title	output
Marine Thermal Waves	github_document

Hobday et al (2016) proposed a framework for identify marine thermal waves (mtw). Although the authors focused on marine heat waves, the framework applies to cold waves equally well. Hobday et al (2018) followed up with an additional framework for categorizing the severity of heat waves. Huang et al (2024) deployed a similar framework for study of recent conditions.

Here we replicate Hobday's first framework using Copernicus Global Ocean Physics Reanalysis data and Copernicus Global Ocean Physics Analysis and Forecast data to develop a daily forecast (and hindcast) map for the region covering Cape Hatteras in North Carolina to Newfoundland including the Flemish Cap.

In a nutshell, conditions that identify a heat/cold wave are...

• daily values exceed the 90th percentile of values for the day of year measured over the last 30 years, or

• daily values fall below the 10th percentile of values for the day of year measured over the last 30 years, and

• the event persists for 5 or more days*.

* There is some allowance to merge heat/cold waves that are interrupted by up to 2 days

We count the number of contiguous days above/below the 90th/10th percentile. The map below shows these days where the deeper the colors the longer the duration of the extreme thermal event. It is important to note that these show the pixels that are exceed or fall below the 90th (red) or 10th (blue) percentile for extended periods of time.