This presentation describes the urban observational facilities in Helsinki, coordinated by the Finnish Meteorological Institute, Vaisala Corporation, and the University of Helsinki. The observational facilities include the Helsinki Testbed and the SMEAR-III station.

Since January 2005, the Finnish Meteorological Institute and Vaisala Corporation have established and maintained a mesoscale atmospheric observational network in southern Finland. The Helsinki Testbed (HTB) is a research and operational program designed to provide new information on observing systems and strategies, mesoscale weather phenomena, urban and regional modeling, and applications in a high-latitude coastal environment. The HTB program features several components: observing system design and implementation, small-scale data assimilation and short-range numerical weather prediction, public service, and commercial development of applications. Specifically, the observing instrumentation focuses on meteorological observations of meso-gamma-scale phenomena that are often too small to be detected adequately by traditional observing networks. The domain of the HTB covers much of southern Finland and the Gulf of Finland. In particular, more than 40 communication masts, 60–100-m high, are equipped with new weather transmitters capable of measuring temperature, humidity, air pressure, rain, and wind speed and direction. Additionally, the number of radio soundings and ceilometer measurements are present, a wind profiler and dual-polarimetric radar have been installed, and four Doppler weather radars are available. The Helsinki Testbed supports the development and testing of new observational instruments, systems and methods in concentrated field experiments, like the NASA Global Precipitation Measuring Mission.

The SMEAR-III urban measuring station consists of a 31-m tower, equipped with meteorological instrumentation at several heights. Measurements include profiles of the temperature and wind and radiation components. The fluxes of sensible heat, momentum, carbon dioxide and water vapour are measured by eddy covariance technique. Next to the tower is situated an air conditioned container where large diversity of aerosol particle and gas concentration instrumentation is located. Aerosol measurements include size distributions and chemical composition and optical properties.

The heart of the data assimilation system is Local Analysis and Prediction System (LAPS) developed by NOAA Earth Systems Research Laboratory's Global Systems Division. Although LAPS presently can be run operationally using the HTB data, much work remains to determine the optimal configuration (e.g., domain, resolution, use of ensembles, sensitivity to assimilation parameters) to provide the best analysis and forecasts. A research program to explore the sensitivities of the LAPS configuration to the performance of the analyses is presently being developed. The results of this program will immediately benefit the LAPS implementation using the HTB, but will inform future commercial users of the HTB, as well as the data assimilation and numerical weather prediction communities.