Coastal and inland climates

The sun rises over two cities in two different locations. A new day dawns, and there is not a cloud in the sky. It’s summer, and the temperature rises as the sun blazes. But watch the thermometers. Here in the inland city the temperature rises quickly.

By lunchtime it’s hot. Here by the coast, the temperature rises more slowly. It does get warm, but not as hot as inland. It’s the same sun, the same season, and the two locations are the same distance from the equator. So, equal amounts of heat from the sun radiates toward the two cities.

How come the temperature rises faster inland than by the sea? The simple answer is: water! Here is a beaker containing one kilogram of water. Here is a beaker containing a mix of sand and rock that also weighs one kilogram. To start with, they are the same temperature.

Now let’s heat up the beakers with the same amount of heat to them both. And watch! The temperature of the sand and rock rises a lot faster. So, sand and rock heat up faster than water. Remember this, because it will help us understand some things about temperature and climate.

Let’s go back to the cities and compare them. Here, by the coast, the water in the ocean is slowly heated by the sun’s rays. The sun blazes for the whole day, but the temperature of the water changes slowly - the water temperature is stable. The ocean is in contact with the air above, so the water affects the air. The air does become warmer during the day, but it is cooled off constantly by the water in the sea with its stable temperature.

This means the air temperature rises slowly. Here inland there is no sea, no water. The energy from the sun quickly heats up the rock and the soil, just like it did in the beaker. The temperature of the ground, and the air above, increases quickly, and it gets hot. So the temperature in areas with water — seas and large lakes — stays more even compared to locations with less water.

The temperature varies more inland than by the coast. Now let’s compare the temperature in these cities over one full year, from January to December. On the horizontal axis we see the months of the year. On the vertical axis is the average temperature in degrees Celsius. In the city by the coast it’s cold in January.

The average temperature increases during springtime, reaches a peak in July, and then decreases again as the summer turns into autumn and winter. Inland, the average temperature is even lower in January. But during springtime, the temperature increases faster than by the coast, and in the middle of the summer it’s a lot warmer. During autumn, the temperature quickly decreases again, and in mid-winter the average temperature is low. Winters are colder inland.

So the climate by the coast has a more even temperature over the year compared to inland. This is what makes coastal climates different from inland climates. Coastal climates are also more humid than inland climates, again because of the nearby water. In coastal climates, the water is warmed up slowly in the spring, and this causes the air to warm up slowly. The same water gives off heat slowly in the autumn, so that the temperature decreases slowly.

While inland climates are drier, and here the temperatures vary more. There are colder winters and hotter summers.