NOTES FOR DC02D COMPLETED ON 26/09/2006 ____________________________________________________________________________________________ ____________________________________________________________________________________________ DATA FILE Byte Location , Byte Size , Explanation -------------------------------------------------------------------------------------------- 1-2 ,2 , Record identifier - dc 4-9 ,6 , Bureau of Meteorology Station Number. 11-50 ,40 , Station Name. 52-61 ,10 , Year month day in YYYY,MM,DD format. 63-71 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 0000 hours Solar Time in kWh.m-2. 73-81 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 0000 hours Solar Time in kWh.m-2. 83-91 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 0030 hours Solar Time in kWh.m-2. 93-101 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 0030 hours Solar Time in kWh.m-2. 103-111 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 0100 hours Solar Time in kWh.m-2. 113-121 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 0100 hours Solar Time in kWh.m-2. 123-131 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 0130 hours Solar Time in kWh.m-2. 133-141 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 0130 hours Solar Time in kWh.m-2. 143-151 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 0200 hours Solar Time in kWh.m-2. 153-161 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 0200 hours Solar Time in kWh.m-2. 163-171 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 0230 hours Solar Time in kWh.m-2. 173-181 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 0230 hours Solar Time in kWh.m-2. 183-191 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 0300 hours Solar Time in kWh.m-2. 193-201 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 0300 hours Solar Time in kWh.m-2. 203-211 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 0330 hours Solar Time in kWh.m-2. 213-221 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 0330 hours Solar Time in kWh.m-2. 223-231 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 0400 hours Solar Time in kWh.m-2. 233-241 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 0400 hours Solar Time in kWh.m-2. 243-251 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 0430 hours Solar Time in kWh.m-2. 253-261 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 0430 hours Solar Time in kWh.m-2. 263-271 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 0500 hours Solar Time in kWh.m-2. 273-281 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 0500 hours Solar Time in kWh.m-2. 283-291 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 0530 hours Solar Time in kWh.m-2. 293-301 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 0530 hours Solar Time in kWh.m-2. 303-311 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 0600 hours Solar Time in kWh.m-2. 313-321 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 0600 hours Solar Time in kWh.m-2. 323-331 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 0630 hours Solar Time in kWh.m-2. 333-341 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 0630 hours Solar Time in kWh.m-2. 343-351 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 0700 hours Solar Time in kWh.m-2. 353-361 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 0700 hours Solar Time in kWh.m-2. 363-371 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 0730 hours Solar Time in kWh.m-2. 373-381 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 0730 hours Solar Time in kWh.m-2. 383-391 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 0800 hours Solar Time in kWh.m-2. 393-401 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 0800 hours Solar Time in kWh.m-2. 403-411 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 0830 hours Solar Time in kWh.m-2. 413-421 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 0830 hours Solar Time in kWh.m-2. 423-431 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 0900 hours Solar Time in kWh.m-2. 433-441 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 0900 hours Solar Time in kWh.m-2. 443-451 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 0930 hours Solar Time in kWh.m-2. 453-461 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 0930 hours Solar Time in kWh.m-2. 463-471 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 1000 hours Solar Time in kWh.m-2. 473-481 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 1000 hours Solar Time in kWh.m-2. 483-491 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 1030 hours Solar Time in kWh.m-2. 493-501 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 1030 hours Solar Time in kWh.m-2. 503-511 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 1100 hours Solar Time in kWh.m-2. 513-521 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 1100 hours Solar Time in kWh.m-2. 523-531 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 1130 hours Solar Time in kWh.m-2. 533-541 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 1130 hours Solar Time in kWh.m-2. 543-551 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 1200 hours Solar Time in kWh.m-2. 553-561 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 1200 hours Solar Time in kWh.m-2. 563-571 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 1230 hours Solar Time in kWh.m-2. 573-581 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 1230 hours Solar Time in kWh.m-2. 583-591 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 1300 hours Solar Time in kWh.m-2. 593-601 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 1300 hours Solar Time in kWh.m-2. 603-611 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 1330 hours Solar Time in kWh.m-2. 613-621 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 1330 hours Solar Time in kWh.m-2. 623-631 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 1400 hours Solar Time in kWh.m-2. 633-641 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 1400 hours Solar Time in kWh.m-2. 643-651 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 1430 hours Solar Time in kWh.m-2. 653-661 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 1430 hours Solar Time in kWh.m-2. 663-671 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 1500 hours Solar Time in kWh.m-2. 673-681 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 1500 hours Solar Time in kWh.m-2. 683-691 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 1530 hours Solar Time in kWh.m-2. 693-701 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 1530 hours Solar Time in kWh.m-2. 703-711 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 1600 hours Solar Time in kWh.m-2. 713-721 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 1600 hours Solar Time in kWh.m-2. 723-731 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 1630 hours Solar Time in kWh.m-2. 733-741 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 1630 hours Solar Time in kWh.m-2. 743-751 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 1700 hours Solar Time in kWh.m-2. 753-761 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 1700 hours Solar Time in kWh.m-2. 763-771 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 1730 hours Solar Time in kWh.m-2. 773-781 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 1730 hours Solar Time in kWh.m-2. 783-791 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 1800 hours Solar Time in kWh.m-2. 793-801 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 1800 hours Solar Time in kWh.m-2. 803-811 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 1830 hours Solar Time in kWh.m-2. 813-821 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 1830 hours Solar Time in kWh.m-2. 823-831 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 1900 hours Solar Time in kWh.m-2. 833-841 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 1900 hours Solar Time in kWh.m-2. 843-851 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 1930 hours Solar Time in kWh.m-2. 853-861 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 1930 hours Solar Time in kWh.m-2. 863-871 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 2000 hours Solar Time in kWh.m-2. 873-881 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 2000 hours Solar Time in kWh.m-2. 883-891 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 2030 hours Solar Time in kWh.m-2. 893-901 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 2030 hours Solar Time in kWh.m-2. 903-911 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 2100 hours Solar Time in kWh.m-2. 913-921 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 2100 hours Solar Time in kWh.m-2. 923-931 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 2130 hours Solar Time in kWh.m-2. 933-941 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 2130 hours Solar Time in kWh.m-2. 943-951 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 2200 hours Solar Time in kWh.m-2. 953-961 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 2200 hours Solar Time in kWh.m-2. 963-971 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 2230 hours Solar Time in kWh.m-2. 973-981 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 2230 hours Solar Time in kWh.m-2. 983-991 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 2300 hours Solar Time in kWh.m-2. 993-1001 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 2300 hours Solar Time in kWh.m-2. 1003-1011 ,9 , *--- Direct solar exposure on a horizontal surface for the half-hour ending 2330 hours Solar Time in kWh.m-2. 1013-1021 ,9 , *--- Uncertainty of direct solar exposure on a horizontal surface for the half-hour ending 2330 hours Solar Time in kWh.m-2. 1023 ,1 , # symbol, end of record indicator. ACCUMULATED REPORTS ___________________ Daily elements are reported at 9am, however many Australian observers do not report over a weekend or holiday. In this case they may accumulate rainfall and other elements such as maximum temperature. Thus the rainfall total reported on a Monday morning may be the total since the previous Friday, not just for the last 24 hours. Similarly, the maximum temperature may be the highest over a period of 2 or 3 days. Where this happens, the 'days of accumulation' field gives the number of days involved. * QUALITY FLAG DESCRIPTIONS ___________________________ Y: quality controlled and acceptable N: not quality controlled W: quality controlled and considered wrong S: quality controlled and considered suspect I: quality controlled and inconsistent with other known information X: no quality information available *--- RADIATION ______________ Radiation quantities are generally expressed in terms of either irradiance or radiant exposure. Irradiance is a measure of the rate of energy received per unit area, and has SI units of Watts per square metre (W.m-2), where 1 Watt (W) is equal to 1 Joule (J) per second. Radiant exposure is a time integral (or sum) of irradiance. Thus a 1-minute radiant exposure is a measure of the energy received per square metre over a period of 1 minute. Therefore a 1 minute radiant exposure = mean irradiance (W.m-2) x 60 (s), and has units of Joules per square metre (J.m-2). A half-hour radiant exposure would then be the sum of 30 one-minute (or 1800 one second) radiant exposures. For example: a mean irradiance of 500 W.m-2 over 1 minute yields a radiant exposure of 30000 J.m-2 or 30 kJ.m-2. Measurements of surface-based radiation are made according to Solar Time. Solar time is different to local time and is based on the idea that when the sun reaches its highest point in the sky, it is noon.(http://en.wikipedia.org/wiki/Solar_time). Current data are measured according to True Solar Time (according to the actual motion of the Sun), while historic data used Mean Solar Time (an approximation of the motion of the Sun that can vary as much as 16 minutes). A solar position calculator can be found at http://www.srrb.noaa.gov/highlights/sunrise/azel.html Solar radiation definitions can be found at http://www.bom.gov.au/sat/glossary.shtml Uncertainties are used instead of quality flags with the exception of satellite derived data. When using data that is a combination of network and satellite data ignore quality flags where uncertainties exist. Uncertainties are in the same units as the data values. GLOBAL SOLAR EXPOSURE Global solar exposure is the total amount of solar energy falling on a horizontal surface of unit area. The daily global solar exposure is the total solar energy for a day. Typical values for daily global solar exposure range 1 to 35 MJ/m2 (megajoules per square metre). The values are usually highest in clear sky conditions during the summer, and lowest during winter or very cloudy days.Combination refers to satellite derived data being used where ground network data is not available. If ground network data is available then this is provided, otherwise where possible satellite derived data is given instead. SATELLITE DERIVED SOLAR EXPOSURE DATA Global solar exposure data is not measured at the site. Instead, it is derived from satellite data for the co-ordinates at which the station is currently located. Accuracies of Satellite Estimates: The satellite method of determining radiant exposure from visible images from GMS5 was tested using pyranometer data from 9 network sites from July and August 1997. On average the model agreed with the measurements to within 0.17% (around 40 kJ.m-2 on a typical clear day) and the majority of measurements agreed within 6% (around 1500 kJ.m-2 on a typical clear day). The satellite method tends to over estimate the radiant exposure in wet, cloudy conditions and to under estimate it in dry conditions. To put these numbers into perspective, we can imagine using the measured global solar radiant exposure at a pyranometer location to estimate the global solar radiant exposure at a point some distance away. The accuracy of the estimation will decrease as we move away from the radiation station. The further we go, the less reliable the estimate will be. In a typical agricultural area such as that around Wagga Wagga, the satellite becomes more accurate than using surface station values at a distance typically 40 km from a pyranometer. Solar exposure data is derived from satellite imagery processed by the Bureau of Meteorology from the Geostationary Meteorological Satellite GMS-5 of the Japan Meteorological Agency. DIFFUSE SOLAR EXPOSURE Diffuse solar exposure is the total amount of solar energy falling on a horizontal surface from all parts of the sky apart from the direct sun. The daily diffuse solar exposure is the total diffuse solar energy for this period. Typical values for daily diffuse solar exposure range from 1000 to 20000 kJ.m-2 (kilo-Joule per metres squared). The values are usually highest during cloudy conditions, and lowest during clear sky days. The diffuse exposure is always less than or equal to the global exposures for the same period. DIRECT SOLAR EXPOSURE Direct solar exposure is the total amount of solar energy arriving at the Earth's surface from the Sun's direct beam, on a plane perpendicular to the beam, and is usually measured by pyrheliometer mounted on a solar tracker. The tracker ensures that the Sun's beam is always directed into the instruments field of view during the day. The pyrheliometer has a field of view of 5. In order to use this measurement for comparison with global and diffuse global exposures irradiances, it is necessary to obtain the horizontal component of the direct solar exposure irradiance. This is achieved by multiplying the direct solar exposure irradiance by the cosine of the Sun's zenith angle. DOWNWARD INFRA-RED (TERRESTRIAL) IRRADIANCE All matter with a temperature greater than 0 K (Kelvin) emits electromagnetic energy; the amount of energy and wavelengths at which the energy is emitted are dependent on the temperature of the body. The higher the temperature of the body, the greater the magnitude of the energy radiated and the shorter the wavelengths at which that peak energy is radiated. A body will radiate energy over a range of wavelengths, called the body's radiation spectrum (a subset of the complete electromagnetic spectrum). Most of the Sun's spectrum lies in the wavelength range of 0.25 - 4.0 m, the so-called short wave range. Downward infrared irradiance is a measurement of the irradiance arriving on a horizontal plane at the Earth's surface, for wavelengths in the range 4 - 100 m (the wavelength emitted by atmospheric gasses and aerosols). It is related to a representative (or effective radiative) temperature of the Earth's atmosphere by the Stefan-Boltzmann Law: E = s T^4 Where: E = irradiance measured. [Wm^-2] s = Stefan-Boltzmann constant. [5.67 x 10^-8 Wm^-2deg^-4 ] T = representative atmospheric temperature. [K] Consequently, this quantity will continue to have a positive value, even at night time. It can be measured using an Eppley PIR pyrgeometer. As in the case of diffuse solar irradiance measurement, it is required that this instrument is shaded from the direct beam of the Sun during the day, since the Sun's beam can heat the pyrgeometer dome and contribute to error in the measurement. Accordingly, the pyrgeometer is mounted on a tracker. The representative temperature is dependent on a number of factors, but typically larger values are recorded when middle to low level clouds cover the sky than those recorded during clear sky episodes. Time base used : Solar GAPS AND MISSING DATA _____________________ Very few sites have a complete unbroken record of climate information. A site may have been closed, reopened, upgraded to a full weather site or downgraded to a rainfall only site during its existence causing breaks in the record for some or all elements. Some gaps may be for one element due to a damaged instrument, others may be for all elements due to the absence or illness of an observer. INSTUMENTS AND OBSERVATIONAL PRACTICES ______________________________________ Historically a nearby site (within about 1 mile in earlier days) may have used the same site number. There may have been changes in instrumentation and/or observing practices over the period included in a dataset, which may have an effect on the long-term record. In recent years many sites have had observers replaced by Automatic Weather Stations, either completely or at certain times of the day. TIME ____ For a part of the year some Australian States adopt Daylight Savings Time (DST), and observers continue to take observations according to the local clock. Times provided with this data are Local Time, unless otherwise noted. Care needs to be taken when comparing values from year to year or month to month, because for some elements the effect of one hour can be marked, for example air temperature often rises sharply between 8am and 9am. Daylight Savings has been used in many Australian states since 1973. The changeovers occur almost always in October and March, but exact dates vary from State to State and year to year. More information can be found at: http://www.bom.gov.au/climate/averages/tables/daysavtm.shtml ROUNDING ________ The primary way of sending current weather information around the world is via a coded message known as a SYNOP. This message only allows some measurements to be sent as rounded values. Once manuscript records have been sent in many of these values are typed in with greater precision (normally to one decimal place). This usually occurs within a few months. If consecutive values all have a zero in the decimal place, then it is almost certain that rounding was used earlier. A new type of message format is progressively being introduced to overcome this situation. COPYRIGHT _________ The copyright for any data is held in the Commonwealth of Australia and the purchaser shall give acknowledgement of the source in reference to the data. Apart from dealings under the copyright Act, 1968, the purchaser shall not reproduce, modify or supply (by sale or otherwise) these data without written permission. Enquiries should be made in the first instance to the National Climate Centre, Bureau of Meteorology, PO Box 1289K, Melbourne 3001, marked to the attention of SRDS. LIABILITY _________ While every effort is made to supply the best data available this may not be possible in all cases. We do not give any warranty, nor accept any liability in relation to the information given, except that liability (if any), that is required by law. IF DATA IS NOT AS REQUESTED ___________________________ If the data provided are not as requested, the data will be repeated at no extra cost, provided that: a) the Bureau is notified within 60 days. b) the printout/disc/data file is returned to the Bureau for checking. c) there has been a fault or error in providing the data. Where there has been no fault or error of provision, the cost involved in requested corrective action such as resending the data or providing alternative sites will be charged for as necessary. ____________________________________________________________________________________________ ____________________________________________________________________________________________ SITE DETAILS FILE This file contains the details for the current site or are those which applied when the site was closed. Many sites have been moved, downgraded, upgraded etc over the years. Byte Location , Byte Size , Explanation -------------------------------------------------------------------------------------------- 1-2 ,2 , Record identifier - st 4-9 ,6 , Bureau of Meteorology Station Number. 11-14 ,4 , Rainfall district code 16-55 ,40 , Station Name. 57-63 ,7 , Month/Year site opened. (MM/YYYY) 65-71 ,7 , Month/Year site closed. (MM/YYYY) 73-80 ,8 , Latitude to 4 decimal places, in decimal degrees. 82-90 ,9 , Longitude to 4 decimal places, in decimal degrees. 92-106 ,15 , Method by which latitude/longitude was derived. 108-110 ,3 , State. 112-117 ,6 , Height of station above mean sea level in metres. 119-124 ,6 , Height of barometer above mean sea level in metres. 126-130 ,5 , WMO (World Meteorological Organisation) Index Number. 132-135 ,4 , First year of data supplied in data file. 137-140 ,4 , Last year of data supplied in data file. 142-144 ,3 , Percentage complete between first and last records. 146-148 ,3 , Percentage of values with quality flag 'Y'. 150-152 ,3 , Percentage of values with quality flag 'N'. 154-156 ,3 , Percentage of values with quality flag 'W'. 158-160 ,3 , Percentage of values with quality flag 'S'. 162-164 ,3 , Percentage of values with quality flag 'I'. 166 ,1 , # symbol, end of record indicator. LATITUDES AND LONGITUDES ________________________ Latitudes and longitudes are given to 4 decimal places, but in many cases will not be accurate to 4 decimal places. This is because in the early days the positions of stations were estimated from maps. Gradually the network of open stations is being checked (and if necessary corrected) using GPS (Global Positioning System). The method used is given in the site details file. WMO INDEX NUMBER ________________ This is the number assigned to a site that makes international weather reports every day. The number is not actively used in the climate archive, and only a few hundred such numbers are assigned at any time. These are not perpetual but may be reassigned where a site no longer makes the international reports (synops); thus a particular number cannot be regarded as unique and exclusive to any particular site. PERCENTAGE INFORMATION ______________________ In some cases the percentage completeness will be overestimated. This will occur if the database has incomplete information about the element being selected. In cases where several elements are selected, rows with a least one of the elements available are considered complete. Where only a limited amount of data is available and the percentage completeness is less than 0.5%, an "*" has been used. An "*" is also used if the percentage of values with a particular quality flag is non zero and less than 0.5%.