How many times does the sea rise a day? When is the high tide? Why?

The tide rises twice a day, and the tide level rises to the highest at 6: 00 am and noon 18: 00 on the first and fifteenth day of each lunar month, and drops to the lowest at 12: 00 pm and 0: 00 am. Then the daily high and low tide time was delayed by 48 minutes.

The sea level fluctuates regularly, for example, there are two waves and two small tides every day. According to the Party's life, observation and discovery, most high lakes occur around the upper and lower reaches of the moon (that is, when crossing the local meridian). Before and after the moon rises and sets, the daily high (low) tide time gradually recedes by about 48 minutes, that is, 48 minutes (0.8 hours) every night.

The two waves each month are around the first and fifteenth days of the lunar calendar, and the two small waves are around the seventh and eighth days of the lunar calendar, that is, the 22nd and 23rd days. However, in fact, the time to produce tides and small tides is not exactly the above time. Because the shape of the earth is very complex, large tides and small tides occur in all parts of the country a few days later than in theory. For example, in the coastal area of Jiaodong Peninsula, the tidal fluctuations on the 3rd and18th are relatively large, while the tidal fluctuations around10th, 22nd and 25th are minimal.

Mode 1:

1, if the lunar date is less than 15: high tide time = lunar date ×0.8 low tide time = lunar date ×0.8-6.

2. If the lunar calendar date exceeds fifteen, the high tide time = (lunar calendar date-15) × 0.8;

Low tide time = (lunar date-15)×0.8-6 calculation time 12 hours.

Mode 2:

1. Recurrence time of high tide on the same day: calculation method of last month: (Lunar days-1)×0.8+5.7 = calculation method of the second half of high tide: (Lunar days-16)×0.8+5.7 = high tide time.

2. Calculation method of the time of high tide tomorrow: high tide time today +48 minutes = high tide time tomorrow. For example, if the climax every day is more than 8 o'clock today, then the climax time tomorrow will be 8: 48. The flood season in light waters is a reliable semidiurnal tide, with two high tides a day, and the time interval between the two high tides is 12 hours and 24 minutes, and the time interval between the highest high tide and the lowest low tide is 6 hours.