Abstract:

At the mouth of Mobile Bay (Main pass), a Lagrangian experiment was conducted using surface drifters on 09/04/2015. It quantified the flow patterns associated with the ebb tidal plume exiting from Mobile Bay. Each “Davis Drifter” measured: Temperature (degrees C),Latitude (degree decimal), Longitude (degree decimal), Speed (Knots), Satellites (number), Date (DD/MM/YYYY), Time (GMT), Electrical Conductivity(microS), Total Dissolved Solids (mg/L), Salinity (PSU), and Specific Gravity (Dimensionless). Depth of measurements was ~0.5 m. Drifters were deployed with consistent temporal and spatial intervals at the mouth of the bay on ebb tides for 6-24 hours. Other data sets will provide additional data from other drifter releases as well as CTD casting data associated with this project. NOTE: Temperature salinity data on Channel east drifter is bad due to calibration error.

Suggested Citation:

Brian Dzwonkowski, Grant Lockridge, and Steven Dykstra. 2017. Drifter data at Main Pass, Mobile Bay Release 1 (2015/09/04). Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7ZW1HW9

Publications:

Lockridge, G., Dzwonkowski, B., Nelson, R., & Powers, S. (2016). Development of a Low-Cost Arduino-Based Sonde for Coastal Applications. Sensors, 16(4), 528. doi:10.3390/s16040528

Purpose:

The objective of this ongoing research is to identify the influence of fluvial water and it’s suspended particulate matter on coastal regions including the ecosystem and it’s susceptibility to oil. This particular study aims to understand the nature of buoyant freshwater plumes in shallow micro-tidal environments. The drifters were created based on a Davis or “CODE” design (1985). Arduino micro-processors were created to take samples of temperature, salinity, and GPS every minute. The drifters were released systematically across the mouth of Mobile Bay during ebb and slack tides to observe the dispersion and circulation of the discharging water. Profiles were conducted with a CTD, LISST, and ADCP and were compared to long term monitoring stations for ambient conditions.

Data Parameters and Units:

Stations locations in Main Pass, Mobile Bay: Shoal west (30 14.6174 88 04.1607) Shoal center (30 14.3670 88 03.6461) Shoal east (30 14.1383 88 03.1365) Channel west (30 13.7800 88 02.3971) Channel center (30 13.6678 88 02.1323) Channel east (30 13.5469 88 01.8825). Each “Davis Drifter” measured: Temperature (C), Latitude(degree decimal), Longitude(degree decimal), Speed (Knots), Satellites(number), Date(DD/MM/YYYY), Time (GMT), Electrical Conductivity(microS), Total Dissolved Solids (mg/L), Salinity (PSU), and Specific Gravity (Dimensionless).

Methods:

The standard resolution of the Arduino Mega 8 bit processor is 1023, which when applied to the range of the temperature sensor (-20 to 133 °C) is approximately 0.25 °C. Conductivity resolution of 0.01 µS over a range of 0.07-99.99 µS with the setup described. The temperature and salinity data RMS errors of 0.154oC and 1.35 psu for the environmental conditions tested in.

Instruments:

The design of the sonde was based around the Arduino platform (either Mega 2560 or Uno) with a data logging attachment (either the Adafruit Ultimate GPS Logger Shield (AUGPSS) or the Adafruit Data Logging Shield) and an Atlas EZO EC microchip (EC) was installed in the available space. The EC microchip received a voltage from the conductivity probe, which was converted into conductivity, salinity, specific gravity, and total dissolved solids. Temperature and conductivity readings were recorded to the SD card as a .CSV file. Prior to deployments, temperature was calibrated to a YSI 2030 pro model handheld sonde, and conductivity was tow point calibrated using 12880 µS and 80000 µS standard solutions.

Error Analysis:

Individual Files: