Validation CAMS Radiation - INPE stations

Date of the validation: Jan. 2016
Network: INPE, Brazil
Number of stations: 11 (see Table 1).
Original time step and radiation components: 1 min GHI measurements
Author: Etienne Wey, Lucien Wald, Philippe Blanc and Claire Thomas
Publication: -

The 1-min measurements were originally quality checked using the procedure described here. As only the GHI component is available in the observations for both datasets, no consistency check is possible via cross-comparison from one component to another. Unfortunately, this protocol turned out to be insufficient for these hourly measurements and that the test to discard the not plausible values ("Extremely Rare Limits" and "Physical Possible Limits") were too permissive; Too many outlyers remained after the QC. Prior the computation of the different quantities to assess the deviation between the satellite estimates and the station measurements as depicted in the protocol of validation, we decided to discard also the measurement values when they are:

• below 2% * clear sky dry, which corresponds to the ESRA clear sky with no turbidity
• above 120% * clear sky dry
• time shift in the data was also observed for several days in the time series. We decided that if more than 10% of the values were located during nightime, the whole day is discarded.

We remind that the other steps are:

• Set night, sunrise and sunset observation values to zero
• As soon as the quality check procedure is over, then aggregate the 1 min values to generate the hourly values if at least 85% of the 1-min slots are available. Apply an intelligent mean which takes into account the sun position at each minute.
• Then the hourly values are aggregated to generate partial daily and monthly sums as depicted in the protocol of validation.

Illustration: list of the stations used for the validation (INPE stations in white) =>