An Assessment of Atmospheric Convection Trends Over India Using Radiosonde Derived CAPE and Other Proxies

Convective Available Potential Energy (CAPE) is widely considered a good measure of atmospheric convection. Though there is a general consensus among the scientific community about the increasing trend of atmospheric convection in a warming scenario, the tropical region presents an uncertain picture of atmospheric convection as recent studies report disagreement between radiosonde and ERA5-derived CAPE trends. In this study, we attempt to address this uncertainty over the Indian region by considering several other proxies of atmospheric convection, namely surface equivalent potential temperature, outgoing longwave radiation, upper tropospheric carbon monoxide, convective precipitation and lightning in addition to the CAPE trends obtained from radiosonde based observations and ERA5 model-based data sets for the period 2001 to 2024. Our results of radiosonde-reported CAPE from 29 stations spread across the entire India show a significant decreasing trend at 0Z (−30.85 J/kg/year), whereas a slightly increasing trend (0.5 J/kg/year) is observed over these stations in ERA5 CAPE data sets at 0Z. Further, our analysis reveals that the CAPE trend based on radiosonde observations over India is reversed if we compute CAPE following the surface-based approach (i.e., SBCAPE). The disagreement between radiosonde and ERA5 CAPE trends raises questions about the reliability of radiosonde-reported CAPE as a measure of atmospheric convection over India. However, results from all other proxies suggest an increasing trend of atmospheric convection over India. Therefore, we conclude that inferences based solely on radiosonde-reported CAPE may not be sufficient to assess the trends of atmospheric convection over India, and a more holistic approach based on several proxies is needed.