Past IEM Features tagged: aridity

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Aridity for July

04 Aug 2015 05:41 AM
The month of July is past us now, so it is a good time to look back and compare it with previous years. The featured plot is known as an aridity plot, which compares the normalized departure of temperature with precipitation. The normalization is accomplished by computing the standard deviation each data set and using that value as the unit of measure. The value for 2015 is highlighted with a circle around the origin, with some of the years outside of that circle labelled. The flood year of 1993 sticks out clearly as the historic precipitation totals well surpass any other July. This year came in on the cool and wet side of long term averages.

Voting:
Good: 18
Bad: 6
Abstain: 5

Tags:   aridity  


Stuck with dry aridity

04 Sep 2013 05:20 AM
The featured chart shows the evolution of aridity since mid April evaluated on a weekly basis for a trailing 14 day period. The weekly values are connected in time to show the trajectory of the change in aridity. This type of chart has a nice property of tending to make circles as temperature and precipitation departures tend to influence each other. The chart shows an interesting transition from 1 Jul to 8 Jul, where we went from above positive precipitation to negative and have not make it back. In fact, it it kind of interesting to see how we've gone from a cold and dry to a hot and dry situation with the precipitation departure holding close to negative one sigma. The line is nearly horizontal going from 19 August to 2 September. The forecast does not hold much hope for positive precipitation departures with more hot weather on the way next week.

Voting:
Good: 32
Bad: 3

Tags:   aridity  


click image for a better view

July Arridity

31 Jul 2013 05:02 AM
The featured chart is an aridity chart showing the combination of temperature and precipitation departure for the month of July expressed in units of standard deviation from average. The total so far for this July is shown on the chart as a red dot and is nearly the same value as 1947! There have been other IEM daily features this year showing 2013 trending like 1947. Extreme dots on this chart are labelled and 1993 certainly stands out (the great flood year). A simple fit is made through this plot showing the inverse relationship as below average temperature is correlated with above average precipitation. This July is a bit unique in the regard of being one of the most extreme in quadrant III (below average temperature and below average precipitation).

Voting:
Good: 79
Bad: 8

Tags:   aridity  


Updated Aridity Plot

15 Aug 2012 05:58 AM
A few weeks back, we featured a plot known as an aridity plot showing the combination of seasonal temperature and precipitation departure from average. This departure is measured in units of standard deviation to provide a closer comparison between temperature and precipitation departures. 2012 still ranks up there with the other legendary years of Iowa's climatological past. A simple linear fit is also shown. While the correlation is a bit low, the implication is that dry years tend to be warm and wet years tend to be cool.

Voting:
Good: 64
Bad: 6

Tags:   aridity