Tag Archives: dry air

January 2014 the driest !

Posted in Manilla NSW, Monthly weather by

The daily weather logWeather log January 2014.

Two 21st century records were broken on the 3rd: the daily maximum was 43.7°, and the relative humidity fell to 2%. A west wind of 30 km/hr blew all that day. The early morning dew point on the 6th was a record January low of minus 3.3 degrees. A second warm spell came about the 15th. Subsoil temperature fell from high to normal during the month.
Rain of 1.8 mm was recorded on the 20th.

Comparing January monthsClimate January 2014.

As well as having almost no rain, this month had by far the lowest January dew point of the century: 6.9°, which is 7.3° below normal! Compared to January 2013, which was very hot, days were much the same (35.9°), but nights were cooler (18.5°). By contrast, January 2012 had been very cool and cloudy.
The total rainfall of 1.8 mm was the lowest January value in the 131-year record. The next lowest was 7 mm in January 1940.
Counting more than one month, the six-month rainfall total of 184 mm is the worst shortage at this time. It is in the 11th percentile of all six-monthly totals. However, such low totals usually come in August or September. It is rare for six-monthly totals as low as 184 mm to come in a summer month: it has happened only thirteen times. The lowest six-monthly total for a summer month was 145 mm for December 1946. Next was 151 mm for December 1951.

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.

December 2013: air still dry

Posted in Manilla NSW, Monthly weather by

The daily weather logWeather log December 2013.

The month began cool, including two nights at 6.9°, the coldest December nights in this record. Later it became very warm, with one night of 24.0° and one day of 40.2°. Spells of sunny weather were separated by five rainy days.
The relative humidity on the afternoon of the 29th was the record low value of 4%, as on 10/1/13 and 13/8/13. (These values may be wrong. Few hygrometers can be read so low.)

Comparing December monthsClimate December 2013

This December was warm: just slightly cooler than December last year, and very much warmer than those of 2010 and 2011. Extremely dry air brought a new record low December mean morning dew point of 8.8°.
Subsoil temperature (25.7°) remained 1.5° above normal.
The total rainfall of 45.6 mm was in the 28th percentile, well below the average of 74 mm. However, there are still no serious shortages in rainfall totals for more than one month.

The Year 2013

This was one of the warmer years in the new century (but much cooler than 2009). It had the driest air, with a mean early morning dew point of 5.4°, 1.5° below average. The air has become drier each year since 2010.

This year also had the highest subsoil temperature: 22.1°, 1.9° above average.
Extremely high rainfall in June (98mm) was balanced by very low rainfall in August (6.4mm) and October (15mm), for a low annual total of 576 mm, in the 37th 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.

3-year trends to May 2013

Posted in 3-year climate trends, Manilla NSW by

Parametric plots of smoothed climate variables at Manilla

“Still warm; not quite so dry”Trends to May 2013.

May continued warm, but not quite so dry. Skies became cloudy again, and minimum temperature rose back to normal.

Points in red for November 2012 complete fully-smoothed data for spring 2012. They define a reversal of climate. Anomalies of moisture variables (rainfall, cloud, dew point, and (minus) temperature range) peaked in the “drought” sense in September or October. The anomaly of daily maximum temperature peaked (probably) in November, and that of daily minimum temperature peaked later (date uncertain).

The curved red arrows on the first graph emphasise the fact that, for these peaks and troughs, temperature extremes came a month or more after rainfall extremes.

ENSO and this 3-year temperature-rainfall-humidity record

I discussed the match between Manilla climate variation at this time and the El Niño – Southern Oscillation in a post on the weatherzone forum thread “ENSO Discussion 2013”: Post #1195723 of 26 May 2013.

Note: 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.

April 2013: Very Dry Air

Posted in Manilla NSW, Monthly weather by

The daily weather logWeather log April 2013.

For most of the month, days were sunny and fairly warm, while nights were cool (but not frosty). The last days were several degrees warmer than normal: as warm as the first days. Two afternoons had extremely dry air, with relative humidity below 10%. While two days had a little rain, the month ended with no readings above 5 mm in eight weeks.

 Comparing April monthsClimate April 2013

 

The mean maximum temperature was a little high and the mean minimum rather low, making the daily temperature range (18.3°) an April record. The mean early morning dew point (4.3°) was also a record (low) value, but cloudiness was normal. The subsoil was almost 2° warmer than normal: its autumn cooling was about three weeks late.
The rainfall total of 4.8 mm was far below the average of 39.3 mm, but April has less rain than that in 15% of the years.

Five Recent Months had Very Dry Air

I have put headlines about very dry air on five monthly weather reports in the last twelve. It is true: the air has been much drier than it was from 1999 to 2009.
I judge the moisture in the air mainly by the dew point – the temperature when dew would form. Normally the early morning dew point, as a monthly average, changes through the year from 15 degrees in February to 2 degrees in July. In some recent months it has been far lower than what is normal for the month:

  • May 2012: 4.4° below normal;
  • August 2012: 4.4° below normal;
  • September 2012: 4.6° below normal;
  • October 2012: 6.6°(!) below normal;
  • April 2013: 4.7° below normal.

Even in the 2002 drought, the furthest the dew point went below normal was 3.9°, in October.
One degree of change in dew point is like 5% change in relative humidity. In these months the morning relative humidity has been below normal by 20% to 35%. Afternoon humidity has been down by more: many days have gone below 10% humidity. These extremely low humidity values must affect crops and pastures, pests and diseases, and may affect health.

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.

 

3-year trends to September 2012

Posted in 3-year climate trends, Manilla NSW by

Parametric plots of smoothed climate variables at Manilla

“Still Very Dry Air”Trends to September 2012.

In September, daily maximum temperatures finally rose above normal. As in August, Dew Points (humidity) remained extremely low, daily minimum temperature very low, rainfall low, and daily temperature range very high. Cloudiness finally fell below normal, and subsoil temperature fell towards normal.

Fully-smoothed data (in red) now include March 2012. All variables for that month show a retreat from the “flooding rains” climate peak. Because the daily minimum temperature anomaly did not reach a minimum in March as I expected, the sequence of peaks for individual variables must be amended as follows:
Nov-11: Rainfall (max); Subsoil temp (min);
Dec-11: Temp range (min); Dew Pt (max);
Jan-12: Temp max (min);
Feb-12: Temp min (min).
The February 2012 value of smoothed minimum daily temperature anomaly (-1.11 degrees) was not quite as low as the record set in March 2008 (-1.17 degrees).

Note: 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.