Premium
The Role of Vorticity Tilting in Northward‐Propagating Monsoon Intraseasonal Oscillation
Author(s) -
Li Baosheng,
Zhou Lei,
Qin Jianhuang,
Murtugudde Raghu
Publication year - 2021
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2021gl093304
Subject(s) - climatology , vorticity , monsoon , convection , geology , oscillation (cell signaling) , potential vorticity , zonal and meridional , madden–julian oscillation , wind shear , atmospheric sciences , climate model , geophysics , meteorology , physics , climate change , vortex , wind speed , oceanography , biology , genetics
The simulation of the northward‐propagating monsoon intraseasonal oscillation (MISO) is still a grand challenge for climate models. Here, we show that the tilting of vorticity plays a critical role in the northward‐propagating MISO. During the Indian summer monsoon (ISM), the persistent vertical easterly shear of background zonal wind sets up a horizontal vorticity. Due to the meridional gradient of vertical velocity associated with convection, positive vorticity anomalies are generated to the north of the convection, where the convection is enhanced. In 19 coupled general circulation models from Phase 6 of the Coupled Model Intercomparison Project (CMIP6), it is confirmed that the simulations of MISO have a strong dependence on the simulations of this tilting but the tilting structures are not well‐captured in CMIP6 models. This offers a specific target for alleviating the model bias in MISO as well as in ISM in contemporary climate models.