The 1st air frost of autumn 2013 occurred briefly for an hour just after 8pm on the 10th November. This was the third latest occurrence of an air frost in autumn since my records began. Previous late air frosts occurred in 2005 (13th Nov) and 2011 (23rd Nov).
Monthly Summary for May 2012 also Spring 2012
After the wet and cold month of April, May 2012 was warmer and drier than average. With a mean temperature of 12.5C, it was 0.7C above the long-term average. There were cold days at the start of the month with maxima of only 8.2C and 9.5C on the 3rd and 4th respectively when the mean maximum is 17.3C. However, several very warm days were enjoyed during the last week when a maximum of 27.6C was recorded on the 23rd and 27th. There was only one minimal air frost when the thermometer briefly dropped to -0.2C on the 16th. A record was set on the 25th when the the highest minimum was noted at 14.7C. The previous high was 13.9C in 1989 and 2001.
Although it was the wettest May for 4 years the total rainfall of 52.4mm was 90% of the long-term average. There were 18 dry days with the wettest being the 7th when 13.7mm was recorded.
The evapotranspiration total was 83.1mm, which meant a net loss to the atmosphere of almost 31mm. Solar energy was 89% of the figure for last year and the total for bright sunshine of 322.7 hours was also down on 2011 with 90% of that figure.
The mean temperature for spring 2012 was 9.3C, which is 0.4C above the long-term average. The total rainfall was 221mm, which was also above the long-term average at 126%.
Dry spring 2011
I have commented in earlier reports on the dry spring. It is well known that in such periods of low rainfall plants set their seed much more quickly. For several years I have kept details of when I plant and harvest my broad beans. The number of days has varied between 92 and 99 days but this year the beans were ready for picking in just 69 days, a significant reduction.
Wind speeds
I recently decided to analyse my records of wind speeds, the most accurate go back to the year 2000 when my anemometer was moved to a very high position, well above roof height. The initial results gave me concern as recent years have shown a decline in wind speed-readings. I had wondered if the repeated attack on the instrument by a rogue rook, two years ago, had damaged the unit.
My equipment captures data every five seconds and from these records I find that there has been a downward trend in average annual wind speeds since 2007 – the fall being most notable for the last two / three years.
|
2001 |
2002 |
2003 |
2004 |
2005 |
2006 |
2007 |
2008 |
2009 |
2010 |
|
4.3 |
4.6 |
4.3 |
4.3 |
4.4 |
4.3 |
4.1 |
3.9 |
3.3 |
3.1 |
Looking specifically at readings in the winter (meteorological) period, December 1st to February 28th, I discovered a reduction in gusts of 20mph +, by an average of four per year. The statistics for gusts of 30mph + produced a reduction of three per year.
‘Aquifer’ rainfall
Analyzing the ‘aquifer’ rainfall, the precipitation which falls between mid October and mid March that percolates down into the sub strata, it has been the fifth wettest period since 1984 with 16% (63mm) above the long-term average. My new equipment enables me to see when evaporation exceeds the moisture that soaks down through the earth and I find that in March, almost 60% of the total rainfall evaporated. There has been an increasing trend in the total aquifer precipitation over the last 27 years in Marlborough, from approximately 375mm in the 1980’s to almost 440mm in the 2000’s.
