Independently assessing the representation of midlatitude cyclones in high-resolution reanalyses using satellite observed winds.

High-resolution reanalyses offer the potential to improve our understanding of midlatitude cyclones, particu- larly smaller-scale systems and those with complex structures. However, previous studies have demonstrated large variations in the frequency and characteristics of Australian midlatitude cyclones between reanalyses when using their native resolution. In this paper we use satellite observations of winds and rainfall in order to evaluate the ability of the ERA-Interim, JRA55, MERRA and CFSR reanalyses to reproduce Australian east coast cyclones. The MERRA reanalysis produces a large number of erroneous small-scale lows without cyclonic wind patterns using a simple pressure-difference-based cyclone identification and tracking method. Consequently, we recommend the ERA-Interim reanalysis when using such methods, or applying more complex tracking methods that are able to compensate for these issues.

Figure 7. Mean wind speeds in (a) MERRA, (b) ERAI and (c) CCMP within 10∘ of the cyclone centre for all ECLs in MERRA where the meridional difference of zonal wind exceeds 5 m s−1 but there is no corresponding cyclone in ERAI within 500 km and 6 h.