India has reached new heights as a new study by the researchers of Indian Institute of Tropical Meteorology (IITM), Pune, reveals that nearly one-fourth of the rain that pours over the northern Western Ghats during the Southwest monsoon evaporates before it even reaches the ground. This is exciting research that tells about how rainfall behaves during the monsoon and could help to improve the weather and climate forecasting in India.
This is the first study in the country to directly measure the amount of rain that evaporates while falling through the atmosphere. The findings have been published in the peer-reviewed journal Atmospheric Chemistry and Physics. According to the research, an average of 25% of the total rain evaporates mid air before reaching the ground during the monsoon months of June to September. Note that this percentage is not fixed as the daily evaporation range varies as low as 4% to as high as 61%. Well this simply means that such a portion of the rain seen in clouds never actually reaches the ground but disappears into the atmosphere during its journey downward. This is a concerning matter as when raindrops evaporates before reaching the ground it absorbs heat from the air that results in cooling the air making it denser and heavier. The cooler air then sinks rapidly towards the surface, creating a pool of cold air. This is one of the major findings as it is India's first experiment that will directly estimate how much rainfall evaporates while falling through the atmosphere. Researchers also noted that the average evaporation rate over India is lower than estimates reported from several other parts of the world. According to the study, around one in every four raindrops evaporates before reaching the ground in the Indian monsoon region. The findings are expected to serve as the foundation for larger studies across the country. Rather than counting raindrops, a scientific approach involving isotopes was carried out by the researchers. Water is basically comprised of hydrogen and oxygen atoms. However, there is an insignificant percentage of the water that contains naturally occurring heavier versions of these atoms, called heavy isotopes. Water containing lighter isotopes tends to be more volatile than that carrying heavy isotopes. The lightest water molecules are those that evaporate first when raindrops are passing through dry air. This means that what remains are raindrops that contain more of heavy isotopes. Scientists can tell the extent of evaporation by analysing the ratio of light and heavy isotopes of the rainwater collected. Less evaporation occurs in the rain that has a lighter isotopic ratio while more evaporation occurs in rain with heavy isotopic ratio. This Pune based research is only a beginning, IITM already operates a rainwater isotope observation network across nine locations in India including Port Blair, Himalayas and northeastern states.One in Four Raindrops Evaporates
Researchers believe that this new finding will help the scientists better understand the rainfall patterns.Why Rain Evaporation Matters
The cooling effect plays a vital role in the formation and movement of rain clouds.Study Marks First Direct Measurement in India
How Scientists Measured Rain Evaporation
Wider Research Across India