Contemporary GCM Fidelity in Representing the Diurnal Cycle of Precipitation Over the Maritime Continent

Abstract

This paper presents a multimodel assessment of fidelity in representation of the diurnal cycle of precipitation over the Maritime Continent (MC). Daily mean precipitation rate and amplitude and phase of the diurnal cycle are utilized to validate General Circulation Model (GCM) performance with respect to multiyear annual mean and seasonal cycle. The analysis shows that models' 6-hourly temporal resolution and 2.5° spatial resolution is sufficient to depict key characteristic of diurnal precipitation. Results show that most models are sensitive to the existence of the MC and show different characteristics of subdaily precipitation. However, 19 out of 20 models underestimate the daily mean precipitation over the eastern Indian Ocean and most of them underestimate both daily mean precipitation and amplitude of the diurnal cycle, especially over islands within the region. Observations show that within the MC the diurnal cycle is higher over land than over ocean. Many models decrease this land-sea contrast. Most models recognize difference in phase of the diurnal cycle between MC islands and surrounding ocean, but some of them show opposite phasing of the diurnal cycle. Results show that modern models perform better than past generation, sometimes comparably to regional models' run in much higher resolution. Although models perform well with respect to the seasonal cycle of the daily mean precipitation, they fail to realistically represent the seasonal evolution of the diurnal cycle amplitude. Additionally, models show no coherence in land-ocean contrast derived from a multiyear average of daily mean precipitation and amplitude of the diurnal cycle.