The tropospheric moisture and double-ITCZ biases in CMIP5 models

Abstract:

Based on Atmospheric Infrared Sunder (AIRS) Obs4MIPs data, Tian et al. (2013) evaluated the climatological mean tropospheric air temperature and specific humidity simulations in Phase 5 of the Coupled Model Intercomparison Project (CMIP5) models. They found that most CMIP5 models have a cold bias in the extratropical upper troposphere and a double-Intertropical Convergence Zone (ITCZ) bias in the whole troposphere over the tropical Pacific. They also pointed out the cloud-related sampling biases in the AIRS Obs4MIPs air temperature and specific humidity climatologies that were later quantified by Hearty et al. (2014). In this study, we will continue comparing the tropospheric specific humidity climatologies between the CMIP5 model simulations and the AIRS Obs4MIPs data after correcting the AIRS data sampling biases to quantify the overall tropospheric moist or dry bias of CMIP5 models. In particular, we will quantify the strength of the double-ITCZ bias in each individual CMIP5 model and discuss its possible implication for climate sensitivity and climate prediction.