Native Plants, Habitat Restoration, and Other Science Snippets from Athens, Georgia

Monday: 27 June 2011

Showoff  -  @ 04:56:54
We had another series of storms last night, delivering 0.92" rainfall and bringing us above the normal June average. No complaints about that!

Last Monday I did another turtle hunt, the day after the one that netted a new discovery and the rediscovery, after three years, of Gretl. I reexamined the floodplain, but the upper search was done largely on the opposite, east-facing slope leading down to SBS Creek.

I only found one turtle, but it was Gretl, again. A little less shiny, but there's that hump in her carapace, and of course the markings are the same.



This was the first time I'd rediscovered a turtle within 24 hours of the prior encounter. On a couple of occasions I've made a rediscovery a few weeks after the first, but had no idea of the extent of the wanderings in that few weeks. This time I can make some reasonable estimate.

Here's Gretl's habitat area:



At the lower left, just about where I'm squatting to take the photo, is where I found her on Sunday morning, nestled against the fallen ash you see across the creek that runs south on the left to north on the right.

On Monday morning, 24 hours later, I found her at the upper right in the above photo, halfway up the east-facing slope. To get there she'd have had to cross the creek, ascend the secondary bank, trek across the flat to the bottom of the hill, and then climb some distance upward.

Now, my original discovery May 7 2008 had caught her at just about the upper *left* in the photo, closer to the top of the slope, but farther south. She does seem to be headed roughly back in that direction.

For all I know, this little migration down to the creek and back could be a semi daily or weekly affair for her. At the other extreme, she might spend most of the season atop the ridge, making the trip to the creek to lay eggs, and then scooting back uphill to her usual territory. It's my impression that box turtles get most of their water from the food they eat. And adults might generally prefer a more lighted environment, which she'd get uphill where the canopy is somewhat less dense. On the other hand it makes sense that she might prefer to lay her eggs near the creek, since baby box turtles are more aquatic in their first year or two. (But you'll recall that we, and our neighbors last year, have found box turtles laying their eggs way uphill and a very long distance from either creek.)


Sunday: 26 June 2011

The Year With No Spring  -  @ 06:02:11
We've been keeping an eye on the weather around here. It's now toward the end of June, when it isn't so unusual to have 90 degF, or higher, during the day, but this year we've been having them since May 1.

Up until last Wednesday night the 15th, we'd had very little rain since May 1, and then we started getting storms every few days. Nice storms, storms that had the sheriff's and fire departments out, suppressing brush fires caused by falling trees on power lines and clearing trees off roads. The general area has averaged 2.5" (we've had 3.9"), but except for one cool day has done nothing to ameliorate temperatures.

Let's see how 2011 is faring, for May and June. Here are two-dimensional plots of May vs June, one of those odd little presentations that allows you to visualize some things quite nicely. In this case, it'll let us compare the two month periods for different years. I've used a reasonably conservative estimate for the rest of June, from current predictions.

Here are the average high temperatures for May versus those for June, in Athens, GA. Long ago I at least copied the high, mean, and low monthly temperatures for every month since 1920, from this site, and those are the data I use here. I don't know why they disappeared it, for accuracy or for pecuniary gains, but there had also been daily temperature and rainfall data since 1898, I think. I've mentioned this before, because the erasing of data is just abhorrent.

We're interested how 2011 ranks for the group that had higher than normal temperatures for *both* months.

The bullseye is the average for May versus that for June, and the red circle and bars encompass a single standard deviation about that average. 2011 fits signficantly outside that circle, although there are years since 1920 with similarly high average temperatures for both months. 1933 stands out as being considerably higher at least for May; 1925 similarly higher at least for June. Those years all happen to lie within the Dust Bowl era heat waves, which also affected Georgia.



May and June 2011 haven't had particularly extreme high temperatures, in 2011, and May actually had some rather cool days. They just both had inordinately high numbers of days where temperatures exceeded 90 degF. It's clear that we'll end up with 27 days above 90F this June, and that beats the record. So let's plot the number of days 90F and above for each month. Here our data are more limited - only since 1949, starting from here, and so unfortunately we can't compare the 1920/1930s hot spots in the first figure above.

Again, the red circle means what it did before, and here 2011 stands out as unique since 1949. Sure, 1962 had one more hot day in May, but June 1962 was perfectly normal. And June 1952 had a a large number of hot days in June, but that followed a normal May. 2011 is remarkable for the duration over which we've been dealt hot day after hot day, as anyone around here knows.



What's the culprit? Day after day the NWS tells us that a high pressure ridge has been parked over the area and shows only a little movement. It bars, until recently, moisture entering from the Gulf of Mexico, our main source of rain. And it bounces cold waves off, not that they'd do much good anyway, when the air is so dry.



Monday: 20 June 2011

Continued Hot and Turtley  -  @ 05:49:28

We've had 18 days 90F and above since June 1 (another day was 89F), and preceding that another 7 such days since May 21. June on average has 10 such days, plus or minus 7, so we're already at more than one standard deviation above the average. The next four days, at least, are expected to be close to 100F, so with our 23rd hot day by Friday June 24, we'll be at #5 for most number of days 90F and above. And with 6 days left to go to the end of the month, it seems likely that we'll break the record of 27 this year. WTF happened to spring?

Until last Wednesday night we'd only had 0.48" rain, about 7% normal, since May 1. Then that night we had some large storms move through and deposit 1.44" rain. On Saturday night another came through, with 1.05" rain. Very welcome, but it did nothing to cool things down, I'm afraid.

Yesterday morning I set out around 8am to specifically and methodically search for box turtles. The morning after a rain seemed like a good time, and in the early morning before it got hot. I found nothing in the first couple of hours, scouring the four or five acres up and down the slopes to SBS Creek, about halfway upstream.

Then I got down to the floodplain, and within 20 minutes found two females.

We've seen the first one before, actually, May 7 2008. At that time she was a good bit farther upstream, across the creek and halfway up the slope to the ridge, probably 300 feet away. Since we traditionally name a turtle upon the first rediscovery, she will now be called Gretl, for no particular reason other than that I'm tired of Kristies, Nikkies, and -forgive me- Courtneys.



She is one of the prettiest box turtles I've found, with her bold gold patterns - of course, even the dullest turtle shines in the wet morning after a rain. Even when I saw her, I knew I had seen her before, but not because of the markings.

It's because of the very strange shape of her carapace. Box turtles generally have a hemispherical, domelike carapace, but hers is definitely humped. Here's yesterday's shot, and for comparison a similar shot from three years ago.



The requisite documentary thumbnails:



The second turtle is a new one, at least I wasn't able to match her up against any of the photos I have since 2005. She was artfully hidden under a clump of grass, on the floodplain a few feet west of the roadcut and about halfway toward Goulding Creek.



Nice discrete markings, and she's probably younger than the average turtle I find. And she has a black plastron, in contrast to Gretl's largely pale one.



So while I was pleased to have at least found two turtles, I think a concerted effort should have turned up more. Maybe the day *after* the day after a storm is a better time. There might be some mushrooms coming up this morning.



Sunday: 12 June 2011

Box Turtles!  -  @ 06:20:26
May 25 must have been some kind of reptile day, since as I walked a little farther up SBS Creek after the snapping turtle discovery, I ran across my first box turtle of the year. It was only clear after looking at the photos that I realized that he (for it was a he) was happily munching on a mushroom.

He's a new one - he matches up with none of the 34 other turtles that either I, or Tom and Gisela next door, have documented. Moreover he turned up in an area that is one where I have found a relatively large number of box turtles. I'm not sure what that means, except that even in a more heavily investigated area I haven't found everything there is to find.



The requisite documentary thumbnails: He's not a very distinctive turtle - the markings are not very intense. I'm counting around 25 scute rings, which is about the most I've ever counted on a turtle, so he's probably relatively old.

There do appear to be some germinating seedlings trying to get a grip on his carapace. This doesn't seem likely to be a successful strategy.



Gisela informs me that she found Maggie on June 9. Maggie was discovered by Tom and Gisela on May 31 of last year, and then again a few weeks later, whereupon she was given her name. We then found that I had actually seen her two years before, Oct 9 2008, down at the floodplain.


Wednesday: 8 June 2011

Jezebels  -  @ 06:56:39
Here's an encounter that's been languishing in the folder for a couple of weeks. Walking up SBS Creek on May 25, I ran across a new thing:



I note that Glenn had a similar encounter, on May 21 2010, where the next feeder creek upstream of Goulding Creek crosses our access road.

This is probably a female preparing a nesting site. Regardless, she had clambered up a five foot near vertical slope in order to reach this creek bank - the trail was clearly visible. It was easy to deduce her course of action - she had almost certainly moved into the feeder creek from Goulding Creek.

This was a smallish and probably fairly young turtle. Her carapace was probably 9 inches long, and I don't count any more than 8 or 10 rings in the scutes. The snapper that has made residence in our ponds up at the house is considerably larger.



If she is nesting, she will lay 20-60 eggs, which is a lot of eggs compared to the box turtles we're more used to. More than likely something, a raccoon probably, is going to find the nest. And then, you know what they say about putting your eggs in one basket.

Her behavior was different from our pond snapping turtle, which we've observed several times a summer over the last six years. We spot the latter occasionally, moving from one pond to another, and when she sees us she scoots - snapping turtles can run fairly fast. This one was completely passive and not unduly disturbed by my intrusion. She didn't resume her activities though, until I had left.

Here's a nice long article on snapping turtles. Interesting about the general lack of aggression and defensive biting behavior when humans encounter them, either in the water or out of it.

Like alligators and some other reptiles, sex determination is dependent on the temperature at which the eggs incubate, with a range of intermediate temperatures (22-28 degC) favoring male development. Female development seems to occur at higher and lower temperatures. I don't know what the soil temperatures are at the depth of the eggs here but given that the last three weeks have been uniformly very hot for May and June, it seems likely that mostly females would result from this clutch. Of course, only one in a thousand will survive to adulthood, so the overwhelming chances are that this snapper is just feeding the predators.


Friday: 3 June 2011

A Peek at June, or, How to be the Life of the Party  -  @ 06:19:31
Everyone wants to know how miserable they're going to be during the month of June, and more importantly: are they really miserable? Or are they just being weenies?

First of all, we'll restrict this to Athens. I'm just not going to do it for everyone - you'll have to do it for your own location.

We'll also restrict this to temperature, and leave rainfall out. Why? What we're doing here depends on the assumption of regularity. If it's 90 degF today, we won't be particularly surprised if it's 90F tomorrow. But it could, if it only would, rain an inch today. That does not mean that it we can be reasonably certain that it will also rain an inch tomorrow.

We could look at the simple average temperature, which is around 77 degF, and that sounds pretty nice. The problem is that it doesn't actually tell us much - a simple average always produces a loss in information. Here, for instance, are two data sets of temperatures taken on three successive days: 99, 100, 101 and 70, 100, 130. The average is 100F for both sets, but these are clearly different data sets with wildly different ranges. Taking the simple average destroyed the difference. (Sure, there's the standard deviation, which will reveal the difference, but if you want to see someone's eyes glaze over, just mention "standard deviation," or "plus or minus.")

I want to get around the loss of information represented by a simple average. I want to cast aside unrevealing differences and zero in on any unusual aspects that are useful in party conversation. For non partiers, this is sort of equivalent to finding the one delicious slice out of a multidimensional pie of general inedibility.

So to accomplish this, I've been playing around with breaking down monthly temperature data into temperature ranges and then counting the number of days in that month for each temperature range. Do this over enough years, and you get a pretty good idea of, for instance, how many days in June will the temperature hit 90 degF or above? When can we reasonably expect to be miserable and not have people laugh at us? More importantly, when can we justifiably laugh at people claiming to be miserable in a perfectly normal June? Here I give you the guidelines for making these important decisions.

Here are the results for June over the years 1949-2010 (except for 2000, which oddly isn't present in the Weather Underground archive.

For the summer months, I chose four temperature ranges into which to sort the daily high temperatures (orange), and three temperature ranges into which to sort the daily lows. These are the column labels.

Rows marked "1" are the statistics that we'll use to get a picture of the normal month of June in Athens. Most of you will be able to look at the table and figure it out, but I'll walk through it anyway.



On average, June has less than 1 day when the daily high hits 100F or above. If we look at the 61 Junes for which we have data, then we see that most of them don't have a day when the temperature hits 100F, but a few have 2 or 3 days with 100F or above. That's what I call the "range" row.

On average, there are 10 days in June when the daily high will hit 90-99 degF. If we look at the range row, it says 0-24, but in reality there are very few Junes with no such days, and also very few with as many as 24 days hitting 90-99 degF.

Rows 1, then, give us a pretty good idea of what to expect, with an idea of the standard deviation encompassing most of the days, and the total range encompassing very abnormal results.

Rows 2 give two examples: a cold June in 1997 (in blue) and a hot June in 1981 (in orange).

In 1997, June had 0 days hitting 100F or above, which isn't very informative. But it had only 1 day hitting 90-99F, and that's very suggestive of an unusually cold June when the average June has 10 such days. We can use the rest of the temperature blocks to confirm this: fairly normal numbers for the 80-89 degF range, but 11 days when the daily high never rose to 80F (the average is 3 days).

Do the daily lows confirm this cold June? It is possible, you know, to have cold days, but mild nights. In this case, in the blue columns, the third temperature block (<=60) tells the story: there were 10 nights when the temperature dropped to 60F or below, and the average number is 3. The range shows that 10 is pretty extreme. So June 1997 was cold both in terms of daily highs and daily lows.

The orange Row 2 shows an example of a hot June in 1981. The temperature never hit 100 or above, but there were 24 days when it hit 90-99F, and the average is 10. Similarly there were 23 nights when the temperature never went below 70F, and there are usually 5 such. June 1981 was extreme in terms of both daily highs and daily lows.

Row 3 is what we know, or is predicted, in the first nine days of the current June.

So far we've hit upper 90s on June 1 and 2, and the prediction is for mid to upper 90s through next Thursday - all 9 days will hit 90 or above. We're already practically at the average by June 9. It is very likely that June 2011 will turn out to be a hot month, since it is very unlikely (although possible!) that the remaining 21 days of June would never go above 89F.

(For those who get further into the statistics, you can use a chi-square analysis to determine whether a particular June is significantly different from the expected (average) June. I've done this, but won't get into it here.)

One of the nice things about this approach is that it breaks things down into a fairly limited number of categories; here there were seven temperature ranges. But notice that only two or three were really informative, and then at that they were very informative. You need all seven to find the two or three, but it's only the two or three that you have to get your head around.

"Yes, it was hot in May, and this is why: there were 13 days when it hit 90 or above, and usually there are only 2 such days." But you needed to look at all seven temperature ranges to find the one that was really different.


Now is there any reason other than self-amusement for doing this? Let us look at four arenas where such an analysis might be of interest:

Benchmarks: yes. A lot of interests will want to know, for instance, the number of days you should expect to hit 90F or above. Tomato plants don't like to fertilize when the temperature gets into the 90s.

Predictions: probably not, unless you get lucky like we did this month and have every day in the first week or so prove to be extreme. Weather can turn on you in a moment.

Hindsight: yes. People's memories are terrible when it comes to comparing a current, seemingly hot June to previous Junes in their experience (and especially the ones outside their experience). May was an even better example, because while May was very significantly hotter, it was essentially a spring month and people will tend to compare hot with hot, rather than May to Mays. So they'll reject May as being hot, because they're thinking of the hottest summer months when they think about what is really hot. But for a May, it was actually quite hot!

Cocktail parties: well. Statistics is probably not a very exciting topic. You're not going to want to get into chi-squares, for instance, unless it's a party with the statistics department. The trick is to mention just one easily digestible statistic that will illuminate the significance of a mutual experience. You might, for instance, just let it drop, in the right circumstances, that there were 13 days in May that hit 90 or above, and usually there are just 2 such days. Now *that's* something most people can get their heads around, and if you're careful to leave it at that, you too can be the life of the party.



Thursday: 2 June 2011

The Month of May  -  @ 05:50:36
It's The Month of May, Number 64 in a series. May was a month of extremes for us - very warm most of the time, and very dry, as we will see. For others, there was extensive flooding and rain, and of course another round of tornados.

Here are the usual temperature anomalies products, at the National Weather Service Climate Prediction Center.

The West and northern midwest continued colder than usual - the west for the second month in a row, and the northern midwest since February. The south and Atlantic states were warmer than usual.

The south had both warmer high and low temperatures, which is intuitive. Much of the northeast extending west through MI and IN and south through NC and TN had much warmer low temperatures at night, than higher temperatures during the day. This odd difference was also true for the west and northern midwest - temperatures didn't warm up much during the day, but neither did they cool down proportionately at night.


We find the National Weather Service Climate Prediction Center's precipitation plots here.

Much of the northern 2/3 of the country received normal or surplus rainfall, but the drought deepened across the southern states from AZ to FL. Surplus rainfall in the midwest, ongoing for several months now, has contributed to extensive flooding in downstream rivers.




For Athens:

Here is a plot of our temperature swings in May, along with precipitation amounts as experienced in Wolfskin:



For the second month in a row we had considerably lower rainfall than normal. We had a period of warmer than usual temperatures, one of colder than usual, and then the last 40% of the month was nearly continually much warmer than usual.

Here is my plot of high temperatures for the month of May in Athens. As usual, the black dots are for the years 1990-2009 (black dots), 2011 (green line), and 2010 (red line).



Our high temperatures were considerably above May's average 80.5, by 3.6 degF. This isn't record breaking, and we didn't break any high temperature records in May. Ironically we did break a 1940 low temperature record on May 5, with 37 degF.

What was nearly record breaking were the number of days 90F and above. May would only have four such days - 2011 had 13 hot days. By another measure there were 13 days more than one standard deviation above the norm (4.9 days normal). What prevented us from having a record breaking hot May was that we did have a period of cooler than normal temperatures, with 8 nights more than one standard deviation below normal (5.7 nights is normal).

In the end, with 13 such days, we had the second highest number of days 90F and above since 1940 - only May 1962 beat us out by one day.

The figure below shows the Athens precipitation data which are official for our area. As usual the green line shows our actual rainfall, the red shows the average accumulation expected. The black dots are rainfall over the last 20 years, the vast river of peach shows the standard deviation.

We never made it above the one standard deviation below the average, meaning that it was dry dry dry. Athens had a total of 0.82", where 4.12" would be normal. Out here in Wolfskin we had even less rainfall - only 0.38". Our spring (MAM) rainfall was 75% of normal, and we are at 81% normal for the calendar year. This was the second driest May since 1940, using the 0.38" rainfall, or the fifth driest, if you use the official Athens 0.82".



The neat prognosticator was right in its prognostication for a warmer April, but it failed in predicting that our local area would be slightly cooler and wetter in May. It is no longer predicting the normal temperatures and rainfall over the next three months.

I'm afraid that it will continue hotter and drier for the next two weeks, at least, across a great deal of the south. The west and north will continue wetter and colder. After that, and for the rest of the summer, the south will continue warmer than usual, but with more normal precipitation. At least that's what they're telling us at the beginning of June ; - )  but it could change.

ENSO stuff:

The ENSO PDF update at this page still chokes on download - wish the Climate Prediction Center at NWS would get that fixed!

La Niña is essentially gone now, after a nearly year-long manifestation, and normal ENSO conditions are in effect, just in time for hurricane season! I suspect our hot and dry weather of the last two months has been due to the tail end of La Niña expressing itself. Before that, the effects were not so noticeable because of the unusually negative Arctic Oscillation that brought cold and wetter weather to the south last December and January.

NOAA's Monthly State of the Climate product for April is now up, and is fascinating reading. Records were broken everywhere, including for the severe tornado outbreaks and wildland fires. May should be appearing soon. Detailed explanations for weather events occurring during whatever month is current can be found for the several sections of the US under the National Overview. There are many interesting weather- and climate-related items to be found here.



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