Delta-X: In situ Beam Attenuation and Particle Size from LISST-200X, Spring 2021

This dataset provides in situ measurements of beam attenuation coefficient at 670 nm (m-1), average suspended particle size (um), particle size distribution (uL L-1), and water temperature (degrees C) in surface waters (~0.5 m) collected during the Delta-X Spring 2021 campaign. Measurements were made in the Atchafalaya and Terrebonne Basins on the southern coast of Louisiana from 2021-03-25 to 2021-04-22. During the field campaign, measurements were collected in multiple channels of varying width (from a few meters to >100m), near Delta-X intensive study sites, in open bays and lakes, and at a few locations in the nearshore Gulf of Mexico. For each in situ collection, the measurements were collected using Sequoia Scientific Laser In-Situ Scattering and Transmissometer instrument (LISST-200X).

There are two data files in comma-separated (.csv) format with this dataset.

 

This dataset provides in situ measurements of beam attenuation coefficient at 670 nm (m^-1), average suspended particle size (µm), particle size distribution (µL L^-1), and water temperature (degrees C) in surface waters (~0.5 m) collected during the Delta-X Spring 2021 campaign. Measurements were made in the Atchafalaya and Terrebonne Basins on the southern coast of Louisiana from 2021-03-25 to 2021-04-22. During the field campaign, measurements were collected in multiple channels of varying width (from a few meters to >100m), near Delta-X intensive study sites, in open bays and lakes, and at a few locations in the nearshore Gulf of Mexico. For each in situ collection, the measurements were collected using Sequoia Scientific® Laser In-Situ Scattering and Transmissometer instrument (LISST-200X).

Project: Delta-X

The Delta-X mission is a 5-year NASA Earth Venture Suborbital-3 mission to study the Mississippi River Delta in the United States, which is growing and sinking in different areas. River deltas and their wetlands are drowning as a result of sea level rise and reduced sediment inputs. The Delta-X mission will determine which parts will survive and continue to grow, and which parts will be lost. Delta-X begins with airborne and in situ data acquisition and carries through data analysis, model integration, and validation to predict the extent and spatial patterns of future deltaic land loss or gain.

Acknowledgments

This work was supported by the NASA Earth Venture Suborbital-3 (EVS-3) program, grant number NNH17ZDA001N-EVS3 and JPL Research and Technology Development.

Spatial Coverage: Atchafalaya and Terrebonne Basins, southern coast of Louisiana, USA

Spatial Resolution:  Point measurements

Temporal Coverage: 2021-03-25 to 2021-04-22

Temporal Resolution: Multiple measurements on each sampling day

Site Boundaries: Latitude and longitude are given in decimal degrees.

Site	Westernmost Longitude	Easternmost Longitude	Northernmost Latitude	Southernmost Latitude
Atchafalaya and Terrebonne Basins	-91.66	-90.14	29.79	28.99

Data File Information

This dataset includes a total of 2 datafiles in CSV format:

DeltaX_LISST200X_Spring2021.csv provides water temperature, beam attenuation coefficient at 670 nm, and average suspended particle size, along with their respective standard deviations. DeltaX_LISST200X_PSD_Spring2021.csv provides the corresponding particle size distributions, along with their respective standard deviations. Missing numeric values are indicated by -9999.

Table 1. Data dictionary for DeltaX_LISST200X_Spring2021.csv.

Variable	Units	Description
basin		Atchafalaya or Terrebonne
site_id		Name of site. See Section 5: Data Acquisition, Materials, and Methods for site_id naming convention.
campaign		Name of Delta-X campaign, e.g. Spring_2021
latitude	Decimal degrees	Latitude of sampling location
longitude	Decimal degrees	Longitude of sampling location
date		Time of sampling in YYYY-MM-DD format
time		UTC time of sampling in HH:MM:SS format
temperature	Degrees C	Average temperature
SD_temperature	Degrees C	Standard deviation of temperature
c_670	m-1	Average beam attenuation coefficient at 670 nm
SD_c_670	m-1	Standard deviation of beam attenuation coefficient at 670 nm
D_avg	um	Average suspended particle size
SD_D_avg	um	Standard deviation of suspended particle size

 

Table 2. Data dictionary for DeltaX_LISST200X_PSD_Spring2021.csv.

Variable	Units	Description
basin		Atchafalaya or Terrebonne
site_id		Name of site. See Section 5: Data Acquisition, Materials, and Methods for site_id naming convention.
campaign		Name of Delta-X campaign, e.g. Spring_2021
latitude	Decimal degrees	Latitude of transect start.
longitude	Decimal degrees	Latitude of transect start.
date		Date of sampling and measurement in YYYY_MM_DD format
time		UTC time of sampling in HH:MM:SS format
Diam_size	uL L-1	average estimated volumetric particle concentration for particles of size (size), where size is in um.
Diam_ size_SD	uL L-1	standard deviation of estimated volumetric particle concentration for particles of size (size), where size is in um.

During the Delta-X Campaigns, in situ measurements of beam attenuation coefficient at 670 nm (m^-1), average suspended particle size (µm), and particle size distribution (µL L^-1) in surface waters were collected at a number of sites across the Atchafalaya and Terrebonne basins. These sites spanned large and small channels at locations chosen to cover a representative range of suspended solids concentration from a variety of hydrodynamic and physical settings typically encountered across the Atchafalaya and Terrebonne basins. This dataset is used to inform and validate Delta-X’s sediment transport models. These measurements made at discrete locations are paired with other measurements of total suspended sediment concentration made on discrete water samples, and with measurements of in situ water-quality indicators, and in situ and airborne water reflectance (all provided as separate data sets). These location- and time-specific measurements are compared to numerical models to calibrate and validate its parameters. The models quantify the mesoscale (i.e., on the order of 1 ha) patterns of soil accretion that control land loss and gain and predict the resilience of deltaic floodplains under projected relative sea-level rise. Understanding and mitigating the impact of the relative sea-level rise on coastal deltas is urgent. If ignored, relative sea-level rise will very soon have devastating consequences on the livelihood of the half-billion people that live in these low-lying coastal regions.

Each day, before and after deployment, clean-water background measurements were acquired with the instrument using Milli-Q water to check for optimal performance of the instrument. The instrument was pressure-tared on the boat deck before deployment. The instrument was lowered from the side of the boat and deployed so that it is perpendicular to the current and the water is flowing as unobstructed as possible through the optics end of the instrument. The data were collected at the surface for about two minutes at a rate of 1 Hz, averaged and a standard deviation of the measurements was calculated.

Study Sites

The Spring 2021 campaign collected measurements from the LISST-200X at different locations across the Atchafalaya and Terrebonne Basins (Figure 2). Each sampling site was named using a combination of abbreviations provided in Table 3 as follows: BBB_MMDD_TN where BBB is the abbreviation for the basin (WLD or TB), MMDD is the month and day of 2021 (e.g., 0327 for March 27, 2021), T is the abbreviation for the station type (F for Full station, D for Dry station, and B for Basic station), and N is the sequential number of the station of each type sampled that day (B1 for first basic station, S1 for first full station, S2 for second full station, etc.).

Figure 2. LISST-200X measurement sites for the Spring 2021 Delta-X campaign.

Table 3. LISST-200X site naming

Abbreviated Site name	Full Site Name
WLD	Atchafalaya Basin (including Wax Lake Delta)
TB	Terrebonne Basin
S	Full station (Water samples for TSS was collected along with water reflectance, measurements from the LISST, and water-quality indicators from ProDSS probe)
D	Dry stations (No Water samples for TSS was collected, but measurements of water reflectance, from the LISST, and water-quality indicators from ProDSS probe were collected)
B	Basic station (only measurements of LISST, and water-quality indicators from ProDSS probe were collected)

 

LISST-200X Operation

Each in situ measurement was collected directly by lowering the LISST-200X from the side of the boat and keeping it submerged at about 0.5 m beneath the surface (Figure 1). Measurements were collected at a rate of 1 Hz for a duration of about two minutes before retrieving the instrument. Data from the LISST-200X were retrieved and exported as individual casts using the commercial Sequoia Scientific® LISST-SOP200X software. Each cast was then processed in MATLAB® to generate the products of interest including in situ beam attenuation coefficient at 670 nm, suspended particle size distribution, average particle size, and water temperature. In the processing, the measurements collected at the surface for about two minutes were averaged and the standard deviation was calculated.

Not provided.