edu.ucar.opensky::articles:23936 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-25T06:39:20.040468 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d73x89zp Role of equatorial waves and convective gravity waves in the 2015/16 quasi-biennial oscillation disruption 2020-12-02T00:00:00Z publication https://n2t.org/ark:/85065/d73x89zp https://doi.org/10.5194/acp-20-14669-2020 Kang, M. author Chun, H. author García, Rolando R. author UCAR/NCAR - Library publisher In February 2016, the descent of the westerly phase of the quasi-biennial oscillation (QBO) was unprecedentedly disrupted by the development of easterly winds. Previous studies have shown that extratropical Rossby waves propagating into the deep tropics were the major cause of the 2015/16 QBO disruption. However, a large portion of the negative momentum forcing associated with the disruption still stems from equatorial planetary and small-scale gravity waves, which calls for detailed analyses by separating each wave mode compared with climatological QBO cases. Here, the contributions of resolved equatorial planetary waves (Kelvin, Rossby, mixed Rossby-gravity (MRG), and inertia-gravity (IG) waves) and small-scale convective gravity waves (CGWs) obtained from an offline CGW parameterization to the 2015/16 QBO disruption are investigated using MERRA-2 global reanalysis data from October 2015 to February 2016. In October and November 2015, anomalously strong negative forcing by MRG and IG waves weakened the QBO jet at 0-5 degrees S near 40 hPa, leading to Rossby wave breaking at the QBO jet core in the Southern Hemisphere. From December 2015 to January 2016, exceptionally strong Rossby waves propagating horizontally (vertically) continuously decelerated the southern (northern) flank of the jet. In February 2016, when the westward CGW momentum flux at the source level was much stronger than its climatology, CGWs began to exert considerable negative forcing at 40-50 hPa near the Equator, in addition to the Rossby waves. The enhancement of the negative wave forcing in the tropics stems mostly from strong wave activity in the troposphere associated with increased convective activity and the strong westerlies (or weaker easterlies) in the troposphere, except that the MRG wave forcing is more likely associated with increased barotropic instability in the lower stratosphere. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication Copyright author(s). This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. None eng geoscientificInformation