A method for identifying complex hot and dry events based on daily drought index

Abstract

This invention discloses a method for identifying complex dry-heat events based on the daily drought index, comprising: obtaining the daily rolling 30-day advance monthly cumulative precipitation (P-value) and daily potential evapotranspiration (PET) values; constructing cumulative water deficit sequences at different time scales to obtain the daily monitored standardized potential evapotranspiration index (SPEI); defining the occurrence of drought events using the consecutive number feature of the daily monitored SPEI; defining the occurrence of extreme high-temperature events using events where the daily maximum temperature exceeds the daily high-temperature threshold for three consecutive days; and considering a complex dry-heat event to have occurred when both drought and extreme high-temperature events occur simultaneously. This invention utilizes the daily SPEI index to monitor and identify complex dry-heat events, and defines the duration and severity of such events, enabling a comprehensive quantitative analysis of the interdecadal, seasonal, and intra-seasonal frequency, duration, and severity characteristics of complex dry-heat events.

Description

Technical Field

[0001] This invention relates to the field of extreme climate identification technology, specifically a method for identifying complex hot and dry events based on the daily drought index. Background Technology

[0002] Global warming has exacerbated the instability of the climate system, leading to complex and concurrent extreme weather events composed of multiple interconnected events. The impact of these complex events is greater than the sum of the effects of any single event. Among these, complex extreme heat and dry events, occurring simultaneously in inland areas, are occurring more frequently. These complex extreme heat and dry events are also more closely related to people's lives and livelihoods, making them a hot topic in extreme climate change research and widely recognized as the most significant complex extreme weather and climate events affected by global climate change.

[0003] Currently, there is no unified monitoring index for complex hot and dry events. Most monitoring indices are based on monthly precipitation or monthly drought indices, while also considering the number of extreme high-temperature events that occur in that month. These indices can only reflect the number of complex hot and dry events, but cannot reflect their duration and intensity, which has led to related studies mainly focusing on interannual frequency variation characteristics.

[0004] The sensitivity of complex dry heat events decreases with increasing time scale, mainly occurring on a time scale of 1 to 3 months within the season. However, the time scale of complex dry heat events driven by high-pressure systems is generally a few days, and existing monitoring methods are difficult to describe their seasonal characteristics.

[0005] On the other hand, for studies of complex dry-heat events in different regions, different monitoring indicators may lead to significant differences in conclusions. Therefore, it is necessary to combine regional drought indices, which have better applicability at the regional scale, to conduct comprehensive monitoring of regional complex dry-heat events and reduce the uncertainty brought about by assessment indicators. Thus, how to accurately capture the temporal and spatial characteristics of the development process of complex dry-heat events is a key issue that urgently needs to be addressed to improve the forecasting and early warning capabilities of complex dry-heat events.

[0006] Patent publication (CN114638526A) discloses a method for quantitatively assessing drought-heat wave combined events. Although the patent publication points out a method for quantitatively assessing drought-heat wave combined events, it only uses image coupling of combined events and does not provide a method for quantifying the severity of combined events.

[0007] Therefore, it is currently impossible to accurately capture the temporal and spatial characteristics of the development process of complex dry and hot events, and it is also impossible to quantitatively identify complex extreme dry and hot events. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for identifying complex dry-heat events based on the daily drought index. This method can identify the start date, end date, duration, and intensity of complex dry-heat events, providing practical technical support for the monitoring of complex dry-heat events.

[0009] This invention is specifically implemented through the following technical solutions:

[0010] A method for identifying complex hot and dry events based on the daily drought index, comprising:

[0011] We obtained the daily rolling 30-day advance monthly cumulative precipitation P and the daily potential evapotranspiration PET value, constructed the cumulative water deficit series at different time scales, and obtained the standardized potential evapotranspiration index SPEI monitored daily.

[0012] The occurrence of drought events is defined by the characteristic that the standardized potential evapotranspiration index (SPEI) is less than -0.5 for several consecutive days based on daily monitoring.

[0013] Using the highest daily temperature T for 3 consecutive days max Exceeding the daily high temperature threshold T d The event is defined as the occurrence of an extreme high-temperature event;

[0014] When drought and extreme heat events occur simultaneously, it is considered a combined dry-heat event.

[0015] In the technical solution of this invention, the Penman-Monteith method recommended by the Food and Agriculture Organization of the United Nations (FAO) is used to calculate the daily potential evapotranspiration (PET) of a site. The calculation formula is as follows:

[0016]

[0017] In the formula: Δ is the slope of the saturated water vapor pressure curve (kPa / ℃), R n Net radiation (MJ / (m 2 ·d)); G is the soil heat flux (MJ / (m²) 2 ·d)), where γ is the wet / dry constant (kPa / ℃), T is the average surface temperature (℃); U is the 2m high wind speed (m / s), converted from the average wind speed at 10m from the meteorological station according to the FAO recommended formula; e a e represents the actual water vapor pressure (kPa). s The average saturated water vapor pressure is (kPa).

[0018] Using the difference between monthly cumulative precipitation (P) and petroleum precipitation (PET) 30 days in advance, P-PET, a cumulative water deficit series at different time scales was constructed:

[0019]

[0020] In the formula: P is precipitation, PET is potential evapotranspiration, k is the monthly time scale (month), and n is the number of calculations.

[0021] The probability distribution of the cumulative water deficit sequence was calculated using a three-parameter log-logistic probability distribution function. The distribution function was then standardized, and the daily SPEI index was obtained by referring to the calculation of the Standardized Potential Evapotranspiration Index (SPEI).

[0022] As a preferred method for defining the drought event described in the invention, the process of the drought event is defined as follows: the SPEI index is lower than -0.5 for 15 consecutive days, wherein the start date of the drought event process is the first day when the SPEI value is less than -0.5, and the end date is the first day after the last day when the SPEI value is less than -0.5.

[0023] In the technical solution of the present invention, the method for defining the end of the drought event process is as follows: when the SPEI index is greater than or equal to -0.5 for 5 consecutive days, the drought event process ends.

[0024] As a preferred method for defining the drought event described in the invention, the severity S of the drought event is... d Expressed as: the sum of the absolute values ​​of the SPEI index on each day during the duration of a drought event:

[0025]

[0026] Wherein, the drought event duration D is the number of days from the start to the end of the drought event process.

[0027] In this invention, the extreme high-temperature event is defined as: the daily maximum temperature T for three consecutive days. max All exceeded the daily high temperature threshold T d It was believed at the time that an extreme heat event had occurred.

[0028] The daily high temperature threshold is the 90th percentile of the daily maximum temperature of the given day and the 15 days before and after the given day in the 31 days of the study period. For example, the 90th percentile of the daily maximum temperature of the given day and the 15 days before and after the given day in the 60 years from 1961 to 2020.

[0029] The severity S of the extreme high temperature event h The definition method is as follows: the cumulative sum of the differences between the daily maximum temperature and the threshold during the duration of an extreme high-temperature event is defined as the severity S of the extreme high-temperature event. h :

[0030]

[0031] The method for defining a complex dry-heat event is as follows: if the SPEI drought index reaches the standard for the start of a drought event on a given day, and at the same time exceeds and reaches the definition standard for an extreme high-temperature event, then a complex dry-heat event is identified.

[0032] The duration D of the complex hot and dry event is defined as the number of consecutive days that meet this standard, and the severity S is defined as the product of the severity of the drought and the extreme heat event at the time of the event.

[0033] S = S d ×S h .

[0034] An optional definition of the severity S of a complex hot and dry event is: when a complex hot and dry event occurs, the severity S of the drought event is... d Standardized value and the severity S of extreme high-temperature events h Product of standardized values:

[0035] S = S d标准化 ×S h标准化 .

[0036] The severity S of the drought event d The standardization method is as follows: within a given historical interval, the severity S of all drought events occurring during a complex hot and dry event is... d Values ​​are mapped to the [0,1] interval and then standardized.

[0037] The severity S of the extreme high temperature event h The standardization method is as follows: within a given historical interval, the severity S of all extreme high-temperature events occurring during a complex dry heat event. h Values ​​are mapped to the [0,1] interval and standardized.

[0038] The technical effects of this invention are as follows:

[0039] 1. Compared with the definition methods of the prior art, the present invention uses the daily SPEI index to realize the monitoring and identification of complex dry and hot events, and defines the duration and severity of complex dry and hot events. It can quantitatively analyze the interdecadal, seasonal, and intra-seasonal frequency, duration, severity and other characteristics of complex dry and hot events, and can provide a scientific basis for the monitoring, forecasting and early warning of complex dry and hot events.

[0040] 2. Compared with existing technologies that use image representation, the advantages of this invention also include: This invention employs a quantitative method to identify complex events, adhering to unified measurement standards and statistical methods, resulting in more systematic, standardized, objective, accurate, and reliable results. Different data for the same quantitative indicator can be directly compared to determine differences and trends, facilitating comparison. Quantitative analysis based on quantitative indicators allows for the induction of patterns, the establishment of theoretical models, and better summarization. Attached Figure Description

[0041] Figure 1 This is a map showing the cumulative precipitation P-values ​​monitored daily for 30 days in advance at the Huaning Station in Yunnan Province from May to October 2010.

[0042] Figure 2 This is a map showing the cumulative potential evapotranspiration PET values ​​monitored daily for 30 days in advance from May to October 2010 at the Huaning Station in Yunnan.

[0043] Figure 3 Standardized potential evapotranspiration index (SPEI) map for daily monitoring at Huaning Station, Yunnan Province, from May to October 2010;

[0044] Figure 4 This is a daily SPEI index map of the period of most severe drought at Huaning Station, Yunnan Province, from August 23, 2010 to September 22, 2010.

[0045] Figure 5 This is a sequence of daily drought index and high temperature events monitored at the Huaning Station in Yunnan Province from May to October 2010. Detailed Implementation

[0046] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the term "comprising" and any variations thereof in the specification, claims and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0048] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0049] The following embodiments use the Huaning Station in Yunnan Province as an example to illustrate the method for identifying complex dry and hot events based on the daily drought index.

[0050] Table 1 shows the cumulative precipitation P-values ​​monitored daily for 30 days in advance at the Huaning Station in Yunnan Province from May to October 2010.

[0051] Table 1. Cumulative precipitation P-values ​​monitored daily for 30 days in advance at Huaning Station, Yunnan Province, from May to October 2010.

[0052]

[0053]

[0054] Figure 1 This is a map showing the cumulative precipitation P-values ​​monitored daily for 30 days in advance at the Huaning Station in Yunnan Province from May to October 2010.

[0055] Table 2 shows the cumulative potential evapotranspiration (PET) values ​​monitored daily for 30 days in advance from May to October 2010 at the Huaning Station in Yunnan.

[0056] Table 2. Cumulative Potential Evapotranspiration (PET) Values ​​Monitored Daily 30 Days Ahead of Schedule at Huaning Station, Yunnan Province, from May to October 2010

[0057]

[0058]

[0059] Figure 2 This is a graph showing the cumulative potential evapotranspiration (PET) values ​​monitored daily for 30 days in advance from May to October 2010 at the Huaning Station in Yunnan.

[0060] The daily potential evapotranspiration (PET) value curve was obtained by using the Penman-Monteith method recommended by the Food and Agriculture Organization of the United Nations (FAO) to calculate the daily potential evapotranspiration (PET) of the site. The calculation formula is as follows:

[0061]

[0062] In the formula: Δ is the slope of the saturated water vapor pressure curve (kPa / ℃), R n Net radiation (MJ / (m 2 ·d)); G is the soil heat flux (MJ / (m²) 2 ·d)), where γ is the wet / dry constant (kPa / ℃), T is the average surface temperature (℃); U is the 2m high wind speed (m / s), converted from the average wind speed at 10m from the meteorological station according to the FAO recommended formula; e a e represents the actual water vapor pressure (kPa). s The average saturated water vapor pressure is (kPa).

[0063] Using the difference between monthly cumulative precipitation (P) and petroleum precipitation (PET) 30 days in advance, P-PET, a cumulative water deficit series at different time scales was constructed:

[0064]

[0065] In the formula: P is precipitation, PET is potential evapotranspiration, k is the monthly time scale (month), and n is the number of calculations.

[0066] Table 3 shows the standardized potential evapotranspiration index (SPEI) values ​​monitored daily at the Huaning station in Yunnan Province from May to October 2010.

[0067] Table 3. Standardized Potential Evapotranspiration Index (SPEI) values ​​monitored daily at Huaning Station, Yunnan Province, from May to October 2010.

[0068]

[0069] like Figure 3 This indicates that by obtaining the daily rolling 30-day advance monthly cumulative precipitation P and daily potential evapotranspiration PET values ​​of the Huaning Station in Yunnan from May to October 2010, a cumulative water deficit series at different time scales was constructed, resulting in the standardized potential evapotranspiration index (SPEI) curves monitored daily at the Huaning Station in Yunnan from May to October 2010.

[0070] The probability distribution of the cumulative water deficit sequence was calculated using a three-parameter log-logistic probability distribution function. The distribution function was then standardized, and the daily SPEI index was obtained by referring to the calculation of the Standardized Potential Evapotranspiration Index (SPEI).

[0071] The occurrence of drought events was defined by using the standardized potential evapotranspiration index (SPEI) monitored daily for several consecutive days with a multiple timescale characteristic of SPEI < -0.5.

[0072] Specifically, the drought event process is defined as follows: the SPEI index is below -0.5 for 15 consecutive days. The drought event begins on the first day when the SPEI value is less than -0.5, and ends on the day following the last day when the SPEI value is less than -0.5. The drought event ends when the SPEI index is greater than or equal to -0.5 for 5 consecutive days.

[0073] As shown in Table 3, Figure 3 The SPEI index was recorded at Huaning Station in Yunnan Province from May to October 2010. Figure 4 Table 4 records the daily SPEI index of the Yunnan Huaning Station during the period of most severe drought from August 23, 2010 to September 22, 2010.

[0074] Table 4. SPEI Index Statistics from August 23, 2010 to September 22, 2010

[0075] date SPEI value date SPEI value date SPEI value August 23 -1.87 September 3 -2.11 September 13 -2.04 August 24 -1.94 September 4 -2.13 September 14 -2.09 August 25 -1.95 September 5 -2.05 September 15 -2.09 August 26 -1.98 September 6 -2.07 September 16 -2.09 August 27 -2.03 September 7 -2.05 September 17 -2.07 August 28 -2.03 September 8 -2.05 September 18 -2.16 August 29 -2.03 September 9 -2.08 September 19 -2.22 August 30 -2.05 September 10 -2.09 September 20 -2.26 August 31 -2.03 September 11 -1.96 September 21 -2.12 September 1 -2.05 September 12 -1.99 September 22 -2.02 September 2 -2.08

[0076] Through Table 3, Figure 3 It can be seen that during the period from May to October 2010, the SPEI was less than -0.5 for 157 consecutive days, and there was one drought event. That is, during this period, the SPEI index was less than or equal to -0.5 for more than 15 consecutive days, and the SPEI index was greater than or equal to -0.5 for more than 5 consecutive days from October 9 to October 22. Therefore, it can be identified that a drought event occurred from May to October, and the drought event lasted from May 5 to October 8, and ended on October 9.

[0077] The severity S of the drought event d Expressed as: the sum of the absolute values ​​of the SPEI index on each day during the duration of a drought event:

[0078]

[0079] The duration D of the drought event is the number of days from the start to the end of the drought event.

[0080] Table 4 records the daily SPEI index during the period of drought severity, from May 5, 2010 to October 8, 2010, and from August 23, 2010 to September 22, 2010, when the drought was at its most severe. The drought event severity S... d It is 63.8.

[0081] Furthermore, in the implementation process, the definition method for the extreme high temperature event is as follows: the daily maximum temperature T for three consecutive days. max All exceeded the daily high temperature threshold Td An extreme heat event was considered to have occurred, with the daily high-temperature threshold determined by the 90th percentile of the daily maximum temperature over a given date and the 15 days before and after the given date (31 days in total) during the study period (1961-2020). Table 5 records the daily high-temperature threshold T at the Huaning station in Yunnan from August 23, 2010 to September 22, 2010. d Daily maximum temperature T max Specific data.

[0082] Table 5 Daily High Temperature Threshold T from August 23 to September 22 d Daily maximum temperature T max Statistical table

[0083]

[0084] As shown in Table 5, extreme high-temperature events occurred from September 5 to 7, 2010, and from September 17 to 22, 2010.

[0085] The severity S of the extreme high temperature event h The definition method is as follows: the cumulative sum of the differences between the daily maximum temperature and the threshold during the duration of an extreme high-temperature event is defined as the severity S of the extreme high-temperature event. h :

[0086]

[0087] It is evident that the extreme heat event that occurred from September 5th to September 7th, 2010 was of significant severity (S). h The severity of the extreme heat event that occurred from September 17 to September 22, 2010 was rated 7.0 (Score S). h It is 13.7.

[0088] Furthermore, the definition method for a compound dry-heat event is as follows: if the SPEI drought index reaches the standard for the start date of a drought event on a given day, and at the same time exceeds and reaches the definition standard for an extreme high-temperature event, then a compound dry-heat event is identified. Thus, it can be seen that two compound dry-heat events occurred at the Huaning station in Yunnan from August 23, 2010 to September 22, 2010.

[0089] In an optional embodiment, the severity S of a complex hot and dry event is defined as follows: the duration D of the complex hot and dry event is defined as the number of consecutive days that meet this standard, and the severity S is defined as the product of the severity of the drought and extreme heat events at the time of the event.

[0090] S = S d ×S h .

[0091] Accordingly, the severity of the complex dry-heat event occurring from September 5th to September 7th, 2010, is S = 43.22, and the severity of the complex dry-heat event occurring from September 17th to September 22nd, 2010, is S = 175.95. However, in this type of embodiment, there will be problems with large numerical ranges and large dispersion in the calculation. Therefore, in another optional embodiment, when calculating the severity S of the complex dry-heat event, S is... d and S h The data are standardized separately, mapped to the [0,1] interval, and then multiplied. Specifically, the severity S of the drought event is... d The standardization method is as follows: For the 60 years from 1961 to 2020, the severity S of all drought events during the occurrence of complex hot and dry events is calculated. d The values ​​are mapped to the [0,1] interval and standardized; the severity S of the extreme high-temperature event h The standardization method is as follows: For the 60 years from 1961 to 2020, the severity S of all extreme high-temperature events during the occurrence of complex dry-heat events is calculated. h Values ​​are mapped to the [0,1] interval and standardized.

[0092] Accordingly, the severity of the complex dry heat event that occurred from September 5 to September 7, 2010 was S = 10.13 (expanded by 100 times), and the severity of the complex dry heat event that occurred from September 17 to September 22, 2010 was S = 54.35 (expanded by 100 times).

[0093] According to the method of the above embodiments, Table 6 also lists the statistics of the complex dry heat event at the Huaning Station in Yunnan from May to October 2010.

[0094] Taking Huaning Station in Yunnan Province as an example, the station experienced continuous drought from May to October 2010, during which varying degrees of high-temperature events occurred, further exacerbating the drought (e.g., Figure 5 Statistical analysis revealed 13 complex dry-heat events during this period, totaling 50 days. The main dates are shown in Table 6. The longest consecutive periods occurred from July 2nd to July 7th and from September 17th to September 22nd, both lasting 6 days. However, the severity of the two events differed significantly. The drought and high-temperature events from July 2nd to July 7th were less severe than those from September 17th to September 22nd, with a combined dry-heat event severity score of 9.46. From September 17th to September 22nd, as the drought continued to develop, the drought severity score increased to 0.59, while the high-temperature event severity score was stronger at 0.93, resulting in a combined dry-heat event severity score of 54.35.

[0095] Table 6. Statistics on Complex Dry Heat Events at Huaning Station, Yunnan Province, from May to October 2010

[0096]

[0097] The method for identifying complex dry-heat events based on the daily drought index described in the above specific implementation method uses the daily SPEI index to monitor and identify complex dry-heat events, and defines the duration and severity of complex dry-heat events. It can quantitatively analyze the interdecadal, seasonal, and intraseasonal frequency, duration, and severity characteristics of complex dry-heat events, and can provide a scientific basis for the monitoring, forecasting, and early warning of complex dry-heat events.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for identifying complex hot and dry events based on daily drought index, characterized in that, include: The daily rolling 30-day advance monthly cumulative precipitation P value and daily potential evapotranspiration PET value are obtained to construct the cumulative water deficit series at different time scales, and the daily monitored standardized potential evapotranspiration index SPEI is obtained. Specifically, the probability distribution of the cumulative water deficit series is calculated using a three-parameter log-logistic probability distribution function, and the probability distribution function is standardized. Referring to the calculation of the standardized potential evapotranspiration index, the daily monitored SPEI index is obtained. Drought events are defined by the characteristic that the standardized potential evapotranspiration index (SPEI) is less than -0.5 for several consecutive days based on daily monitoring; where S... d This indicates the severity of the drought event, specifically the sum of the absolute values ​​of the SPEI index for each day during the duration of the drought event. Wherein, the duration of the drought event, D, is the number of days from the start to the end of the drought event; Using the highest daily temperature T for 3 consecutive days max Exceeding the daily high temperature threshold T d The event is defined as the occurrence of an extreme high-temperature event; where S is used. h The severity of an extreme heat event is indicated by the cumulative sum of the differences between the daily maximum temperature and the threshold during the duration of the extreme heat event, S. h : When drought and extreme heat events occur simultaneously, a combined dry-heat event is considered to have occurred. The duration D of a combined dry-heat event is defined as the number of consecutive days that meet this standard, and the severity S is defined as the severity Sdry of the drought event at the time of the event. d Severity of extreme heat events h The accumulation of: S=S d ×S h ; The duration D of a complex hot and dry event is defined as the number of consecutive days that meet this standard, and the severity S is defined as: the severity S of the drought event when the complex hot and dry event occurs. d Standardized value and the severity S of extreme high-temperature events h Product of standardized values: S=S d标准化 ×S h标准化 , The severity S of the drought event d The standardization method is as follows: within a given historical interval, the severity S of all drought events occurring during a complex hot and dry event is... d Values ​​are mapped to the [0,1] interval and then standardized. The severity S of the extreme high temperature event h The standardization method is as follows: within a given historical interval, the severity S of all extreme high-temperature events occurring during a complex dry heat event. h Values ​​are mapped to the [0,1] interval and standardized.

2. The method for identifying complex hot and dry events based on daily drought index as described in claim 1, characterized in that, The process of defining a drought event is as follows: the SPEI index is below -0.5 for 15 consecutive days. The drought event process begins on the first day when the SPEI value is less than -0.5, and ends on the first day after the last day when the SPEI value is less than -0.

5.

3. The method for identifying complex hot and dry events based on daily drought index as described in claim 2, characterized in that, The drought event process is defined as ending when the SPEI index is greater than or equal to -0.5 for 5 consecutive days.

4. The method for identifying complex hot and dry events based on daily drought index as described in claim 1, characterized in that, The definition of an extreme high-temperature event is as follows: the daily maximum temperature T for three consecutive days. max All exceeded the daily high temperature threshold T d It was believed that an extreme heat event had occurred, in which the daily high temperature threshold T was... d It is the 90th percentile of the daily maximum temperature for a given date and the 15 days before and after it, totaling 31 days.

5. The method for identifying complex hot and dry events based on daily drought index as described in claim 1, characterized in that, The definition of a complex dry-heat event is as follows: if the SPEI drought index reaches the standard for the start of a drought event on a given day, and at the same time exceeds and reaches the definition standard for an extreme high-temperature event, then a complex dry-heat event is identified.

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