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Meteorological day: Difference between revisions
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!style="width:800px" | Cumulus approach | !style="width:800px" | Cumulus approach | ||
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| Minimum Temperature | ! scope="row"| Minimum Temperature | ||
| The daily minimum temperature in the 12 hours (9 p.m. to 9 a.m.) prior to the traditional observation time is assigned to the date of that observation | | The daily minimum temperature in the 12 hours (9 p.m. to 9 a.m.) prior to the traditional observation time is assigned to the date of that observation | ||
| The daily minimum temperature in the 24 hours starting at the selected rollover time is assigned to the date of that rollover | | The daily minimum temperature in the 24 hours starting at the selected rollover time is assigned to the date of that rollover | ||
|- | |- | ||
| Maximum temperature | ! scope="row"| Maximum temperature | ||
| The daily maximum temperature in the 12 hours (9 a.m. to 9 p.m.) after the traditional observation time is assigned to the date that applies to both times | | The daily maximum temperature in the 12 hours (9 a.m. to 9 p.m.) after the traditional observation time is assigned to the date that applies to both times | ||
| Reported for day starting at 9 a.m. | | Reported for day starting at 9 a.m. | ||
|- | |- | ||
| Average temperature | ! scope="row"| Average temperature | ||
| 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. | | 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. | ||
* 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! | * 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! | ||
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| 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. | | 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 | ! scope="row"| Rainfall | ||
| Some nations report the daily rainfall for the 24 hours prior to the 9 a.m. observation time on a particular date. Others, throw their rainfall total back to previous date, i.e. the total for the 24 hours after 9 a.m on the particular date. | | Some nations report the daily rainfall for the 24 hours prior to the 9 a.m. observation time on a particular date. Others, throw their rainfall total back to previous date, i.e. the total for the 24 hours after 9 a.m on the particular date. | ||
| Cumulus assigns it to the date when the day started. | | Cumulus assigns it to the date when the day started. | ||
|- | |- | ||
| Sunshine Hours | ! scope="row"| Sunshine Hours | ||
| Always reported by calendar day (midnight to 23:59) | | 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 | ||
|- | |- | ||
| Snowfall | ! scope="row"| Snowfall | ||
| A snow day is reported by calendar day. The snow depth may be only reported at standard observation time of 9 a.m. (or as maximum that day) | | A snow day is reported by calendar day. The snow depth may be only reported at standard observation time of 9 a.m. (or as maximum that day) | ||
| For Cumulus 1, you select a particular time ([[Cumulus.ini_(Cumulus_1)#Read-only_parameters_in_the_Station_section|SnowDepthHour]]) and that is when the date changes, i.e. prior to that snow depth is assigned to yesterday, a snow index is calculated for any longer period (e.g. month or season). Cumulus 1 allows other information to be recorded in the [[Log.xml|Weather Diary]]. MX implements its [[diary.db]] slightly differently, and reports snow falling and lying as well as depth. | | For Cumulus 1, you select a particular time ([[Cumulus.ini_(Cumulus_1)#Read-only_parameters_in_the_Station_section|SnowDepthHour]]) and that is when the date changes, i.e. prior to that snow depth is assigned to yesterday, a snow index is calculated for any longer period (e.g. month or season). Cumulus 1 allows other information to be recorded in the [[Log.xml|Weather Diary]]. MX implements its [[diary.db]] slightly differently, and reports snow falling and lying as well as depth. | ||
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| Highest and lowest pressure | ! scope="row"| Highest and lowest pressure | ||
| Reported for day starting at 9 a.m. | | Reported for day starting at 9 a.m. | ||
| Reported for day starting at 9 a.m. | | Reported for day starting at 9 a.m. | ||