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Atmospheric methane (CH 4) is considered to be one of the most important greenhouse gases due to its increasing atmospheric concentrations and the fact that it has a warming potential 28 times that of atmospheric carbon dioxide (CO 2). Over the Indian sub-continent, fluxes and transport both contribute towards CH 4 seasonal variability. Its intra-seasonal variability however is more complex as it is additionally influenced by monsoonal activity during the Asian Summer Monsoon (ASM) period. In this study, the intra-seasonal variability of atmospheric CH 4 is examined using ground-based observations at two sites located in the Southern Indian Peninsula, Sinhagad (SNG) and Cape Rama (CRI); and outputs from three different model simulations. Both, the ground based observations and multi-model simulations show that the dominant spectral variability of CH 4 is coherent with 20–90 day oscillations in the dynamics of the monsoon (termed hereafter as Intra-Seasonal Oscillations, ISOs). The multi-model analysis revealed that CH 4 is heavily influenced by advection due to this intra-seasonal variability. The simulations also display a clear northward propagation of CH 4 anomalies over India. The co-evolution of CH 4 , outgoing long wave radiation (to represent convection) and OH radicals (proxy to CH 4 sinks) is presented. The study quantifies CH 4 variability at intra-seasonal timescales and also its spatial extent. The results suggest that the effect of ISOs on CH 4 needs to be considered along with the corresponding observations for future inverse modeling. Image 1 Composite analysis shows a clear northward propagation of atmospheric CH 4 concentration anomalies with amplitude of ±10 ppb and at a speed of approximately 1.5° latitude per day. On the day when the active spell commences (i.e. at zero on the time axis), the CH 4 concentrations switches from positive to negative at surface, middle and upper troposphere. This is visible in three different model outputs analyzed here although with some differences from model to model.Figure: Active-break composite evolution of atmospheric CH4 anomalies (ppb) over India, as simulated by models LMDz (upper left panel), ACTM (upper right panel), and CAM-Chem (lower panel). The data was averaged from 55 °E to 110 °E and is shown from the equator to 30 °N. • Surface CH 4 observations in India show coherence of 30–90 day oscillations. • Advected CH 4 signal shows clear northward propagation of anomalies during JJAS. • The co-evolutions of CH 4 , OLR, and OH radicals are presented for the JJAS period. [ABSTRACT FROM AUTHOR]