ARM TR-072

> Continuous Measurements of Atmospheric Carbon Monoxide at the ACRF
> Southern Great Plains Site
>
> April 2006
>
> S.C. Biraud
>
> Work supported by the U.S. Department of Energy,
>
> Office of Science, Office of Biological and Environmental Research

# Contents {#contents .Heading-Front}

[1 General Overview 1](#general-overview)

[2 Contacts 1](#contacts)

[3 Deployment Locations and History
2](#deployment-locations-and-history)

[4 Near-Real-Time Data Plots 2](#near-real-time-data-plots)

[5 Data Description and Examples 2](#data-description-and-examples)

[6 Data Quality 5](#data-quality)

[7 Instrument Details 6](#instrument-details)

# Tables {#tables .Heading-Front}

[1 Primary standards specifications. 3](#__RefHeading___Toc133302881)

[2 Quality Control flags value. 3](#__RefHeading___Toc133302882)

[3 "Warning" and "bad" quality control flag scheme.
4](#__RefHeading___Toc133302883)

# General Overview

The Southern Great Plains (SGP) Carbon Monoxide (CO) system provides
high-precision atmospheric concentration measurements of CO mixing ratio
(ppbv dry air) every 10 minutes in air collected at 60 meters above
ground level. Concentrations measurements are based on the principle
that carbon monoxide absorbs infrared radiation at a wavelength of 4.6
µm.

# Contacts

## Mentor

Sébastien C. Biraud, Research Associate

Geochemistry Department

Earth Science Division

Mail Stop: 90R1116

Lawrence Berkeley National Laboratory

1 Cyclotron Road

Berkeley, CA 94720

Phone: 510-486-6084

Fax: 510-486-5686

Email: <scbiraud@lbl.gov>

Web: <http://esd.lbl.gov/ESD_staff/biraud/>

Marc L. Fischer, Staff Scientist

Atmospheric Sciences Department

Environmental Energy Technologies Division

Mail Stop: 90K

Lawrence Berkeley National Laboratory

1 Cyclotron Road

Berkeley, CA 94720

Phone: 510-486-5539

Fax: 510-486-5928

Email: <mlfischer@lbl.gov>

Web: <http://eetd.lbl.gov/env/mlf/>

## Instrument Developer

Lawrence Berkeley National Laboratory (LBNL) staff built the system.

Thermo Electron Corporation is the vendor CO gas analyzer model 48°C
(see <http://www.thermo.com/com/cda/product/detail/1,1055,14684,00.html>
for product description).

For instrument repair and maintenance contact:

Thermo electron Corporation

Service: Air Quality Instruments

27 Forge Parkway

Franklin, MA 02038

Phone: 1-866-282-0430

Fax: 1-508-520-1460

# Deployment Locations and History 

The CO system is located at the base of the 60-meter tower (36.607 ºN,
97.489 ºW, and 314 meters above sea level) at the Atmospheric Radiation
Measurement (ARM) Climate Research Facility (ACRF) SGP Central Facility.

The system was deployed on May 25, 2005, and operates continuously,
except for occasional power outages and scheduled maintenance.

# Near-Real-Time Data Plots

**Data stream 1**: Quick views of the CO system data for yesterday are
available at

<http://co2anal.lbl.gov/worldview/co-yest.html>

**Data stream 2**: Quick views of the CO system data for the past week
are available at

<http://co2anal.lbl.gov/worldview/co-week.html>

# Data Description and Examples

## Data File Contents

The data are presented in two levels of processing: a1 and b1. Each
level of processing has a directory, which is named accordingly. For
more detailed information on processing, please see Section 6.1.

In summary:

-   Directory 'a1': sgpcoC1.a1.YYYYMMDD.HHMMSS.asc. First level of
    processing where raw data are time stamped every 5 seconds.
    "YYYYMMDD" denotes year, month, day of the file. "HHMMSS" denotes
    hour, minute, and second of the file. All data are in ASCII format.

-   Directory 'b1': sgpcoC1.b1.YYYYMMDD.HHMMSS.cdf. Second level of
    processing where data are quality checked and corrections for offset
    and span are applied.

### Primary Variables and Expected Uncertainty

The CO system provides carbon monoxide mixing ratio in dry air in ppbv
units. Uncertainty of the instrument is estimated to be on the order of
5 ppb.

#### Definition of Uncertainty

Uncertainties in the measurements obtained under well-mixed conditions
are typically dominated by random noise from atmospheric turbulence and
the instrument. The data processing software is designed to provide
diagnostic variables to identify the sources of uncertainty that affect
the measurements.

Samples are bracketed by two secondary calibration standards. These
standards have been calibration against two primary National Oceanic and
Atmospheric Administration (NOAA) Earth System Research Laboratory
(ESRL) certified standards. Concentrations of these primary standards
are shown in Table 1.

  --------------------------------- ---------- ---------- ------------- -------------------- -------------- ----------
  []{#__RefHeading___Toc133302881                                                                           
  .anchor}**Table 1. Primary                                                                                
  standards specifications**                                                                                

  **Manufacturer**                  **Type**   **Serial   **Mixture**   **Concentrations**   **Performed    **Date**
                                               \#**                                          by**           

  SCOTT MARRIN                      150A       CA05962    CO in air     95±1 ppb             NOAA - D.      1-Dec-03
                                                                                             Kitzis         

  SCOTT MARRIN                      150A       CA05909    CO in air     292.5±2.9 ppb        NOAA - D.      1-Dec-03
                                                                                             Kitzis         
  --------------------------------- ---------- ---------- ------------- -------------------- -------------- ----------

### Secondary/Underlying Variables

This section is not applicable to this instrument.

### Diagnostic Variables

The diagnostic variables are listed in the table for Data Quality Flags,
Section 5.1.4.

### Data Quality Flags

Output files include quality control (qc) flags. Almost every variable
\'x\' has a qc flag named \'qc_x\'. The values of qc flags values and
definitions are shown in Tables 2 and 3.

  --------------------------------- ----------------------------------------------------
  []{#__RefHeading___Toc133302882   
  .anchor}**Table 2. Quality        
  Control flags value**             

  **QC Value**                      **Relevant Condition**

  0                                 value not suspect.

  1                                 value in a range that might point toward a problem.

  2                                 value below minimum or 2 above maximum threshold.
  --------------------------------- ----------------------------------------------------

+-----------+------------+-------------------------+------------------+
| []{#      |            |                         |                  |
| __RefHead |            |                         |                  |
| ing___Toc |            |                         |                  |
| 133302883 |            |                         |                  |
| .ancho    |            |                         |                  |
| r}**Table |            |                         |                  |
| 3**.      |            |                         |                  |
| **        |            |                         |                  |
| "Warning" |            |                         |                  |
| and "bad" |            |                         |                  |
| quality   |            |                         |                  |
| control   |            |                         |                  |
| flag      |            |                         |                  |
| scheme**  |            |                         |                  |
+-----------+------------+-------------------------+------------------+
| **qc Flag | **Units**  | **"Warning" Condition** | **"Bad"          |
| A         |            |                         | Condition**      |
| ssociated |            |                         |                  |
| to        |            |                         |                  |
| V         |            |                         |                  |
| ariable** |            |                         |                  |
+-----------+------------+-------------------------+------------------+
| CO        | ppb        | 50 \< CO \< 60          | CO \< 50         |
|           |            |                         |                  |
|           |            | 600 \< CO \< 800        | CO \> 800        |
+-----------+------------+-------------------------+------------------+
| int_temp  | Deg.       | 25 \< int_temp \< 30 40 | int_temp \< 25   |
|           | Celsius    | \< int_temp \< 45       |                  |
|           |            |                         | int_temp \> 45   |
+-----------+------------+-------------------------+------------------+
| ch        | Deg.       | 35.0 \< chamber_temp \< | chamber_temp \<  |
| amber_tem | Celsius    | 42.4                    | 35.0             |
| p         |            |                         | chamber_temp \>  |
|           |            | 47.5 \< chamber_temp \< | 55.0             |
|           |            | 55.0                    |                  |
+-----------+------------+-------------------------+------------------+
| agc       | Hz         | 1.90e5 \< agc \< 1.95e5 | agc \< 1.9e5 agc |
|           |            | 2.05e5 \< agc \< 2.1e5  | \> 2.1e5         |
+-----------+------------+-------------------------+------------------+
| p         | Torr       | 790 \< pres_TE48C \<    | pres_TE48C \<    |
| res_TE48C |            | 800 820 \< pres_TE48C   | 790 pres_TE48C   |
|           |            | \< 830                  | \> 830           |
+-----------+------------+-------------------------+------------------+
| f         | LPM        | 0.40 \< flow_TE48C \<   | flow_TE48C \<    |
| low_TE48C |            | 0.45 0.55 \< flow_TE48C | 0.40 flow_TE48C  |
|           |            | \< 0.60                 | \> 0.60          |
+-----------+------------+-------------------------+------------------+
| pre       | Torr       | 785 \< pres_control \<  | pres_control \<  |
| s_control |            | 795 805 \< pres_control | 785 pres_control |
|           |            | \< 815                  | \> 815           |
+-----------+------------+-------------------------+------------------+
| flo       | LPM        | 0.40 \< flow_control \< | flow_control \<  |
| w_control |            | 0.45 0.55 \<            | 0.40             |
|           |            | flow_control \< 1.00    | flow_control \>  |
|           |            |                         | 1.00             |
+-----------+------------+-------------------------+------------------+
| dpt       | Deg.       | -15 \< dpt \< -10       | dpt \> -10.0     |
|           | Celsius    |                         |                  |
+-----------+------------+-------------------------+------------------+

### Dimension Variables

Each variable has dimensions included in the data files.

## Annotated Examples

The variable for CO mixing ratio is co. Typical daytime values are 60
ppb \<co\< 600 ppb. The corresponding qc variable is qc_co
(dimensionless), which when normal has a value of zero.

## User Notes and Known Problems

The instrument has provided high quality data for a large fraction
(\>90%) of its operating lifetime. Occasional loss of data has occurred
due to loss of power communications or instrument malfunction. All data
users are strongly urged to review the quality reports, which describe
the intermittent problems and changes to sensor and the data processing,
then refer further questions to the instrument mentor.

## Frequently Asked Questions

Where do I get more information?

Contact the instrument mentors at <scbiraud@lbl.gov> or
<mlfischer@lbnl.gov>.

# Data Quality

## Data Quality Health and Status

Data quality is evaluated by inspecting qc flags and variables in
processed data.

**Data Processing Algorithms**

The first stage of the data processing program reads in raw data files
(a0) to produce intermediate a1 files. These a1 *daily* files contain
time stamped 5 Hz data but are not yet corrected for sensor offset and
drifts. It is also worth to note that from time to time the CO system
has hiccups (mostly windows operating system related) and a0 data
contains truncated lines. These lines are purged during the a0 to a1
processing.

The second stage of data processing reads a1 files to produce estimates
of CO mixing ratios with qc flags.

-   Calculate average concentrations for each channel (sampled, zero,
    and span air).

-   Correct for offset of the instrument.

-   Find calibration data and correct for drifts.

-   Write out results.

## Data Reviews by Instrument Mentor

ARM staff perform preventive maintenance checks weekly and
post-preventive maintenance reports on the internet. ARM carbon staff at
LBNL checks these reports on a weekly basis. Instrument mentor Sébastien
Biraud routinely views graphical displays produced at LBNL. The displays
include graphs of CO concentrations, flow rate, pressure, automatic gain
control, and dew point temperature.

## Data Assessments by Site Scientist/Data Quality Office

Not available at this time.

## Value-Added Procedures and Quality Measurement Experiments

Not available at this time.

# Instrument Details

## Detailed Description

### List of Components

Thermo Electron Gas Analyzer Model 48°C

-   Zero Noise : 5.0 ppb RMS (120 second averaging time)

-   Zero Drift (24 hour): less than 100 ppb

-   Response Time: 60 seconds (30 second averaging time)

-   Precision: 10.0 ppb

-   Sample Flow Rate: 0.5 liter/min

-   Operating Temperature: 20° 30°C (may be safely operated over the
    range 5°-45°C)

-   Power Requirements: 90-100 VAC; 210-240 VAC, 50 Hz, 100 Watts

Tylan mass flow controller (FC-2900)

-   Flow: 0.5 LPM

-   Step Response Time: 1 sec (dependent on step request and conditions)

-   Accuracy: ± 1.0% full scale

-   Linearity: ± 0.5% full scale

-   Repeatability: ± 0.2% full scale

-   Valve Normally-open or normally-closed solenoid

-   Supply Voltage: ± 12 VDC to ± 18 VDC

-   Supply Current: 110 mA nominal (125 mA max @ ± 18 VDC)

-   Power Consumption: 3.3 watts @ ± 15 volts

-   Input/Output Signal: 0-5 VDC

MKS Pressure controller (model 640)

-   Pressure: 100 PSI

-   Supply Voltage: 15 VDC ± 5%

-   Supply Current: 200 mA max

-   Input/Output Signal: 0-5 VDC

Vaisala Dewpoint Transmitter DMT142

-   Operating Dewpoint Temperature: -50°C  +60°C (-76°F  +140°F)

-   Accuracy: ±3°C (± 5.4°F)

-   Withstands condensation

### System Configuration and Measurement Methods

We measure one sample for 5 minutes at a time; the reported value is the
average of the last 2 minutes. Every 6 hours, we run two calibration
standards (NOAA/ESRL) certified standards at approximately 100 and
300 ppb. Sample CO concentration is calculated with the standards run
before and after it.

Data from the CO analyzer are transmitted to a personal computer (PC)
located in an instrument shed at the base of the 60-meter tower. The PC
collects and stores ASCII data stream from the gas analyzer using
LABVIEW software. The raw data are transferred to LBNL, processed into
the ARM Archive format, and inspected for problems on a daily basis.
Processed files are sent to the ARM Archive using the Site Transfer
Suite on a weekly basis.

### Specifications

This section is not applicable to this instrument.

## Theory of Operation

See Section 7.1, Detailed Description.

## Calibration

### Theory

See Section 7.1, Detailed Description.

### Procedures

See Section 7.1, Detailed Description.

### History

Currently, the instrument performance is checked against weekly
NOAA/ESRL flask samples collected from the 60-meter tower air-sampling
inlet.

## Operation and Maintenance

### User Manual

This section is not applicable to this instrument.

### Routine and Corrective Maintenance Documentation

This section is not applicable to this instrument.

### Software Documentation

General description of the data product formats can be found in Section
5.

### Additional Documentation

This section is not applicable to this instrument.

## Glossary

See the [ARM Glossary](http://www.arm.gov/about/glossary.stm).

## Acronyms

ARM Atmospheric Radiation Measurement (Program)

CO carbon monoxide

ESRL National Earth System Research Laboratory

LBNL Lawrence Berkeley National Laboratory

NOAA National Oceanic and Atmospheric Administration

PC personal computer

qc quality control

See the [ARM Acronyms and
Abbreviations](http://www.arm.gov/about/acronyms.stm).

## Citable References

Chaney, LW, and WA McClenny. 1977. "Unique ambient carbon monoxide
monitor based on gas filter correlation: performance and application."
*Environmental Science and Technology* 11:1186-1190.

Dickerson, RR, and AC Delany. 1988. "Modification of a commercial gas
filter correlation CO detector for enhanced sensitivity." *Journal of
Atmospheric and Oceanic Technology* 5:424-431.

Novelli, PC, JW Elkins, and LP Steele. 1991. "The development and
evaluation of a gravimetric reference scale for measurements of
atmospheric carbon monoxide." *Journal of Geophysical Research -
Atmospheres* 96:13,109-13,121.

Parrish, DD, JS Holloway, and FC Fehsenfeld. 1994. "Routine, continuous
measurement of carbon monoxide with parts per billion precision."
*Environmental Science and Technology* 28:1615-1618.