**Data
processing methods**

**Procedure
to Calculate Daily and Monthly Totals**

1. Daily totals of downwelling and upwelling longwave radiation is determined in case the data for all hour intervals of the 24-hour period are available.

If at least one hourly total value is missing, the daily total is not calculated.

2. Daily totals of global, diffuse and direct normal radiation are determined in case the data for all hour intervals of the daytime are available, with the exception of sunrise and sunset hour intervals.

To avoid unduly great losses of daily totals due to the gaps in the data for sunrise and sunset hours, the following procedure of data processing is accepted.

In case observational data are missing for the above-mentioned
hour intervals on a number of days, we recommend to determine h_{s} (sun's altitude) for those hours.

If h_{s} > 5° , the lack of an hourly total is identified as the lack of observation,
and the daily total is not determined for that day.

If h_{s} £ 5° , the daily total is calculated in similar situation.

3. If data for each day of the month are available:

a) the monthly total is calculated by adding together daily/hourly totals for each day of the month;

b) the monthly mean of daily/hourly totals is calculated by dividing the monthly total by the number of days in the calendar month.

4. If there are days with missing data, first of all the monthly mean of daily/ hourly totals is calculated and then monthly total is obtained:

a) the monthly mean of daily/hourly totals is calculated by dividing the sum of daily/hourly totals for the days with available data (including estimated and questionable values) by the number of days with observations;

b) the monthly total is calculated by multiplying the monthly mean of daily/ hourly totals by the number of days in the calendar month.

5. If there are 10 or more days with missing daily/hourly totals, the monthly total and the monthly mean of daily/ hourly totals are not calculated.