Abstract
AbstractIn the present study, global tropical cyclone (TC) formation characteristics are estimated using two fundamentally different Commonwealth Scientific and Industrial Research Organisation (CSIRO) and Okubo‐Weiss zeta parameter (OWZP) tracking schemes in the reanalysis data and in a high‐resolution climate model with interannually varying sea surface temperatures. Both the schemes have a reasonable global geographical distribution of TC genesis locations with under simulation in the eastern North Atlantic and northwestern Australian regions. The mean annual TC frequency in the model is similar to observations using the CSIRO scheme but higher using the OWZP scheme, whereas the annual frequency in reanalysis using the OWZP scheme is similar to observations but halved using the CSIRO scheme. In the CSIRO scheme, both the resolution‐dependent thresholds and large‐scale climate may play a role for skilful TC formation statistics. In contrast, large‐scale climate leads to changes in OWZP TC detections. This highlights the importance of the large‐scale environment for TC detections in both the tracking schemes. The OWZP scheme can differentiate the monsoon lows from the actual TCs in the north Indian Ocean compared to the CSIRO scheme, which incorrectly detects them as TCs in the monsoon season. The distribution of TC lifetime in the model using the OWZP scheme is similar to observations. Conversely, the CSIRO scheme detected TCs have shorter lifetimes, perhaps due to intrinsic tracking scheme differences. Although the tracking schemes are fundamentally different, the study shows that there exist some similarities between them and for certain TC formation characteristics the OWZP scheme performs better compared to the CSIRO scheme.
Highlights
Recent advances in climate models have led to more accurate simulation of the tropical cyclone (TC) climatology, geographical distribution, and seasonal and interannual variability across various regions of the globe (Bell et al, 2013; Camargo & Wing, 2016; Li & Sriver, 2018; Shaevitz et al, 2014; Strachan et al, 2013; Tory et al, 2013b; Walsh et al, 2015; Zhao et al, 2009)
Geographical Distribution of TC Genesis Locations This section illustrates the geographical distribution of the TC genesis locations from IBTrACS and the ACCESS model detected using both Commonwealth Scientific and Industrial Research Organisation (CSIRO) and Okubo‐Weiss zeta parameter (OWZP) TC tracking schemes (Figure 1)
The OWZP detected TCs are more frequent than observations in most of the ocean basins with an undersimulation in the eastern NA and northwestern part of the Australian (AUS) region
Summary
Recent advances in climate models have led to more accurate simulation of the tropical cyclone (TC) climatology, geographical distribution, and seasonal and interannual variability across various regions of the globe (Bell et al, 2013; Camargo & Wing, 2016; Li & Sriver, 2018; Shaevitz et al, 2014; Strachan et al, 2013; Tory et al, 2013b; Walsh et al, 2015; Zhao et al, 2009). It is observed that different climate models produce distinct frequency rates across different ocean basins, and the precise cause for these variations is not clear These earlier studies identified some of the prominent factors that lead to changes in TC formation rates. Based on the pouch concept, in recent studies by Tory et al (2013a), Tory et al (2013b), a TC tracking scheme is developed using ERA‐Interim reanalysis (Dee et al, 2011) that includes a diagnostic term known as the Okubo‐Weiss Zeta parameter (OWZP), coexisting with necessary thermodynamic conditions and dynamic conditions This OWZP represents low‐deformation vorticity regions favorable for TC formation. This study compares the performance of the phenomenon‐based tracking scheme (OWZP) with the traditional scheme (CSIRO) in a fine‐resolution climate model simulation and reanalysis when compared against the observations (IBTrACS, Knapp et al, 2010) in simulating various storm characteristics such as climatology, lifetime, and seasonal and interannual variability. We attempted to examine the performance of the OWZP TC detection scheme in the NI Ocean
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