sea summer monsoon based on Fengyun polar-orbiting meteorological satellites is provided for an embodiment of the present invention.

[0025] Figure 2 The present invention provides scatter plot density and evaluation index of FY-3D / VASS and ERA5850hPa temperature in the South China Sea summer monsoon region in April, May and June 2022 for embodiments of the present invention.

[0026] Figure 3 The FY-3D / VASS and ERA5850hPa specific humidity scatter plots and evaluation indicators for the South China Sea summer monsoon region from April to June 2022 are provided for embodiments of the present invention.

[0027] Figure 4 The pseudo-equivalent potential temperatures of FY-3D / VASS and ERA5 from April to June 2022 provided for embodiments of the present invention;

[0028] Figure 5 Scatter plots of ocean winds in the South China Sea summer monsoon region from April to June 2022 (FY-3E / WindRAD and MetOp-C / ASCAT) provided for embodiments of the present invention;

[0029] Figure 6 Scatter plots of ocean winds (FY-3E / WindRAD and MetOp-C / ASCAT) in the South China Sea summer monsoon region from April to June 2022, provided for embodiments of the present invention;

[0030] Figure 7Scattered wind speeds over the South China Sea summer monsoon region from April to June 2022 (FY-3E / WindRAD and MetOp-C / ASCAT) provided for embodiments of the present invention.

[0031] Figure 8 The monthly average ocean winds and wind speeds for FY-3E / WindRAD and MetOp-C / ASCAT from April to June 2022 are provided for embodiments of the present invention.

[0032] Figure 9 The monthly average ocean surface wind speed deviations for FY-3E / WindRAD and MetOp-C / ASCAT from April to June 2022, provided for embodiments of the present invention;

[0033] Figure 10 The following data are provided for embodiments of the present invention: the average 850 hPa FY-3D / VASS and ERA 5-day average pseudo equivalent potential temperatures in the South China Sea summer monsoon region from March 1 to September 30, 2022 (a), FY-3E / WindRAD, MetOp-C / ASCAT ocean winds and ERA 5-day average zonal winds (b).

[0034] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] The onset of the Asian tropical summer monsoon occurs over ocean surfaces where conventional observation data is scarce. Satellites can provide real-time information on atmospheric parameters, cloud parameters, and precipitation covering the entire region for monitoring summer monsoon activity. Previous satellite monitoring of the South China Sea summer monsoon primarily utilized parameters such as cloud top brightness temperature, precipitation, and cloud-guided winds for applied research. However, the vertical sounding instruments onboard the Fengyun polar-orbiting meteorological satellite can effectively observe three-dimensional atmospheric temperature and humidity under all-weather conditions and have played a crucial role in monitoring extreme weather events. The application of this observational data in monitoring the South China Sea summer monsoon has great potential. The wind field measurement radar onboard the FY-3E meteorological satellite, launched in 2021, can observe global ocean surface wind fields. Previous data analysis shows that, compared to the 850 hPa wind field, changes in ocean surface and near-surface winds better characterize the features of various Asian monsoon systems. Therefore, this embodiment of the invention will also evaluate the application capability of FY-3E ocean surface winds in monitoring the South China Sea summer monsoon. The monitoring application capability of the South China Sea summer monsoon based on the Fengyun polar-orbiting meteorological satellite is verified through dual indicators. The flowchart is as follows: Figure 1 .

[0037] The FY-3D meteorological satellite was launched on November 15, 2017. This paper uses temperature and humidity data retrieved from the Vertical Atmospheric Sounding System (FY-3D / VASS) instrument group of the Fengyun-3D satellite. This vertical observation instrument group consists of three instruments: a 4-channel Microwave Humidity Sounder (MWHS), a 5-channel Microwave Temperature Sounder (MWTS), and a 26-channel Infrared Atmospheric Sounder (IRAS). The VASS temperature and humidity data covers the globe, with a nadir spatial resolution of 15 km. Vertically, it covers 43 pressure layers from 1013.25 hPa at the ground to 0.1 hPa at high altitude. In this embodiment, the pressure layer selected is 839.95 hPa. Stable and reliable FY-3D / VASS temperature and humidity retrieval data began in April 2019.

[0038] The FY-3E meteorological satellite was successfully launched in July 2021 and is the world's first civilian meteorological satellite in a dawn-dusk orbit. The satellite carries 11 sets of remote sensing instruments, including 3 newly developed, 7 upgraded, and 1 inherited from existing systems. The FY-3E satellite achieves a combined active and passive ocean surface wind field detection capability, featuring a newly added dual-frequency wind field measurement radar. This is the first active remote sensing instrument carried on the Fengyun series of meteorological satellites, providing high-precision measurements of global ocean surface wind fields, including wind speed and direction. The wind field measurement radar acquires global ocean surface wind field information, including wind speed and direction, through backscattering measurements of the Earth system. The wind field measurement radar is a dual-frequency, dual-polarization conical scanning radar, achieving high-precision wind field measurements through on-board internal calibration and on-orbit active external calibration. It operates on two frequencies, C-band (5.3 GHz) and Ku-band (13.265 GHz), with four antennas, both frequencies featuring both HH and VV modes. Each pixel emits light from multiple perspectives. The minimum detectable wind speed is 3 m / s. This invention utilizes ocean wind data from a wind field measurement radar. This data is daily, divided into ascending (dusk) and descending (early morning) phases. The data is presented as equal-latitude and longitude grids (0.25° × 0.25°), covering the global ocean surface. This paper processes the daily ascending and descending data into daily averages. The observation times for the South China Sea summer monsoon region are approximately 10:00 PM (UTC) and 10:00 PM.

[0039] The following three conditions must be met for the South China Sea summer monsoon to occur:

[0040] 1) The event occurs at or after the 25th day of the lunar month;

[0041] 2) The average zonal wind over the South China Sea summer monsoon monitoring area is greater than zero and lasts for at least two pentads (including two pentads);

[0042] 3) The average 850 hPa pseudo-equivalent potential temperature in the South China Sea summer monsoon monitoring area is greater than or equal to 340 K and lasts for at least 2 pentads (including 2 pentads). At this time, most of the atmosphere in the South China Sea summer monsoon monitoring area is stable and exhibits high temperature and high humidity characteristics.

[0043] Description of the two data sources used for comparative analysis in the examples:

[0044] In this embodiment of the invention, the temperature, humidity, and wind field data used in the ERA5 reanalysis data are all from the European Centre for Medium-Range Weather Forecasts (ECWMF) reanalysis dataset (ERA5). This dataset integrates model and global observation data, with a horizontal spatial resolution of 0.25° (longitude) × 0.25° (latitude) and a temporal resolution of 1 hour. In this embodiment of the invention, the data is processed into daily average data, and the pressure layer used is 850 hPa.

[0045] The ASCAT scatterometer used in this embodiment of the invention is one of the instruments carried by the Metop polar satellite, an operational meteorological satellite launched by the European Space Agency (ESA) and operated by the European Union Meteorological Satellite Organization (EUMETSAT). Metop-C was launched on November 7, 2018, and provides the equivalent horizontal stress wind vector at a height of 10m, including wind speed and direction. Wind speed is measured in meters per second (m / s). The wind speed range is 0-50 m / s, but wind speeds exceeding 25 m / s are generally less reliable. The standard deviation of the wind component should be better than 2 m / s, and the wind speed deviation should be less than 0.5 m / s. The spatial resolution is approximately 12.5 km, with coverage twice a day. In this embodiment, the data is processed to a daily average resolution of 0.25° × 0.25°. Observations of the South China Sea summer monsoon region are conducted around 02:00 AM (UTC) and around 14:00 PM.

[0046] This invention utilizes operational South China Sea summer monsoon monitoring indicators from the National Climate Center for application evaluation, including the 850 hPa pseudo-equivalent potential temperature indicator and the sea surface zonal wind indicator. The pseudo-equivalent potential temperature is calculated as follows:

[0047] e = prs × q / (0.62197 + q)

[0048] tlcl=55.0+2840.0 / (3.5×logT-loge-4.805)

[0049] θ = T × (1000 / prs) 0.2854×(1.0-0.28×q)

[0050]

[0051] Where, θ se The values ​​are: pseudo-equivalent potential temperature, θ, prs = 850 hPa, T, temperature (K), and q, specific humidity (kg / kg). The South China Sea summer monsoon region is (10°N-20°N; 110°E-120°E). The pseudo-equivalent potential temperature index of the South China Sea summer monsoon is the regional average 850 hPa pseudo-equivalent potential temperature, and the wind field index of the South China Sea summer monsoon is the regional average zonal wind average over the sea surface.

[0052] The following evaluation metrics are calculated using the formulas for mean deviation (MB), mean absolute error (MAE), root mean square error (RMSE), and correlation coefficient (CC):

[0053]

[0054] Where Y is the variable being tested, X is the reference value variable, and n is the matched sample size. Let n be the average of the tested variables. The average value of the reference variable for testing n samples.

[0055] The first example assesses temperature and humidity using the FY-3D / VASS instrument cluster for monitoring the South China Sea summer monsoon. The timeframe for this example is April 1st to June 30th, 2022, covering the entire onset of the 2022 South China Sea summer monsoon. Atmospheric temperature and specific humidity at 850 hPa were acquired using the FY-3D polar-orbiting meteorological satellite's vertical sounding instrument cluster (VASS), and processed into daily average data to calculate the pseudo-equivalent potential temperature index at 850 hPa.

[0056] Then, based on the above evaluation index calculation formula, the scatter plots of 850hPa FY-3D / VASS temperature and ERA5 temperature for April, May, and June 2022, and the evaluation indexes are shown. Figure 2 The number of matched samples in April, May, and June was approximately 80,000, with May having the largest number at 86,000. April had the smallest mean deviation and mean absolute error (MAO) at -0.39 and 1.02℃ respectively, and the largest correlation coefficient at 0.46. May had a mean deviation of -0.73, an absolute mean deviation of 1.11℃, and the smallest root mean square error (RMSE) at 1.55℃. June had the smallest correlation coefficient at 0.27. Overall, the average distribution from April to June showed samples with abnormally high or low 850hPa temperatures in FY-3D / VASS, with an average deviation of 0.6℃ lower, a mean absolute deviation of 1.1℃, and an RMS error of 1.6℃.

[0057] The 850hPa FY-3D / VASS specific humidity and ERA5 specific humidity scatter plots and evaluation indices for April, May and June 2022 show ( Figure 3 The correlation coefficient and scatter distribution of specific humidity deviated from the temperature, with samples showing abnormally high and low specific humidity from April to June, indicating an overall low specific humidity. In May and June, the correlation coefficients were relatively low, and the high scatter density was distributed below the trend line. The average deviation in June was relatively small at -0.15 g / kg. The average deviation from April to June was -0.53 g / kg, with a mean absolute error of 2.25 g / kg and a root mean square error of 2.97 g / kg.

[0058] The average temperature and specific humidity at 850 hPa in the South China Sea summer monsoon region from April to June, as measured by FY-3D / VASS, are generally lower than those of ERA5. Using the FY-3D / VASS temperature and humidity data and the formula above, the 850 hPa pseudo-equivalent potential temperature distribution shows that an average pseudo-equivalent potential temperature of 340 K at 850 hPa can be used as an indicator of the onset of the South China Sea summer monsoon. Therefore, a comparative analysis of the 850 hPa pseudo-equivalent potential temperature distributions of FY-3D / VASS and ERA5 is conducted. Figure 4It can be seen that during the onset of the South China Sea summer monsoon in 2022, from April to June, the satellite-retrieved pseudo-equivalent potential temperature was slightly lower by 1-2 K. Before the onset of the South China Sea summer monsoon in April, the pseudo-equivalent potential temperature in the lower monsoon region of the South China Sea was below 340 K. In May, the pseudo-equivalent potential temperature was above 340 K, controlling the South China Sea summer monsoon region and the Bay of Bengal. In June, it further pushed northward to areas such as Jiangnan and South China. The distribution and seasonal progression of the pseudo-equivalent potential temperature in FY-3D / VASS and ERA5 are consistent, and to a certain extent, they can monitor the changes in atmospheric temperature and humidity indices during the onset of the South China Sea summer monsoon.

[0059] The steps for assessing the sea surface winds during the FY-3E summer monsoon monitoring in the South China Sea are as follows:

[0060] The FY-3E wind field measurement radar is the first active remote sensing instrument mounted on the Fengyun series meteorological satellites. Its retrieved ocean wind fields have been a stable operational product since March 1, 2022. To analyze its applicability in monitoring the South China Sea summer monsoon, this data was compared with the ocean wind fields retrieved by ASCAT on the EUMETSAT satellite mounted on Metop-C. The time period was selected from April 1 to June 30, 2022, covering the entire process of the 2022 South China Sea summer monsoon outbreak. Due to the different transit times of the two satellites, which swept across the South China Sea summer monsoon region at approximately dawn / evening (FY-3E, around 22:00 and 10:00) and morning / night (Metop-C, around 02:00 and 14:00), both were processed into daily average data for evaluation. Spatial grid matching was performed on the same daily average data within the South China Sea summer monsoon region.

[0061] In monitoring the South China Sea summer monsoon, attention is paid not only to wind speed magnitude but also to the meridional wind (v) and zonal wind (u) components, as these three quantities have been tested and evaluated separately. The monthly matched sample size was approximately 20,000 from April to June 2022. The zonal wind (u) assessment shows ( Figure 5 According to the above assessment formula, the correlation coefficients for April and May are 0.66 and 0.62 respectively, while the correlation coefficient for June is relatively low at 0.52. The high-density scattered area in April is distributed between 0-5 m / s, indicating that the South China Sea summer monsoon is dominated by easterly winds. The high-density scattered area in May is distributed between -5 and 5 m / s, while in June it shifts to between -5 and 0 m / s, representing the shift in zonal winds before and after the onset of the South China Sea summer monsoon. The average deviation of zonal winds from April to June 2022 was approximately -0.58 m / s, with an average absolute error of approximately 2.29 m / s, a root mean square error of approximately 3.01 m / s, and an average correlation coefficient of 0.70. The meridional wind (v) assessment shows ( Figure 6The correlation coefficients for April to June were all above 0.75, with an average correlation coefficient of 0.85. The average deviations were all positive, indicating that the southerly wind component was slightly stronger than the MetOp-C / ASCAT component, with the largest average deviation in June. The absolute average deviation and root mean square error of the meridional wind (v) were both smaller than those of the zonal wind (u), and the differences before and after the onset of the summer monsoon were small. The average deviation for April to June was 0.52 m / s, the average absolute error was 2.01 m / s, and the average root mean square error was 2.70 m / s. Wind speed assessment showed ( Figure 7 The correlation coefficient was highest in April at 0.87, and the average correlation coefficient from April to June was 0.79. The average deviation was about -0.46 m / s, the absolute deviation was 1.56 m / s, and the root mean square error was about 2.00 m / s.

[0062] From the average distribution of April to June 2022 ( Figure 8 The ocean wind flow field distributions of FY-3E / WindRAD and MetOp-C / ASCAT are consistent, with similar locations and intensities of high-speed areas. In April, before the onset of the Asian summer monsoon, the South China Sea summer monsoon region is dominated by northeasterly winds, with higher wind speeds in the northeastern South China Sea and east of the Philippines. The wind speed in FY-3E is slightly weaker, by about 1 m / s. At this time, the cross-equatorial airflow along the east coast of Africa has not yet been established, the Arabian Sea is under anticyclone control, and southwesterly winds begin to appear south of India, extending all the way to the southwestern Bay of Bengal. In May, during the successive onset of the Asian summer monsoon, the cross-equatorial airflow over the east coast of Africa is strong, turning into westerly or southwesterly winds within the 0-10N latitude zone, extending to the Indochina Peninsula and the northern South China Sea. The summer monsoon in the Bay of Bengal and the South China Sea intensifies. As can be seen from the distribution of high-speed areas, the wind speed in FY-3E is slightly weaker, by about 1 m / s. In June, the cross-equatorial airflow will further strengthen, with the maximum wind speed in the region of concern occurring in the southwestern Arabian Sea, exceeding 11 m / s. The Asian tropical summer monsoon region will be controlled by westerly and southwesterly winds.

[0063] The daily average pseudo-equivalent potential temperature calculated using FY-3D and ERA5 data shows that the monsoon index of the South China Sea summer monsoon region ( Figure 10 a) The average pseudo-equivalent potential temperature in the ERA5 region was slightly higher than that in FY-3D, and significantly higher from mid-March to mid-April. In late March, the average pseudo-equivalent potential temperature in the ERA5 region exceeded 340K. Starting April 28th, except for May 11th and 12th, the pseudo-equivalent potential temperature in ERA5 was greater than 340K, meeting one of the indicators for the onset of the South China Sea summer monsoon. The average pseudo-equivalent potential temperature in the FY-3D region also began to exceed 340K on April 28th, but fell back below 340K after May 1st, fluctuated on May 8th and 9th, and then stabilized relatively steadily above or near 340K around May 17th.

[0064] The National Climate Center's South China Sea summer monsoon monitoring index is the regional average 850 hPa zonal wind u (10-20N; 110-120E). Figure 10 b represents the regional average zonal wind time series from March 1st to September 30th, 2022 (10-20N; 110-120E). It can be seen that the trends of the ocean wind extraction indicators from FY-3E / WindRAD and MetOp-C / ASCAT are basically consistent, with the onset time of the South China Sea summer monsoon being one day later than ERA5 (May 10th). This provides excellent monitoring of the zonal wind direction shift during the onset of the 2022 South China Sea summer monsoon.

[0065] One embodiment also verified the ability of the FY-3 meteorological satellite to detect the evolution of atmospheric parameters before and after the 2022 summer outburst in the South China Sea.

[0066] Monitoring of the East Asian summer monsoon circulation by the National Climate Center indicates that the South China Sea summer monsoon will erupt in the third pentad of May, slightly earlier than the average (fourth pentad of May), and its intensity will be close to or weaker than average (Note: a pentad is defined as 5 days; for example, the third pentad of May is from May 11th to 15th). Monitoring of temperature, humidity, and wind field indicators of the South China Sea summer monsoon by the FY-3 meteorological satellite also shows that the South China Sea summer monsoon will erupt in the third pentad of May 2022. Analysis of atmospheric parameters and the eruption process before and after the onset of the South China Sea summer monsoon using FY-3 data is also available.

[0067] Studies have shown that explosive vortices or cyclonic storms in the Bay of Bengal can trigger the onset of the South China Sea summer monsoon. Before the onset of the 2022 South China Sea summer monsoon, the Bay of Bengal was affected by Cyclone Asani (BAB 03, JTWC 02B, China National Meteorological Center standard translation: Asani). A tropical disturbance formed in the Bay of Bengal on May 5th, was designated a cyclone storm on May 8th, and then gradually moved northwest, making landfall on the coast of Andhra Pradesh, India on May 11th. It then gradually weakened and dissipated, reaching its maximum intensity of a Category 1 tropical cyclone as determined by the JTWC and a severe cyclone storm as determined by the BAB and the China Meteorological Administration. Asani brought strong winds and rain to India and Bangladesh, causing at least three deaths, but failed to significantly alleviate the extreme heat in South Asia.

[0068] Prior to the onset of the South China Sea summer monsoon, tropical cyclone activity also occurred in the southern Indian Ocean. On May 5th, a low-pressure system formed in the central Indian Ocean. This system gradually developed and was named Karim by the Regional Specialized Meteorological Centre (RSMC) on Réunion Island on Saturday, May 7th. Karim moved southeast and entered the Australian region on Sunday, May 8th, further intensifying to Category 2 (95 km / h) at 0600 UTC on May 8th. Karim remained at Category 2 intensity on May 9th as the system steadily moved south. On May 10th, Karim reached a peak intensity of 60 knots (110 km / h), slightly below Category 3. By evening, Karim began to weaken due to unfavorable conditions. Early on May 11th, Karim transitioned into a subtropical system but continued to produce storm and gale-force winds thanks to the strong pressure gradient between the system and the southern high-pressure ridge.

[0069] The combined influence of Tropical Cyclone Karim in the southern Indian Ocean and Cyclone Asani in the northern Indian Ocean intensified the westerly winds over the Indian Ocean between the two cyclones, with wind speeds exceeding 10 m / s in some areas south of the Bay of Bengal, which was conducive to the later advance of the summer monsoon into the South China Sea. The pentad-average FY-3D pseudo-equivalent potential temperature and FY-3E ocean wind distribution before and after the onset of the South China Sea summer monsoon indicate that: in the first pentad of May, cross-equatorial airflow was established over the ocean east of Africa, with westerly winds in the Indian Ocean within the 0-5N range, and southerly winds in the western Bay of Bengal. At this time, the South China Sea was controlled by northeasterly or easterly winds, with stronger winds in the northern part of the South China Sea. A low-pressure circulation existed in the tropical region near 90-100E south of the equator, which was conducive to the strengthening of the westerly winds on its northern side; in the second pentad of May, the most typical feature was the formation of two low-pressure systems over the Bay of Bengal and the southern hemisphere oceans south of it, with the influence on the Bay of Bengal being... Cyclone Asani: Under the influence of Asani, the winds in the South China Sea and the waters south of the Indochina Peninsula shifted from easterly to southeasterly, merging into the cyclone. In the third phase of May, the cyclone made landfall in the Bay of Bengal and dissipated. The most obvious feature was the rise in pseudo-equivalent potential temperature in the Indian Peninsula, the Bay of Bengal, and the Indochina Peninsula. At the same time, the cross-equatorial airflow was more strongly drawn by Asani than in the second phase of May. The southwesterly winds controlled the Bay of Bengal and extended eastward into the South China Sea summer monsoon region. In the fourth phase of May, the southern part of the South China Sea summer region was continuously controlled by the southwesterly winds, while the northern part was affected by cold air and developed northeasterly winds. The pseudo-equivalent potential temperature in most areas was above 340K.

[0070] The Bay of Bengal storm exerted a suction effect on the cross-equatorial airflow, strengthening the westerly winds over the tropical oceans north of the equator. After the cyclone weakened and dissipated, a strong southwest monsoon crossed the Indochina Peninsula and reached the South China Sea, triggering the onset of the South China Sea summer monsoon. Although influenced by cold air, northeasterly winds appeared in the northern part of the South China Sea in the 4th pentad of May, but strong southwesterly winds in the northern Indian Ocean ensured that the entire South China Sea summer monsoon region was controlled by stable southwesterly winds after the cold air passed. In the 5th pentad of May, the pseudo-equivalent potential temperature above 340K, representing a warm and humid air mass, advanced into South China and the Jiangnan region. The entire South China Sea region was influenced by the southwest summer monsoon, with southwesterly and northeasterly winds converging in the waters south of Taiwan. In the 6th pentad of May, the South China Sea continued to be controlled by the southwest summer monsoon, and the warm and humid air mass pushed further north to the Yangtze River basin.

[0071] This invention provides an evaluation of the application of FY-3D / VASS temperature and humidity data and FY-3E / WindRad ocean wind data in specific regions and at specific times. It analyzes the differences between atmospheric parameters retrieved by Fengyun satellites and other data, evaluates the temperature and humidity indicators and wind field indicators of the South China Sea summer monsoon under operational monitoring, and analyzes the onset process of the South China Sea summer monsoon in 2022.

[0072] In the examples, the FY-3D / VASS 850hPa temperature and specific humidity, compared with ERA5, showed an average deviation of -0.6℃, an average absolute deviation of 1.1℃, and a root mean square error of 1.6℃ for the South China Sea summer monsoon region from April to June. The average deviation of specific humidity was -0.53 g / kg, an average absolute error of 2.25 g / kg, and a root mean square error of 2.97 g / kg. The pseudo-equivalent potential temperature calculated using FY-3D / VASS temperature and specific humidity was slightly lower than expected by 1-2 K during the 2022 South China Sea summer monsoon outbreak from April to June. The distribution trend is consistent with the seasonal progression trend, and the atmospheric temperature and humidity index changes during the South China Sea summer monsoon outbreak can be monitored.

[0073] In the examples, the average assessment of the South China Sea summer monsoon region from April to June, comparing the FY-3E / WindRAD ocean winds and the Metop-C / ASCAT ocean winds, shows that the average deviation of zonal winds from April to June 2022 was approximately negative, while the average deviation of meridional winds was positive. Wind speed assessments showed an average correlation coefficient of 0.79, an average deviation of approximately -0.46 m / s, an absolute deviation of 1.56 m / s, and a root mean square error of approximately 2.00 m / s from April to June. The distribution of ocean wind current fields from FY-3E / WindRAD and Metop-C / ASCAT is consistent, with similar locations and intensities of high-wind-speed areas. The horizontal distribution of the average deviation from April to June indicates that the average deviation in the Asian summer monsoon region, including the tropical Indian Ocean south of the equator and the western Northwest Pacific, is generally negative. This is partly due to the systemic deviation caused by the different transit times of the two satellites, leading to diurnal variations in average wind speed.

[0074] The example demonstrates the effectiveness of using FY-3D to calculate pseudo-equivalent potential temperature and FY-3E ocean wind dual-indicator monitoring of the South China Sea summer monsoon. The dual indicators effectively monitor the temperature, humidity, and wind field transformations during the 2022 South China Sea summer monsoon onset process, with accuracy largely consistent with the onset time of the South China Sea summer monsoon published operationally by the National Climate Center, both falling within the third pentad of May. Prior to the onset of the South China Sea summer monsoon, in early May, the tropical cyclone "Karim" in the southern Indian Ocean and the storm "Asani" in the Bay of Bengal in the northern Indian Ocean drew in westerly winds near the equator, strengthening the westerly winds over tropical oceans north of the equator. After the cyclones and storms weakened and dissipated, the strong southwest monsoon crossed the Indochina Peninsula and reached the South China Sea, triggering the onset of the South China Sea summer monsoon.

[0075] This invention utilizes the multi-instrument vertical detection capabilities of the Fengyun polar-orbiting meteorological satellite to monitor the atmospheric temperature and humidity transformation characteristics before and after the onset of the South China Sea summer monsoon. It also uses the wind field measurement radar onboard the FY-3E meteorological satellite to retrieve ocean wind data and assess wind field transformation before and after the onset of the South China Sea summer monsoon. Verification with different data demonstrates the application capabilities of both types of satellite data in South China Sea summer monsoon climate monitoring. Besides real-time monitoring of atmospheric parameter transformations in the South China Sea summer monsoon region, globally covered polar-orbiting meteorological satellites can also monitor cross-equatorial airflow, warm and humid vapor transport, tropical depressions or cyclones in the southern Indian Ocean, and vortices or cyclones erupting in the Bay of Bengal, all of which are important indicators for the establishment of the Asian summer monsoon before its onset, as well as the triggering effect of synoptic-scale systems on the onset of the summer monsoon. This allows for operational monitoring and forecasting of the South China Sea summer monsoon based on Fengyun meteorological satellites, which can be corroborated by meteorological numerical models or reanalysis data.

[0076] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0077] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0078] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0079] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for monitoring the South China Sea summer monsoon based on dual indicators using Fengyun polar-orbiting meteorological satellites, characterized in that, The method includes the following steps: S1. The atmospheric temperature and specific humidity at 850 hPa were obtained by the VASS instrument group of the polar-orbiting meteorological satellite FY-3D, and the data were processed into daily average data to calculate the pseudo equivalent potential temperature index at 850 hPa. S2, uses the WindRAD radar of the polar-orbiting meteorological satellite FY-3E to acquire ocean wind field data, processes it into daily average data, obtains ocean wind speed and direction, and obtains average zonal wind index; S3, assess the accuracy of FY-3D / VASS temperature and specific humidity relative to ERA5 data; S4, Evaluate the accuracy of FY-3E / WindRAD ocean winds relative to Metop-C / ASCAT data; S5 is used to verify the accuracy of monitoring the onset of the South China Sea summer monsoon using the dual indicators S1 and S2, based on the evaluation results of S3 and S4.

2. The method for monitoring the South China Sea summer monsoon based on Fengyun polar-orbiting meteorological satellites according to claim 1, characterized in that, The South China Sea summer monsoon region is (10°N-20°N; 110°E-120°E).

3. The method for monitoring the South China Sea summer monsoon based on Fengyun polar-orbiting meteorological satellites according to claim 1, characterized in that, The daily average data needs to be spatially gridded in the South China Sea summer monsoon region.

4. The method for monitoring the South China Sea summer monsoon based on Fengyun polar-orbiting meteorological satellites according to claim 1, characterized in that, The calculation formulas for the accuracy evaluation indicators mentioned in S3 and S4 are as follows: Where Y is the variable being tested, X is the reference value variable, and n is the matched sample size. Let n be the means of the tested variables in a sample. The average value of the reference variable for testing n samples.

5. The method for monitoring the South China Sea summer monsoon based on Fengyun polar-orbiting meteorological satellites according to claim 1, characterized in that, In the S3 comparison with FY-3D / VASS and ERA5, the pseudo-equivalent potential temperature distribution and seasonal progression trend are consistent, thus the Fengyun polar-orbiting meteorological satellite can monitor the changes in atmospheric temperature and humidity index during the onset of the South China Sea summer monsoon.

6. The method for monitoring the South China Sea summer monsoon based on Fengyun polar-orbiting meteorological satellites according to claim 1, characterized in that, In the S4 comparison, FY-3E / WindRAD and Metop-C / ASCAT show that the ocean surface wind flow field distribution is consistent, and the location and intensity of the high wind speed area are similar. Therefore, the Fengyun polar-orbiting meteorological satellite can monitor the wind field transformation characteristics during the onset of the South China Sea summer monsoon.

7. The method for monitoring the South China Sea summer monsoon based on Fengyun polar-orbiting meteorological satellites according to claim 1, characterized in that, The accuracy of monitoring the onset process of the South China Sea summer monsoon using the S1 and S2 dual indicators was compared and verified with the onset time of the South China Sea summer monsoon published operationally by the National Climate Center.

8. The method for monitoring the South China Sea summer monsoon based on Fengyun polar-orbiting meteorological satellites according to claim 1, characterized in that, When the polar-orbiting meteorological satellite provides global coverage monitoring, the average FY-3D pseudo-equivalent potential temperature and FY-3E ocean wind distribution display are also used to monitor cross-equatorial airflow, warm and humid water vapor transport, tropical depressions or cyclones in the southern Indian Ocean, vortices or cyclones in the Bay of Bengal, and the triggering effect of synoptic-scale systems on the onset of the summer monsoon, which are important indicators for the establishment of the Asian summer monsoon before the outbreak of the South China Sea summer monsoon.

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