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Definition | Standard deviation (std) of O-B values over a defined period |
Calculation | For each observed variable, the std of all valid data is computed for every station. |
Valid data | Data not flagged as missing value (O-B is not NULL) |
Minimum required valid data | Daily: 2 valid values |
Math expression | , where Nj is number of valid data for variable j and the bar denotes the average as defined in Table 43. |
Both bias and standard deviation contribute to the overall measurement uncertainty. The root mean square error (rmse) is a common metric used to measure accuracy, and it is applied to upper-air observations in the WDQMS web tool (section 6.2) based on the quantitative information for the two vertical layers (mean and standard deviation of O-B departures over Trop and Stra, see section 2.2) provided by the NWP reports (see Table 5).
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