Extreme weather

The Fremantle Doctor – The summer sea-breeze cooling down the area around Perth

The Fremantle doctor is not what the name suggest, a person with a doctorate in medicine, rather it is a sea-breeze in western Australia, where cold fresh air from the Indian ocean typically flows through the west coast of Australia around 4 pm in the afternoon.

Location of Fremantle within Perth

The “Fremantle doctor” name stems from the suburb city harbor located in Fremantle within the city of Perth, see figure below. The saying arose because sailors used to wait for the Fremantle Doctor to take the sail-boats out to sea, utilizing the regular winds blowing over the city side as drift for the sails.

Meteorological Phenomena

The sea-breeze is a meteorological phenomena occurring when cooler air-masses approach the land from the sea providing a cooling sensation on the skin during warm summer days. The Fremantle doctor happens due to the temperature gradients between the cooler seas to the west and warmer Australian land mass to the east.

The above figures are created in order to showcase the temperature variation on a warm summer day. As an example the particular day of Friday 2’nd of December 2022 was chosen.

The figures show 2 m temperature and 10 m wind across the entirety of Australia. The forecasting models are based on meteorological models from ECMWF. The temporal difference between the two figures is 6 hours between 9 am (top) and 3 pm (bottom).

Now compare the above forecast estimates around the city of Perth. First, it can be seen that the 2m temperature and 10 m wind estimates changes during the day. Secondly, in the afternoon by bringing in cooler fresh air from below the southern coast deep into the land. Finally, this sea-breeze bring in relief from the scorching heat brought onto the land by the sun.

Effect of Climate change on the Fremantle Doctor

According to the IPCC report 6 on climate change assessment of Impacts, Adaptation and Vulnerability from 2022. The number of extreme heat temperature events will be occurring at an increasing frequency and will (with high confidence) cause significant changes within the Australasia domain.

Whether the Fremantle Doctor’s cooling effect will increase in a similar manner is hard to say. The need for relief from high temperatures however will remain a constant during the summer months of Australia’s warm climate. Thus, the Fremantle Doctor will continue to bring relief to habitants living in the greater area of Fremantle, Perth.

References – Forecasts for ECMWF and open data available. – IPCC Report 6, assessment of Impacts Adaptation and Vulnerability

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