A method for separating precipitation within a tropical cyclone circulation

Abstract

The application discloses a method for separating precipitation in a tropical cyclone circulation, and the steps for separating the precipitation in the tropical cyclone circulation in a certain period of time include: obtaining data; determining the circulation range by using the outermost closed isobar average radius (ROCI); identifying the precipitation area by using a threshold T, marking the possible tropical cyclone precipitation area if any part of the area is in the circulation range; if the possible tropical cyclone precipitation area exceeds the range of 2.5 times ROCI, then T=T+1, and repeating until the range is not more than the limited range; deleting the area that does not meet the condition; adding weak precipitation below the threshold T; restoring the original precipitation data in the area, and adding weak precipitation in the un-identified area in the circulation; the application uses the circulation range of the tropical cyclone as a limiting condition to separate the tropical cyclone precipitation, and is more physically meaningful; the separated precipitation is highly consistent with the subjective separation result, and can provide strong support for the analysis and research of the tropical cyclone precipitation.

Description

Technical Field

[0001] This invention relates to the field of meteorological research technology, specifically to a method for separating precipitation within a tropical cyclone circulation. Background Technology

[0002] Tropical cyclones are low-pressure vortices that occur over tropical or subtropical oceans. The strong winds, torrential rains, storm surges, and other secondary disasters they bring often cause significant casualties and property damage. Precipitation is one of the most significant disaster-causing factors of tropical cyclones; heavy rainfall frequently leads to farmland flooding, urban waterlogging, traffic disruptions, and even triggers secondary geological disasters such as landslides and mudslides. On the other hand, tropical cyclone precipitation also has a beneficial aspect, being crucial for agriculture and water resource supply. Quantitative precipitation forecasting for tropical cyclones is vital for ensuring the safety of life and property and the effective use of water resources. Improving forecast accuracy requires a clear understanding of the distribution characteristics of tropical cyclone precipitation and its related factors.

[0003] Previous studies have mostly analyzed precipitation within a fixed radius of the tropical cyclone center. However, tropical cyclones vary in size, and using a fixed radius inevitably includes some non-tropical cyclone precipitation and misses some tropical cyclone precipitation. Besides the fixed radius separation method, other separation methods exist, but they all have problems, such as identifying excessively large precipitation areas, failing to identify any precipitation in weaker tropical cyclones, using unrealistic time extrapolation schemes, and exhibiting drastic fluctuations in precipitation radius. Therefore, it is necessary to adopt a more reasonable method to separate tropical cyclone precipitation. Summary of the Invention

[0004] The purpose of this invention is to provide a method for separating precipitation within a tropical cyclone circulation. This invention uses the range of the tropical cyclone circulation as a limiting condition to separate tropical cyclone precipitation, which is more physically meaningful. Through practical implementation, it can be found that the precipitation separated by this invention is highly consistent with the subjective separation results. It does not have problems such as the identified precipitation area being too large, the inability to identify any precipitation in weak tropical cyclones, or the drastic fluctuations in precipitation radius. It can provide strong support for the analysis and research of tropical cyclone precipitation.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for separating precipitation within a tropical cyclone circulation. First, tropical cyclone data for the specified period is acquired, including the tropical cyclone positions at the beginning and end of the period, the mean radius of the outermost closed isobar (ROCI), and the gridded cumulative precipitation data for the specified period. Then, the average tropical cyclone position and average ROCI for the specified period are calculated.

[0006] Preferably, S1: Tropical cyclone location and ROCI data can be obtained from the optimal tropical cyclone track data IBTrACS, and gridded precipitation data can be obtained from the Global Precipitation Observation Program. S2: A circle is drawn with the mean tropical cyclone location as the center and the mean ROCI as the radius, and the area inside the circle is the tropical cyclone circulation range.

[0007] Preferably, S3: Set the initial threshold T0 for identifying precipitation. T0 should not be too small or too large. T0 can be set to 1 mm, and the precipitation area identification threshold T = T0.

[0008] Preferably, S4: Identify all precipitation areas in the precipitation field using a threshold T, and mark any precipitation area as a possible tropical cyclone precipitation area if any part of the precipitation area is within the tropical cyclone circulation.

[0009] Preferably, S5: Tropical cyclone precipitation may connect with precipitation generated by other systems to form a very large precipitation area. Therefore, if the possible tropical cyclone precipitation area exceeds 2.5 times the ROCI range, then T = T + 1, and repeat the steps in S4 above until the possible tropical cyclone precipitation area does not exceed the limit range.

[0010] Preferably, S6: Traverse all possible tropical cyclone precipitation areas, delete precipitation areas whose weighted center of precipitation is outside the tropical cyclone circulation and whose area within the circulation is less than 1 / 20 of the circulation area, retain precipitation areas whose weighted center is outside the circulation but whose large part is within the circulation, and the remaining precipitation areas are tropical cyclone precipitation areas.

[0011] Preferably, S7: If T>T0 at this time, then use the regional growth method to add weak precipitation between T0 and T to all tropical cyclone precipitation areas.

[0012] Preferably, S8: The growth threshold is t. Initially, let t = T. For each precipitation area ri, if the precipitation of its adjacent grid points is between t-1 mm and t mm, then the grid point is included in ri. In this way, each area grows in different directions at the speed of one grid point. Repeat this step until all precipitation grid points greater than or equal to t-1 mm belong to a certain precipitation area. Let t = t-1, and repeat the above steps until t = 2.

[0013] Preferably, S9: restore the original precipitation data within the tropical cyclone precipitation area and add the precipitation between T0 and T within the circulation range. The precipitation obtained at this time is the precipitation within the tropical cyclone circulation.

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

[0015] First, this invention uses the tropical cyclone circulation range as a constraint to separate tropical cyclone precipitation, which is more physically meaningful. Practical implementation shows that the precipitation separated by this invention is highly consistent with subjective separation results, and it avoids problems such as excessively large identified precipitation areas, failure to identify any precipitation in weaker tropical cyclones, and drastic fluctuations in precipitation radius. Therefore, it can provide strong support for the analysis and research of tropical cyclone precipitation. Attached Figure Description

[0016] Figure 1 This invention provides a flowchart of a method for separating precipitation within a tropical cyclone circulation. Detailed Implementation

[0017] 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, and 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.

[0018] Please see Figure 1This invention provides a technical solution: a method for separating precipitation within a tropical cyclone circulation. First, tropical cyclone data for the specified period is acquired, including the tropical cyclone positions at the start and end of the period, the mean radius of the outermost closed isobar (ROCI), and gridded cumulative precipitation data for the period. Then, the average tropical cyclone position and average ROCI for the period are calculated. Specifically, the method includes the following steps: S1: Cyclone position and ROCI data can be obtained from the best tropical cyclone track data IBTRAS (International Best Track Archive for Climate Stewardship), and gridded precipitation data can be obtained from the Global Precipitation Observation Program (GEP). Measurement (GPM) is used to determine the precipitation area. S2: Draw a circle with the mean tropical cyclone location as the center and the mean ROCI as the radius; the area inside the circle represents the tropical cyclone circulation range. S3: Set the initial threshold T0 for precipitation identification. T0 should not be too small or too large; it can be set to 1 mm. The precipitation area identification threshold T = T0. S4: Use the threshold T to identify all precipitation areas in the precipitation field. If any part of a precipitation area is within the tropical cyclone circulation range, that precipitation area is marked as a possible tropical cyclone precipitation area. S5: Tropical cyclone precipitation may connect with precipitation from other systems, resulting in a very large precipitation area. Therefore, if a possible tropical cyclone precipitation area exceeds 2.5 times the ROCI range, the area should be identified. If T = T + 1, repeat steps S4 until the possible tropical cyclone precipitation areas do not exceed the limit. S6: Traverse all possible tropical cyclone precipitation areas, delete precipitation areas whose weighted center of gravity is outside the tropical cyclone circulation and whose area within the circulation is less than 1 / 20 of the circulation area, retain precipitation areas whose weighted center of gravity is outside the circulation but whose area is largely within the circulation, the remaining precipitation areas are tropical cyclone precipitation areas. S7: If T > T0 at this time, use the region growth method to add weak precipitation between T0 and T to all tropical cyclone precipitation areas. S8: The growth threshold is t, initially let t = T, for each precipitation area ri, if the precipitation of its adjacent grid points is between t-1 mm and t If the precipitation is between t-1 mm, then the grid point is included in ri. In this way, each region grows at the rate of one grid point in different directions. Repeat this step until all precipitation grid points greater than or equal to t-1 mm belong to a certain precipitation region. Let t = t-1, and repeat the above step S8 until t = 2. S9: Restore the original precipitation data in the tropical cyclone precipitation region and add the precipitation between T0 and T in the circulation range. The precipitation obtained at this time is the precipitation in the tropical cyclone circulation.

[0019] This invention uses the range of tropical cyclone circulation as a constraint to separate tropical cyclone precipitation, which is more physically meaningful. Through actual implementation, it can be found that the precipitation separated by this invention is highly consistent with the subjective separation results. It does not have problems such as the identified precipitation area being too large, the inability to identify any precipitation in weak tropical cyclones, or the precipitation radius fluctuating drastically. It can provide strong support for the analysis and research of tropical cyclone precipitation.

[0020] Working principle: First, tropical cyclone data for the specified time period is acquired, including the tropical cyclone positions at the start and end of the period, the mean radius of the outermost closed isobar (ROCI), and the gridded cumulative precipitation data for the period. Then, the average tropical cyclone position and average ROCI for the period are calculated. Specifically, the following steps are included: S1: Cyclone position and ROCI data can be obtained from the best track data of tropical cyclones (IBTrACS, International Best Track Archive for Climate Stewardship), and gridded precipitation data can be obtained from the Global Precipitation Observation Program (Global Precipitation Observation Program). Measurement (GPM) is obtained. S2: Draw a circle with the average tropical cyclone position as the center and the average ROCI as the radius. The area inside the circle is the tropical cyclone circulation range. S3: Set the initial threshold T0 for identifying precipitation. T0 should not be too small or too large. T0 can be set to 1 mm. The precipitation area identification threshold T = T0. S4: Use the threshold T to identify all precipitation areas in the precipitation field. If any part of the precipitation area is within the tropical cyclone circulation range, the precipitation area is marked as a possible tropical cyclone precipitation area. S5: Tropical cyclone precipitation may connect with precipitation generated by other systems to form a very large precipitation area. Therefore, if the possible tropical cyclone precipitation area exceeds 2.5 times the ROCI range, then T = T + 1. Repeat the steps in S4 above until the possible tropical cyclone precipitation area does not exceed the limit range. S6: Traverse all possible tropical cyclone precipitation areas and delete those with precipitation weighting centers in the tropical cyclone circulation. Outside the circulation and within the circulation area, the precipitation area is less than 1 / 20 of the circulation area. Precipitation areas with a center outside the circulation but a large part within the circulation are retained. The remaining precipitation areas are tropical cyclone precipitation areas. S7: If T>T0 at this time, weak precipitation between T0 and T is added to all tropical cyclone precipitation areas using the region growth method. S8: The growth threshold is t. Initially, let t=T. For each precipitation area ri, if the precipitation of its adjacent grid points is between t-1mm and tmm, then the grid point is included in ri. In this way, each region grows at the speed of one grid point in different directions. Repeat this step until all precipitation grid points greater than or equal to t-1mm belong to a certain precipitation area. Let t=t-1 and repeat the above step S8 until t=2. S9: Restore the original precipitation data in the tropical cyclone precipitation area and add precipitation between T0 and T within the circulation range. The precipitation obtained at this time is the precipitation within the tropical cyclone circulation.

[0021] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for separating precipitation within a tropical cyclone circulation, characterized in that, include: S1: First, obtain tropical cyclone data for this period, including the tropical cyclone positions at the beginning and end of the period, the mean radius of the outermost closed isobar (ROCI), and the gridded cumulative precipitation data for this period. Then, calculate the average tropical cyclone position and average ROCI for this period. S2: Draw a circle with the mean tropical cyclone location as the center and the mean ROCI as the radius. The area inside the circle is the tropical cyclone circulation range. S3: Set the initial threshold T0 for identifying precipitation, and the precipitation area identification threshold T = T0; S4: Identify all precipitation areas in the precipitation field using a threshold T. If any part of a precipitation area is within the tropical cyclone circulation, that precipitation area is marked as a possible tropical cyclone precipitation area. S5: If the possible tropical cyclone precipitation area exceeds 2.5 times the ROCI range, then T=T+1, and repeat the steps in S4 above until the possible tropical cyclone precipitation area does not exceed the limit range. S6: Traverse all possible tropical cyclone precipitation areas, delete precipitation areas whose weighting center is outside the tropical cyclone circulation and whose area within the circulation is less than 1 / 20 of the circulation area, retain precipitation areas whose weighting center is outside the circulation but whose area is largely within the circulation, and the remaining precipitation areas are tropical cyclone precipitation areas. S7: If T > T0 at this time, then use the regional growth method to add weak precipitation between T0 and T to all tropical cyclone precipitation areas; S8: The growth threshold is t. Initially, let t=T. For each precipitation region ri, if the precipitation of its adjacent grid points is between t-1 mm and t mm, then the grid point is included in ri. In this way, each region grows in different directions at the speed of one grid point. Repeat this step until all precipitation grid points greater than or equal to t-1 mm belong to a certain precipitation region. Let t=t-1 and repeat the above steps until t=T0. S9: Restore the original precipitation data within the tropical cyclone precipitation area and add the precipitation between T0 and T within the circulation range. The precipitation obtained at this time is the precipitation within the tropical cyclone circulation.

2. The method for separating precipitation within a tropical cyclone circulation according to claim 1, characterized in that: The location of tropical cyclones and ROCI data in S1 can be obtained from the optimal tropical cyclone track data IBTrACS, and the gridded precipitation data can be obtained from the Global Precipitation Observation Project.

3. The method for separating precipitation within a tropical cyclone circulation according to claim 1, characterized in that: Set T0 to 1mm.

Images