Date(UTC) (960317 – 960413)
The date is given as UTC in the form YYMMDD.
UTC (Scheduled) (00:00 – 23:59)
UTC (Actual) (00:00 – 23:59)
Observations were scheduled hourly, on the hour, 24 hours per day. As expected, adhering strictly to this schedule proved impractical. Most observations were therefore made a few minutes before or after the scheduled time — however in some extreme cases scheduled and actual observation times can differ by a substantial fraction of an hour, and very occasionally observations were missed entirely. Both times are given as UTC in the form HH:MM.
Heading (0–360)
For this section, the approximate ship heading as displayed on the VT220 terminal in the plot room was recorded. This is used to give a reference point from which compass directions for weather observations can be established (see next section).
LocSun (0,1,2,3,4,5)
ObscSun (1,0)
LocSun gives the "quadrant number" in which the sun is found at the time of the observation. Based on ship geometry, the quadrant number refers to a region of the sky which, in the full Excel version of the log, can be converted to an absolute compass direction. Common also to the cloud section of the observation log, the practice of dividing the hemisphere of the sky into regions was used to give a potentially useful measure of sky inhomogeneity and make cloud observations easier to make. The regions are identified as follows: Quadrant 1 is the quadrant of the ship containing the port bow and bounded by planes passing through the bow-stern line and the line demarcating amidships, Quadrant 2 contains the port stern and quadrants 3 and 4 continue around the ship in a counter-clockwise fashion. The near-zenith section, which is referenced in the numeric-only data as "Quadrant 5", consists of an inverted cone with sides at an angle of some 11 degrees to the mast. A zero, or more commonly a missing data entry, indicates night time, or an inability to locate the sun because of heavy cloud cover.
The Sun Obstruction (ObscSun) parameter gives a simple yes/no indication of whether there were any visible clouds between the sun and the observer. A zero in the ObscSun column, for example, indicates no visible obstruction from clouds of any type. See also Zenith/Solar Transparency, sub-section iv) below.
All observations for this section are done separately for each of the five sky regions described above. An example for quadrant Q1 follows.
Q1Overall (0–100)
Q1Low (0,1)
Q1Mid-level (0,1)
Q1High-level (0,1)
Q1Lowest (0–100)
Raining (0,1)
This column measures if there is rain (1) or no rain (0) falling at the ship at the time of the observation. No indication of intensity is given.
Sea State (0–12)
Wave height (0– )
The prevailing sea state can be described by a category number, as shown in photographs from The American Practical Navigator. The appearance of the sea surface was compared with these photographs, giving a category number from 0 to 12. While strictly the Beaufort scale for estimating wind speed, these photographs enabled us to obtain a useful quasi-objective indicator of ocean roughness.
Wave height (given in feet) was difficult to judge, especially in the presence of a swell. Generally, the height of the largest oscillation present (peak-to-peak) was entered. It was felt, after an excursion by UW–Madison personnel in the Discoverer's RHIB, however, that these values may be somewhat underestimated.
AERI Uncovered (0,1),
Bow Wake Disturbance (0–100)
The AERI Uncovered column indicates whether the AERI was covered with the tarpaulin (0) or not (1). This does not necessarily indicate whether the AERI is operating, but a covered AERI (0) is usually associated with inclement weather.
The percentage of time during which a 35 degree (from nadir) view is seeing disturbed water as a result of the bow wake is recorded in the Bow Wake Disturbance column. This gives a separate indicator of sea state; however this parameter was essentially an afterthought and is not available on a regular basis.
Recorder (1,2,3,4)
The observer taking the measurement is identified as follows: 1 Brian Osborne, 2 John Short, 3 Nick Nalli, 4 Robert Knuteson. Please note that this is not the order during the day with which observers rotate: this order is 1,3,4,2.
Photo Taken (0,1)
This column indicates whether a weather record photo (1) or not (0) was taken. Generally whenever there is enough light, a photo is taken. The Photographic Weather Observation Log is a separate entity, also compiled by the UW–Madison group, in which a 35-mm camera fitted with a wide-angle (28-mm) lens, records weather conditions off the port bow every hour. This archive is available on CDROM.
Comments
Any other additional information about cloud, sea, or other weather conditions is entered in this column. Further useful comments are available in the photographic log index.