Saturday, 1 April 2017

Carwoola Weather report March 2017

In summary a rather damp month with quite high minimum temperatures but only moderate maximum temperatures. See this article for words from the Canberra Times (although the minimum temperature cited is strange).


After a very dry start to the year March gave good falls.  At Whiskers Creek Rd I recorded 86.0 mm through my weather station (and got agreement from the Nylex several times).  This is the 5th highest total for March since we started recording in 1984.  It is 37mm more than March 2016 and 36mm more than the 32 year average for the month.  
I reported some initial thoughts about March rainfall in a post early in the month.  A key finding in that is that the longer term averages are biased upwards by two very soggy years in which >200mm were recorded.

Another way of looking at the rain is the number of wet days, which I define as a day with greater than 0.2mm of precipitation (to rule out days with a foggy morning which usually give 0.2mm in the weather station).  This year we have had 17 wet days: this equals the most recorded for any month (tying the value for July 1994). 
I put in the trendline out of a spirit of curiosity.  The R2 value shows that there is no significant trend (ie on average, we get pretty even rainfall through the year).


A mild month!
Although March is, under my definition, Autumn there is still a possibility of a heat wave.  The average number of heat wave days in March is close to 2 but in many years - including 2017 - there are none, 

Looking at records back to 1993 this is quite a cool March in terms of maximum temperature, averaging to 24.1oC this year.  This is below below both last year and the long-term average.
For minimum temperatures the value for 2017 (12.8oC) was well up on both 2016 and the long term average.  This has been pretty much a constant in recent months.
For March this can probably be explained by contemplated the cloudiness of the month (as indicated by the number of rainy days).  However it inspired me to check out the longer term pattern of average minimum temperatures for March.  
The R2 value isn't great at 0.55, but deleting the value for 2000 as an outlier gives a trend line of the same general shape but boosts the R2 value to 0.69 which is suggesting a strong relationship.  Even with my constant concern about the brevity of the time series these data suggest that our climate is warming up.


I have often said that I use 40% as a " reasonable" level of humidity.  For March 2017 most of the month was well above that level.  This probably shouldn't be surprising in view of the number of rainy days.
 The monthly average value (59.6%) is well above the average  - which for this variable is only based on 5 years of data.


I am usually wary of the wind data since the anemometer is in a fairly sheltered position.  It also gets beset with spider webs.  I usually clear them out with a finger: this month I was quite lucky doing that as this was the engineer of the web.
Despite the Red-back's best efforts we got wind readings and looking at the average gust over the month it seemed quite high for March.

No comments: