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Observational estimates of Kelvin wave momentum fluxes in the tropical lowerstratosphere remain challenging. Here we extend a method based on linear wavetheory to estimate daily time series of these momentum fluxes fromhigh-resolution radiosonde data. Daily time series are produced for soundingsites operated by the US Department of Energy (DOE) and from the recentDynamics of the Madden–Julian Oscillation (DYNAMO) field campaign. Ourmomentum flux estimates are found to be robust to different data sources andprocessing and in quantitative agreement with estimates from prior studies.Testing the sensitivity to vertical resolution, our estimated momentum fluxesare found to be most sensitive to vertical resolution greater than 1 km,largely due to overestimation of the vertical wavelength. Climatologicalanalysis is performed over a selected 11-year span of data from DOEAtmospheric Radiation Measurement (ARM) radiosonde sites. Analyses of this11-year span of data reveal the expected seasonal cycle of momentum fluxmaxima in boreal winter and minima in boreal summer, and variabilityassociated with the quasi-biennial oscillation of maxima during easterlyphase and minima during westerly phase. Comparison between periods withactive convection that is either strongly or weakly associated with theMadden–Julian Oscillation (MJO) suggests that the MJO provides a nontrivial increase in the lowermost stratospheric momentum fluxes

Intraseasonal to interannual variability of Kelvin wave momentum fluxes as derived from high-resolution radiosonde data