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ACT-America: Profile-based Planetary Boundary Layer Heights, Eastern USA

Documentation Revision Date: 2019-08-26

Dataset Version: 1

Summary

This dataset provides profile-based estimates of the height to the top of the planetary boundary layer (PBL) in meters above mean sea level estimated from meteorological measurements acquired during ascending or descending vertical profile flight segments during NASA's Atmospheric Carbon and Transport - America (ACT-America) airborne campaign. ACT-America flights sampled the atmosphere over the central and eastern United States seasonally from 2016 - 2019. Two 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.

With meteorological data from identified profile flight segments, the height of the first maximum in the potential temperature gradient was used to mark the PBL top height. When the potential temperature gradient did not provide a clear height, gradients in water vapor mixing ratio were used. This method was previously explored within numerous past work (e.g., Seibert et al., 2000; Groenemeijer et al., 2009; Pal et al., 2010). The geographic coordinates for the top height are the center location of the profile flight segment.

There is one file in this dataset in CSV (*.csv) file format and it includes data from the Summer 2016, Winter 2017, Fall 2017, and Spring 2018 campaigns.

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

Pal, S. 2019. ACT-America: Profile-based Planetary Boundary Layer Heights, Eastern USA. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1706

Table of Contents

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

Dataset Overview

This dataset provides profile-based estimates of the height to the top of the planetary boundary layer (PBL) in meters above mean sea level estimated from meteorological measurements acquired during ascending or descending vertical profile flight segments during NASA's Atmospheric Carbon and Transport - America (ACT-America) airborne campaign. ACT-America flights sampled the atmosphere over the central and eastern United States seasonally from 2016 - 2019. Two 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.

With meteorological data from identified profile flight segments, the height of the of first maximum in the potential temperature gradient was used to mark the PBL top height. When the potential temperature gradient did not provide a clear height, gradients in water vapor mixing ratio were used. The geographic coordinates for the top height are the center location of the profile flight segment.

Project: Atmospheric Carbon and Transport – America (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.

Related Dataset:

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

Data Characteristics

Spatial Coverage: Flights over eastern and central United States

Spatial Resolution: Point measurements

Temporal Coverage: Periodic flights took place during each intensive campaign.

Campaign Beginning and Ending Dates
Summer 2016 2016-07-11 to 2016-08-28
Winter 2017 2017-01-21 to 2017-03-10 
Fall 2017 2017-10-03 to 2017-11-13
Spring 2018 2018-04-12 to 2018-05-20

 

Temporal Resolution: Daily

Study Area: (Coordinates are given in decimal degrees.)

Site Westernmost Longitude Easternmost Longitude Northernmost Latitude Southernmost Latitude
Eastern and Central United States 49.108 27.230 -106.494 -73.399

 

Data File Information

There is a single file in this dataset in CSV (*.csv) file format: Profile_Based_PBL_Heights.csv

Missing values are reported as -9999.  

  • For the Summer 2016 Campaign, there are 22 missing points for the B200 and 55 missing for the C130 flights. No other missing data.

PBL is also known as the atmospheric boundary layer (ABL).

User Note:  The PBL top height is reported in m above mean sea level (MSL). To obtain the depth/thickness of the PBL in meters above ground level (AGL), the underlying topography must be used. Ground elevation in m above MSL is available in the related dataset (Yang et al., 2018: https://doi.org/10.3334/ORNLDAAC/1574).

 

Data Dictionary

Column name Units/format Description
date yyyy-mm-dd Sampling date (UTC)
hour hh.hhh Sampling time as decimal hour (UTC)
aircraft   B200 or C130 aircraft
latitude decimal degrees Latitude of the center location of the profile
longitude decimal degrees Longitude of the center location of the profile
PBL_height m MSL Height to the top of the planetary boundary layer (PBL) in meters above mean sea level (MSL) as derived from meteorological measurements acquired during a profile flight at this time and location.

 

Data Center Processing

One *.csv file was compiled from the four originally provided campaign-specific *.txt files.

  • 2016_Summer_B200_C130_Profile_Based_PBL_Heights_v1.0.txt
  • 2017_Winter_B200_C130_Profile_Based_PBL_Heights_v1.0.txt
  • 2017_Fall_B200_C130_Profile_Based_PBL_Heights_v1.0.txt
  • 2018_Spring_B200_C130_Profile_Based_PBL_Heights_v1.0.txt

 

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.

ACT-America Goals

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, missing 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.

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.

Profile-based Planetary Boundary Layer Height

In addition to horizontal flight patterns, profile (vertical) flight segments were flown during ACT-America field campaigns over the three regions. Profiles were collected at six different times: take off, landing, spiral up and down, and en route ascent and descents. These occurred over a variety of flights owing to aircraft speed and mission planning purposes.

Within each identified profile, the location of first maximum in potential temperature gradient was used to mark the PBL top height. When the potential temperature gradient did not provide a clear height, gradients in water vapor mixing ratio were used. The coordinates for the top height are the center location of the profile flight segment.

The PBL top height is reported in m above MSL. To obtain the depth/thickness of the PBL in m AGL, the underlying topography must be used.  Ground elevation in m about MSL is available in the related dataset (Yang et al., 2018).

For future PBL height measurements, PBL will be reported in m above ground level (AGL) instead of PBL top height in m MSL.

Data Access

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

ACT-America: Profile-based Planetary Boundary Layer Heights, Eastern USA

Contact for Data Center Access Information:

References

Groenemeijer, P., Barthlott, C., Corsmeier, U., Handwerker, J., Kohler, M., Kottmeier, C., et al.     (2009). Observations of kinematics and thermodynamic structure surrounding a convective storm cluster over a low mountain range. Monthly Weather Review, 137, 585-602. https://doi.org/10.1175/2008MWR2562.1.

Pal, S., Behrendt, A., Wulfmeyer, V., 2010. Elastic-backscatter-lidar-based characterization of the convective boundary layer and investigation of related statistics. Annales Geophysicae 28, 825-847.

Seibert, P., Beyrich, F., Gryning, S.-E., Joffre, S., Rasmussen, A., and Tercier, P.: Review and intercomparison of operational methods for the determination of mixing height, Atmos. Environ., 34, 1001–1027, 2000.

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