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ACT-America: L1 Meteorological and Aircraft Navigational Data

Documentation Revision Date: 2018-06-29

Data Set Version: 1

Summary

This dataset provides aircraft navigational parameters and related meteorological data (often referred to as "housekeeping" data) in support of the research activities for the two aircraft that flew for the NASA Atmospheric Carbon and Transport-America (ACT-America) project. ACT-America's mission spans five years and includes five 6-week intensive field campaigns covering all 4 seasons and 3 regions of the central and eastern United States. Two instrumented aircraft platforms, the NASA Langley Beechcraft B200 King Air and the NASA Goddard Space Flight Center's C-130H Hercules, were used to collect high-quality in situ measurements across a variety of continental surfaces and atmospheric conditions. During these flights, aircraft positional, meteorological, and environmental data are recorded by a variety of instruments. For this dataset, measurements include, but are not limited to: latitude, longitude, altitude, ground speed, air temperature, and wind speed and direction. These data are incorporated into related ACT-America flight-instrumented datasets to provide geotrajectory file information for position, attitude, and altitude awareness of instrumented sampling.

ACT-America's objectives are to study the transport and fluxes of atmospheric CO2 and CH4. At times they flew directly under Orbiting Carbon Observatory-2 (OCO-2) overpasses to evaluate the ability of OCO-2 to observe high-resolution atmospheric CO2 variations. 

This dataset provides results from the Summer 2016 and Winter 2017 campaigns. New data will be added approximately 6 months after the conclusion of a campaign.

This dataset contains 118 ICARTT files and 118 netCDF files, one file of each type per flight.

Figure 1. The ACT-America team on the tarmac with the B-200 King Air and C-130 Hercules NASA aircraft in Shreveport, Louisiana.

Citation

Yang, M.M., J.D. Barrick, C. Sweeney, J.P. Digangi, and J.R. Bennett. 2018. ACT-America: L1 Meteorological and Aircraft Navigational Data. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1574

Table of Contents

  1. Data Set Overview
  2. Data Characteristics
  3. Application and Derivation
  4. Quality Assessment
  5. Data Acquisition, Materials, and Methods
  6. Data Access
  7. References

Data Set Overview

This dataset provides aircraft navigational parameters and related meteorological data (often referred to as "housekeeping" data) in support of the research activities for the two aircraft that flew for the NASA Atmospheric Carbon and Transport-America (ACT-America) project.  ACT-America's mission spans five years and includes five 6-week intensive field campaigns covering all 4 seasons and 3 regions of the central and eastern United States. Two instrumented aircraft platforms, the NASA Langley Beechcraft B200 King Air and the NASA Goddard Space Flight Center's C-130H Hercules, were used to collect high-quality in situ measurements across a variety of continental surfaces and atmospheric conditions. During these flights, aircraft positional, meteorological, and environmental data are recorded by a variety of instruments. For this dataset, measurements include, but are not limited to: latitude, longitude, altitude, ground speed, air temperature, and wind speed and direction. These data are incorporated into related ACT-America flight-instrumented datasets to provide geotrajectory file information for position, attitude, and altitude awareness of instrumented sampling.

Project:  Atmospheric Carbon and Transport (ACT-America)

The ACT-America, or Atmospheric Carbon and Transport - America, project is a NASA Earth Venture Suborbital-2 mission to study the transport and fluxes of atmospheric carbon dioxide and methane across three regions in the eastern United States. Each flight campaign will measure how weather systems transport these greenhouse gases. Ground-based measurements of greenhouse gases were also-collected. Better estimates of greenhouse gas sources and sinks are needed for climate management and for prediction of future climate.

Dataset Visualization: Visualize ACT-America Data

Data Characteristics

Spatial Coverage: Flights over eastern and central United States

Spatial Resolution: Point measurements

Temporal Coverage: Periodic flights occurred during each intensive campaign.

Campaign Beginning and ending dates
Summer 2016 2016-07-11 to 2016-08-29
Winter 2017 2017-01-21 to 2017-03-10
Four more campaigns to be added.  

Temporal Resolution: 1 second

Study Area: (coordinates in decimal degrees)

Site Westernmost Longitude Easternmost Longitude Northernmost Latitude Southernmost Latitude
Eastern and Central United States -106.494 -71.9109 49.1083 28.562

 

Data File Information

There are 118 data files in netCDF (*.nc) version 4 format following CF convensions 1.6. NetCDF files are structured as GeoTrajectory files, where the observations for a flight segment are connected along a one-dimensional track in space, with time increasing monotonically along the track. These files contain data from the respective aircraft’s flight parameters and related environmental data.

There are 118 data files in the ICARTT file format (*.ict). ICARTT files have detailed header information and follow the standards established and summarized in the ICARTT File Format Standards V1.1. https://www-air.larc.nasa.gov/missions/etc/IcarttDataFormat.htm. The files contain the same flight data as the NetCDF files. The flight data are available from the ACT-America P3-B Data System (PDS; for B200 flights) and Housekeeping data (for C130 flights). Files are organized by data system and aircraft (B200 and C130). 

Naming conventions are the same for both file formats. Files are organized by instrument and aircraft for the flight(s) on a given date.

ACT-America file naming convention

File names are standardized by:

project-instrument_aircraft_YYYYMMDD_R#_L#.ext

where:

project = ACTAMERICA

data system = either 'Hskping' or 'PDS'

aircraft = either 'c130' or 'B200'

YYYYMMDD = flight date (UTC)

R# = revision number of data. A higher number indicates a more recent revision.

L# = optional launch number. Some flights had more than one sortie or launch.

ext = file extension. either '.nc' for NetCDF or '.ict' for ICARTT

Companion Files

Additional information on the aircraft platforms deployed by ACT-America is provided in the accompanying files: Platform_B200.pdfPlatform_C130.pdf, and ACTAMERICA_Hskping_Experimenter_Handbook_Jan2011v2.pdf.

 

Data Dictionary:

Variable name Description Units
Flight Information    
Aircraft_Sun_Azimuth aircraft sun azimuth degree
Aircraft_Sun_Elevation aircraft sun elevation degree
Cabin_Pressure cabin pressure mb
Day_of_Year day of year starting Jan 1 UTC d
Dew_Point dew point  Celcius
Drift_Angle drift angle degree
Flight_ID flight identification (aircraft and flight date) NA
GPS_Altitude global positioning system altitude meters
Ground_Speed ground speed meters per second
Indicated_Air_Speed indicated air speed meters per second
Latitude latitude degree north
Longitude longitude degree east
Mach_Number mach number mach
**ManeuverFlag data flag for sampling based on aircraft maneuver NA
Mixing_Ratio H2O mixing ratio g per kg
Part_Press_Water_Vapor H2O vapor pressure mb
Pitch_Angle pitch angle degree
Potential_Temp potential temperature Kelvin
Pressure_Altitude pressure altitude ft
Relative_Humidity relative humidity percent
Roll_Angle roll angle degree
Sat_Vapor_Press_H2O H2O sat vapor pressure of water mb
Sat_Vapor_Press_Ice H2O sat vapor pressure of ice mb
Solar_Zenith_Angle Solar zenith angle degree
Start_UTC start UTC time of day seconds
Static_Air_Temp static air temperature Celcius
Static_Pressure static pressure mb
Sun_Azimuth sun azimuth degree
*time time seconds since 2016-01-01 00:00:00.0 UTC
Total_Air_Temp total air temperature Celcius
Track_Angle track angle degree
True_Air_Speed true air speed kts
True_Heading true heading degree
Vertical_Speed vertical speed m per minute
Wind_Direction wind direction degree
Wind_Speed wind speed m per second
Elevation    
Altitude_AGL_m Aircraft altitude above ground level m
Ground_Elevation_m Ground elevation a.m.s.l. m
Out of Range or Missing    
ulod_flag Data greater than the upper limit of detection -7777
llod_flag Data less than the lower limit of detection -8888
Missing data, nodata, or _FillValue   -9999

* "Flight_ID" and "time" provided only in netCDF files.

** Only available in c130 aircraft files. ManeuverFlag definition: 0 = on ground; 1 = take off; 2 = in-line ascent; 3 = in-line descent; 4 = spiral up; 5 = spiral down; 6 = constant altitude legs; 7 = landing.

Application and Derivation

ACT-America, or Atmospheric Carbon and Transport – America, will conduct five airborne campaigns across three regions in the eastern United States to study the transport of atmospheric carbon. The eastern half of the United States is a region that includes a highly productive biosphere, vigorous agricultural activity, extensive gas and oil extraction and consumption, dynamic, seasonally varying weather patterns and the most extensive carbon cycle and meteorological observing networks on Earth, serves as an ideal setting for the mission.

Each 6-week campaign will accurately and precisely quantify anomalies in atmospheric carbon, also known as Carbon Flux. Accurate carbon flux data is necessary to address all terrestrial carbon cycle science questions. ACT-America addresses the three primary sources of uncertainty in atmospheric inversions — transport error, prior flux uncertainty and limited data density.

ACT-America will advance society’s ability to predict and manage future climate change by enabling policy-relevant quantification of the carbon cycle. Sources and sinks of atmospheric carbon dioxide (CO2) and methane (CH4) are poorly known at regional to continental scales. ACT-America will enable and demonstrate a new generation of atmospheric inversion systems for quantifying CO2 and CH4 sources and sinks.

Figure 2. A schematic showing ACT-America project goals.

ACT-America Goals:

  1. To quantify and reduce atmospheric transport uncertainties.
  2. To improve regional-scale, seasonal prior estimate of CO2 and CH4 fluxes.
  3. To evaluate the sensitivity of Orbiting Carbon Observatory (OCO-2) column measurements to regional variability in tropospheric CO2.

 

ACT-America will achieve these goals by deploying airborne and ground-based platforms to obtain data that will be combined with data from existing measurement networks and integrated with an ensemble of atmospheric inversion systems. Aircraft instrumented with remote and in situ sensors will observe how mid-latitude weather systems interact with CO2 and CH4 sources and sinks to create atmospheric CO2/CH4 distributions. A model ensemble consisting of a mesoscale atmospheric transport model with multiple physics and resolutions options nested within global inversion models and surface CO2/CH4 flux ensembles will be used to predict atmospheric CO2 and CH4 distributions.

Beyond the conclusion of the mission, application of the knowledge gained from this mission will improve diagnoses of the carbon cycle across the globe for decades.

Quality Assessment

Within the data, nodata and out-of-range values are provided in the dataset as described. The table below lists the uncertainties associated with the corresponding instruments.   

Variable name C-130 System B-200 System
Latitude/Longitude/GPS_Altitude 5 meters spherical error probability * 5 meters spherical error probability *
Ground Speed 0.01 m/s * 0.05 m/s *
True_Heading 0.015 deg * 0.07 deg *
Pitch_Angle, Roll_Angle 0.01 deg * 0.01 deg *
Dew_Point 0.2 deg C * 0.5 – 1.0 C (Dynamic Cond,)
Total_Air_Temp 1.5 deg C * +/- 0.6 C (Dynamic Cond.)
Cabin_Pressure 0.25% FS * NA

 *  Uncertainties quoted on instrument spec sheet 

Data Acquisition, Materials, and Methods

ACT-America Overview

The eastern half of the United States, a region that includes a highly productive biosphere, vigorous agricultural activity, extensive gas and oil extraction, dynamic, seasonally varying weather patterns and the most extensive carbon cycle and meteorological observing networks on Earth, serves as an ideal setting for the mission. Flights will concentrate observations on three study domains: Northeast, South-central, and Midwest.

ACT-America will deploy the NASA C-130 and B-200 aircraft to measure atmospheric CO2 and CH4 in the atmospheric boundary layer (ABL) and free troposphere (FT). The mission proposes a total of 70 science flights, 528 hours for the C-130 and 396 hours for the B-200, dedicated in a roughly 3:3:1 ratio among fair weather, stormy weather, and OCO-2 underpass flight patterns.

For fair and stormy weather flights, the C-130 will fly at 3-8 km above ground, collecting in situ measurements in the lower FT, remotely sensed, column-averaged CO2 measurements focused on the ABL, and occasional in situ vertical profiles. The B-200 will primarily sample the ABL. For OCO-2 underflights, the C-130 will fly at 8 km above ground with the B-200 flying in the ABL, both along the OCO-2 flight track. The existing in situ tower CO2/CH4 observing network will be enhanced with five additional tower sites.

The mission will deliver 2-3 times more high-quality lower tropospheric CO2 and CH4 observations than any previous airborne campaign. 

Flight Plans

Data from the fair-weather flights are intended to quantify regional CO2 and CH4 fluxes, and to evaluate fair weather atmospheric C transport processes. The flight pattern is designed to provide extensive sampling of the ABL and lower FT in source/sink regions, meeting the requirements for the fair weather investigation. The C-130 aircraft will fly a U-shape pattern with flight legs perpendicular to the wind, sampling FT and ABL properties downwind of the sources and sinks of C. The C-130 will fly at roughly two times the midday ABL depth, (~3-4 km above ground level (AGL)) with periodic descents and ascents (5 to 10 times in a 6-8-hr flight) to sample the ABL. Although clear sky conditions will be targeted, the C-130 will conduct more profiling if low-altitude clouds interfere with the remote sensors. The B-200 aircraft will partake in two flights per day and will sample a subset of the C-130 flight path focusing on long transects in the ABL with periodic ascents to the FT. The two aircraft will operate over the same time period, but precise coordination is not required.

Data from stormy-weather flights will be used in combination with the data from fair-weather flights to evaluate the transport of C in the mid-latitudes. The flight plans include flight legs parallel to and crossing frontal boundaries at two or more altitudes, and crossing the frontal zone at two or more locations, meeting the requirements for the stormy weather investigation.

The pattern for the OCO-2 inter-comparison flights is designed to obtain data to evaluate the degree to which OCO-2 column CO2 measurements capture true spatial variability in column CO2 content over the continents. Two OCO-2 under flights will be conducted during each campaign and will be selected to cover varying surface reflectance, topography, and aerosol and cloud cover, all possible sources of bias in the OCO-2 measurements. The C-130 flights will be 1000 km in length and flown at 8 km (28 kft) altitude to maximize the fraction of the atmospheric column sampled by the MFLL. The B-200 aircraft will sample a shorter (~360 km) leg in the ABL, often the largest source of variability in column CO2. The B-200 flight will be centered with the C-130 and both aircraft will be vertically stacked during the OCO-2 overpass.

Airborne Instruments

For this dataset, the table below lists the names and model number of the instruments used to collect the flight parameters and environmental data, where applicable.  For detailed information on the instrumentation, see the information in the ACTAMERICA_Hskping_Experimenter_Handbook_Jan2011v2.pdf contained in the companion files in this dataset.

Variable C-130 Data System  B-200 Data System
Latitude Honeywell H-764 Applanix Model 510 V5
Longitude Honeywell H-764 Applanix Model 510 V5
GPS_Altitude Honeywell H-764 Applanix Model 510 V5
Pressure_Altitude derived Derived (Honeywell PPT2)
Ground_Speed Honeywell H-764 Applanix Model 510 V5
True_Air_Speed derived Derived
Indicated_Air_Speed derived NA
Mach_Number Collins ADC_86A (Calculated from Pitot-Static system) Honeywell PPT2 (Calculated from Pitot-Static system)
Vertical_Speed Collins ADC_86A NA
True_Heading Honeywell H-764 Hemisphere DGPS – VS131
Track_Angle Honeywell H-764 Applanix Model 510 V5
Drift_Angle Honeywell H-764 NA
Pitch_Angle Honeywell H-764 Applanix Model 510 V5
Roll_Angle Honeywell H-764 Applanix Model 510 V5
Static_Air_Temp Derived from Total_Air_Temp & Mach_Number Derived from Total_Air_Temp & Mach_Number
Potential_Temp Derived from Static_Air_Temp and Static_Pressure Derived from Static_Air_Temp and Static_Pressure
Dew_Point Edgetech Vigilant 137, 3-stage TEC Edgetech Vigilant 137, 3-stage TEC
Total_Air_Temp Rosemount 102 deiced Rosemount 102 deiced
Static_Pressure Honeywell PPT2 Honeywell PPT2
Cabin_Pressure Measurement Specialties EPRB-2-XU63-30P-/Z1 NA
Wind_Speed Derived from EGI Derived Using Applanix & DGPS Heading
Wind_Direction Derived from EGI Derived Using Applanix & DGPS Heading
Solar_Zenith_Angle derived NA
Aircraft_Sun_Elevation derived NA
Sun_Azimuth derived NA
Aircraft_Sun_Azimuth derived NA
Mixing_Ratio derived Derived
Part_Press_Water_Vapor derived Derived
Sat_Vapor_Press_H20 derived Derived
Sat_Vapor_Press_Ice derived Derived
Relative_Humidity derived Derived

Data Access

These data are available through the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

ACT-America: L1 Meteorological and Aircraft Navigational Data

Contact for Data Center Access Information:

References

ICARTT files have detailed header information and follow the standards established and summarized in the ICARTT File Format Standards V1.1. https://www-air.larc.nasa.gov/missions/etc/IcarttDataFormat.htm