GOME2-O3-ACSAF Results

According to the metadata the temporal extent of this dataset is 2017-11-23-ongoing.
https://navigator.eumetsat.int/elastic-csw/download/EO%3AEUM%3ADAT%3AMETOP%3AEARS-IASI-L2
In this case, the testfile is the netcdf with name:
W_XX-EUMETSAT-Darmstadt, HYPERSPECT+SOUNDING,METOPB+IASI_C_EUMP_20200723093252_40713_eps_o_l2.nc
Where we initially filtered the product using the following configuration of quality flags:
‘flag_itconv’== 5 AND ‘flag_retcheck’== 0 AND ‘flag_iasibad’== 0
In the test file (113 MB) 19281 products on a total of 19344 fulfil the desired flag configuration.
In this case the retrieval does not happen in the profile space but in the so-called principal component space. The state vector is here composed by 28 elements that corresponds to the eigenvalues associated with a fixed set of eigenvectors that must be used to reconstruct the actual profiles, once the retrieved eigenvalues are known.
For temperature we applied a supplementary filtering strategy that discards the retrieved state vectors that have values separated from the correspondent a priori value by more than 5 times the a priori error and this is an extremely rare condition in a well-behaved retrieval.
According to this strategy we selected 3880 products in the test file, that are represented in Figure 5. In Figure 6 the average distance between each pixel and its nearest neighbour is 21.68 km. For the product under test (Figure 6) the ratio of the largest and the smallest elements (principal components) is -3.907e-01.