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.

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.