Abstract
To explore the driving mechanisms of elevation-dependent warming (EDW) over the Tibetan Plateau (TP), the output from a suite of numerical experiments with different cumulus parameterization schemes (CPs) under the Coordinated Regional Climate Downscaling Experiments-East Asia (CORDEX-EA-II) project is examined. Results show that all experiments can broadly capture the observed temperature distributions over the TP with consistent cold biases, and the spread in temperature simulations commonly increases with elevation with the maximum located around 4000–5000 m. Such disagreements among the temperature simulations could to a large extent be explained by their spreads in the surface albedo feedback (SAF). All the experiments reproduce the observed EDW below 5000 m in winter but fail to capture the observed EDW above 4500 m in spring. Further analysis suggests that the simulated EDW during winter is mainly caused by the SAF, and the clear-sky downward longwave radiation (LWclr) plays a secondary role in shaping EDW. The models’ inability in simulating EDW during spring is closely related to the SAF and the surface cloud radiative forcing (CRFs). Furthermore, the magnitude and structure of the simulated EDW are sensitive to the choice of CPs. Different CPs generate diverse snow cover fractions, which can modulate the simulated SAF and its effect on EDW. Also, the CPs show great influence on the LWclr via altering the low-level air temperature. Additionally, the mechanism for different temperature changes among the experiments varies with altitudes during summer and autumn, as the diverse temperature changes appear to be caused by the LWclr for the low altitudes while by the SAF for the middle-high altitudes.
Highlights
The Tibetan Plateau (TP), the largest and highest plateau in the world, exerts a profound impact on the global and regional climate (Duan and Wu 2005; Sato and Kimura 2007; Wu 1984), and is regarded as an early warning indicator of the global warming (Yao et al 2000)
We focus on the comparations of Weather Research and Forecasting Model (WRF) performances in simulating the temperature and elevationdependent warming (EDW) over TP, intending to investigate the major contributing factors to EDW, and to assess the sensitivity of simulated EDW to the cumulus parameterization schemes (CPs) in WRF
Similar distributions are observed for T2m, Tmax, and Tmin in the observational dataset, and the temperature distribution follows the topography of the TP, with the highest temperature in the Qaidam Basin and southeast TP and lowest temperature over the northwest corner above 5000 m (Fig. 2), which reflects the dominant role of orography on the temperature distribution over the TP
Summary
The Tibetan Plateau (TP), the largest and highest plateau in the world, exerts a profound impact on the global and regional climate (Duan and Wu 2005; Sato and Kimura 2007; Wu 1984), and is regarded as an early warning indicator of the global warming (Yao et al 2000). Climate models, which overcome the inadequacies of observations and provide enough variables to unveil the physical mechanisms driving EDW, have been widely used in temperature simulations and projections over the TP (Gao et al 2015; Ma et al 2019; Palazzi et al 2017, 2019; Rangwala et al 2010; Su et al 2013; Wang et al 2016). CPs determine the amount of precipitation and some of them occur in the form of snow over the TP, which influences the surface radiation budget and near-surface air temperature simulation All of these imply that different CPs may be an important source of uncertainty in EDW and their effects need to be systematically evaluated. The performance of CORDEX‐EA‐II simulations in simulating seasonal temperature and
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