The Madden–Julian oscillation exerts broad influences on global weather and climate as its center of convection moves from the tropical Indian Ocean into the Pacific. Weather events under the influence of the MJO include precipitation, surface temperature, tropical cyclones, tornadoes, flood, wildfire, and lightning, among others. Several climate phenomena are also affected by the MJO. They are the monsoons, El Niño–Southern Oscillation, the North Atlantic Oscillation, the Pacific and North American pattern, the Arctic and Antarctic Oscillations or northern and southern annual modes, the Indian Ocean dipole, the Wyrtki jets, and the Indonesian Through-flow. This article provides a brief summary of the connections between the MJO and these weather and climate phenomena. These connections demonstrate the critical role of the MJO in the weather–climate continuum and its prediction.
The Madden—Julian Oscillation (MJO) has been diagnosed in the World Weather Research Program (WWRP)/World Climate Research Program (WCRP) Sub‐seasonal to Seasonal prediction project (S2S) database using the Wheeler and Hendon index over the common hindcast period 1999—2010. The S2S models display skill to predict the MJO over a period between two and four weeks. The majority of S2S models tend to produce a weaker MJO than in ERA‐Interim, with a phase speed decreasing with lead time. All the S2S models produce realistic patterns of MJO teleconnections at 500 hPa, with an increased probability of positive North Atlantic Oscillation (NAO) following an active MJO over the Indian Ocean and of negative NAO following an active MJO over the West Pacific. However, the amplitude of the MJO teleconnection patterns are significantly weaker than in ERA‐Interim over the Euro‐Atlantic sector and are often too strong over the western North Pacific. Models with lower horizontal resolution tend to produce weaker teleconnections. In the lower stratosphere, several S2S models produce teleconnections which are too strong compared to ERA‐Interim. These results suggest that, although the S2S models display significant skill in predicting the MJO propagation beyond two weeks, all the S2S models do not fully exploit the predictability associated with the MJO in the Northern Extratropics, particularly over Europe. Evolution of the MJO bivariate correlation between the model ensemble means and ERA‐Interim as a function of lead time for ten S2S models. The MJO bivariate correlations have been calculated over the period 1999—2010 for (a) all the seasons and (b) extended winters (December—March). The cyan shaded area represents the 95% level of confidence computed from a 10 000 bootstrap re‐sampling procedure.
The U.S. Climate Variability and Predictability (CLIVAR) MJO Working Group (MJOWG) has taken steps to promote the adoption of a uniform diagnostic and set of skill metrics for analyzing and assessing dynamical forecasts of the MJO. Here we describe the framework and initial implementation of the approach using real-time forecast data from multiple operational numerical weather prediction (NWP) centers. The objectives of this activity are to provide a means to i) quantitatively compare skill of MJO forecasts across operational centers, ii) measure gains in forecast skill over time by a given center and the community as a whole, and iii) facilitate the development of a multimodel forecast of the MJO. The MJO diagnostic is based on extensive deliberations among the MJOWG in conjunction with input from a number of operational centers and makes use of the MJO index of Wheeler and Hendon. This forecast activity has been endorsed by the Working Group on Numerical Experimentation (WGNE), the international body that fosters the development of atmospheric models for NWP and climate studies. The Climate Prediction Center (CPC) within the National Centers for Environmental Prediction (NCEP) is hosting the acquisition of the forecast data, application of the MJO diagnostic, and real-time display of the standardized forecasts. The activity has contributed to the production of 1–2-week operational outlooks at NCEP and activities at other centers. Further enhancements of the diagnostic's implementation, including more extensive analysis, comparison, illustration, and verification of the contributions from the participating centers, will increase the usefulness and application of these forecasts and potentially lead to more skillful predictions of the MJO and indirectly extratropical and other weather variability (e.g., tropical cyclones) influenced by the MJO. The purpose of this article is to inform the larger scientific and operational forecast communities of the MJOWG forecast effort and invite participation from additional operational centers.
An international field campaign aiming at atmospheric and oceanic processes associated with the Madden–Julian oscillation (MJO) was conducted in and around the tropical Indian Ocean during October 2011–March 2012. The objective of the field campaign was to collect observations urgently needed to expedite the progress of understanding the key processes of the MJO, focusing on its convective initiation but also including propagation and maturation, and ultimately to improve skills of numerical simulation and prediction of the MJO. Primary targets of the field campaign included interaction of atmospheric deep convection with its environmental moisture, evolution of cloud populations, and air-sea interaction. Several MJO events were captured by ground-based, airborne, and oceanic instruments with advanced observing technology. Numerical simulations and real-time forecasts were integrated components of the field campaign in its design and operation. Observations collected during the campaign provide unprecedented opportunities to reveal detailed processes of the MJO and to assist evaluation, improvement, and development of weather and climate models. The data policy of the campaign encourages the broad research community to use the field observations to advance the MJO study.