Understanding model-observation discrepancies in satellite retrievals of stratospheric temperature using GISS ModelE

We will present multiple realizations of satellite-retrieved stratospheric temperature

diagnostics in historical simulations of climate change during the satellite era (specifically

1979--2021) using GISS ModelE contributions to the Coupled Model Intercomparison Project (Phase 6)

(CMIP6). The stratospheric trends in these diagnostics are affected by greenhouse

gases (notably carbon dioxide and ozone depletion), coupling with the ocean, volcanic aerosols, solar

activity and compositional and dynamic feedbacks. We explore the impacts of internal variability,

changing forcing specifications, composition interactivity, the quality of the stratospheric

circulation, vertical resolution, and possible impacts of the mis-specification of volcanic

aerosol optical depths.

Overall trends and patterns over the satellite period are well captured, but discrepancies at

all levels exist and have multiple distinct causes. We find that stratospheric comparisons

(using Stratospheric Sounding Unit (SSU) and Microwave Sounding Unit (MSU) retrievals and

successor instruments) are most affected by variations in the representation of ozone depletion

and feedbacks, followed by the volcanic signals. Tropospheric skill is affected by the trends

in ocean temperature and tropospheric aerosols, but also by the representation of stratospheric processes

through the impact of the Brewer-Dobson circulation on the height of the tropical tropopause.