Wednesday, June 22, 2016

RipStik wave and the speed of sound

In the morning I followed up on the weather station visit by demonstrating a dry and wet bulb thermometer. I then demonstrated using a table to determine the relative humidity, heat index, and relative health risk of that heat index. This was followed by making a RipStik wave on poster pad paper in front of the south faculty building.


As the class was seated to the east of the entrance to the building, I opted to lay down the sheets on this slope. I used an uphill run but my turn-around had been sketchy on the east side of the sheets. Wobbly, I came in a tad slow with low amplitude. The initial wave length was 30 cm on an amplitude of only 2 cm. I accelerated up sheet ending on a 60 cm wave length and a 7 cm amplitude. This complicated the analysis.


A student timed the run, I held and drank coffee while riding. The time was 1.75 seconds for what was crudely some 4.75 wavelengths laid down across 248 cm of poster paper. This put an average period at 0.37 seconds, a frequency of 2.71 Hertz, an average wavelength of 52 cm, and a wave speed of 143 cm/s.


Again I used cellular communications to handle the intermittent rain. Once one is out beyond 100 meters, shouting is not possible.

Hansha, Jason head west

John and Gino in the distance by the "B101" Pterocarpus indicus (Narra) tree.

The timer line up

Marsha flagging John. Mayleen, Shirley-Ann, Hansha, Marsha, Jason, Marlinda, Marmelyn, Sucy-ann, and Preston time or record data.

Reset and rerun.

Rain would move in after 200 meters. 250 meters was abandoned and 300 meters, at maintenance was the next stop. Above is roughly 400 meters.

450 meters

1476 feet. The 8 in the second digit would not clear. The wheel is increasingly balky about resetting.

Preston, Marsha, Marlinda, Jason at 450 meters

The long road back to John, Gino. Hard to believe but we could see them rather easily today. Cloudy weather works better than sunny weather. Hearing was easy too. There was a quietness to the campus, and a light easterly breeze was in a laminar flow across campus.


Data and results suggest a speed of sound only about 4 percent below the published value for today.

Pohnpei Weather Service Office visit by physical science class

On the day of the summer solstice in Micronesia, 21 June, the SC 130 Physical Science class most appropriately visited the weather service office in Kolonia.

The visit led off with a brief introduction to the operations center and some of the many roles the station plays. The station, in coordination with the weather service offices on Guam, provides weather information, tide, flash flood watches and warnings, storm watches and warnings, and a number of other services. They also translate critically important weather bulletins into the local language.

Marsha, Hansha, Shirley-Ann, and John listen to the presentation


The 10:00 local time launch of the LMS-6 radiosonde is imminent. Around the world radiosonde's are launched at the same universal time.


The balloon is filled with hydrogen


Getting into position with the radiosonde downwind of the balloon


The balloon will ascend to roughly 10,000 meters


The class shelters from the sun next to the balloon tracking station


Balloon released

Balloon on ascent

Balloon climbing

Pressure, temperature, relative humidity data is relayed by radio signal back to the ground. The tracking station tracks the direction and calculates the distance to the radiosonde to obtain wind speed data aloft.


 Balloon with radiosonde

Marlinda takes notes

Neikaman poses as Marlinda takes notes behind Sucy-Ann

Neikaman

Rain gauge

Inside is a clear plastic cylinder

0.09 inches of rain this morning

Sucy-Ann, Preston, Gino, Neikaman

Digital recording rain gauge relied upon more often during exceptionally heavy rainfall

Cabling connects the unit to the operations center

Min and max thermometers

Dry bulb on the left, wet bulb on the right

The min and max thermometers had to be vibrationally isolated from the blower fan used to drive air over the wet bulb thermometer. The vibration was yielding lower minimum values than the actual minimum temperature

Blower motor switch

New cement pad for the min and max thermometers

The NOAA is one of many service the United States provides to the Federated States of Micronesia

US President Barack H. Obama

Data from the rising weather balloon radiosonde unit

Atmospheric profile from the radiosonde: temperature, pressure, and humidity data

Station air pressure reading

Hansha, Jason, Marsha, Sucy-ann, Shirely-Ann, Neikaman, John, Marmelyn

As always, the class owes a debt of gratitude to the Pohnpei National Weather Service office for their time and hospitality! Nothing makes dry concepts and numbers come to life better than a field trip to a place where those variables and data make a difference in peoples lives.

Wednesday, June 15, 2016

Finding Binky and meters per arcminute of longitude

I hid Binky down deeper in the swale I had used last year. This year I used brown plastic shopping bags, which proved to be better camoflage down low in the paddle grass (Ischaemum polystachyum).

Binky

 The hide location at 6:30 in the morning



Some difference of location opinion for the GPS units. 



Pwisehn malek in the early morning sun

The swale

Brown bag Binky blended right into the brown understory

Starting location for the search for Binky

Gino heads off to the left, John on the right

Joemar and Shirley-Ann head sure-footed in the right direction at a good pace

Sucy-ann, Neikaman, and Marmelyn consult the handout

Neika studies the GPS coordinates

Jason


Marsha

Mayleen compares the GPS to the coordinates on the handout

Heading west 

Hansha and Mayleen

Hansha compares coordinates

Gino watching the longitude numbers roll down as he heads weast

Neikaman navigating for her group


A cat that would follow the group all the way to the hide

Cat

The cat headed west to find Binky


Joemar reaches the edge of the paddle grass sea and stops

The cat would go all the way

Neika, undeterred by the paddle grass


Marmelyn

Not children of the corn but rather physical science students deep in the paddle grass

The paddle grass is deep in the swale


At this point Mayleen and Hansha were effectively on top of my morning track, but they either were not looking for traces of track or did not know to look for track traces in paddle grass. Paddle grass stays bent for more than day where someone has walked and a good tracker could probably pick up a person's passage even two or three days later. 

Neika forges ahead. She would be one of the first to reach the correct coordinates. 

Gino and John coming from the west

Neika and Hansha. Hansha is very close to the Binky hide, but neither would ultimately find Binky.

Hansha and Mayleen

Much of the class converged on the coordinates. Binky is hidden in the grass off to the right.

At this point the class milled around. Only Joemar would realize that at this point the key would be to poke around in the understory.


Hansha and Mayleen


In the afternoon laboratory I would experiment and use the 30 m tape measure in lieu of the wheel. This made the 30 meters more clear, but it meant someone had to stay behind to bring up the other end of the tape. I had the reel on the west end, in retrospect the reel should have been east and the zero end west. That said, the other problem was that one person was left out of the data gathering, babysitting the zero end. Rotating end keepers helped.


Results compare favorably with the estimated 1842 meters per minute value for seven degrees north of the equator. The value is 39 meters low, only about 2% below the expected value.