時(shí)間：2011-04-18 00:50來源：藍(lán)天飛行翻譯 作者：航空 點(diǎn)擊：次
|
b.Pilots usually report height values above MSL, since they determine heights by the altimeter. This is taken in account when disseminating and otherwise applying information received from pilots. (“Ceil-ing” heights are always above ground level.) In reports disseminated as PIREPs, height references are given the same as received from pilots, that is, above MSL. c.In area forecasts or inflight advisories, ceilings are denoted by the contraction “CIG” when used with sky cover symbols as in “LWRG TO CIG OVC005,” or the contraction “AGL” after, the forecast cloud height value. When the cloud base is given in height above MSL, it is so indicated by the contraction “MSL” or “ASL” following the height value. The heights of clouds tops, freezing level, icing, and turbulence are always given in heights above ASL or MSL. 7.1.17. Reporting Prevailing Visibility a. Surface (horizontal) visibility is reported in METAR reports in terms of statute miles and 3/5/3/1/ increments thereof; e.g., 1/16, 1/8, 16, 1/4, 16, 8, 2, 5/8, 3/4, 7/8, 1, 1 1/8, etc. (Visibility reported by an unaugmented automated site is reported differently than in a manual report, i.e., ASOS: 0, 1/16, 1/8, 1/4, 1/2, 3/4, 1, 1 1/4, 1 1/2, 1 3/4, 2, 2 1/2, 3, 4, 5, etc., AWOS: M1/4, 1/4, 1/2, 3/4, 1, 1 1/4, 1 1/2, 1 3/4, 2, 2 1/2, 3, 4, 5, etc.) Visibility is determined through the ability to see and identify preselected and prominent objects at a known distance from the usual point of observation. Visibilities which are determined to be less than 7 miles, identify the obscuring atmospheric condi-tion; e.g., fog, haze, smoke, etc., or combinations thereof. b.Prevailing visibility is the greatest visibility equalled or exceeded throughout at least one half of the horizon circle, not necessarily contiguous. Segments of the horizon circle which may have a significantly different visibility may be reported in the remarks section of the weather report; i.e., the southeastern quadrant of the horizon circle may be determined to be 2 miles in mist while the remaining quadrants are determined to be 3 miles in mist. c.When the prevailing visibility at the usual point of observation, or at the tower level, is less than 4 miles, certificated tower personnel will take visibility observations in addition to those taken at the usual point of observation. The lower of these two values will be used as the prevailing visibility for aircraft operations. 7.1.18. Estimating Intensity of Rain and Ice Pellets a. Rain 1.Light. From scattered drops that, regardless of duration, do not completely wet an exposed surface up to a condition where individual drops are easily seen. 2.Moderate. Individual drops are not clearly identifiable; spray is observable just above pave-ments and other hard surfaces. 3.Heavy. Rain seemingly falls in sheets; individual drops are not identifiable; heavy spray to height of several inches is observed over hard surfaces. b. Ice Pellets 1.Light. Scattered pellets that do not com-pletely cover an exposed surface regardless of duration. Visibility is not affected. 2.Moderate. Slow accumulation on ground. Visibility reduced by ice pellets to less than 7 statute miles. 3.Heavy. Rapid accumulation on ground. Visibility reduced by ice pellets to less than 3 statute miles. 7.1.40 Meteorology 7.1.19. Estimating Intensity of Snow or Drizzle (Based on Visibility)a. Light. Visibility more than 1/2 statute mile. b. Moderate. Visibility from more than 1/4 stat-ute mile to 1/2 statute mile. c. Heavy. Visibility 1/4 statute mile or less. 7.1.20. Pilot Weather Reports (PIREPs)a.FAA air traffic facilities are required to solicit PIREPs when the following conditions are reported or forecast: ceilings at or below 5,000 feet; visibility at or below 5 miles (surface or aloft); thunderstorms and related phenomena; icing of light degree or greater; turbulence of moderate degree or greater; wind shear and reported or forecast volcanic ash clouds. b.Pilots are urged to cooperate and promptly volunteer reports of these conditions and other atmospheric data such as: cloud bases, tops and layers; flight visibility; precipitation; visibility restrictions such as haze, smoke and dust; wind at altitude; and temperature aloft. c.PIREPs should be given to the ground facility with which communications are established; i.e., EFAS, AFSS/FSS, ARTCC, or terminal ATC. One of the primary duties of EFAS facilities, radio call “FLIGHT WATCH,” is to serve as a collection point for the exchange of PIREPs with en route aircraft. d.If pilots are not able to make PIREPs by radio, reporting upon landing of the inflight conditions encountered to the nearest AFSS/FSS or Weather Forecast Office will be helpful. Some of the uses made of the reports are: AIM 1.The ATCT uses the reports to expedite the flow of air traffic in the vicinity of the field and for hazardous weather avoidance procedures. 2.The AFSS/FSS uses the reports to brief other pilots, to provide inflight advisories, and weather avoidance information to en route aircraft. 3.The ARTCC uses the reports to expedite the flow of en route traffic, to determine most favorable altitudes, and to issue hazardous weather information within the center’s area. 4.The NWS uses the reports to verify or amend conditions contained in aviation forecast and advisories. In some cases, pilot reports of hazardous conditions are the triggering mechanism for the issuance of advisories. They also use the reports for pilot weather briefings. 5.The NWS, other government organizations, the military, and private industry groups use PIREPs for research activities in the study of meteorological phenomena. 6.All air traffic facilities and the NWS forward the reports received from pilots into the weather distribution system to assure the information is made available to all pilots and other interested parties. |
