Quality-checked meteorological data from the Southern Ocean collected during the Antarctic Circumnavigation Expedition from December 2016 to April 2017. Data files: ACE_filtered_meteorological_data_1min.csv File header: date_time: date and time of the middle of the time period over which the measurements were averaged in ISO 8601 format YYYY-MM-DDThh:mm:ss+00:00 [UTC] latitude: latitude of the ship at the position of the date_time [decimal degrees North] longitude: longitude of the ship at the position of the date_time [decimal degrees East] VIS: horizontal visibility [metres] CL1: height of first cloud level (if SC1==9: CL1 provides the vertical visibility) [metres] CL2: height of second cloud level [metres] CL3: height of third cloud level [metres] SC1: Sky cover at first cloud level (If SC1=9 CL1 provides the vertical visibility) [octants, 9] SC2: sky cover at second cloud level [octants] SC3: sky cover at third cloud level [octants] RH1: relative humidity measured by the port sensor [%] TA1: air temperature measured by the port sensor [degrees Centigrade] DP1: dew point provided by the port sensor [degrees Centigrade] TW1: wet bulb temperature calculated from RH1 and TA1 [degrees Centigrade] PA1: atmospheric pressure measured by the port sensor [millibar] RH2: relative humidity measured by the starboard sensor [%] TA2: air temperature measured by the starboard sensor [degrees Centigrade] DP2: dew point provided by the starboard sensor [degrees Centigrade] TW2: wet bulb temperature calculated from RH1 and TA1 [degrees Centigrade] PA2: atmospheric pressure measured by the starboard sensor [millibar] SR1: solar radiation measured by the port sensor [Watts per square metre] SR3: solar radiation measured by the starboard sensor [Watts per square metre] UV1: ultraviolet radiation measured by the port sensor [Watts per square metre] UV2: ultraviolet radiation measured by the startboard sensor [Watts per square metre] WSR1: relative wind speed measured by the starboard sensor (affected by flow distortion) [metres per second] WDR1: relative wind direction (from) measured by the starboard sensor (clockwise from the bow. E.g. +90 denotes wind coming from starboard; affected by flow distortion) [degrees] WSR2: relative wind speed measured by the port sensor (affected by flow distortion) [metres per second] WDR2: relative wind direction (from) measured by the port sensor (clockwise from the bow. E.g. +90 denotes wind coming from starboard; affected by flow distortion) [degrees] HEADING: ship heading, clockwise from North [degrees] SOG: ship speed over ground [metres per second] COG: ship course over ground, clockwise from north [metres per second] WS1: wind speed relative to ground computed from starboard sensor readings and the ship’s heading and velocity (results are affected by flow distortion) [metres per second] WD1: wind direction (from) computed computed from starboard sensor readings and the ship’s heading and velocity (results are affected by flow distortion; clockwise from North E.g. +90 denotes wind coming from East) [degrees] WS2: wind speed relative to ground computed from port sensor readings and the ship’s heading and velocity (results are affected by flow distortion) [metres per second] WD2: wind direction (from) computed computed from port sensor readings and the ship’s heading and velocity (results are affected by flow distortion; clockwise from North E.g. +90 denotes wind coming from East) [degrees] sol_altitude: solar altitude, with zero at the horizon and positive when the sun is above the horizon [degrees] sol_azimuth: azimuth is reckoned with zero corresponding to north. Positive azimuth estimates correspond to estimates east of north; negative estimates, or estimates larger than 180 are west of north [degrees] SR1_shadow_mask: Flag indicating if SR1 (port side sensor) is likely shadowed by the ship’s structure (don’t use SR1 if the mask is True) [boolean] SR3_shadow_mask: Flag indicating if SR3 is likely shadowed by the ship’s structure (don’t use SR3 if the mask is True) [boolean] TATWDPRH1_heat_island_mask: Flag indicating if the port sensor readings (TA1, RH1, DP1, and TW1) are likely affected by heating of the air passing over the ship (the readings are likely affected if the mask is true) [boolean] TATWDPRH2_heat_island_mask: Flag indicating if the starboard sensor readings (TA1, RH1, DP1, and TW1) are likely affected by heating of the air passing over the ship (the readings are likely affected if the mask is true) [boolean] TATWDPRH1_relhum_mask: Flag indicating if the port sensor readings do not fulfill the conditions (DP1 <= TW1 <= TA1) and RH1<=100% (if the mask is true the readings are assumed to be physically not correct) [boolean] TATWDPRH2_relhum_mask: Flag indicating if the starboard sensor readings do not fulfill the conditions (DP2 <= TW2 <= TA2) and RH2<=100% (if the mask is true the readings are assumed to be physically not correct) [boolean] Null values NaN has been used to represent data values that are missing or that did not meet quality-checking criteria and where therefore removed (see README.txt for full details). The CL1,2,3 can have the value Inf (infinity) when SC1,2,3 are zero, i.e. no clouds detected.