2. Configure the MLHGT product:
Variability
The MLHGT algorithm uses climatological melting level altitude as an initialization
parameter in the Bayesian inference.
The Variability field sets the realistic limits of allowed MLHGT solutions centered
at the climatological melting levels configured in Ingest/Setup utility.
For example, if the climatological melting level height is typically 3 km (1.9 mi)
above sea level and the variability is set at 3000 m (9842 ft 6 in), the accepted
range for the solution is from 1.5 ... 4.5 km (0.9 ... 2.8 mi).
You can still use the setup_change function to automatically update 0 °C
heights from other sources, such as radiosonde or NWP, on a more timely
basis.
Hgt Bin Spacing
An Earth co-ordinate grid system is created where a MLHGT value is derived for
each grid point. This field sets the vertical bin spacing centered on each grid
point.
Data in the vertical bins are used as input to the height determination. Allowable
inputs are between 50 ... 2000 m (164 ft 1 in ... 6561 ft 8 in).
Az bins
The spatial resolution varies as a function of range due to the broadening of the
radials. This field defines how many column sectors exist in the 360° of view. For
example, if you add a value of 24, there are 24 columns for each range interval,
each having a size of 15° (360/24 =15).
By specifying a small base scale of the grid, more MeltClassifier
estimates are needed as input to achieve a given confidence level.
Specifying a large grid scale lowers the overall resolution.
You may wish to achieve something in between, which provides sucient
data availability at the desired confidence levels with higher resolutions.
Decay Time
As confidence of the MLHGT estimates decreases, either by lack of radar
observations or latency in time, the MLHGT Bayesian approach smoothly
transitions the estimates from the radar observed height to the climatological
melting level height at every grid point.
The Decay Time field sets the length of the time window for this smooth
transition. The default value is 1 hour.
Min Confidence
At each grid point the MLHGT algorithm checks the confidence in the radar
MLHGT estimate by comparing it with those in the neighboring grids. The
confidence is accepted if it exceeds the minimum confidence level defined in this
filed AND a minimum number of neighbors meet the confidence. Else the
confidence in the estimate is set to a very low value.
Chapter 3 – Configuring IRIS Products
RESTRICTED 53
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