Dip test - QC2d-1 - Revision 02

CRITERIA:

(1) |A(t)-A(t-2)| < |A(t-1) - A(t-2)|

(2) |A(t)-A(t-1)|  > δ

(3) fs=2 for A(t-1)

(4) fs=1 for A(t-2)

where DELTA is dependent on the parameter

The above was tried out with mixed success … therefore rolled back to also requiring fs=2 for A(t) pending further specification

If the criteria are met

    
   set fs=9 for A(t-1) 
   set fs=4 for A(t)

A(t-1) receives a corrected value by interpolation. The interpolation method can be linear or by Akima algorithm.

Relevant parameters are all those subject to the step check (QC1-3a):

paramid parameter δ(X)
1 AA
2 BI
81 FF 10 or 12,5 m/s TBC
85 FM
86 FX
87 FX_1
88 FX_6
89 FX_12
90 FG_1
91 FG_6
92 FG_12
93 FX_X
94 FG_X
104 RA
105 RR_01
113 SS_1
123 RT_1
172 PH
174 POM
175 PON
176 POX
177 PP
197 QE
198 QL
199 QLX
200 QO
201 QOX
211 TA 7,5 °C TBC
212 TAM
213 TAN
215 TAX
221 TG
222 TGM
223 TGN
225 TGX
227 TJM
262 UU 30% TBC
264 UN
265 UX

It is possible that δ(X) can be derived from the station_param table, but the exact rule is TBD. Here is an extract of the station_param table for reference:

 stationid | paramid | level | sensor | fromday | today | hour |      qcx      |            metadata             |     desc_metadata     |      fromtime     
  
-----------+---------+-------+--------+---------+-------+------+---------------+---------------------------------+-----------------------+-------------------
--
     76920 |     211 |     0 | 0      |       1 |    31 |   -1 | QC1-1-211     | max;highest;high;low;lowest;min |                       | 1500-01-01 00:00:0
0
                                                                               : 50;15.3;10.3;-.5;-5.5;-55                                 
     76920 |     211 |     0 | 0      |      32 |    59 |   -1 | QC1-1-211     | max;highest;high;low;lowest;min |                       | 1500-01-01 00:00:0
0
                                                                               : 50;15.2;10.2;-.9;-5.9;-55                                 
     76920 |     211 |     0 | 0      |      60 |    90 |   -1 | QC1-1-211     | max;highest;high;low;lowest;min |                       | 1500-01-01 00:00:0
0
                                                                               : 50;14.7;9.7;1;-4;-55                                      
     76920 |     211 |     0 | 0      |      91 |   120 |   -1 | QC1-1-211     | max;highest;high;low;lowest;min |                       | 1500-01-01 00:00:0
0
Flag valueDefinitionuseinfo(2) consequence
fs=4Kontrollert. Mistanke om feil detektert i QC1-3. Ingen tilsvarende feil i QC2d-1. Ingen korreksjon.Friskmeldt.
fs=5Kontrollert. Ingen mistanke om feil detektert i QC1-3. Mistanke om feil detektert i QC2d-1.Ingen korreksjon.Originalverdi noe mistenkelig.
fs=9Kontrollert. Observert endring høyere enn testverdi. Korrigert automatisk.Originalverdi sikkert feilaktig.

The report 24/93 KLIMA “Theoretical analysis of the dip-test in quality control of geophysical observations” by Petter Øgland describes a diptest run independent from a previous step test.

http://klima.dnmi.no/rapporter/Klimarapporter/1993/24_93.pdf

Comparison between Øgland's parameter δ and the current Kvalobs step criterium shows:

 δ(UU) = 30%  versus the Kvalobs step(UU) = 30%
 δ(FF) = 30 m/s versus the Kvalobs step(FF) = 10 or 12.5 m/s
 δ(TA) = 10.5 °C versus the Kvalobs step(TA) = 7,5 °C

For wind and temperature the Kvalobs dip test will flag more often than by Øgland's formula. For humidity will Øgland's formula gives error flags without corresponding flag from the Kvalobs dip test. This occurs in a “skew” dip when the step test criterion is met in one of the two cases.

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  • kvalobs/kvoss/system/qc2/requirements/algorithms/diptest02.txt
  • Last modified: 2022-05-31 09:29:32
  • (external edit)