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The planetary-boundary layer (PBL) plays an important role in air-pollution studies over urban/industrial areas. Therefore, numerous experimental/modelling efforts have been conducted to determine the PBL height and provide statistics. Nowadays, remote-sensing techniques such as ceilometers are valuable tools in PBL-height estimation. The National Observatory of Athens operates a Vaisala CL31 ceilometer. This study analyses its records over a 2-year period and provides statistics about the PBL height over Athens. A specifically developed algorithm reads the CL31 records and estimates the PBL height. The algorithm detects an upper and a lower PBL curve. The results show maximum values of about 2500 m above sea level (asl)/3000 m asl in early afternoon hours in all months for upper PBL, and particularly the summer ones, under all-/clear-sky conditions, respectively. On the contrary, the lower PBL does not possess a clear daily pattern. Nevertheless, one morning and another afternoon peak can be identified. The intra-annual variation of the upper PBL height shows a peak in August in all-weather conditions and in September under clear-sky ones. Season-wise, the upper PBL height varies showing an autumn peak for all-weather cases, while the lower PBL height shows a winter maximum due to persistent surface-temperature inversions in this season.

<p>It is generally accepted that a climatic data set of meteorological measurements with true sequences and real interdependencies between meteorological variables is needed for a representative climate simulation. In the late 1970s the Typical Meteorological Year (TMY) concept was introduced in USA as a design tool for approximating expected climate conditions at specific locations, at a time when computers were much slower and had less memory than today. A TMY is a collation of selected weather data for a specific location, listing usually hourly values of meteorological and solar radiation elements for one-year period. The values are generated from a data bank much longer than a year in duration, at least 10 years. It is specially selected so that it presents the range of weather phenomena for the location in question, while still giving annual averages that are consistent with the long-term averages for the specific location. Each TMY data file consists of 12 months chosen as most “typical“ among the years present in the long-term data set. Although TMYs do not provide information about extreme events and do not necessarily represent actual conditions at any given time, they still reflect all the climatic information of the location. TMY sets remain in popular use until today providing a relatively concise data set from which system performance estimates can be developed, without the need of incorporating large amounts of data into simulation models. </p><p>TMY sets for 33 locations in Greece distributed all over the country were developed, covering for the first time all climatic zones, for both historical and future periods. Historical TMY sets generation was based on meteorological data collected from the Hellenic National Meteorological Service (HNMS) network in Greece in the period 1985-2014, while the corresponding total solar radiation values have been derived through the Meteorological Radiation Model (MRM).</p><p>Moreover, the generation of future TMY sets for Greece was also performed, for all 33 locations. To this aim, bias adjusted daily data for the closest grid point to the HNMS station’s location were employed from the RCA4 Regional Climate Model of the Swedish Meteorological and Hydrological Institute (SMHI) driven by the Earth system model of the Max Planck Institute for Meteorology (MPI-M). Simulations were carried out in the framework of the EURO-CORDEX modeling experiment, with a horizontal RCA4 model resolution of 0.11<sup>o</sup> (~12 x 12 km). We used daily data for four periods: the 1985-2014 used as reference period and the 2021-2050, 2046-2070 and 2071-2100 future periods under RCP4.5 and RCP8.5 scenarios. </p><p>This work was carried out in the framework of the “Development of synergistic and integrated methods and tools for monitoring, management and forecasting of environmental parameters and pressures” (KRIPIS-THESPIA-II) Greek national funded project.</p>