China News Service, Guangzhou, July 13 (Guo Jun and Li Jianji) According to the prediction of Guangzhou Wuyang Planetarium, on July 14 and 15 this year, the largest astronomical tide in the second half of this year will occur in the Pearl River section of Guangzhou ( excluding storm surge), the highest tide level will be at noon and afternoon.
The reasons for this astronomical spring tide are mainly astronomical and hydrological factors.
The astronomical factors are: at 17:06 on July 13, the moon moved to "perigee", and the Earth and the moon are the closest throughout the year, only 357,372 kilometers, resulting in a "near-earth spring tide"; July 14 at 2:38 When the moon, the earth and the sun line up in an approximately straight line, a "syzygy tide" occurs.
These two astronomical tides converge in a short period of time to become a significant astronomical tide.
The hydrological factors are: some time ago, the highest water levels of the Xijiang and Beijiang in the Pearl River Basin exceeded the warning water level.
The current water level of the Pearl River is also higher than that of the same period last year.
At 14:00 on July 11, the water level of the Xijiang Wuzhou Hydrological Station was 11.29 meters; the Beijiang Shijiao Hydrological Station, the water level was 4.24 meters.
The highest and lowest tide levels of the Pearl River in Guangzhou: 12:40 and 22:05 on July 14; 13:30 and 23:00 on the 15th; 14:20 and 23:00 on the 16th 45 points.
The time of the highest climax is delayed by about 50 minutes every day.
The maximum tidal range (the highest tide minus the lowest tide) is close to 3 meters.
After July 16, the highest tide level of the Pearl River in Guangzhou will drop significantly.
The tidal nature of the Pearl River in Guangzhou is irregular semi-diurnal, with two high tides and low tides every day.
In most cases, however, the heights of the two high tides are not equal, nor are the lengths of time from low tide to high tide or from high tide to low tide.
Experts say that the flood season in Guangzhou can be divided into pre-flood season and post-flood season.
At present, Guangzhou has entered the post-flood season, and it is necessary to beware of storm surges caused by typhoons.
Astronomical spring tides can be predicted for a long time in advance, and usually will not cause greater harm to the public; however, storm surges caused by typhoons are difficult to predict several weeks in advance.
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