ARM TR-018

> Millimeter Wave Cloud Radar (MMCR) Handbook
>
> December 2004
>
> K. B. Widener
>
> K. Johnson
>
> 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
1](#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 2](#data-quality)

[7. Instrument Details 3](#instrument-details)

# Tables {#tables .Heading-Front}

Table 1. MMCR Deployment Locations and
Dates..................................................................1

Table 2. MMCR Data Stream Availability [2](#__RefHeading___Toc501422275)

Table 3. Primary Variables [3](#__RefHeading___Toc501422276)

Table 4. Secondary Variables [4](#__RefHeading___Toc501422277)

Table 6. Dimension Variables [6](#__RefHeading___Toc501422278)

Table 7. ARM SGP Site Operation Parameters 1997.09.15 -- 2004.08.10
[4](#__RefHeading___Toc501422279)

Table 8. Calibration Information [6](#__RefHeading___Toc501422280)

Table 9. MMCR Antenna Table [6](#__RefHeading___Toc501422281)

# General Overview

The Millimeter Cloud Radar (MMCR) systems probe the extent and
composition of clouds at millimeter wavelengths. The MMCR is a
zenith-pointing radar that operates at a frequency of 35 GHz. The main
purpose of this radar is to determine cloud boundaries (e.g., cloud
bottoms and tops). This radar will also report radar reflectivity (dBZ)
of the atmosphere up to 20 km. The radar possesses a doppler capability
that will allow the measurement of cloud constituent vertical
velocities.

# Contacts

## Mentor

Kevin Widener\
Pacific Northwest National Laboratory\
P.O. Box 999\
Richland, WA 99352\
Phone: 509-375-2487

Fax: 509-375-6736\
[kevin.widener@pnl.gov](../kevin.widener@pnl.gov)

Karen Johnson\
Environmental Sciences Department\
Brookhaven National Laboratory\
Upton, NY 11973\
Phone: 631-344-5952

Fax: 631-344-2060\
<kjohnson@bnl.gov>

## Instrument Developer

Ken Moran, Project Leader\
NOAA Environmental Research Laboratories\
Environmental Technology Laboratory\
325 Broadway, R/E/ET4\
Boulder, CO 80303\
Phone: 303- 497-6575\
<Ken.Moran@noaa.gov>

# Deployment Locations and History

**Table 1.** MMCR Deployment Locations and Dates

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

  SGP/C1         1996/11/08                              Operational

  NSA/C1         1998/03/25                              Operational

  TWP/C1         1999/06/14                              Operational

  TWP/C2         1998/10/22                              Operational

  TWP/C3         2002/03/06                              Operational
  -------------- -------------------- ------------------ ----------------

The first five MMCRs were built by the National Oceanic and Atmospheric
Administration's (NOAA\'s) Environment Technology Laboratory (ETL)in
Boulder, Colorado. The first unit is now operating at the Southern Great
Plains (SGP) Central Facility. The second unit is currently operating at
the North Slope of Alaska/Adjacent Artic Ocean (NSA/AAO) site, and the
third and forth units are located at the Tropical Western Pacific's
Atmospheric Radiation and Cloud Station (TWP\'s ARCS-1) on Manus Island
and ARCS-2 on Nauru Island. The fifth unit is a hot spare/development
radar located at NOAA/ETL. The sixth radar was built by Radian
International; it is currently installed at Darwin, Northern Territory,
Australia at the ARCS-3 site.

In addition to the ARM MMCRs, NOAA/ETL fielded an identical radar during
the Surface Heat Budget of the Arctic Ocean (SHEBA)
([http://sheba.apl.washington.edu](http://sheba.apl.washington.edu/))
experiment from the fall of 1997 to the fall of 1998.\
\
A new MMCR data processor, the C-40, was developed by NOAA/ETL and
installed at the SGP and NSA sites in September 2003 and April 2004,
respectively. Along with the new MMCR radar computer, the C-40 provides
faster data collection and much improved instrument reliability.
Upgrades are planned for the TWP sites in the coming year.

# Near-Real-Time Data Plots

Near-real-time MMCR data plots are available from the Data Quality
Office (DQO) for each site. Thumbnail images of the most recent data are
available from the [ARM DQHandS Plot
Browser](http://dq.arm.gov/plotbrowser/) website. Select the site of
interest and select the associated MMCR data stream. For NSA, choose
'nsammcrmom,' for SGP select 'sgpmmcrmom,' and for the TWP sites, select
'twpmmcrcal.' Then choose either the 'list' or 'thumbnail' search
option. The 'list' option provides a list of available plots; the
'thumbnail' option presents thumbnails images. The most recent week of
data is the default date range.

DQO plots can also be accessed individually via
<http://dq.arm.gov/PLOTS>. MMCR plots for each site are accessible as
listed below. In each case, select the date of interest from the page
that appears:

NSA: <http://dq.arm.gov/PLOTS/NSA/nsammcrmom/>

SGP: <http://dq.arm.gov/PLOTS/SGP/sgpmmcrmom/>

TWP: <http://dq.arm.gov/PLOTS/TWP/twpmmcrcal/>

> (Individual TWP site plots for C1, C2 are accessible once a date is
> selected. Plots for TWP-C3 are not yet available from the DQO.)

# Data Description and Examples

MMCR data are available from the [ARM Data
Archive](http://www.arm.gov/data) in the following data streams:
mmcrmom, mmcrcal, mmcrmoments, and mmcrspecmom. This table indicates
which data streams are available at each site and time period:

[]{#__RefHeading___Toc501422275 .anchor}Table 2. MMCR Data Stream
Availability

  --------------- ---------------------------- --------------------------
  **Site**        **Date Range**               

                  **mmcrcal, mmcrmoments**     **mmcrmom**

  NSA             1999.03 - 2004.04.12         2004.04.13 - Present

  SGP             1996.11 - 2003.09.08         2003.09.09 - Present

  TWP-C1          1999.08 - Present            

  TWP-C2          1998.11 - Present            

  TWP-C3          2002.03 - Present            
  --------------- ---------------------------- --------------------------

The data streams 'mmcrcal' and 'mmcrmoments' together make up a complete
set of MMCR data. The 'mmcrmom' data stream alone contains all the MMCR
data fields.

## Data File Contents

### Primary Variables and Expected Uncertainty

The following tables show the primary quantities measured by the MMCR
for the mmcrmom data stream, followed by the mmcrcal, mmcrmoments data
streams.

[]{#__RefHeading___Toc501422276 .anchor}Table 3. Primary Variables

#  {#section .Heading-Front}

# mmcrmom Data Stream (current SGP, NSA) {#mmcrmom-data-stream-current-sgp-nsa .Heading-Front}

  ----------------------------- ----------------------------------- -----------------
  **Variable**                  **Description**                     **Uncertainty**

  Reflectivity                  MMCR Reflectivity (time, height),   0.5dB
                                in dBZ                              

  MeanDopplerVelocity           MMCR Mean Doppler Velocity (time,   0.1 m/s
                                height), in m/s                     

  SpectralWidth                 MMCR Spectral Width (time, height), 0.1 m/s
                                in m/s                              

  CircularDepolarizationRatio   MMCR Circular Depolarization Ratio  
                                (time, height), dB                  
  ----------------------------- ----------------------------------- -----------------

# mmcrcal / mmcrmoments Data Streams (current TWP, historical SGP, NSA) {#mmcrcal-mmcrmoments-data-streams-current-twp-historical-sgp-nsa .Heading-Front}

+--------------+-----------+-------------------------------+----------+
| **Variable** | # Data    | **Description**               | # U      |
|              | Stream {# |                               | ncertain |
|              | data-stre |                               | ty {#unc |
|              | am .Headi |                               | ertainty |
|              | ng-Front} |                               |  .Headin |
|              |           |                               | g-Front} |
+--------------+-----------+-------------------------------+----------+
| Reflectivity | mmcrcal   | MMCR Reflectivity             | 0.5 dB   |
|              |           | (time-height), in dBZ         |          |
+--------------+-----------+-------------------------------+----------+
| MeanDop      | mm        | MMCR Mean Doppler Velocity    | 0.1 m/s  |
| plerVelocity | crmoments | (time-height), in m/s         |          |
+--------------+-----------+-------------------------------+----------+
| S            | mm        | MMCR Spectral Width (time,    | 0.1 m/s  |
| pectralWidth | crmoments | height), in m/s               |          |
+--------------+-----------+-------------------------------+----------+

The overall uncertainties for the primary quantities measured are as
follows:

-   Measurement accuracy: 0.5 dB over receiver dynamic range

-   Doppler resolution: less than 0.1 meters/second.

-   

#### 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

[]{#__RefHeading___Toc501422277 .anchor}Table 4. Secondary Variables

# mmcrmom Data Stream {#mmcrmom-data-stream .Heading-Front}

  ------------------------------- ----------------------------------------------
  **Variable**                    **Description**

  GateSpacing                     Gate Spacing (ns) for each mode

  InterPulsePeriod                Inter-Pulse Time Period (ns) for each mode

  MinimumDetectableReflectivity   Minimum Detectable Reflectivity (dBZ), hourly
                                  for each mode & height

  ModeNum                         Operating Set for each Record

  NoiseLevel                      Mean Noise Level (dB), for each time & height

  NumCodeBits                     Number of Coded Bits for each mode

  NumCoherentIntegrations         Number of Coherent Integrations done for each
                                  mode

  NumFFt                          Number of FFT points used for each mode

  NumSpectralAverages             Number of Spectral Averages done for each mode

  NyquistVelocity                 Nyquist Velocity (m/s), for each mode

  Power                           Uncalibrated Power (dB), for each time &
                                  height

  PulseWidth                      Pulse Width (ns), for each mode

  RadarConstant                   Radar Constant (dB), hourly for each mode

  RangeCorrectedPowwer            Range-Corrected Calibrated Power (dBm), for
                                  each time & height

  RxGain                          Receiver Gain (dB) for each mode

  SignalToNoiseRatio              Signal-to-Noise Ratio (dB), for each time &
                                  height

  SkyNoiseLevel                   Sky Noise Level (dB), for each mode

  StartGateDelay                  Delay to first range gate (ns)
  ------------------------------- ----------------------------------------------

See [MMCR Data Stream Format
Changes](http://www.gim.bnl.gov/armclouds/mmcr/mmcrMomNewVsOldDataStreams.html)
for differences between the new mmcrmom data stream fields and the
mmcrcal, mmcrmoments fields.

### Diagnostic Variables

**Table 5.** Diagnostic Variables

**mmcrmom Data Stream**

+----------------------+-----------------------------------------------+
| **Variable**         | **Description**                               |
+----------------------+-----------------------------------------------+
| AvgNoiseLevel        | Average Noise Level (S/N \< 0), dB for each   |
|                      | time                                          |
+----------------------+-----------------------------------------------+
| CalCheckLevel        | Receiver Calibration Check Level (dB) for     |
|                      | each mode                                     |
+----------------------+-----------------------------------------------+
| CalCheckTime         | Time stamp for receiver calibration check     |
+----------------------+-----------------------------------------------+
| ClutterHeight        | Maximum height of clutter removal (m)         |
+----------------------+-----------------------------------------------+
| DCFilterONOFF        | DC Filtering on-off status                    |
+----------------------+-----------------------------------------------+
| DataQualityStatus    | Data Quality Status, for each time (see       |
|                      | Section 5.1.4)                                |
+----------------------+-----------------------------------------------+
| ModeDescription      | Description of each radar mode                |
+----------------------+-----------------------------------------------+
| NumReceivers         | Total number of receivers in use, for each    |
|                      | mode                                          |
+----------------------+-----------------------------------------------+
| Pea                  | Peak transmitted power, averaged over an hour |
| kTransmittedPowerAvg | (dBm), for each hour                          |
+----------------------+-----------------------------------------------+
| ReceiverMode         | For each mode, Identifies what multiple       |
|                      | receiver mode does:                           |
|                      |                                               |
|                      | 0 = single polarization                       |
|                      |                                               |
|                      | 1 = dual polarization                         |
|                      |                                               |
|                      | 2 = dual antenna                              |
|                      |                                               |
|                      | 3 = added loss in receiver (precip mode)      |
+----------------------+-----------------------------------------------+
| ReceiverNumber       | Number of receiver in use, for each mode.     |
|                      |                                               |
|                      | Dual-polarization: 1 = co-channel, 2 =        |
|                      | cross-channel                                 |
|                      |                                               |
|                      | Dual-antenna: 1 = std antenna, 2 = aux.       |
|                      | antenna                                       |
+----------------------+-----------------------------------------------+
| Rx290Klevel          | Receiver 290K level (dB) for each mode        |
+----------------------+-----------------------------------------------+
| RxCalTimeStamp       | Receiver calibration check time stamp (s)     |
+----------------------+-----------------------------------------------+
| TWTStatusCode        | TWT Status Code, 9-digit code, 3 left-most    |
|                      | digits indicate % of time TWT produced        |
|                      | acceptable peak transmitted power values (see |
|                      | Section 5.1.4)                                |
+----------------------+-----------------------------------------------+
| TimeAvg              | Time associated with hourly averaged values   |
|                      | (s)                                           |
+----------------------+-----------------------------------------------+
| WindowingONOFF       | Windowing on-off status                       |
+----------------------+-----------------------------------------------+
| qc_time              | QC checks on time intervals between           |
|                      | successive records (see Section 5.1.4)        |
+----------------------+-----------------------------------------------+

See [MMCR Data Stream Format
Changes](http://www.gim.bnl.gov/armclouds/mmcr/mmcrMomNewVsOldDataStreams.html)
for differences between the new mmcrmom data stream fields and the
mmcrcal, mmcrmoments fields.

### Data Quality Flags

**DataQualityStatus** (mmcrmom data stream only): DataQualityStatus has
a value for each time value. It gives information on whether
Reflectivity and RangeCorrectedCalibratedPower exist for this time and
if so, how they were calibrated.

DataQualityStatus:

1 = No values for Reflectivity and RangeCorrectedCalibratedPower

> 2 = Abbreviated calibration was applied: Calibrated Power = f(RxGain)

4 = Using default radar constant; No recent entry for Peak Power

8 = TWT fault during this file; Possible lost data

**qc_time** (mmcrmom data stream only): Contains the results of quality
checks on sample time. This field has a value at each sample time. The
qc_time values are calculated by comparing each sample time with the
previous time. In the table below, Delta_time = t\[n\] -- t\[n-1\] .

qc_time:

1 = Delta_time is within expected interval.

> 2 = Delta_time is zero: Duplicate sample times

4 = Delta_time is greater than expected.

8 = Delta_time is less than expected.

**TWTStatusCode** (mmcrmom data stream only): This field reports on
traveling wave tube (TWT) status once per hour. A nine-digit code is
reported, as follows:

TWTStatusCode digit #, from left to right:

> Digits 1-3 = Percentage of time the TWT had peak power within
> acceptable bounds (0-100%)
>
> Digit 4 = \# TWT retries at 55 minutes past the hour (values from 0-5)
>
> Digit 5 = \# TWT retries at 45 minutes past the hour (values from 0-5)
>
> Digit 6 = \# TWT retries at 35 minutes past the hour (values from 0-5)
>
> Digit 7 = \# TWT retries at 25 minutes past the hour (values from 0-5)
>
> Digit 8 = \# TWT retries at 15 minutes past the hour (values from 0-5)
>
> Digit 9 = \# TWT retries at 05 minutes past the hour (values from 0-5)

For example, a code of 072030020 indicates that 72% of the time TWT
power was acceptable, there were 3 retries at 45 minutes past the hour
and 2 retries at 15 minutes past the hour. Note that after 5 retries the
TWT would be shut down due to a fault.

### Dimension Variables

[]{#__RefHeading___Toc501422278 .anchor}Table 6. Dimension Variables

# mmcrmom Data Stream {#mmcrmom-data-stream-1 .Heading-Front}

  ----------------------------------- -----------------------------------
  **Variable**                        **Description**

  alt                                 Altitude, meters above mean sea
                                      level, of ground instrument is
                                      sited on

  base_time                           Base time for file, in seconds
                                      since 1/1/1970 00:00:00 GMT

  heights                             Range heights in meters above mean
                                      sea level of data collection for
                                      each mode (center of radar sample
                                      volume)

  lat                                 North latitude in degrees

  lon                                 East longitude in degrees

  time                                Time offset in seconds from
                                      midnight on file's collection date

  time_offset                         Time offset in seconds from
                                      base_time
  ----------------------------------- -----------------------------------

## Annotated Examples

Below are plots of Reflectivity, Mean Doppler Velocity, and Spectral
Width, from top to bottom, for an SGP day. Areas of non-hydrometeor
"clutter" are shown (typically insects, bits of vegetation or dust).
Clutter is often seen at low levels at the SGP site and can be difficult
to distinguish from hydrometeor echoes. The [ARSCL
VAP](http://science.arm.gov/vaps/arscl.stm) generally does a good job of
identifying and eliminating clutter echoes (see Section 6.4 below for
more information). The "bright band" is also indicated on the plot. This
is an area of enhanced reflectivity caused by melting ice particles.

![](media/image1.png){width="6.5in" height="4.875in"}Below are time vs.
height plots of Reflectivity (for SGP 2004.02.29) for radar modes 1
(Boundary Layer), 2 (Cirrus), 3 (General) and 4 (Precipitation). Mode 1
samples the lowest kilometers only, but is more sensitive there than the
other modes. Mode 2 is the most sensitive mode above 3 kilometers but
sometimes has pulsecoding artifacts. These spiked artifacts in the
presence of strong reflectivity gradients are caused by imperfect pulse
decoding and can contaminate adjacent areas with weaker returns. Mode 3
is a good general mode, but is not quite as sensitive to thin clouds as
Mode 2. Mode 4 is less sensitive than modes 2 and 3, but it does not
saturate as readily in higher reflectivity regions, such as drizzle.

![](media/image2.png){width="6.5in" height="4.875in"}

## User Notes and Known Problems

MMCR processor upgrades are underway at all ARM Climate Research
Facility (ACRF) sites. When the upgrade is done at a site, the MMCR data
streams change from 'mmcrcal' and 'mmcrmoments' to a single data stream,
'mmcrmom.' The SGP and NSA sites were upgraded on 2003.09.09 and
2004.04.13, respectively. It is expected that the TWP sites will be
upgraded in early 2005.

A comparison of the fields in the mmcrmom data streams with those in the
mmcrcal and mmcrmoments data streams is available here:

<http://www.gim.bnl.gov/armclouds/mmcr/mmcrMomNewVsOldDataStreams.html>

MMCR spectral data, in data stream \"mmcrspecmom\" are also available at
sites with the upgraded MMCR processor (currently SGP and NSA). The
mmcrspecmom data can be ordered through the usual ARM Archive web
\"Power Interface.\" But, please note that approximately 8 GB of
spectral data are collected each day. Data requests covering a few hours
to a few days will be accepted via the web interface. Spectral data
availability at the archive lags several weeks behind data collection
time because the data are periodically shipped to the archive on disks.

## Frequently Asked Questions

**How is the minimum measurable height determined?**

There are two system delays that must be considered: the interval
between the time when the pulse is transmitted and when the return
signals are first sampled by the receiver detector (StartGateDelay
variable in the moments and spectra files), and the time it takes the
received signal to reach the detector from the receive antenna (RxDelay
variable in the moments and spectra files). Hence, subtracting the
RxDelay from the StartGateDelay yields the time that the pulse was
moving through the atmosphere (transit time). The measurement height is
0.5\*transit_time. Thus,

Min. Meas. Hgt = (0.5(StartGateDelay - RxDelay)) x c

where the delays are expressed in seconds and c is the speed of light.
For mode 1, StartGateDelay = 1200 ns and RxDelay = 500 ns, so
350e-9(3.0e8) = 105 m AGL (above ground level). In the data files, the
heights are in MSL (mean sea level). The radar is located at
approximately 318 MSL, so the lowest measurement height in the data is
105 m + 318 m = 423 m.\
\
**How does pulse coding affect the lowest measurement height?**

Essentially, complementary code renders the first n-1 heights useless,
where n is the number of coded bits. Therefore, an 8-bit code applied in
a situation where the enhanced vertical resolution is 45 m means that
the first usable data is from 8\*45 = 360 m + 105 m = 465 m AGL. Note
that 105 m is the height of the lowest measurement height.\
\
**Is the MMCR polarization diverse?**

Until the recent SGP MMCR upgrade, the MMCR has not been
polarization-diverse at any sites. At the NSA and TWP sites, and at the
SGP site prior to 2004.08.11, the MMCR transmits and receives at the
same polarization; this is not adjustable.

As of 2004.08.11, the SGP is running a polarization mode, with
polarization alternating from horizontal to vertical from pulse to
pulse.

**What is the lifetime of the transmitter tube?**

The advertised lifetime for the Traveling Wave Tube Amplifier (TWTA) is
20,000 hours. This amounts to 2.3 years of continuous operation.\
\
**What index of refraction for water is used to computer reflectivity
(Kw)?**

0.98

# Data Quality

## Data Quality Health and Status

The [Data Quality Office](http://dq.arm.gov/) (DQO) website has links to
several tools for inspecting and assessing MMCR data quality:

-   [DQ HandS](http://dq.arm.gov/cgi-bin/dqmenu.pl) (Data Quality Health
    and Status)

-   [DQ HandS Plot Browser](http://dq.arm.gov/plotbrowser/)

-   [NCVweb](http://dq.arm.gov/ncvweb/ncvweb.cgi): Interactive web-based
    tool for viewing ARM data

Plots of reflectivity, Doppler radial velocity, and Doppler spectral
width provide a good indicator of whether the system is operational or
not.

## Data Reviews by Instrument Mentor

Data reviews are done weekly. Monthly assessments will be provided here
in the future.

## Data Assessments by Site Scientist/Data Quality Office

All DQO and most Site Scientist techniques for checking have been
incorporated within [DQ HandS](http://dq.arm.gov/) and can be viewed
there.

## Value-Added Products 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
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. 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,
etc.. For more information, see [VAPs and
QMEs](http://www.arm.gov/data/vaps.stm).

The major MMCR-related VAP is called
[ARSCL](http://science.arm.gov/vaps/arscl.stm), which stands for "Active
Remote Sensing of Clouds." ARSCL combines data from the MMCR, the
micropulse lidar (MPL), Vaisala ceilometer (VCEIL) and surface
precipitation measurements to provide a time series of hydrometeor
height distributions and best estimates of radar reflectivities,
vertical velocities, and Doppler spectral widths. See the [ARSCL
VAP](http://science.arm.gov/vaps/arscl.stm) documentation and the [ARM
Tech.
Memo](http://www.arm.gov/publications/tech_reports/armvap-002-1.pdf) for
additional information.

# Instrument Details

## Detailed Description

### List of Components

At all sites:

-   Applied Systems Engineering TWTA

-   Spacek Labs Coherent Up/Down Converter (CUDC)

-   EMS Switching Circulators

-   Alpha Cassegrain antenna

-   4-Port Circulators

-   NOAA/ETL Pulse Controller

-   Radian Receiver/Modulator

-   Radian Interface

-   IOtech Analog Multiplexer

-   IOtech Analog-to-Digital Converter

-   Tektronix Oscilloscope

NSA and SGP only:

-   Windows NT Data Management System Computer, running LabView

-   Windows NT Radar Control computer, running LapXM software

TWP sites only:

-   Solaris-PC Data Management System computer

-   OS/2 Radar Control computer

### System Configuration and Measurement Methods

The MMCR system consists of the radar, data acquisition/control
subsystem, enclosures, cables, and accessories so that it will be
operable in a semi-autonomous mode. For the purposes of this
specification, semi-autonomous operation is defined as a mode wherein an
operator is required only to power up and power down the system. Once
powered up, the MMCR will automatically enter a standby mode ready to
begin taking data.

### Specifications

**Radar specifications are as follows (Moran et al. 1997):**

  ---------------------------------- ------------------------------------
  Frequency                          34.86 GHz (Wavelength 8.66mm,
                                     Ka-band)

  Peak Transmitted Power             100 W

  Maximum Duty Cycle                 25%

  Antenna Diameter                   see table under Calibration History

  Antenna Gain                       see table under Calibration History

  Beam Width (full-width,            see table under Calibration History
  half-maximum)                      

  PRF (max)                          20 kHz
  ---------------------------------- ------------------------------------

**MMCR Mode Sequence and Characteristics**

MMCR upgrades are underway at all sites, so details of mode
characteristics and sequencing are changing. For detailed information on
operational parameters at each site for specific time ranges, please see
[MMCR Operational
Parameters.](http://www.gim.bnl.gov/armclouds/mmcr/MMCR_Operating_Parameters.html)

Here the historical modes and sequencing will be discussed, followed by
a description of recent changes at SGP and NSA.

**Current TWP and Historical NSA, SGP Mode Sequence**

Historically, the MMCR has cycled through 4 modes with combined dwell
and processing times of approximately 9 seconds for each mode. The mode
parameters have varied over time and at each site. For detailed
information on operational parameters at each site for specific time
ranges, please see [MMCR Operational
Parameters](http://www.gim.bnl.gov/armclouds/mmcr/MMCR_Operating_Parameters.html).
As an example, here are the parameters in effect at SGP from September
1997 through August 10, 2004:

[]{#__RefHeading___Toc501422279 .anchor}Table 7. ARM SGP Site Operation
Parameters 1997.09.15 -- 2004.08.10

  -------------------------- ------------- ------------ ----------- -----------------
  **Radar Parameter**        **Operating                            
                             Mode**                                 

                             **1\          **2\         **3\        **4\
                             Stratus**     Cirrus**     General**   Precipitation**

  Inter-Pulse Period         68            126          106         106
  (microsec)                                                        

  Pulse Width (microsec)     0.3           0.6          0.6         0.6

  Gate Spacing (microsec)    0.3           0.6          0.6         0.6

  Number of Gates            110           167          167         167

  Coherent Averages          10            6            6           1

  Spectral Averages          64            21           60          29

  FFT Length                 64            64           64          128

  Coded Bits                 8             32           0           0

  Dwell Time (sec)           0.7           0.6          1.0         0.7

  Obsv./Processing Time      9             8.7          8.5         9
  (sec)                                                             

  Minimum Detectable Signal  \~ -132       \~ -132      \~ -132     \~ -132
  (dBm)                                                             
  -------------------------- ------------- ------------ ----------- -----------------

**Current NSA Mode Sequence**

At NSA, the installation of the new C40 processor on 2004.04.14 was
accompanied by a new mode sequence to provide more frequent
boundary-layer (BL)sampling:

BL GE BL CI BL GE BL PR

Here BL is analogous to the Stratus mode, CI is the Cirrus mode, GE is
the General mode, and PR is the Precipitation mode. The combined dwell
and processing times for each mode are much shorter with the new
processor, approximately 2 seconds per mode. The entire mode sequence
completes in just under 18 seconds.

**Current SGP Mode Sequence**

At SGP, a dual-polarization mode was added on August 11, 2004. At this
time the mode sequence and timing were also modified to provide more
frequent BL sampling. A new precipitation mode was also added, with
about 27 dB of additional loss in the receiver to reduce receiver
saturation during light precipitation. The SGP mode sequence is:

BL CI BL GE BL PR BL GE BL CI BL GE BL PO BL GE

where BL is the boundary layer mode, CI is the cirrus mode, GE is the
general mode, PR is the precipitation mode, and PO is the
dual-polarization mode. Dwell and processing time for each mode is
approximately 2 seconds, with the complete mode sequence completing in
about 32.5 seconds.

## Theory of Operation

The MMCR works by transmitting a pulse of millimeter-wave energy from
its transmitter through the antenna. The energy propogates through the
atmosphere until it hits objects that reflect some of the energy back to
the MMCR. These objects can be clouds, precipitation, insects, spider
webs, man-made objects, etc. The same antenna is used to receive the
return signal. The received signal is split into two channels, termed I
and Q (for in-phase and quadrature). A digital signal processor
processes these signals and provides power, Doppler velocity, and
spectral width. The power measurement is processed by knowing the
MMCR\'s calibration coefficient to provide the radar reflectivity.\
\
Looking at the meteorlogical radar range equation gives insight as to
how the MMCR works and what parameters affect its sensitivity. Any
radar\'s sensitivity is proportional to the transmit power, the square
of the antenna gain, and the square of the radar\'s wavelength. The
sensitivity is inversely proportional to the square of the range from
the radar to the target.

## Calibration

### Theory

There are several systems within the radar that require calibration at
regular intervals. The values obtained from these calibrations are
stored as constants, polynomials, or curves in the calibration files or
programs. These are used by the software to convert raw radar moment
files to range-corrected power (dBm) and reflectivity (dBZ) data in
netCDF format and sent to the site data system (SDS).

Below is a listing of the calibration constants stored in the system and
the required frequency of calibration.

[]{#__RefHeading___Toc501422280 .anchor}Table 8. Calibration Information

+-----------------------------------------------------------------------+
|                                                                       |
|  ---------------- -------------------- ------------- ---------------- |
|                                                                       |
|  **Constant**     **Storage Location** **Interval    **Storage Type** |
|                                         (months)**                    |
|                                                                       |
|   Inclinometer     MMCR Operating       120           Polynomial      |
|                    Computer                                           |
|                                                                       |
|   RF noise diode   MMCR Data Computer   12            Constant        |
|                                                                       |
|   Receiver Path    Calibration Files    12            Constant        |
|   Loss                                                                |
|                                                                       |
|   Transmitter Path Calibration Files    12            Constant        |
|   Loss                                                                |
|                                                                       |
|   TWT RF Test      Manual               60            Constant        |
|   Point                                                               |
|                                                                       |
|   Forward Power    MMCR Data Computer   36            Polynomial      |
|   Monitor                                                             |
|                                                                       |
|   RF Attenuator    Internal             36            Polynomial      |
|                                                                       |
|   IF Attenuator    Manual               36            Constant        |
|                                                                       |
|   Radar Parameters Calibration Files    6             Curve           |
|                                                                       |
|   Noise Diode Path Manual               36            Constant        |
|   Loss                                                                |
|                                                                       |
|   Antenna Gain     Calibration Files    60            Constant        |
|                                                                       |
|   Receiver         Calibration Files    36            Constant        |
|   Bandwidth                                                           |
|                                                                       |
|   Range Delay      MMCR Operating       36            Constant        |
|                    Computer                                           |
|                                                                       |
|   Coded Pulse Loss Calibration Files    36            Constant        |
|                                                                       |
|  ---------------- -------------------- ------------- ---------------- |
+-----------------------------------------------------------------------+

### Procedures

This information is currently unavailable.

### History

Antenna calibration information from the manufacturer:

[]{#__RefHeading___Toc501422281 .anchor}Table 9. MMCR Antenna Table

  --------------- ------------ ---------- ------------------ --------- -----------
  ** Diameter**   **Serial     **Model    **Location**       **Gain    **Beam
                  Number**     \#**                          (dBi)**   Width**

  2m              11           63208400   ARCS-1,            53.37     0.32˚
                                          Albuquerque                  

  2m              12           63208400   SHEBA              53.48     0.30˚

  2m              13           63208400   ARCS-2, Nauru      52.73     0.31˚

  2m              14           63208400   Barrow, AK         53.37     0.31˚

  3m              11           63208300   SGP                57.48     0.19˚
  --------------- ------------ ---------- ------------------ --------- -----------

## Operation and Maintenance

### User Manual

This information is currently unavailable.

### Routine and Corrective Maintenance Documentation

[SGP Preventative Maintenance
Procedures](http://198.124.96.210/pm_proc/mmcrpm03.htm) can be accessed
at this address:

<http://198.124.96.210/pm_proc/mmcrpm03.htm>.

[Preventive Maintenance
Logs](http://198.124.96.210:591/cfdpm1/default.htm) for SGP site
instruments are available here:
<http://198.124.96.210:591/cfdpm1/default.htm>. Just click on the
instrument desired then enter the date(s) of interest.

[Corrective Maintenance
Logs](http://198.124.96.210/menus/cmreports.html) for SGP site
instruments are available here:

<http://198.124.96.210/menus/cmreports.html>. Select the current fiscal
year or historical period to access the maintenance database.

### Software Documentation

Raw MMCR data are ingested at the Data Management Facility (DMF),
creating netCDF a1 level data files, which are stored at the ARM
Archive. Information on data file formats is available in Section 5,
Data Description and Examples..

### Additional Documentation

## Glossary

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

## Acronyms

AAO: Adjacent Arctic Ocean

ACRF: ARM Climate Research Facility

AGL: above ground level

ARCS: Atmospheric Radiation and Cloud Station

ARM: Atmospheric Radiation Measurement (Program)

CUDC: Coherent Up/Down Converter

DMF: Data Management Facility

DOE: U.S. Department of Energy

DQO: Data Quality Office

ETL: (NOAA) Environment Technology Laboratory

IF: Intermediate Frequency

Lidar: Light Detection and Ranging

MMCR: Millimeter wave Cloud Radar

MMW: Millimeter wave (30GHz - 300GHz)

MPL: Micropulse LIDAR

NOAA: National Oceanic and Atmospheric Administration

NSA: North Slope of Alaska

PNNL: Pacific Northwest National Laboratory (Battelle)

QME: Quality Measurement Experiment

RF: Radio Frequency

SDS: Site Data System

SGP: Southern Great Plains

SHEBA: Surface Heat Budget of the Arctic Ocean

TWP: Tropical Western Pacific

TWTA: Traveling Wave Tube Amplifier

VAP: Value-Added Product

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

## Citable References

Albrecht BA, TP Ackerman, G Mace, DW Thomson, MA Miller, and RM Peters.
1991. "A surface-based cloud observing system." Preprint Vol., *Seventh
Conf. on Meteorological Observations and Instrumentation*, pp. 443-446,
New Orleans.

Baum BA, T Uttal, M Poellot, TP Ackerman, JM Alvarez, J Intrieri, D
O\'C. Starr, J Titlow, V Tovinkere, and EE Clothiaux. 1995. "Satellite
remote sensing of multiple cloud layers." *J. Atmos. Sci,*
**52**:4210-4230.

Bogush, A. 1989. *Radar and the Atmosphere*, Artech House.

Clothiaux EE, MA Miller, BA Albrecht, TA Ackerman, J Verlinde, DM Babb,
RMPeters, and WJ Syrett. 1995. "An evaluation of a 94-GHz radar for
remote sensing of cloud properties." *J. Atmos.Ocean.Tech.*
**12**:201-229.

Currie N and C Brown. 1987. *Principles and Applications of
Millimeter-Wave Radar*, Artech House.

Dong X, TP Ackerman, EE Clothiaux, P Pilewskie, and Y Han. 1997.
"Microphysical and radiative properties of boundary layer stratiform
clouds deduced from ground-based measurements." *Journal Geophys. Res*.
**102**:23829-23843.

Doviak RJ, and DS Zrni. 1993. "Doppler Radar and Weather Observations."
2 ed., Academic Press, p. 562.

Frish AS, CW Fairall, and JB Snider. 1995. "Measurement of stratus cloud
and drizzle parameters in ASTEX with a Ka-band doppler radar and
microwave radiometer." *J. Atmos. Sci.* **52**:2788-2799.

Hobbs PV, NT Funk, RR Weiss, JD Locatelli, and KR Biswas. 1985.
"Evaluation of a 35- GHz radar for cloud physics research." *J. Atmos.
Oceanic Technol.* **2**:35-48.

Intrieri JM, GL Stephens, W Eberhard, and T Uttal. 1993. "A method for
determining cirrus cloud particle sizes using a lidar and radar
backscatter technique." *J. Appl. Meteor.* **32**:1074-1082.

Intrieri JM, WL. Eberhard, T Uttal, JA Shaw, JB Snider, Y Han, BW Orr,
and SY Matrosov. 1995. "Multiwavelength observations of a developing
cloud system: the FIRE II 26 November 1991 case study." *J. Atmos. Sci.*
**52**:4079-4094.

Kropfli RA and RD Kelly. 1996. "Meteorological research applications of
a mm-wave radar." *Meteorol. Atmos. Phys.* **59**:105-121.

Lhermitte RM 1987. "A 94-GHz doppler radar for cloud observations." *J.
Atmos. Oceanic. Tech.* **4**:36-48.

Lhermitte RM 1987. "Small cumuli observed with a 3-mm wavelength doppler
radar." *Geo. Research Letters* **14**:707-710.

Lhermitte RM 1988. "Cloud and precipitation remote sensing at 94 GHz."
*IEEE. Trans. Geo. Rem. Sen.* **26**:207-218.

Lhermitte RM 1990. "Attenuation and scattering of millimeter wavelength
radiation by clouds and precipitation." *J. Atmos. Oceanic. Tech.*
**7**:464-479.

Liebe HJ 1985. "An updated model for millimeter wave propagation in
moist air." *Radio Sci.* **20(**5):1069-1089.

Liebe HJ, T Manabe, and GA Hufford. 1989. "Millimeter-wave attenuation
and delay rates due to fog/cloud conditions." *IEEE Trans. Antennas
Propagation* **37(**12):1617-1623.

Liebe HJ. 1989. "MPM-An atmospheric milimeter-wave propagation model."
*Int. J. Infrared and Millimeter Wave*, **10(**6):631-650.

Mace GG, D O\'C. Starr, TP Ackerman, and P Minnis. 1995. "Examination of
coupling between an upper-tropospheric cloud system and synoptic-scale
dynamics diagnosed from wind profiler and radiosonde data," *Journal of
Atmospheric Sciences* **52**:4094-4127.

Martner BE and RA Kropfli. 1993. "Observations of multi-layered clouds
using Ka-band radar." *Proc. 31st Aerospace Sci. Mtg.*, AIAA, p. 8,
Washington, D.C.

Matrosov SY, T Uttal, JB Snider, and RA Kropfli. 1992. "Estimation of
ice cloud parameters from ground-based infrared radiometer and radar
measurements." *J. Geophys. Res.* **97**:11567-11574.

Matrosov SY 1993. "Possibilities of cirrus particle sizing from
dual-frequency radar measurements." *J. Geophys. Res.*, **98**,
20675-20683.

Matrosov SY, AJ Heymsfield, JM Intrieri, BW Orr, and JB Snider. 1995.
"Ground-based remote sensing of cloud particle sizes during the 26
November 1991 FIRE II cirrus case: comparisons with in situ data." *J.
Atmos. Sci.* **52**:4128-4142.

Mead JB, RE McIntosh, D Vandemark, and CT Swift. 1989. "Remote sensing
of clouds and fog with a 1.4-mm radar." *J. Atmos. Oceanic Technol.*
**6**:1090-1097.

Miller MA, MP Jensen, and EE Clothiaux. 1998. "Diurnal variability in
the statocumulus transition region: a case study using 94 GHz radar."
*J. Atmos. Sci.*. 55:2294-2310.

Miller MA and BA Albrecht. 1995. "Surface-based observations of
cumulus-stratocumulus interaction during ASTEX." *J. Atmos. Sci.*
**52**:2809-2826.

Moran KP, BE Martner, DC Welsh, DA Merritt, MJ Post, and T Uttal. 1997.
" ARM\'s cloud-profiling radar.: *Proceedings of the 28th Conf. on Radar
Meteorology*, Austin, TX.

Pasqualucci F, BW Bartrum, RA Kropfli, and WR Moninger. 1983. :A
millimeter-wavelength dual-polarization doppler radar for cloud and
precipitation studies.: *J. Climate Appl. Metero.* **22**:758-765.

Peters RM, BA Albrecht, MA Miller, and JT Treaster. 1992. "Automated
cloud profiling with a 94 GHz radar." *Proceedings of the Eleventh
International Conference on Clouds and Precipitation*, Montreal, Quebec,
Canada. August 17-21, 1992.

Planck VG, D Atlas, and WH Paulsen. 1955. :The nature and detectability
of clouds and precipitation as determined by a 1.25 centimeter radar."
*J. Meteor.* **12**:358-378.

Post MJ, KP Moran, and B Martner. 1996. *Contractors for the Department
of Energy ARM Program Millimeter-Wave Radars*. Environmental Technology
Laboratory, ERL, NOAA.

Probert-Jones JR 1962. "The radar equation in meteorology". *Quart. J.
Roy. Met. Soc.* **88**:485- 495.

Saugageot H 1992. *Radar Meteorology*, Artech House.

Sekelsky SM, and RE McIntosh. 1996. "Cloud Observations with a
Polarimetric 33 GHz and 95 GHz Radar." *Meteorol. Atmos. Phys.*
**59**:123-140.

Skolnik M. 1990. *Radar Handbook*, Merril Skolnik, McGraw-Hill.

Uttal T, JM Intrieri, WL Eberhard, TP Ackerman, and EE Clothiaux. 1995.
"Cloud boundaries during FIRE II." *J. Atmos. Sci.* **52**:4276-4284.

Wexler R and D Atlas. 1959. "Precipitation generating cells." *J.
Meteor.*, **16**:327-332.