Update on in-situ tower-based measurements

INFLUX workshopPurdue University

8 August 2011

Outline• CO2/CH4/CO instrument calibration at PSU• Drift tests• Instrument calibration and testing at NIST• Multi-species data examples• Data availability to date• Comparison of co-located Picarros• Deployment readiness update

CO2/CH4/CO instrument calibration

• For CO2, used 4 NOAA tanks for which only CO2 is known for calibration

• For CH4 and CO, we had four tanks, but two sets of two

NOAA_co2=[378.22 416.55 378.61 417.06] ; % ppmNOAA_ch4=[1798.4 2465.6 1790 2461.2] % ppbNOAA_co=[153.3 239.5 145.3 233.7]; % ppb

Repeat of CO2 only calibration28 February 2011

Results are very similar to calibration on 26 January 2011

400 ppm tank: suspect?

Instr 2005

Instr 2006

WMO recommendationsCO2: 0.1 ppmCH4: 2 ppbCO: 2 ppb

CO2/CH4/CO calibration (26 Jan 2011)

Drift testsJan-Feb 2011

• Tested two tanks, alternating between • 5, 10, 5, 10 min, etc • 11 days of data

CO2 (ppm)

CH4 (ppb)

CO (ppb)

Time series for 10-min tank10-sec data10-min averages60-min averages

• Noticeable drift over the 10+ day test, significant for CO2 compared to target accuracy, but drift for CH4 and CO is small compared to target accuracy

• How long (and how often) do we need to sample for zero drift of CO

DOY

CO2 (ppm)

CH4 (ppb)

CO (ppb)

• Calculated means over various periods (5, 10, 30, and 60 min)

• Calculated range of those means during each day

• For CO2 there is slight improvement as period increases; however, for all the range is roughly half of the target (0.1 ppm)

CO2

D

aily

rang

e of

mea

n (p

pm)

DOY

CH4

• For CH4 all the ranges are half of less of the target (2 ppb)

Dai

ly ra

nge

of m

ean

(ppb

)

DOY

CO

• For CO there is marked improvement as the averaging period increases

• For 10-min averaging period, the range is roughly 2.5 ppb (target: 2 ppb for clean air)

Dai

ly ra

nge

of m

ean

(ppb

)

DOY

Allan Variance: CO2σy

2(t)=½ <(yn+1 – yn)2>y(n) is the normalized measure

departure, measured over sample period n, and t is time per sample

period

• Minimum: 5 – 40 min • Plan to a better test by sampling tank

for several hours (CO2 system)

Allan Variance: CH4

Minimum: 8 - 56 min

Allan Variance: CO

Instrument Calibration and Testing at NIST5 – 7 July 2011

• Using three PSU NOAA-calibrated (CO2/CH4/CO) tanks, we performed calibration of 6 NIST Picarros and testing of 2 PSU Picarros– CC339519: 365.34 ppm CO2, 1714.86 ppb CH4, 141.1 ppb CO – CC342919: 395.08 ppm CO2, 1859.23 CH4, 146.4 ppb CO – CC336629: 451.17 ppm CO2, 2117.14 ppb CH4, 254.5 ppb CO

Note that while the calibration tanks for CO2 and CH4 span a good range, two of the tanks measure nearly the same value for CO

• Also tested– CC336482 396.04 ppm CO2, 142.0 ppb CO– NIST tank from NOAA Niwot Ridge

• Inter-test differences are < 0.04 ppm for CO2, < 1.1 ppb for CH4, and < 1.3 ppb for CO.

• Residuals from applying a linear fit are <0.02 ppm for CO2, < 0.12 ppb for CH4 and < 2 ppb for CO.

• Both the CO2 and CH4 residuals are well below the WMO recommendations for those species. The maximum CO residual is approximately equal to the WMO recommendation for clean air.

NIST tank from NOAA uncalibrated Niwot Ridge air

• CO2: 388.26 +- 0.02 ppm (5 instruments)• CH4: 1840.30 +- 0.17 ppb (3 instruments)• CO: 129.1 +- 0.2 ppb (2 instruments)

• PSU CADS instruments measured 388.3 ppm and 388.4 ppm (note: CADS07 has failing pump)

Results (using calibrated NIST systems)

NOAA-calibrated tankCO2: 396.04 ppm CH4: not cal’ed CO: 142.0 ppb

• CO2: 396.03 +- 0.02 ppm (5 instruments)• CH4: 1865.17 +- 0.12 ppb (3 instruments)• CO: 142.1 +- 2.2 ppb (2 instruments)

• PSU CADS instruments measured 396.0 ppm and 396.1 ppm (note: CADS07 has failing pump)

• Peak-to-peak noise of NIST CFADS and CKADS instruments: 0.05 – 0.15 ppm CO2

• Peak-to-peak noise of PSU CADS instruments: 0.4 – 0.7 ppm CO2

Results (using calibrated NIST systems)

Multi-species data July 2011 / 19-20 April 2011

Multi-species data: July 2011

CO2 (ppm)

CH4 (ppb)

CO (ppb)

Green = Rural siteRed = Urban site

19 April 2011

• Green = Rural site• Red = Urban site• Two instruments

measuring CO2 at both sites, but not seen on this scale (it’s a good thing!)

• Top level only is plotted

• Valve sequencer had “issues”

Drive around2100-2300 UTC5-7pm local

20 April 2011

• Green = Rural site• Red = Urban site• Two instruments

measuring CO2 at both sites, but not seen on this scale (it’s a good thing!)

• Top level only is plotted

• Valve sequencer had “issues”

• 300-730 UTC = 11pm-3:30am local

Drive around1300-1500 UTC9-11am local8:00 UTC = 4am local = 0.3

20 April 2011

• Green = Rural site• Red = Urban site• Two instruments

measuring CO2 at both sites, but not seen on this scale (it’s a good thing!)

• Top level only is plotted

• Valve sequencer had “issues”

• 300-730 UTC = 11pm-3:30am local

Drive around1300-1500 UTC9-11am local

Green = multi-species instrument at rural sitePink = CO2-only instrument co-located at rural site

IND Airport Wind Data (19-20 April 2011)

IND Airport Pressure/Temp (19-20 April 2011)

Data Availability (CO2 only instruments)Site01 (CO2 only) Beginning October 2010

Site02 (CO2 only)

Data Availability (CO2/CH4/CO instruments)

SITE01 (CO2/CH4/CO)

SITE02 (CO2/CH4/CO)

Beginning in March 2011

Comparison of co-located CRDS instruments

Tower locations (current and planned)• Site 01: CO2/CH4/CO

Flasks, PROFILE, “Rural”

• Site 02: CO2/CH4/CO Flasks, PROFILE, “Urban”

• Site 03: CO2/CH4/CO (2 instruments) Flasks, PROFILE

• Site 04: CO2/CO, Flasks

• Site 05: CO2/CO, Flasks

• Site 06: CO2/CH4• Site 07: CO2/CH4

PROFILE• Site 08: CO2• Site 09: CO2• Site 10: CO2• Site 11: CO2

07

06

03

01

02

10

08

11

09

04

05

Additional towers: progress towards deployment readiness

• 2 sites in addition to Sites 01 and 02 will be profile sites (4 levels), other 6 sites will measure at top level (100+ m AGL)

• In the process of building the 2 profile sampling systems• Note that the CO2-only instruments will be re-located to

the SouthEast in 2012