The moist static energy budget in NCAR CAM5 hindcasts during DYNAMO

Abstract

The Dynamics of the MJO (DYNAMO) field campaign took place in the Indian Ocean during boreal fall and winter of 2011-2012 to collect observations of Madden-Julian Oscillation (MJO) initiation. Hindcast experiments are conducted with an atmospheric general circulation model with varying values of a dilute CAPE entrainment rate parameter for the first two MJO events of DYNAMO from 1 October 2011 to 15 December 2011. Higher entrainment rates better reproduce MJO precipitation and zonal wind, with RMM skill up to 20 days. Simulations with lower entrainment rapidly diverge from observations with no coherent MJO convective signal after 5 days, and no MJO predictive skill beyond 12 days. Analysis of the tropical Indian Ocean column moist static energy (MSE) budget reveals that the simulations with superior MJO performance exhibit a mean positive MSE tendency by vertical advection; inconsistent with reanalysis that indicates a weak negative tendency. All simulations have weaker mean MSE source tendency and significantly weaker cloud-radiative feedbacks. The vertical gross moist stability (VGMS) is used to interpret these MSE budget results in a normalized framework relevant to moisture mode theory. VGMS in the high entrainment runs is far too low compared to ERAi, indicating that it cannot be used in isolation as a measure of model success in producing a realistic MJO hindcast, contrary to previous studies. However, effective VGMS that includes radiative feedbacks is similar among the high entrainment runs and ERAi. We conclude that the MJO is erroneously improved by increasing the entrainment parameter because moistening by vertical MSE advection compensates for the overly weak cloud-radiative feedbacks.

Origins of Moist Air in Global Lagrangian Simulations of the Madden–Julian Oscillation

“…In recent years, one popular way of thinking about the MJO is as a moisture mode [14,21] with many studies seeking to understand its mechanism(s) of moistening and drying [22][23][24]. The moisture mode concept is consistent with the observation that high rain rates are correlated with regions of high column integrated moisture in the tropics in general [25,26].…”

MJO simulation in CMIP5 climate models: MJO skill metrics and process-oriented diagnosis

“…This gap between parameterization development and improving model performance motivated the recent development of the 'process-oriented' MJO simulation diagnostics by the MJOTF and others (Maloney 2009;Kiranmayi and Maloney 2011;Andersen and Kuang 2012;Kim et al 2014Kim et al , 2015Benedict et al 2014;Chikira 2014;Hannah and Maloney 2014;Arnold and Randall 2015;Klingaman et al 2015a, b;Xavier et al 2015;Wolding and Maloney 2015;Wolding et al 2016). These process-oriented diagnostics are designed to characterize resolved-scale processes that are strongly affected by certain aspects of parameterization schemes, and that are relevant to MJO dynamics.…”

Evaluation of the Near Real-Time Forecasts Using a Global Nonhydrostatic Model during the CINDY2011/DYNAMO

“…Modeling studies have also been undertaken with operational forecasts Fu et al 2013;Ling et al 2014;Kerns and Chen 2014a) and global/regional model simulations (Fu et al 2015;Hannah and Maloney 2014;Miyakawa et al 2014;Nasuno 2013;Subramanian and Zhang 2014;Chen et al 2015;Hagos et al 2014a, b;Seo et al 2014;Wang et al 2015). With regard to the moistening process of the MJO, a special focus has been given on multi-scale processes (Chen et al 2015;Hagos et al 2014b;Kerns and Chen 2014a).…”

“…The moisture or moist static energy (MSE) budgets were assessed as a process-oriented diagnosis, in both observational Sobel et al 2014) and modeling (Hannah and Maloney 2014;Seo et al 2014;Subramanian and Zhang 2014;Wang et al 2015) studies. Sobel et al (2014) confirmed that the MSE budgets during the life cycle of the CINDY2011/ DYNAMO MJOs generally agreed with those reported in previous studies.…”