20. normally, a parcel of air warmer than the surrounding air; conversely, the air parcel will surrounding air if it is cooler than the remains stationary, sinks b. a. rises, remains stationary sinks, rise rises, sink c. d. 21. microscopic particles, such as dust particles and sea salt crystals, are known as as "landing pads" on which water vapor can condense that serve ice cyrstals b. a. condensation nuclei supercooled water droplets d. c. water droplets 22. tiny particles present in the atmosphere so small and light that the slightest movements of air keep then aloft are called eg soot, salt particles a. clouds b. aerosols c. cirmus d. convection 23. absorption and downward movement of precipitation into the soil is called a. infiltration b. runoff c. snowfall d. evaporation 24. the realm of water in all its forms, and the flows of water among ocean land and atmosphere are known collectively as a. hydrosphere b. lithosphere c. biosphere 25. motion of a surface layer ground surface when the infiltration rate is exceeded by the precipitation rate; a form of run off of water over a sloping a. snowfall b. evaporation c. overland flow d. infiltration