NL10001 NL10002 NETHERLANDS NL10003 NL10004 CLIMATOLOGICAL STANDARD NORMALS (CLINO) of Dutch NL10005 climatological stations for the period 1961 - 1990 for NL10006 publication by WMO (Surface data). NL10007 NL10008 NL10009 1.INTRODUCTION. NL10010 NL10011 Data has been provided from five Dutch stations. The data NL10012 relate to the standard period for normal values 1961 - 1990. NL10013 The Standard Normals have been based on hourly surface data NL10014 and have been computed to daily, monthly and yearly values, in NL10015 accordance with WMO-publication TD/ NO. 341 of March 1989. NL10016 NL10017 NL10018 2. THE OBSERVATIONAL NETWORK. NL10019 NL10020 The five stations De Kooy (international index number 06235), NL10021 De Bilt (06260), Eelde (Groningen Airport 06280), Vlissingen NL10022 (06310) and Maastricht (Airport Zuid-Limburg 06380) are NL10023 classified as PRINCIPAL STATIONS, from which hourly NL10024 observations and measurements are present. NL10025 NL10026 The observation site of these stations has been representative NL10027 to the surrounding area, according to the WMO-Regulations. NL10028 NL10029 The geographical coordinates and other specifications of the NL10030 stations are given in the next table, giving the situation on NL10031 31 December 1990. NL10032 NL10033 TABLE I NL10034 NL10035 NO/NAME LATITUDE LONGITUDE H (M) Hz(M) NL10036 NL10037 06235 52 deg 55 min N 4 deg 47 min E + 0 + 4 NL10038 DE KOOY NL10039 NL10040 06260 52 deg 06 min N 5 deg 11 min E + 2 + 19 NL10041 DE BILT NL10042 NL10043 06280 53 deg 08 min N 6 deg 35 min E + 4 + 5 NL10044 EELDE NL10045 NL10046 06310 51 deg 27 min N 3 deg 36 min E + 8 + 13 NL10047 VLISSINGEN NL10048 NL10049 06380 50 deg 55 min N 5 deg 46 min E + 114 + 116 NL10050 MAASTRICHT NL10051 NL10052 NL10053 H = height of the observation site above MSL. NL10054 Hz= height of the barometer above MSL. NL10055 NL10056 NL10057 NL10058 3.BASIC DATA AND METHOD OF OBSERVATION. NL10059 NL10060 3.1 General remarks. NL10061 NL10062 The climatological day is defined as the period between NL10063 00.01 and 24.00 h UT. NL10064 NL10065 The climatological normals have been based on hourly surface NL10066 observations and measurements and computations have been NL10067 done to daily, monthly and yearly values. NL10068 NL10069 Most weather parameters are available during the 30-year NL10070 period 1961 - 1990, exept global radiation, evaporation and NL10071 days with special phenomena, which are available during at NL10072 least 1971 - 1990; soil temperatures have been calculated NL10073 for one station for ten years: 1981 - 1990. Snow depth NL10074 data are not present. NL10075 NL10076 NL10077 3.2 Explanation to the parameters. NL10078 NL10079 3.2.1. Atmospheric pressure. NL10080 NL10081 The hourly measurements have been reduced to Mean Sea Level NL10082 (MSL). The height of the barometer above MSL has been noted NL10083 in Table I as Hz. Measurements have been done with mercury NL10084 and (electrical) aneroid barometers. NL10085 NL10086 3.2.2. Temperature NL10087 NL10088 Air temperature. NL10089 Hourly values of air temperatures have been used for NL10090 computation of daily means. Maximum and minimum temperatures NL10091 are related to the climatological day. NL10092 Air temperatures have been measured in a Stephenson Screen: NL10093 the height of the sensors are at 1.50 M above terrain. The NL10094 sensors used are the mercury and platinum resistance NL10095 thermometers. NL10096 NL10097 Soil temperatures are present just for station De Bilt during NL10098 10 years. Measurements are made at 06, 12, 18 and 24 h UT at a NL10099 depth of 5, 10, 20, 50 and 100 cM. The instruments used are NL10100 the mercury and platinum resistance thermometers. NL10101 NL10102 3.2.3. Relative humidity. NL10103 NL10104 Hourly values of relative humidity have been calculated from NL10105 the psychrometer formula with dry and wet bulb temperatures NL10106 during the 1961-1970 period; from readings of hair hygrographs NL10107 during 1971-1980 and from measurements directly from electric NL10108 humidity sensors in the 1980- 1990 period. The measurements NL10109 are made in a screen at 1.50 M height. NL10110 NL10111 NL10112 3.2.4. Vapour pressure. NL10113 NL10114 This parameter was calculated from the relative humidity and NL10115 air temperature. NL10116 NL10117 3.2.5. Dewpoint temperature. NL10118 NL10119 The values of this parameter were calculated from other NL10120 humidity parameters and the air temperatures. NL10121 NL10122 3.2.6. Rainfall data were obtained from measurements once a NL10123 day at 8.00 h UT. The upper rim of the rain- gauges were sited NL10124 at 40 cM above the ground; the collection surface of the NL10125 funnel being 2 dm2. NL10126 NL10127 3.2.7. Evaporation has been calculated fron the Makkink NL10128 formula. Daily sums of evapotranspiration (in mm) were NL10129 obtained with daily mean temperatures and daily sums of global NL10130 radiation. Monthly and yearly normals are based on daily data. NL10131 Since global radiation is measured during less than 30 yaers, NL10132 the evapotranspiration normals are based on the analogous NL10133 number of years: at least 20. NL10134 NL10135 3.2.8. Global radiation measurements started in the 1960's. NL10136 The type of instrument being Moll-Gorczynski Pyranometer, NL10137 commonly referred to as the Kipp solarimeter. NL10138 Calibration has been done with reference to the World NL10139 Radiometric Reference (WRR). The height of the sensor above NL10140 terrain was not prescribed. NL10141 NL10142 3.2.9. Duration of sunshine (daily values). NL10143 NL10144 Hourly amounts has been read of Campbell-Stokes cards. NL10145 Adjustments were carried out with respect to the daily total. NL10146 NL10147 3.2.10. Total cloud amount (in octas) has been obtained from NL10148 hourly estimations. NL10149 Daily means are used as basis for calculations of the normals. NL10150 NL10151 3.2.11. Wind parameters has been obtained from cup anemometer NL10152 readings (hourly mean wind speed) and wind vanes measurements NL10153 (mean value of the wind direction during the last 10-minutes NL10154 of the hour). The sensors being placed at a height of 10 M NL10155 above the observation site. NL10156 Wind steadiness factor has been defined as the quotient of NL10157 vector wind speed and scalar speed. NL10158 Prevailing wind direction has been diverted from the frequency NL10159 tables of the wind direction. NL10160 NL10161 NL10162 3.2.12. Specific weather phenomena. NL10163 NL10164 These phenomena are fog, rainfall, snowfall, hail, thunder, NL10165 icing and wind with gale force. NL10166 A day is counted as a day with fog, rainfall,.......etc. if NL10167 this phenomena has been observed during at least one hour. NL10168 A day with snowfall is different from a day with snow lying. NL10169 Normals of snow lying days are not available. NL10170 NL10171 NL10172 4. Explanation to the tables. NL10173 NL10174 4.1 General. NL10175 NL10176 Daily means and daily sums are based on 24 hours, NL10177 running from 01.00 - 24.00 h UT. NL10178 NL10179 Small differences can occur between the monthly normals NL10180 summed to yearly values and the calculated yearly normal NL10181 values by the effect of rounding. NL10182 NL10183 NL10184