CN113156540A

CN113156540A - Method for extracting quasi-bi-periodic oscillation real-time index of high latitude in Eurasia in summer

Info

Publication number: CN113156540A
Application number: CN202011598979.9A
Authority: CN
Inventors: 姚素香; 孙添乐; 夏依聪
Original assignee: Nanjing University of Information Science and Technology
Current assignee: Nanjing University of Information Science and Technology
Priority date: 2020-12-29
Filing date: 2020-12-29
Publication date: 2021-07-23
Anticipated expiration: 2040-12-29
Also published as: CN113156540B

Abstract

The invention discloses a method for extracting quasi-bi-periodic oscillation (QBBWO) real-time indexes of high latitude and middle latitude in Eurasia, which comprises the steps of firstly carrying out EEOF analysis on 500hPa potential height fields subjected to band-pass filtering for 10-30 days with lagged days of-6, -3 and 0 at the high latitude in summer 5-9 in 1979-2018 to obtain the first 4 modes; secondly, extracting a 500hPa potential height distance flat field for 10-30 days by adopting a non-filtering method; projecting a non-filtered 500hPa potential height distance flat field containing-6, 3 and 0 days to the first two EEOF modes to obtain a western-transmitted quasi-bi-periodic oscillation real-time index of high latitude in Eurasia; then, the height distance flat field of the 500hPa potential for 10-30 days including-6, -3 and 0 days of non-filtering is projected to the third and fourth EEOF modes to obtain a quasi-bi-periodic oscillation real-time index of high latitude in the second Eurasia. The invention grasps the key area of the QBBWO with medium and high latitude and the circulation structure and the propagation characteristics thereof, embodies the relation between the QBBWO with medium and high latitude and the weather and the climate in China and east Asia areas, is applied to real-time monitoring and provides reference for the evaluation of the QBBWO simulation capability.

Description

Method for extracting quasi-bi-periodic oscillation real-time index of high latitude in Eurasia in summer

Technical Field

The invention relates to an index extraction method, in particular to an extraction method of quasi-bi-periodic oscillation real-time indexes of high latitude and middle latitude in Eurasia in summer.

Background

Quasi-bi-cyclic oscillations (QBBWO), also known by scholars as Sub-monthly oscillations (Yokoi and Satomora, 2006; Wen et al, 2011), are important phenomena with time scales smaller than seasonal changes, and numerous studies have shown that QBBWO is ubiquitous in regions of the monsoon or tropical regions (Lau et al, 1988; Chen and Chen,1995 a; Fukutomi and Yasunari,1999, Krishramuriti and Bhalme, 1976; Krishramurit and Ardauny, 1980), regions of high and high latitude (Wushu et al, 1994; plum Chongyin and Arduch, 1995), and even globally (Kikuchi and Wang, 2009).

The current domestic research on QBBWO real-time index is mainly focused on the research on signals from medium and low latitudes: lee et al (2013) proposes a real-time index for northern hemisphere summer season internal oscillation (BSISO), which uses external long wave radiation (OLR) of east asian summer season wind zone (40 ° -160 ° E,10 ° S-40 ° N) and low-layer wind field distance flat field to perform multivariate empirical orthogonal analysis (EOF), and the third and fourth modes mainly represent QBWO signals of 10-30 days propagating to north/northwest, i.e., BSISO2 index. Gao et al (2016) developed a real-time index of the Atlantic-North-West Pacific region (90 ° -150 ° E,10 ° S-40 ° N) based on Lee et al (2013), and its three and four modalities also represent QBBWO signals for 10-30 days, i.e., EAWNP-ISO2 indices. As the establishment of the two methods is based on an EOF analysis method, the monitoring capability of extreme weather is still to be improved, Hsu et al (2019) provides new real-time QBBWO indexes WNP-QBBWOI and IO-QBBWOI by utilizing an Extended EOF (EEOF) method.

Considering that the EEOF method includes the spatial-temporal evolution characteristics of the meteorological field, the fluctuation propagation characteristics are better grasped, and the continuous changes of the meteorological field at different moments can be considered as a whole, so that the EEOF method can be used as a low-pass filter to filter out small-scale fluctuations (Weare and Nasstrom 1982; Kikuchi and Wang 2009; Kikuchi et al 2012; Suhas et al 2014; Kikuchi et al 2017).

Many researches show that the west wind zone at the middle and high latitude has a remarkable period of 10-30 days, the oscillation intensity is stronger, the quasi-bi-periodic oscillation at the middle and high latitude has remarkable influence on the weather and extreme weather events in China, and the establishment of the quasi-bi-periodic oscillation real-time index at the middle and high latitude has important scientific significance and application value. However, there is currently a lack of medium and high latitude quasi-bi-periodic oscillation real-time index correlation studies.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a method for extracting a quasi-bi-periodic oscillation real-time index of high latitude and summer in Eurasia.

The technical scheme is as follows: the invention relates to a method for extracting a quasi-bi-periodic oscillation real-time index in summer of high latitude in Eurasia, which comprises the following steps of:

s1: EEOF analysis is carried out on 500hPa potential height fields subjected to band-pass filtering for 10-30 days at high latitudes (0 DEG E160 DEG E,30 DEG 75 DEG N) in summer 5-9 in 1979-2018 and lagging for-6, -3 and 0 days;

s2: extracting 500hPa potential height distance flat field for 10-30 days by adopting a non-filtering method;

s3: projecting a non-filtered 500hPa potential height distance flat field containing-6, -3 and 0 days to the first two EEOF modes to obtain a western-transmitted quasi-two-cycle oscillation real-time index at high latitude in Eurasia;

s4: and projecting the non-filtered 500hPa potential height distance flat field containing-6, -3 and 0 days to a third EEOF mode and a fourth EEOF mode to obtain a quasi-bi-periodic oscillation real-time index of high latitude in the second Eurasia.

Wherein, in the process of extracting 500hPa potential height distance flat field for 10-30 days by adopting the non-band-pass filtering method, the method also comprises the following steps:

s1: subtracting the sliding average of the previous 15 days from the original data, and removing a background signal;

s2: the sliding average was performed for the first 4 days, and the high frequency signal was removed.

In the invention, the Butterworth method is utilized for 10-30 days of band-pass filtering; the index is derived from the ERA-Interim reanalysis data. The middle and high latitude areas comprise upstream and downstream areas of the west wind zone and middle and high latitude areas influencing large weather in China.

Has the advantages that: compared with the prior art, the invention has the following remarkable advantages: (1) the key area of the QBBWO and the circulation structure and the propagation characteristics thereof can be mastered; (2) the relation between the QBBWO with medium and high latitude and weather and climate systems in China or east Asia regions can be well reflected, such as the indication effect on plum blossom in Jianghuai, the regulation and control on the time-space evolution of wind precipitation in east Asia, the monitoring on extreme precipitation and high temperature events and the like; (3) the method can be directly applied to real-time monitoring on business and provides reference for evaluation of the simulation capability of the mode QBBWO.

Drawings

FIG. 1 is a flow chart of the non-filtering real-time index creation of the present invention;

FIG. 2 shows EEOF1(a-c) and EEOF2(d-f) with high altitude 500hPa potential height intervals of3 days (-6 days, -3 days and 0 days) in summer Eurasia of the northern hemisphere (percentages on subheadings are variance contribution rates of each mode);

FIG. 3 shows EEOF3(a-c) and EEOF4(d-f) with high altitude 500hPa potential height intervals of3 days (-6 days, -3 days and 0 days) in summer Eurasia of the northern hemisphere (percentages on subheadings are variance contribution rates of each mode);

FIG. 4 is a graph of the lead-lag correlation coefficient between EEOF decomposition time coefficients of the present invention (where the abscissa represents the number of days of lead-lag);

FIG. 5 is a graph of real-time indices (solid line) at 5-9 months in 2010 and the resulting time coefficients (dashed line) of the EEOF analysis, a being EASO-W1 and PC1, b being EASO-W2 and PC2, c being EASO-E1 and PC3, d being EASO-E2 and PC 4;

FIG. 6 is a phase composition curve of real-time index EASO-W (a) in West and EASO-E (b) in east. Here, QBWO strong events with each phase intensity exceeding 1 and their evolution 40 days later are synthesized, with large filled circles representing the starting point, odd phases (1, 3, 5, 7) represented by a solid line, and even phases (2, 4, 6, 8) represented by a dashed line;

FIG. 7 is a composite graph of a 10-30 day band pass filtered 500hPa potential altitude anomaly versus eight phases of West passed potential altitude anomaly EASO-W as defined in FIG. 6 (the shaded area indicates passing 95% of the t-test);

FIG. 8 is a composite graph of a 10-30 day bandpass filter 500hPa potential altitude anomaly versus eight phases of east-handed potential altitude anomaly EASO-W as defined in FIG. 6 (the shaded area indicates passing 95% of the t-test);

FIG. 9 shows the eight-phase distribution of the Western EASO-W (a) and the easO-E (b) at the high latitude according to the 1979-2018 plum-entering date provided by the national center of climate (the middle two circles represent quasi-bi-periodic oscillation intensities of 0.5 and 1.0);

FIG. 10 is a 10-30d filtered composition of eight phases of precipitation levels in the western-style high altitude potential altitude anomaly (EAWO-W) life history (shaded areas represent more than 95% significance tests);

FIG. 11 is a 10-30d filtered composition of eight phases of precipitation levels in the eastern high altitude potential altitude anomaly (EAWO-E) life history (shaded areas represent more than 95% significance test);

FIG. 12 is a composite of eight phases of 10-30d filtered air temperature range plots in the western-style high altitude potential altitude anomaly (EAWO-W) life history (shaded areas represent more than 95% significance tests);

FIG. 13 is a composite of eight phases of 10-30d filtered air temperature steps in the eastern high altitude potential altitude anomaly (EAWO-E) life history (shaded area represents more than 95% significance test);

FIG. 14 is a graph showing the real-time index evolution of the altitude of the high latitude position of 10-30d in Europe during the continuous extreme rainstorm event of the Yangtze river basin from 1/7 to 12/1991, the large solid circle indicates the real-time index of EASO-W in 1991, FIG. 14a is a graph showing the real-time index of EASO-E in FIG. 14 b.

Detailed Description

The technical solution of the present invention is further explained with reference to fig. 1-14.

The method for extracting the quasi-bi-periodic oscillation real-time index of the high latitude summer in Eurasia as shown in the figure comprises the following steps:

s1: EEOF analysis is carried out on 500hPa potential height fields subjected to band-pass filtering for 10-30 days at high latitudes (0 DEG E-160 DEG E, 30-75 DEG N) in summer 5-9 in 1979-2018 and lagging for-6, -3 and 0 days;

the region covers the upstream and downstream regions of the west wind zone with great influence on the weather and climate of China, including key regions of high and medium latitudes of large weather of China, such as the Wularshan region, the Begalhu region, the Yakutke region and the like. The first two modalities of the EEOF analysis explain 11.33% and 11.17% of the overall variance (FIG. 2), the third and fourth modalities of the EEOF analysis account for 6.30% and 5.90% of the overall variance, respectively, and the total contribution of the first 4 variances is about 35% (FIG. 3), indicating convergence, and both pass the North significance test (North et al 1982). Through the finding of the lead-lag correlation (fig. 4), the first and second modes of the EEOF are the same fluctuation signal, the third and fourth modes are also the same fluctuation signal, and the absolute value of the correlation coefficient exceeds 0.8 at most. The evolution process of the first modality and the second modality is represented as follows: the potential altitude quasi-bi-circumferential anomaly exhibits a wave motion in continental europe, with superlongwaves propagating from east to west, wherein the potential altitude anomaly may reach near 40 ° N at the base. The third and fourth modes show two fluctuations in the air on continental europe, with significant east-borne transmission in the air at high latitudes and significant south-borne transmission in the east asian.

In the process of extracting 500hPa potential height distance flat field for 10-30 days by adopting a non-band-pass filtering method, the method also comprises the following steps:

The potential altitude range flat field obtained by the non-band-pass filtering method is called a non-band-pass filtering field. Time correlation coefficients between Principal Components (PC) obtained by 10-30 days of band-pass filtering and real-time indexes of high latitude 10-30d oscillation in Eurasia obtained by projecting to a non-band-pass filtering wave field are calculated, and the four correlation coefficients are respectively 0.81, 0.82, 0.79 and 0.84. For any year, such as 2000, the two are in good agreement as shown in fig. 5. The reliability of the real-time index obtained by this non-bandpass filtering method can thus be determined.

Performing band-pass filtering for 10-30 days by using a Butterworth method; data were from ERA-Interim reanalysis data.

The middle and high latitude areas comprise upstream and downstream areas of the west windy zone and middle and high latitude areas of large weather in China.

According to the quasi-bi-periodic oscillation real-time indexes of high latitude and middle latitude in summer in two Eurasia, the eight phases are respectively divided into eight positions, and the eight positions correspond to positions with different scale potential heights in 10-30 days. The distance of each point from the center is the intensity of the oscillation. Fig. 6 is a composite of the evolution of the phase for strong events with real-time indices exceeding 1.0, which can last 12-13 days for both indices (days outside the circle), demonstrating that this index can provide a relatively long predictable time-out.

FIG. 7 shows the potential height anomaly of 10-30d synthesized according to the real-time oscillation index of West pass. In phase 1, the largest negative anomaly potential height center is located near the new island, while the atlantic and pacific high latitude areas are positive anomaly control (fig. 7 a). When reaching 2-3 phase, the negative potential is highly abnormal and moves to the west, passes through the Barn sea and reaches the northern Europe area. The strength of the positive potential altitude anomaly of the pacific high latitude is obviously enhanced while the altitude anomaly is transmitted west along the Asian continent high latitude area. In phase 4, the new island is controlled by a significant positive anomaly in the eastern asian high latitude area, while the negative anomaly center in northern europe is significantly weakened. The 5 th phase presents the characteristics opposite to the first phase, the new land island is positive potential height anomaly control, and the pacific and atlantic high latitude areas are weak negative anomalies. In the 6 th-7 th phase, the disease is transmitted abnormally in west and reaches the northern Europe through Balen sea. And in the 8 th phase, the negative potential height transmitted by the Pacific ocean and the West moves to the Asian high latitude area abnormally, and the strength is enhanced. The phase obtained based on real-time exponential synthesis clearly reflects the structure and the propagation observation characteristics of western-transmitted quasi-bicylic oscillation with high anomaly of the European subambient potential.

FIG. 8 shows the 10-30d potential height anomaly based on the eastern real-time oscillatory index synthesis. As can be seen from fig. 8, its source is located in the barren sea. In phase 1, there is a significant wave train of the Balancian sea-Ural mountain-Begal lake-east Asia, which is a high anomaly of the positive potential; in the 2 nd-4 th phase, the positive potential of the Balancilla moves to the Wularshan region with high abnormality, and the intensity is gradually increased. In phase 5, the intensity of the positive potential height moving to the east is slightly reduced. In the 6 th and 7 th phase, the potential height abnormality of east shift is combined with the normal potential height abnormality of far east region, and the intensity is enhanced again. Until phase 8, negative anomalies were noted in Wularshan and positive anomalies were noted in Beigal lake north. In the whole process, the potential altitude abnormality of the east Asia region has a more obvious response center. The phases 1-4 and the phases 5-8 form the distribution characteristic of the height abnormality of the opposite potential. The phase obtained by the real-time index synthesis based on east China clearly reflects the observation characteristic that the Eurasian potential altitude anomaly is propagated to the southeast from the Balanus at high latitude and the response condition of the east asian region.

Plum rain is the product of wind propulsion to the north in summer seasons and is also significantly affected by medium and high latitude atmospheric circulation. FIG. 9a shows the relationship between quasi-bi-periodic potential altitude oscillation real-time index (EASO-W) transmitted in western province at high latitude 10-30d in Eurasia and plum entering in Jianghuai basin in China. According to the plum entering date provided by the climate center, the date point of the plum entering in the year of 1979-2019 is on the phase diagram. As can be seen, the real-time index average intensity of 10-30d at the middle and high latitudes is larger when the plum blossom is carried out in most years, and the intensity is lower than 0.5 in only 6 years in 40 years. The plum is 65% of the total year in the period of phase 5-8. Phase 4 was only 1 year old to plum. The east-handed European Asia middle-high summer quasi-bi-cycle oscillation real-time index (EASO-E) is also closely related to the entering of plum in the Jianghuai river basin (figure 9b), the EASO-E strength is more than 0.5 in 35 years in 40 years, compared with the 5 th-8 th phase of the west-handed index, the entering of plum is more likely to occur in the 1 th-4 th phase of the east-handed index in the highly abnormal situation of the east-handed potential, particularly the 1 st and 2 nd phase account for 50%, and the entering of plum is less likely to occur in the 6 th phase. Both indexes better reproduce the evolution characteristics of the potential heights of Wularshan and Beigal lake areas in the key region of plum entering, so that the index has better indication significance for plum entering.

The 10-30d abnormity of the high-altitude potential in Eurasia has obvious influence on summer rainfall. As can be seen from FIG. 10, the change of rainfall in summer in China is closely related to the different phase evolution of the western-transmitted potential altitude quasi-bi-periodic oscillation (EASO-W). When the real-time index of western transmission is in the first phase, the river south and south China are rainy, and when the 2 nd-4 th phase, the Yangtze river basin is rainy; in the 5 th phase, the Yangtze river is rainy in midstream; in the 6 th phase, the river is rainy; in the 7 th phase, the Yangtze river basin is rainy; in phase 8, the Yangtze river basin and the south of the Yangtze river are rainy. FIG. 11 shows the relationship between eastern potential height quasi-bi-weekly real-time index (EASO-E) and rainfall in our country. In the 8 th and 1 st phase, the south of China is rainy, and the north is rainy; in the 2 nd to 3 rd phase, the south of the Yangtze river is slightly rainy; the 4 th phase, the Yangtze river basin and the yellow river basin are rainy; the 5 th to 6 th phases, the river basin is rainy; in the 7 th phase, the area upstream of the Yangtze river is rainy.

The 10-30d abnormity of the high latitude potential in Europe can also have a remarkable influence on the summer temperature. FIG. 12 shows the phase evolution relationship between summer temperature anomaly and western-style transmitted potential altitude quasi-bi-periodic oscillation (EASO-W) in our country. It can be seen that in the 8 th phase and the 1 st-2 nd phase, the north of China is warm and the south is cold; in phase 3, warm in China and cold in Xinjiang; in the 4 th to 7 th phases, the north is cold and the south is warm.

FIG. 13 shows the relationship of summer temperature anomaly to the east-transmitted real-time index of potential height 10-30d (EASO-E). When the 1 st phase and the 2 nd phase are shown, the north of China is warmer, and the south is colder; 3-4 phase, except Xinjiang, most areas of China are warmer; in the 5 th-6 th phase, the north of China is cold and the south is warm; in the 7 th-8 th phase, most of China is cold except Xinjiang which is obviously warm.

In 1991, the rainfall in the Yangtze river basin in China is excessive, and rare continuous rainstorm events occur from 1 to 12 months 7 in 1991, so that huge economic loss and casualties are caused. The method can be monitored by using quasi-bi-cycle real-time indexes of high altitude potential in Eurasia. For West-handed EASO-W (FIG. 14a), extreme precipitation in Yangtze river basin starts at phase 6 and ends at phase 2, and EASO-W is very strong. This is consistent with the previous results on the temporal evolution of the spatial distribution of precipitation anomalies (fig. 10). For EASO-passed EAWO-E (fig. 14b), abnormal extreme precipitation in the Yangtze river basin starts at phase 4 and ends at phase 8, again with very strong EASO-E intensity. Again, this is consistent with the previous results on the temporal evolution of the spatial distribution of precipitation anomalies (fig. 11). The two indexes are reliable for monitoring the rainfall and the extreme rainfall, and have important significance at the same time.

Claims

1. A method for extracting a quasi-bi-periodic oscillation real-time index of high latitude in Eurasia in summer is characterized by comprising the following steps of:

s3: projecting a non-filtered 500hPa potential height distance flat field containing-6, -3 and 0 days to the first two EEOF modes to obtain a western-transmitted quasi-bi-periodic oscillation real-time index at high latitude in Eurasia;

2. The method for extracting the quasi-bi-periodic oscillation real-time index of the high latitude and summer in Eurasia as claimed in claim 1, wherein during the extraction of the 500hPa potential altitude horizon by the non-filtering method for 10-30 days, the method further comprises the following steps:

3. The method for extracting the mid-high latitude summer quasi-bi-periodic oscillation real-time index in Eurasia according to claim 1, wherein the band-pass filtering for 10-30 days utilizes a Butterworth method.

4. The method for extracting the mid-high summer quasi-bi-periodic oscillation real-time index in Eurasia as claimed in claim 1, wherein the index is derived from ERA-Interim reanalysis data.

5. The method for extracting the quasi-bi-periodic oscillation real-time index of the high latitude and the middle latitude in the European Asia in summer according to claim 1, wherein the high latitude areas comprise upstream and downstream areas of the West Feng zone and high latitude areas affecting large-scale weather in China.