Today in the United States, nearly eighty percent of the population lives within the urban environment. Descriptions of the urban climate can no longer rely on observations from the communities major airport(s). The National Climatic Data Center's new Metropolitan Area Climate (MAC) Summary, for the first time, presents a picture of the climate across the whole of the urban area.
During the past several years, several events have taken place that makes the urban areal climate description possible. For starters, there are now four times the number of sites reporting hourly and daily data with the introduction of the National Weather Service/Federal Aviation Administration's ASOS instruments. Weather reports are now available for some 850 sites across the United States, giving some large metropolitan areas multiple stations. Daily observations from the 8,000 Cooperative Observer sites that once took months to digitize now are becoming available on a daily basis. To supplement and complement ASOS observations a series of new programs are producing areal based observations, such as GOES, NEXRAD, and lightning strike detection.
The MAC Summary is a user friendly product that describes the climate across the complete urban area. It presents the climatological parameters most frequently requested by the urban user. It draws on the strengths of the ASOS, Cooperative observer, NEXRAD, and other data sources, to integrate them into one presentation. The MAC presents daily and monthly temperature, precipitation, snow, degree day, weather, and pressure data. Daily extremes values are available for winds and statistics are presented on the number of days or hours that certain thresholds were exceeded. The MAC is available in a timely fashion, accessible on the Web or by paper copy (which is certifiable.)
This paper will describe the new MAC Summary including results of initial feedback to the prototype summary.