The distribution of precipitation and the spread in tropical upper tropospheric temperature trends in CMIP5/AMIP simulations

Abstract

Reconciling observations and simulations of tropical upper tropospheric temperature trends remains an important problem in climate science. Examining atmospheric models running over observed sea surface temperatures (SSTs), Flannaghan et al. (2014) show that this reconciliation is affected by the SST data set used and that a precipitation‐weighted SST (PSST) is valuable in explaining this result. Here we show that even for Coupled Model Intercomparison Project Phase 5 Atmospheric Model Intercomparison Project (CMIP5 AMIP) simulations forced with identical SSTs, tropical upper tropospheric temperature trends across models (and between ensemble members) show a substantial spread (standard deviation ∼10% of the average trend). About 60% of this spread between ensemble means, as well as deviations from the ensemble means, can be explained by PSST calculated from the time‐evolving precipitation in each model run. Both PSST and atmospheric temperature trends show statistical evidence for systematic differences between models. We conclude that the response of precipitation patterns to changes in SST patterns is a significant source of uncertainty for tropical temperature trends.

The impact of eastern equatorial Pacific convection on the diversity of boreal winter El Niño teleconnection patterns

“…The use of the RSST criterion to define EPC and EPN El Niño is based on the assumption that tropical tropospheric temperatures closely follow the tropical mean SST. Although we believe that the validity of this assumption is reasonable enough for the purposes of this study, recent work suggests that there may be substantial deviation from this tendency, particularly on interdecadal timescales (Flannaghan et al 2014;Fueglistaler et al 2015). Therefore, there may be room to refine the convective eastern Pacific criterion, perhaps through the incorporation of precipitation-weighted SST instead of the tropical mean SST, but such refinements would come at the cost of added complexity.…”

Observational Evidence for Two Modes of Coupling Between Sea Surface Temperatures, Tropospheric Temperature Profile, and Shortwave Cloud Radiative Effect in the Tropics

“…The mechanism underlying the previous multiple linear regression builds on the expectation that the tropical average boundary layer temperature is closely tied to , while the tropical average‐free tropospheric temperature is closely tied to SSTs in the warmest regions with atmospheric deep convection (Flannaghan et al, ; Fueglistaler et al, ; Sobel et al, ; Zhang, ). To be precise, the relation is for subcloud moist entropy, but over the ocean the latter forms a fairly compact, monotonic relation with SSTs and we may use SST as proxy for subcloud moist entropy.…”

On the role of ozone feedback in the ENSO amplitude response under global warming

“…It is well known that the modeled magnitude of upper tropospheric warming under greenhouse gas forcing is uncertain [Fueglistaler et al, 2015;Sohn et al, 2016]. In addition, models differ in their zonal mean and regional ENSO changes under climate change [Christensen et al, 2013;Bellenger et al, 2014].…”