10.12 Meteorological data - *.met The Carlsberg Automatic Meridian Circle carried out regular meteorological observations in the period 13 May 1984 to 27 May 1998 and the records are more or less continuous in that period. The devices used to measure temperature, pressure, humidity, wind speed and direction are as follows: Temperature Analog Devices AD590K Range: -55 deg C to +150 deg C Calibrated accuracy: 0.1 deg C Situation: mast head; 6 metres above ground until 1991 May 16, then 10.5 metres above ground Pressure Ysi Sostman, 2014-19.2/25.7 HA-3-WH aneroid type barometer Range: 650-870 mb Resolution: 0.1 mm Hg Hysteresis: 0.1 mm Hg Situation: inside telescope enclosure (started 1 August 1984) Humidity Lambrecht KG, type 800 N 100 hair hygrometer Range: 0-100% relative humidity Resolution: 2% Situation: inside the telescope enclosure until 1987 October 17 when it was moved to the outside north-facing wall of the telescope enclosure Wind speed From 1984 May: Malling, system 881.01 and 875 anemometer Range: 0-30 m/s Accuracy: 1 m/s From 1988 January: Vaisala WAA 12 anemometer Range: 0-75 m/s Accuracy: +/- 1% below 20 m/s; +/- 2% above 20 m/s Situation: mast head; 6 metres above ground until 1991 May 16, then 10.5 metres above ground NB: Until December 1994, wind speed averaged over several seconds and therefore insensitive to sudden gusts Wind direction Aanderaa, model 2053 (vane type) Range: 0 deg - 360 deg Accuracy: 5 deg Situation: mast head; 6 metres above ground until 1991 May 16, then 10.5 metres above ground For the years 1984, 1985 and 1986 meteorological readings are only available at 30 minute intervals. From 1987 January, the meteorological sensors were read automatically by a dedicated Olivetti PC. Readings were then made at 5 minute intervals throughout the day and night regardless of whether observing was in progress. Beginning in 1994 December, all readings were made at 20 s intervals and then averaged over 5 minutes. The 5-min averages of wind velocity are thus less prone to erratic fluctuations caused by gusts than single readings at 5 minute intervals. No readings were available when any one of the computers was "down", or a sensor became faulty, or during periods of routine maintenance or when the telescope was being modified - for example when fitting the new micrometer or the new circle reading system etc. In particular, there are no meteorological data for the following periods: 1984 September 25 to October 8: data were inadvertently deleted from the computer file 1985 December 9 to December 31: technical fault 1986 January 1 to January 11: telescope out of operation due to technical fault 1986 March: no wind direction data because the transducer was broken by heavy icing 1986 September 12 to September 22: telescope out of action due to technical fault 1986 December 18 to December 31: telescope was closed down for this period 1988 February: breaks in the data due to the fitting of the new micrometer 1988 May to August 10: no wind direction values between north and north-east because direction indicator was faulty 1994 January: gaps in the data because some of the sensors broke free from the top of the meteorological mast due to severe icing and strong winds 1995 April: gaps in the meteorological data because a new telescope control system was installed and operation was restricted 1995 September 14 to 1995 November 16: no wind direction values due to a fault in the wind direction device 1995 November 16 to 1996 March 7: A/D converter produced `noisy' background. The meteorological data are given in 26 six-monthly files. The number of records in each file is as follows: 1984 Jun-Dec 3541 1985 Jan-Dec 5974 1986 Jan-Dec 7285 1987 Jan-Jun 47349 1987 Jul-Dec 45810 1988 Jan-Jun 50637 1988 Jul-Dec 46556 1989 Jan-Jun 50672 1989 Jul-Dec 51706 1990 Jan-Jun 51974 1990 Jul-Dec 49363 1991 Jan-Jun 50008 1991 Jul-Dec 49571 1992 Jan-Jun 51884 1992 Jul-Dec 51606 1993 Jan-Jun 50622 1993 Jul-Dec 52740 1994 Jan-Jun 50640 1994 Jul-Dec 51173 1995 Jan-Jun 49121 1995 Jul-Dec 53010 1996 Jan-Jun 50989 1996 Jul-Dec 49001 1997 Jan-Jun 50548 1997 Jul-Dec 51899 1998 Jan-May 42033 Format of meteorological data record Record length = 60 char Format Quantity 1X I4 Year 1X I2 Month 1X I2 Day 1X I2 Hours UT 1X I2 Minutes UT 1X I2 Seconds UT 2X F5.1 Pressure in millibars 2X F6.1 Outdoor temperature in deg C 2X I2 Wind speed in metres/second 1X I3 Wind direction: North is 0 deg; East is 90 deg 1X I3 Percentage relative humidity: measured inside the dome until 17 October 1987; outdoors thereafter 1X F6.1 Temperature inside the dome in deg C 1X 5I1 Acceptance flags for pressure, temperature, humidity, wind speed and wind direction: if 0 - reading ignored if 1 - reading accepted if temperature flag set to 2, then temperature is the indoor temperature as the outside value was unacceptable Inside temperature and acceptance flags are not available for the period June 1984 to December 1986.