Why is data reported as missing?
There are a variety of reasons as to why data may be reported as missing on the web page. Missing data can be described as either data that has not been retrieved from the monitoring site or data that is not considered valid. The monitor may be a seasonal monitor, such as most of the ozone sites, and only operate for part of the year. For the time that it is not in operation the data will be reported as missing. There are some basic data quality tests that are conducted as the data is collected. If the data does not pass those tests it will be reported as missing. Most of the data reported is collected through the use of dial up modems. In some cases the computer is not able to connect to the site and the current hour of data is then reported as missing. As soon as the computer is able to make a connection it will collect any missing data that is available and fill in those hours with actual data. Finally, data that has been collected and has appeared on the web page may be invalidated
