Modified

27 October 2026

QCF: overall quality control flag

The overall quality flag QCF combines the test flags of the post-processing chain into one flag per record. It is calculated after each level, and each level includes the tests of the levels before it, so the flag after Level 3.3 accounts for all tests.

Notebook: 01_FPPC_IRGA72_NEE, the tables “result of each Level-2 test” and “result of each Level-3.2 test” and Step 5.

Flag values

Table 1: Values of the overall quality flag.
QCF Meaning Rule
0 Best quality No test raised a flag
1 Good quality One to three soft flags, no hard flag
2 Rejected At least one hard flag, or more than three soft flags

Each test flags a record 0 (passed), 1 (soft flag, a warning) or 2 (hard flag, rejected). Most tests set only hard flags. Soft flags come from the SSITC test (flag 1 as reported by EddyPro) and from the spectral correction factor test (SCF from 2 to below 4). A missing flux is rejected by the missing-value test, so it always has QCF 2.

In FP2026.1 the same rule applies by day and by night: records with QCF 0 and 1 are kept.

Columns

For a flux <flux> after level <level>, for example NEE_L3.1 after Level 3.3 in the scenario CUT_50:

Table 2: Columns of the overall quality flag, for NEE after Level 3.3 (CUT_50).
Column Content
FLAG_L3.3_CUT_50_NEE_L3.1_QCF The overall flag: 0, 1 or 2
NEE_L3.1_L3.3_CUT_50_QCF The flux where QCF is 0 or 1
NEE_L3.1_L3.3_CUT_50_QCF0 The flux where QCF is 0
SUM_L3.3_CUT_50_NEE_L3.1_SOFTFLAGS Sum of the soft flags, equal to their number
SUM_L3.3_CUT_50_NEE_L3.1_HARDFLAGS Sum of the hard flags, twice their number
SUM_L3.3_CUT_50_NEE_L3.1_FLAGS Sum of both

The same columns exist after each level: FLAG_L2_FC_QCF, FLAG_L3.1_NEE_QCF, FLAG_L3.2_NEE_L3.1_QCF and FLAG_L3.3_<CUT>_NEE_L3.1_QCF for NEE, and the same pattern for LE and H, whose Level-3.3 columns carry CUT_NONE.

Which columns to use

  • Gap-filled series: NEE_L3.1_L3.3_CUT_50_QCF_gfXG and its scenarios, LE_L3.1_L3.3_CUT_NONE_QCF_gfXG, H_L3.1_L3.3_CUT_NONE_QCF_gfXG (see Level 4.1). They are built from the records with QCF 0 and 1.
  • Measured values only: the _QCF columns (QCF 0 and 1), or the _QCF0 columns for the highest quality.

Records per flag

Table 3: Records per value of the overall quality flag in FP2026.1, out of 188,448 half-hours. QCF 2 includes the records without a measured flux.
Flag column QCF 0 QCF 1 QCF 2
FLAG_L2_FC_QCF 59,004 75,311 54,133
FLAG_L3.2_NEE_L3.1_QCF 56,966 66,893 64,589
FLAG_L3.3_CUT_16_NEE_L3.1_QCF 49,090 43,322 96,036
FLAG_L3.3_CUT_50_NEE_L3.1_QCF 46,827 39,930 101,691
FLAG_L3.3_CUT_84_NEE_L3.1_QCF 44,048 36,201 108,199
FLAG_L3.3_CUT_NONE_LE_L3.1_QCF 49,066 70,011 69,371
FLAG_L3.3_CUT_NONE_H_L3.1_QCF 84,975 56,071 47,402
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