Mapping cold fronts during 35 Southerly Buster events (1994-2020), by using ERA-5 hourly wind shifts during the Australian warm season
Creators: name: Gangoiti, Gotzon
name: Torre-Pascual, Eduardo
name: Rodríguez-García, Ana
name: Sáez de Cámara, Estíbaliz
name: Gómez, María Carmen
name: De Blas, Maite
name: García, José Antonio
name: García-Ruiz, Estíbaliz
name: Zuazo, Iñaki
Publisher: name: Zenodo
Year: 2024
Subjects: thermal low
shallow front
frontogenesis
mesofront
southerly buster

description: DOCUMENT: Mapping cold fronts during 35 Southerly Buster events (1994-2020), by using ERA-5 hourly wind shifts during the Australian warm season 

The Front Identification Scheme (FIS), first developed to track Galernas in the Bay of Biscay, has been adapted to track cold fronts as they progress across the Australian continent. Here, the FIS software is adapted to detect ERA5 reanalysis wind shifts from NW-to-SW with a simultaneous increase in the southerly component (shaded blues in m×s-1), between consecutive wind fields separated by two hours. A threshold of 2 m×s-1 increase of the meridional component is use to plot this type of fronts. In addition, E-to-W wind shifts with a simultaneous increase in the westerly component (shaded reds in m×s-1) are plotted in the same figures using a similar threshold of 2 m×s-1 increase in the zonal component between the same consecutive wind fields.

The method can track with unprecedented temporal and spatial resolution the active life cycle of shallow fronts during the warm season as they move from the west to the east coast of Australia, either over land or over the sea. These shallow fronts, which include Central Australian Fronts, Southerly Busters and Type 2 fronts, form ahead of primary fronts in the Southern Ocean during the warm season, are frequently cloud-free and difficult to detect in the vast Australian territory. They can have a rapid and unexpected evolution and are behind important episodes of devastating bushfires, dust storms, extreme heat or coastal weather extremes, as it is the case of the Southerly Busters of the east coast, a sudden squally wind surge from the south associated with intense turbulence at a hazard for boating and aviation.

Files are grouped both by years and the represented variables: directories named “fronts_xy1000hPa” and “fronts_xy700hPa” stand for fronts at 1000 and 700 hPa respectively and they include maps of hourly wind shifts (red and blue shaded areas) and convergence above the reference value 3×10-5 s−1 (blue contours), and 1000 hPa wind vectors. Directories "g1" stand for Grid 1, which includes maps of the whole Australian continent, while "g2" stand for Grid 2, an area centered on the south-eastern or south-western coast. Directory “mslp_thetaDepth_xy_surf” includes maps of mean sea level pressure (MSLP-1000 hPa in contours, 900-1000 hPa layer depth (m) in shaded colors, and 10-m wind vectors and finally, directory “shear_xy1000-700_converg” includes vertical wind shear (m×s-1) of the 700-1000 hPa winds (shaded colors and vectors) and the net mass convergence (kg×m-2×s-1) into the lower-middle troposphere (1000-500 hPa column) in contours (solid for positive and dashed for negative).