1. The pressure announced on last night’s television weather broadcast was 29.92. Explain how this was measured and give the units. Would this be considered an unusually large or low pressure value? A pressure announced on the weather forecast of 29.92 is an average measurement. It is measured with a barometer and in the United States the units of measure are inches of mercury, or inHg. This is what meteorologist are referring to in their forecasts. 29.92 inHg is a measurement within the normal range. This may be referred to as air pressure, atmospheric pressure or barometric pressure. They are all the same thing. Low pressure readings are associated with stormy weather and precipitation, while high pressure readings are indicated by clear and calm weather. Here is Portland, Oregon, where it rains 9 months of the year, we experience normal pressure readings of 29.92 inHg or slightly higher or lower. It only changes when we have exceptionally worse or better weather.
2. If the earth did not rotate, how would you expect winds to blow with respect to high and low pressure centers? With no earth rotation, winds would blow in straight lines. They would move from a huge high pressure region, the side in direct sunlight, to the lowest pressure region. This would be the dark side of the earth. The side the sun never touches. Cold air from the dark side would then be pulled back to the sunny side in straight lines to be warmed and then pushed back again. The dark side would be in a constant state of stormy weather, while the sun side would experience beautiful clear, calm, sunny days. If it didn’t get cooked by the sun, that is.
3. If the pressure gradient force remained the same but the earth’s rate of rotation decreased slightly, would you expect the speed of the geostrophic wind to increase, decrease or remain about the same? If pressure gradient winds remained the same but the earth’s rotation slowed geostrophic winds would increase. The Coriolis force is a force based on the earth’s rotation. Because the earth spins objects in the atmosphere do not move in straight lines. The earth’s rotation causes them to veer of course. This is the CF. Pressure gradient winds (PGF) along with CF balance out geostrophic winds. If the earth slowed, the CF would decrease, so geostrophic winds would have to increase to maintain this balance.
4. Explain why it is much more difficult to measure snowfall amount than rainfall amount. Rain is measured by the amount of liquid contained in the measurement device. Whatever is amount of liquid is in the device, is the measurement. However snow, has various factors that can impact its measurement. First of all snowfall measurement is based on how much liquid there would be if the snow was melted into liquid form. There are several factors that can impact how much snow is measured in a device. Wind can move snow from high points to low points and vice versa. The surface on which the snow is falling onto can also impact a measurement. The length of time the snow has been on the ground and how compact it is can also effect measurements. Measuring in several places and then using an average can give a more accurate total. Meteorologists usually forecast snow amounts giving a range of totals due to these factors which make it challenging to give an exact forecast.
5. Would you expect to find a subsidence inversion to be associated with high or low pressure? What effects might a subsidence inversion have on weather conditions at the ground? Subsidence inversions happen in areas of high pressure. A mass of cold air sinks slowly and is heated by adiabatic compression lower in the atmosphere. This causes this type of inversion. Subsidence inversions are high in the atmosphere and never reach the bottom because of turbulent mixing. The top of a subsidence inversion can usually be indicated by a smoky or dusty looking layer that has a distinguishable line. This line marks the top of this inversion. Effects can include low visibility and poor air quality.
Ahrens, C. D. (01/2014). Essentials of Meteorology: An Invitation to the Atmosphere, 7th Edition [VitalSource Bookshelf version]. Retrieved fromhttp://online.vitalsource.com/books/9781305439733