4.3.2.3.3.3 In meteorological reports disseminated beyond the aerodrome, the averaging period for RVR shall be 10 minutes and:
a) only the value representative of the touchdown zone shall be given, and no indication of location on the runway shall be included;
b) when there is more than one runway available for landing, touchdown zone runway visual range values shall be included for all such runways, up to a maximum of four, and the runways to which the values refer shall be indicated, e.g. RVR RWY 26 500M RVR RWY 20 800M;
c) when the runway visual range values during the 10-minute period immediately preceding the observation have shown a distinct tendency, such that the mean during the first 5 minutes varies by 100 m or more from the mean during the second 5 minutes of the period, this shall be indicated by the abbreviation “U” for an upward tendency and by the abbreviation “D” for the downward tendency, e.g. RVR RWY 12 300M/D;
d) when the fluctuations of the runway visual range during the 10-minute period immediately preceding the observation have shown no distinct tendency, this shall be indicated by the abbreviation “N”;
e) when the one-minute runway visual range values during the 10-minute period immediately preceding the observation vary from the mean value by more than 50 m or more than 20 per cent of the mean value, whichever is the greater, the one-minute mean minimum and the one-minute mean maximum values shall be included instead of the 10-minute mean value,
e.g. RVR RWY 18 MNM700M MAX1100M.
4.3.2.3.4 Present weather
4.3.2.3.4.1 The types of the present weather phenomena shall be given in meteorological reports in terms of drizzle, rain, snow, snow grains, ice pellets, ice crystals (diamond dust), hail, small hail and/or snow pellets, fog, mist, sand, dust (widespread), haze, smoke, volcanic ash, dust/sand whirls (dust devils), squall, funnel cloud (tornado or waterspout), dust storm and sand storm.
4.3.2.3.4.2 The following characteristics of the present weather phenomena shall be given, as appropriate, in connection with the types listed in 4.3.2.3.4.1: thunderstorm, shower, freezing, blowing, low drifting, shallow, patches and partial.
4.3.2.3.4.3 The relevant intensity (light, moderate, heavy) or, as appropriate, the proximity to the aerodrome (vicinity) of the reported present weather phenomena shall be given.
4.3.2.3.5 Amount and height of base of low cloud
Cloud amount using FEW (1-2 oktas), SCT (3-4 oktas), BKN (5-7 oktas) or OVC (8 oktas), type (only if cumulonimbus (CB) or towering cumulus (TCU)) and height of base in metres (feet) shall be given in that order. If the base of the lowest cloud is diffuse or ragged or fluctuating rapidly, the minimum height of the cloud or cloud fragments shall be given together with an appropriate description of the characteristics thereof. If there are no clouds and no restriction on vertical visibility, and the abbreviation CAVOK is not appropriate, SKC shall be used. When the sky is obscured and information on vertical visibility is available, it shall be given as VER VIS, followed by the value of the vertical visibility. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：Rules of the Air and Air Traffic Services(110)
