Paul E. Roundy

How regional SST shapes Saharan Near-Surface Temperature: Sensitivity and Dynamical Mechanisms

Zhuo Li, Brian E. J. Rose, Paul E. Roundy, Bosong Zhang

Abstract The Sahara Desert has undergone substantial near-surface warming during the boreal warm season (June–November) in recent decades. Previous studies have suggested that historical and future Saharan warming is largely controlled by sea surface temperature (SST) changes. Here, we assess the sensitivity …

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The Role of Stratosphere–Troposphere Vertical Shear of the Zonal Wind in the QBO-MJO Relationship

Paul E. Roundy

Vertical shear of the zonal wind across the equatorial tropopause over the Indian Ocean to the Maritime Continent is caused by a combination of the quasi-biennial oscillation (QBO) of the stratosphere and the seasonal cycle and interannual variability of the upper troposphere. …

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Propagation Speed Climatology of Pacific Equatorial Kelvin Waves in Different Background Conditions

Crizzia Mielle De Castro, Paul E. Roundy

Atmospheric equatorial Kelvin waves—convective disturbances that manipulate tropical wind and rainfall patterns—can propagate eastward at speeds ranging from nearly stationary to 30 m/s, with variability determined by moist processes and advection by the background wind. Current studies on Kelvin waves lack a …

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Zonal Propagation of the Indian Basin MJO Across Varying Background Wind and Seasonal Background Wind States

Paul E. Roundy

The Madden–Julian Oscillation (MJO) varies seasonally. Both moist and dry dynamical processes would contribute to this seasonality. Previous results have suggested strong dependence of MJO phase speed on planetary-scale upper tropospheric Kelvin waves interacting with the mean flow. Composites and phase speed …

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Feedback Cycle between Synoptic Kelvin Waves and the Madden–Julian Oscillation through Nonlinear Advection

Crizzia Mielle De Castro, Paul E. Roundy

Abstract This work hypothesizes that the Madden–Julian oscillation (MJO) alters the vertical structure of synoptic convectively coupled Kelvin waves in a manner that allows nonlinear advection by the altered Kelvin waves to feed back onto the MJO. Through wavelet decomposition and linear …

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Planetary Scale Kelvin Wave Propagation from the Stratosphere as a Potential Explanation of the Association between the MJO and the QBO

Paul E. Roundy

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The Equatorial Upper-Tropospheric MJO Signal Is Created by Kelvin Wave Dynamics Interacting with the Mean Flow

Paul E. Roundy

Abstract Fields of equatorial upper-tropospheric circulation data are lag regressed against wavelet-filtered indices of upper-tropospheric zonal wind anomalies over a range of phase speeds at 50-day periods to study the propagation mechanisms of the upper-tropospheric circulation signal of the Madden–Julian oscillation (MJO) …

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How the GEFS forecast model represents the dry dynamical component of the maritime continent barrier effect on the MJO

Paul E. Roundy

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How Temperature Trends Vary with Specific Humidity in the Tropical Lower Troposphere in ERA5

Paul E. Roundy

Abstract The rate of change of temperature during 1979–2020 is assessed as a continuous function of specific humidity for the tropical lower troposphere using ERA5 reanalysis data and a modulation regression technique. Statistical stability is assessed through a Monte Carlo experiment and …

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Multi-time scale analysis of the water level minima in Lake Titicaca over the past 103 years

Juan Sulca, Mathias Vuille, Ken I. Takahashi, Paul E. Roundy et autres

Lowest events in Lake Titicaca’s water level (LTWL) significantly impact local ecosystems and the drinking water supply in Peru and Bolivia. However, the hydroclimatic mechanisms driving extreme lake-level lowstands remain poorly understood. To investigate these low lake-level events, we analyzed detrended monthly …

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On the MJO Phase Speed among Different Background Moisture and Zonal Wind Base States

Ahmed A. Shaaban, Paul E. Roundy

Abstract The variability of the phase speed of the Madden–Julian oscillation (MJO) is poorly understood. The authors assess how the phase speed of the convective signal of the MJO associates with the background states over eastern Africa and the Indian Ocean. Relaxation …

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Role of Dry Dynamics in the Maritime Continent Barrier Effect in the Madden–Julian Oscillation

Paul E. Roundy

Abstract Eastward-moving moist deep convection and atmospheric circulation signals associated with the tropical Madden–Julian oscillation (MJO) sometimes break down as they cross the Maritime Continent region, but other times, the signal propagates across the region maintaining amplitude or regaining it over the …

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