Abstract
Abstract. This study describes the development of the hydrological cycle model for the Globally Resolved Energy Balance (GREB) model. Starting from a rudimentary hydrological cycle model included in the GREB model, we develop three new models: precipitation, evaporation and horizontal transport of water vapour. Precipitation is modelled based on the actual simulated specific and relative humidity in GREB and the prescribed boundary condition of vertical velocity. The evaporation bulk formula is slightly refined by considering differences in the sensitivity to winds between land and oceans, and by improving the estimates of the wind magnitudes. Horizontal transport of water vapour is improved by approximating moisture convergence by vertical velocity. The new parameterisations are fitted against the Global Precipitation Climatology Project (GPCP) data set and reanalysis data sets (ERA-Interim). The new hydrological cycle model is evaluated against the Coupled Model Intercomparison Project phase 5 (CMIP5) model simulations, reduction in correction terms and by three different sensitivity experiments (annual cycle, El Niño–Southern Oscillation and climate change). The skill of the hydrological cycle model in the GREB model is now within the range of more complex CMIP5 coupled general circulation models and capable of simulating key features of the climate system within the range of uncertainty of CMIP5 model simulations. The results illustrate that the new GREB model's hydrological cycle is a useful model to study the climate's hydrological response to external forcings and also to study inter-model differences or biases.
Highlights
One topic in climate change that deserves urgent attention is the changing pattern of the hydrological cycle (Donat et al, 2016)
coupled general circulation models (CGCMs) evaluated by the Intergovernmental Panel on Climate Change (IPCC) for the fifth assessment report are among the most complex simulations of the climate system
We introduced the newly developed hydrological cycle model for the Globally Resolved Energy Balance (GREB) model
Summary
One topic in climate change that deserves urgent attention is the changing pattern of the hydrological cycle (Donat et al, 2016). Many aspects of the hydrological cycle (i.e. high precipitation in the Intertropical Convergence Zone; ITCZ) seen in complex CGCMs can be found in models with intermediate complexity such as the CLIMBER-2 (Petoukhov et al, 1999), the UVic Earth system climate model (Weaver et al, 2001) or the simple atmosphere–ocean–sea–ice model developed by Wang and Myask (2000). Stassen et al.: A hydrological cycle model for GREB and land–sea contrast (Dommenget and Floter, 2011; Izumi et al, 2015) They provide a framework to conceptually understand the hydrological response to climate change. We give a discussion and summary of the results
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