jbkajtar/mhw_australia

Code for generating Australian marine heatwave (MHW) metrics from observational data. Generated for Kajtar et al. (2021).

Australian marine heatwave data (mhw_australia)

Code for generating marine heatwave (MHW) metrics from observational data for: Kajtar, J.B., N.J. Holbrook, V. Hernaman, A catalogue of marine heatwave metrics and trends for the Australian region. J. South. Hemisph. Earth Syst. Sci., 71 (2021) 284–302. https://doi.org/10.1071/ES21014.

Marine heatwaves are calculated following the Hobday et al. (2016) definition, using the marineHeatWaves python module (https://github.com/ecjoliver/marineHeatWaves). Marine heatwave categories follow the definition given by Hobday et al. (2018).

This code has been written to generate MHW metrics for the marine region around Australia (100°E-170°E, 50°S-0°). The metrics are computed from daily observational sea surface temperature (SST) data, using NOAA 0.25° daily Optimum Interpolation Sea Surface Temperature (OISST) over the period 1982-2020. Marine heatwaves are computed with respect to the 1983-2012 climatology. The marine heatwave data are provided on a grid point basis across the domain. Area-averaged SST timeseries and marine heatwave metrics are also provided for five case study regions: the Western Australia coast, Torres Strait, Great Barrier Reef, Tasman Sea, and South Australian Basin.

Contents

Directory	Description
code	Code for computing MHW metrics
marineHeatWaves	Customised MHW detection code
post-processing	Code for post-processing data
data	Output and source data

code

Python code for computing MHW metrics. Data source paths must first be specified in each of the scripts. The raw observed daily sea surface temperature data (NOAA OISST) is not provided here, but more information about the data and how to access can be found at: https://doi.org/10.25921/RE9P-PT57.

File	Description
compute_australian_mhw_stats.py	Compute MHW metrics across the Australian region.
store_aus_case_study_regions.py	Store area-averaged SST timeseries, for further processing.
plot_fig_case_studies.py	Processing and plotting of case study region MHW metrics. Code for generating Figs. 5-9.

marineHeatWaves

Marine heatwaves detection code, available at: https://github.com/ecjoliver/marineHeatWaves. The code provided here has been slightly adapted, but the original module should also work.

post-processing

MATLAB code for post-processing of MHW metrics.

File	Description
area_average.m	Function to compute an area-average
area_make.m	Function to compute a cell area array, used in area_average.m
findrange.m	Function to find a range in an array
pp_mhw_stats.m	Post-processing of MHW field data
pp_mhw_strongest.m	Post-processing of strongest and longest detected MHWs

data

Various source and output data produced by the code.

File	Description
oni.data.txt	Observed Oceanic Nino Index (ONI) data, provided by NOAA/PSL
sst_ts.aus.NOAA_OISST.AVHRR.v2-1_modified.nc	Area-averaged daily SST timeseries for case study regions
mhw_cats.aus.NOAA_OISST.AVHRR.v2-1_modified.nc	MHW metrics: annual field data
mhw_stats.processed.aus.NOAA_OISST.AVHRR.v2-1_modified.nc	MHW metrics: post-processed data for producing figures
mhw_strongest.processed.aus.NOAA_OISST.AVHRR.v2-1_modified.nc	MHW metrics: post-processed data of the strongest and longest MHWs

References

Hobday, A.J., L. V. Alexander, S.E. Perkins-Kirkpatrick, D.A. Smale, S.C. Straub, E.C.J. Oliver, J.A. Benthuysen, M.T. Burrows, M.G. Donat, M. Feng, N.J. Holbrook, P.J. Moore, H.A. Scannell, A. Sen Gupta, T. Wernberg, A hierarchical approach to defining marine heatwaves, Prog. Oceanogr. 141 (2016) 227–238. https://doi.org/10.1016/j.pocean.2015.12.014.

Hobday, A.J., E.C.J. Oliver, A. Sen Gupta, J.A. Benthuysen, M.T. Burrows, M.G. Donat, N.J. Holbrook, P.J. Moore, M.S. Thomsen, T. Wernberg, D.A. Smale, Categorizing and naming marine heatwaves, Oceanography. 31 (2018) 162–173. https://doi.org/10.5670/oceanog.2018.205.

Kajtar, J.B., N.J. Holbrook, V. Hernaman, A catalogue of marine heatwave metrics and trends for the Australian region. J. South. Hemisph. Earth Syst. Sci., 71 (2021) 284–302. https://doi.org/10.1071/ES21014.

Acknowledgements

We acknowledge support from the Australian Government’s National Environmental Science Program (NESP) Earth Systems and Climate Change (ESCC) Hub, and the Australian Research Council’s Centre of Excellence for Climate Extremes. The research was conducted under ESCC Hub Project 5.8: ‘Marine and coastal climate services for extremes’. We acknowledge the input and support of project leader Kathleen L. McInnes and the whole Project 5.8 team. JBK and NJH acknowledge further support from the NESP Phase 2 Climate Systems Hub.

NOAA High Resolution SST data were provided by the NOAA National Centers for Environmental Information. We thank them for making this data publicly available. We acknowledge the compuational resources provided by the National Computational Infrastructure (NCI), which is supported by the Australian Government. We acknowledge Eric Oliver for the use of his marineHeatWaves python module, freely available at https://github.com/ecjoliver/marineHeatWaves.