weather map – NOAA Teacher at Sea Blog

August 22, 2008April 5, 2021

Patricia Donahue, August 22, 2008

NOAA Teacher at Sea
Patricia Donahue
Onboard NOAA Ship Rainier
August 19-23, 2008

Mission: Hydrographic Survey of Bear Cove, AK
Geographical Area: Kachemak Bay, Alaska, 59.43.7 N, 151.02.9 W
Date: August 22, 2008

One of the Rainier’s small boats, also called a launch

Science and Technology Log

Much of today had to do with technology. The small boat I went out on, pictured to the right, was filled with computer equipment. Each day at the survey technology department meetings, I’ve listened but not entirely understood the reports of computer issues on the small boats. This morning I witnessed one such incident. Something didn’t work. Fortunately, there was a work-around and the data collection proceeded smoothly.

I was reminded of the early 18^th century efforts to determine longitude. The problem was so pressing that kings of various countries offered rewards for the development of a clock that could keep time at sea. In 1772, James Cook, for whom Cook Inlet in Alaska is named, sailed with the first marine chronometer. The chronometer was a clock that kept accurate time for the home port. On board Cook’s ship, Resolution, there was another clock that kept local time.

Sonar equipment is lowered into the water.

Since the Earth turns 15 degrees of longitude each hour, by using the difference between the two clocks, seamen would know how far east or west they had traveled. They already knew how to determine latitude with an instrument called a sextant so by using the marine chronometer they could actually plot their coordinates. Now, of course, we take GPS for granted. Many people even have GPS in their cars. These devices and the hand held ones I use with my students at school are accurate to within 4 to 10 meters. Well, the boat I was on today has DGPS, which is even better. It is accurate to within 5 centimeters! With this high-tech equipment, NOAA is able to take very accurate measurements and make very accurate maps.

This graph depicts the velocity of sound through water.

The boat I was on today used multi-beam sonar to determine the depth of the ocean floor. This is similar in concept to the single beam in that ping return-times are used. The multi-beam uses a lot more pings, sometimes as many as 200 per second. In the picture above, the sonar equipment is being lowered into the ocean. I learned that salinity, temperature and depth (which is another way of saying pressure) determine the electrical conductivity and density of the water. These two factors then determine the sound velocity. In the graph, depth is on the Y axis and velocity is on the X axis. Notice the bulge in the plotted line. This represents an area nearer the surface where glacial melt water and ocean water are mixing. The velocity of sound through this water is slower than deeper down where it’s mostly salt water.

This graph displays the pitch, roll, and heave of the boat.

Measurements of salinity, temperature, electrical conductivity, depth and density were taken 27 times today. This data will be used to adjust the sound velocity to get the most accurate picture of the ocean bottom. The movement of the boat also has an effect on the sonar equipment. NOAA is using the moving vessel profiler or MVP to eliminate the interference caused by the boat’s movement. A boat has a pitch, roll and heave. The computer screen to the left shows graphs of these three types of movement. What do you think was happening on the boat at about halfway across the graph? Remember, the boat is “mowing the lawn” as it collects data. Lastly, the tides also affect the data. Upon return to Rainier, the data is processed and also corrected for the effect of the tides.

TAS Donahue gets a chance to drive the launch.

Personal Log

Several crewmembers have tried fishing from the boat and we’ve seen many small boats with fishermen aboard but no one has caught anything. Using the binoculars aboard the small boat today I watched someone land a fish. I think it was a halibut, which makes sense since we’re in Halibut Cove. The most exciting part of the day was driving the small boat. Data was not collected from a small piece of sea bottom so the boat had to make one last pass over it with the sonar equipment. I’ve driven many different vehicles, even a motorcycle, but a boat is different. I couldn’t make it stay straight!

The scariest thing that happened today didn’t happen to us at all. The United States Coast Guard broadcast a message all afternoon over the marine radio. The message would also start with “pan, pan, pan,” which is the appropriate way to begin a distress call. Most of us have heard of “may day” calls. Those are used when there is immediate danger. A “pan” call is more similar to a warning. A boat carrying two adults and one child had not returned as expected and was missing. The Coast Guard was asking all other boaters to keep an eye out for them. I hope they’ve been found and that everyone is okay.

Animals Seen Today

A raft of otters, Common Murres, Marbled Murrelets, and Barrow’s Goldeneye

Vocabulary of the Day

The coxswain is the person who drives the boat.

Challenge Yourself What is 5 cm in inches? What types of movements are pitch, roll and heave?

August 21, 2008April 5, 2021

Patricia Donahue, August 21, 2008

NOAA Teacher at Sea
Patricia Donahue
Onboard NOAA Ship Rainier
August 19-23, 2008

Mission: Hydrographic Survey of Bear Cove, AK
Geographical Area: Kachemak Bay, Alaska, 59.43.7 N, 151.02.9 W
Date: August 21, 2008

Weather Data from the Bridge at 1000 hours
Broken clouds (7/8)
Visibility 11 to 27 nautical miles
Winds calm
Seas 0-1 ft (light breeze) at 9.4˚C
Air pressure 1001.5 millibars and rising slightly
Dry Bulb 12.2˚C, Wet Bulb 11.1˚C
Cumulus clouds between 3000 and 5000 feet

The lines circled in red are the track that the boat follows back and forth in order scan the bottom of the sea. It’s a lot like mowing a lawn! — The track that the boat follows back and forth in order scan the bottom of the sea. It’s a lot like mowing a lawn!

Science and Technology Log

We are anchored in Halibut Cove near a large lagoon too shallow even for the small boats to enter. The nearby mountains have attracted my attention. According to the chart for this area, the two seen off the bow are both 3600 feet high. They have some patches of snow on them. A taller mountain, 4200 feet high, is barely visible in the distance. Nearer the shore some cliffs show evidence of an interesting geological history. Once upon a time, marine sediments collected at the bottom of the sea. The layers built steadily one atop the other, creating organic and clastic sedimentary rocks. The rocks were uplifted to nearly vertical and have eroded. The lighter colored section appears to be limestone but it’s difficult to tell from afar. Due to intense tectonic activity in the area, some of the rock was heated and crushed, causing metamorphism. The section next to what I think is limestone looks to be either a metamorphosed limestone or a batholith. I’m hopeful that someone on board knows more geology than I do!

One of these scans shows a school of fish and the other shows a mound on the sea floor. Can you guess which is which? (Answer: the scan on the left is a mound on the sea floor and the scan on the right is a school of fish.) — One of these scans shows a school of fish and the other shows a mound on the sea floor. Can you guess which is which?

Today I went out on one of the small vessels conducting single beam sonar scanning to determine the depth and shape of the bay bottom. The boat moves across the surface of the sea in straight, parallel lines much like the ones made when cutting the grass with a lawn mower. The lines in the first picture are the rows that the boat “mows.” The sonar pings go down from the bottom of the boat at a rate of 100 per second! The equipment on board measures how much time passes until the ping returns from the bottom. The longer it takes for the sound signal to bounce back, the deeper the water is in that location. The boat also has another scanner similar to what fishermen use to find schools of fish. Look at these two photographs from the scanner. Which is a school of fish and which is a 27 foot high mound on the ocean floor? The depth of the water is in large numbers in the lower left. The numbers farthest to the right are the ocean temperatures. Why is the water colder where the bottom is deeper?

This is a sea otter feasting on a clam! The tiny white spec on its belly is the clam

Personal Log

The screen above with the “mowing the lawn” lines on it clearly shows an airplane making its way back and forth. Of course I had to ask, “Why an airplane icon”? I thought they’d tell me that it was for laughs but no, there is a good reason. The airplane icon’s nose keeps in sync with the GPS and the lines better than the ship icon! The surveyors find it easier to know their position.

Animals Seen Today

Many sea otters – Look closely at the picture to the left. The otter in the picture is eating clam. A shell is balanced on its belly!
Schools of fish under the boat “seen” by the radar
Several types of birds too far away to identify

Vocabulary of the Day

While inputting the weather this morning, I noticed several screens that we did not add data to and rather than skip them, I decided to see what they were about. They were about ice conditions that a ship might encounter and include in a weather report. Here are two new words I didn’t have for ice. A bergy bit is a large piece of floating glacier ice between 100 and 300 square meters in area and showing less than 5 meters but more than 1 meter above sea level. A growler is smaller than a bergy bit. It is larger than 20 square meters in area but less than 1 meter is above the sea surface. Growlers can be transparent, green, or even black in appearance. Since its summer in Alaska, I won’t be seeing any bergy bits or growlers! I also learned that the term iceberg has a precise definition. An iceberg is a piece of ice afloat or aground that shows more than 5 meters above the sea surface. They are described more specifically by their shape.

Challenge Yourself

Kachemak Bay receives a lot of glacial melt water. Surveyors have a difficult time with the radar equipment when they encounter freshwater because the sound waves travel at a different speed through fresh water than they do through salt water. In which type of water, salt or fresh, does sound travel faster? Why?

August 20, 2008April 5, 2021

Patricia Donahue, August 20, 2008

NOAA Teacher at Sea
Patricia Donahue
Onboard NOAA Ship Rainier
August 19-23, 2008

Mission: Hydrographic Survey of Bear Cove, AK
Geographical Area: Kachemak Bay, Alaska, 59.43.7 N, 151.02.9 W
Date: August 20, 2008

Weather Data – Glorious!

Science and Technology Log

A black bear comes to inspect what the land party is up to!

WOW! That says it all. Today’s big excitement was supposed to be the leveling of the tidal gauge and the survey work in the cove. The bigger thrill – and scare – was the bear that approached to within 30 feet of me as I was standing over a benchmark with a leveling rod. Remembering the safety rules about bears, I stayed calm and alerted the others. Then I put down the pole and walked away slowly. Fortunately it was a young and smallish black bear who was easily scared off by the Commander throwing rocks. We were all on our guard the rest of the day. There were several benchmarks to check. Some of the climbing was perilous. All of the work had to be done at low tide. The survey data was collected and I look forward to seeing what’s done with it.

During the afternoon, another emergency drill took place and I was invited to watch. In the scenario, the bridge lost the ability to steer the ship. Control of the vessel had to be made from aft steering, below decks where the rudders protrude from the vessel. By using only a compass and steering orders given in degrees, the helmsman maneuvered the ship. There were no windows or other indicators of the ship’s position. To make matters worse, the scenario called for a loss of communications so a sound powered phone that uses only the energy from the speaker’s voice to operate had to be used instead.

By late afternoon the ship moved to its new anchorage a few miles from Homer. I was invited to watch the lowering of the anchor. The anchor weighs 3500 pounds and there are two of them. Each length of chain weighs 1200 pounds and there are a total of 12 lengths for each anchor. Today we used only 5 sections of chain and 1 anchor. Each section of chain is 90 feet (15 fathoms) long. The anchor is lowered while the ship is in reverse.

Personal Log

My family and my students enjoy a game called geocaching. We’ve started by using hand held GPS devices to find benchmarks and eventually we’ll move on to finding caches and creating our own. I’ve only ever seen old benchmarks but today I saw brand new ones. One of the officers even showed me how they’re made. Benchmarks indicate the exact location and height above sea level of that particular place. The Chief Steward took me to see the food storage facilities. The freezer is enormous! The ship carries enough food to last for 6 months, although the fresh fruits and vegetables only last for one month. They have more food than CostCo!

Animals Seen Today

Stellar’s Jay, Black Bear, and two species of Jelly Fish

Question of the Day

How long is the anchor chain on the Rainier? Provide your answer in feet and fathoms. How much do the anchors and the chain weigh altogether? Why is the boat in reverse when the anchor is dropped?

Challenge Yourself

Go to http://www.geocaching.com and type in your zip code. Identify a benchmark near your home. Find it and take a photograph!

August 19, 2008April 5, 2021

Patricia Donahue, August 19, 2008

NOAA Teacher at Sea
Patricia Donahue
Onboard NOAA Ship Rainier
August 19-23, 2008

Mission: Hydrographic Survey of Bear Cove, AK
Geographical Area: Kachemak Bay, Alaska, 59.43.7 N, 151.02.9 W
Date: August 19, 2008

Weather Data from the Bridge at 1600 hours
Broken clouds (5/8)
Visibility 11 to 27 nautical miles
Winds 230˚ at 6 knots
Seas 0-1 ft (light breeze) at 8.3˚C
Air pressure 1003.5 millibars and falling slightly
Dry Bulb 13.1˚C, Wet Bulb 12˚C
Cumulus and cirrus clouds between 2000 and 3300 feet

Science and Technology Log

Today I recorded the temperature twice, once in the morning and once in the afternoon. The data is written on a sheet and then entered into a specialized computer program. Once saved, the floppy containing the data is placed in a transmitter for delivery via satellite to the National Weather Service. There are few weather stations in the area so the ship is acting as one! The information will then show up on maps as a station model such as the one shown above. My students learn how to code and decode these models and it was awesome to see where the data comes from and how it is delivered.

This is a weather map symbol that shows wind direction (the arm extending from the circle) from the southwest; wind speed (the smaller arm) at 6 knots; temperature at 13.1˚C; dew point and 12˚C; pressure at 1003.5 mb; and cloud cover which is indicated by the shaded circle and shows broken clouds, meaning partly cloudy.

Yesterday and today I also made note of true north and magnetic north. The difference between them was 17 degrees yesterday and 16 degrees today. In Texas a few weeks ago this difference was about 12 degrees. The officer on the bridge told me that there is a lot of interference that accounts for the larger difference here. I was reminded of what I’ve recently learned about the polarity reversals the Earth has undergone throughout its history. According to scientists, the planet is entering a period in which true north and magnetic north will deviate more and more from one another. I read a book I found in the wardroom about the geology of Alaska and discovered that the area we’re in now is mainly sedimentary rock. Through the “big eyes” on the flying bridge I can see a lot of stratification in the rocks.

One of the engineers showed me the engine room. I was able to see the freshwater generator system that makes potable water for the ship. Salt water is “flashed” to its boiling point but not 100 degrees Celsius! This evaporation is done at a very low pressure by creating a vacuum of more than 90% so the boiling point of the water is much lower. This saves energy. The water evaporates, leaving behind the salts and other minerals dissolved in it. The water vapor is condensed and stored in a tank for use by the crew. One of the evaporators can make about 130 gallons of water in an hour and the ship has two of them. (If the water intake is not as salty, such as where we are now due to the glacial melt water, then more water can be generated.) There are also two storage tanks, each holding 8,400 gallons for a total of nearly 17,000 gallons.

The ship uses between 2000 and 3000 gallons per day so the amount stored could last for 5 days if necessary. There are only 53 people aboard. I did the math and realized that the crew is using a lot less water than I thought. Generally, an estimate of water use is 150 gallons per person per day. Not only is the crew careful about water use, some salt water replaces freshwater. For example, the toilets use salt water. Another interesting thing about the evaporators is that they use titanium plates. Titanium is very, very expensive! Back home people are stealing catalytic converters out of cars to recover the titanium in them! Since I teach the gas laws, distillation, and the periodic table, I plan to include a lesson about the evaporators.

Personal Log

Today’s big events were a fire drill and an abandon ship drill. Fortunately I’ve gotten to know the ship fairly well and I was able to get to my assigned muster station in a timely fashion. The newly arrived personnel, myself included, also watched survival videos. Extra survival equipment had to be put away and I volunteered to help. I was able to climb down through hatches into the area where dry goods are stored. I wonder if they’ll let me climb the mast? My fears about seasickness have not been realized due to the fact that we are in very calm water. The bay seems more like a lake! From the ship I can see the Dixon Glacier and the Portlock Glacier. I’m sure they are a lot farther away than they appear! The survey team that went out today reported difficulties in the areas where the glacial runoff enters the bay. I hope I get to go out tomorrow.

Animals Seen Today

Bald Eagle, Otter

Question of the Day

How much fresh water is each person aboard the Rainier using in one day?

Challenge Yourself

Use the internet to find out how many people are aboard a large cruise ship or a large naval vessel. Calculate how many gallons of water they would use. How many freshwater generators would the ship need? How much water would the cruise ship have to store to last for 5 days? Using the station model above, can you determine the relative humidity?