Rain!

Image: Rainbow over “Tir Ceòlmhor” – the Singing Land.

It seems to me that I can’t remember a day in the past month when it hasn’t rained.  What is this – global warming, or global wetting?

Back when Ken and I were considering buying property, I spent some time looking a climate models to see what sorts of changes might be coming in the future.  Using a program called ClimateBC, I looked at predicted changes in the climate by the year 2025, based on 8 climate models (for those who really want to know – CanESM2_RCP26,  CanESM2_RCP45, CanESM2_RCP85,  CNRM-CM5_RCP26,  CNRM-CM5_RCP45, CNRM-CM5_RCP85,  HadGEM2-ES_RCP45, HadGEM2-ES_RCP85), for each of the sites that we were considering.  I averaged the values generated by the 8 models and then compared them with the “normal” climate values (averaged data from 1981 to 2010).  This generated some interesting results.

For our Port Neville site, the following changes were predicted by 2025:

  • mean annual temperature will rise by 1.4°C
  • continentality (e.g., extremes in temperature between hot and cold seasons) will increase by 1.4°C
  • mean annual precipitation will increase by 102.1 mm (5% increase; by comparison, Prince Rupert will have an 8% increase in annual precipitation)
  • frost-free period will increase by 31.4 days!
  • precipitation as snow between August in the previous year and July in the current year will decrease by 22.9 mm (31% decrease)

However, the annual averages don’t really tell the whole story – you need to see how the heat and rain are distributed over the year to get the full picture of the change.

Tmax (°Celsius) Precipitation (% change) Hargreaves climatic moisture deficit (mm)
January 0.5 4 0
February 1.1 12 0
March 1.3 1 0
April 1.6 -12 0
May 1.2 -3 0.5
June 2.0 -5 5.4
July 1.8 4 3.8
August 2.0 -14 12.3
September 1.4 16 0
October 1.2 19 0
November 1.1 -1 0
December 1.1 15 0

What we see here is that while all months will get a bit warmer, the greatest temperature increases occur in June, July, and August.  Rainfall, however, has a much more variable pattern.  April, May, June, and August will get less rain, whereas September, October, December, and February will get much more rain.  The Hargreaves climatic moisture deficit is a measure of how much greater evaporation will be over rainfall.  A positive value for the Hargreaves climatic moisture deficit indicates that the soil is drying out – not a good thing if you are trying to grow a garden without irrigation!  June, July, and especially August will be dry – this could result in more forest fires during that time.

How does this relate to what we have been experiencing so far?

  • June and early July, 2015 – unprecedented dry spell, with 180 fires across the province
  • April 18, 2016  – warm weather records were shattered in Vancouver and 48 other areas of British Columbia due to a high pressure system hovering over the province
  • August 16, 2016 – 17 weather stations across the province had record-breaking temperatures for that date, including many coastal stations
  • October 31, 2016  –  Vancouver and Victoria broke records for the most days of rain in October
  • November 8, 2016 – a Pineapple Express brought record-breaking warm weather to Vancouver and high temperatures for November to much of British Columbia

Are we indeed seeing hotter, drier summers and warmer, wetter winters?  It certainly seems so.

 

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4 thoughts on “Rain!”

  1. Maybe because we live on the water I keep track of changes in wind. Typically November is a very windy month for us on Powell Lake. This year October brought several storms with heavy winds along with heavy rain. This is the beginning of what appears to be a third warm winter in a row. We don’t get much snow, but last year we didn’t see any at all. We’ve been keeping weather logs for the last ten years. I can’t say there’s enough data for a trend, but it seems like things are changing. – Margy

    1. As an oceanographer, I’ve lived by and worked on the water for close to 30 years now. Like you, I can’t say for sure that there is a trend, but what I have observed is an increase in weather variability, severity, and “record-breaking” events over time. While this doesn’t really form a trend – after all, one winter might be colder than normal, the next wetter than normal – I think this increased variability is what we are likely going to see more of with climate change.

      1. Very interesting and some good reading material 🙂 Valerie
        My youngest son lives on Cortez Island so is probably living similar to your way of life to 🙂

        1. Good to hear from you! Ken says its been a long time!
          Let Darren know where we are.
          If your would like to email us, just click on my “blueseas” blog name which will take you to the front page of our website where there is a link to our email address.
          Cheers,
          Barb and Kennard

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