The Citizen Weather Observer Program (CWOP) is a private-public partnership with three main goals: 1) to collect weather data contributed by citizens; 2) to make these data available for weather services and homeland security; and 3) to provide feedback to the data contributors so that they have the tools to check and improve their data quality. In fact, the program's web address, wxqa.com, stands for Weather Quality Assurance. CWOP currently comprises over 6.000 registered members worldwide. Some 3,000-4.000 are reporting routinely via internet server connections. The data are passed to the NOAA GSD Meteorological Assimilation Data Ingest System (MADIS) and subjected to a series of quality checking (QC) applications. The QC metadata values are provided with the data when it is served by MADIS. CWOP data have traditionally used a shared internet infrastructure for acquisition and aggregation. Data are sent at station-independent observation rates of 5- to 15-minutes, with some outliers reporting less frequently. Current recommendations are for 15-minute observation intervals, however, during a transition of infrastructure systems. After the transition is completed, 5-minute observations will be supported and experiments at data collection at higher rates will be commissioned. CWOP has historically used a shared data infrastructure for acquisition, aggregation, and transmission to MADIS. In January, 2008, however, a spike in the number of data packets on the distribution system caused the system operators to consider the need to separate the two services on the common infrastructure. CWOP initiated its own infrastructure in mid-February, 2008, and completed the transition in mid-July. In the process of transition, some reporting stations failed to heed the call to change to dedicated CWOP servers and were lost. The total number of stations lost to follow-up both transiently and long-term, remains to be determined at the time of this writing, but in the first 24 hours of the final transition, some 36% of CWOP stations were not reporting appropriately. Initial response from CWOP members who noted the loss of data availability has been strongly positive, however, and we anticipate recovering the majority of stations over time. CWOP instrumentation runs the gamut from high-end professional and research grade hardware (including at least one retired ASOS system) to consumer-grade hardware, with the majority of stations manufactured by Davis Instruments, although other vendors are well-represented. Station siting rarely conforms to World Meteorological Organization guidelines for surface observations because urban sites rarely have an area that is sufficiently large enough to be obstruction-free into the far-field for wind measurement, and, because some of the instrumentation is in the form of “All-In-One” devices incorporating anemometry, temperature, humidity and precipitation measurement into a single housing. Participants are asked to provide installation photos to augment station metadata to allow normalization of site installations. The majority of CWOP stations tend to cluster in urban environments. As a result, high-resolution observations of meteorological phenomena are possible. As the frequency of observations is increased, the utility of these observations becomes more apparent. A large component of CWOP stations, however, are located in rural regions, affording increased densification of observation in areas that have traditionally been under-observed. Data derived from CWOP observations can prove valuable in verification of meteorological events, as well as enhancing forecast and nowcast activities. The densification of observation afforded by CWOP to conventional ASOS/AWOS observations can provide significant benefit in data assimilation for forecast models as well as providing a more dense observation network for forecast and event verification. CWOP data are available to NWS WFOs via AWIPS (MADIS is available to AWIPS workstations), and to the research community via the MADIS Internet Data Distribution stream using the Unidata LDM software. Third-world and developing nations traditionally have limited resources for mesoscale observations, much less increased-density urban meteorological observations. We posit that CWOP will, over time, provide ample evidence that the use of modestly-priced, consumer-grade instrumentation will be shown to provide sufficient observation quality and repeatability to be useful in other regions of the world, supplementing traditional surface observing systems, where high-priced weather instrumentation is a barrier to high-spatial-resolution observations.
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