Meredith Salmon: Fun in the Sun with the Sunphotometer, July 19, 2018

NOAA Teacher at Sea

Meredith Salmon

Aboard NOAA Ship Okeanos Explorer

July 12 – 31, 2018

 

Mission: Mapping Deep-Water Areas Southeast of Bermuda in Support of the Galway Statement on Atlantic Ocean Cooperation

Weather Data from the Okeanos Explorer Bridge

Latitude: 28.39°N

Longitude: 65.02°W

Air Temperature: 28.3°C

Wind Speed:  11.8 knots

Conditions: Partly sunny  

Depth: 5092.22 meters

 

Science and Technology Log

“Explorations of opportunity” including NASA Maritime Aerosol Network are conducted on the Okeanos Explorer while underway. The Maritime Aerosol Network is an organized opportunity to collect aerosol data over oceans. Aerosols are liquid or solid particles that can be generated in two ways: natural phenomena (volcano, sand storm, pollination, waves, etc.) or anthropogenic sources (combustion of hydrocarbons, chemical industries, etc.). The open ocean is one of the major sources of natural aerosols of sea-salt aerosols. Sea-salt aerosols, together with wind-blown mineral dust, and naturally occurring sulfates and organic compounds, are part of natural tropospheric aerosols.

Depending on their color, aerosols absorb sunlight in different ways. For instance, soot particles generated from the combustion of hydrocarbons absorb all visible light, therefore generating a rise in atmospheric temperature. Conversely, crystals of salt reflect all visible light and cause climatic cooling. Other studies have shown that their presence is essential for the water cycle: without aerosols, water could not condense in the form of clouds. Therefore, these particles influence the climate balance. In order to achieve this, NASA provides sunphotometers to “Vessels of Opportunity.” These vessels can be either scientific or non-scientific in their nature of operations.

SunFun
Sunphotometer device used throughout the expedition
Garmin
Garmin GPS used to collect coordinates before obtaining sunphotometer reading

How Does This Process Work?

Sunphotometer takes aerosol maritime measurements by using a photometer that is directed at the sun to measure the direct-sun radiance at the surface of the Earth. These measurements are then used to obtain a unit-less parameter: Aerosol Optical Depth (AOD). AOD is the fraction of the Sun’s energy that is either scattered or absorbed (attenuated) while it moves through the Earth’s atmosphere. The attenuation of the Sun’s energy is assumed to be a result of aerosols since the measurements are collected when the path between the sun and the sunphotometer instrument is cloud-free.

Why Is This Process Important?

This collaboration between NOAA and NASA allows for the addition of thirteen more data sets to the Maritime Aerosol Network. Regions in the open ocean are unable to be studied from land-based sunphotometers located on islands, so ships are the only other alternative to compile data. As a matter of fact, satellite based measurements are not as accurate over the ocean compared to hand-held surface measurements. Therefore, the measurements we have been logging serve as ground truth verification for satellites. In addition, the Maritime Aerosol Network allows for the expansion of data sets to the Arctic, thanks to NOAA Ship Ronald H. Brown and other West Coast hydrographic ships.

SunFUN
Tatum and I collecting sunphotometer readings

sunfun 4 (3)

 

Personal Log

Safety is an absolute priority while out at sea, so the team aboard the Okeanos Explorer conducts weekly fire/emergency and abandon ship drills, and a man overboard drill every three months. We completed a man overboard drill today with an orange buoy. Everyone on the ship has designated reporting locations once the alarm sounds and the drill commences. Once you arrive at your assigned area on the ship, you must scan the water for the target and point in its direction once you find it. The fast rescue boat (FRB) is deployed to go retrieve the target and once it is safely back aboard, the drill is complete.

 

MOB
Fast Rescue Boat used during the Man Overboard Drill
man over board 2
Man Overboard Drill on the Okeanos Explorer

Did You Know?

The Mauna Loa Observatory record of solar transmission of sunlight is the longest continuous record in existence!

Resources:

https://www.esrl.noaa.gov/gmd/grad/instruments.html

https://earthobservatory.nasa.gov/Features/Aerosols/page5.php

https://www.esrl.noaa.gov/gmd/obop/mlo/programs/esrl/solar/solar.html

 

Meredith Salmon: Sonars, Sub-bottoms, and Summertime! July 18, 2018

NOAA Teacher at Sea

Meredith Salmon

Aboard NOAA Ship Okeanos Explorer

July 12 – 31, 2018

 

Mission: Mapping Deep-Water Areas Southeast of Bermuda in Support of the Galway Statement on Atlantic Ocean Cooperation

 

Weather Data from the Okeanos Explorer Bridge

Latitude: 29.03°N

Longitude: 62.11°W

Air Temperature: 27.5°C

Wind Speed:  6.38 knots

Conditions: Sunny

Depth: 5167.70 meters

Science and Technology Log

EK 60
SIMRAD EK 60 echo sounder readings – 38kHz frequency is not pictured

In conjunction with the EM302 multibeam sonar, the Okeanos Explorer uses five different frequencies of SIMRAD single beam echo sounders to identify biomass in the water column: an 18 kHz, 38kHz, 70 kHz, 120 kHz, and 200kHz. (38 kHz is not pictured because it is not used in conjunction with the EM302 since the frequencies are too similar and they can cross talk). These sonar systems are common on fishing boats for estimating fish abundance and they’re used for other marine research, as well. In deeper waters, lower frequency sonar is used. Since we are surveying in approximately 5,000 meters of water, the 18 kHz will be used.

Knudsen sub-bottom profiler
3.5 kHz Knudsen sub-bottom profiler data

The third piece of important equipment used during this mission is a 3.5 kHz Knudsen sub-bottom profiler. This technology is used to assist in many surveys since these systems identify and characterize layers of sediment or rock under the seafloor. In sub-bottom profiling a sound source directs a pulse towards the seafloor and parts of this pulse reflect off the seafloor while others penetrate the seafloor. The portions of the pulse that penetrate the seafloor are both reflected and refracted as they pass into different layers of sediment. These signals return towards the surface and can be used to determine important features of the seafloor. For instance, the time it takes for the reflected sound pulses to return to the vessel can be used to determine the thickness and positioning (ex. Sloped or level) of the seafloor. The refracted pulses can provide information about the sub-bottom layers. The variability in density can be used to explain differences in composition (ex. greater density is representative of harder materials). Frequency differences can help scientists obtain optimal results that can be used when collecting data during a survey. Lower frequency pulses can penetrate the seafloor but produce a lower-resolution picture while higher-frequency pulses produce the opposite.

The EM 302, EK60, and Knudsen sub-bottom profiler are all used simultaneously during this seafloor mapping operation.

Personal Log 

Throughout the cruise, one of the NOAA Corps Officers is in charge of planning fun morale events for everyone aboard to participate in. Today, we had a cookout complete with delicious food, music, and corn-hole on the fantail. Everyone had a great time! Additional morale events are planned throughout the rest of the mission so I will post about those later on!

cookout

Corn Hole!
Competitive Cornhole on the Fantail

 

NOAA Squad
Some of the Mapping Team aboard the Okeanos Explorer!

Did You Know?

The earliest technique of bathymetry (depth measurement in water) involved lowering a weighted-down rope or cable over the side of a ship, then measuring the length of the wet end when it reached the bottom. Inaccuracies were common occurrences using this technique because of the bending of the rope caused by deflection from subsurface currents and ship movements.

This technique was replaced in the 1920s by echo sounding, in which a sound pulse traveled from the ship to the ocean floor, where it was reflected and returned.

The multibeam echosounder was invented in the 1960’s.

 

Resources: 

https://www.simrad.com/ek60

https://www.km.kongsberg.com/ks/web/nokbg0240.nsf/AllWeb/1AE8CC56C6F31E51C1256EA8002D3F2C?OpenDocument

Click to access 1259200b5dddf07c4043b97c1d753782183a.pdf