Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
ATOC 4720 class21 • Clouds and storms 1. The air-mass thunderstorm 2. Severe storms Cirrus clouds Cirrostratus: halos A question from Tom: atmospheric stability IMPORTANT: : conditionally unstable Dry lapse rate and T profile [Derive on the blackboard] Saturation lapse rate and T profile Height (z) Archimedes’ principle: Td Ts Tobs FB FG Acceleration of air parcel Temperature (T) 1. The air mass thunderstorm:isolated Air mass thunderstorm character Isolated thunderstorm; Occurs in warm and humid regions: tropics and warm marine air-masses drift to middle latitude (say,air from the Gulf Stream); Life cycle: Self destructing mechanism-downdraft counteracts updraft; Weak or no vertical shear in winds; 2. Severe thunderstorms Occur only in convectively unstable situation; Considerable vertical shear; Downdraft reinforce updraft; Squall lines; multicell storms, supercell storms Squall lines Squall lines • Individual cumulonimbus towers (close to each other) are often arranged in long lines; gusty surface winds--squall lines; • Often occur in summer: West Africa, south of the Sahara, and mid-latitude lands, including central and eastern US; Squall lines Conditions, structure, and development: Vertical wind shear; Convectively unstable; Moves with a speed of winds in middle troposphere: so it takes Over the air in the prestorm environment at low levels, while it acts as a massive, slow-moving obstacle to The winds in the upper troposphere; Structure: see figure: downdraft formation, Anvil formation, Mamma; Updraft and downdraft reinforce each other; Surface wind gust 25m/s; Right-moving multicell storms Supercell thunderstorm Hails Tornado