Tropical cyclones in the GISS ModelE2

Abstract

The authors describe the characteristics of tropical cyclone (TC) activity in the GISS general circulation ModelE2 with a horizontal resolution 18)18. Four model simulations are analysed. In the first, the model is forced with sea surface temperature (SST) from the recent historical climatology. The other three have different idealised climate change simulations, namely (1) a uniform increase of SST by 2 degrees, (2) doubling of the CO 2 concentration and (3) a combination of the two. These simulations were performed as part of the US Climate Variability and Predictability Program Hurricane Working Group. Diagnostics of standard measures of TC activity are computed from the recent historical climatological SST simulation and compared with the same measures computed from observations. The changes in TC activity in the three idealised climate change simulations, by comparison with that in the historical climatological SST simulation, are also described. Similar to previous results in the literature, the changes in TC frequency in the simulation with a doubling CO 2 and an increase in SST are approximately the linear sum of the TC frequency in the other two simulations. However, in contrast with previous results, in these simulations the effects of CO 2 and SST on TC frequency oppose each other. Large-scale environmental variables associated with TC activity are then analysed for the present and future simulations. Model biases in the large-scale fields are identified through a comparison with ERA-Interim reanalysis. Changes in the environmental fields in the future climate simulations are shown and their association with changes in TC activity discussed.

Sensitivity of Tropical Cyclone Formation to Resolution‐Dependent and Independent Tracking Schemes in High‐Resolution Climate Model Simulations

“…The seasonal cycle in the NI Ocean has a bimodal distribution with two observed peaks in the premonsoon and postmonsoon seasons (observations) and is not captured well with CSIRO detection scheme in both the model and reanalysis but captured reasonably well using the OWZP detection scheme. The NI basin is where GCMs with some tracking schemes have difficulty in capturing the seasonal signal due to false alarms of monsoon depressions being identified as TCs during the monsoon season (Murakami, Mizuta, & Shindo, ; Murakami et al, ; Manganello et al, ; Camargo et al, ). The reason could be that monsoon depressions have certain similar characteristics with actual TCs (Murakami et al, ).…”

Western North Pacific Tropical Cyclone Model Tracks in Present and Future Climates

“…A summary of these simulations is given in Table . Many aspects of these simulations have already been examined (Camargo et al, ; Horn et al, ; Patricola et al, ; Scoccimarro et al, ; Shaevitz et al, ; Villarini et al, ; Wehner et al, ), but their focus was not in the WNP TC tracks, as considered here. The HWG models included in our analysis are listed in Table .…”

“…Similar analysis of the HWG multimodel ensemble environmental fields is currently in progress and will be the topic of a future publication. Results from the Goddard Institute for Space Studies (GISS) model show that there is an increase in the potential intensity in the western and central North Pacific for the p2K and p2KCO2 scenarios, accompanied by a decrease of the vertical wind shear and an increase in the tropical cyclone genesis index (Camargo et al, ; Tippett et al, ) in the eastern part of the basin, leading to an expansion of the area that is favorable for TC occurrence poleward and eastward (Camargo et al, , Figures 10, 11, and 13).…”

Western North Pacific Tropical Cyclone Tracks in CMIP5 Models: Statistical Assessment Using a Model-Independent Detection and Tracking Scheme

“…An advantage of direct simulation over the other two methods is that other than limitations inherent in the models and detection algorithm, no additional assumptions are required [see Emanuel (2013) for further reading]. Both fine (;20-50 km) and coarse (;100-300 km) resolution climate models have been used for direct simulation of TCs in the WNP (e.g., Bengtsson et al 2007;Stowasser et al 2007;Sugi et al 2009;Zhao et al 2009;Held and Zhao 2011;Murakami et al 2011;Scoccimarro et al 2011;Murakami et al 2012a,b;Camargo 2013;Mori et al 2013;Strachan et al 2013;Vecchi et al 2013;Vecchi et al 2014;Walsh et al 2013;Yokoi et al 2013;Knutson et al 2015;Murakami et al 2015;Camargo et al 2016;Jin et al 2016;Kossin et al 2016;Tsou et al 2016;Nakamura et al 2017). Although TC intensities are poorly resolved in coarse-resolution models (e.g., Davis 2018), they can have relatively good representations of the large-scale processes that affect TC characteristics such as genesis locations and tracks (e.g., Moise et al 2015;Chand et al 2017), which are the focus of the present study; other projections such as TC rainfall and intensity were not made.…”

“…Kossin et al (2016) and Nakamura et al (2017) included in their analyses CMIP5 TC-like storms obtained by direct simulation to analyze WNP TC frequencies, genesis locations, and tracks, along with downscaled synthetic TCs; in the case of Nakamura et al (2017), TCs from high-resolution simulations were also analyzed. For the CMIP5 model TC-like storms, both these studies utilized the same detection and tracking algorithm of Camargo and Zebiak (2002). Since all detectors have strengths and weaknesses, different detectors can produce very different results when applied to the same model (Horn et al 2014;Tory et al 2014) and so we argue that coarse-resolution simulations for the WNP basin are worth revisiting with a fundamentally different detection methodology.…”