Calculation Methods for Mean Field Values

For each minute mean in the IAF2.0 archive file we have either:

or

Additional non-reported components can be calculated (click here for details) from this minute mean giving a complete set of values for the m th minute mean as follows:

The hourly and daily means for the first three components are read from the archive file. For each other component an hourly or daily mean can be calculated directly by taking a mathematical mean of that component individually across all the minute mean values (click here for details). A component hourly or daily mean derived directly from the minute means in this way is denoted by a ‘bar’, and a component hourly or daily mean read from the archive file is denoted in bold, giving a set of hourly or daily mean values as follows:

or

(Note: if the hourly or daily mean for a component can be read from the archive file, then the archive value is the one which will be used, and no other calculation will ever be made on that component, whichever option is chosen)

Option 3 ‘Calculate all components from the minute mean values’ will display these values, but this set of values gives members that cannot be derived from each other, for example:

The Data viewer offers 2 other options, both of which give a final set of mean values where the relationship between the components is as expected. In both these options only four values are calculated from the minute means, and all other components are derived from these four. The table below shows a summary of the differences in the three calculation methods. The final values displayed by the Data viewer are denoted here as:

Summary of Different Calculation Methods for Hourly and Daily Means

Component | Option 1: Calculate FDiff mean and derive other components | Option 2: Calculate FScalar mean and derive other components | Option 3: Calculate all components from the minute means
Where a cell is split, the left side shows values used if the reported component code is XYZG and the right side shows the values if the reported component code is HDZG
Notes | Options 1 and 2 give a set of hour or daily mean values where component members can be derived from each other. | This option gives a set of hour or daily mean values all directly derived from the minute means, but component members cannot be derived from each other
Missing values can also cause differences between the calculation methods
Also note |

Missing Values

Occasionally, there is only a FScalar value recorded, and the XYZ or HDZ are missing. In this case the FScalar value will contribute to the value of ,but not which will also contribute to differences in the calculation methods. Similarly, if any of the other components are missing, there will be further differences in the three methods.

Calculating a component mean from the set of m minute means

Individually, the calculations are as follows:

Component | Calculation | Notes
|  | These calculations will only be done if the hourly or daily means cannot be read directly from the archive file, and only if option 3 is chosen
|  | This calculation is only used if options 1 or 3 are chosen
|  | This calculation will only be used if option 3 is chosen
|  | This calculation is only used if options 2 or 3 are chosen

Calculating minute mean values for non-recorded components