Large-Scale Environmental Characteristics of MJOs that Strengthen and Weaken over the Maritime Continent
- Pacific Northwest National Laboratory, Richland, Washington
- University of Washington, Seattle, Washington
The characteristics of Madden-Julian Oscillation (MJO) events that strengthen and weaken over the Maritime Continent (MC) are examined using long-term satellite observations and reanalysis datasets. The MJO weakens twice as often as it strengthens over the MC, with weakening MJOs being twice as likely during El Niño years compared to La Niña years and the reverse being true for MJO strengthening events. Weakening MJOs are characterized by large positive sea-surface temperature (SST) and moist-static energy (MSE) anomalies in the southern hemisphere (SH) of the MC compared to MJO strengthening events. These anomalies correspond to more precipitation and stronger upper-level divergence in the SH compared to the NH. The north-south polarity in these variables reflects the seasonal cycle in MJO weakening over the MC. MJOs that approach the MC during the NH winter typically weaken. There is a window during the NH summer and fall in which the MJO almost always strengthens over the MC. This seasonal cycle corresponds to whether the MJO crosses the MC primarily north or south of the equator. The MJO encounters more and taller MC islands when crossing in the SH, which previous results suggest is the likely cause of the frequent weakening. The finding of a seasonal cycle in MJO weakening over the MC complements and extends previous work on the topic and highlights the importance of sampling MJOs throughout the year in future field campaigns designed to study MJO-MC interactions.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Biological and Environmental Research (BER)
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1488447
- Report Number(s):
- PNNL-SA-128529
- Journal Information:
- Journal of Climate, Vol. 31, Issue 14; ISSN 0894-8755
- Publisher:
- American Meteorological Society
- Country of Publication:
- United States
- Language:
- English
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