The present dataset of air ion mobility and aerosol particle size distributions is a follow-up of the dataset Tahkuse_1993_1994, http://datadoi.ut.ee/handle/33/22. It makes available results of routine measurements in Tahkuse Air Monitoring Station from 01.01.2004 to 31.12.2014. The station is located in the Sepa farmhouse in Tahkuse village about 27 km northeast of the city of Pärnu, Estonia. Geographical coordinates are 58º31'28"N, 24º55'32"E, 24 m a.s.l. The farmhouse is surrounded with flat open landscape with some tree groups, grassland and agricultural land. The level of air pollution is typical for atmospheric air at a sparsely populated rural area. The dataset includes results of simultaneous measurements of positive and negative air ions and neutral aerosol particles. The small air ions are charged molecules and clusters up to 1.6 nm, the intermediate and large air ions are charged fine aerosol particles of size 1.6 – 70 nm. The air ion spectrometers are the same as used in Tahkuse during 1993 – 1994. Important upgrades of the instrumentation are taking into use the aerosol particle size spectrometer EAS and the AlphaGUARD radon monitor. The spectrometers are installed in the attic of the building. The air intake is at a height of 5 m above the ground. The continued measurements of wind speed, wind direction, air temperature, relative humidity, and concentration of NO2 are complemented with measurements of air pressure, sun radiation and radon activity concentration. The detailed description of the landscape, station, and instruments is presented in the thesis by Hõrrak, U. (2001) Air ion mobility spectrum at a rural area, https://dspace.ut.ee/handle/10062/50218. The measurements are saved into 11 yearly files as a tab-separated ANSI text. The zip-package of files should be downloaded from the present website, unpacked and operated in the personal computer of the scientist. The data can be immediately opened and analyzed using MS Excel as well as by means of different computer programs, which are able to process the ANSI text. Every file consists of a table with 114 columns and 8761 or 8785 rows. The columns correspond to variables and rows to measurement hours. The data are written without omissions for 24 hours per day even when the measurements were stopped or failed and the values of variables are unknown. The missing values are marked with the code –99. The data is accompanied with an instruction for the user Tahkuse_data_2004–2014_guide.pdf and a presentation of data preparation algorithms Tahkuse_data_2004–2014_supplement.pdf. The authors acknowledge Aadu Mirme for great work designing the original instrumentation.
