Evaporation
The evaporation converts surface water into water vapour. In this way, part of the water is returned to the atmosphere naturally. The evaporation requires energy, which makes it cooler next to plants than in built-up areas.
The evaporation process distinguishes between evaporation on free water surfaces and ungrown surfaces (evaporation) and evaporation on plant surfaces (transpiration).
On planted areas up to 40 % of the precipitation water can evaporate. Whereas on built-up areas such as streets and houses only 10 % of the rainwater evaporates. In addition, the proportion of water that can evaporate depends on temperature and humidity. The higher the temperature and the lower the humidity, the more water can evaporate.
Energy is released during the phase transition from the liquid state to the gaseous state. This creates a cooling effect by evaporation, which protects plants and dogs (pikes) from overheating. This cold can also be used for cooling in cities.
Research question
What is the temperature difference between a meadow and an asphalted surface?
- Thermometer
- Meadow or other greened area
- Asphalted or otherwise cultivated surface
Test performance
With the thermometer the temperature is measured one after the other approx. 10 cm above the meadow and the asphalted surface.
Experimental observations
A lower temperature is measured on the meadow than on the asphalted surface. The difference in temperature should be clearly visible on a sunny day. The difference is due to the evaporation cold that occurs during transpiration.
- Lysimeter
- Evaporation dish