**Concept of Operations**

**and**

**Operational Requirements**

**WSR-88D Dual Polarization**

Approved: Date:

Director, Office of Climate, Water

and Weather Services.

**2.2.1 INTRODUCTION**

Reference: SON-04-004 Additional Radar Observational Data

SON-05-023 WSR-88D Dual Polarization

This document describes the operational concept for National Weather
Service (NWS) usage of data from Weather Surveillance Radar -- 1988
Doppler (WSR-88D) units upgraded to Dual Polarization capability.

**2.2.2 CURRENT STATE OF OPERATIONS**

This section provides a description of the existing WSR-88D system. It
includes high-level descriptions of the functional and technical aspects
of the existing WFO radar usage environment.

**2.2.2.1 Background**

The NWS uses WSR-88D data as a primary source of information to support
tornado, other severe weather warnings, flash flood warnings and general
forecasts. The Environmental Modeling Center has begun using WSR-88D
wind information in model initialization, and intends to expand such
use. There are 143 WSR-88D units in the conterminous United States
(CONUS), 121 operated by the NWS and 22 operated by the Department of
Defense (DOD). Twelve additional WSR-88D units are operated by the FAA
in Alaska, Hawaii and Puerto Rico and support NWS Weather Forecast
Offices (WFOs) in those areas. The DOD operates four units outside the
CONUS, including one unit that supports WFO Guam.

A given WFO in the CONUS has a dedicated, high speed connection between
the Advanced Weather Interactive Processing System (AWIPS) and the local
NWS WSR-88D unit for effectively unlimited product access. All WFOs have
request/reply access to other WSR-88D units in the County Warning Area
(CWA). Recently, the request/reply functionality has been transformed
from low speed dial-up telephone lines to using the AWIPS Wide Area
Network (WAN) to improve the number and timeliness of products that can
be requested. Certain WFOs have dedicated high speed communication
connections to selected DOD WSR-88D units in their CWA.

WFOs also receive products from other WSR-88D units over the AWIPS
Satellite Broadcast Network (SBN). The SBN products are a subset of the
products routinely collected from each NWS WSR-88D unit with the Radar
Product Central Collection Distribution Service (RPCCDS).

In addition to viewing individual radar products, the forecaster can
view a mosaic of any product accumulated in the AWIPS database for the
local and up to eight surrounding WSR-88D units. All of the AWIPS
Display 2 Dimensional (D2D) functionality is available for viewing
individual and mosaic WSR-88D products.

While the WSR-88D data have been highly beneficial, there are
significant limitations to the effectiveness of WSR-88D support to NWS
forecast and severe weather warning operations. As described in the
WSR-88D Dual Polarization SON, these limitations affect rainfall
estimation, hail detection, winter weather services, and the quality of
basic reflectivity and velocity estimations. Many of these limitations
are related to the single polarization (linear horizontal) design of the
WSR-88D. This polarization provides information related mainly to the
horizontal scattering characteristics of scatterers, with little
information on the differences among snow flakes, hail stones,
raindrops, birds, etc., other than reflectivity strength.

![](media/image1.png){width="6.502083333333333in" height="2.6125in"}

Figure 1. Scatter plots of radar rainfall estimation vs gages for
polarimetric data (left) and reflectivity only (right).

**2.2.2.2 User Classes and Other Involved Personnel**

-   *NWS WFO and National Center Forecasters:* use radar information to
    support forecasts, watches and warnings

-   *NWS Hydrologists:* use radar information to support flood and river
    stage forecasts

-   *NWS Numerical Model Developers:* use radar information to improve
    model initialization, especially for high resolution models

-   *NWS Scientists and Engineers:* maintain and enhance technology and
    science of radar systems

-   *Administrators and Product Software Engineers:* manage and program
    operational baseline of software infrastructure and applications

-   *DOD and FAA Operational Personnel:* use radar information to
    support military and aviation missions

-   *Private Sector Meteorologists:* use radar information to support
    commercial sector weather enterprises

    **2.2.2.3 Organizational Structure**

The WSR-88D operations are part of the NWS NEXRAD Program, located
within the Office of Operational Systems (OOS). All operations and
maintenance support requirements for the WSR-88D are managed and funded
within OOS through the Radar Operations Center (ROC). Large, new
technology acquisitions and scientific evolution are managed and funded
within the NWS Office of Science and Technology (OST) through the NEXRAD
Product Improvement (NPI) program. Upon completion of NPI acquisition
projects, the ROC assumes operations and maintenance responsibilities
for the upgraded WSR-88D system. At this time, OOS and the ROC will also
assume life cycle integration and deployment responsibility.

**2.2.2.4 Support Environment**

NEXRAD is a tri-agency program of the NWS, DOD and FAA. The NWS acts as
the agent for the other two agencies. The ROC, the NWS Training Center,
and the NWS National Logistics Supply Center, all part of OOS, support
NEXRAD operations. The overall operational requirements are 24x7
operations with \>= 96% operational availability.

AWIPS provides the NWS with product display and manipulation
functionality for WSR-88D products. AWIPS operations and maintenance
support are funded through the NWS AWIPS Program. The Office of Climate,
Water and Weather Systems (OCWWS) Warning Decision Training Branch
(WDTB) develops forecaster training material for each AWIPS software
release, including material on new WSR-88D products and modifications to
WSR-88D operation.

**2.2.3 PROPOSED CONCEPT OF OPERATIONS**

This section provides a high level description of the objectives of the
Dual Polarization upgrade to the WSR-88D, and how the it will operate
from a user's perspective. It includes descriptions of user roles,
capabilities, functions and any required special features.

**2.2.3.1 Description of Polarimetric Information**

The addition of a linear vertical polarization channel (i.e., Dual
Polarization) will provide information related to both the horizontal
and vertical scattering characteristics of scatterers. Many years of
Dual Polarization R&D have identified Dual Polarization scattering
characteristics that can be used to distinguish among the various
precipitation and non-precipitation scatterers, and provide improved
information on rainfall rates, types of hydrometeors, and biological
versus meteorological scatterers. The additional information is
presented in the form of measured polarimetric moments and derived
quantity:

-   *Measured Polarimetric Moments*

    -   *Differential Reflectivity (Z~DR~):*

> This is a measure of the ratio of the back-scattered linear horizontal
> power to the back-scattered linear vertical power, which in dB of
> reflectivity is horizontal reflectivity (backscattered power) minus
> vertical reflectivity (backscattered power). If the volume of interest
> contains mostly small raindrops, there is little oblateness of the
> scatterers, and the reflectivities are close to each other, yielding a
> Z~DR~ near zero. However, as the raindrops increase in size, there is
> larger power received in the horizontal channel, and Z~DR~\>0. When
> there is a thunderstorm containing hail and rain, the hail stones
> tumble as they fall, yielding a mean vertical to horizontal ratio of
> near zero; hence the Z~DR~ for hail will be close to zero, while that
> of the heavy raindrops will be in the range from 1 to 5. Thus, Z~DR~
> is a useful measure to separate hail from rain. Using similar
> reasoning, Z~DR~ can be used to infer the presence of frozen
> precipitation, super-cooled water drops in updrafts, and the onset of
> melting snow/hail in the bright band region or near the ground.

-   *Correlation Coefficient (RHO):*

> This is a measure of the correlation between the horizontal and
> vertical back-scattered power (for all pulses used to observe a radar
> sample volume) from the scatterers within a given volume. If the
> entire volume is full of similarly sized small rain drops (compared to
> the wavelength of the radar), the correlation will be very high, from
> 0.95 to 0.99. When there is a mixture of particles, the correlation
> drops. If there is hail or snow mixed with rain, or a wide
> distribution of orientation of the hydrometeors, or tumbling wet snow
> aggregates and hail, the correlation will be much less than one, with
> values sometimes below 0.90. A good indicator of large hail is to have
> reduced correlation within areas of high reflectivity.

-   *Differential Phase Shift (PHI~DP~):*

> Differential Phase is simply the difference in phase between the
> horizontally- and vertically- polarized pulses at a given range along
> the propagation path. To understand Differential Phase, consider two
> simultaneous, or consecutive, radar pulses that travel the same
> propagation path. The first pulse is horizontally-polarized, and the
> second is vertically-polarized. Along the propagation path is a
> uniform field of falling raindrops. Falling raindrops are oblate, so
> the electric field will encounter more water content in the horizontal
> direction than in the vertical. The horizontally polarized pulse will,
> therefore, be affected by more water than the vertically polarized
> pulse. Since electromagnetic waves travel more slowly through water
> than through air, the horizontally-polarized wave will travel more
> slowly through the field of raindrops than will the
> vertically-polarized pulse. This is a two-way process: the
> horizontally-polarized backscattered radiation will travel more slowly
> back to the radar than the vertically-polarized backscatter. Since
> Differential Phase will increase with range from the radar, its range
> derivative is taken to determine where along the propagation path
> changes in phase difference are occurring. This derivative is called
> the S*pecific Differential Phase*, or K~DP~.

-   *Derived Polarimetric Quantity*

    -   *Specific Differential Phase (K~DP~):*

> Specific differential phase, K~DP~, is a range derivative of the
> differential phase shift and can be a good indicator of liquid water
> and rain rate along the propagation path, as the amount of the phase
> shift is directly related to the total liquid water through the path
> of the radar beam. Because this shift is only caused by liquid, this
> parameter can be used to make an estimate of rain in a hail-rain
> mixture. When raindrops are small and more spherical, this measure is
> not as useful as in the case of larger, more oblate raindrops found in
> more intense rain situations. A major positive factor with the use of
> the differential phase data is that, given intense enough returns,
> K~DP~ is independent of the absolute radar calibration, is immune to
> propagation effects on calibration, and to any noise inherent in the
> system. And as previously stated, in a rain/hail mixture, a good
> estimate of rainfall can be obtained.

-   *RPG Products*

    -   *Quantitative Precipitation Estimation Algorithm (QPE)*

> The initial deployment of Dual Polarization will include a new
> rainfall estimation algorithm based on a combination of the
> polarimetric parameters K~DP~ and Z~DR,~ and the current linear
> horizontal reflectivity parameter Z. This algorithm utilizes the
> strengths of polarimetric parameters in heavier rainfall rates, and
> the value of Z in lighter rates. At this time, it has not been
> determined whether to provide the polarimetric rainfall estimate in
> addition to, or as a replacement of, the current algorithm.

-   *Hydrometeor Classification Algorithm (HCA)*

> The initial deployment of Dual Polarization will include a hydrometeor
> classification algorithm. The algorithm will generate products showing
> where hail, rain, snow, biological scatterers, and clutter are
> identified.

**2.2.3.2 Operations from a User's Perspective**

Dual Polarization will be implemented within the existing framework of
WSR-88D operations, as described in Section 2.2.2. Users will see
additional base products (Z~DR~, PHI~DP~, RHO, K~DP~) and derived
products (polarimetric precipitation estimates, HCA). These products
will comply with current Radar Product Generator (RPG) Interface Control
Document (ICD) formats, and thus may be requested, viewed and
manipulated with all of the normal capabilities of AWIPS D2D for radar
products.

Dual Polarization information will be valuable for all seasons and for
all WFO and RFC forecast and warning missions where radar data are
normally used. It is anticipated that forecasters will absorb the new
products into their normal forecast and warning preparation processes.
It is further anticipated that the polarimetric precipitation
information will be incorporated into the WFO Flash Flood Monitoring and
Prediction (FFMP) system, the WFO and RFC Multi-parameter Precipitation
Estimation (MPE) software and RFC hydrologic models.

**2.2.4 OPERATIONAL SCENARIOS**

This section presents examples of Dual Polarization products, with a
focus on their operational use.

**2.2.4.1 Heavy Precipitation**

Precipitation, with high reflectivities covering a large area, is in
progress. The current WSR-88D precipitation estimates are too high due
to use of an inappropriate Z/R relationship for the drop size
distribution prevailing in this event. The Dual Polarization
precipitation estimates, utilizing KDP and ZDR, are much closer to rain
gage reports. The forecaster, with more accurate rainfall estimates,
determines that no flash flood warning is required, and avoids issuing a
false alarm.

Figures 2 and 3 show the improved rainfall estimates using Dual
Polarization data versus the current WSR-88D.

![](media/image2.png){width="6.5in" height="3.7472222222222222in"}

Figure 2. General overestimation of rainfall estimates using current
WSR-88D capability.

![](media/image3.png){width="6.5in" height="3.7694444444444444in"}

Figure 3. General good agreement of Dual Polarization rainfall estimates
with rain gage reports (overlaid numerical values).

The improvements in rainfall estimation with polarimetric data have been
quantified by NSSL, as shown in the scatter plots in Figure 1. These
scatter plots represent data from 150 gages and 50 hours of observations
over 24 rain events.

**2.2.4.2 Winter Freezing Rain Event**

A large area of winter precipitation is in progress. The current WSR-88D
reflectivity data do not differentiate between areas of snow, rain, or
AP. The Dual Polarization Hydrometeor Classification Algorithm suggests
areas of snow aloft, stratiform rain at lower altitudes, and
non-meteorological AP close to the radar. The forecaster develops
further confidence and understanding of the precipitation type by
utilizing the Dual Polarization base data variables, Differential
Reflectivity (Zdr) and Correlation Coefficient (RHO), along with surface
temperatures. Zdr and RHO both dramatically increase where liquid
precipitation is falling. The Dual Polarization indication of rain
versus snow, allows the forecaster to alert the public with a high
degree of confidence on the freezing rain conditions in the metropolitan
Oklahoma City area.

![](media/image4.png){width="2.999212598425197in"
height="2.7956692913385828in"}![](media/image5.jpeg){width="3.2318897637795274in"
height="2.9173228346456694in"}

**Figure 4. Current linear horizontal reflectivity \[left: dBZ\] versus
Dual Polarization Winter Hydrometeor Classification Product \[right:
areas of snow (DS-Dry Snow, WS-Wet Snow) and rain (SR-Stratiform
Rain)\]. The surface temperatures have been added to the Dual
Polarization radar product.**

**2.2.4.3 Hail Event**

A convective storm is in progress. The current WSR-88D reflectivity data
indicate an area of high reflectivity, but the spatial extent, quantity,
and size of hail is ambiguous. The Dual Polarization Convective
Hydrometeor Classification Algorithm identifies a more concise area of
threat for hail, which is further evaluated through reviewing the dual
polarization base data. Large hail usually has near zero or negative
Zdr, RHO below .95, and nearly 0 KDP. The forecaster is able to use this
information to better organize storm spotters on this storm, and the
forecaster is able to warn the public with more spatial precision and
confidence.

![](media/image6.png){width="6.501388888888889in"
height="3.6354166666666665in"}

![](media/image7.png){width="6.499305555555556in"
height="3.6416666666666666in"}

**Figure 5. (Top). Current reflectivity product with overlay of hail
likelihood based on algorithm. (Bottom) Dual Polarization Convective
Hydrometeor Classification Product showing identified area of hail**

2.2.4.4 Base Products

In current NWS operations, base data analysis is the foundation of storm
interrogation that is used to make warning decisions. Algorithms are
used to raise situation awareness, and they act as a safety net. Base
data analysis is critical for the development of expertise in
forecasters because it leverages the human strength of pattern matching,
and it allows the forecaster to develop a fundamental understanding of
storm structure. Base Product displays for the polarimetric moments
provide the same critical role in operations, and they provide for the
integration of precipitation micro-physics into warning decision making.
The following figure illustrates the strong hail signal in the
Reflectivity, Differential Reflectivity, and Correlation Coefficient
base products and the derived Specific Differential Phase polar display
product. The base data show:

1.  high values of horizontal reflectivity (potentially rain or hail)
    coincident with:

2.  low-values of Differential Reflectivity (spherically-oriented
    tumbling hail hydrometeors and/or small rain drops),

3.  low values of Specific Differential Phase (no rain, therefore likely
    just hail),

4.  very low Correlation Coefficient (Mie scattering strongly suggesting
    large hail).

The base data analysis provides for a high degree of confidence of the
presence of large hail, and it gives the forecaster an understanding of
the hail growth mechanism (dry hail growth with weak competition for
cloud drops). This information allows for more strongly worded severe
weather statements that accurately describe the high level of threat for
large hail with more confidence and spatial accuracy.

![](media/image8.png){width="5.992361111111111in"
height="3.3444444444444446in"}

Figure 6. Supercell thunderstorm producing softball-size hail.

2.2.5 SUMMARY OF IMPACTS

This section provides a description of the anticipated operational,
technical, and organizational impacts associated with the Dual
Polarization upgrade. It includes a description of the impacts
anticipated during the transition period.

**2.2.5.1 Operational Impacts**

-   More radar data to analyze during severe weather events.

    -   Interpretation challenges associated with new radar parameters,
        and, potentially, retaining legacy rainfall accumulation product
        along with polarimetric version.

    -   More AWIPS WAN traffic, with the potential need for more
        prioritization of WAN messages to ensure throughput of
        operationally critical information.

-   Additional staff time requirement for recurring local training of
    forecasters.

    -   Forecaster training material on Dual Polarization data usage
        will be developed by the WDTB to be included in:

        -   ORPG and ORDA Build training packages

        -   the AWIPS training package,

        -   updates to the WDTB Distance Learning Operations Course
            (DLOC) for interns

        -   updates to the WDTB Advanced Warning Operations Course
            (AWOC). and

        -   training for NWS dissemination partners (e.g. media) who
            have access to the data if the data is available in real
            time.

.

**2.2.5.2 Organizational Impacts**

-   Potential for future increase in capacity requirements for:

    -   AWIPS database and processing (additional WSR-88D products, both
        base and derived)

    -   Radar Products Central Collection Dissemination Service (RPCCDS)
        (additional WSR-88D products)

    -   Level II central collection (additional moments for polarimetric
        data)

    -   National Climatic Data Center archive (additional products and
        Level II data)

-   Additional O&M maintenance training for Dual Polarization components

    **2.2.5.3 NWS Science and Technology Infusion**

```{=html}
<!-- -->
```
-   Prioritization of development resources to address both legacy
    WSR-88D applications and new polarimetric applications.

    **2.2.5.4 Impacts during Implementation**

```{=html}
<!-- -->
```
-   Prioritization of development and testing resources between NWS OST,
    NWS OHD, Forecast Systems Laboratory (AWIPS modifications for
    additional products), and ROC.

**2.2.6 ALTERNATIVES ANALYSIS**

Dual Polarization will provide fundamental observational data to improve
many of the NWS warning and forecast services. There are no technical
alternatives that are applicable for providing such data. The
limitations of the current WSR-88D data, detailed in Section 2.2.2.1,
cannot be addressed through training, policy, procedures, etc.

**2.2.7 REQUIREMENTS DEVELOPMENT**

Dual Polarization operational requirements were developed to address
known issues with WSR-88D data and products in the areas of rainfall
estimation, rain-snow discrimination, hail identification and data
contamination by clutter and birds. These issues have been identified
through WFO and RFC operational experience with the WSR-88D since its
deployment in the mid-1990s.

**2.2.8 OPERATIONAL REQUIREMENTS**

This section identifies the high-level functional and operating
capabilities and characteristics of the Dual Polarization upgraded
WSR-88D from the user's perspective. The requirements are stated in
Table 1, Operational Requirements. Not all the categories listed in the
table may apply. Each requirement is assigned a unique Identification
Number. Each requirement is a concise stand-alone statement and includes
an owner (identifies who needs the specific requirement), priority, and
verification method.

The Requirements Owner is the office, user class/group or service area
stating the need for the requirement. Each of the requirements is
assigned one of the following **Priority Level**:

-   **High**: The requirement has the highest priority classification in
    the proposed systems. It is essential and must be met.

-   **Medium**: The requirement is important. Not meeting this
    requirement would result in a significantly degraded (but still
    useable) capability.

-   **Low**: If this requirement is not met, some capability or ease of
    use would be degraded or slightly degraded

Each requirement is assigned a Verification Method which indicates how
the requirement will be verified, and include:

-   **Test**: The requirement will be verified with testing.

-   **Demo**: The requirement will be verified by demonstration.

-   **Inspect**: The requirement will be verified by inspection.

-   **None**: Verification is not required.

The Dual Polarization upgrade to the WSR-88D is a modification to the
existing components of the WSR-88D. As such, Dual Polarization will meet
the operational requirements of the current WSR-88D System Specification
(Radar Operations Center Document Number 2810000E), and will operate
within the current WSR-88D training, operations, and
maintenance/logistics support policies, procedures and structures.

**Table 1. OPERATIONAL REQUIREMENTS**

+------------+---------------------------+-------+-------+-----------+
| IDEN       | **OPERATIONAL**           | OWNER | PRI   | VER       |
| TIFICATION |                           |       | ORITY | IFICATION |
|            | **REQUIREMENT**           |       |       | METHOD    |
| NUMBER     |                           |       | LEVEL |           |
+============+===========================+=======+=======+===========+
| **1.0**    | **Operational**           |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **1.1**    | **The Dual Polarization   | W/OS  | High  | Demo      |
|            | upgraded WSR-88D shall be |       |       |           |
|            | able to operate in Dual   |       |       |           |
|            | Polarization mode         |       |       |           |
|            | continuously.**           |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **1.2**    | **Dual Polarization base  | W/OS  | High  | Test      |
|            | data shall be provided in |       |       |           |
|            | the maximum spatial       |       |       |           |
|            | resolution supported by   |       |       |           |
|            | the WSR-88D and           |       |       |           |
|            | scientific research,      |       |       |           |
|            | currently established as  |       |       |           |
|            | 250 m and 0.5 deg.**      |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **1.3**    | **Dual Polarization base  | W/OS  | High  | Test      |
|            | data shall be provided to |       |       |           |
|            | the maximum range of      |       |       |           |
|            | operational utility,      |       |       |           |
|            | currently established as  |       |       |           |
|            | 300 km.**                 |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **1.4**    | **The Dual Polarization   | W/OS  | High  | Demo      |
|            | upgraded WSR-88D shall    |       |       |           |
|            | meet the operational      |       |       |           |
|            | availability requirements |       |       |           |
|            | defined for the current   |       |       |           |
|            | WSR-88D.**                |       |       |           |
+------------+---------------------------+-------+-------+-----------+
|            |                           |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **2.0**    | **Functional**            |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **2.1**    | **The Dual Polarization   | W/OPS | High  | Test      |
|            | upgraded WSR-88D shall    |       |       |           |
|            | meet the functional       |       |       |           |
|            | requirements defined for  |       |       |           |
|            | the current WSR-88D.**    |       |       |           |
+------------+---------------------------+-------+-------+-----------+
|            |                           |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **3.0**    | **Data / Information**    |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **3.1**    | **Dual Polarization base  | W/OS  | High  | Test      |
|            | data products shall be    |       |       |           |
|            | provided for the moments: |       |       |           |
|            | Differential              |       |       |           |
|            | Reflectivity, Correlation |       |       |           |
|            | Coefficient, and          |       |       |           |
|            | Differential Phase.**     |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **3.2**    | **Dual Polarization       | W/OS  | High  | Demo      |
|            | derived quantities shall  |       |       |           |
|            | be provided for: Specific |       |       |           |
|            | Differential Phase,       |       |       |           |
|            | Rainfall Estimation, and  |       |       |           |
|            | Hydrometeor               |       |       |           |
|            | Classification.**         |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **3.3**    | **Dual Polarization base  | W/OS  | High  | Inspect   |
|            | data and products shall   |       |       |           |
|            | comply with Government    |       |       |           |
|            | Furnished Information     |       |       |           |
|            | (GFI).**                  |       |       |           |
+------------+---------------------------+-------+-------+-----------+
|            |                           |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **4.0**    | **Human Factors**         |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **4.1**    | **The Dual Polarization   | W/OS  | High  | Demo      |
|            | upgraded WSR-88D shall    |       |       |           |
|            | comply with the same      |       |       |           |
|            | Human Factors             |       |       |           |
|            | requirements defined for  |       |       |           |
|            | the current WSR-88D.**    |       |       |           |
+------------+---------------------------+-------+-------+-----------+
|            |                           |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **5.0**    | **System Level            |       |       |           |
|            | Interface**               |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **5.1**    | **The Dual Polarization   | W/OPS | High  | Test      |
|            | upgraded WSR-88D shall    |       |       |           |
|            | comply with the same      |       |       |           |
|            | system level interface    |       |       |           |
|            | requirements defined for  |       |       |           |
|            | the current WSR-88D.**    |       |       |           |
+------------+---------------------------+-------+-------+-----------+
|            |                           |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **6.0**    | **Operational             |       |       |           |
|            | Maintenance**             |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **6.1**    | **The Dual Polarization   | W/OPS | High  | Inspect   |
|            | upgraded WSR-88D shall    |       |       |           |
|            | comply with the same      |       |       |           |
|            | operational maintenance   |       |       |           |
|            | requirements defined for  |       |       |           |
|            | the current WSR-88D.**    |       |       |           |
+------------+---------------------------+-------+-------+-----------+
|            |                           |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **7.0**    | **Logistics**             |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **7.1**    | **The Dual Polarization   | W/OPS | High  | Inspect   |
|            | upgraded WSR-88D shall    |       |       |           |
|            | comply with the same      |       |       |           |
|            | logistics requirements    |       |       |           |
|            | defined for the current   |       |       |           |
|            | WSR-88D.**                |       |       |           |
+------------+---------------------------+-------+-------+-----------+
|            |                           |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **8.0**    | **Security and Privacy**  |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **8.1**    | **The Dual Polarization   | W/OPS | High  | Inspect   |
|            | upgraded WSR-88D shall    |       |       |           |
|            | comply with the same      |       |       |           |
|            | security and privacy      |       |       |           |
|            | requirements defined for  |       |       |           |
|            | the current WSR-88D.**    |       |       |           |
+------------+---------------------------+-------+-------+-----------+
|            |                           |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **9.0**    | **Training**              | W/OPS | High  | Inspect   |
+------------+---------------------------+-------+-------+-----------+
|            |                           |       |       |           |
+------------+---------------------------+-------+-------+-----------+
|            |                           |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **10.0**   | **Documentation**         |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **10.1**   | **The Dual Polarization   | W/OPS | High  | Inspect   |
|            | upgraded WSR-88D shall    |       |       |           |
|            | comply with the same      |       |       |           |
|            | documentation             |       |       |           |
|            | requirements defined for  |       |       |           |
|            | the current WSR-88D.**    |       |       |           |
+------------+---------------------------+-------+-------+-----------+
|            |                           |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **11.0**   | **Constraints**           |       |       |           |
+------------+---------------------------+-------+-------+-----------+
|            |                           |       |       |           |
+------------+---------------------------+-------+-------+-----------+
|            |                           |       |       |           |
+------------+---------------------------+-------+-------+-----------+
| **12.0**   | **Other**                 |       |       |           |
+------------+---------------------------+-------+-------+-----------+
|            |                           |       |       |           |
+------------+---------------------------+-------+-------+-----------+

+-----------------------------------+-----------------------------------+
| **Priority Level** **Key**:       | **Verification Method key:**      |
+-----------------------------------+-----------------------------------+
| **High**: The requirement has the | **Test**: The requirement will be |
| highest priority classification   | verified with testing.            |
| in the proposed systems. It is    |                                   |
| essential and must be met.        | **Demo**: The requirement will be |
|                                   | verified by demonstration.        |
| **Medium**: The requirement is    |                                   |
| important. Not meeting this       | **Inspect**: The requirement will |
| requirement would result in a     | be verified by inspection.        |
| [significantly                    |                                   |
| degraded]{.underline} (but still  | **None**: None required.          |
| useable) capability.              |                                   |
|                                   |                                   |
| **Low**: If this requirement is   |                                   |
| not met, some capability or ease  |                                   |
| of use would be degraded or       |                                   |
| slightly degraded                 |                                   |
+-----------------------------------+-----------------------------------+