Diurnal cycle of specific humidity for in situ data (black markers) and ERA5 data (coloured markers). The coloured lines indicate ERA5 data on pressure levels 600 hPa (dark-yellow; a), 750 hPa (bright blue; b and h), 775 hPa (green; c), 800 hPa (blue-violet; d and e), 850 hPa (olive; g) and 900 hPa (royalblue; f). The grey and coloured shadings represent the standard deviation of the in situ and ERA5 data based on hourly averaged data, respectively. Time is in universal time (UT).