Archive for the ‘weather’ Category

New HMP Weather Station

December 10, 2016

Did you notice the new automated weather station located in the central wetland area at Huntley Meadows Park, Fairfax County, Virginia USA?

The new automated weather station located in the central wetland area at Huntley Meadows Park, Fairfax County, Virginia USA.

13 NOV 2016 | Huntley Meadows Park | new automated weather station

The old weather station, installed and maintained by Virginia Tech University, went offline after 23 September 2016.

The [old] Huntley Meadows weather station was installed to help park personnel manage water levels within the wetland. Source Credit: Huntley Meadows Wetlands Research.

The new station is up-and-running; real-time data is supposed to be available online soon.

The new automated weather station located in the central wetland area at Huntley Meadows Park, Fairfax County, Virginia USA.

13 NOV 2016 | Huntley Meadows Park | new automated weather station

Editor’s Note: The author contacted both the park manager and the natural resource manager; neither person was willing to estimate when the new weather station will go online. Look for a post update when more information is available.

Copyright © 2016 Walter Sanford. All rights reserved.

Snowy scenes along the Hike-Bike Trail

February 7, 2016

The “exposure triangle” has three corners: 1) Aperture; 2) Shutter Speed; and 3) ISO (light sensitivity). When shooting in “Program” mode and Auto ISO, all three corners of the exposure triangle are wildcards set by the camera. In “Aperture Priority” mode and Auto ISO, the user selects the aperture (lens opening) and the camera selects the shutter speed and ISO. In “Shutter Priority” mode and Auto ISO, the user selects the shutter speed and the camera selects the aperture (lens opening) and ISO. Finally, in “Manual” mode the user selects all three settings in the exposure triangle.

All of the photos in this post were shot in “Aperture Priority” mode at ISO 100. That leaves one corner of the exposure triangle for the camera to set: Shutter Speed. At an aperture of f/4 and ISO 100, the camera is set for a relatively wide lens opening and maximum light sensitivity. Ice and snow are very reflective surfaces, so it’s no surprise the camera selected fast shutter speeds to limit the amount of light received by the camera sensor. One upside of this combination of settings: Camera shake was virtually a non-factor!

The following gallery of photos shows views along the Hike-Bike Trail at Huntley Meadows Park, a little more than a week after the “Blizzard of 2016.”

The view along the Hike-Bike Trail at Huntley Meadows Park, Fairfax County, Virginia USA.

4mm (25mm, 35mm equivalent) | f/4 | 1/2000s | ISO 100 | -1 ev

Notice that exposure compensation (ev) was used for most of the photos. In “Aperture Priority” mode at a fixed ISO, exposure compensation affects shutter speed: negative exposure values (ev) make the shutter speed faster, further reducing the amount of light received by the camera sensor; positive exposure values make the shutter speed slower, increasing the amount of light received.

Looking downstream along a creek that crosses the Hike-Bike Trail.

Looking downstream along a creek that crosses the Hike-Bike Trail at Huntley Meadows Park, Fairfax County, Virginia USA.

4mm | f/4 | 1/1000s | ISO 100 | -1 ev

Approaching the observation platform at the terminus of the Hike-Bike Trail. Notice the chromatic aberration in the tree tops at the upper-right corner of the photo.

Looking toward the observation platform at the terminus of the Hike-Bike Trail, Huntley Meadows Park, Fairfax County, Virginia USA.

4mm | f/4 | 1/1600s | ISO 100 | -1 ev

Looking toward the observation platform.

Approaching the observation platform at the terminus of the Hike-Bike Trail, Huntley Meadows Park, Fairfax County, Virginia USA.

4mm | f/4 | 1/1300s | ISO 100 | 0 ev

The central wetland area, as viewed from the observation platform. Notice the observation tower is faintly visible at the far side of the wetlands.

The central wetland area, as viewed from the observation platform at the terminus of the Hike-Bike Trail, Huntley Meadows Park, Fairfax County, Virginia USA.

4mm | f/4 | 1/2000s | ISO 100 | -1 ev

A vernal pool located near the terminus of the Hike-Bike Trail. The pool is mostly covered by ice and snow and somewhat difficult to see in the following photo.

A vernal pool located near the terminus of the Hike-Bike Trail at Huntley Meadows Park, Fairfax County, Virginia USA.

4mm | f/4 | 1/2000s | ISO 100 | -1 ev

A view of the “Mystery Pool.”

A view of the "Mystery Pool," Huntley Meadows Park, Fairfax County, Virginia USA.

4mm | f/4 | 1/1600s | ISO 100 | -1 ev

Heading toward the parking lot at the beginning of the Hike-Bike Trail.

The view along the Hike-Bike Trail at Huntley Meadows Park, Fairfax County, Virginia USA.

4mm | f/4 | 1/500s | ISO 100 | 0 ev

Related Resource: The exposure triangle and exposure compensation.

Copyright © 2016 Walter Sanford. All rights reserved.

Wild Turkey tracks

February 5, 2016

Pattern recognition. The richness of my field experience is often the result of my ability to recognize patterns in nature. For example, while exploring a remote location in the forest at Huntley Meadows Park, I spotted a set of Wild Turkey tracks (Meleagris gallopavo).

I recognized the shape of the turkey footprints in snow as a result of a chance encounter a few years ago, when I was able to tag along with Mr. Kevin Walter — Natural Resource Specialist, U.S. Army Garrison Fort Belvoir — for part of a field survey of birds at Accotink Bay Wildlife Refuge. As we were walking along “Great Blue Heron Trail,” Kevin pointed out a fresh set of Wild Turkey tracks.

Wild Turkey tracks (Meleagris gallopavo) spotted at Huntley Meadows Park, Fairfax County, Virginia USA.

01 FEB 2016 | Huntley Meadows Park | Wild Turkey track

Related Resource: Wild Turkey tracks, one of over 700 spottings by Geodialist on Project Noah. [Note: “Geodialist” is my username on Project Noah.]

Editor’s Note: Sincere thanks to Alonso Abugattas, Ed Eder, and Ben Jessup — a professional naturalist and two excellent amateur naturalists, respectively — for verifying my tentative field identification.

Copyright © 2016 Walter Sanford. All rights reserved.

HMP automated weather station

February 3, 2016

The following photos show the automated weather station located in the central wetland area at Huntley Meadows Park (HMP), Fairfax County, Virginia USA.

An annotated photograph of the weather station features labels for most of the instruments. The tipping bucket rain gauge is shown in the preceding photo, near the left side of the image; the rain gauge is one of several sensors not shown in the annotated photo provided by Virginia Tech University.

The following real-time data is available online: air temperature; wind direction and speed; and current water surface elevation.

Weather_Eng

(sample graphic image)

Air temperature is of particular interest to odonate hunters. 70°F is widely believed to be the minimum body temperature necessary for dragonfly flight. That is, for most species of dragonflies. Autumn Meadowhawk (Sympetrum vicinum) has been observed in flight at temperatures as low as 50°F!

Current water surface elevation may be the most challenging observation to interpret. Two known values help to put the measurement into context: the elevation of the berm is 34.5 feet; the bottom of the concrete box/culvert that serves as the outlet for the wetland is 32 feet. The water level may be higher than 34.5 feet when water breaches the berm. The water level may be lower than 32 feet when evapotranspiration exceeds inflow (precipitation and runoff).

Archived data: See a graph of hourly air temperature for the past two days.

Mean_Temp

(sample graphic image)

Archived data: See a graph of daily precipitation totals for the past month.

Rainfall

(sample graphic image)

Related Resource: My photoblog features a link from the right sidebar to the HMP Weather Station, where the reader will find quick links to all of the resources featured in this post.

Copyright © 2016 Walter Sanford. All rights reserved.

Splish Splash, I was takin’ a bath

July 23, 2014

The following photos show an Eastern Box Turtle (Terrapene carolina carolina) spotted on 22 July 2014 during a photowalk along a small creek that flows through the forest at Huntley Meadows Park.

They are found in most open forested habitats with lots of cover. They seek damp mud or pools when temperatures get too high. Source Credit: Virginia Herpetological Society.

The high temperature was 88°F (31°C), recorded at 3:05 p.m.

Eastern Box Turtle (Terrapene carolina carolina)

Eastern Box Turtle (Terrapene carolina carolina)

Eastern Box Turtle (Terrapene carolina carolina)

Editor’s Note:Splish Splash” is a song performed by Bobby Darin, recorded and released in 1958.

Copyright © 2014 Walter Sanford. All rights reserved.

The End

December 2, 2013

Sadly …

This is the end
Beautiful friend
This is the end
My only friend, the end.
The End, by The Doors

Late-fall/early winter is the end of dragonfly season in the mid-Atlantic region and literally the end for a couple of dead Autumn Meadowhawk dragonflies (Sympetrum vicinum) spotted at Huntley Meadows Park on 15 November 2013. Both carcasses were located along the boardwalk, under a canopy of trees near the observation tower.

The author is unable to identify either the gender or the cause of death for the first individual, lying ventral side up (shown below). At least two scenarios are possible. 1) The dragonfly died of natural cause(s) and was partially eaten afterward. 2) The dragonfly was killed by a predator, most likely a bird, since no other adult dragonfly species are on the wing in mid-November.

Autumn Meadowhawk dragonfly (carcass)

Photo 1. Autumn Meadowhawk dragonfly (carcass, gender unknown).

The second individual (shown below) is a male, as indicated by its coloration and terminal appendages. The carcass looks desiccated, like the dragonfly was freeze-dried. Mike Powell, a fellow wildlife photographer and blogger, observed frost on the boardwalk during the early morning on the 15th.

Autumn Meadowhawk dragonfly (male, carcass)

Photo 2. Autumn Meadowhawk dragonfly (carcass, male).

Copyright © 2013 Walter Sanford. All rights reserved.

The Hardy Boys

November 18, 2013

No, not Frank and Joe Hardy, and their portly pal Chet Morton. Rather I’m referring to three hardy male Autumn Meadowhawk dragonflies (Sympetrum vicinum), shot during a photowalk through Huntley Meadows Park on 11 November 2013, that have survived several nights of below-freezing temperatures. These three guys were among tens of males that I spotted during a three-hour photowalk in the central wetland area. Notice that Male 2 appears to be eating an unknown insect.

Tech Tip: Either mouse-over or tap photos to see captions.

Copyright © 2013 Walter Sanford. All rights reserved.

Fishermen on Accotink Bay

August 26, 2013

Fishermen on Accotink Bay

The preceding photograph shows a view from the shoreline of Accotink Bay. The photo was taken during a photowalk on 16 August 2013 at Accotink Bay Wildlife Refuge, a 1,200 acre preserve located at Army Garrison Fort Belvoir, Fairfax County, Virginia USA.

Copyright © 2013 Walter Sanford. All rights reserved.

Circumscribed Halo

March 16, 2013

An Oval Circumscribed Halo and 22° Halo observed from the Hollin Meadows Swim & Tennis Club, Fairfax County, Virginia USA.

The circumscribed halo is typically a brightly coloured oval around the sun. It is tangential to the inner 22º halo directly above and below the sun and it is brightest there. Sometimes local brightenings of the 22º halo are the only sign of it. Its shape depends very much on the solar altitude. Source Credit: Atmospheric Optics

I used a fence post to block the disc of the Sun and shot the photos at -3 exposure value (ev). The camera LCD was so dark it was like looking at the Sun through welder’s glass! Photo 2 (of 2) also shows a contrail.

Circumscribed Halo Circumscribed Halo

Tech Tips: The following camera settings were used: ISO 100; focal length 4.5mm (25mm, 35mm camera equivalent); -3 ev; aperture f/8; shutter speed 1/2,000 second.

Copyright © 2013 Walter Sanford. All rights reserved.

Great Blue Heron

February 2, 2012

A Great Blue Heron (Ardea herodias) spotted during a photowalk through Huntley Meadows Park, Fairfax County, Virginia USA. This photo was taken soon after the passing of a strong cold front — in a matter of minutes the surface of the water morphed from a reflective glass mirror to the chop shown below.

P1000423-rw2-ver3b_aperture

Tech Tips: The original raw image (RW2) was cropped and adjusted using Apple “Aperture,” and exported as a high resolution JPG image.

Copyright © 2012 Walter Sanford. All rights reserved. www.wsanford.com


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