Description of the E-Mail Format For the Aerosols Protocol

NOTE: This version of the Aerosols Protocol e-mail format has changed considerably from (and is more complicated than) earlier versions. Do NOT use earlier versions, as they will not be accepted by GLOBE's computers!

There are several advantages to using the e-mail format for reporting GLOBE sun photometer data for the Aerosols Protocol, even though the format is complicated relative to some other GLOBE protocols.

1. Once you get used to using it, e-mail entry takes less time than online data entry.
2. It is easy to submit several days' worth of data all at once. You can mix several different protocols in the same e-mail entry. They don't have to be in chronological order.
3. If you have questions about data you have collected, you can send this format directly to me first, for my comments. (I have my own software to read and process data in this format.)
4. If you are working directly with me on a satellite ground validation project, we have probably agreed to save data reports even on days when you can collect only metadata. GLOBE will not accept such reports, but my software will.

Note that GLOBE forwards to me a copy of your data entries, even if you use online data entry, in e-mail format.

For each sample number all fields are required. At least three samples are required.

Note that times must be reported as Universal Time (UTC or UT), not local times. The data shown here are appropriate for observations just after clock noon during the summer on the east coast of the United States, for example. (EDT -- Eastern Daylight, or Summer, Time -- is four hours earlier than UT.) The data entry sheet for field use contains places for both local and UT times because it may be easier to use local times in the field. It is usually very difficult or impossible to tell whether you have converted times correctly. Depending on your time zone, reporting local hours will result in very strange AOT values or no results at all. It is more often the case that AOT values will still look reasonable even though the local hour has been reported. The AOT calculations depend strongly on the elevation angle of the sun which, of course, is directly related to time. So, errors in reporting time will produce AOT values that may look OK but, in fact, are wrong. Please be careful!

Each set of measurements starts with AZ (or az). A set of measurements may be continued on more than one line if there is not enough space on one line. This sun photometer is an older instrument. Newer instruments will have dark voltages of only a few millivolts (reported as 0.003, for example) or, in some cases, only a few tenths of a millivolt (reported as 0.0002, for example). There were some scattered altocumulus and cirrocumulus clouds when these measurements were taken. The sky color was light blue, the haze condition was somewhat hazy, the air temperature was 20° C, and the station pressure was 1009 mbar. (Presumably this value was obtained directly from an aneroid barometer calibrated at sea level.) There were 3 short lived contrails that covered less than 10% of the sky. With only 3 sets of voltages recorded, all the values for the last 2 samples must be set to missing. (See the string of 12 X's.) A satellite flew over at 16:08:12 UT with a maximum elevation angle of 67 degrees above the horizon. The case temperature before the reading was 24° C and after the reading it was 25° C. relative humidity was measured with a sling psychrometer, which gave 37% based on a dry bulb temperature of 20° and a wet bulb temperature of 12°.

Because the sky was not obscured and no sea level pressure value was reported, these fields are represented by X's. When you report barometric pressure, be sure to report actual pressure at your site as "station pressure" in Field 54. If you get barometric pressure from an online, broadcast, or newspaper source, it is invariably sea level pressure, and should be reported as such in Field 55. Note that because classroom aneroid barometers (as used for this example) are typically not very accurate, an online or broadcast weather report is the preferred source for sea level barometric pressure values. Regardless of whether you report sea level or station pressure, GLOBE will calculate the missing value based on your site elevation. A common mistake is to report sea level pressure in the station pressure field. This will lead to errors in the AOT calculation, especially if your site is at an elevation significantly above sea level. Please be careful!

The comment at the end of the format indicates the possibility of cirrus cloud contamination during the measurements.