MADIS Hydrological Surface Quality Control
This page provides a detailed description of the quality control (QC) processing and data structures for the hydrological surface dataset. For a general overview of MADIS quality control, click here.
Automated Quality Control
At this time, only level 1 QC checks are applied to hydrological surface
variables. The following table lists the variables that are QC'ed, and the
checks that are used:
MADIS Hydro Variables with QC
--------------------------------------------------------------
Code Name Max Level | Level 1:
Possible |
QC Level | Validity
|
--------------------------------------------------------------
PCP5M accumulated precip - 5m 1 X
PCP1H accumulated precip - 1h 1 X
PCP3H accumulated precip - 3h 1 X
PCP6H accumulated precip - 6h 1 X
PCP12H accumulated precip - 12h 1 X
PCP24H accumulated precip - 24h 1 X
The level 1 validity checks restrict each observation to falling within a TSP-specified set of tolerance limits. Observations not falling within the limits are flagged as failing the check. The following table lists the tolerance limits:
----------------------------------------- Validity Checks ----------------------------------------- Accumulated precip - [all] 0 - 44 in
Subjective Intervention
Two text files, a "reject" and an "accept" list provide the capability to subjectively override the results of the automated QC checks. The reject list is a list of stations and associated input observations that will be labeled as bad, regardless of the outcome of the QC checks; the accept list is the corresponding list of stations that will be labeled as good, regardless of the outcome of the QC checks.
Here are the current subjective intervention lists in use:
QC Data Structures
The MADIS QC information available for each variable includes the following QC structures: a single-character "data descriptor", intended to define an overall opinion of the quality of each observation by combining the information from the various QC checks, and for users desiring detailed information, a "QC applied" bitmap indicating which QC checks were applied to each observation, and a "QC results" bitmap indicating the results of the various QC checks.
The following table provides a complete list of the data descriptors and the bits used in the bitmaps:
----------------------------
MADIS QC Information - Hydro
----------------------------
QC Data Descriptor Values
-------------------------
No QC available:
Z - Preliminary, no QC
Automated QC checks:
C - Coarse pass, passed level 1
S - Screened, passed levels 1 and 2
V - Verified, passed levels 1, 2, and 3
X - Rejected/erroneous, failed level 1
Q - Questioned, passed level 1, failed 2 or 3
where level 1 = validity
level 2 = N/A
level 3 = N/A
Subjective intervention:
G - Subjective good
B - Subjective bad
Bitmask for QC Applied and QC Results
-------------------------------------
Bit QC Check Decimal Value
--- -------- -------------
1 Master Check 1
2 Validity Check 2
3 Reserved 4
4 Reserved 8
5 Reserved 16
6 Reserved 32
7 Reserved 64
8 Reserved 128
9 Reserved 256
10 Reserved 512
The QC bitmask is used in the QC applied and QC result "words" returned along with the QC data descriptor. By examining the individual bits, the user can determine which checks were actually applied, and the pass/fail status of each check that was applied.
In the QC applied word, a bit value of 1 means the corresponding check was applied, a bit value of 0 indicates the check wasn't applied.
In the QC results word, a bit value of 1 means the corresponding check was applied and failed, a bit value of 0 indicates the check passed (given that the check was applied).
The "Master Check" is used to summarize all of the checks in a single bit. If any check at all was applied, this bit will be set in the QC applied word. If the observation failed any QC check, it will be set in the QC results word.
When read as decimal numbers, the different bits that are set in the bitmask are summed together. For example, a QC applied value of 3 should be interpreted as 1 + 2, meaning the validity check was applied (and the "master check" as well).
References
Technique Specification Package 88-21-R2 For AWIPS-90 RFP Appendix G Requirements Numbers: Quality Control Incoming Data, 1994. AWIPS Document Number TSP-032-1992R2, NOAA, National Weather Service, Office of Systems Development.
Last updated 16 June 2016
