Spontaneous transition to superrotation in warm climates simulated by CAM3" (2010). [1] Recent paleoclimate proxy reconstructions show that tropical surface temperatures may have been as high as 35°–40°C in the Early Cenozoic. Here, we study the tropical atmospheric circulation's response to temperatures in this range using a full‐complexity atmospheric general circulation model (AGCM). We find...

This work is being done in conjunction with other observational and modelling research aimed at improving the representation of the Madden-Julian Oscillation (MJO) in global models. In combines remote sensing and in-situ observations made from the RV-Revell during legs 2 & 3 of the DYNAMO experiement to help characterize vertical transport through the boundary layer and to build statistics of t...

[1] An aquaplanet general circulation model is used to assess the sensitivity of intraseasonal variability to the pattern of sea surface temperature (SST) warming. Three warming patterns are used. Projected SST warming at the end of the 21st century from the Geophysical Fluid Dynamics Laboratory Climate Model 2.1 is one pattern, and zonally symmetric and globally uniform versions of this warmin...

The authors report a significant increase in Madden–Julian oscillation (MJO)–like variability in a superparameterized version of the NCARCommunity AtmosphereModel run with high sea surface temperatures (SSTs). A series of aquaplanet simulations exhibit a tripling of intraseasonal outgoing longwave radiation variance as equatorial SST is increased from 268 to 358C. The simulated intraseasonal va...

We present a statistical analysis of the initiation and termination of boreal winter and boreal summer intraseasonal oscillations (ISOs). This study uses purely convection (infrared brightness temperature) data over a 23-year time interval from 1984–2006. The indices are constructed via the nonlinear Laplacian spectral analysis (NLSA) method and display high intermittency and non-Gaussian stati...

Herewe ask, what controls the horizontal scale of theMadden-Julian Oscillation, i.e., what controls its zonal wave number k?We present a new one-dimensional (1D) β-planemodel that successfully simulates theMJO with the same governing mechanism as the 2D shallow water model of Yang and Ingersoll (2013). Convection is parameterized as a short-duration localized mass source that is triggered when ...

Atmospheric rivers (ARs) account for a large portion of winter precipitation in the western US. To evaluate sources AR and predictability at subseasonal-to-seasonal timescales, we examine relationships between two climate modes, El Niño/Southern Oscillation (ENSO) Madden-Julian oscillation (MJO), hydroclimate Our analysis uses ensemble Weather Research Forecast (WRF) model simulations from 1981...

We investigate in this paper the dominant intraseasonal signals in both convection and circulation data using the nonlinear Laplacian spectral analysis (NLSA) method. Three Madden-Julian oscillation (MJO) indices are constructed based on temporal modes extracted from pure cloudiness, lowerand upper-level zonal wind anomalies. All three indices reveal strong intermittency and capture well – thro...

Abstract: TheMadden-Julian oscillation (MJO) is the dominantmode of variability in the tropical atmosphere on intraseasonal timescales and planetary spatial scales. The skeleton model is a minimal dynamical model that recovers robustly the most fundamental MJO features of (I) a slow eastward speed of roughly 5 ms−1, (II) a peculiar dispersion relation with dω/dk ≈ 0, and (III) a horizontal quad...

A self-contained derivation of the IPESD models [Majda, A.J., Klein, R., 2003. Systematic multi-scale models for the tropics. J. Atmos. Sci. 60, 393–408] governing synoptic and planetary scale tropical flows is provided. This derivation demonstrates the analytic tractability of the model and the effect of zonally and meridionally tilted synoptic scale heating on the forcing of planetary scale f...