Kysyjä tarkoittanee vuosina 1984-1986 tehtyä Riptide-sarjaa
People caught in a rip current may notice that they are moving away from the shore quite rapidly. Often, it is not possible to swim directly back to shore against a rip current, so this is not recommended. Contrary to popular misunderstanding, a rip does not pull a swimmer under the water. It carries the swimmer away from the shore in a narrow band of moving water.
According to the NOAA rip currents caused an average of 71 deaths annually in the United States over the ten years ending in 2022 (with 69 in 2022).
In a rip current, death by occurs when a person has limited water skills and panics, or when a swimmer persists in trying to swim to shore against a strong rip current, and eventually becomes exhausted and drowns.
Ristiaallokko ; Pelkäsin hammaslääkäreitä ja pimeää
Rip currents typically flow at about 0.5 m/s (1.6 ft/s). They can be as fast as 2.5 m/s (8.2 ft/s), which is faster than any human can swim. Most rip currents are fairly narrow, and even the widest rip currents are not very wide. Swimmers can usually exit the rip easily by swimming at a right angle to the flow, parallel to the beach. Swimmers who are unaware of this fact may exhaust themselves trying unsuccessfully to swim directly against the flow. The flow of the current fades out completely at the head of the rip, outside the zone of the breaking waves, so there is a definite limit to how far the swimmer will be taken out to sea by the flow of a rip current.
Rip currents are a potential source of danger for people in shallow water with breaking waves, whether this is in seas, oceans or large lakes. Rip currents are the proximate cause of 80% of rescues carried out by beach .
A rip current is like a moving , which the swimmer can get out of quite easily by swimming at a right angle, across the current, i.e. parallel to the shore in either direction. Rip currents are usually not very wide, so getting out of one only takes a few strokes. Once out of the rip current, getting back to shore is not difficult, since waves are breaking, and floating objects, including swimmers, will be pushed by the waves towards the shore.
In the United States, some beaches have signs created by the (NOAA) and , explaining what a rip current is and how to escape one. These signs are titled, "Rip Currents; Break the Grip of the Rip". Two of these signs are shown in the image at the top of this article. Beachgoers can get information from lifeguards, who are always watching for rip currents, and who will move their safety flags so that swimmers can avoid rips.
Ilmainen Sanakirja (englanti-suomi)
Rip currents often look somewhat like a road or river running straight out to sea. They are easiest to notice and identify when the zone of breaking waves is viewed from a high vantage point. The following are some visual characteristics that can be used to identify a rip:
Käännös riptide – Sanakirja suomi-Englanti
Rip currents have a characteristic appearance, and, with some experience, they can be visually identified from the shore before entering the water. This is helpful to lifeguards, swimmers, surfers, boaters, divers and other water users, who may need to avoid a rip, or in some cases make use of the flow.
Pelkäsin nättejä tyttöjä ja keskustelujen aloittamista
The vorticity and inertia of rip currents have been studied. From a model of the vorticity of a rip current done at Scripps Institute of Oceanography, it was found that as a fast rip current extends away from shallow water, the vorticity of the current increases, and the width of the current decreases. This model acknowledges that friction plays a role and waves are irregular in nature. From data from Sector-Scanning Doppler Sonar at Scripps Institute of Oceanography, it was found that rip currents in La Jolla, California, lasted several minutes, that they reoccurred one to four times per hour, and that they created a wedge with a 45° arch and a radius of 200–400 meters.
pieraista; halkaista; repiä; revetä ..
In the formation of a rip current, a wave propagates over a sandbar with a gap in it. When this happens, most of the wave breaks on the sandbar, leading to "setup". The part of the wave that propagates over the gap does not break, and the "setdown" continues in that part. Because of this phenomenon, the mean water surface over the rest of the sandbar is higher than that which is over the gap. The result is a strong flow outward through the gap. This strong flow is the rip current.
riptide; rive; roue; snag · split
A more detailed and technical description of rip currents requires understanding the concept of . Radiation stress is the force (or momentum flux) that is exerted on the water column by the presence of the wave. When a wave reaches shallow water and , it increases in height prior to breaking. During this increase in height, radiation stress increases, because of the force exerted by the weight of the water that has been pushed upwards.