ARM TR-068

> Surface Temperature and Humidity Reference System (SURTHREF) Handbook
>
> November 2005
>
> 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 7](#data-quality)

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

**Tables**

[1. Primary Variables 2](#__RefHeading___Toc119482736)

[2. Diagnostic Variables 4](#__RefHeading___Toc119482737)

[3. Quality Checks 5](#__RefHeading___Toc119482738)

[4. Dimension Variables 6](#__RefHeading___Toc119482739)

# General Overview

The Surface Temperature and Humidity Reference (SURTHREF) system is
intended to provide accurate reference values of ambient temperature and
relative humidity for comparison with radiosonde prelaunch values.

# Contacts

## Mentor

Michael T. Ritsche

Scientific Associate

Argonne National Laboratory

Bldg. 203

Argonne, IL 60439

Phone: (630) 252-1554

Fax: (630) 252-5498

Email: <mtritsche@anl.gov>

Barry M. Lesht

Scientist

Argonne National Laboratory

Bldg. 203

Argonne, IL 60439

Phone: (630) 252-4208

Fax: (630) 252-5498

Email: <bmlesht@anl.gov>

## Instrument Developer

**Data logger**

Campbell Scientific Inc.

815 W. 1800 N.

Logan, UT 84321

Phone: (801) 753-2342

Fax: (801) 750-9540

Website: [http://www.campbellsci.com](http://www.campbellsci.com/)

**Temperature/Relative Humidity Probe**

Vaisala

100 Commerce Way

Woburn, MA 01801-1068

Phone: (617) 933-4500

Fax: (617) 933-8029

Website: [http://www.vaisala.com](http://www.vaisala.com/)

Rotronic

160 E. Main St

Huntingtion, NY 11743

Phone: (631) 427-3898

Fax: (631) 427-3902

Website: <http://www.rotronic-usa.com/>

# Deployment Locations and History 

The SURTHREF is located at the Southern Great Plains (SGP) site's
Central Facility in Oklahoma and was installed in July 2005.

# 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

There are six temperature and relative humidity probes. Three probes
(V1, V2 and V3) are from Vaisala, Inc. Three probes (R1, R2 and R3) are
from Rotronic, Inc.

### Primary Variables and Expected Uncertainty

  ----------------------------------------------------------------------------------------------
  []{#__RefHeading___Toc119482736                                               
  .anchor}**Table 1**. Primary                                                  
  Variables.                                                                    
  --------------------------------- ---------------- ---------- --------------- ----------------
  **Quantity**                      **Variable**     **Unit**   **Measurement   **Resolution**
                                                                Interval**      

  Temperature V1 Average            temp_V1_avg      C          1 min           0.01

  Temperature V2 Average            temp_V2_avg      C          1 min           0.01

  Temperature V3 Average            temp_V3_avg      C          1 min           0.01

  Temperature R1 Average            temp_R1_avg      C          1 min           0.01

  Temperature R2 Average            temp_R2_avg      C          1 min           0.01

  Temperature R3 Average            temp_R3_avg      C          1 min           0.01

  Relative Humidity V1 Average      RH_V1_avg        \%         1 min           0.1

  Relative Humidity V2 Average      RH_V2_avg        \%         1 min           0.1

  Relative Humidity V3 Average      RH_V3_avg        \%         1 min           0.1
  ----------------------------------------------------------------------------------------------

  -------------------------------------------------------------------------
  **Table 2**. (contd)                                           
  --------------------- ---------------- ------- --------------- ----------
  Relative Humidity R1  RH_R1_avg        \%      1 min           0.1
  Averge                                                         

  Relative Humidity R2  RH_R2_avg        \%      1 min           0.1
  Average                                                        

  Relative Humidity R3  RH_R3_avg        \%      1 min           0.1
  Average                                                        

  Sonde Present Bit     count            N/A     1 min           1
  Flag                                                           

  Temperature V1        temp_V1_max      C       1 min           0.01
  Maximum                                                        

  Temperature V2        temp_V2_max      C       1 min           0.01
  Maximum                                                        

  Temperature V3        temp_V3_max      C       1 min           0.01
  Maximum                                                        

  Temperature R1        temp_R1_max      C       1 min           0.01
  Maximum                                                        

  Temperature R2        temp_R2_max      C       1 min           0.01
  Maximum                                                        

  Temperature R3        temp_R3_max      C       1 min           0.01
  Maximum                                                        

  Relative Humidity V1  RH_V1_max        \%      1 min           0.1
  Maximum                                                        

  Relative Humidity V2  RH_V2_max        \%      1 min           0.1
  Maximum                                                        

  Relative Humidity V3  RH_V3_max        \%      1 min           0.1
  Maximum                                                        

  Relative Humidity R1  RH_R1_max        \%      1 min           0.1
  Maximum                                                        

  Relative Humidity R2  RH_R2_max        \%      1 min           0.1
  Maximum                                                        

  Relative Humidity R3  RH_R3_max        \%      1 min           0.1
  Maximum                                                        

  Temperature V1        temp_V1_min      C       1 min           0.01
  Minimum                                                        

  Temperature V2        temp_V2_min      C       1 min           0.01
  Minimum                                                        

  Temperature V3        temp_V3_min      C       1 min           0.01
  Minimum                                                        

  Temperature R1        temp_R1_min      C       1 min           0.01
  Minimum                                                        

  Temperature R2        temp_R2_min      C       1 min           0.01
  Minimum                                                        

  Temperature R3        temp_R3_min      C       1 min           0.01
  Minimum                                                        

  Relative Humidity V1  RH_V1_min        \%      1 min           0.1
  Minimum                                                        

  Relative Humidity V2  RH_V2_min        \%      1 min           0.1
  Minimum                                                        

  Relative Humidity V3  RH_V3_min        \%      1 min           0.1
  Minimum                                                        

  Relative Humidity R1  RH_R1_min        \%      1 min           0.1
  Minimum                                                        

  Relative Humidity R2  RH_R2_min        \%      1 min           0.1
  Minimum                                                        

  Relative Humidity R3  RH_R3_min        \%      1 min           0.1
  Minimum                                                        
  -------------------------------------------------------------------------

#### 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 , 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 *^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

None.

### Diagnostic Variables

  --------------------------------- -------------------- ------------------
  []{#__RefHeading___Toc119482737                        
  .anchor}**Table 3**. Diagnostic                        
  Variables.                                             

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

  Standard Deviation of Temperature temp_V1_std          1 min
  V1                                                     

  Standard Deviation of Temperature temp_V2_std          1 min
  V2                                                     

  Standard Deviation of Temperature temp_V3_std          1 min
  V3                                                     

  Standard Deviation of Temperature temp_R1_std          1 min
  R1                                                     

  Standard Deviation of Temperature temp_R2_std          1 min
  R2                                                     

  Standard Deviation of Temperature temp_R3_std          1 min
  R3                                                     

  Standard Deviation of Relative    RH_V1_std            1 min
  Humidity V1                                            

  Standard Deviation of Relative    RH_V2_std            1 min
  Humidity V2                                            

  Standard Deviation of Relative    RH_V3_std            1 min
  Humidity V3                                            

  Standard Deviation of Relative    RH_R1_std            1 min
  Humidity R1                                            

  Standard Deviation of Relative    RH_R2_std            1 min
  Humidity R2                                            

  Standard Deviation of Relative    RH_R3_std            1 min
  Humidity R3                                            

  Logger Panel Temperature          logger_temp          1 min
  --------------------------------- -------------------- ------------------

### Data Quality Flags

  --------------------------------------------------------------------------------------------------
  []{#__RefHeading___Toc119482738                                                        
  .anchor}**Table 4**. Quality                                                           
  Checks.                                                                                
  --------------------------------- ---------------- --------------- --------- --------- -----------
  **Quantity**                      **Variable**     **Measurement   **Min**   **Max**   **Delta**
                                                     Interval**                          

  Sample Time                       qc_time          1 min                               

  Sonde Present Bit Flag            qc_count         1 min           0         60        N/A

  Average Temperature V1            qc_temp_V1_avg   1 min           -40       50        10

  Average Temperature V2            qc_temp_V2_avg   1 min           -40       50        10

  Average Temperature V3            qc_temp_V3_avg   1 min           -40       50        10

  Average Temperature R1            qc_temp_R1_avg   1 min           -40       50        10

  Average Temperature R2            qc_temp_R2_avg   1 min           -40       50        10

  Average Temperature R3            qc_temp_R3_avg   1 min           -40       50        10

  Average Relative Humidity V1      qc_RH_V1_avg     1 min           -2        104       30

  Average Relative Humidity V2      qc_RH_V2_avg     1 min           -2        104       30

  Average Relative Humidity V3      qc_RH_V3_avg     1 min           -2        104       30

  Average Relative Humidity R1      qc_RH_R1_avg     1 min           -2        104       30

  Average Relative Humidity R2      qc_RH_R2_avg     1 min           -2        104       30

  Average Relative Humidity R3      qc_RH_R3_avg     1 min           -2        104       30

  Maximum Temperature V1            qc_temp_V1_max   1 min           -40       50        10

  Maximum Temperature V2            qc_temp_V2_max   1 min           -40       50        10

  Maximum Temperature V3            qc_temp_V3_max   1 min           -40       50        10

  Maximum Temperature R1            qc_temp_R1_max   1 min           -40       50        10

  Maximum Temperature R2            qc_temp_R2_max   1 min           -40       50        10

  Maximum Temperature R3            qc_temp_R3_max   1 min           -40       50        10

  Maximum Relative Humidity V1      qc_RH_V1_max     1 min           -2        104       30

  Maximum Relative Humidity V2      qc_RH_V2_max     1 min           -2        104       30

  Maximum Relative Humidity V3      qc_RH_V3_max     1 min           -2        104       30

  Maximum Relative Humidity R1      qc_RH_R1_max     1 min           -2        104       30

  Maximum Relative Humidity R2      qc_RH_R2_max     1 min           -2        104       30

  Maximum Relative Humidty R3       qc_RH_R3_max     1 min           -2        104       30

  Minimum Temperature V1            qc_temp_V1_min   1 min           -40       50        10

  Minimum Temperature V2            qc_temp_V2_min   1 min           -40       50        10

  Minimum Temperature V3            qc_temp_V3_min   1 min           -40       50        10
  --------------------------------------------------------------------------------------------------

  ---------------------------------------------------------------------------
  **Table 5**. (contd)                                                 
  ---------------------- ---------------- -------------- ------ ------ ------
  Minimum Temperature R1 qc_temp_R1_min   1 min          -40    50     10

  Minimum Temperature R2 qc_temp_R2_min   1 min          -40    50     10

  Minimum Temperature R3 qc_temp_R3_min   1 min          -40    50     10

  Minimum Relative       qc_RH_V1_min     1 min          -2     104    30
  Humidity V1                                                          

  Minimum Relative       qc_RH_V2_min     1 min          -2     104    30
  Humidity V2                                                          

  Minimum Relative       qc_RH_V3_min     1 min          -2     104    30
  Humidity V3                                                          

  Minimum Relative       qc_RH_R1_min     1 min          -2     104    30
  Humidity R1                                                          

  Minimum Relative       qc_RH_R2_min     1 min          -2     104    30
  Humidity R2                                                          

  Minimum Reltive        qc_RH_R3_min     1 min          -2     104    30
  Humidity R3                                                          
  ---------------------------------------------------------------------------

### Dimension Variables

+---------------------+-------------+-----------+---------------------+
| []{#__RefHea        |             |           |                     |
| ding___Toc119482739 |             |           |                     |
| .anchor}**Table     |             |           |                     |
| 6**. Dimension      |             |           |                     |
| Variables.          |             |           |                     |
+---------------------+-------------+-----------+---------------------+
| **Quantity**        | *           | **Me      | **Unit**            |
|                     | *Variable** | asurement |                     |
|                     |             | I         |                     |
|                     |             | nterval** |                     |
+---------------------+-------------+-----------+---------------------+
| Base time in Epoch  | base_time   | 5 min     | seconds since       |
|                     |             |           | YYYY-mm-dd          |
|                     |             |           |                     |
|                     |             |           | XX:XX:XX X:XX       |
+---------------------+-------------+-----------+---------------------+
| Time offset from    | time_offset | 5 min     | seconds since       |
| base_time           |             |           | YYYY-mm-dd          |
|                     |             |           |                     |
|                     |             |           | XX:XX:XX X:XX       |
+---------------------+-------------+-----------+---------------------+
| Time offset form    | time        | 5 min     | seconds since       |
| midnight            |             |           | YYYY-mm-dd          |
|                     |             |           |                     |
|                     |             |           | XX:XX:XX X:XX       |
+---------------------+-------------+-----------+---------------------+
| North latitude      | lat         | 5 min     | degrees             |
+---------------------+-------------+-----------+---------------------+
| East longitude      | lon         | 5 min     | degrees             |
+---------------------+-------------+-----------+---------------------+
| Altitude            | alt         | 5 min     | meters above sea    |
|                     |             |           | level               |
+---------------------+-------------+-----------+---------------------+

NOTE: lat/lon/alt refers to the ground where the instrument is sited and
not the height of the sensor.

## Annotated Examples

None.

## User Notes and Known Problems

None.

## Frequently Asked Questions

None.

# 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

None.

## 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 Atmospheric Radiation Measurement
(ARM) Program are met through the analysis and processing of existing
data products into value-added products (VAPs). Despite extensive
instrumentation deployed at the ARM 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
to fill unmet measurement needs, but 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. Instead, a QME adds value to the
input data streams 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 web page at <http://www.arm.gov/data/vaps.stm>.

# Instrument Details

## Detailed Description

List of Components

**Temperature and relative humidity sensors:**

-   three Vaisala HMP-4D Series probes

-   three Rotronic MP100H Series probes.

**Data logger:** Campbell Scientific Model CR23X Micrologger.

**Meteorological Instrument Shelter:** The shelter is a standard NWS
"Stevenson screen" modified to allow for operator access on two sides.
The shelter dimensions are 20 inches by 30 inches by 34 inches.

**Aspirated Chamber:** The chamber is fabricated from white
polypropylene plastics. Its dimensions are 11 inches by 13 inches by 18
inches (volume = 1.49 feet^3^). One end is open and covered with a
removable plate containing a 7 inch x 7.5 inch access port. Two muffin
fans, each rated at 115 cfm are mounted at the far end. The fans produce
an estimated face flow of 10.49 fps or 3.2 m/s. The chamber has six
sensor ports on its top surface to accommodate standard temperature and
relative humidity probes.

**Sonde positioning platform:** A polypropylene platform is mounted
approximately 1 inch above the bottom of the aspirated chamber. The
platform is equipped with moveable guides for positioning radiosondes. A
user-controlled switch is mounted on the side of the Aspirated Chamber
to indicate when a radiosonde is placed in or removed from the chamber.

### System Configuration and Measurement Methods

The SURTHREF system is intended to be used as a ground reference point
for radiosonde launches. Radiosondes are placed inside the aspirator so
that comparisons between the six T/RH probes and the radiosonde can be
accomplished. It is possible that in the future a VAP will be created so
that the radiosonde surface values can be corrected. For there to be an
exact determination of when the radiosonde is inside the aspirator box a
user operated switch is installed. When the operator places the
radiosonde inside the aspirator box they flip the switch. The data
logger program counts the number of seconds of each minute that the
switch is in the "up" position. Any count greater than zero suggests
that the radiosonde is in the aspirator.

The data logger measures each input once every second. The temperature
and relative humidity data are averaged for each of the six probes once
per minute and minimums and maximum are calculated along with a total
count of how many seconds the "Radiosonde Present" switch was in the up
position.

### Specifications

**Temperature and Relative Humidity Probes:**

**Vaisala HMP-45D T/RH probe:**

**Temperature:** Precision: 0.01 C; Uncertainty: See "Data Acquisition
Errors"

**RH:** Precision: 0.1% RH; Uncertainty: +/-2.0% RH (0% to 90% RH),
+/-3.0% RH (90% to 100% RH)

**Rotronic MP100H T/RH probe:**

**Temperature:** Precision: 0.01 C; Uncertainty: +/-0.2 C.

**RH:** Precision: 0.1% RH; Uncertainty: +/-1.5%.

**Data Acquisition Errors**

The Campbell Scientific CR23X A/D converter accuracy is +/-0.1% of
full-scale range. The time base accuracy is +/-1 minute per month, or
about 23 ppm. The collector computer checks the data logger clock once
per day and corrects it if it is off by more than 2 seconds.

## Theory of Operation

The SURTHREF system is a combination of three temperature and relative
humidity probes from two different manufacturers for six probes.
Although the primary use of the system is intended to provide accurate
reference values of ambient temperature and relative humidity for
comparison with radiosonde prelaunch values, the system includes a data
logger to record time series of the measured variables.

## Calibration

### Theory

### Procedures

See Section 7.4.1 of the [SURTHREF User
Manual](http://www.arm.gov/publications/tech_reports/handbooks/surthref_user.pdf)
for procedures.

### History

The SURTHREF System was installed in July 2005 with recently calibrated
sensors.

## Operation and Maintenance

### User Manual

See the [SURTHREF User
Manual](http://www.arm.gov/publications/tech_reports/handbooks/surthref_user.pdf).

### Routine and Corrective Maintenance Documentation

This section is not applicable to this instrument.

### Software Documentation

ARM netCDF file header descriptions may be found for the SURTHREF system
at http://science.arm.gov/tool/dod/showdod.php?Inst=SURTHREF.

### Additional Documentation

This section is not applicable to this instrument.

## Glossary

**Relative humidity:** Percentage of saturated vapor pressure at the
specified temperature.

See the ARM Glossary at <http://www.arm.gov/about/glossary.stm>.

## Acronyms

AC alternating current

A/D Analog to Digital converter

BBSS balloon-borne sounding system

DQA Data Quality Assessment

NIST National Institute of Standards and Technology

QME Quality Measurement Experiment

RH Relative Humidity

RMSE root-mean-square error

SGP Southern Great Plains

T/RH temperature/relative humidity (sensor)

VAP value-added product

Also see the ARM Acronyms and Abbreviations at
<http://www.arm.gov/about/acronyms.stm>.

## Citable References

None.