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 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.

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.