ARM TR-035

> **Surface and Tower Meteorological**
>
> **Instrumentation at Barrow (METTWR4H)**
>
> Handbook
>
> April 2008
>
> M.T. Ritsche
>
> 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 3](#data-description-and-examples)

[6. Data Quality 10](#data-quality)

[7. Instrument Details 11](#instrument-details)

**Figures**

[1. CMH Daily Self Test 9](#__RefHeading___Toc96159532)

2\. CMH Autobalance Recovery
Issue...........................................................................10

[2. Wind Speed spike at the 40m level 11](#__RefHeading___Toc96159533)

[3. Ultrasonic Data Spikes 11](#__RefHeading___Toc96159534)

**Tables**

[1. Location and History 2](#__RefHeading___Toc96159559)

[2. Primary Variables 3](#__RefHeading___Toc96159560)

[3. Diagnostic Variables 6](#__RefHeading___Toc96159561)

[4. Quality Check Variables 7](#__RefHeading___Toc96159562)

[5. Dimension Variables 9](#__RefHeading___Toc96159563)

# General Overview

The Barrow meteorology station (BMET) uses mainly conventional *in situ*
sensors mounted at four different heights (2m, 10m, 20m and 40m) on a 40
m tower to obtain profiles of wind speed, wind direction, air
temperature, dew point and humidity. It also obtains barometric
pressure, visibility and precipitation data from sensors at the base of
the tower. Additionally, a Chilled Mirror Hygrometer and an Ultrasonic
wind speed sensor are located near the 2m level for comparison purposes.

# Contacts

## Mentor

Michael Ritsche, Scientific Associate\
Argonne National Laboratory

9700 South Cass Avenue, Bldg. 203\
Argonne, IL 60439\
Phone: 630-252-1554\
Fax: 630-252-5498\
E-mail:
[mtritsche@anl.gov](http://www.arm.gov/instruments/static/mail to: mtritsche@anl.gov)

## Instrument Developer

**Wind Speed and Direction, Temperature and Relative Humidity,
Barometric Pressure, Present Weather Sensor**

Vaisala

100 Commerce Way

Woburn, MA 01801-1068

Phone: 617-933-4500

Fax: 617-933-8029

Web page: [http://www.vaisala.com](http://www.vaisala.com/)

**Aspirated Radiation Shields**

R.M. Young Company

2801 Aero-Park Drive

Traverse City, MI 49686

Phone: 231-946-3980

Fax: 231-946-4772

Web page: [http://www.youngusa.com](http://www.youngusa.com/)

**Chilled-Mirror Hygrometer**

Technical Services Laboratory, Inc.

95 Ready Ave.

Fort Walton Beach, FL 32548

Phone: 850-243-3722

**Precipitation**\
Scientific Technology, Inc.\
205 Perry Parkway, Suite 14\
Gaithsburg, MD 20877-2141\
Phone: 301-948-6070\
Fax: 301-948-4674\
\
**Computer**\
Dell Optiplex GX270 SFF\
Web page: [http://www.dell.com](http://www.dell.com/)

**Datalogger and Ethernet Devices**\
Campbell Scientific Inc.\
815 W. 1800 N.

Logan, UT 84321\
Phone: 801-753-2342\
Fax: 801-750-9540\
Web page: [http://www.campbellsci.com](http://www.campbellsci.com/)

**Fiber Driver**\
Allied Telesys\
19800 North Creek Parkway, Suite 200\
Bothell, WA 98011\
Phone: 425-487-8880\
Fax: 425-489-9191\
Toll-free: 1-800-424-6596 (US only)\
Web page: [http://alliedtelesyn.com](http://alliedtelesyn.com/)

# Deployment Locations and History 

The original configuration and collection system was installed in March
1998. In October 2003 the configuration and collection system was
changed considerably. Information on the data, sensors and measurement
methods prior to October 2003 can be found at [Barrow Meteorology
Station (BMET)](http://www.arm.gov/instruments/instrument.php?id=8).

[]{#__RefHeading___Toc96159559 .anchor}Table 1. Location and History

  ----------------- ----------------- ----------------- -----------------
  **Location**      **Date            **Date Removed**  **Status**
                    Installed**                         

  NSA/C1            10/2003                             Operational
  ----------------- ----------------- ----------------- -----------------

# Near-Real-Time Data Plots

Near-real-time data plots can be found at the following locations:

-   <http://www.nsdl.arm.gov/Visualization/quicklook_interface.shtml>

-   <http://www.nsdl.arm.gov/Visualization/ncvweb.shtml>.

# Data Description and Examples

## Data File Contents

### Primary Variables and Expected Uncertainty

[]{#__RefHeading___Toc96159560 .anchor}Table 2. Primary Variables

+-----------------+---------------+----+----------+----------+--------+
| **Quantity**    | **Variable**  | ** | **Mea    | **Mea    | **     |
|                 |               | Un | surement | surement | Resolu |
|                 |               | it | Level**  | In       | tion** |
|                 |               | ** |          | terval** |        |
+-----------------+---------------+----+----------+----------+--------+
| 2m Arithmetic   | WS2m_S_WVT    | m  | 2m       | 1 min    | 0.001  |
| Mean Wind Speed |               | /s |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 2m Vector       | WS2m_U_WVT    | m  | 2m       | 1 min    | 0.001  |
| Averaged Wind   |               | /s |          |          |        |
| Speed           |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 2m Vector       | WD2m_DU_WVT   | d  | 2m       | 1 min    | 0.001  |
| Averaged Wind   |               | eg |          |          |        |
| Direction       |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| Standard        | WD2m_SDU_WVT  | d  | 2m       | 1 min    | 0.01   |
| Deviation of 2m |               | eg |          |          |        |
| Vector Averaged |               |    |          |          |        |
|                 |               |    |          |          |        |
| Wind Direction  |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 10m Arithmetic  | WS10m_S_WVT   | m  | 10m      | 1 min    | 0.001  |
| Mean Wind Speed |               | /s |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 10m Vector      | WS10m_U_WVT   | m  | 10m      | 1 min    | 0.001  |
| Averaged Wind   |               | /s |          |          |        |
| Speed           |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 10m Vector      | WD10m_DU_WVT  | d  | 10m      | 1 min    | 0.001  |
| Averaged Wind   |               | eg |          |          |        |
| Direction       |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| Standard        | WD10m_SDU_WVT | d  | 10m      | 1 min    | 0.01   |
| Deviation of    |               | eg |          |          |        |
| 10m Vector      |               |    |          |          |        |
| Averaged Wind   |               |    |          |          |        |
| Direction       |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 20m Arithmetic  | WS20m_S_WVT   | m  | 20m      | 1 min    | 0.001  |
| Mean Wind Speed |               | /s |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 20m Vector      | WS20m_U_WVT   | m  | 20m      | 1 min    | 0.001  |
| Averaged Wind   |               | /s |          |          |        |
| Speed           |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 20m Vector      | WD20m_DU_WVT  | d  | 20m      | 1 min    | 0.001  |
| Averaged Wind   |               | eg |          |          |        |
| Direction       |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| Standard        | WD20m_SDU_WVT | d  | 20m      | 1 min    | 0.01   |
| Deviation of    |               | eg |          |          |        |
| 20m Vector      |               |    |          |          |        |
| Averaged Wind   |               |    |          |          |        |
| Direction       |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 40m Arithmetic  | WS40m_S_WVT   | m  | 40m      | 1 min    | 0.001  |
| Mean Wind Speed |               | /s |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 40m Vector      | WS40m_U_WVT   | m  | 40m      | 1 min    | 0.001  |
| Averaged Wind   |               | /s |          |          |        |
| Speed           |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 40m Vector      | WD40m_DU_WVT  | d  | 40m      | 1 min    | 0.001  |
| Averaged Wind   |               | eg |          |          |        |
| Direction       |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| Standard        | WD40m_SDU_WVT | d  | 40m      | 1 min    | 0.01   |
| Deviation of    |               | eg |          |          |        |
| 40m Vector      |               |    |          |          |        |
| Averaged Wind   |               |    |          |          |        |
| Direction       |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| Sonic           | SonicWs_S_WVT | m  | 2m       | 1 min    | 0.001  |
| Arithmetic Mean |               | /s |          |          |        |
| Wind Speed      |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+

**Table 2**. (cont'd)

+-----------------+---------------+----+----------+----------+--------+
| **Quantity**    | **Variable**  | ** | **Mea    | **Mea    | **     |
|                 |               | Un | surement | surement | Resolu |
|                 |               | it | Level**  | In       | tion** |
|                 |               | ** |          | terval** |        |
+-----------------+---------------+----+----------+----------+--------+
| Sonic Vector    | SonicWs_U_WVT | m  | 2m       | 1 min    | 0.001  |
| Averaged Wind   |               | /s |          |          |        |
| Speed           |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| sonic Vector    | S             | d  | 2m       | 1 min    | 0.001  |
| Averaged Wind   | onicWD_DU_WVT | eg |          |          |        |
| Direction       |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| Standard        | So            | d  | 2m       | 1 min    | 0.01   |
| Deviation of    | nicWD_SDU_WVT | eg |          |          |        |
| Sonic Vector    |               |    |          |          |        |
| Averaged Wind   |               |    |          |          |        |
| Direction       |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 2m Average      | T2m_AVG       | C  | 2m       | 1 min    | 0.001  |
| Temperature     |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 2m Average      | RH2m_AVG      | \% | 2m       | 1 min    | 0.01   |
|                 |               |    |          |          |        |
| Relative        |               |    |          |          |        |
| Humidity        |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 2m Average      | DP2m_AVG      | C  | 2m       | 1 min    | 0.001  |
| Calculated Dew  |               |    |          |          |        |
| Point           |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 2m Average      | VP2m_AVG      | k  | 2m       | 1 min    | 0.001  |
| Calculated      |               | Pa |          |          |        |
| Vapor Pressure  |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 10m Average     | T10m_AVG      | C  | 10m      | 1 min    | 0.001  |
| Temperature     |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 10m Average     | RH10m_AVG     | \% | 10m      | 1 min    | 0.01   |
|                 |               |    |          |          |        |
| Relative        |               |    |          |          |        |
| Humidity        |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 10m Average     | DP10m_AVG     | C  | 10m      | 1 min    | 0.001  |
| Calculated Dew  |               |    |          |          |        |
| Point           |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 10m Average     | VP10m_AVG     | k  | 10m      | 1 min    | 0.001  |
| Calculated      |               | Pa |          |          |        |
| Vapor Pressure  |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 20m Average     | T20m_AVG      | C  | 20m      | 1 min    | 0.001  |
| Temperature     |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 20m Average     | RH20m_AVG     | \% | 20m      | 1 min    | 0.01   |
|                 |               |    |          |          |        |
| Relative        |               |    |          |          |        |
| Humidity        |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 20m Average     | DP20m_AVG     | C  | 20m      | 1 min    | 0.001  |
| Calculated Dew  |               |    |          |          |        |
| Point           |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 20m Average     | VP20m_AVG     | k  | 20m      | 1 min    | 0.001  |
| Calculated      |               | Pa |          |          |        |
| Vapor Pressure  |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 40m Average     | T40m_AVG      | C  | 40m      | 1 min    | 0.001  |
| Temperature     |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 40m Average     | RH40m_AVG     | \% | 40m      | 1 min    | 0.01   |
|                 |               |    |          |          |        |
| Relative        |               |    |          |          |        |
| Humidity        |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 40m Average     | DP40m_AVG     | C  | 40m      | 1 min    | 0.001  |
| Calculated Dew  |               |    |          |          |        |
| Point           |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 40m Average     | VP40m_AVG     | k  | 40m      | 1 min    | 0.001  |
| Calculated      |               | Pa |          |          |        |
| Vapor Pressure  |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| Atmospheric     | AtmPress      | h  | 1m       | 1 min    | 0.1    |
| Pressure        |               | Pa |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 1 minute        | AvgVis1mi     | m  | 2m       | 1 min    | 1      |
| Average         |               |    |          |          |        |
| Visibility      |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| 10 minute       | AvgVis10m     | m  | 2m       | 1 min    | 1      |
| Average         |               |    |          |          |        |
| Visibility      |               |    |          |          |        |
+-----------------+---------------+----+----------+----------+--------+
| Instant Present | InstPWCod     | N  | 2m       | 1 min    | N/A    |
| Weather Code    |               | /A |          |          |        |
+-----------------+---------------+----+----------+----------+--------+

**Table 2**. (cont'd)

  ------------------ ---------------- ---------- --------------- --------------- ----------------
  **Quantity**       **Variable**     **Unit**   **Measurement   **Measurement   **Resolution**
                                                 Level**         Interval**      

  15 minute Present  PWcod15mi        N/A        2m              1 min           N/A
  Weather Code                                                                   

  1 hour Present     PWCod1hr         N/A        2m              1 min           N/A
  Weather Code                                                                   

  Precipitation Rate PCPRate          mm/hr      2m              1 min           0.01

  Cumulative Water   CumH2O           mm         2m              1 min           0.01
  Sum                                                                            

  Cumulative Snow    CumSnow          mm         2m              1 min           0.01
  Sum                                                                            

  Chilled Mirror     CMHTemp          C          1m              1 min           0.01
  Temperature                                                                    

  Chilled Mirror Dew CMHDP            C          1m              1 min           0.01
  Point                                                                          

  Chilled Mirror     SatVPCMH         kPa        1m              1 min           0.01
  Calculated                                                                     
  Saturation Vapor                                                               
  Pressure                                                                       

  Chilled Mirror     VPCMH            kPa        1m              1 min           0.01
  Calculated Vapor                                                               
  Pressure                                                                       

  Chilled Mirror     CMHRH            \%         1m              1 min           0.1
  Calculated                                                                     
  Relative Humidity                                                              
  ------------------ ---------------- ---------- --------------- --------------- ----------------

#### Definition of Uncertainty

We define uncertainty as the range of probable maximum deviation of a
measured value from the true value within a 95% confidence interval.
Given a bias (mean) error *B* and uncorrelated random errors
characterized by a variance *σ^2^*, the root-mean-square error (RMSE) is
defined as the vector sum of these,

$$\text{RMSE} = \left( B^{2} + s^{2} \right)^{\frac{1}{2}}$$

(*B* may be generalized to be the sum of the various contributors to the
bias and *σ^2^* the sum of the variances of the contributors to the
random errors). To determine the 95% confidence interval we use the
Student's *t* distribution: *t*~n;0.025~ ≈ 2, assuming the RMSE was
computed for a reasonably large ensemble. Then the *uncertainty* is
calculated as twice the RMSE.

### Secondary/Underlying Variables

This section is not applicable to this instrument.

### Diagnostic Variables

[]{#__RefHeading___Toc96159561 .anchor}Table 3. Diagnostic Variables

  -------------------------------------- -------------- ------------------
  **Quantity**                           **Variable**   **Measurement
                                                        Interval**

  2m Average QLI Input Voltage           Volt2m_Avg     1 min

  2m Average QLI Reference Temperature   RefT2m_AVG     1 min

  10m Average QLI Input Voltage          Volt10m_Avg    1 min

  10m Average QLI Reference Temperature  RefT10m_AVG    1 min

  20m Average QLI Input Voltage          Volt20m_Avg    1 min

  20m Average QLI Reference Temperature  RefT20m_AVG    1 min

  40m Average QLI Input Voltage          Volt40m_Avg    1 min

  40m Average QLI Reference Temperature  RefT40m_AVG    1 min

  Present Weather Sensor Alarm           PWSAlarm       1 min

  Standard Deviation of 2m Temperature   T2m_STD        1 min

  Standard Deviation of 2m Relative      RH2m_STD       1 min
  Humidity                                              

  Standard Deviation of 2m Calculated    DP2m_STD       1 min
  Dew Point                                             

  Standard Deviation of 2m Calculated    VP2m_STD       1 min
  Vapor Pressure                                        

  Standard Deviation of 10m Temperature  T10m_STD       1 min

  Standard Deviation of 10m Relative     RH10m_STD      1 min
  Humidity                                              

  Standard Deviation of 10m Calculated   DP10m_STD      1 min
  Dew Point                                             

  Standard Deviation of 10m Calculated   VP10m_STD      1 min
  Vapor Pressure                                        

  Standard Deviation of 20m Temperature  T20m_STD       1 min

  Standard Deviation of 20m Relative     RH20m_STD      1 min
  Humidity                                              

  Standard Deviation of 20m Calculated   DP20m_STD      1 min
  Dew Point                                             

  Standard Deviation of 20m Calculated   VP20m_STD      1 min
  Vapor Pressure                                        

  Standard Deviation of 40m Temperature  T40m_STD       1 min

  Standard Deviation of 40m Relative     RH40m_STD      1 min
  Humidity                                              

  Standard Deviation of 40m Calculated   DP40m_STD      1 min
  Dew Point                                             

  Standard Deviation of 40m Calculated   VP40m_STD      1 min
  Vapor Pressure                                        

  Average X Component of Sonic Wind      SonicX_Avg     1 min
  Speed                                                 

  Average Y Component of Sonic Wind      SonicY_AVG     1 min
  Speed                                                 

  Average Sonic Static Speed of Sound    SonicS_AVG     1 min

  Datalogger Battery Voltage             Batt_Volt      1 min
  -------------------------------------- -------------- ------------------

### Data Quality Flags

[]{#__RefHeading___Toc96159562 .anchor}Table 4. Quality Check Variables

+-----------------------+------------------+----------+----+----+----+
| **Quantity**          | **Variable**     | **Mea    | *  | *  | *  |
|                       |                  | surement | *M | *M | *D |
|                       |                  | In       | in | ax | el |
|                       |                  | terval** | ** | ** | ta |
|                       |                  |          |    |    | ** |
+-----------------------+------------------+----------+----+----+----+
| Sample time           | qc_time          | 1 min    |    |    | N  |
|                       |                  |          |    |    | /A |
+-----------------------+------------------+----------+----+----+----+
| 2m Arithmetic Mean    | qc_WS2m_S_WVT    | 1 min    | 0  | 1  | 20 |
|                       |                  |          |    | 00 |    |
| Wind Speed            |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+
| 2m Vector Averaged    | qc_WS2m_U_WVT    | 1 min    | 0  | 1  | 20 |
|                       |                  |          |    | 00 |    |
| Wind Speed            |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+
| 2m Vector Averaged    | qc_WD2m_SDU_WVT  | 1 min    | 0  | 3  | N  |
|                       |                  |          |    | 60 | /A |
| Wind Direction        |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+
| 10m Arithmetic Mean   | qc_WS10m_S_WVT   | 1 min    | 0  | 1  | 20 |
|                       |                  |          |    | 00 |    |
| Wind Speed            |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+
| 10m Vector Averaged   | qc_WS10m_U_WVT   | 1 min    | 0  | 1  | 20 |
|                       |                  |          |    | 00 |    |
| Wind Speed            |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+
| 10m Vector Averaged   | qc_WD10m_SDU_WVT | 1 min    | 0  | 3  | N  |
|                       |                  |          |    | 60 | /A |
| Wind Direction        |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+
| 20m Arithmetic Mean   | qc_WS20m_S_WVT   | 1 min    | 0  | 1  | 20 |
|                       |                  |          |    | 00 |    |
| Wind Speed            |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+
| 20m Vector Averaged   | qc_WS20m_U_WVT   | 1 min    | 0  | 1  | 20 |
|                       |                  |          |    | 00 |    |
| Wind Speed            |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+
| 20m Vector Averaged   | qc_WD20m_SDU_WVT | 1 min    | 0  | 3  | N  |
|                       |                  |          |    | 60 | /A |
| Wind Direction        |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+
| 40m Arithmetic Mean   | qc_WS40m_S_WVT   | 1 min    | 0  | 1  | 20 |
|                       |                  |          |    | 00 |    |
| Wind Speed            |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+
| 40m Vector Averaged   | qc_WS40m_U_WVT   | 1 min    | 0  | 1  | 20 |
|                       |                  |          |    | 00 |    |
| Wind Speed            |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+
| 40m Vector Averaged   | qc_WD40m_SDU_WVT | 1 min    | 0  | 3  | N  |
|                       |                  |          |    | 60 | /A |
| Wind Direction        |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+
| Sonic Arithmetic Mean | qc_SonicWS_S_WVT | 1 min    | 0  | 1  | 20 |
|                       |                  |          |    | 00 |    |
| Wind Speed            |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+
| Sonic Vector Averaged | qc_SonicWS_U_WVT | 1 min    | 0  | 1  | 20 |
|                       |                  |          |    | 00 |    |
| Wind Speed            |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+
| Sonic Vector Averaged | qc_Sonic_SDU_WVT | 1 min    | 0  | 3  | N  |
|                       |                  |          |    | 60 | /A |
| Wind Direction        |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+
| 2m Average            | qc_T2m_AVG       | 1 min    | -  | 30 | 10 |
| Temperature           |                  |          | 60 |    |    |
+-----------------------+------------------+----------+----+----+----+
| 2m Average Relative   | qc_RH2m_AVG      | 1 min    | -2 | 1  | 30 |
| Humidity              |                  |          |    | 04 |    |
+-----------------------+------------------+----------+----+----+----+
| 2m Average Calculated | qc_DP2m_AVG      | 1 min    | -  | 30 | 10 |
|                       |                  |          | 60 |    |    |
| Dew Point             |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+
| 2m Average Calculated | qc_VP2m_AVG      | 1 min    | 0  | 4  | 1  |
|                       |                  |          | .0 | .3 |    |
| Vapor Pressure        |                  |          | 01 |    |    |
+-----------------------+------------------+----------+----+----+----+
| 10m Average           | qc_T10m_AVG      | 1 min    | -  | 30 | 10 |
| Temperature           |                  |          | 60 |    |    |
+-----------------------+------------------+----------+----+----+----+
| 10m Average Relative  | qc_RH10m_AVG     | 1 min    | -2 | 1  | 30 |
| Humidity              |                  |          |    | 04 |    |
+-----------------------+------------------+----------+----+----+----+
| 10m Average           | qc_DP10m_AVG     | 1 min    | -  | 30 | 10 |
| Calculated            |                  |          | 60 |    |    |
|                       |                  |          |    |    |    |
| Dew Point             |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+

**Table 4**. (cont'd)

+-----------------------+------------------+----------+----+----+----+
| **Quantity**          | **Variable**     | **Mea    | *  | *  | *  |
|                       |                  | surement | *M | *M | *D |
|                       |                  | In       | in | ax | el |
|                       |                  | terval** | ** | ** | ta |
|                       |                  |          |    |    | ** |
+-----------------------+------------------+----------+----+----+----+
| 10m Average           | qc_VP10m_AVG     | 1 min    | 0  | 4  | 1  |
| Calculated            |                  |          | .0 | .3 |    |
|                       |                  |          | 01 |    |    |
| Vapor Pressure        |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+
| 20m Average           | qc_T20m_AVG      | 1 min    | -  | 30 | 10 |
| Temperature           |                  |          | 60 |    |    |
+-----------------------+------------------+----------+----+----+----+
| 20m Average Relative  | qc_RH20m_AVG     | 1 min    | -2 | 1  | 30 |
| Humidity              |                  |          |    | 04 |    |
+-----------------------+------------------+----------+----+----+----+
| 20m Average           | qc_DP20m_AVG     | 1 min    | -  | 30 | 10 |
| Calculated            |                  |          | 60 |    |    |
|                       |                  |          |    |    |    |
| Dew Point             |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+
| 20m Average           | qc_VP20m_AVG     | 1 min    | 0  | 4  | 1  |
| Calculated            |                  |          | .0 | .3 |    |
|                       |                  |          | 01 |    |    |
| Vapor Pressure        |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+
| 40m Average           | qc_T40m_AVG      | 1 min    | -  | 30 | 10 |
| Temperature           |                  |          | 60 |    |    |
+-----------------------+------------------+----------+----+----+----+
| 40m Average Relative  | qc_RH40m_AVG     | 1 min    | -2 | 1  | 30 |
| Humidity              |                  |          |    | 04 |    |
+-----------------------+------------------+----------+----+----+----+
| 40m Average           | qc_DP40m_AVG     | 1 min    | -  | 30 | 10 |
| Calculated            |                  |          | 60 |    |    |
|                       |                  |          |    |    |    |
| Dew Point             |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+
| 40m Average           | qc_VP40m_AVG     | 1 min    | 0  | 4  | 1  |
| Calculated            |                  |          | .0 | .3 |    |
|                       |                  |          | 01 |    |    |
| Vapor Pressure        |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+
| Atmospheric Pressure  | qc_AtmPress      | 1 min    | 8  | 11 | 10 |
|                       |                  |          | 00 | 00 |    |
+-----------------------+------------------+----------+----+----+----+
| 1 minute Average      | qc_AvgVis1mi     | 1 min    | 0  | 5  | N  |
| Visibility            |                  |          |    | 00 | /A |
|                       |                  |          |    | 00 |    |
+-----------------------+------------------+----------+----+----+----+
| 10 minute Average     | qc_AvgVis10m     | 1 min    | 0  | 5  | N  |
| Visibility            |                  |          |    | 00 | /A |
|                       |                  |          |    | 00 |    |
+-----------------------+------------------+----------+----+----+----+
| Instant Present       | qc_InstPWCod     | 1 min    | 0  | 99 | N  |
| Weather Code          |                  |          |    |    | /A |
+-----------------------+------------------+----------+----+----+----+
| 15 minute Present     | qc_PWcod15mi     | 1 min    | 0  | 99 | N  |
| Weather Code          |                  |          |    |    | /A |
+-----------------------+------------------+----------+----+----+----+
| 1 hour Present        | qc_PWCod1hr      | 1 min    | 0  | 99 | N  |
| Weather Code          |                  |          |    |    | /A |
+-----------------------+------------------+----------+----+----+----+
| Precipitation Rate    | qc_PCPRate       | 1 min    | 0  | 9  | 1  |
|                       |                  |          |    | 99 | 00 |
+-----------------------+------------------+----------+----+----+----+
| Cumulative Water Sum  | qc_CumH2O        | 1 min    | 0  | 99 | 10 |
+-----------------------+------------------+----------+----+----+----+
| Cumulative Snow Sum   | qc_CumSnow       | 1 min    | 0  | 9  | 1  |
|                       |                  |          |    | 99 | 00 |
+-----------------------+------------------+----------+----+----+----+
| Chilled Mirror        | qc_CMHTemp       | 1 min    | -  | 30 | 10 |
| Temperature           |                  |          | 60 |    |    |
+-----------------------+------------------+----------+----+----+----+
| Chilled Mirror Dew    | qc_CMHDP         | 1 min    | -  | 30 | 10 |
| Point                 |                  |          | 60 |    |    |
+-----------------------+------------------+----------+----+----+----+
| Chilled Mirror        | qc_SatVPCMH      | 1 min    | 0  | 4  | 1  |
| Calculated Saturation |                  |          | .0 | .3 |    |
| Vapor Pressure        |                  |          | 01 |    |    |
+-----------------------+------------------+----------+----+----+----+
| Chilled Mirror        | qc_VPCMH         | 1 min    | 0  | 4  | 1  |
| Calculated            |                  |          | .0 | .3 |    |
|                       |                  |          | 01 |    |    |
| Vapor Pressure        |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+
| Chilled Mirror        | qc_CMHRH         | 1 min    | 0  | 1  | 30 |
| Calculated Relative   |                  |          |    | 01 |    |
| Humidity              |                  |          |    |    |    |
+-----------------------+------------------+----------+----+----+----+

### Dimension Variables

[]{#__RefHeading___Toc96159563 .anchor}Table 5. Dimension Variables

  -------------- ------------------- ----------------------------------------
  **Variable**   **Measurement       **Unit**
                 Interval**          

  base_time      1 min               seconds since YYYY-mm-dd XX:XX:XX X:XX

  time_offset    1 min               seconds since YYYY-mm-dd XX:XX:XX X:XX

  time           1 min               seconds since YYYY-mm-dd XX:XX:XX X:XX

  lat            1 min               degrees

  lon            1 min               degrees

  alt            1 min               meters above sea level
  -------------- ------------------- ----------------------------------------

## Annotated Examples

This section is not applicable to this instrument.

## User Notes and Known Problems

The 40-meter tower that the sensors are mounted on is misaligned to true
north by 30 degrees. In most instances this error is corrected by
programming. Unfortunately from 10/31/2003 through 10/20/2005 this
correction was not applied. The wind data during this time is 30 degrees
east of what it should be. In other words, until reprocessing corrects
this error, users should subtract 30 degrees from the wind direction
data.

Once a day the Chilled Mirror Hygrometer goes through a daily self-test.
This is done to remove contaminants from the mirror. It also allows the
CMH to assess the level of contamination remaining on the mirror. When
the self-test occurs the mirror is heated to above ambient causing the
dew point, RH, vapor pressure and saturation vapor pressure data during
the time of self-test and recovery to be incorrect. See Figure 1 below.

![](media/image1.png){width="4.784027777777778in"
height="2.8534722222222224in"}

[]{#__RefHeading___Toc96159532 .anchor}Figure 1. CMH Daily Self Test

When the CMH does through the daily self-test and autobalance of the
mirror it has to heat the mirror to remove contaminants and make a
measurement of the cleanliness of the mirror. After the reading is
finished it must cool the mirror back to ambient dew point temperatures.
When the dew point depression is large enough this dynamic adjustment
does not take much time. When the dew point depression is small and the
temperatures are below freezing this dynamic adjustment can take up to a
few hours. When the dew point depression is small the system has a
tendency to overdrive the mirror colder than the ambient dew point and
followed be warmer than the ambient as it tries to return the mirror to
the dew point temperature. See Figure 2 for and example plot of this
situation. The best way to describe what is happening is to imagine a
plot of a sinusoidal curve (the mirror dew point) moving above and below
the actual dew point curve as the CMH control circuits try to
equilibrate the mirror with the environment. As time progresses the
siunusiodal curve moves asymptotically toward the actual ambient dew
point values. If the ambient dew point is changing rapidly at the time
of autobalance adjustment the time to equilibrate is even longer.

![](media/image2.png){width="6.496527777777778in"
height="4.378472222222222in"}

**Figure 2**: CMH Autobalance Recovery Issue

At times the data from the wind speed and direction sensors is missed
when it is sent from the QLI50 Data Collector to the Serial Data
Multiplexer. When this occurs a spike is noticed in the data as the
program tries to convert --6999 or --9999 data into vector averages. See
Figure 3 below.

![](media/image3.png){width="5.998611111111111in"
height="1.8138888888888889in"}

[]{#__RefHeading___Toc96159533 .anchor}Figure 3. Wind Speed spike at the
40m level

##  {#section .unnumbered}

## At times the data from the Ultrasonic wind speed and direction sensor is poor due to heavy, wet snow. When this occurs the Ultrasonic sensor outputs --6999 or --9999. The datalogger attempts to convert the poor or missing data values to vector averages. As the missing or poor data may only be a few seconds in a minute the values are averaged into the minute values and show up as spikes in the data. See Figure 4 below. {#at-times-the-data-from-the-ultrasonic-wind-speed-and-direction-sensor-is-poor-due-to-heavy-wet-snow.-when-this-occurs-the-ultrasonic-sensor-outputs-6999-or-9999.-the-datalogger-attempts-to-convert-the-poor-or-missing-data-values-to-vector-averages.-as-the-missing-or-poor-data-may-only-be-a-few-seconds-in-a-minute-the-values-are-averaged-into-the-minute-values-and-show-up-as-spikes-in-the-data.-see-figure-4-below. .unnumbered}

![](media/image4.png){width="5.998611111111111in"
height="1.6722222222222223in"}

[]{#__RefHeading___Toc96159534 .anchor}Figure 4. Ultrasonic Data Spikes

## Frequently Asked Questions

This section is not applicable to this instrument.

# Data Quality

## Data Quality Health and Status

Data Quality Health and Status (DQ HandS)
[http://dq.arm.gov](http://dq.arm.gov/)

NCVweb - for interactive data plotting using
<http://dq.arm.gov/ncvweb/ncvweb.cgi>

## Data Reviews by Instrument Mentor

This section is not applicable to this instrument.

## Data Assessments by Site Scientist/Data Quality Office

The ARM Data Quality Office uses the Data Quality Assessment (DQA)
system to inform the ARM Site Operators, Site Scientists, and Instrument
Team members of instrument and data flow problems as well as general
data quality observations. The routine assessment reports are performed
on the most recently-collected ARM data, and used with the Data Quality
Problem reports tool to initiate and track the problem resolution
process.

<http://dq.arm.gov/weekly_reports/weekly_reports.html>

## Value-Added Procedures and Quality Measurement Experiments

Many of the scientific needs of the ARM Program are met through the
analysis and processing of existing data products into \"value-added\"
products or VAPs. Despite extensive instrumentation deployed at the ARM
CART sites, there will always be quantities of interest that are either
impractical or impossible to measure directly or routinely. Physical
models using ARM instrument data as inputs are implemented as VAPs and
can help fill some of the unmet measurement needs of the program.
Conversely, ARM produces some VAPs not in order to fill unmet
measurement needs, but instead to improve the quality of existing
measurements. In addition, when more than one measurement is available,
ARM also produces \"best estimate\" VAPs. A special class of VAP called
a Quality Measurement Experiment (QME) does not output geophysical
parameters of scientific interest. Rather, a QME adds value to the input
datastreams by providing for continuous assessment of the quality of the
input data based on internal consistency checks, comparisons between
independent similar measurements, or comparisons between measurement
with modeled results, and so forth. For more information, see the [VAPs
and QMEs](http://www.arm.gov/data/vaps_all.php) web page.

# Instrument Details

## Detailed Description

### List of Components

#### Wind Speed Sensor: A Vaisala WAA251 cup anemometer is used to measure the horizontal wind speed. {#wind-speed-sensor-a-vaisala-waa251-cup-anemometer-is-used-to-measure-the-horizontal-wind-speed. .unnumbered}

#### Wind Direction Sensor: A Vaisala WAV151 wind vane with heated shaft is used to measure wind direction. {#wind-direction-sensor-a-vaisala-wav151-wind-vane-with-heated-shaft-is-used-to-measure-wind-direction. .unnumbered}

#### Wind Speed and Direction Sensor: A Vaisala WS425 ultrasonic wind sensor is used to measure the horizontal wind speed and direction at the 2m level at Barrow.  {#wind-speed-and-direction-sensor-a-vaisala-ws425-ultrasonic-wind-sensor-is-used-to-measure-the-horizontal-wind-speed-and-direction-at-the-2m-level-at-barrow. .unnumbered}

**Temperature and Relative Humidity Sensor**: A Vaisala HMP45D
temperature and relative humidity probe is used to measure air
temperature and relative humidity.

#### Ambient Temperature and Dew Point Temperature: A Technical Services Laboratory Model 1088 hygrothermometer (CMH) is used to measure air temperature and dew point.  {#ambient-temperature-and-dew-point-temperature-a-technical-services-laboratory-model-1088-hygrothermometer-cmh-is-used-to-measure-air-temperature-and-dew-point. .unnumbered}

**Visibility and Precipitation Sensor**: A Vaisala FD12P present weather
sensor (PWS) is used to measure present weather, visibility and
precipitation.

#### Barometric Pressure Sensor: A Vaisala PTB201A digital barometer is used to measure the station pressure (not corrected to sea level).  {#barometric-pressure-sensor-a-vaisala-ptb201a-digital-barometer-is-used-to-measure-the-station-pressure-not-corrected-to-sea-level. .unnumbered}

### System Configuration and Measurement Methods

#### QLI50 Sensor Collectors {#qli50-sensor-collectors .unnumbered}

Vaisala QLI50 sensor collectors are used to collect data from the wind
speed, wind direction, temperature and relative humidity probes. The
QLI50s determine the frequency of the WAA-252 anemometer signals by
measuring and averaging the time between pulses. The GRAY code output
from the WAV-151 wind vanes is read and converted to angles. The QLI-50s
supply a constant current to the HMP45D platinum resistance detectors
and relative humidity circuitry, measure the returned voltages, and
convert the voltages to temperatures and relative humidity values. The
QLI50s also use the temperature and relative humidity data to calculate
dew point temperatures. The QLI50s also convert the temperature and
relative humidity data to dew point values using the following equation:

TDEW = ((c\*b)/((c\*(a/2)) + b)) -- 273.16

where a = ln(100/X2), b = (1.0\*a) -- (2.1\*X1) + 2711.5, c = X1 +
273.16

X1 = measured air temperature (deg C)

X2 = measured relative humidity (%)

The QLI50s convert the analog data from the sensors to a digital format.
The QLI50s send the data automatically once per second to a Campbell
Scientific SDM-SI04 serial data multiplexer. The data is sent via RS-232
to the SDM. The QLI-50s are set for Automatic messaging (AMES 2) at
1-second intervals (REP A 1). A Vaisala WHP25 supplies power to the
QLI50s.

**Power Supplies**

Vaisala WHP25 power supplies are used to power the QLI50 sensor
collectors; the HMP45D temperature relative humidity probes and the
heating system for the wind speed and wind direction sensors. The output
voltage of the WHP25's is 24VAC. AC to DC converters are used to power
the aspirators, which contain the temperature and relative humidity
probes.

**Serial Data Multiplexer**

Campbell Scientific serial data multiplexers (SDM-SI04) are used to
collect data from the serial devices and serial sensors. The barometer,
present weather sensor (PWS), chilled mirror hygrometer (CMH), and the
QLI50 sensor collector send data to the SDM. The SDM converts the serial
data it collects to a form the CR23X datalogger can understand using
complex filters supplied by the user. The SDM stores complex commands
required to request data from the smart serial devices such as the PWS,
CMH and barometer. These commands are also user supplied. Each SDM has
four serial ports that are independently configured to communicate with
different sensors. At Barrow, two SDM's are used; one to communicate
with the four QLI50s at each of the four levels (2m, 10m, 20m, 40m), the
other is used to communicate with the PWS, CMH, and barometer.

**CR23X Datalogger**

A Campbell Scientific CR23X datalogger is used to acquire and process
the data collected by the SDM from the various sensors. Once per minute
the datalogger prompts the SDM to request data from the PWS, CMH and
barometer. The datalogger also waits for the one-second data from the
SDM connected to the QLI's at once-per-second intervals. At Barrow, the
datalogger also collects data from the ultrasonic wind sensor at
one-second intervals using Campbell Scientifics' SDI-12 communication
protocol. The one-second data from the QLI50s and the ultrasonic are
accumulated in the logger in order to calculate the one-minute data
values and statistics. The one-minute data from the barometer and the
PWS is stored while the CMH data is converted from Fahrenheit to Celsius
and relative humidity is calculated from the Celsius temperature and dew
point. The following equations are used to convert the temperature and
dew point data from the CMH to RH values using calculated vapor pressure
and saturation vapor pressure:

If temperatures are less than 0 deg C:

Saturation VP = (6.1359\*(EXP((22.452\*CMHTemp)/ (272.55 +
CMHTemp))))\*0.1

VP = (6.1359\*(EXP((22.542\*CMHDP)/(272.55 + CMHDP))))\*0.1

If temperatures are greater than or equal to 0 deg C:

Saturation VP = (6.1365\*(EXP((17.502\*CMHTemp)/(240.97 +
CMHTemp))))\*0.1

VP = (6.1365\*(EXP((17.502\*CMHDP)/(240.97 + CMHDP))))\*0.1

RH = 100\*(VP/SatVP)

where CMHTemp = (5/9)\*(measured CMH Temp in F -- 32.0)

CMHDP = (5/9)\*(measured CMH DP in F -- 32)

Once-per-minute data is sent from the CR23X to the PC upon request. The
data is sent via Ethernet through a Campbell Scientific NL-100 network
interface, then to an Allied Telesyn media converter through which the
data is sent to a partner media converter via fiber optic cable. Once
the data reach the end of the fiber, the media converter sends the data
through Ethernet cable to a network switch and then onto the PC. The
CR23X datalogger includes a 4 Mbyte extended memory option allowing the
storage of over 2 million data points in the event of a communication
outage. The datalogger has an extended temperature option giving it a
valid operating temperature range of --40 to +60 C. The CR23X has been
modified so that the Input/Output connectors are removable, allowing for
quick connect/disconnect for easy datalogger replacement.

**NL-100 Network Link Interface**

A Campbell Scientific NL-100 network interface is used to communicate
with the Campbell Scientific CR23X datalogger. The NL100 uses an
Ethernet 10 Base-T communications link between itself and the Allied
Telesyn media converter. The NL100 is configured to act as a Serial
Server in the TCP/IP network. The unique IP address for the system is
stored within the NL100.

**\
**

**AT-MC13 Ethernet Media Converters**

The AT-MC13 media converters are used to convert the data from the CR23X
(through the NL100) to fiber optics. Converting to fiber optics and
using the media converters allows for a 2Km maximum operating distance
of the network. Two media converters are used; one is located at the
base of the towers in the datalogger enclosure, the other is located
inside the building at each location. The media converters operate at 10
Mbps and feature half- and full-duplex operation. The media converters
also have a MIDI/MDI-X switch. This switch is used to configure the
twisted pair port on the media converter as either MIDI or MIDI-X
eliminating the need for crossover cables regardless of the type of
network device that is connected to the unit. The media converters also
have a Fiber Link Test switch that allows testing of the fiber optic
connection without requiring the twisted pair port to be connected.

**Computer**

The PC used at both Barrow and Atqasuk is a Dell Optiplex GX270 Small
Form Factor with a 15" flat panel monitor. The PC contains a Celeron
2.00 GHz, 400 Front Side Bus, and 128K Cache processor. It has 512mb of
DDR non-ECC SD-RAM and an Integrated DVMT Video card. The hard drive is
an 80 GB EIDE 7200 RPM drive. It also has internal Dell business audio
speakers, an integrated Intel Gigabit (10/100/1000) network interface
card and an 8x DVD-ROM. The operating system installed on the PC is
Microsoft Windows XP Professional using NTFS. The PC was configured to
conform to the ARM core PC requirements. The PC is configured to
automatically restart and logon after power disruption eliminating the
need for human intervention. Campbell Scientifics' LoggerNet software is
loaded on the PC and is configured to initialize at start up. LoggerNet
is the software application that enables communication and control of
the CR23X datalogger. Radmin software is also loaded on the PC allowing
remote connection to or control of the local PC. A share-ware program
called InternetTime is used to verify and adjust the time of the PC
clock once a day. A PERL script called \"split_working_cdl.pl\" is used
to handle the output data file from the LoggerNet software. This script
has been installed on both systems in C:\\ARM\\bin and is scheduled to
run once an hour in the LoggerNet task manager. This script creates
uniquely named hourly files and places the files in a folder from which
the Data Collection System can access, collect and delete them. FTP
software allows the Data Collection System to access the PC.

**LoggerNet**

LoggerNet software is an application that allows the set up,
configuration, and retrieval of data from a network of Campbell
Scientific dataloggers. LoggerNet also allows sharing of data over an
Ethernet communications network. LoggerNet is written using advanced
"client-server" architecture. The server is a software program that runs
in the background, handling all of the datalogger communications. The
server also takes care of storing the data and providing information to
manage the datalogger network. Client software programs in LoggerNet are
used to create datalogger programs, view and graph data, verify
communications on the network, and run other software or tasks.

### Specifications

**Wind Speed Sensor**

The anemometers have heated cups and shafts to prevent ice build up. The
anemometers employ a photo-chopper to produce a 10 Hz per m/s signal.
Vaisala quotes a starting threshold of \<0.5 m/s, a distance constant of
2.7 m, and a linear output with an accuracy of +/- 0.17 m/s from 0.4 to
75 m/s.

**Wind Direction Sensor**

The vanes use an optically detected GRAY code disk with a 5.6o
resolution. Vaisala quotes a starting threshold of 0.4 m/s, a damping
ratio of 0.14, and overshoot ratio of 0.65 and a delay distance of 0.4
m.

Wind Speed and Direction Sensor

The WS425 uses ultrasound to determine the horizontal wind speed and
direction. It measures the transit time it takes for the pulse to travel
from one transducer head to another. For wind speed, Vaisala quotes a
starting threshold and delay distance of virtually zero, measurement
range of 1 to 65 m/s, resolution of 0.1 m/s, and an accuracy of +/-
0.135 or 3% of reading (whichever is greater) over the measuring range.
For wind direction, Vaisala quotes the same starting threshold and delay
distance as above, a resolution of 1o, and an accuracy of +/- 2o. The
maximum reading rate for this sensor is once per second.

**Temperature and Relative Humidity Sensor**

The probes are mounted on each level (2m, 10m, 20m, and 40m). Each probe
contains a Vaisala HUMICAP sensor and associated electronics along with
a 4-wire, platinum resistance temperature detector. The relative
humidity output is an analog signal, with 0 to 1V corresponding to an RH
of 0 to 100%. Vaisala quotes the accuracy of the RH signal to be +/- 2%
for 0 to 90 % and +/- 3% for 90 to 100%. The RH sensor has a response
time of 15 seconds. The long-term stability is quoted to be better than
1% RH per year and a temperature dependence of +/- 0.05% RH/oC. The
measurement range of the RTD is quoted as --40 to +60 oC. Each
temperature and relative humidity probe is mounted in a R.M. Young Model
43408-2 aspirated radiation shield. A brushless DC blower provides
aspiration.

**Ambient Temperature and Dew Point Temperature**

The sensor is mounted near the lowest level temperature and relative
humidity probe near the base of the tower. The Model 1088 measures
temperature and dew point over the range of --80 to +130o F. The
accuracy of the temperature measurement is +/- 1o RMS in the range of
--60 to +122o F and +/- 2o F RMS through the remainder of the range. The
accuracy of the dew point temperature is +/- 2o F RMS from 30 to 86o F,
+/- 3o F RMS from --10 to 30o F, +/- 4o F from --30 to -10o F. No
accuracy data for the dew point measurement is available for the rest of
the range. The model 1088 consists of two component units, the aspirator
and the transmitter. The aspirator contains the dew point assembly and
temperature sensor. All of the associated electronics are contained in
the transmitter. Data is sent via RS-232 to the collection system when
the sensor is polled.

**Visibility and Precipitation Sensor**

A Vaisala FD12P present weather sensor (PWS) is a microprocessor-
controlled intelligent device that uses a forward scatter visibility
meter, a capacitive rain detector, and a platinum resistance temperature
detector to measure visibility and precipitation. The LED light source
has a peak-radiated power of 40 mW. The visibility measurement is
accurate to +/-10% for ranges between 10 and 10,000 m and +/- 20% for
ranges between 10,000 and 50,000 m. The accuracy of the precipitation
intensity measurement is +/-30% for the range of 0.5 to 20 mm/hr. The
LED transmitted light intensity is monitored and used to compensate for
temperature and aging effects. Data is sent via RS-232 to the collection
system when the sensor is polled.

**Barometric Pressure Sensor**

The barometer uses a Vaisala BAROCAP silicon capacitive absolute
pressure sensor. Vaisala quotes the operating temperature as --40 to
+60o C and the pressure measurement range as 500 to 1100 hPa. The total
accuracy over the measurement range is given to be +/- 0.15 hPa. Data is
sent via RS-232 to the collection system when the sensor is polled.

## Theory of Operation

Surface meteorological data is collected at the ARM Climate Research
Facility (ACRF) North Slope of Alaska (NSA) site at two locations,
Barrow, Alaska and Atqasuk, Alaska. At the site in Barrow, data is
collected at the base of a 40-meter tower and at 4 levels on the tower;
2-meter, 10-meter, 20-meter and 40-meter. Temperature, relative
humidity, wind speed and wind direction are collected at each level.

The data is collected at the base of the tower using Campbell Scientific
CR23X dataloggers. The dataloggers are polled once a minute by Campbell
Scientific LoggerNet software. The LoggerNet software runs on a Dell
Optiplex GX270 small form-factor computer using Microsoft XP
Professional as the operating system. The computer system is configured
such that if power is interrupted it will automatically restart
eliminating the need for human intervention. The LoggerNet software has
been added to the start menu so that it will automatically begin to
collect data from the dataloggers as soon as the system has re-booted.

The data from the dataloggers is stored in a single location and the
data is appended to an ever-increasing file. A PERL script has been
written to search the data file once an hour to capture a single hours
worth of data (00 -- 59) and copy the data to another file location with
a unique time and date name. The file is then deleted preventing a
large, single file that continues to grow. The hourly files created by
the PERL script are collected once an hour using FTP and the collected
file is then deleted from the local PC.

Remote Administrator (RAdmin) software has been loaded to both computers
so that remote access is available for loading new programs,
troubleshooting, etc. Access is limited to the site observers, mentors,
and selected operations personnel.

Temperature, relative humidity, wind speed and direction are collected
once per second from the different levels of each tower. The one-second
analog data is collected by a Vaisala QLI data collector and is sent via
serial cables to the CR23X datalogger once per second where it is
accumulated to create one-minute averages and other calculated
variables. Data is collected from the other sensors near the base of
each tower once each minute. The Present Weather Sensor (PWS), Chilled
Mirror Hygrometer (CMH) and barometric data are collected once per
minute at each location. At Barrow an ultrasonic wind speed sensor has
also been mounted at the 2-meter level and data from it is collected
once per minute. Data from each of the sensors at the base of the tower
transmit their data via serial cable except for the ultrasonic wind
sensor. The ultrasonic wind sensor transmits its data via Serial Data
Interface (SDI-12), a communication protocol created by Campbell
Scientific.

The serial data from all sensors is sent to, or requested by, a Campbell
Scientific serial data multiplexer (SDM-SIO4). Each SDM-SIO4 has four
ports and a unique address so that multiple SDMs can be connected to
each logger. The Barrow system has two SDMs. Each SDM contains
programming for the communication protocols (baud rate, data bits, etc)
and filters so data can be converted to a form the CR23X can accept.

The data collected by the logger is requested by the LoggerNet system
once per minute. The data is sent by the CR23X datalogger to the
computer via a network connection. A Campbell Scientific NL-100 network
interface is used to send the data via an RS-232 serial connection from
the logger to the computer. The NL-100 allows each datalogger to have a
unique network address. The data is passed from the NL-100 to an Allied
Telesyn AT-MC13 media converter via a Cat-5 Ethernet cable. The media
converter sends the data via a fiber optic cable to another media
converter inside the building where it is sent through a network switch
and onto the computer. See Figure 1: Network Diagram.

The data that is collected from the datalogger can be viewed locally at
each sites computer. A program contained in the LoggerNet software
package called Real Time Monitor and Control (RTMC) is used to plot
graphs of the data and view data values, allowing observers to verify
proper operation of the system and sensors. The raw one-second data can
also be viewed to assist in troubleshooting.

## Calibration

### Theory

The BMET is not calibrated as a system. The sensors along with the
Sensor Collectors and the instruments are calibrated separately. The
system was installed using components that had a current calibration.

### Procedures

**Daily Checks**

The data from the tower are checked each day during daily rounds.
Temperature and relative humidity data from the 2m level and the CMH are
compared to determine if the data appear reasonable. The T/RH data
between the difference levels is compared also to determine if the data
appear to be reasonable. Any discrepancies are noted on the daily rounds
forms. The wind speed and direction is compared and checked against
local conditions. The barometric and present weather data is checked to
determine if what is being reported also appears reasonable. For
example, if the present weather sensor is reporting 100m visibility and
heavy snow when it is clear and sunny out, this indicates a problem with
the present weather sensor and is noted. The present weather sensor also
has an alarm value. If everything is working properly the alarm reading
is 0, if there is a problem the alarm reading will be 1. Data from the
barometer should be between 800 and 1100 hPa. If the barometric data is
outside of these values then it is noted on the daily forms. A view
screen has been built which displays 24 hours of data graphed along with
text values for the current readings. The graphs allow checks of the
data to be made to determine if problems have occurred during the most
recent 24 hours. Long gaps in data, long periods of or many data spikes,
and flat line data (no change in values over extended periods) will be
apparent and are noted on the daily forms.

**Monthly Checks**

Once a month the auto balance dial reading is taken for the CMH. The
auto balance reading is an indication of the contamination on the
surface of the mirror. This value is recorded once a month on the daily
forms. When the reading reaches or exceeds 500, the mirror is cleaned
and the entire sensor is recalibrated.

**Six-Month Checks**

[Present Weather Sensor]{.underline}

The lenses of the present weather sensor are cleaned along with the
capacitive rain detector every six months.

[Chilled Mirror Hygrometer]{.underline}

The CMH is cleaned and recalibrated every six months to ensure proper
functioning and that reasonable data is returned from the sensor.

**Annual Checks**

[Cup Anemometers and Wind Direction Vanes]{.underline}

The bearings in these sensors are checked once a year. The cups and vane
are inspected for any signs of damage. If any irregularity is observed,
the respective anemometer or wind direction sensor is replaced.

[HMP45D Temperature and Relative Humidity Probes]{.underline}

The filters on the probes need to be checked once a year and replaced if
dirty.

[PTB201 or PTB220 Digital Barometer]{.underline}

The reading of the digital barometer is compared with the reference
digital barometer.

[FD12P Present Weather Sensor]{.underline}

The visibility calibration is checked once a year using the FDA12
calibration kit.

**Two-Year Checks and Replacement**

[Wind Speed and Direction Sensors]{.underline}

The calibration of the current cup anemometers and the frequency
measuring portion of the QLI50 Sensor Collectors is checked by using the
R. M. Young Model 18810 Anemometer Drive to spin the anemometer shafts
for at least one minute at the different rpms. The calibration of the
current wind vanes and decoding portion of the QLI50 Sensor Collector is
also checked. The sensors are then replaced and the newly installed
sensors are checked to ensure the values fall within manufacturers
specifications.

[Temperature and Relative Humidity Sensors]{.underline}

The calibration of the current temperature and relative humidity probe
is checked by comparing it to the reference probe. The probe is then
replaced with one that has a current calibration. The calibration of the
newly replaced probe is also checked before returning to service.

### History

All equipment were calibrated at the manufacturer\'s prior to
installation.

A field check calibration on the instruments was made on September 18,
1999. All were within tolerances.

On Octobert 13, 2001, all wind speed, wind direction, and
temperature/humidity sensors were replaced and a field calibration check
on the instruments was completed. All were within tolerances.

Serial Numbers:

2m T/RH: W2110041 Wind Speed: U37502 Wind Direction: V34549

10m T/RH: W2110042 Wind Speed: U51103 Wind Direction: V35301

20m T/RH: W2110045 Wind Speed: U51102 Wind Direction: V36303

40m T/RH: W2110047 Wind Speed: U37501 Wind Direction: V34547

PWS calibrated.

On September 18, 2002, the 20m wind speed sensor was replaced.

Serial Number: W46210

On October 18, 2003, all wind speed sensors and direction sensors and
T/RH probes were replaced and a field calibration check on the
instruments was completed. All were within tolerances.

Serial Numbers:

2m T/RH: Y4320176 Wind Speed: W51302 Wind Direction: V36303

10m T/RH: Y4320177 Wind Speed: X09304 Wind Direction: W39549

20m T/RH: V4940011 Wind Speed: W51310 Wind Direction: V48511

40m T/RH: W2110042 Wind Speed: U51102 Wind Direction: W14224

PWS calibrated

On Sep 08, 2004 the 20m T/RH probe was replaced.

Serial Number: W2110041

On August 23, 2005 all wind speed and directions sensors and T/RH probes
were replaced and a field calibration check on the instruments was
completed. All were within tolerances.

Serial Numbers:

2m T/RH: V4940014 Wind Speed: U21110 Wind Direction: W23228

10m T/RH: U4940013 Wind Speed: W51301 Wind Direction: V34549

20m T/RH: Y4320178 Wind Speed: U46210 Wind Direction: V34547

40m T/RH: V4940011 Wind Speed: U21107 Wind Direction: W07444

PWS calibrated and CMH cleaned and calibrated.

On April 11, 2006 the CMH was cleaned and calibrated.

On July 18, 2006 the PWS was cleaned and calibrated.

On September 21, 2006 the 2m wind speed and direction sensors were field
calibration checked and the T/RH probe was replaced.

2m T/RH : Y321077

On October 18, 2006 the 10,20 and 40m lwind speed and direction sensors
were field calibration checked and the T/RH probes were replaced.

10m T/RH: A3930010

20m T/RH: W2110047

40m T/RH: A3930011

20m Wind Direction: U48511

40m Wind Direction: U48507

On October 19, 2006 the CMH was cleaned and calibrated.

On December 12, 2006 the CMH was cleaned.

On March 1, 2007 the CMH was cleaned and calibrated.

Sensor head 1619 installed.

Transmit logic board 1425 installed.

On March 14, 2007 the CMH was cleaned and calibrated.

On May 22, 2007 the 20m and 40m wind direction sensors were replaced:

20m Wind Direction: W14224

40m Wind Direction: V36303

## 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

See <http://science.arm.gov/tool/dod/showdod.php?Inst=mettwr4h>.

### Additional Documentation

This section is not applicable to this instrument.

## Glossary

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

## Acronyms

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

## Citable References

None.