wiki:cookbook/Product2D_MAX
Last modified 4 years ago Last modified on 04/29/13 11:32:04

1. Algorithm name

Quality-based maximum of reflectivity (MAX) product generation – Product2D: MAX

2. Basic description

a) Physical basis of the algorithm

The algorithm generates maximum of reflectivity (MAX) 2-D product from radar reflectivity volume with quality information using product2D_PPI algorithm.

b) Amount of validation performed so far

Not performed yet.

c) References (names and contact information of all developers during the evolutionary history, scientific papers)

IMGW, Department of Ground Based Remote Sensing.

3. ODIM metadata requirements for I/O

Input data: VOL

  • General “what”: source(NOD).
  • For particular SCANs:
    • Dataset-specific “where” for data and QI: nbins, nrays.
    • Data-specific “what” for data: gain, offset, nodata, undetect.
    • Data-specific “what” for QI: gain, offset, nodata, undetect.

Output data: Cartesian data

  • Top-level “where”: lon, lat, xsize, ysize, xscale, yscale.
  • Dataset-specific “what”: product.
  • Data-specific “what” for data: gain, offset, nodata, undetect.
  • Data-specific “what” for QI: gain, offset, nodata, undetect.

4. Input data

a) What kind of radar data (including the list of previous algorithms and quality flags applied)

object=PVOL:

  • quantity=DBZH, otherwise TH,
  • quantity=QIND (generated e.g. by QI_TOTAL algorithm).

b) Other data (optional and mandatory, applying “universally” agreed formats, geometry)

Defined projection and domain of Cartesian output.

5. Logical steps, using any of: text, flow charts, graphics, equations (or references to equations), conditional branches in “all possible cases”.

The algorithm generates maximum of reflectivity (MAX) 2-D products in Cartesian coordinates from radar reflectivity volume and based on the data quality information.

Algorithm parameters

Set of the algorithm parameters:

Description Denotation Unit Default value
Lower height limit for MAX product generation MAX_hMin km 1
Upper height limit for MAX product generation MAX_hMax km 20

Algorithm description

Maximum of reflectivity (MAX) product represents Cartesian image of highest measured value of radar reflectivity Z (in dBZ) for each vertical column. The maximum is detected in a preset range of height (between hmin and hmax) and generally is a search for the highest value among reflectivities in pixels in the column for all PPIs (Fig. 1).

Fig. 1. Scheme of generation of maximum of radar reflectivity product (MAX).

Data quality characterization

Quality of the MAX depends on the two factors:

  • quality of reflectivity data taken as MAX, QIsource,
  • how large fraction of investigated heights (between hmin and hmax) was scanned, QIscope,

and the final quality index QI is taken as a product of the both factors:

$  QI = QI_{source} \cdot QI_{scope}  $

The value of the first component QIsource is taken as the quality of the measurement defining MAX. If MAX = “nodata” then QIsource = “nodata”, and if MAX = “undetect” then QIsource = 1.

Fig. 2. Quality characterization for maximum of reflectivity product in terms of availability.

The second component QIscope is determined based on heights of the highest and lowest scans for considered Cartesian pixel (hhighest and hlowest respectively) in relation to hmin and hmax (Fig. 2):

  • if hhighest < hmin then

QIscope = “nodata” and QI = “nodata”.

  • if hhighesthmin and hlowest <= hmax then QIscope depends on what part of height range between hmin and hmax was scanned: $  QI_{scope} = \frac {min(h_{highest},h_{lowest}) - max(h_{lowest},h_{min})} {h_{max} - h_{min}}  $
  • if hlowest > hmax then

QIscope = “nodata” and QI = “nodata”.

6. Output

a) Data type using ODIM notation where possible, e.g. DBZH

Input quantity as IMAGE object (in Cartesian coordinates) with:

  • "how": task - "pl.imgw.product2d.max",
  • "how": task_args
    • parameters inherited from PPI algorithm (interpolation method and selected quality field name),
    • parameters of MAX algorithm,

b) Quality index (QI) field

Quality index field QIND as IMAGE object with:

  • "how": task - "pl.imgw.product2d.max",
  • "how": task_args - parameters inherited from PPI algorithm (interpolation method and selected quality field name).

7. Outline of a test concept exemplifying the algorithm, as a suggestion for checking that an implementation has been successful.

TBD

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