Abstract
Abstract. The representation of the effect of tropical deep convective (DC) systems on upper-tropospheric moist processes and outgoing longwave radiation is evaluated in the EC-Earth3, ECHAM6, and CAM5 (Community Atmosphere Model) climate models using satellite-retrieved data. A composite technique is applied to thousands of deep convective systems that are identified using local rain rate maxima in order to focus on the temporal evolution of the deep convective processes in the model and satellite-retrieved data. The models tend to over-predict the occurrence of rain rates that are less than ≈ 3 mm h−1 compared to Tropical Rainfall Measurement Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA). While the diurnal distribution of oceanic rain rate maxima in the models is similar to the satellite-retrieved data, the land-based maxima are out of phase. Despite having a larger climatological mean upper-tropospheric relative humidity, models closely capture the satellite-derived moistening of the upper troposphere following the peak rain rate in the deep convective systems. Simulated cloud fractions near the tropopause are larger than in the satellite data, but the ice water contents are smaller compared with the satellite-retrieved ice data. The models capture the evolution of ocean-based deep convective systems fairly well, but the land-based systems show significant discrepancies. Over land, the diurnal cycle of rain is too intense, with deep convective systems occurring at the same position on subsequent days, while the satellite-retrieved data vary more in timing and geographical location. Finally, simulated outgoing longwave radiation anomalies associated with deep convection are in reasonable agreement with the satellite data, as well as with each other. Given the fact that there are strong disagreements with, for example, cloud ice water content, and cloud fraction, between the models, this study supports the hypothesis that such agreement with satellite-retrieved data is achieved in the three models due to different representations of deep convection processes and compensating errors.
Highlights
Simulating moist convection has long been identified as critical if general circulation models (GCMs) are to reasonably represent key features of the tropical climate (Manabe and Strickler, 1964; Manabe and Wetherald, 1967)
The composite technique is able to reveal the evolution of the model-simulated deep convective (DC) systems at a high spatio-temporal resolution and thereby evaluate the model’s ability to capture the response of upper-tropospheric moist processes to DC systems. This current study presents a continuation of Johnston et al (2013), which provides a novel application of the composite method with focus on an intercomparison of the spatio-temporal evolution of simulated DC systems of three GCMs: CAM5 (Community Atmosphere Model), ECHAM6, and EC-Earth3
We focus on the normalised probability density function of rain rates (RRs) and the diurnal
Summary
Simulating moist convection has long been identified as critical if general circulation models (GCMs) are to reasonably represent key features of the tropical climate (Manabe and Strickler, 1964; Manabe and Wetherald, 1967). Cumulus convection occupies a wide range of time- and length scales and interacts with many atmospheric processes. Individual cumulus cloud sizes are much smaller than contemporary GCM grid resolution. These clouds can later grow into large organised clusters covering an area of ∼ 103 km. For a general review of tropical convection see Moncrieff et al (2012)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
