Chapter 1: Weather Variables Review Questions

Weather: A Concise Introduction Second Edition (pgs. 1 - 18). GENED 1158 at Harvard College

Which variables do we typically measure to describe the state of the atmosphere?

• Temperature

• Pressure

• Wind

• Precipitation

Convert the freezing point (0°C) and the boiling point (100°C) of water to degrees Fahrenheit and kelvin.

0°C = 273.15 K = 32°F

100°C = 373.15 K = 212°F

Convert body temperature (97°F) and fever temperature (103°F) to degrees Celsius.

97°F = 36.11°C 103°F = 39.44°C

Explain how a mercury barometer works. In particular, explain what happens to the barometer when atmospheric pressure increases/decreases.

• A mercury barometer consists of a glass tube filled with mercury, inverted in a dish of mercury.

• When atmospheric pressure increases, it pushes down on the mercury in the dish, causing the mercury level in the tube to rise.

• When atmospheric pressure decreases, the mercury level in the tube falls.

What are the different units of pressure used in meteorology? What is a pressure of 1013 hPa expressed in millimeters of mercury?

• psi, kg/cm², atmospheres/bars (mb)

• 1013 hPa = 760 mm Hg

What is the typical range of atmospheric pressure measured at sea level in the midlatitudes?

980 hPa - 1030 hPa

Describe how wind speed and direction are typically measured at weather stations.

Anemometers are set at the top of “masts” where they can measure wind speed and direction at the standard height of 10 m

Explain the difference between instantaneous wind, sustained wind, and wind gust.

• Instantaneous wind: the wind speed at a specific moment in time

• Sustained wind: wind speed averaged over a certain time period

• Wind gust: higher values of wind speed that only last for short periods of time

Describe two types of rain gauge used in meteorology.

• Tipping Bucket: Water is collected by a funnel and falls onto a tipping plate that tips when enough water has accumulated in the bucket One tip usually corresponds to 0.25 mm (0.01 inches) of rain. The number of tips indicates the amount of rain that has fallen over time.

• Funnel: Collects raindrops and magnifies the rain accumulation into a thinner cylinder so that the total depth may be accurately read on the scale However, only the total depth of accumulated rain is read on the scale. In other words, we have no indication of the changes in precipitation rate between two readings. Such a rain gauge usually measures up to 25 mm, and the overflow is caught in the outside cylinder, for later measurements

What factors should be considered when designing and locating a weather shelter, and why?

• Shade (avoid sunlight/heat contamination)

• Elevated at about 2 meters (avoid contamination from surface effects)

• White paint (reflect light)

• Ventilation (limit heat concentration inside box)

How much additional pressure does your body experience when you dive 10 m underwater? If you dive 35 m underwater, how much total pres- sure does your body experience? (Provide your answer in bars and in millibars.)

• 10 meters: 2013 mb = 2.013 bars

• 35 meters: 4013 mb = 4.013 bars

• For every 10 meters, add 1 additional bar.

Explain why, in a wind report, the sustained wind cannot be greater than the wind gusts.

Wind gusts represent a very short period of time and not an average of multiple wind speed values