Wind shear is a sudden, drastic shift in wind speed and/or direction that may occur at any altitude in a vertical or horizontal plane. It can subject your aircraft to sudden updrafts, downdrafts, or extreme horizontal wind components, causing loss of lift or violent changes in vertical speeds or altitude. In fact, when landing during gusty conditions, you should use a power-on approach and landing to minimize the effect of the wind and to retain positive control of the aircraft. Wind shear is associated with temperature inversions, the jet stream, thunderstorms, and frontal inversions. With a temperature inversion, it occurs when cold, calm air is near the surface and warmer air aloft is in motion. This can be a hazard during climbouts or approaches when your airspeed is relatively slow. Be alert for a sudden change in airspeed and carry an extra margin of speed if you suspect an inversion.With fronts, the most critical period is either just before or just after frontal passage. With a cold front, wind shear occurs just after the front passes and for a short time after ward. Studies indicate the amount of wind shear in a warm front is generally much greater than in a cold front. The wind shear below 5,000 ft AGL in a warm front may last for ap proximately six hours. The most critical period is before the front passes; the problem ceases to exist after it passes.A microburst is an intense, localized downdraft of brief duration which spreads out in all directions when it reaches the surface. This creates severe horizontal and vertical wind shears which pose serious hazards to aircraft, particularly those near the surface. An individual mi croburst typically covers an area of less than two and a half miles in diameter at the surface and usually lasts no longer than 15 minutes. Peak winds last two to four minutes and atten dant downdrafts can be as strong as 6,000 ft per minute.Any convective cloud can produce this phenomenon. Although microbursts are commonly associated with heavy precipitation in thunderstorms, they often occur in virga. If there is no precipitation, your only cue may be a ring of dust at the surface. If you suspect the pres ence of microbursts in your local area, delay your takeoff or landing.4.An individual microburst （ ） ．