Variation In Precipitation At Dulles International Airport (IAD) 1964-2017

Previously I wrote about the variation In precipitation At Washington Reagan National Airport (DCA) and Baltimore Washington International Airport (BWI) to see if there was a significant change over the years due to Climate Change, and now it’s time to look at Dulles International Airport.

The IAD dataset starts later than that for DCA and BWI, and starts from April 1, 1960. As with the DCA and BWI data, there appear to be a few days with missing data, as for some years there is only data for 364 days. The actual number of days per year of data was taken into account when computing means. Also, large amounts of data are not available for various dates 1960 through 1963, and of course there is no data for the remainder of 2018. So the plots are from 1964 through 2017.

Each of the graphs can be clicked to be viewed full size.

The first graph is the average daily precipitation. This is total amount of rain per year divided by the number of days in the year. This graph shows a slight increase, from 0.110 to 0.115 inches per day:

Next is a graph of the number of days per year with precipitation, followed by its inverse, the number of days without. The number of days with precipitation has increased from about 114 to 121, or 6 more days. The increases at DCA and BWI were 5 days, and they was over a larger number years. It currently rains about 115 days per year at DCA, and 118 days per year at BWI.

This leads to the next graph, the average rainfall on days when it actually rained. There is no apparent change at all – this graph is flat. So while it rains about 6 more days a year at IAD, the amount of rain, on days when it does rain, is the same. Actually if you squint, it looks like it might be very so slightly decreasing, but it is subtle. And probably going to be different once you add in another year’s worth of data.

Next, we can look at the standard deviation in rainfall amounts on days when it rains, standard deviation is amount of variation of a set of data values around the mean (average). My previous post has a link for more information about standard deviation, as well as the best standard deviation joke for math nerds.

The standard deviation rose from about 0.48 to 0.50, about half the increase seen at BWI. By comparison, the standard deviation was unchanged at DCA. If you torture the data enough, you can find possible reasons for the change. I notice there was a step change / increase in the standard deviation from 2005-2014, which seems to have since stopped. You can also spot a period in the 1990s when the standard deviation was low. I am sure 20 people can find 20 more possible reasons. It’s like a Rorschach test for meteorologists. Here’s the standard deviation plot:

Finally, we can look at the number of days that rained and had rainfall over two standard deviations (using the standard deviation for that year), treating this as significant or extreme rainfall events. The trend of this is completely flat:

To summarize the analysis of rainfall events at DCA, BWI, and IAD:

  • The number of days with rain is increasing, 5 or 6 more days per year, over the last half century or more, at all three airports.
  • The average annual measured rainfall is either decreasing (DCA) or increasing (BWI, IAD), depending on which station you look at.
  • The average amount of rain on days when it does rain is either decreasing (DCA), increasing (BWI) or exactly the same (IAD).
  • The number of days with significantly high rainfall, exceeding two standard deviations, is either very slightly increasing (BWI) or unchanged (DCA, IAD), depending on which airport you look at.
  • Variation In Precipitation At Baltimore Washington International Airport (BWI) 1937-2018

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    Previously I wrote about the Variation In Precipitation At Washington Reagan National Airport (DCA) 1945-2018 to see if there was a significant change over the years due to Climate Change, and now it’s time to look at BWI Airport.

    The BWI dataset starts earlier than tat for DCA, and runs from July 1, 1937 to July 18, 2018. As with the DCA data, there appear to be a few days with missing data, as for some years there is only data for 364 days. The actual number of days per year of data was taken into account when computing means. Also, some data is not plotted for 1945 or 2018, namely the number of days with/without rain for those years, as a full year of data is not available.

    Each of the graphs can be clicked to be viewed full size.

    The first graph is the average daily precipitation. This is total amount of rain per year divided by the number of days. It shows an increase from roughly 0.108 to 0.121 inches per day from 1939 to 2018. That’s an increase of about 12%.

    Next is a graph of the number of days per year with precipitation, followed by its inverse, the number of days without. The number of days with precipitation has increased from about 113 to 118, or 5 more days. This is the same increase we saw at DCA, although it seems rain about 3 fewer days per year at DCA vs BWI (You picked the right airport to leave near, Walter):

    That leads to the next graph, the average rainfall on days when it actually rained. This shows an increase from about 0.35 inches to 0.37 inches. (The trend at DCA was actually negative, from 0.37 to 0.35 inches in fact. Exactly opposite. Hmm…):

    Next, we can look at the standard deviation in rainfall amounts on days when it rains, standard deviation is amount of variation of a set of data values around the mean (average). My previous post has a link for more information about standard deviation, as well as the best standard deviation joke for math nerds. The standard deviation in rainfall amounts at BWI is increasing. Looking at the graph, the increase seems to be mostly due to an increase during the 2005-2015 period, which has since ended. Is it a short term variation due to random processes, or part of a long term shift?

    Next we can look at the number of days that rained and had rainfall over two standard deviations (using the standard deviation for that year), treating this as significant or extreme rainfall events. The trend of this is completely flat:

    But, you might ask, isn’t the standard deviation slightly increasing each year? What if we use a fixed standard deviation value, like 0.50 which seems to be the mean value? Doing that, you do see an increase from about 9 to 11 days per year:

    Next up… Dulles Airport (which unfortunately has the shortest dataset of all three major airports)

    Variation In Precipitation At Washington Reagan National Airport (DCA) 1945-2018

    Recently the weather, at least precipitation wise, in the DCA area has been variable. It was very wet and rainy, then we had dry conditions for several weeks with essentially no rain. Now, it is very wet again. Are we seeing extreme (some may say historic) changes in the weather? Or are these just the usual variations?

    Are rainfall events are becoming less common, but more extreme? That is, it rains less often, but we get more rain when it does rain, rather than getting rainfall spread out evenly over time as it used to be. And maybe we’re getting more rain overall. Or possibly less rain, those two claims seems to depend on recent weather memory.

    To check this claim, data for Washington Reagan National Airport (DCA) was downloaded from the NOAA NCDC site and analyzed in several ways. You can download this data yourself, if you wish: https://www.ncdc.noaa.gov/cdo-web/

    The dataset runs from July 1, 1945 to July 18, 2018. There appear to be a few days with missing data, as for some years there is only data for 364 days. The actual number of days per year of data was taken into account when computing means. Also, some data is not plotted for 1945 or 2018, namely the number of days with/without rain for those years, as a full year of data is not available.

    Each of the graphs can be clicked to be viewed full size.

    First, is there a significant long term trend in the amount of precipitation at DCA? No, there does not seem to be (if you squint you may see a very small decline over time, the sign of this slope likely changes from year to year with normal variability in rainfall):
    Mean daily precipitation

    Second, are rain events becoming less common, but with higher rainfall totals from those events? That would mean we are seeing fewer days with rain, but more rain on those days. The following two graphs show the number of days without any rain, and the number of days with rain, defined as 0.01″ or more. First the number of days without rain. Which is not increasing, but actually decreasing:
    Days per year without precipitation

    And the number of days per year with rain, which of course is just the inverse of the previous graph. It’s raining 5 or 6 more days per year (sorry, Walter):
    Days per year with precipitation

    Third, what about the rainfall totals on days when it actually rains. Is that increasing, leading to more extreme rain events? No, it isn’t. It is actually decreasing, which makes sense considering the mean rainfall per year is essentially steady, and it is raining a few more days out of the year:
    Mean precipitation for days with precipitation

    OK, maybe it is mostly the same, but we’re getting a few more extreme rainfall events per year? Let’s look at the standard deviation of the rainfall amounts, again only for days when it actually rains.

    Standard deviation is amount of variation of a set of data values around the mean (average), there is an explanation here: https://en.wikipedia.org/wiki/Standard_deviation If you get this joke, you understand standard deviation: “Yo mama is so mean she has no standard deviation”

    Hmm, no, that is also steady:
    Standard deviation of daily precipitation

    One more thing, look at the number of days with very extreme rainfall. How about the number of days where the rainfall exceeded two standard deviations? That also seems to be flat:
    Days above two standard deviations

    Anything else we can check to see if precipitation is indeed getting more extreme in Washington DC? So far, it doesn’t seem to be.

    Note, the purpose of this analysis was not to try and discredit man made climate change aka AGW, which is certainly real. Only to see if claims of a noticeable effect on the precipitation patterns in the DC area can be confirmed, which does not seem to be the case.

    Winter 2017-2018 Snowfall

    On Parr’s Ridge in northern Carroll County, MD.

    Contest!
    Guess The Amount of Snow At Casa De Smolinski

    Seasonal Snowfall Contest Entries

    16	Snowbrow
    20.7	wadejg
    23.9	dcasey
    24.5	Squawks12
    24.9	Bob919
    29.2	SSB
    30	Takoma
    33.3	Merry Mildist
    36.8	83worldtraveler
    36.9	beadalou
    38	ubimea
    38.4	USAJerry
    38.5	Evann21
    40.8	Groveton
    41.1	I Love MetMet
    41.1	Rex Block
    41.3	taylort2
    41.7	PBH
    43.6	gelezinis vilkas
    44.4	SoCal SnowGal
    44.4	Xtrain21
    45.5	Rex Block
    46.2	Terpiecat
    47.325	Kate commenting
    50	walter-in-fallschurch
    51	huskerdont77
    51.4	BigCountry
    51.9	bachaney
    52.2	eric654
    52.4	gelezinis vilkas
    54.7	parksndc
    54.9	heroine.chic
    55.2	chrisofthebeagles
    55.9	heerokdas
    62.2	TominMichiganParkDC (*) late entry, not reflected in the mean/median values
    62.8	Lord Stark
    63.1	WGsnowchic
    66.0	--sg
    65.0	CalypsoSummer
    67.6	surewhynot
    68.8	wwashington postt
    81.3	hee hee
    

    Mean: 45.68″
    Median: 44.4″

    November Total: 0.0″

    Saturday December 9, 2017:
    3.5″ snow.

    Friday December 15, 2017:
    0.75″ fluffy snow.

    Sunday December 24, 2017:
    0.25″ Snow and sleet.

    Saturday December 30, 2017:
    2.0″ very dry snow.

    December Total: 6.50″

    Thursday January 4, 2018:
    0.9″ very dry snow.

    Monday January 8, 2018:
    0.25″ snow and sleet.

    Saturday January 13, 2018:
    0.25″ snow and graupel.

    Tuesday January 16, 2018:
    0.3″ snow.

    Wednesday January 17, 2018:
    2.0″ snow.

    Tuesday January 30, 2018:
    1.5″ snow.

    View post on imgur.com

    January Total: 5.2″

    Friday February 2, 2018:
    Snow flurries.

    Sunday February 4, 2018:
    2.4″ of heavy wet snow, followed by rain and some freezing rain.

    Wednesday February 7, 2018:
    Sleet, freezing rain (0.1 inch) and rain.

    Monday February 12, 2018:
    Some sleet in the morning.

    Saturday February 17, 2018:
    2.0″ wet snow.

    February Total: 4.4″

    Friday March 2, 2018:
    0.5″ wet snow, whipped by strong winds.

    Monday March 12, 2018:
    1.2″ snow.

    Wednesday March 14, 2018:
    Snow flurries.

    Thursday March 15, 2018:
    Snow flurries.

    Friday March 16, 2018:
    Snow flurries.

    Tuesday March 21, 2018:
    7.5″ snow.

    Wednesday March 20, 2018:
    8.3″ snow.

    Sunday March 25, 2018:
    Light snow flurries.

    March Total: 17.5″

    Monday April 2, 2018:
    0.5″ of snow after 0.43″ of rain.

    Monday April 9, 2018:
    Snow flurries/showers, no accumulation.

    Tuesday April 17, 2018:
    Snow flurries, no accumulation.

    Thursday April 19, 2018:
    Rain and some sleet mixed in.

    April Total: 0.5″

    2017-2018 Season To Date Total: 34.1″

    Previous seasons:
    Winter 2016-2017
    Winter 2015-2016
    Winter 2014-2015
    Winter 2013-2014

    Winter 2009-2010: No details, but the seasonal total was about 100″ with three major blizzards.

    Project: Exterminate Yellow Jackets

    For several years, yellow jackets made it extremely unpleasant, and often downright impossible, to enjoy sitting outside during the summer on the deck. As everyone who has experienced yellow jackets knows, these are extremely aggressive and downright hostile insects. While bees are generally peaceful and useful creatures, helping to pollinate, yellow jackets don’t pollinate, and are generally pure evil. My goal now every spring is to do my best to completely eradicate them from the area. Many of the yellow jackets found in the United States are not even native, but invasive species from Europe, if you need additional incentive to obliterate them. Again, to repeat. Yellow jackets are mean and nasty wasps. They do not pollinate flowers and help fruit grow. They are not critical to the ecosystem of your back yard. You can do your best to completely eradicate them from your yard, and feel no guilt doing so.

    Most people wait until they are being bother by yellow jackets to put up a trap or two in the summer. By then, it is far too late. Yellow jacket nests can have several thousand wasps by mid summer, and you may well have multiple nests in or near your yard. It is simply impossible to trap them all by this time, in fact their nests will probably increase in population faster than you can trap and kill them. You’ll find it impossible to sit outside and enjoy summer, being forced to hide inside and watch reruns of old TV shows.

    But it turns out, there is a solution. You need to act now. Yellow jacket nests are annual, only the queen survives winter. Once the weather warms up (as in right now) the queens emerge, to establish the new nests for this summer. While later in the season they have their evil minions to do their bidding, gathering food and generally making your life miserable, right now they have to do the dirty work. Which means this is your opportunity to trap and kill every single queen you possibly can. And it’s not that difficult to do.

    After experimenting with various commercial yellow jacket traps, most of which used expensive pheromone based lures that had to be replaced often, and often did not even work very well, I stumbled on this style trap made by Victor:

    The trap is a plastic bottle with a top that screws on. The top has small holes in it, under the yellow top (which keeps out the rain), which the wasps can fly into. But due to their erratic flying pattern, they have a difficult time escaping from the trap. So they are stuck inside, and finally die.

    I bait the traps with a grape juice / cranberry juice mix, I find this works best, although you can try plain grape juice or other juices, and see what works best for you:

    I pour a small amount of juice into each trap, this lures the yellow jackets into the trap, where their meet their demise:

    I purchased a dozen traps several years ago, and place them in various locations around the perimeter of my yard. You can probably get by with just a few, if you have a small yard. You do want to find the ideal locations to place them, which depends on where the likely yellow jacket nests are located. I find that placing them on the sides of my yard near the woods captures the most wasps, which makes sense. After a few years of using them, I now know where they should be located, but to get started you can experiment by spacing the traps near the most likely areas, and then seeing which traps capture the most wasps, and which capture few, or even none. Move the traps away from areas that are not productive to those that are, of course it may take a season to completely figure it out, but even with non optimal locations, you will likely capture and kill many queens.

    You need to periodically examine the traps to check for dead wasps, as well as refill with more juice as needed. Obviously you want to carefully examine the trap before opening it, to make sure all the wasps are dead, or in poor enough shape that you can kill them after dumping out the contents. Queens are fairly easy to identify, they are much larger than the usual yellow jackets you see.

    There are plans online for building your own trap from a 2 liter soda bottle. I’ve tried this, and have not had much success, but you might want to give it a try and see how it works for you.

    Again, it is imperative to get your traps out now, so you can capture and kill every queen yellow jacket possible. Each queen you kill means one fewer nest, which means thousands fewer yellow jackets invading your barbecues this summer.

    Winter 2016-2017 Snowfall

    On Parr’s Ridge in northern Carroll County, MD.

    Contest
    Guess The Amount of Snow At Casa De Smolinski

    Seasonal Snowfall Contest Entries

      2.2	Ok_now_3-2-1_DANK-HANK
      3.2	Pamsm
      4.4	I love Kate
      5.0	hee hee
      7.5	Questsnow
     12.5	83worldtraveler
     19.7	Groveton
     23.6	Snowbi-wan Kenobi
     24.1	A CAMDEN WALKER
     25.7	wadejg
     26.2	Kate commenting
     27.0	taylort2
     29.4	Autumn_Forge
     29.7	heroine.chic
     31.6	cameraman
     31.7	Rex Block
     33.3	bob919
     35.1	Xtrain21
     36.5	walter-in-fallschurch
     38.4  	pct_atc
     43.2	NorthArlington101
     45.6	Terpiecat
     50.2	eric654
     53.4	AndrewinStafford
     54.5	chrisofthebeagles
     57.3	BigCountry
     57.9	slamslam
     79.0	surewhynot
    120.0	The Adorable Miniature Snowplows
    201.7	Days Of Weather Past 
    

    Saturday November 19, 2016:
    Sleet. Changed to light snow before ending.

    Sunday November 20, 2016:
    Snow flurries.

    November Total: 0.0″

    Sunday December 11, 2016:
    0.1″ Snow.

    Saturday December 17, 2016:
    0.5″ Snow and sleet, then 0.2″ freezing rain.

    December Total: 0.6″

    Friday January 6, 2017:
    2.8″ Snow.

    Saturday January 7, 2017:
    Light snow, no accumulation.

    Tuesday January 10, 2017:
    Light snow, 0.1″ accumulation.

    Wednesday January 11, 2017:
    0.07″ of freezing rain, accumulation on the ground and road surfaces only, due to above freezing air temperatures.

    Saturday January 14, 2017:
    Sleet, light snow, freezing rain.

    Friday January 27, 2017:
    Snow flurries.

    Saturday January 28, 2017:
    Snow flurries.

    Sunday January 29, 2017:
    Snow flurries.

    Monday January 30, 2017:
    0.5″ of snow from a quick squall.

    January Total: 3.4″

    Thursday February 9, 2017:
    3.0″ of snow after rain.

    Wednesday February 15, 2017:
    Snow flurries and graupel.

    February Total: 3.0″

    Friday March 3, 2017:
    Light snow, 0.1″ accumulation.

    Friday March 10, 2017:
    Light snow, 2.8″ accumulation.

    Tuesday March 14, 2017:
    11.0″ of heavy but not wet snow.

    A view of one of the ponds. Sadly there are frog eggs under all that snow:

    I hope the Lilac makes it:

    Saturday March 18 – Sunday March 19, 2017:
    2.0″ of snow.

    March Total: 15.9″

    Friday April 7, 2017:
    Light snow for about an hour, no accumulation as it was 41F.

    April Total: 0.0″

    2016-2017 Season To Date Total: 22.9″

    Winter 2015-2016 Snowfall

    Saturday December 19, 2015:
    Trace snow.

    December Total: Trace

    2015-2016 Season Total: Trace

    Monday January 4, 2016:
    Flurries.

    Tuesday January 12, 2016:
    0.3″

    Sunday January 17, 2016:
    0.2″

    Wednesday January 20, 2016:
    0.3″

    Friday January 22, 2016 – Saturday January 23, 2016:
    28.0″

    January Total: 28.8″

    Friday February 5, 2016:
    A dusting of snow while temperature were above freezing.

    Tuesday February 9, 2016:
    7.5″ as of 11:00 AM. Fairly wet and heavy snow. Above freezing for much of the time it fell.
    Then 2.8″ in the evening for a total of 10.3″.
    Some earlier pictures:




    Friday February 12, 2016:
    1.0″ of very light and puffy snow, I was able to clear the driveway with the leaf blower.

    Monday February 15, 2016:
    1.0″ of snow, later changing to sleet and some light freezing rain.

    Thursday February 25, 2016:
    Snow flurries.

    Friday February 26, 2016:
    Snow flurries.

    February Total: 12.3″

    Friday March 4, 2016:
    1.6″ of snow.

    Sunday March 6, 2016:
    A dusting of snow.

    Saturday March 19, 2016:
    0.5″ of snow.

    March Total: 2.16″

    Sunday April 3, 2016:
    A dusting of snow during a strong wind event.

    Friday April 8, 2016:
    Snow flurries.

    Saturday April 9, 2016:
    0.5″ of snow, also some graupel.

    April Total: 0.5″

    2015-2016 Season Total: 43.7″

    Winter 2014-2015 Snowfall

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    Thursday November 13, 2014:
    0.5 inch snow.

    Wednesday November 26, 2014:
    0.56 inch of rain, changed to snow early morning
    3.9 inch snow.
    Changed to graupel as it was ending.

    Science experiment with the kids:

    We cut a block of snow from outside, 12.5 by 9 by 7.5 cm, and computed the volume: 843.75 cm3. We shaved the top to make sure it was even.

    Then we took the snow and weighed it, and came up with 160g.

    We melted the snow and measured the volume, and got 160 ml (nice to see the agreement).

    Then we computed the snow to liquid ratio: 843.75/160=5.27.

    Our measured snow depth here was 3.9 inches, so that is 0.74 inches liquid. We got 0.56 inch of rain before it switched to snow. So rather impressive 1.3 inches of liquid total.

    Saturday November 29, 2014:
    0.3 inch of snow from a quick dusting.

    November Total: 4.7 inches

    Tuesday December 2, 2014:
    0.54 inch of rain.
    0.2 inch of snow/sleet.

    Monday December 8, 2014:
    Snow flurries.

    Tuesday December 9, 2014:
    0.1 inch freezing rain.

    Wednesday December 10, 2014:
    Snow flurries in the evening.

    Thursday December 11, 2014:
    Snow flurries and light snow throughout the day, 0.25 inch total accumulation.

    December Total: 0.45 inches

    Monday January 5, 2015:
    Snow flurries in the morning.

    Tuesday January 6, 2015:
    3.0 inches of snow.

    Wednesday January 7, 2015:
    0.3 inches of snow.

    Monday January 12, 2015:
    0.1 inch of freezing rain.

    Wednesday January 14, 2015:
    0.2 inches of snow.

    Monday January 19, 2015:
    Dusting of snow.

    Wednesday January 21, 2015:
    3.5 inches of snow.

    Friday January 23, 2015 – Saturday January 24, 2015:
    1.25 inches of snow.

    Monday January 26, 2015 – Tuesday January 27, 2015:
    1.9 inches of snow.

    Thursday January 29, 2015
    0.25 inches of snow.

    January Total: 10.4 inches

    Monday February 2, 2015
    1.0 inches of snow/sleet/rain/etc.

    Monday February 9, 2015
    Crunchy coating of snow, sleet, freezing rain.

    Thursday February 12, 2015
    0.1 inches of snow.

    Saturday February 14, 2015
    0.5 inches of snow.

    Monday February 16, 2015 – Tuesday February 17, 2015
    2.5 inches of snow.

    Wednesday February 18, 2015
    0.1 inches of snow.

    Thursday February 19, 2015
    A dusting of snow.

    Saturday February 21, 2015
    7.25 inches of snow.

    Thursday February 26, 2015
    0.2 inches of snow.

    Friday February 27, 2015
    0.25 inches of snow.

    February Total: 11.90 inches

    Sunday March 1, 2015
    1.0 inch of snow, followed by sleet and about 0.1 inch of freezing rain.

    Tuesday March 3, 2015
    0.1 inch of freezing rain.

    Thursday March 5, 2015
    13.25 inches of snow.

    Friday March 20, 2015
    3.0 inches of snow.

    Tuesday March 24, 2015
    Dusting of snow.

    March (to date) Total: 17.25 inches snow, 0.1 inch ice

    Season To Date Total: 44.70 inches