GB/T 33671-2017 Meiyu Monitoring Indicators GB/T33671-2017 |tt||Standard compression package decompression password: www.bzxz.net
This standard specifies the definition, indicators and calculation methods of the occurrence, interruption, end and intensity of Meiyu in the Yangtze and Huaihe River Basin. ? This standard is applicable to Meiyu monitoring, forecasting, evaluation and services. ?

ICS07.060
National Standard of the People's Republic of China
GB/T33671—2017
Meiyu monitoring indices
Published on 2017-05-12
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China Standardization Administration of China
Implementation on 2017-12-01
This standard was drafted in accordance with the rules given in GB/T1.1-2009. This standard was proposed by the China Meteorological Administration.
This standard is under the jurisdiction of the National Technical Committee for Climate and Climate Change Standardization (SAC/TC540). GB/T33671—2017
Drafting units of this standard: National Climate Center, Shanghai Regional Climate Center, Wuhan Regional Climate Center, Anhui Provincial Climate Center, Jiangsu Provincial Climate Center, Yangzhou Meteorological Bureau.
The main drafters of this standard are: Zhou Bing, Liang Zang, Wang Dongqian, Zhou Yuehua, Xu Min, Xiang Ying, Qin Mingrong. I
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GB/T33671—2017
Meiyu is a unique weather and climate phenomenon in East Asia. It is the product of the periodic activity of the East Asian summer monsoon. It mainly appears in the area from the Jiangzhun River Basin in China to South Korea and Japan from June to July. The average annual Meiyu in the Jiangzhun River Basin is more than 300 mm, accounting for 30% to 40% of the total annual precipitation. Meiyu has significant interannual and interdecadal variation characteristics, obvious regional characteristics, and is closely related to the development of the national economy and people's lives. In order to promote the standardization and objectivity of Meiyu determination in the Jiangzhun River Basin, this standard is specially formulated. HiiKAoNhiKAca
1Scope
Meiyu Monitoring Indicators
GB/T33671—2017
This standard specifies the definitions, indicators and calculation methods of the occurrence, interruption, end and intensity of Meiyu in the Jiangzhun River Basin. This standard applies to Meiyu monitoring, forecasting, evaluation and services. Terms and Definitions
The following terms and definitions apply to this document. 2.1
Meiyu
Mainly occurs in the Jianghuai River Basin in June and July. The continuous precipitation process with a long rainy period. 2.2
Daily precipitationdailyaccumulatedprecipitationThe accumulated precipitation from 20:00 the previous day to 20:00 the current day. [QX/T52—2007, definition 3.2]
Note: The unit is meter (mm).
Daily average temperaturedailyaveragetemperatureThe average temperature of the four hours of 02:00, 08:00, 14:00 and 20:00 on the same day. [QX/T50—2007 definition 3.1]
Note: The unit is degrees Celsius (℃).
Rainy dayrainday
The day when the daily precipitation is greater than or equal to 0.1 mm. 2.5
Ridge of subtropical high
The average position of the ridge of the 500hPa western Pacific subtropical high in the range of 110°～130°E. [QX/T304—2015, definition 4.3]
3 Meiyu monitoring indicators
3.1 Monitoring scope and division
The Meiyu in the Yangtze and Huaihe River basins is divided into three regions for monitoring, namely Jiangnan region (I), middle and lower reaches of the Yangtze River region (II), and Jianghuai region (III). See Figure A.1 in Appendix A. The representative stations of the Meiyu monitoring area in each division are: 65 stations in Jiangnan region, 157 stations in middle and lower reaches of the Yangtze River region, and 55 stations in Jianghuai region, see Table B.1 in Appendix B.
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3.2 Monitoring indicators
3.2.1 Regional rainy day
On a certain day, more than 1/3 of the monitoring stations in the monitoring area have precipitation greater than or equal to 0.1 mm, and the daily average precipitation in the area is greater than or equal to 2.0 mm.
3.2.2 Rainy Season Start Date
Starting from the first rainy day, if the proportion of rainy days in the next 2, 3, 10 days accounts for ≥50% of the total number of days in the corresponding period, then the first rainy day is the rainy season start date. There will be no new rainy season start date after July 20. 3.2.3 Rainy Season End Date
Starting from the last rainy day of the rainy season, if the proportion of rainy days in the previous 2, 3, …, 10 days accounts for ≥50% of the total number of days in the corresponding period, then the last rainy day is the rainy season end date. In the case of an abnormally long rainy season, the day before the first non-rainy day after the rainy season enters August is the rainy season end date. If this does not meet the rainy season end date conditions, it is necessary to calculate forward to determine the rainy season end date. The rainy season end date should occur before the beginning of autumn.
3.2.4 Rainy season
A rainy season must meet the following conditions: the proportion of rainy days in any consecutive 10 days is greater than or equal to 40%, the number of rainy days is greater than or equal to 6 days, and there are no non-rainy days for more than 5 consecutive days (including 5 days), and the station average precipitation intensity is greater than or equal to 5mm/d. The length of a rainy season is the number of days from the start day to the end day of the rainy season. 3.2.5 The beginning of the plum rain season
The beginning day of the first rainy season is the plum rain season. At this time, the subtropical high pressure in the western Pacific jumps north for the first time, and the ridge line of the subtropical high is located between the corresponding southern and northern boundaries (see Table 1). The plum rain season begins as early as late May, in a high temperature and high humidity environment, with an average daily temperature greater than or equal to 22℃.
Table 1 Activity range of the subtropical high ridgeline during the Meiyu period
Regional selection
Jiangnan region
Middle and lower reaches of the Yangtze River
Jianghuai region
3.2.6 End of Meiyu period
≥18°N
≥19°N
≥20N
<25°N
<26°N
The day after the end of the last rainy period is the end of Meiyu period. At this time, the western Pacific subtropical high jumps northward for the second time, and the position of the subtropical high ridgeline exceeds the northern boundary.
3.2.7 Meiyu period
There can be more than one rainy period during the Meiyu period. The length of the Meiyu period is the cumulative number of days from the Meiyu day to the day before the end of Meiyu period. 3.2.8 Subtropical high ridgeline during plum rain period
During plum rain period, the position of subtropical high ridgeline 5d sliding needs to meet the following conditions (see Table 1). When the position of subtropical high ridgeline 5d sliding exceeds 2 latitudes of the northern boundary position by 12
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, and there is no continuous rainy day, and the monitoring area has high temperature and dry weather, the plum rain period in this area ends. 3.2.9 Empty plum rain
According to the monitoring indicators, it is impossible to determine the effective plum rain period between June and July, and it is determined to be empty plum rain. 3.2.10 Second plum rain
After entering the plum rain period, the first rain period is confirmed to be over, the plum rain period is interrupted, and then continuous precipitation occurs, and the position of the subtropical high ridgeline can meet the judgment conditions of Table 1, it can enter the second rain period, that is, "second plum rain". 3.2.11 Regional Plum Rain Season
The Plum Rain Season in the three regions of Jiangnan (I), the middle and lower reaches of the Yangtze River (II) and the Jianghuai (III) is determined as the start (end) date of the Plum Rain Season in the region based on the Plum Rain Season Day and the End Plum Rain Season Day in the monitoring area. The cumulative number of days from the Plum Rain Season Day to the day before the end of the Plum Rain Season is the length of the regional Plum Rain Season.
3.2.12 Plum Rain Precipitation Concentration Period
The period composed of multiple rainy periods (excluding rainy period interruptions) is called the Plum Rain Precipitation Concentration Period. 3.2.13 Plum Rain Season
The earliest start date of the Plum Rain Season in the three regions is the Plum Rain Season Day in the Jiangzhun River Basin, and the latest end date is the end date of the Plum Rain Season. The length of time between the day before the end of the Plum Rain Season and the Plum Rain Season Day is the Plum Rain Season. 3.2.14 Average precipitation during the plum rain season
The average cumulative daily precipitation in the plum rain area during the plum rain season is the average precipitation during the plum rain season in the Yangtze and Huaihe River Basin. 3.3 Calculation of plum rain intensity
3.3.1 Regional plum rain intensity
The regional average precipitation during the plum rain period, that is, the average of the total precipitation during the plum rain period of all plum rain monitoring stations in the region is the plum rain intensity of the region. Its calculation is shown in formula (1):
Where:
P—rainfall intensity during the plum rain period in a certain region;
P, the total precipitation during the plum rain period at the i-th station in the region; N——the total number of stations in the region.
3.3.2 Regional plum rain intensity indexbzxZ.net
The calculation of the regional plum rain intensity index (M) is shown in formula (2): M=
L+0.5(R/L)+R
+(R。/L)
Wherein:
MRegional plum rain intensity index
L—The length of the plum rain season in a certain year (number of days): L。—The average length of the plum rain season in previous years (number of days); R。
.（1）
.（2）
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—The total precipitation at the monitoring station during the plum rain season in a certain year; R
R。—The average total precipitation at the monitoring station during the plum rain season in previous years. Table 2
M boundary value
Plum rain intensity
M≤-1.25
Grade classification of regional plum rain intensity index
-1.25
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