Sept. 29, 2018
The footy is now over and the annual pollen count starts Monday.
Grass pollen is what we're mainly interested in, as it's by far the most common cause of hay fever in Victoria.
So, what's ahead for the grass pollen season?
The first thing to consider is how much rain there's been this year. And if you think it's been pretty a dry year for Victoria, then you'd be right.
One way to assess the likely impact the dry spell has had on the grass pollen season is to look at landscape greenness, a type of data that’s gathered by satellites.
As we move out of winter into spring, the landscape turns from brown to green, a colour change that's visible from space.
In the northern hemisphere this greening is largely due to deciduous forests coming into leaf.
But Australian forests have evergreen trees that don’t lose their leaves every year. Instead, it’s the seasonal growth of grasses that causes our landscape to green.
Today's picture shows the BoM’s NDVI map for August. NDVI is one way landscape greenness is measured.
While the NDVI average map might look pretty green, if you look instead at the NDVI anomaly map a different picture emerges.
The anomaly map shows not so much a map of greenness but of brownness. That’s because landscape greenness in Victoria is well below average for this time of year.
Greenness relates directly to chlorophyll, the pigment plants use to trap light for photosynthesis. And photosynthesis in turn relates directly to plant productivity, the ability of plants to grow by making leaves, flowers and ultimately pollen and seeds.
Simply put, because it’s been a dry year the pasture grasses across western Victoria, the source of much of Melbourne’s grass pollen, are in below average condition coming into the grass pollen season.
That means we’re expecting 2018 will be a lighter than normal grass pollen season.
But that doesn’t mean there won’t be any bad days for hay fever sufferers and asthmatics. It means we’re expecting the 2018 sneezin' season to have fewer bad days and maybe even end a little earlier.
And of course there’s still a risk of thunderstorm asthma, like the event back in November 2016.
So hay fever sufferers should still keep those antihistamines handy.
And asthmatics should remain alert to their asthma symptoms and follow their asthma action plan.
We’ll start counting again across all eight Victorian pollen monitoring sites on October 1. Each day through to December 31 we’ll provide a daily grass pollen count and 7-day forecast for grass pollen.
Counts and forecasts will be available on www.melbournepollen.com.au and are updated daily at around 10:30am.