ocean mixing – NOAA Teacher at Sea Blog

December 5, 2011March 26, 2021

Jacquelyn Hams: 14 November 2011

NOAA Teacher at Sea
Jackie Hams
Aboard R/V Roger Revelle
November 6 — December 10, 2011

Mission: Project DYNAMO
Geographical area of cruise: Leg 3, Eastern Indian Ocean
Date: November 14, 2011

Weather Data from the R/V Revelle Meteorological Stations

Time: 1045
Wind Direction: 262.60
Wind Speed (m/s): 135.8
Air Temperature (C): 28
Relative Humidity: 79.7%
Dew Point: (C): 24.2⁰
Precipitation (mm): 42.4

PAR (Photosynthetically Active Radiation) (microeinsteins): 1101.5
Long Wave Radiation (w/m2): 410.3
Short Wave Radiation (w/m2): 192.5

Surface Water Temperature (C): 29.8
Sound Velocity: 1545.1
Salinity (ppm): 34.8
Fluorometer (micrograms/l): 0.2
Dissolved Oxygen (mg/l): 2.8
Water Depth (m): 4637

Wave Data from WAMOS Xband radar

Wave Height (m) 1.3
Wave Period (s): 13.2
Wavelength (m): 236
Wave Direction: 280⁰

Science and Technology Log

Ocean Mixing

All about CTDs

A CTD is a standard instrument used on ships to measure conductivity, temperature and depth. Three CTD systems are being used during Leg 3 of Project DYNAMO to measure CTD.

The Revelle deploys the ship’s CTD twice a day to a depth of 1,000 m. The CTD measurements can be viewed on a monitor in the computer room.

The Ocean Mixing group is using a specialized profiling instrument that was designed, constructed, and deployed by the microstructure group at the College of Oceanic and Atmospheric Sciences, Oregon State University. The instrument, called “Chameleon”, measures CTD and turbulence. Chameleon takes continuous readings to a depth of 300 m as it is lowered through the water column. The top of the instrument has brushes to keep the instrument upright in the water and make it hydrodynamically stable so that very precise measurements of turbulence can be achieved. These measurements allow computations of mixing, hence the name Ocean Mixing Group. The instrument freely falls on a slack line to a depth of 300 m after which it is retrieved using a winch. The Chameleon has been taking continuous profiles at the rate of about 150/day since we have been on station and will continue taking measurements for the next 28 days.

The T Chain CTD aboard the ship was also designed by the microstructure group at the College of Oceanic and Atmospheric Sciences, Oregon State University. This instrument measures CTD in the near-surface (upper 10 m) using bow chain-mounted sensors (7 Seabird microcats + 8 fast thermistors). The T Chain takes data every 3 seconds, and although that is not very fast, the data is extremely accurate (within 1/1000th of a degree – 3/1,000th of a degree). The T Chain is mounted on the bow and has been taking measurements continuously since we have been on station. These measurements focus on the daytime heating of the sea surface and the freshwater pools created by the extreme rainfall we have been observing and which is associated with the MJO.

NOAA High Resolution Doppler LIDAR (Light Detection And Ranging) Group

A Brief Introduction to LIDAR

The following introduction to LIDAR systems was provided by Raul Alvarez.

In LIDAR, a pulse of laser light is transmitted through the atmosphere. As the pulse travels through the atmosphere and encounters various particles in its path, a small part of the light is scattered back toward the receiver which is located next to the transmitter. (You may have seen similar scattering off of dust particles in the air when sunlight or a laser pointer hits them.) The particles in the atmosphere include water droplets or ice crystals in clouds, dust, rain, snow, aircraft, or even the air molecules themselves. The amount of signal collected by the receiver will vary as the pulse moves through the atmosphere and is dependent on the distance to the particles and on the size, type, and number of particles present. By keeping track of the elapsed time from when the pulse was transmitted to when the scattered signal is detected, it is possible to determine the distance to the particles since we know the speed of the light.

Once we know the signal at each distance, it is now possible to determine the distribution of the particles in the atmosphere. By measuring how the light was affected by the particles and the atmosphere between the LIDAR and the particles, it is possible to determine things such as the particle velocity which can yield information about the winds, particle shape which can indicate whether a cloud is made up of water droplets or ice crystals, or the concentration of some atmospheric gases such as water vapor or ozone. The many kinds of LIDARs are used in many different types of atmospheric research including climate studies, weather monitoring and modeling, and pollution studies.

Typical lidar signal as a funciton of range — Typical lidar signal as a function of range

Photograph of Ann and Raul inside the LIDAR van.

Raul explains the inner workings of LIDAR aboard the ship. From left to right: 1st photo shows Raul and the LIDAR system; 2nd and 3rd photos display the optical components of the LIDAR; 4th photo is the rotating scanner base.

The four cone-shaped devices are differential GPS antennae used to correct for the motion of the boat.

An integrated motion compensation system is used to stabilize the scanner to maintain pointing accuracy. As you can see from the video below, the scanner maintains its position relative to the horizon while the ship moves.

The slides below represent a Doppler LIDAR data sample from Leg 3 of the Revelle cruise. The images and slides were provided courtesy of Ann Weickmann.

Personal Log

The R/V Revelle is not a NOAA ship. It is part of the University-National Oceanographic Laboratory System (UNOLS) and part of the Scripps Institution of Oceanography research fleet. A few crew members were kind enough to take time from busy schedules to talk with me about their careers. Students may find these interviews interesting especially if they are exploring career options.

The food aboard the Revelle is very good thanks to our cooks, Mark and Ahsha. They are very friendly crew members and always happy to accommodate the diverse eating schedules of scientists who have to work during meal hours.

Meanwhile back on the winch, I am beginning to get the hang of it. I will not say that I am comfortable, because I am always aware that I am in charge of a very expensive piece of equipment. I alternate between operating the winch, operating the computer, standby time (to assist as needed) and free time.

Jackie on the computer in the Hydro lab.

November 21, 2011March 26, 2021

Jacquelyn Hams: 12 November 2011

NOAA Teacher at Sea
Jackie Hams
Aboard R/V Roger Revelle
November 6 — December 10, 2011

Mission: Project DYNAMO
Geographical area of cruise: Leg 3, Eastern Indian Ocean
Date: November 12, 2011

Weather Data from the R/V Revelle Meteorological Stations

Time: 1045
Wind Direction: 2580
Wind Speed (m/s): 2.8
Air Temperature (C): 28
Relative Humidity: 67.6%
Dew Point: (C): 21.4
Precipitation (mm): 40.3

PAR (Photosynthetically Active Radiation) (microeinsteins): 2274.5
Long Wave Radiation (w/m2): 429
Short Wave Radiation (w/m2): 659

Surface Water Temperature (C): 29.7
Sound Velocity: 1545.1
Salinity (ppm): 35.2
Fluorometer (micrograms/l): 65.5
Dissolved Oxygen (mg/l): 3.3
Water Depth (m): 4640

Wave Data from WAMOS Xband radar

Wave Height (m) 1.7
Wave Period (s): 12.8
Wavelength (m): 226
Wave Direction: 195⁰

Science and Technology Log

The Revelle is now on station and will remain in this location for approximately 28 days to conduct measurements of surface fluxes, wind profiles, C-band radar, atmospheric soundings, aerosols, sonar- based ocean profiling and profiling of ocean structure including turbulence. Please note that the exact position and course of the ship will not be posted in this blog until Leg 3 has been completed and the ship is back in port in Phuket, Thailand. Although piracy is not anticipated at the station location, it has been a problem in other parts of the Indian Ocean and the policy is not to publicize the coordinates of the ship.

Surface Fluxes

The Surface Fluxes group measures the amount of radiation and heat into and out of the ocean. There are several dome instruments on the Revelle to measure atmospheric radiation, acoustic and propeller sensors to measure winds and a “sea snake” to measure the sea surface temperature. The term flux is defined as a transfer or exchange of heat. The sum of the terms in the equation below indicates how much radiation is in the ocean. If the sum >0, the ocean is warming. If the sum is <0, the ocean is cooling. Below each term is a photograph of the ship-board instrument used to measure it.

Ocean Mixing

Today I deployed the Los Angeles Valley College drifting buoy. Before leaving Los Angeles, the students in my introductory Physical Geology and Oceanography classes signed NOAA stickers that I placed on the buoy before releasing it into the Indian Ocean. A drifting buoy floats in the ocean water and is powered by batteries located in the dome. The drifting buoys last approximately 400 days unless they collide with land or the batteries fail. The buoy collects sea surface temperature and GPS data that are sent to a satellite and then to a land station where the data can be accessed. Drifting buoys are useful in tracking current direction and speed. Approximately 12 drifting buoys will be deployed from the Revelle during Leg 3 of the Project DYNAMO cruise.

Personal Log

Can you have pirates before a pirate drill?

After we arrived on station, a science meeting was held to provide instructions regarding safety and emergency procedures for mandatory drills such as fire safety, abandon ship, and pirate drills. Drills are typically scheduled once a week and we have already assembled for a fire drill. A pirate drill was scheduled for the following week.

I began my orientation working with the Oregon State University Ocean Mixing Group. My role on the research team is to assist with the operation of the “Chameleon”, a specially designed ocean profiling instrument that is continuously lowered and raised to the surface taking measurements while on station. My job is to rotate between operating the winch (used to lower and raise the instrument) and the computer station. The computer station operator is in constant communication with the winch operator and tells the operator when to raise and lower Chameleon. In addition, the computer operator logs the critical start and end times of each run and keeps track of the depth of the instrument.

Jackie operates the winch. My goal is to keep the instrument safe and have a perfect wind.

I was just beginning to learn to operate the winch when an alarm sounded followed by the words “Go to your pirate stations, this is not a drill, repeat, this is not a drill”. I must admit I was a bit stressed. When I came on this trip, I knew there was a remote risk, but I thought it was extremely remote. Everyone assembled in the designated area and it turns out that a fishing boat was approaching the ship and the Revelle does not take chances if the boat appears to be approaching boarding distance to the ship. There have been two instances where we have assembled for safety following the alarm and the words “This is not a drill, repeat, this is not a drill.” In both cases, fishing boats were too close for comfort. As I began operating the winch, I watched a fishing boat off in the distance for a few days and became more comfortable knowing that the ship is taking extreme caution to protect all on board. All this excitement and before we even had a pirate drill!

But all is well somewhere out here on the equator and the Indian Ocean provides many opportunities for photographing amazing sunrises and sunsets.

Sunrise on the Indian Ocean (photo by Jackie Hams)

Sunset on the Indian Ocean (Photo by Jackie Hams)

November 15, 2011March 26, 2021

Jacquelyn Hams: 7 November 2011

NOAA Teacher at Sea
Jackie Hams
Aboard R/V Roger Revelle
November 6 — December 10, 2011

Mission: Project DYNAMO
Geographical area of cruise: Leg 3, Eastern Indian Ocean
Date: November 7, 2011

Weather Data from the R/V Revelle Meteorological Stations

Time: 1100
Course on Ground
Wind Direction: 195.5⁰Wind Speed (m/s): 2.1
Air Temperature (C): 27.6
Relative Humidity: 81.7%
Dew Point: (C): 24.4
Precipitation (mm): 6.0

PAR (Photosynthetically Active Radiation) (microeinsteins): 517.4
Long Wave Radiation (w/m²): 405.3
Short Wave Radiation (w/m²): 60.5

Surface Water Temperature (C): 28.7
Sound Velocity: 1540.6
Salinity (ppm): 32.45
Fluorometer (micrograms/l): 65.2
Dissolved Oxygen (mg/l): 3.6

Wave Data from WAMOS Xband radar

Wave Height (m) 1.6
Wave Period (s): 18.4
Wavelength (m): 312
Wave Direction: 265⁰

Science and Technology Log

Background

Leg 3 of the Project DYNAMO research cruise began, on November 6, 2011 from Phuket, Thailand at approximately 1430. The DYNAMO Leg 3 research cruise consists of seven scientific groups conducting experiments in the following areas:

Surface Fluxes
Atmospheric Soundings
Aerosols
NOAA High Resolution Doppler LIDAR
TOGA Radar
Ocean Optics
Ocean Mixing

My primary role on this cruise is to work with the Ocean Mixing group led by Dr. Jim Moum from Oregon State University. The Ocean Mixing Group is responsible for sonar measurements of ocean current profiles, high frequency measurement of acoustic backscatter, turbulence/CTD profiling instruments and near surface CTD (Conductivity, Temperature, Depth) measurements. I will be working with other scientific groups as needed and have organized my Teacher at Sea blog to report on daily activities by science group.

Sampling Activities

We have been cruising for a couple of days to the sampling station in the eastern Indian Ocean and are still within the Exclusive Economic Zones (EEZ) of Thailand, India, and other countries. Here is an interesting fact that I learned about the EEZ – it not only applies to resources, but also applies to data collection. What this means to the R/V Revelle, is that the scientists cannot collect data until the ship clears the 200 nautical mile EEZ for the counties. After clearing the EEZ, the science groups can begin data collection.

Atmospheric Soundings

Data collection began on the ship on November 8 and one of the first groups I observed was the Atmospheric Soundings group. This group is responsible for launching radiosondes using helium balloons (weather balloons). A radiosonde is an instrument that contains sensors to measure temperature, humidity, pressure, wind speed, and wind direction. Although the balloons can hold up to 200 cubic feet of helium, on this cruise, each balloon is filled with 30-35 cubic feet of helium. As the radiosonde ascends, it transmits data to the ship for up to 1 ½ hours before the weather balloon bursts and falls into the ocean. The weather balloons have been reaching an average altitude of 16 km before bursting. Approximately 260 weather balloons will be launched during Leg 3 of the cruise.

Watch the video clip below to watch the deployment of a weather balloon.

Computer screen shot of radiosonde data. Temperature is red, relative humidity in blue, wind speed is in green and wind direction is purple.

Ocean Mixing

The Ocean Mixing group began the deployment of XBTs (Expendable bathythermographs) on November 10, 2011. XBTs are torpedo shaped instruments which are lowered through the ocean to obtain temperature data. The XBT is attached to a handheld instrument for launching by a copper wire. Electronic readings are sent to the ship as the XBT descends in the ocean. When the XBT reaches 1,000 meters, the copper line is broken and the XBT is released and falls to the bottom on the ocean.

Here I am getting ready to launch the XBT.

Computer screen shot of thermocline (change in temperature with depth) obtained from XBT instrument. The green shaded curve displays the historical record for comparison.

Personal Log

I arrived in Phuket, Thailand on November 3, 2011 after a 19-hour plane ride. After dinner and a good night’s sleep, I went to the ship to get acquainted with my new home for the next 6 weeks. Select the link below for a tour of the R/V Revelle.

http://shipsked.ucsd.edu/ships/roger_revelle/.

Aboard the R/V Revelle in Phuket, Thailand

The Revelle sailed from Phuket on November 6. As the ship sailed to station, I captured the beauty of the Indian Ocean.