Meteorology

METEOROLOGY At a certain position, the temperature on the 300 hPa chart is -48°C; according to the tropopause chart, the tropopause is at FL 330. What is the most likely temperature at FL 350 ? 300hPa = 30,000 ft (FL300). The temperature falls at 2ºC per 1,000ft to be -54ºC at FL330, the tropopause. Above FL330 the temperature is constant. Which FL corresponds with the 200 hPa pressure level ? FL 390. 200hPa = FL390 is worth remembering. What is the approximate vertical interval which is equal to a pressure change of 1 hPa at an altitude of 5500 m ? At mean sea level 1hPa = 8m (27ft). At 5,500m (18,000ft) 1hPa = 15m (50ft) and at 12,000m (39,000ft) 1hPa = 32 m (105 FT). In order to calculate QFE from QNH, which of the following must be known ? Elevation of the airfield. QNH is QFE reduced to sea level assuming ISA conditions so to calculate QFE from QNH we only need to know field elevation. What is the dry adiabatic lapse rate ? 3ºC/1,000ft or 1ºC/100m. A layer is conditionally unstable if the air... Is unstable for saturated air and stable for dry air. a ir. Lapse rate between 1.8ºC and 3ºC per 1,000ft. A parcel of unsaturated air is lifted to just below the condensation level and then returned to its original level. What is the final temperature of the parcel of air? The same as the starting temperature. It goes up cooling at the DALR and comes down warming at the DALR . What is the effect of a strong low level inversion ? It promotes vertical windshear. An inversion means very stable conditions and, therefore, poor  visibility.. However, it does produce wind shear between different visibility different levels. The temperature at FL 140 is -12°C. What will the temperature be at FL 110 if the ICAO standard lapse rate is applied ? -6oC. FL140 = -12ºC 3 x 2ºC/1,000ft + 6ºC FL110 = -6ºC. If atmospheric conditions exist such that the temperature deviation is ISA +10°C in the lower  troposphere up to 18000 FT, FT, what is the actual layer thickness between FL 60 and FL 120 ? 6240FT The difference between the 6,000ft pressure ‘depth’ and the depth of a standard atmosphere will be 4ft per 1,000ft per per ºC deviation = 4 x 6 x 10 = 240ft. The actual depth of the layer between FL60 and FL120 = 6,000 + 240 = 6,240ft. Which of the following is a common cause of ground or surface temperature inversion ? Terrestrial radiation on a clear night with no or very light winds. It gets cold near the surface and stays warm above. This is a temperature temperature inversion. inversion.

How does the height of the tropopause normally vary with latitude in the northern hemisphere ? It decreases from south to north. The tropopause is higher over the equator and lower over the Poles. What, approximately, is the average height of the tropopause over the equator ? 16KM. The average height of the tropopause across the globe is 11km; lower at the poles and higher at the equator, but 40km is far too high. In which layer is most of the atmospheric humidity concentrated ? Troposphere. Higher, colder air holds little moisture. At FL 180, the air temperature is -35°C.The air density at this level is: Greater than the density of the ISA at FL180. At FL180 in a standard atmosphere, the temperature is (+15 – 2x18) = -21ºC. If the temperature is colder than ISA, the air will be denser than ISA. Under what condition does pressure altitude have the same value as density altitude ? At standard temperature. Density altitude is only the same as pressure altitude in standard atmosphere conditions. In the troposphere the decrease in pressure per 100 m increase in height is: Larger in the lower layers than in the higher layers. The rate of change of pressure is not linear, it is logarithmic. It is much greater near the surface than at altitude. It is about 27ft/hPa at sea level but 110ft/hPa at 40,000ft. In temperate latitudes what weather conditions may be expected over land during the summer in the centre of a stationary high pressure zone ? Calm winds, haze. High pressure is associated with stable air; no significant cloud, no cumulus, light winds and poor visibility. At what time of the year, are the paths of north Atlantic lows moving from west to east generally at their most southerly position? Winter. “Florida to Folkstone” in the winter and “Newfoundland to Norway” in the summer. What is the relationship between visibility and RVR in homogeneous fog? The visibility is generally less than the RVR.