Researchers from Japan presented a satellite analysis of precipitation in their region. They found that the increase in rainfall over the past 20 years has become a trend.
Researchers at the University of Tokyo Metropolitan University analyzed long-term rainfall radar data from satellites and found a significant increase in rainfall over the past decade in East Asia. These data span 23 years and provide an unprecedented insight into how precipitation patterns have changed. They showed that the increase in precipitation is due to a decade of increased moisture transport from the tropics.
Scientists have noticed that from the second half of June to the first half of July, especially a lot of precipitation falls in East Asia. This occurs when the flow of humid air in the Asian monsoon region meets anticyclonic flows in the western subtropics. While they bring much-needed water to the region, their recent floods have become deadly and cause widespread destruction; floods in China and Japan in 2020 were particularly devastating.
The researchers wanted to understand if there is a trend in this phenomenon. To do this, they combined two datasets that span 23 years and cover both sea and land with equal accuracy. After conducting a thorough analysis of the time series, they confirmed a significant increase in precipitation over the past decade. In particular, they showed that there has been a clear increase in the amount of extreme precipitation – such that can provoke natural disasters.
The team focused on two aspects of precipitation development – moisture transport and changes in airflow in the upper troposphere. They showed that increased water vapor transport due to decreased tropical cyclone activity. In addition, scientists noticed showed that there were depressions in the upper troposphere, which influenced air circulation, which changed the nature of precipitation.