LOCAL CLIMATOLOGICAL DATA (LCD) EXPLANATION FILE This file explains how to read the monthly local climatological data (LCD) files. These files are available for the period of record of January 1957 until present. The file naming convention is MMYY.lcd, where MM = two digit month and YY = two digit year (i.e., 0997.lcd is the LCD file for September 1997). On 01 January 1997, Amundsen-Scott South Pole Station redefined its climatological day as 0000-2359 Universal Coordinated Time (UTC). With the exception of the three year period of 1994 through 1996, this definition is consistent with South Pole Station's meteorological record. From January 1994 through December 1996, the climatological day was defined as 0000-2359 New Zealand Standard Time. Daily data from these years was reprocessed to use Universal Coordinated Time. Another significant change affecting the LCD was the transition from Surface Aviation Observations (SAO) code to the World Meteorological Organization's (WMO) Aviation Routine Weather Report/Aviation Selected Special Weather (METAR/SPECI) code formats. This transition occurred at 0000 UTC 01 June 1997. Affected by the METAR/SPECI transition were the symbols used for daily weather occurrences. This change, as it affects the LCD file, is detailed below. Also, beginning with the June 1997 file, sky cover amounts are reported in oktas (8ths), and not tenths (10ths). Daily maximum temperature: Minus degrees Celsius. Daily minimum temperature: Minus degrees Celsius Daily average temperature: Minus degrees Celsius. The average of all available observations for the day. This could range from 4 to 24 observations. Previously the daily average temperature had been calculated as the average of the maximum and minimum temperatures. All months have been reprocessed to use all available daily observations. Precipitation: Liquid equivalent, always recorded as a trace (T) after March 1958. Liquid equivalent to the nearest one hundredth of an inch from January 1957 - March 1958. No precipitation is recorded as a "0". Daily average wind direction: Prevailing wind direction for the day, i.e. the direction with the highest number of occurrences. Wind direction observations are two-minute averages recorded to the nearest ten degrees. South Pole Station uses a grid system in which 360 degrees corresponds to the prime meridian. Daily average wind speed: Average of twenty-four hourly observations in miles per hour (mph) to the nearest tenth. Each hourly observation is a two-minute average wind speed. Daily fastest mile (correctly labeled as Peak Wind beginning in Jan. 2000): This is the highest instantaneous speed in miles per hour (mph), as obtained from the wind direction and speed recorder. Daily fastest (peak) direction: The grid direction of the highest instantaneous speed to the nearest ten degrees. Daily Sunshine: Total sunshine to the nearest tenth of an hour. Estimated by suncards burned on a Campbell-Stokes sunshine recorder. Daily Sky Cover: Average sky cover reported in tenths (oktas beginning in June 1997). The average is based on four synoptic observations daily from mid-February through late October. During the austral summer, from November through mid-February, the value is the average of up to twenty-four hourly observations daily. Sky cover not only includes opaque and translucent clouds, but also surface-based obscurations (i.e., blowing snow, fog, etc.). Daily station pressure: Average station pressure in tenths of millibars (hPa), as computed from twenty-four hourly observations daily. Daily weather occurrences (WX): Observed weather phenomena, including precipitation and obscurations. No intensities. From January 1957 through May 1997, SAO notations were used: S - snow K - smoke SG - snow grains IF - ice fog SP - snow pellets F - fog IC - ice crystals BS - blowing snow SW - snow shower From June 1997 to present, METAR/SPECI notations are used: SN - snow FU - smoke SG - snow grains FZFG - freezing fog GS - snow pellets BR - mist (fog with vis 5/8 mile or more) IC - ice crystals BLSN - blowing snow Other METAR/SPECI qualifiers may precede the precipitation or obscuration: SH - shower MI - shallow PR - partial BC - patches VC - vicinity Row 42: Average monthly maximum temperature: Average of daily maximum temperatures in minus degrees Celsius. Average monthly minimum temperature: Average of daily minimum temperatures in minus degrees Celsius. Monthly average temperature: Average of daily average temperatures using all available observations. Minus degrees Celsius Average monthly wind direction: Prevailing grid wind direction, i.e. the direction with the highest number of occurrences. Average monthly wind speed: Average of the daily wind speeds in miles per hour (mph). Monthly maximum instantaneous speed/Day of occurrence: Maximum instantaneous wind speed (peak wind) in mph / day of occurrence. Average sunshine per day: Average hours of sunshine per day to the nearest tenth of an hour. Average monthly sky cover: Average sky cover per day in tenths (oktas beginning June 1997). Average monthly station pressure: Average station pressure to the nearest tenth of a millibar. Computed by averaging the daily average pressure values. Row 44: AVG MONTHLY: Average of daily average temperatures using all available observations. Degrees Celsius. (Same value as line 42). PCPN: Monthly total precipitation. Always recorded as a trace. NR DAYS CLEAR: Number of clear days (0-3 tenths or 0-2 oktas sky coverage). Row 45: HIGHEST: Maximum monthly temperature in degrees Celsius. SUNSHINE: Total sunshine for the month, to the nearest tenth of an hour / percent of possible sunshine PARTLY CLOUDY: Number of partly cloudy days (4-7 tenths or 3-6 oktas sky coverage). Row 46: LOWEST: Minimum monthly temperature in degrees Celsius. CLOUDY: Number of cloudy days (8-10 tenths or 7-8 oktas sky coverage). Row 47: HIGH PRESSURE: Maximum monthly station pressure in millibars, followed by the day of occurrence. Row 48 LOW PRESSURE: Minimum monthly station pressure in millibars, followed by the day of occurrence. Row 49: NET CHANGE IN SNOWSTAKE FIELD: Net average change in fifty snowstakes located approximately 1/2 mile grid southeast of station. Reported in inches. Row 50: VECTORED WIND DIRECTION FOR THE MONTH: Reported to the nearest tenth of a degree. Grid system used where 360 corresponds to the prime meridian. Row 51: VECTORED WIND SPEED FOR THE MONTH: Reported to the nearest tenth of a knot.