It is lovely to walk at the beach, but sometimes the humidity can make it uncomfortable. People who live in coastal towns know the challenge of drying laundry and keeping mold at bay due to the high humidity in the air. What is humidity, and why are beaches so humid.
Humidity is a term that indicates the amount of water molecules in the air. It is measured as a percentage of the total amount of water the air can hold. The air at the beach has a higher humidity because of the proximity to the sea. The water molecules gain energy from the sun, evaporate and form water vapor.
It may be confusing to understand why humidity levels vary on different days and why some coastal towns have higher humidity than others.
What Is Humidity?
Humidity refers to the amount of water vapor or water molecules found in the atmosphere. You will always see humidity expressed as a percentage on weather reports. The amount of water vapor is calculated as a percentage of the total water vapor the atmosphere can hold.
One hundred percent humidity is also known as dew point. It refers to the state where the atmosphere is saturated with water molecules, and the water begins to condense. This means that the water vapor changes back into a liquid state, forming droplets on the ground and other surfaces.
How Do The Water Molecules Get Into The Air?
The water in the ocean consists of water molecules held in place as a liquid by intermolecular forces. The sun warms the surface water in the sea, providing energy in the form of heat.
The sun’s heat energy causes the water molecules to begin moving around, and eventually, the intermolecular forces are overcome. This frees the molecules from the liquid, allowing them to move into the air as water vapor or gas molecules.
The water vapor molecules have a lot of energy from the sun’s heat. This energy causes them to rise through the layers of air, creating an updraft or convection current. As these warmed energized molecules leave the surface of the water, other water molecules take their place. They are heated, and the cycle continues.
In this way, water molecules from the sea are taken up into the atmosphere and create humidity.
Why Does Humidity Differ Daily In The Same Location?
When you consult a weather report, you may see that the humidity is different on different days, and there is a seasonal variation. The reason for this lies with the sun and the angle of the earth’s axis.
On hot days when the sun shines brightly, more heat energy is transmitted through the atmosphere from the sun to the water. The greater heat energy results in more water molecules gaining enough energy to overcome the intermolecular forces in the water. Another way of explaining this is that the heat allows more water to turn into gas.
If there is thick cloud cover that does not allow the sun to transmit as much heat, the humidity will reduce. The effect will be especially noticeable if the cloudy conditions persist for a few days.
The earth rotates on an angled axis, which means that in summer, the land in that hemisphere is angled towards the sun. This results in hotter conditions allowing for greater humidity.
The hemisphere is angled away from the sun in winter. The sun’s rays reaching the region are weaker and do not transmit as much heat. This results in cold temperatures and reduced humidity.
Why Do Coastal Cities Vary In Humidity?
Coastal cities vary in humidity due to factors that affect the atmospheric temperature of the city and the temperature of the ocean at that point on the coast.
A region’s temperature is influenced by its distance from the equator. Areas, towns, or cities close to the equator have higher temperatures with less seasonal temperature variation. Regions further from the equator have cooler summers, and winters have low icy temperatures.
Therefore, beaches close to the equator usually have higher humidity than those further away from the equator. Coastal southern states in the USA generally have higher humidity than coastal states in the north.
Ocean currents may be hot or cold, depending on where they originate. Currents that arise in the polar regions will be icy. Those currents that originate in equatorial latitudes will be warm. Coastal currents pass close to the land and influence humidity in two ways.
- Warm currents need less energy from the sun to form water vapor. If the coastal current is warm, the humidity will be high.
- Ocean currents can affect the air around the beach and warm it or cool it down. Polar or cold coastal currents result in cooler environmental temperatures, which cause lower humidity levels.
If there is a cold coastal current, it is not uncommon to find that the coast or area around the beach is dry, and some are even deserts. The cold currents make rainfall in the adjacent land unlikely. There is so few water molecules in the air that condensation levels are seldom reached.
Alternatively, there may be fog from the sea, but the conditions that allow condensation never occur. An example of such a desert is the Atacama Desert on the Pacific coast of Chile.
Geographical features such as coastal mountain ranges, regional winds, and climatic conditions such as atmospheric pressure systems can affect humidity. It can be increased or decreased by these factors.
Why Do We Feel Uncomfortable In High Humidity?
When our bodies are hot, they perspire, allowing moisture or sweat to form on our skin. As the perspiration evaporates, it cools down our skin and provides relief from the heat. In conditions of high humidity, perspiration is less likely to evaporate as the atmosphere is already soaked with water vapor. This means it is difficult for us to cool down.
In highly humid conditions, we feel damp and sweaty as perspiration does not evaporate. In addition, if the humidity levels are almost at dew point, the water vapor may begin condensing on our warm skin, making us even soggier.
Breathing in highly humid conditions can be uncomfortable due to the high water content in the air. The high humidity means there is less available oxygen in the air, and we must breathe more often to gain sufficient oxygen.
Humid air allows smells to proliferate and spread quickly through the air. You are more likely to smell unpleasant odors from rubbish bins, drains, and sewers in humid conditions.
Conclusion
It is more humid at the beach because any large body of water allows more evaporation to occur, resulting in higher water content in the air. Evaporation and humidity levels will be highest at the coastline and beaches.
References
- https://www.scientificamerican.com/article/what-causes-humidity/
- https://www.pbs.org/newshour/science/8-things-didnt-know-humidity
- https://eo.ucar.edu/kids/sky/water2.htm
- https://www.weather.gov/lmk/humidity
- https://www.nationalgeographic.org/encyclopedia/desert/
