A31C-3041: Comparing ground‐based and airborne aerosol measurements during the DISCOVER‐AQ Colorado field deployment

Lee Thornhill1 (Kenneth.L.Thornhill@nasa.gov), B.E. Anderson2, L.D. Ziemba2, A.J. Beyersdorf2, E.L. Winstead1, R. Moore2, M. Shook1, C. Corr2, G. Chen2, C. Hudgins1, J.D.W. Barrick1, R. Martin2, C.E. Jordan3, J. Hite4, and A. Nenes4

1 Science Systems and Applications Inc; 2 NASA Langley Research Center ; 3 Univ. of New Hampshire, Durham, NH ; 4 Georgia Tech, Atlanta, Georgia

Understanding the relationship between airborne and ground-based measurements is one of the key questions that the DISCOVER-AQ series of field deployments hope to be able to answer. To address this question, the NASA P-3B systematically conducted vertical profiles over at least six ground sites sampling down to about 1000 feet above ground level (AGL). These data are combined with missed approaches at local airports which provide vertically resolved information between the lowest spiral altitude and the ground-based measurements. During the last DISCOVER-AQ field deployment (Denver, CO; July-August 2014), NASA Langley made aerosol measurements onboard both the NASA P-3B and a mobile laboratory. Coincident measurements included aerosol number concentration, size distributions, along with optical properties such as aerosol scattering, extinction, and hygroscopicity. Two ground sites were sampled, as well as several road trips to sample emissions from feedlots, oil/gas mining operations, and smoke from distant wildfires. We present a comparison between airborne and ground-based measurements made at the two ground sites. Most of the sampling was done in low aerosol concentration environments, away from local sources. Combined, the two ground sites provide at least 30 comparisons between airborne and ground-based aerosol measurements.

Introd

uctio

n and Overview of D

‐AQ CO

Summary and Future Dire

ctions

DISCOVER-AQ CO Overview• The NASA P-3B was equipped with a complex suite of chemical and

aerosol instruments

• A total of 214 spirals were done over 6 ground sites and 108 missed approaches were performed at nearby airports in order to extend the profiles down to the surface

• NASA Langley’s Aerosol Research Group (LARGE) provided a coincident set of aerosol measurements to the ones they had on the NASA P-3B in a mobile laboratory (MACH-2)

Acknowledgement: This research was funded by NASA’s Earth Venture-1 Program through the Earth System Science Pathfinder (ESSP) Program Office. We wish to thank the ESSP Program Office for the support. We also would like to thank the pilots and flight crew of the NASA P-3B through the NASA Wallops Flight Facility for their support and important contributions.

Groun

d Site Location Info

Composite Flight Track Map showing all the flight tracks at each of the 6

waypoints, highlighting the BAO Tower (yellow dashed box) and Platteville

(yellow solid box) ground sites

Platteville Overpass E

xample

BAO Tow

er Overpass E

xample

BAO Tower (Erie, CO, elev 1584 m)• Located 25 miles North of Denver just west of I-25

• 300m instrumented tower, operated by NOAA-ETL

• Records data at 4 levels as well as on a moveable instrumented carriage

• Spent 18 days parked next to the tower (see below)

• Ground data showed excellent agreement with the airborne data

Platteville, CO (elev 1502.8 m, 37 mi NE of Denver)• Area surrounded by fracking operations

• Nearly vacant NOAA monitoring site

• Spent a week there sampling (late on 24 July through morning of 31 July)

• Highest aerosol scattering / extinction were in the morning and due to haze

• Rain washed out the atmosphere late on DOY 209

• Optical measurements and number concentrations show better agreement than the f(RH) calculations

Road Trips24 July 2014• Greeley, CO - sample feedlot emissions from

pre-sunrise to lunch• Greeley, CO – early afternoon sampling of

gas / oil open flaring (didn’t see much)• Up to Wyoming sampling gas & oil fields

29 July 2014• Quick trip to sample the Wiggins and

Magnum feedlots

7 August 2014• Wildfire smoke chasing – north to Cheyenne,

west towards Salt Lake City, ending up in Idaho Falls as the forecasts evolved

8 August 2014• Sawtooth National Forest & Sun Valley, ID

for more smoke chasing from distant fires9 August 2014• Return to BAO tower – mainly vehicle

exhaust sampled, no smoke next morning

07/27/14 – P-3B Science Flight 06• Ground ops were located at

Platteville

• Penn State’s group launched 2 balloons at 12:17 and 14:37

• P-3B Made 3 Spirals (Local Time)1. 12:09 – 12:162. 14:28 – 14:363. 16:02 – 16:08

• Biomass burning aerosols aloft, but none mixed down to the surface

• Possibility that the P-3B sampled their own exhaust (spike in CN)

Soundings• First ozonesonde 

showed a small surface layer with a mixed layer up to 2.3 km

• Four hours later the mixed layer extended from the surface all the way up to about 3.3 km

• Air masses originated over SE Montana

• Particles travelled over the eastern plains and stayed to the east of the urban Denver area

48 hour HYSPLIT back trajectories

First Spiral (12:09 – 12:16) Second Spiral (14:28 – 14:36)

08/02/14 – P-3B Sci Flights 10 (L1 & L2)

• Ground ops was located at BAO Tower

• P-3B Made 3 Spirals (local times)1. 09:18 – 09:352. 11:44 – 12:013. 14:54 – 15:11

• In addition, missed approaches were made at the neighboring Parkland airstrip

• Cleanest aerosol levels morning of the campaign

Soundings (left)• Mixed layer grew during 

the day, extending up to 3.5 km by the final spiral

• Sampled airmass had subsided from the central plains  

HYSPLIT Back Traj. (right)• 48 hours prior HYSPLIT 

suggest the airmasses were at 2500 m AGL

First Spiral (09

:18 –09

:35)

Second

 Spiral (11

:44 –12

:01)

Smoke chasing in the Sawtooth National Forest, ID• Red box – smoke encounter• Green box – likely emissions from passing cars

60000

40000

20000

0

cn37

75 (c

m-3

)

210.0209.0208.0207.0206.0

P-3B overpass data in green triangles

60000

40000

20000

0

cn37

75 (c

m-3

)

216.0215.0214.0213.0212.0

P-3B overpass data in green triangles

Collected data during 18 P‐3B overpasses

• Mixed layer extended to over 3 km

• Better agreement in the optical and CN measurements.

• Offset present in the Platteville f(RH) data, future work will determine why

• Mixed layer had not yet extended down to the surface

• Good agreement with optical and CN measurements at the lowest P-3B altitudes (was only 1800 m due to air traffic control restrictions)

320316312308Theta (K)

5500

5000

4500

4000

3500

3000

2500

2000

1500

GPS

Alti

tude

(m)

Spiral #1

320315Theta (K)

Spiral #2

322320318316314Theta (K)

Spiral #3

Third

 Spiral (14

:54 –15

:11)

• Very low scattering

• Extinction ≈ Scattering therefore very little aerosol absorption

• Better agreement between P-3B and ground later in day as the mixed layer strengthened

• CN concentrations doubled from spiral 2 to spiral 3 due to small particles

• Great agreement in the f(RH) measurements

Initial Summary of Preliminary Observations

• When the P-3B was able to descend into the mixed layer, the NASA LARGE ground based dry scattering measurements agreed very well with the airborne based optical data

• The scanning humidifier system appears to agree better at the BAO tower ground site than at the Platteville ground site

• The dry extinction appears to exhibit a slight offset compared to the dry scattering which cannot be attributed to aerosol absorption, requiring some future evaluation

• The mean P-3B aerosol number concentrations agree well with the ground-based data

• The ambient scattering values were nearly equal to the dry scattering values, due to the low relative humidity observed over the Front Range of Colorado

Future Direction• Submit data to the DISCOVER-AQ archive

• Compare the size distributions from the ground and aircraft

• Determine why the f(RH) data agrees better at the BAO Tower ground site than at Platteville

• Add additional analysis prior to the DISCOVER-AQ Science Team Meeting in May

Coincident LARGE aerosol measurements include:

320310Theta (deg C)

5.5

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

GPS

Alti

tude

(km

)

Sounding 112:17 - 13:51

325320315Theta (deg C)

5.5

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

Sounding 214:37 - 16:09

Measured Parameter P‐3B Instruments MACH‐2 Mobile Lab Instruments

Aerosol Number Concentration(CN)

TSI‐3025 (CN > 4 nm)TSI‐3010 (CN > 10 nm)

TSI‐3775  (CN > 4 nm)

Aerosol Particle Size Scanning Mobility Particle Sizer (SMPS) (0.01‐0.3 µm)

SMPS (0.008‐0.3 µm)

DMT Ultra‐High Sensitivity Aerosol Spectrometer (UHSAS) (0.06‐1.0 µm)

TSI Engine Exhaust Particle Sizer (EEPS) (0.006‐0.52 µm)

TSI Aerosol Particle Sizer (APS) 3321 APS 3321

Total (Dry & Wet) Scattering (450, 550, and 700 nm)

2 x TSI 3563 Nephelometers 2 x TSI 3563 Nephelometers

Aerosol Hygroscopicity System humidifies aerosols to 80% RH Scanning system switches between dry (< 40%), 60%, 70%, and 80% RH in steps

Aerosol Absorption Radiance Research Particle Soot Absorption Photometers (PSAP) (467, 532, and 660 nm)

Thermo Multi‐Angle Absorption Photometer (MAAP) (660 nm)

20000

10000

0

cn37

75 (c

m-3

)

15:04 15:06 15:08 15:10 15:12 15:14

1.60

1.50

1.40

1.30

1.20

1.10

1.00

f(RH

) (80

% &

20%

)

15:04 15:06 15:08 15:10 15:12 15:14

30

20

10

0

Dry

SC

(Mm

-1)

15:04 15:06 15:08 15:10 15:12 15:14

20000

10000

0

cn37

75 (c

m-3

)

11:56 11:58 12:00 12:02

1.60

1.50

1.40

1.30

1.20

1.10

1.00

f(RH

) (80

% &

20%

)

11:56 11:58 12:00 12:02

30

20

10

0

Dry

SC

(Mm

-1)

11:56 11:58 12:00 12:02

12000

10000

8000

6000

4000

2000

0

cn37

75 (c

m-3

)

09:30 09:32 09:34 09:36

1.60

1.50

1.40

1.30

1.20

1.10

1.00

f(RH

) (80

% &

20%

)

09:30 09:32 09:34 09:36

30

20

10

0

Dry

SC

(Mm

-1)

09:30 09:32 09:34 09:36

1.40

1.30

1.20

1.10

1.00

f(RH

) (80

% &

20%

)

14:28 14:30 14:32 14:34 14:36 14:38

40000

30000

20000

10000

0

cn37

75 (c

m-3

)

14:28 14:30 14:32 14:34 14:36 14:38

60

50

40

30

20

10

0

Dry

SC

(Mm

-1)

14:28 14:30 14:32 14:34 14:36 14:3860

50

40

30

20

10

0

Dry

EXT

(Mm

-1)

14:28 14:30 14:32 14:34 14:36 14:38

60

50

40

30

20

10

0

Dry

EXT

(Mm

-1)

12:10 12:12 12:14 12:16 12:18

60

50

40

30

20

10

0

Dry

SC

(Mm

-1)

12:10 12:12 12:14 12:16 12:181.40

1.30

1.20

1.10

1.00

f(RH

) (80

% &

20%

)

12:10 12:12 12:14 12:16 12:18

2400020000160001200080004000

0

cn37

75 (c

m-3

)

12:10 12:12 12:14 12:16 12:18

Collected data during 6 P‐3B overpasses

1.60

1.50

1.40

1.30

1.20

1.10

1.00

f(RH

) 80%

& 2

0%

216.0215.0214.0213.0212.0DOY (with respect to local time)

Red line = P‐3BBlue line = Ground Data

Red line = P‐3BBlue line = Ground Data

60

50

40

30

20

10

0

Opt

ical

Dat

a (M

m-1

)

216.0215.0214.0213.0212.0

Dry Scattering550 nm Ground P-3 Overpass

120

80

40

0

Opt

ical

Dat

a (M

m-1

)

210.0209.0208.0207.0206.0

Dry Scattering550 nm Ground P-3 Overpass

Extinction (Mm‐1)

P‐3B Flight07/27/14

P‐3B Flight07/28/14

P‐3B Flight07/31/14

P‐3B Flight08/02/14

P‐3B Flight08/03/14

1.60

1.50

1.40

1.30

1.20

1.10

1.00

f(RH

) 80%

& 2

0%

210.0209.0208.0207.0206.0DOY (with respect to local time)