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Dip test - QC2d-1 - Revision 01

The above cartoon is just to illustrate the order of t0,t1 and t2. Note in email exchanges the same time labels have been described as t-2, t-1 and t. (Please let me know if there is a specific convention that you prefer to be adopted and this page will be updated ….ed).

The flag fs=2 is detected on the observation A(t2), the previous value A(t1) is also flagged fs=2, and the next previous value A(t0) is flagged fs=1.

 If  
    | A(t2) - A(t0) | < | A(t1) - A(t0) | 
 and 
    | A(t2) - A(t1) | > DELTA

where DELTA is dependent on the parameter

    
   set fs=9 on A(t1) 
   set fs=4 on A(t2)

A(t1) 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):

1 AA
2 BI
81 FF
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
212 TAM
213 TAN
215 TAX
221 TG
222 TGM
223 TGN
225 TGX
227 TJM
262 UU
264 UN
265 UX
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/diptest01.1295478983.txt.gz
  • Last modified: 2022-05-31 09:23:18
  • (external edit)