Progress in measuring and observing the urban atmosphere

Summary Observations of atmospheric conditions and processes in cities provide the cornerstone for advances in the understanding of urban climates and are crucial to improving the performance of urban atmospheric models. Here, recent progress in the observation and measurement of the urban atmosphere is considered in terms of: first, the research directions of those involved in conducting urban climate observations; second, advances in technology, both direct in terms of the development of new sensors and indirect in terms of computing power and capabilities in data analysis; and third, enhanced understanding of sensor placement. Increasingly, urban based observational programs are collaborative, multi-institutional, multi-national, interdisciplinary initiatives. This has important implications for the research questions addressed and the potential to investigate processes and effects across multiple spatial and temporal scales. Advances in technology have provided urban climatologists with new, improved and often more affordable instrumentation, and the ability to process and analyze data more rapidly. Greater understanding of urban atmospheric processes, and atmospheric sciences more broadly, have resulted in important insights into appropriate placement of meteorological instruments and the interpretation of results. An important issue that the urban climate community must address is how best to archive data so it is not lost. A database of current and past studies with key metadata about sites, instrumentation and data processing is proposed. Well documented and available urban data sets will enable future researchers to continue to extract valuable new insights and verify existing understanding about urban atmospheric processes. Urban field studies can be costly and time-consuming, so continuing to exploit the rich, significantly untapped, historical data sets will allow steady progress in urban atmospheric research to continue, provided funding are available for analysis of the data.