Chapter 6 Review Questions Explain how the Sun drives the global water cycle. Define vapor pressure. How does Dalton’s law of partial pressures apply to vapor pressure? On a clear calm day, why does...

Chapter 6
Review Questions
Question: Explain how the Sun drives the global water cycle.
Answer Water cycle is powered by energy from sun and gravity
Solar energy evaporates water from oceans, streams, lakes, soil, and vegetation.
Percentage of water vapour in the atmosphere includes 84% from oceans, 16% from
inland waters, vegetation, land etc.
Amount of water vapour entering the atmosphere is the amount of water returing to
earth’s surface.
Winds transport evaporated water, influencing humidity around the wordl rain, sleet,
hail, and snow
Water vapor to precipitation:
Winds and air masses transport water vapor over earth’s surfaces
This vapor condenses into tiny droplets that form clouds as a result of falling
temperatures.
Precipitation will then occur only if the air has condensation
For condensation to occur the temperature must be at dew point.
Question Define vapor pressure. How does Dalton’s law of partial pressures
apply to vapor pressure?
Vapor pressure or equilibrium vapor pressure is defined as the pressure exerted by
a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a
given temperature in a closed system.
Dalton’s Law, or the Law of Partial Pressures, states that the total pressure exerted by a
mixture of gases is equal to the sum of the partial pressures of the gases in the
mixture.
Ptotal=PA+PB+-----
Question:
On a clear calm day, why does the relative humidity usually decrease from a
maximum shortly after sunrise to minimum in the early or mid afternoon?
Ans.
Relative humidity is dependent on temperature. As the temperature changes, so does
the humidity without any additional moisture. This is due to the fact that humidity is a
percent of how much water is in the air compared to how much is needed for the air to
become saturated or a relative humidity of 100%. Since a higher temperature needs
more water to become saturated, the humidity will decrease as the temperature
increases with no change in water content. If the temperature cools and becomes closer
to the saturation temperature then the humidity will increase with no change in water
content in the air. If you add (evaporation) or subtract water (condensation, rain, snow)
then it becomes more complicated but still is temperature dependent.
Question Describe the principal mechanism whereby clouds from in the
atmosphere.
Ans. The formation of cumulus clouds is a situation in which air parcels initially follow
dry adiabates, but subsequently follow wet adiabats after dew point is reached. Solar
heating of the ground warms the adjacent air, and bubbles of this warmed air rises due
to buoyancy, their temperature decreasing with altitude according to the dry adabatic
lapse rate. At the altitude where condensation begins, a cloud forms and the stability of
the air decreases as the air begins to follow a wet adiabat.
Instability can lead to extensive vertical development of the cloud, strong upward air
currents within the cloud and possibly production of a thunderstorm.
Critical Thinking
Question
How and why does the moisture content of the top soil affect the maximum air
temperature in the lower troposphere?
Answer. Because an atmosphere with CO2 and other greenhouse gasses absorbs and
reradiates some of the otherwise space-bound "Earthlight" back to Earth, the Earth’s will
warm if we add more greenhouse gasses to its atmosphere
Question
Are convective clouds (e.g., cumulus) more likely to form over snow-covered
ground or bare ground? Explain your reasoning.
Answer: Over bare ground only. Because, snow is a good reflector of heat and a fairly
good radiator of long wave radiations. consequently, the temperature over a snow
surface tends to sink to very low levels. The air over the snow covered surface will also
be colder and in such a condition, the charge separation (which is responsible for the
formation of convective clouds) will be very weak. Hence, the chances of the formation
of convective clouds over snow covered ground will be less than that over the bare
ground.
Question
Under what atmospheric condition are the actual air temperature, dewpond, and
wet-bulb temperature the same?
Dry Bulb Temperature:
Commonly referred to as Ambient Air temperature. Thermometer is not affected by the
moisture of the air
Wet Bulb Temperature:
The wet bulb temperature is the temperature of an object that can be achieved through
evaporative cooling, assuming good air flow and that the ambient air temperature
remains the same. It is the adiabatic saturation temperature. The bulb of the
thermometer is wrapped in a muslin cloth.
The Wet Bulb temperature is always between the Dry Bulb temperature and the Dew
Point.
 if the dew-point temperature is close to the dry air temperature - the relative
humidity is high
 if the dew point is well below the dry air temperature - the relative humidity is
low
Dew Point Temperature:
The Dew Point is the temperature at which water vapor starts to condense out of the air
(the temperature at which air becomes completely saturated). Above this temperature
the moisture stays in the air.
Note: If, The relative humidity is 100 percent if the dry bulb and wet bulb temperature
are equal then all temperature is same
Rising unsaturated air cools at a rate of 9.8 C degrees per 1000m ascent. Rising
saturated air cools at a lower rate which varies with temperature, but an average cooling
rate of 6 C degrees per 1000 m can be assumed. If the actual decrease in temperature
with height in the atmosphere on a particular day is 8 C degrees per 1000m, and a
rising parcel would remain unsaturated, determine whether that atmosphere is stable or
unstable. If the parcel were saturated, is the atmosphere stable or unstable? Explain
how you made both determinations.
Chapter 7
Review
Question Identify some of the natural sources of nuclei. What role is played by
cloud condensation nuclei in the formation of a cloud?
Cloud condensation nuclei promote condensation of water vapor at temperatures above
and below the freezing point of water.CCN allow cloud droplets to grow and condense
as condensation continues. Natural sources of CCN include ocean spray, volcanic
eruptions, and forest fires
Question 8 Describe the general relationships among the altitude, temperature,
and composition of stratiform clouds.
High stratiform clouds are composed mostly of ice crystals, and have bases at altitudes
above 5000 m.Temperatures in high clouds are typically below -25 °C.Middle stratiform
clouds have bases that range from 2000 to 5000 m and can be composed of ice
crystals, water droplets, or a combination of the two. Temperatures in middle clouds
range between 0 °C and -25 °C Low clouds have bases ranging from the Earth’s
surface to around 2000 m, and are composed mostly water droplets. Low clouds have
temperatures above -5 °C.
Question Identify the unique features of a noctilucent cloud
Noctilucent clouds form in the upper mesosphere at an altitude above 80 km. They are
very rare and only seen at high latitudes in the summer. Composed of tiny water-ice
crystals formed on meteoric dust particles, these clouds are very thin and only appear at
night.
Question Describe the process involved in the formation of warm-cloud precipitation.
Answer: The collision-coalescence process causes precipitation to form in a warm
cloud. This process takes place in clouds made up of cloud droplets of different sizes.
Larger droplets, having a higher terminal velocity than smaller droplets, collide and
coalesce with smaller droplets in their path. The droplets continue to grow, eventually
falling to the Earth as precipitation.
Critical Thinking
Question Explain why rain is normally slightly acidic in a non-polluted
atmosphere. Define acid rain.
Answer: This is due to presence of atmospheric Carbon di oxide CO2 in a non- polluted
atmosphere. Due to emission of Sulphur oxides (SOX), Nitrogen oxides (NOX) to the
atmosphere by any activities including manmade and natural reacting with water vapor
in the atmosphere. When water will fall or precipitation occur, the water contains acid
viz sulphuric acid, nitric acid etc. And damaging the property on earth. Thus, the rain
containing acid is called acid rain.
Question What is the value of weather radar operating...