Level-2: Quality flag expansion

Level 2 turns the quality information of the EddyPro output into one flag per test, FLAG_L2_FC_<TEST>_TEST (0 passed, 1 warning, 2 rejected), and combines them into the overall flag FLAG_L2_FC_QCF (see QCF). The tests are the same as in the 2016-2024 processing.

Notebook: 01_FPPC_IRGA72_NEE, Step 2.

Table 1: Level-2 tests of FC.

Flag	Test	Setting
SSITC	Steady state and developed turbulence (EddyPro)	Flag as reported
SCF	Size of the spectral correction factor	Warning from 2, rejected from 4
SIGNAL_STRENGTH	Signal strength of the LI-7200 (CUSTOM_SIGNAL_STRENGTH_IRGA72_MEAN)	Rejected below 60
CO2_VM97_SPIKE_HF	Spikes in the raw data (Vickers and Mahrt 1997)	Hard flag
CO2_VM97_DROPOUT_HF	Dropouts in the raw data (Vickers and Mahrt 1997)	Hard flag

Gas completeness, angle of attack and steadiness of the horizontal wind are not tested. In practice the SSITC test rejects nearly all records that Level 2 removes.

Latent and sensible heat flux

Notebooks: 11_FPPC_IRGA72_LE, 15_FPPC_IRGA72_H.

• LE uses the same tests, with its own SSITC and spectral correction flags and the raw-data tests of H2O.
• H comes from the sonic anemometer alone, so the tests of the gas analyser (signal strength, raw-data tests of CO2 and H2O) do not apply. The raw-data tests are those of the sonic temperature (T_SONIC_VM97_TEST): spikes, dropouts and absolute limits. The absolute-limits test is added for H, because a sonic temperature outside its plausible range indicates water or ice on the transducers.