ERA5 OLR Spectral Filtering of Tropical Waves (Kelvin, MRG, TEWs, MJO) for Northern South America

To investigate the main tropical atmospheric phenomena influencing precipitation variability over northern South America (NSA), wavenumber–frequency power spectra of outgoing longwave radiation (OLR) from ERA5 were computed. The approach followed Wheeler and Kiladis (1999), combined with the regional tapering technique of Dias et al. (2013). The analysis domain was defined as the longitudinal sector from 160° W to 20° E, centered over the NSA region. To reduce intraseasonal noise and obtain a smooth distribution of synoptic-scale variability, 64-day window segments with a 13-day overlap were used, applying a Hann window. The ERA5 OLR fields were then filtered using inverse Fourier transforms, retaining only the spectral variability within the wavenumber–frequency ranges corresponding to Kelvin waves (KW), mixed Rossby–gravity waves (MRG), tropical easterly waves (TEWs), and the Madden–Julian Oscillation (MJO), following Wheeler and Kiladis (1999) and Kiladis et al. (2009). The resulting dataset contains filtered OLR time series associated with these tropical disturbances over northern South America. These series provide the basis for analyzing convectively coupled equatorial waves and their influence on precipitation variability. Further methodological details and applications of these data can be found in Builes-Jaramillo et al. (2025). References Wheeler, M., & Kiladis, G. N. (1999). Convectively coupled equatorial waves: Analysis of clouds and temperature in the wavenumber–frequency domain. Journal of the Atmospheric Sciences, 56(3), 374–399. https://doi.org/10.1175/1520-0469(1999)056<0374:CCEWAO>2.0.CO;2 Kiladis, G. N., Wheeler, M. C., Haertel, P. T., Straub, K. H., & Roundy, P. E. (2009). Convectively coupled equatorial waves. Reviews of Geophysics, 47, RG2003. https://doi.org/10.1029/2008RG000266 Dias, J., Leroux, S., Tulich, S. N., & Kiladis, G. N. (2013). How systematically organized is tropical convection within the MJO? Geophysical Research Letters, 40, 1420–1425. https://doi.org/10.1002/grl.50308 Huaman, L., Schumacher, C., & Kiladis, G. N. (2020). Eastward-propagating disturbances in the tropical Pacific. Monthly Weather Review, 148(9), 3713–3728. https://doi.org/10.1175/MWR-D-20-0029.1 Builes-Jaramillo, A., Yepes, J., Salas, H. D., Bedoya-Soto, J. M., Rivera, P., Valencia, J., & Carmona, A. M. (2025). Intraseasonal oscillations and hydroclimate of northern South America, Central America and Mexico. International Journal of Climatology, 45, e8848. https://doi.org/10.1002/joc.8848