Enhanced VWP
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The Enhanced Velocity Azimuth Display Wind Profile (EVWP) function is designed to improve
the availability and accuracy of VWP wind estimates.
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General Description
The Velocity Azimuth Display (VAD) algorithm computes wind speed and direction for the
heights required by the VWP product. The VAD algorithm uses a slant range parameter
(default = 30 km) to guide the selection of the elevation angle for each required
height. For any particular height, the elevation angle that is closest to the slant
range is used to compute the wind.
The VAD wind estimate for each individual height is based on the data
from a single elevation/range pair. This assumes that adequate return
is available using the single elevation/slant range pair to calculate
a representative wind estimate for the particular height. Several cases
have demonstrated that, in many meteorological situations, the assumption
that adequate valid return exists at a single range/elevation pair is not valid.
The Enhanced Velocity Azimuth Display Wind Profile (EVWP) function is designed to
improve the availability and accuracy of VWP wind estimates. The concept behind the
EVWP function is the fact that each VWP height is achieved at different slant ranges, depending
on the elevation. Therefore, in additional to the execution of the Original VAD, the EVWP
function generates multiple supplemental VAD wind estimates using different elevation/slant
range pairs for each required height. Then, the EVWP function selects the “best” wind
estimate for inclusion on the VWP product.
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More Detailed Information
In additional to the execution of the Original VAD algorithm, generate multiple
supplemental VAD wind estimates using different elevation/slant range pairs for
each height. For any elevation, slant ranges are limited to the interval between
10 and 20km. As each elevation is scanned, the EVWP function passes these
additional slant ranges to the VAD algorithm to process. The VAD algorithm
computes a wind estimate for each height (identified slant range) intersected
by the elevation scan. Each wind estimate is passed to the EVWP function for
validation. The following describes this process:
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Adaptable Parameters for EVWP
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The following are the adaptable parameters for EVWP. The LOCA for these
parameters has not been established.
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- enhanced_vad: Enables/disables EVWP logic (Yes/No, Default: Yes)
- min_points: Minimum number of points to conditionally accept VAD (Range [0, 100], Default: 25)
- min_symmetry: Minimum symmetry to conditionally accept VAD (Range [-10.0, 10.0], Default: -6.0)
- scale_rms: RMS scaling factor to conditionally accept VAD (Range [1.0, 5.0], Default: 2.0)
- min_proc_range: Minimum processing range for VAD (Range [5.0, 30.0], Default: 10.0)
- max_proc_range: Maximum processing range for VAS (Range [30.0, 120.0], Default 120.0)
Example Testing Results
KOHX_Feb_6_2008_Squal Line, shows the results of a long-period convective event from KOHX and was presented to the DQ Group on Feb 11, 2011. (PDF)
KLWX_May11_12_2006_Convective_Event, shows the results of a long-period severe convective event from KLWX. (PDF)
KGWX_May_2-3_2008_VWP-EVWP_Comparison, shows the results of a long-period convective event from KGWX. (PDF)
