Activity #1 Can precipitation begin as rain, turn into ice pellets and hit the Earth as freezing rain? Why or why not? What are some other combinations of precipitation that can occur during a water droplet?s fall to Earth?     Activity #2: Freezing Rain and Ice Storms The radiosonde data (Eastern Ontario Southern Quebec) are representative of the atmospheric conditions during the January 1998 ice storm. Plot the values on the accompanying graph. Place a dot (?) to show temperature at a particular altitude. Use a cross (x) to show the dew point at the same height. If the temperature and dew point values are the same, draw a small circle around the dot.   After plotting all the data, connect adjacent temperature values with solid straight lines to show the temperature pattern with altitude, and use dashed straight lines for adjacent dew point values. The combination of temperature and humidity patterns that results is termed a 'sounding'. It depicts atmospheric conditions in the atmosphere above the reporting station at the time the data were collected.   Use the graph with plotted data to answer the following questions: 1. Were there clouds above the area when these data were collected? What assumption must you make in interpreting the data to answer this question? (Refer back to the Introduction section if you need help answering this). 2. Locate the top and bottom of any existing cloud layer. Draw on the graph horizontal lines that cut across the sounding at the highest and lowest points at which saturated air was reported, i.e., temperature and dew-point values were the same. Since precipitation typically falls from relatively thick layers of cloud at least a few hundred metres thick, were the clouds thick enough to produce precipitation? 3. Shade lightly with your pencil the area enclosed by the vertical 0-degree line on the graph and that part of the plotted sounding showing temperatures of 0 degrees and higher. This shading highlights a layer of air in which temperatures are above freezing. Label the layer, 'WARM'. Describe in your own words the conditions above the area in terms of layers of air with above-freezing and freezing temperatures. 4. Assume that precipitation was occurring and that it originated as ice particles in the upper reaches of the existing cloud layer. What will prevent these particles from reaching ground level as snow? 5. For freezing rain to occur as it was in Eastern Ontario at the time of observation, raindrops must fall through a relatively shallow layer of freezing air immediately above the Earth's surface. According to the table of data given to you, how thick was this layer above Eastern Ontario ?       The slope of a cold front is steeper than that of a warm front because of the friction between the cold air and the surface.