Intraseasonal Variability in an Aquaplanet General Circulation Model
By E. Maloney, A. Sobel, W. Hannah. 2010
137 citations recorded by the source corpus.
An aquaplanet atmospheric general circulation model simulation with a robust intraseasonal oscillation is analyzed. The SST boundary condition resembles the observed December‐April average with continents omitted, although with the meridional SST gradient reduced to be one‐quarter of that observed poleward of 10° latitude. Slow, regular eastward propagation at 5 m s−1 in winds and precipitation with amplitude greater than that in the observed MJO is clearly identified in unfiltered fields. Local precipitation rate is a strongly non‐linear and increasing function of column precipitable water, as in observations. The model intraseasonal oscillation resembles a moisture mode that is destabilized by wind‐evaporation feedback, and that propagates eastward through advection of anomalous humidity by the sum of perturbation winds and mean westerly flow. A series of sensitivity experiments are conducted to test hypothesized mechanisms. A mechanism denial experiment in which intraseasonal latent heat flux variability is removed largely eliminates intraseasonal wind and precipitation variability. Reducing the lower‐troposphere westerly flow in the warm pool by reducing the zonal SST gradient slows eastward propagation, supporting the importance of horizontal advection by the low‐level wind to eastward propagation. A zonally symmetric SST basic state produces weak and unrealistic intraseasonal variability between 30 and 90 day timescales, indicating the importance of mean low‐level westerly winds and hence a realistic phase relationship between precipitation and surface flux anomalies for producing realistic tropical intraseasonal variability.
Subfields: Atmospheric Science, Global and Planetary Change, Oceanography
View Paper: https://www.semanticscholar.org/paper/4ae7a25b476bbbe16cac598081f4a287639b0c04
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Citations in the corpus
- An Idealized Semi-Empirical Framework for Modeling the Madden–Julian Oscillation (2012, methodology): “…has been shown to be greatest in the lower free troposphere in observations (Benedict and Randall 2007) and simulations (e.g., Maloney 2009; Maloney et al. 2010), but the zonal wind tends to change sign with height in MJO events while the moisture gradient generally does Unauthenticated |…”
- Fifty Years of Research on the Madden‐Julian Oscillation: Recent Progress, Challenges, and Perspectives (2020, background): “…west, thus promoting the eastward propagation of the MJO (e.g., Arnold et al., 2015; Adames & Wallace, 2015; Andersen & Kuang, 2012; Chikira, 2014; Gonzalez & Jiang, 2019; Jiang, 2017; Jiang, Maloney, & Su, 2020; D. Kim, Kug, et al., 2014; Maloney, 2009; Maloney et al., 2010; Sobel et al., 2014).”