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.
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.
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.
Trends in global temperature and in carbon emissions changed sharply several times during the last 160 years.
One question is at the heart of concern about human influence on climate: how does global temperature relate to human-caused emissions of carbon dioxide?
This graph shows that relation: it does not explain it.
I display two well-established data sets:
1. The HadCRUT4 record of estimated global surface air temperature. Values are expressed as the anomaly from 1961-1990 mean values in degrees celsius.(See Note 1. below.)
2. Global Fossil Fuel Carbon Dioxide Emissions, tabulated and graphed as tonnes of carbon (See Note 2. below.)) by the Carbon Dioxide Information Analysis Center, Oak Ridge.(See Note 3. below.)
The format of the data is given in Note 4. below.
Multi-decadal linear trends
Trends in carbon emissions
Throughout this time, the rate of carbon emissions increased exponentially, but at rates that changed abruptly at certain dates. In units of log-cycles per century, the rates were:
From 1850: 1.97 units;
From 1913: 0.28 units;
From 1945: 2.14 units;
From 1973: 0.77 units. Continue reading
Parametric plots of smoothed climate variables at Manilla
“August 2014 back to normal”
August data (orange)
Most raw anomaly values for August have returned to near normal. The daily maximum temperature anomaly has finally fallen below normal and rainfall has risen above normal. The dew point anomaly remains well below normal, but its value is on the (green) trend line that has applied during the last three years.
Fully smoothed data (red)
Fully-smoothed data is now available for the summer season ending in February 2014. During the summer all variables except daily minimum temperature moved decisively away from drought. Rainfall increased rather slowly, but cloudiness increased very rapidly, and daily temperature range fell very rapidly.
The hot-arid climatic peak (drought) of spring 2013
Extreme anomaly values of climate variables came in the following order:
Highest minimum temperature (not high): July;
Highest subsoil temperature (extreme): July;
Widest temperature range (very wide): October;
Highest maximum temperature (extreme): October;
Least cloudiness (normal): October;
Lowest dew point (extreme): December;
Lowest rainfall (very low): December-January.
This is not the order that is typical in recent extreme episodes. The smoothed rainfall anomaly minimum of -22.3 mm (not nearly as low as the -27.1 mm of July 2002) came much later than the peak of daily maximum temperature. On the top left graph the trace curved anti-clockwise, which is unusual.
Fully smoothed data – Gaussian smoothing with half-width 6 months – are plotted in red, partly smoothed data uncoloured, and raw data for the last data point in orange. January data points are marked by squares.
Blue diamonds and the dashed blue rectangle show the extreme values in the fully smoothed data record since September 1999.
Normal values are based on averages for the decade from March 1999. They appear on these graphs as a turquoise (turquoise) circle at the origin (0,0). A range of anomalies called “normal” is shown by a dashed rectangle in aqua (aqua). For values in degrees, the assigned normal range is +/-0.7°; for cloudiness, +/-7%; for monthly rainfall, +/-14 mm.
The daily weather log
The weekly temperature was normal throughout, but the first half of the month had sunny warm days, cold nights and very dry air. The night of the 3rd (-4.0°) was the coldest August night this century, and the early morning of the 12th had the lowest August dew point (-8.7°). Two brief overcast and rainy spells began on the 16th and 26th, yielding 54.4 mm in five rain days. The reading of 26.6 mm on the 17th was one of the highest for August in recent years.
The number of frosts (12) was a little below normal (15).
Comparing August months
While August 2008 had been the coolest, and August 2009 the warmest in the 21st century, nearly all averages this month were near normal. As exceptions, the daily maximum temperature was slightly low and the dew point (as in the two previous August months) was very low. Few mornings had dew on the grass.
The total rainfall of 54.4 mm is in the 75th percentile, well above the August average (40 mm). This rain also raised the rainfall totals for periods of more than one month, so that only the 18-month total of 691 mm now remains as a serious shortage (9th percentile).
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.
This post is the sixth in a set for the 12 calendar months. Graphs are sixteen-year logs of the monthly mean anomaly values of nine climate variables for Manilla, NSW, with fitted trend lines. I have explained the method in notes at the foot of the page.
Raw anomaly values for August
Extreme values of August anomalies in this period were:
Temperature range anomaly (minus) +4.1 deg: August 2010;
Dew Point Anomaly -4.5 deg: August 2012.
Trend lines for August
The trend of mean temperature anomalies was almost constant. The trend of daily maximum temperature anomalies was almost constant, but had a weak minimum at 2007. The trend of minimum temperature anomaly had a weak minimum in 2001 and a weak maximum in 2010. The subsoil temperature anomaly trend ended very high, after a weak minimum in 2005.
The graph above relates to a graph of the cumulative values of the Southern Oscillation Index, posted earlier.
This graph is in a more familiar form . It may help to explain what the earlier graph means. That is, that the SOI was dominated by positive values (towards La Niña) for about fifty-nine years before 1976, and was dominated by negative values (towards El Niño) for twenty-four years after that date. From 2000 the trend seems to be upward, showing La Niña dominance again. Broadly, these were straight-line CUSUM relationships throughout each of the periods, as shown by the coloured trend lines. Slopes on a CUSUM plot represent offsets of the mean monthly value: the mean SOI in the earlier period was +1.4 units, and that in the second period was -3.5 units. Since 2000, the mean monthly value is around +1.0 units. Continue reading
This graph is a log of cumulative values of the monthly Southern Oscillation Index for the last 139 years. (See Note added 25th August 2014 below.)
High values of the SOI (contrary to NINO3.4 values for the ENSO index) relate to deluges in Australia and low values relate to droughts.
This is the CUSUM technique, invented in 1954 by E.S.Page. Pay attention to the slopes on the graph.
I have identified major El Niño and La Niña events on the graph. La Niñas have extreme upward slopes and El Niños exteme downward slopes.
The main feature of the graph, which is obscure in graphs that do not use CUSUM, is that La Niñas dominated the 60-year period from 1917 to 1976, and El Niños dominated the 25-year period from 1976 to 2000. I have drawn linear trend lines to make this clear. The first trend line (La Niña dominant) begins at an SOI CUSUM value of -30 in May 1917 and ends at a value of +960 in February 1976, yielding a slope of +1.4 SOI units per month. The second trend line (El Niño dominant) ends at a value of -40 in December 1999, yielding a slope of -3.5 SOI units per month.
The tendency to El Niños in the second period was greater than the tendency to La Niñas in the first period by a factor of more than two.
Although the period since 2000 is very short, the trend seems to slope upward at about +1.0 SOI units per month.
I posted discussion of an earlier version of this graph in “Weatherzone” Forums >> Weather >> Climate and Climate Change >> ENSO Discussion 2012 Post #1103736
Note added 25th August 2014
Another CUSUM SOI graph
By searching the net for “cusum soi” I find that a plot of the cumulative sum of values of the Southern Oscillation Index was published by Cordery and Yao in 1993: “Non stationarity of phenomena related to drought”.
Neither the data nor the approach of Cordery and Yao are the same as mine.
Cordery and Yao used monthly normalised SOI anomaly data supplied by the Bureau of Meteorology, as I did. They mention that “Prior to 1933 there are 7 gaps in the SOI sequence resulting from a total of 102 months of data missing from the Papeete pressure record.” I have not found any note of this with the Bureau’s current data table.
Apart from an (unexplained) reduction in the scale of CUSUM values by a factor of 500, there are important differences in detail. During the time of La Niña dominance, I find that the major CUSUM peaks (La Niña turning to El Niño) in 1918, 1939, and 1976 lie almost in one line. Cordery and Yao’s plot has the 1939 peak relatively much higher: the second highest on the record after the 1976 peak, and almost as high.
Cordery and Yao used CUSUM to show that the SOI series was not stationary for a part of the time. I used it to identify persistent shifts in the SOI mean value.