QBO Modulation of the MJO‐Related Precipitation in East Asia. Issue 4 (16th February 2020)

• Record Type: Journal Article
• Authors: Kim, Hera; Son, Seok‐Woo; Yoo, Changhyun
• Is Part Of: Journal of geophysical research. Volume 125:Issue 4(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-02-16
• Subjects: Madden Julian oscillation -- quasi‐biennial oscillation -- MJO teleconnection -- subseasonal -- East Asia precipitation; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2019JD031929
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: This study revisits precipitation change in East Asia caused by the Madden‐Julian oscillation (MJO) and its interannual variation due to the quasi‐biennial oscillation (QBO). Specifically, boreal‐winter precipitation, derived from weather stations across China, Korea, and Japan, is examined for MJO phases 2–3 and 6–8. Consistent with previous findings, precipitation in southern China and southern Japan increases by up to 36% during MJO phases 2–3, when the MJO convection is located in the Indian Ocean. In contrast, during MJO phases 6–8, precipitation decreases by 13%. More importantly, these MJO‐related precipitation anomalies become larger and more organized when the QBO is in its easterly phase. The difference in precipitation anomalies between the QBO easterly and westerly phases is approximately 40% for MJO phases 2–3 and 70% for MJO phases 6–8 from southern China to Japan. This result reaffirms that the QBO can affect surface weather in the northern extratropics through MJO teleconnection. Plain Language Summary: Deep convections in the tropics influence distant regions via propagation of energy in the form of waves. With its change dominant on the intraseasonal timescale, the Madden‐Julian oscillation (MJO) is known to change daily winter precipitation in East Asia. At the same time, far above in the tropical stratosphere, there is a year‐to‐year variation in zonal wind called the quasi‐biennial oscillation (QBO). It is widely believed that the MJO is stronger and more persistent when the QBO blows from east to west (easterly) than when it blows from west to east. Based on this belief, how MJO‐induced precipitation in East Asia is affected by the QBO is investigated. As expected, the degree of change in precipitation is larger with a stronger MJO amplitude during easterly QBO winters. During easterly QBO winters, MJO‐induced vertical motion near coastlines of East Asia is amplified by stronger upper‐level circulations. Furthermore, moisture transport from the subtropics is also enhanced with the stronger low‐level circulation in easterly QBO winters. In the sense that the QBO has a longer timescale as well as a longer memory than the MJO, we expect to utilize the QBO to predict MJO‐related surface weather changes in the extratropics better and earlier. Key Points: The MJO‐induced precipitation anomaly in East Asia is significantly influenced by QBO phase The MJO teleconnection in East Asia is strengthened during easterly QBO winters, when the MJO amplitude is enhanced The moisture supply to East Asia by MJO‐induced circulation is enhanced during easterly QBO winters