Organized Thunderstorms Significantly Contribute to the Earth’s Energy Cycle
The Earth gains energy through the absorption of solar radiation at its surface and loses energy by emission of infrared radiation throughout the troposphere. Differential energy gain/loss between the tropics and high latitudes drives atmospheric overturning circulation that broadly determines the large-scale pattern of precipitation. For the first time, scientists used a new-generation global reanalysis data set and novel analysis techniques to investigate the characteristics of multiscale atmospheric overturning. They showed that mesoscale (< 1000 km) overturning produced by organized thunderstorms plays a comparable and dominant role as large-scale overturning in redistributing energy across the tropics.
Although mesoscale convective processes have been studied extensively in the context of weather, this study highlights the significant role of mesoscale convective processes in the global energy and water cycles. Hence this study underscores the research need at the weather-climate nexus to advance understanding of tropical convection-circulation interactions as a key element of weather and climate prediction. By providing the first estimate of mesoscale overturning, this study also provides an important benchmark for future studies of tropical circulation and precipitation.
Reliable estimates of atmospheric overturning across different spatial scales are important for understanding and predicting weather and climate variability. However, the atmospheric overturning at/below the mesoscale is poorly quantified so far. This study compared the global atmospheric overturning between the ERA5 and ERA-Interim reanalyses at a spatial resolution of 0.75o (~79 km) and 0.28125o (~31 km), respectively. Results showed that in the tropics, the mesoscale overturning in the new-generation reanalysis ERA5 is 74% of the large-scale overturning but the contribution of mesoscale overturning to the total overturning is much weaker in ERA-Interim. As an indication of deep convective clouds, satellite observations of outgoing longwave radiation suggest that the deep mesoscale overturning over the tropics is better captured by ERA5 than ERA-Interim. The results suggest that understanding the tropical overturning at meso- and convective-scales may be important to understanding the global weather and climate.