Dry Air in Winter 2017

Photo of red Eucalyptus flowers

Eucalyptus leucoxylon in winter

This winter had remarkably dry air. The lowest early morning dew point was -10.0°, and the winter mean was -0.5°. Both were record low values. Through the season, the dew point got further and further below the early morning temperature, ending five degrees lower.

Daily maximum and minimum temperatures were near normal. However, they were more than a degree cooler than in the recent winters of 2009 and 2013.

Graphical log for winter 2017

With dry air came a wide daily temperature range of 16.3°, second only to 17.5° in the winter of 2002. It also brought sunny weather, with only 32% cloudy mornings. While that was near the average for my “normal” decade 1999-2008, it was lower than in any recent winter. The winters of the last decade, 2007-2016, were much more cloudy, averaging 45% cloudy mornings. Winter 2016 had 53%!

There were four brief spells of rain this winter, none with heavy rain. They were spaced about seventeen days apart. That sequence had begun in autumn, with heavier falls then. After the 4th of August there was no rain at all.

The total rainfall of 89.8 mm was at the 27th percentile, well below the winter average of 125 mm. Five recent winters had similar amounts of rain: 2000 (98 mm), 2001 (107 mm), 2003 (102 mm), 2004 (97 mm) and 2006 (104 mm). Two were much drier: 2002 (44 mm) and 2011 (55 mm).

Climate for winter 2017


Data. A Bureau of Meteorology automatic rain gauge operates in the museum yard. From 17 March 2017, 9 am daily readings are published as Manilla Museum, Station 55312.  These reports use that rainfall data when it is available. All other data, including subsoil at 750 mm, are from 3 Monash Street, Manilla.

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Hard Winter for Solar-passive

Graphical log of daily indoor and outdoor temperatures for winter 2016.

Temperature log: main features

This graph, for 2016, shows a winter pattern of indoor and outdoor temperatures that is typical for this house. Indoor temperatures vary much less than outdoor temperatures, they rise and fall with them, and they are higher nearly all the time.
While the outdoor temperatures shown go as low as minus three degrees, those indoors lie within the winter “comfort zone” from 17 to 24 degrees (see this post) nearly all the time.

Weather this winter

This winter was harsh for a solar-passive house. Near-record rainfall (227 mm) came with the greatest number of cloudy days of any winter in the new century. There were 53 mornings with more than four octas of cloud, when the average is 33.

Heater use

Because cloud limited the the solar gain, I had to use blower heaters far more than in previous winters. My records show that I used 320 kWh ($80) in these heaters this winter, when I normally use about 40 kWh ($10).
Heaters were also used by guests who were present on the six days shown. As well as being unused to the climate, the guests lived in the colder west wing of the house. They may have used 72 kWh ($18). Those guests have kindly written reviews of their visit.
Even using 400 kWh of electricity for personal heating in a winter could not make a detectable change in house temperature. I have found that blower heaters are surprisingly good at making a room in this house comfortable. As the radiant temperature of the walls is only 2 or 3 degrees too low for comfort, it can be compensated by making the air temperature only slightly higher.

The pattern in detail

While cloudy days are not plotted here (Cloud observations for this winter are plotted elsewhere.), cloudy days can be recognised on the graph. In this climate, days with low maximum temperature and high minimum temperature are always due to cloud. Only in fine weather are days warm and nights frosty. The graph shows how the weather goes through a cycle every week or two: sunny days get warmer, then rain sets in. As it clears, the air gets even colder, before warming up again.
Indoor temperatures follow the same cycle, but there are differences. There may be a delay of up to a day, and sometimes longer.

Correlations

I did scatter plots comparing all the variables shown in the first graph and I fitted linear regressions. I present the four scatter-plots that had the highest coefficients of determination (“R-squared”). Continue reading

Extremely wet winter 2016

Water flowing over a weir

Manilla Weir Fish Ladder

This winter, with 227.4 mm of rain, was the fifth wettest in the record from 1883. In order of rainfall, wetter winters were: 1920 (318 mm), 1998 (304 mm), 1950 (261 mm) and 1952 (233 mm). This winter’s total was more than 100 mm over the average (125 mm). The heaviest daily fall, 37 mm, was on 5 June, and there were four other falls of more than 15 mm; two in June and two in August.
There were big week-long swings in temperature through June and July. On four occasions nights were more than four degrees warmer than normal and on one occasion days were four degrees cooler than normal. No such swings occurred from late July to mid-August, then days became five degrees cooler than normal. In this winter, there were few spells of either hot days or cold nights. The number of frosts (42) was near the usual number (44).

Graphical log for winter 2016
While the mean temperature of the season was normal, most other measures of climate were not.
The winter seasons of 2016 and 2010 were both extremely moist. Winter 2016 had more rain (227 mm versus 160 mm) and more cloudy days (53% versus 49%). In other respects 2010 was more moist: the dew point was higher (3.7° versus 2.5°), and the days had a narrower temperature range (12.5° versus 12.8°). The daily temperature range for winter is usually much wider: 15.3°. It was 17.5° in winter 2002!

Climate for winter 2016


Rainfall figures for this month are from the automatic rain gauge at Manilla, published on the internet by the Bureau of Meteorology as Station 55031. All other data, including subsoil at 750 mm, are from 3 Monash Street, Manilla.

Winter 2015 like winter 2014

A low-level lenticular cloud

Low Level Lennie

Weather log for winter 2014There was one short spell of rather cold days in mid-July this year, and another at the very end of August.
Otherwise, this winter was very like the winter before. In mid-June and late August there were humid spells with heavy rain and very warm nights. By contrast, early August had cold nights with very low humidity and no rain. In both years, July had very light falls of rain.
The number of frosts in each season (38; 42) was near normal (44), but in this winter the coldest night (minus 2.1°) was the warmest so far this century.

Weather log for winter 2015

Like last winter, the average night temperature and the cloudiness were a little high, and the dew point very low. Average day temperature was half a degree low, making the daily temperature range narrow.
The winter rainfall, 133 mm, was just above the average (125 mm) and in the 62nd percentile.

Climate for winter 2015


 Temperature, including subsoil at 750 mm, and other data are from 3 Monash Street, Manilla.

Manilla’s Frosts to 2014

Graphical log of frosts

This post updates a similar one by including three more years to make a total of sixteen.

The Number of Frosts in Each Year

The first graph is a log of the number of frosts in each year. The pattern is different when counting all frosts or only severe frosts.
The log for all frosts had two periods of stable, medium numbers of frosts: from 1999 to 2003, and from 2008 to 2011. Three years had many frosts: 2004 (68), 2006 (70), and 2012 (69). The year 2007 had the fewest frosts (43) until beaten by 2013 (34).
In the logs for severe frosts below minus 2° or minus 4° in the thermometer screen, the drought year 2002 stands out as the most frosty by far. It had the coldest mornings: -5.1° on both the 2nd and 11th of July.

The Last Three Years

Monthly frosts in 2012, 2013, and 2014.

The second graph compares the mean seasonal pattern of frosts with the patterns for the three latest years: 2012, 2013, and 2014.
The frost season of 2012, which almost matched the record 70 frosts of 2006, began early and ended late. May had 13 frosts (like the 14 of 2006) and September had 10 (like the 8 of 2003).
The curve for the season of 2013 ( the new record fewest) was like that of a normal frost season, but lower.
The year 2014 was not very frosty, because the season began late, with no frosts in May and only nine in June.

Monthly frosts each year

Graphs showing the seasonal frost patterns for earlier years are copied here.

 

 

 

 

 

 


There is 2013 reserch on frost in NSW titled “Understanding frost risk in a variable and changing climate” reported here.
It is in GRDC Update Papers (Grains Research and development Corporation). The research is done by Steven Crimp and co-workers at CSIRO Climate Adaption Flagship.
Referring to the period 1960 to 2010,
“Over many parts of NSW the frost season length has broadened by as much as 40 days and the mean number of consecutive frost days has increased to 5 days.”

Winter 2014 normal

Berries on a melia tree

Chinaberries in winter

This winter, there were no very warm or very cold spells. There was one sunny spell with a wide daily temperature range in early August, followed by a week with a narrow temperature range.
There were 38 frosts. While this is below the 16-year winter average of 44, it is near the average for the last seven winters. From 2001 to 2006 the winter average was higher: 47 frosts.
Rain fell on 15 days (normal), with a highest reading of 26.6 mm, which is also normal in winter.Weather log for winter 2014

Seasonal means and totals were all not far from normal except for the dew point. The dew point of 0.7 degrees was more than two degrees low, showing extremely dry air, as in winter 2012. The daily minimum temperature was almost a degree high, reducing the temperature range and raising the mean temperature as well.

The winter rainfall total of 106 mm is just below the average (125 mm) and in the 40th percentile.

Climate for winter 2014


Data. Rainfall data is from Manilla Post Office, courtesy of Phil Pinch. Temperature, including subsoil at 750 mm, and other data are from 3 Monash Street, Manilla.

Winter 2013 Warm

Weather log winter 2013

This winter, June was very cloudy and wet, July was very warm, and August was warm and dry. This pattern was common across northern NSW.
There were only 29 frosts, well below the winter average of 44, and fewer than in winter 2010 (32).
All winter average temperatures were above normal: daily max (18.9°), up by 0.8°; daily mean (11.6°), up by 1.2°; daily min (4.3°), up by 1.6°. In each case, winter of 2009 had been slightly warmer. As in last winter, the subsoil temperature was very high: 17.0°, which is 2.7 °above normal for winter in the decade from 1999. In that same decade, only 34% of winter mornings were cloudy; this winter’s value of 43% has become normal since.
The winter rainfall total of 134 mm is just above the average (125 mm) and in the 62nd percentile.Climate Winter 2013

Data. Rainfall data is from Manilla Post Office, courtesy of Phil Pinch. Temperatures, including subsoil at 750 mm, and other data are from 3 Monash Street, Manilla.