Photograph from the International Space Station showing an overshooting storm with an anvil and above-anvil cirrus plume. Credit: ESA / NASA
A recent study published in Advances in Atmospheric Sciences has uncovered a detailed mechanism through which intense storms over the Himalayas contribute to increasing moisture in the lower stratosphere—a layer of the atmosphere crucial to global climate regulation. The research, led by Ph.D. student Li Ming and Dr. Wu Xue from the Institute of Atmospheric Physics (IAP) at the Chinese Academy of Sciences, highlights the important role of gravity waves generated by deep convection.
Stratospheric water vapor influences Earth's radiation balance, ozone chemistry, and atmospheric circulation. While it is known that some powerful storms can push moisture into the stratosphere, the exact processes over the Himalayan region—a hotspot for such storms during the Asian summer monsoon—have remained unclear.
Using high-resolution satellite data and numerical modeling, the team found that overshooting storms over the southern slope of the Himalayas excite gravity waves. These waves break and cause turbulent mixing, allowing more water vapor and ice particles to move between atmospheric layers. Additionally, the waves enhance wind shear, which promotes the formation and spread of "above-anvil cirrus plumes" (AACPs)—cloud-like structures that linger in the lower stratosphere.
