In the last several years, there has been a tremendous expansion in the number of non-NWS automated weather stations, and groups of weather stations (commonly referred to as "mesonets"), operating across the United States. The expansion reflects the need by many organizations for densely spaced, real-time surface observations to aid in, for example, agricultural monitoring, energy and transportation planning, emergency management, fire management, and meteorological research. To fill these needs, many state and local government agencies, public utility companies, research organizations and private industries have installed mesoscale meteorological observing systems.

Among these systems are the Environmental Sensor Stations (ESS) installed and operated by state departments of transportation. It is estimated that more than 1300 ESS sites have been installed nationwide to provide observations of meteorological variables such as pressure, temperature, and winds, as well as road variables such as pavement temperature and road condition. Acquisition of data from these stations would dramatically increase the number and frequency of observations available for weather analysis and prediction purposes, and has the potential to enable numerical weather prediction models to better capture local and mesoscale weather phenomena.

Despite these considerations, however, a true national-scale integration of mesonet observations has not yet been undertaken. To fill this need, NOAA's Forecast Systems Laboratory (FSL) has implemented a system to ingest, integrate, quality control, and distribute mesonet observations on a national scale through its Meteorological Assimilation Data Ingest System (MADIS). MADIS currently ingests over 5600 mesonet observations from across the country, including ESS observations from 10 state departments of transportation, quality controls the observations, and then supplies them to other meteorological organizations. Organizations already receiving MADIS datafeeds include the National Centers of Environmental Prediction (NCEP), the National Center for Atmospheric Research (NCAR), and several private meteorological firms and major universities.

This paper will cover the current status of mesonet observations in the MADIS database, both in terms of ingest and distribution, and will also describe the quality control techniques applied to the observations.