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 h_{min} and h_{max}) 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, QI_{source},
- how large fraction of investigated heights (between h_{min} and h_{max}) was scanned, QI_{scope},
and the final quality index QI is taken as a product of the both factors:
The value of the first component QI_{source} is taken as the quality of the measurement defining MAX. If MAX = “nodata” then QI_{source} = “nodata”, and if MAX = “undetect” then QI_{source} = 1.
Fig. 2. Quality characterization for maximum of reflectivity product in terms of availability.
The second component QI_{scope} is determined based on heights of the highest and lowest scans for considered Cartesian pixel (h_{highest} and h_{lowest} respectively) in relation to h_{min} and h_{max} (Fig. 2):
- if h_{highest} < h_{min} then
QI_{scope} = “nodata” and QI = “nodata”.
- if h_{highest} ≥ h_{min} and h_{lowest} <= h_{max} then QI_{scope} depends on what part of height range between h_{min} and h_{max} was scanned:
- if h_{lowest} > h_{max} then
QI_{scope} = “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
Attachments
- Fig_1_MAX.gif (3.1 KB) - added by jan 6 years ago.
- Fig_2_MAX.gif (12.8 KB) - added by jan 6 years ago.