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Meteorological day: Difference between revisions
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Steve Loft did make a simplifying assumption that does not align with the practice of most Meteorological Offices, Cumulus implements minimum temperature and rainfall differently. The World Meteorological Office (WMO) allows individual nations some flexibility, and does not prescribe total international alignment. | Steve Loft did make a simplifying assumption that does not align with the practice of most Meteorological Offices, Cumulus implements minimum temperature and rainfall differently. The World Meteorological Office (WMO) allows individual nations some flexibility, and does not prescribe total international alignment. | ||
The following table tries to illustrate the divergence: | The following table tries to illustrate the divergence if you choose a rollover time other than midnight: | ||
{| class="wikitable" border="1" | {| class="wikitable" border="1" | ||
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| Average temperature | | Average temperature | ||
| The WMO daily average is the average of the minimum in previous 12 hours and maximum in subsequent 12 hours, this ensures consistency with traditional climate statistics. Nations are permitted to use integrated averages for their internal purposes | | The WMO says that daily temperature average is calculated in different ways. Its preference is the average of the minimum in previous 12 hours and maximum in subsequent 12 hours, this ensures consistency with traditional climate statistics. | ||
| Cumulus maintains a total and a count for each day. The total is incremented by the actual temperature every time Cumulus processes a measurement (may be every minute for Cumulus 1, and every second for MX). The count is incremented by one each time a measurement is processed. The [[Average_temperature|average]] at the end of the day is just the total divided by the count. | * Prior to automatic recording, some stations would have manual recordings taken a few times a day, and if these were at 0600, 12:00, and 18:00, the mean might be calculated by adding the 3 readings, then adding the last again, and dividing by 4! | ||
* Nations are permitted to use integrated averages for their internal purposes. | |||
| Cumulus maintains a total and a count for each day. The total is incremented by the actual temperature every time Cumulus processes a measurement (may be every minute for Cumulus 1, and every second for MX). The count is incremented by one each time a measurement is processed. The integrated [[Average_temperature|average]] reported at the end of the day is just the total divided by the count. | |||
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| Rainfall | | Rainfall | ||
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| Sunshine Hours | | Sunshine Hours | ||
| Always reported by calendar day | | Always reported by calendar day (midnight to 23:59) | ||
| Regardless of which rollover time is selected, Cumulus always reports sunshine hours from one minute past midnight until midnight for any day | | Regardless of which rollover time is selected, Cumulus always reports sunshine hours from one minute past midnight until midnight for any day | ||
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