The Radiative Influences of Lower Stratospheric Water Vapor Anomalies on Temperatures in the Upper Troposphere and Lower Stratosphere

Tropical lower stratospheric water vapor has consistent patterns of variability, such as the seasonal cycle/tropical tape recorder, the Quasi-Biennial Oscillation (QBO), and the El Niño–Southern Oscillation (ENSO). This variability is known to have radiative influences on local stratospheric temperatures. However, nonlocal radiative impacts of lower stratospheric water vapor variability on upper tropospheric temperatures are not well understood. A recent study by the authors suggests that the vertical structure of stratospheric water vapor anomalies could be important for radiative influences on temperatures above and below the cold-point tropopause. Such a radiative stratosphere-troposphere coupling could be important for understanding upper tropospheric temperature variability and predictability. Furthermore, if the vertical structure of stratospheric water vapor anomalies does have notable radiative effects, then proper model representation of these anomaly structures would be critical for accurate modeling of temperature variability above and below the tropopause. This study uses water vapor observations from the Aura Microwave Limb Sounder (MLS) and the Stratospheric Water and OzOne Satellite Homogenized (SWOOSH) datasets, MLS temperature measurements, and high-vertical-resolution GPS temperature measurements to investigate the radiative influences of vertical structures of water vapor anomalies on local and nonlocal temperatures. Radiative calculations are performed with the Community Atmosphere Model's offline radiative driver. Results show that consideration of the full vertical structure of stratospheric water vapor anomalies is necessary to properly estimate their radiative effects. The nonlocal radiative influences of lower stratospheric water vapor variability patterns (e.g. the tropical tape recorder, QBO) on upper tropospheric temperatures are quantified.