Perigee
Topic: Movements of Ocean Water: Waves, Tides and Currents · NCERT: Class 11, Ch 13 "Movements of Ocean Water"
Meaning
Perigee is the point in the Moon's orbit where it is closest to the Earth, about 363,000 km away. The Moon's orbit is an oval, so it comes nearest once a month. At perigee the Moon's pull is stronger than usual. High tides are higher, low tides are lower, and the tidal range (the gap between high and low water) is larger. A full moon at perigee looks bigger and brighter and is called a supermoon. When perigee falls on a spring tide, the result is a "king tide", which can flood low coasts.
Example
When a supermoon falls on a spring tide, low-lying coasts such as the Hooghly estuary near Kolkata, West Bengal, see unusually high water. Coastal flooding is more likely then.
Don't confuse with
- Perihelion: this is the Earth's closest point to the Sun, around 3 January. Perigee is about the Moon and the Earth. Saying "the Moon is closest at perihelion" is a common exam trap.
- Apogee: the Moon's farthest point, when the tidal range is smaller.