Long term rain and temperatures

The objective of this post is to report on a couple of interesting findings about longer term aspects of the weather in Mallacoota.  In summary:

• there has been a decreasing amount of rainfall for the last 5 years and the trend may not yet have turned.; and
• there is little change in the average daily maximum and minimum temperatures across the month of March. 

Long Term Rain

When looking at the weather for Carwoola I found that taking a long term view demonstrated the depth of the current drought rather well.  So I decided to take the same approach for Mallacoota, using BoM data.

My starting point was a 12 month rolling total which blocks any seasonal patterns.

I couldn't pick a significant trend in the overall series but did note the downwards slide towards the end!  The mean 12 months rainfall is 936 mm and the median is 917 mm.  It is a bit hard to  work out the value of the mode but looking at a bar chart of major size classes ...

... suggests that it would fall at around 900mm.  That grouping of averages suggests that the values are not too far off a normal distribution

I then extended the rolling periods to 18 months and 24 months, giving the following chart.

In each case there is a rather consistent downwards look to the last 5 years, so I charted that separately.  The values of R² confirm a significant downward slope.

While the 24 month series ends with an uptick it is probably too soon to say the drought is broken.

Long term average March Temperature extremes

To support some thoughts about temperatures for this month I calculated the average monthly maxima and minima by day using BoM data since 1994.

I was impressed by how flat the graph was, as I was expecting a pronounced downwards trend though the month.  With an R² of 0.39 I don't think the value for maximum is significant and even that for minima ( 0.60) is anything to get excited over.