Topic 6: Atmospheric Moisture and Global Precipitation Introduction Humidity: -Absolute Humidity -Specific Humidity -Relative Humidity Atmospheric Stability.

Topic 6: Atmospheric Moisture and Topic 6: Atmospheric Moisture and

Global PrecipitationGlobal Precipitation

Introduction

Humidity:

- Absolute Humidity- Specific Humidity - Relative Humidity

Atmospheric Stability

Topic 5: Atmospheric Moisture Topic 5: Atmospheric Moisture and Global Precipitationand Global Precipitation

Adiabatic Activities

Condensation Process:- Cloud & Cloud Classification- Fog

Precipitation:- Ice-Crystal Formation Process- Collision-Coalescence Process

Topic 5: Atmospheric Moisture Topic 5: Atmospheric Moisture and Global Precipitationand Global Precipitation

- Types of Precipitation- Acid Rains

Global Pattern of Precipitation

Atmospheric Moisture: Atmospheric Moisture: An IntroductionAn Introduction

Water vapor is one of the atmospheric gases

>½ of all water vapor is found within one mile (1.6 km) of the earth surface

Very small fraction occurs above 4 miles (6.4 km)


Water vapor is unevenly distributed and may be very low over desert areas and may be up to 4% by volume over equatorial areas

Evaporation of liquid water is the main source of water vapor (gas) in the atmosphere


Latent heat of vaporization is stored in the vapor during evaporation

The rate of evaporation is enhanced by:- water temperature- air temperature- degree of windiness

Changes in the State of Water in Relation to Changes in the State of Water in Relation to Energy Absorption and ReleaseEnergy Absorption and Release


Evapotranspiration is another source of vapor to the atmosphere

It is the transfer of moisture through plants to the atmosphere

The maximum rate of evapotranspiration, when water is not limiting, is called potential evapotranspiration (PE)


Where PE exceeds actual precipitation:- no water is available for storage- soils become dry and - vegetation turns brown

Atmospheric Moisture: Atmospheric Moisture: HumidityHumidity

Humidity is the amount of water vapor in the atmosphere

It’s may be measured and expressed as:- Absolute Humidity (gm/m3) - Specific Humidity (gm/kg) - Relative Humidity (%)

Atmospheric Moisture: Atmospheric Moisture: Absolute HumidityAbsolute Humidity

Absolute Humidity measures the total water vapor content of air

It’s expressed as weight of water vapor in a given volume of air (gm/m3)

Absolute Humidity is very sensitive to:- temperature changes - changes in air volume

Atmospheric Moisture: Atmospheric Moisture: Specific HumiditySpecific Humidity

Specific Humidity measures the mass or weight of water vapor content in a given mass of air

It’s expressed as mass (gm) of water vapor in one kilogram (kg) of air (gm/kg)

For any given temperature, there is a maximum mass of vapor that a kilogram of air can hold (i.e. saturation quantity)


In cold polar air, specific humidity may be as low as 0.2gm/kg

In warm equatorial air, specific humidity may be as high as 16gm/kg

Specific humidity progressively increases from the poles to a single peak at the equator

Pole-To-Pole Values of Specific Humidity (gm/kg)Pole-To-Pole Values of Specific Humidity (gm/kg)


Both absolute and specific humidity measure the quantity of precipitable water in the atmosphere

Atmospheric Moisture: Atmospheric Moisture: Relative HumidityRelative Humidity

Relative Humidity (R.H.) measures the percentage of water vapor present in the atmosphere relative to the maximum quantity the air could hold at the given temperature

Relative Humidity (R.H.) changes as air’s capacity to hold moisture (i.e. its vapor content) changes

There is an inverse relationship between temperature and relative humidity such that relative humidity is lower during the hot daytime and higher during the cooler night

Relative Humidity and Temperature ChangesRelative Humidity and Temperature Changes


Relative Humidity (R.H.) increases if:- evaporation increases vapor content of

air- cooling reduces the holding capacity of air

Relative Humidity decreases if:- moisture is removed by condensation or dispersal - heating increases air holding capacity


Relative Humidity (R.H.) could be measured using this formula:

Vapor pressure R.H. = ---------------------------------- X 100

Saturation Vapor Pressure

R.H. is 100% at saturation

R.H. is 50% if only half of the total vapor is present


Air that has R.H. of 100% (saturation) at cool temperature might be far from saturation at a warmer temperature even if the actual amount of moisture is unchanged

Dew point is the temperature at which air becomes saturated during cooling


Instrument used for measuring relative humidity is called a hygrometer

A homemade hygrometer uses a strand of human hair attached to the end of a pointer to determine R.H.

The hair changes in length in response to changes in R.H.


The pointer falls whenever R.H. is high, or the hair lengthens when R.H. is high

Another method for measuring R.H. is through the use of a psychrometer which consists of 2 thermometers:- a dry bulb thermometer - a wet bulb thermometer


The difference between the dry and wet bulb thermometer readings is called wet bulb depression

It involves the calculation of the wet bulb depression

The wet bulb depression is entered into a psychrometric table to obtain the R.H.

Pole-To-Pole Variation of Relative Humidity (%)Pole-To-Pole Variation of Relative Humidity (%)

Relative Humidity Values (%) and Temperature in Relative Humidity Values (%) and Temperature in o o FF

Relative Humidity Values (%) and Temperature in Relative Humidity Values (%) and Temperature in o o CC

Dew-Point Temperature in Dew-Point Temperature in o o FF

Atmospheric StabilityAtmospheric StabilityRising air causes condensation and

precipitation to occur

But the ability of air to rise is closely related to atmospheric stability

Air will rise when the air is unstable

Air will resist upward movement or sink when the air is stable

Stable and Unstable AtmosphereStable and Unstable Atmosphere

Atmospheric StabilityAtmospheric Stability

The air is unstable when the parcel of air is warmer (lighter) than the surrounding air

The air is stable when the parcel of air is cooler (heavier) than the surrounding air

Atmospheric stability could also be stated in terms of the lapse rate concept

Adiabatic Cooling and WarmingAdiabatic Cooling and Warming

Adiabatic Cooling in a Balloon and Cooling of Adiabatic Cooling in a Balloon and Cooling of Surrounding Air (Environmental Lapse RateSurrounding Air (Environmental Lapse Rate

Atmospheric StabilityAtmospheric Stability

The air is stable when:- lapse rate of the surrounding air is

less than the dry adiabatic lapse rate (DALR) of the rising air

The air is unstable when:- lapse rate of the surrounding air is

greater than the dry adiabatic lapse rate (DALR) of rising air

Atmospheric Stability in Relation to Lapse RateAtmospheric Stability in Relation to Lapse Rate

Stable AirStable Air

Atmospheric StabilityAtmospheric StabilityThe air is conditionally unstable when:

- lapse rate of the surrounding air is in-between the dry and wet adiabatic lapse rates

Stable air produces no clouds due to lack of adiabatic cooling

But when stable air is forced to rise, it cools to produce stratiform clouds and drizzly precipitation

Atmospheric Stability in Relation to Lapse RateAtmospheric Stability in Relation to Lapse Rate

Unstable AirUnstable Air

Conditionally Unstable AirConditionally Unstable Air

Adiabatic Cooling and Warming of Adiabatic Cooling and Warming of Rising AirRising Air

When unsaturated air rises it cools at a relatively steady rate of 5½o F/1000 ft (10oC/1000 m) called dry adiabatic lapse rate (DALR)

There is no gain or loss of heat during adiabatic cooling or warming

As rising air cools, its capacity to hold water decreases (i.e. R.H. increases)

Types of Lapse RatesTypes of Lapse Rates


As rising air continues to cool and its relative humidity continues to increase until it reaches saturation or R.H of 100%

The temperature at which relative humidity is 100% is called dew point temperature


The altitude at which dew point temperature is reached is known as the lifting condensation level (LCL)

Condensation (or cloud formation) begins at LCL when the rising air becomes saturated or R.H. of 100%

Hence, LCL becomes the base of a cloud


Condensation causes latent heat to be released

As a result, the addition of latent heat to the atmosphere causes the air rising beyond LCL to cool at a slackened or reduced rate


This diminished cooling rate is called the wet adiabatic lapse rate (3.3o F/1000ft) (WALR or SALR)

adiabatic cooling or warming processes apply only to air in motion

environmental (average) lapse rate applies to non-moving air (3.5o F/1000 ft or 6.4oC/1000 m)

Condensation ProcessesCondensation Processes

Condensation begins in saturated air or R.H. is 100%

But surface tension inhibits the growth of droplets from molecules formed by condensation

Hence, condensation surfaces or nuclei are needed, for droplets to develop on, in order to overcome surface tension

Condensation Processes Condensation Processes

Examples of condensation nuclei include:- tiny particles- smoke- salt- pollen, etc.

Silver iodide is used as condensation nuclei during artificial rain making in a process called cloud seeding

Condensation ProcessesCondensation ProcessesWater vapor condenses around

condensation nuclei to form water droplet

In the absence of condensation nuclei, condensation is suppressed causing the air to become supersaturated if cooling continues

Water droplets remain in liquid form at temperature as cold as -40o F or -40o C if the droplets are dispersed as fine droplets

Condensation ProcessesCondensation Processes

Liquid water droplets at such temperature are super cooled droplets

Super cooled droplets are important because they promote the growth of ice crystals in cold clouds

The visible expression of condensation is the cloud

Condensation Processes: CloudsCondensation Processes: Clouds

Clouds are composed of water droplets and ice crystals

The base of a cloud is clear-cut and corresponds with the LCL

Clouds grow upward from the base or LCL


It is the source of all precipitation but not all clouds form precipitation

Cloud may be classified on the basis of height of its base as:- High cloud or cirrus cloud

(> 6 km cloud base)- Middle cloud or alto cloud

(2 – 6 km cloud base)- Low cloud (0 – 2 km cloud base)

Principal Types of CloudPrincipal Types of Cloud


High Clouds or Cirrus (Ci) clouds:

- cloud base is above 6 km - small amount of water vapor present - low temperature - thin and white clouds of ice crystals - examples: cirrus, cirro-cumulus, cirro-stratus

High Cirrus (Mares’ Tails) CloudHigh Cirrus (Mares’ Tails) Cloud


Middle clouds or Alto (A) clouds:- occurs between 2 and 6 km - examples: altocumulus, altostratus

low clouds: - occurs between 0-2 km - examples: stratus, stratocumulus,

nimbostratus and cumulonimbus- cumulonimbus cloud has vertical extent extending up to 15 km or more

Condensation Processes: CloudsCondensation Processes: CloudsClouds could also be classified on the

basis of cloud forms as: - Stratiform- Cumuliform- Strato-Cumulus

Stratiform: - It’s a layered cloud- It forms blanket cover - It produces large precipitation

A Low Stratus Cloud OvercastA Low Stratus Cloud Overcast

Condensation Processes: CloudsCondensation Processes: CloudsCumuliform:

- It is globular or bubble like masses- It is puffy in form

Strato-cumulus:- It describes clouds with merged puffs - It forms a continuous layer - "nimb" in cloud name means precipitation producing cloud- Example: cumulonimbus, nimbostratus

Puffs of Fair-weather Cumulus CloudsPuffs of Fair-weather Cumulus Clouds

Cumulonimbus CloudCumulonimbus Cloud

Condensation Processes: FogCondensation Processes: Fog

Fog is cloud in direct contact with the ground surface and hinders visibility

On the basis of how they are formed, there are different types of fogs: - Radiation Fog- Advection Fog- Orographic Fog- Evaporation Fog

Condensation Processes: FogCondensation Processes: Fog

Radiation Fog:- It’s formed by radiation cooling often caused by temperature inversion, especially at night

Advection Fog:- It’s formed when warm air moves over cold ground surface- Example: Grand Banks fogs or fogs formed over cold currents

Radiation FogRadiation Fog

Advection FogAdvection Fog

Condensation Processes: FogCondensation Processes: FogOrographic or Upslope Fog:It is the result of adiabatic cooling of

humid air forced to ascend a topographic slope

Evaporation Fog:It is the result of addition of water vapor

to cold air that is already near saturation Example: Bathroom fog

Orographic (Upslope) FogOrographic (Upslope) Fog

Evaporation FogEvaporation Fog

Condensation Processes: DewCondensation Processes: Dew

Dew forms at night when adjacent air is cooled by conduction to saturation to form tiny beads of water

Ice crystals (white frost) forms if prevailing temperature is below freezing

Example: Early morning wet lawn or wet car

PrecipitationPrecipitation

For clouds to produce precipitation that will fall to the ground:- the tiny water droplets in clouds

must form large raindrop sizes

- the raindrop sizes must be large enough to overcome:

atmospheric turbulence andfall through evaporation

PrecipitationPrecipitation

The mechanism for producing larger raindrops in clouds include:

- ice-crystal formation process or Bergeron process in cold clouds

- collision-coalescence process in warm clouds

Precipitation: Ice-Crystal FormationPrecipitation: Ice-Crystal Formation

Ice-Crystal Formation:

- It occurs in cold clouds, especially in temperate regions

- In cold clouds, ice crystals and super-cooled water droplets coexist

- Ice-crystals attract most of the water vapor because of lower vapor

pressure around them

Ice-Crystal Formations in CloudsIce-Crystal Formations in Clouds


- Super-cooled water evaporates to replenish the vapor supply

- Hence, ice-crystals grow in size at the expense of the super-cooled water droplets

- Ice-crystals grow large enough to fall and picks up more moisture enroute


The enlarged ice-crystals precipitate to form:

- snowflakes when atmospheric temperature is below freezing

- rain when the ice-crystals melt enroute to the ground

Precipitation: Precipitation: Collision-Coalescence ProcessCollision-Coalescence Process

It occurs in warm clouds of the tropics

Large numbers of small droplets in the cloud collide and merge if atmospheric electricity is favorable

They grow larger in this process to form raindrops

Raindrop Formation By Collision and CoalescenceRaindrop Formation By Collision and Coalescence

Types of PrecipitationTypes of Precipitation

Types of precipitation are based on:- how they are formed - how moist air is lifted

Common types of precipitation are:- Convective Precipitation- Orographic Precipitation- Frontal Precipitation

Types of Precipitation: Types of Precipitation: Convective PrecipitationConvective Precipitation

It involves strong updraft of warm moist air (convection cells) due to unequal heating of surfaces

Convection cells rise in succession and expand to cool adiabatically

Cumulus cloud forms with a flat base at the LCL

Convective PrecipitationConvective Precipitation

Convergent or Convective Precipitation?Convergent or Convective Precipitation?


The release of latent heat sustains the upward draft and vertical growth of cumulo-nimbus clouds

It may give rise to thunderstorms or hail

Common in equatorial regions and the tropics throughout the year


It occurs mainly in summer in mid-latitude regions

Bonus Question (5 points)

- Write a short essay on hailstorms (1-2 typed pages, double-spaced)

Types of Precipitation:Types of Precipitation:

Orographic PrecipitationOrographic Precipitation Mountain or relief barrier causes moist air

to be lifted and ascend its windward slope

The rising moist air cools, condenses, and precipitation forms on the windward side

The wind continues to the leeward (rain shadow) side of the mountain as dry and hot wind

Orographic PrecipitationOrographic Precipitation

Orographic uplift ContinuedOrographic uplift Continued

Types of Precipitation:Types of Precipitation:Orographic PrecipitationOrographic Precipitation

Orographic precipitation occurs in California

Moist westerly wind from the Pacific Ocean brings heavy orographic rainfall to the western windward slopes of Californian mountains

Types of Precipitation:Types of Precipitation:Orographic PrecipitationOrographic Precipitation

The westerly winds cross over the Coastal Ranges and Sierra Nevada Mt. (4000 m) to the eastern leeward slopes as dry and hot winds

Hence, the Death Valley, Eastern California and Nevada, in the rain shadow, have dry desert conditions

Types of Precipitation:Types of Precipitation:Frontal PrecipitationFrontal Precipitation

It occurs when warm and cold air masses meet along a front

The warm and lighter air rises over the cooler air and cools adiabatically

Condensation & precipitation may result

This is common in the mid-latitudes and rare in the poles and the tropics

Frontal PrecipitationFrontal Precipitation

Acid RainAcid Rain

Acid rain is a washout process

It involves the washout or removal of pollutants from the atmosphere by:- snow- sleet- hail- fog - rainfall

Acid RainAcid Rain

Sulfur dioxide is washed out as sulfuric acid

Nitrogen oxide is washed out as nitric acid

Carbon dioxide is washed out as carbonic acid

Acid RainAcid Rain

Common sources of pollutants, include:

- sulfur dioxide industrial emissions in smoke stacks

- NO2, NO, NO3, CO, and CO2

emissions in automobile exhausts

Acid RainAcid Rain

Acid rains with pH of 4.5 or less (normal pH for pure water is 7.0) is common

Fishes die below a pH of 4.5

Acid fog with pH of 1.7 occurred in California in 1982

Effects of Acid RainsEffects of Acid Rains Causes lakes to become biological

deserts, no life

Forest trees begin to die

Increased corrosion or weathering of buildings and monuments at rapid rates

Causes acidic soils

Forest Die Back Due to Acid Rain

Effects of Acid RainsEffects of Acid Rains

Effects of acid rains are often felt in downwind locations well outside major pollutant source areas

For example:- Scandinavians and Germans complain

about British pollution- Canadians blame the U.S.- New England states blame the Great

Lakes States further west

Areas Sensitive to Acid RainsAreas Sensitive to Acid Rains

Effects of Acid RainsEffects of Acid Rains

Efforts to stop Acid Rain problems in the U.S., include:

- The U.S. Clean Air Act of 1970which involves:

reduction of sulfur emissionsestablishment of automobile emission

standardsreplacement of coal-fired power plants

Global Pattern of PrecipitationGlobal Pattern of PrecipitationThe global average annual precipitation is

about 90 cm (35 inches)

Total annual rainfall tends to decrease from the equator toward the poles

Hence, equatorial region receives the highest amount of precipitation, with an annual average of 125 - 300 cm

Global Average Annual PrecipitationGlobal Average Annual Precipitation

Global Average Annual PrecipitationGlobal Average Annual Precipitation

Global Pattern of PrecipitationGlobal Pattern of PrecipitationThe subtropics, between lat 15o and 35o N

& S are substantially drier due to air subsidence

Hence, the continental west coasts of the subtropics washed by cold currents are the world's driest deserts

However, the continent east coasts washed by warm ocean currents are often wetter

Global Pattern of PrecipitationGlobal Pattern of Precipitation

The middle latitudes,between lat. 35o and 65o N and S, receive total precipitation that is close to the global average

It is the zone of Westerly wind with winter cyclones

California in this zone have summer drought when STH shifts poleward

January Average Precipitation in the U.S.January Average Precipitation in the U.S.

July Average Precipitation in the U.S.July Average Precipitation in the U.S.

Global Pattern of PrecipitationGlobal Pattern of Precipitation

The high latitudes, between lat. 65o N &S and the Poles, receive low annual precipitation because high latitude cold air has very low capacity for moisture

The zonal distribution of precipitation described is often complicated by:- land and sea distribution- ocean currents and- topography

Review Questions for Topic 6

1)1) The continuous interchange of our planet’s water supply The continuous interchange of our planet’s water supply between Earth and the atmosphere is called what?between Earth and the atmosphere is called what?

A. Saturation

B. Vaporization

C. The hydrologic cycle

D. Evapotranspiration

E. Precipitation Figure 6-1

1)1) The continuous interchange of our planet’s water supply The continuous interchange of our planet’s water supply between Earth and the atmosphere is called what?between Earth and the atmosphere is called what?

A. Saturation

B. Vaporization

C. The hydrologic cycle

D. Evapotranspiration

E. Precipitation

Explanation: The hydrologic cycle is used to describe the distribution of water between Earth and the atmosphere. This distribution is in balance so the general water supply does not change.

Figure 6-1

2)2) The condition of the atmosphere when it contains as The condition of the atmosphere when it contains as much water as it can hold at a given temperature (state much water as it can hold at a given temperature (state of total wetness) is known asof total wetness) is known as

A. breaking point.

B. saturation.

C. atmospheric climax.

D. perspiration.

E. conditional humidity.

2)2) The condition of the atmosphere when it contains as The condition of the atmosphere when it contains as much water as it can hold at a given temperature (state much water as it can hold at a given temperature (state of total wetness) is known asof total wetness) is known as

A. breaking point.

B. saturation.

C. atmospheric climax.

D. perspiration.

E. conditional humidity.

Explanation: When Earth’s atmosphere reaches the point of maximum water vapor content, the air is said to be saturated.

3) 3) There is an inverse relationship between temperature and There is an inverse relationship between temperature and relative humidity such that relative humidity tends torelative humidity such that relative humidity tends to

A. drop drastically at 4 A.M.

B. keep an even balance.

C. be lowest in the afternoon and highest just before dawn.

D. be lowest at dawn and highest in the afternoon.

E. be always high at midnight.

3) 3) There is an inverse relationship between temperature and There is an inverse relationship between temperature and relative humidity such that relative humidity tends torelative humidity such that relative humidity tends to

A. drop drastically at 4 A.M.

B. keep an even balance.

C. be lowest in the afternoon and highest just before dawn.

D. be lowest at dawn and highest in the afternoon.

E. be always high at midnight.Explanation: As the air heats up, the amount of water vapor it holds increases, so that the relative humidity of the air decreases. Since air is warmest in the afternoon, humidity will be lowest, and air is coolest just before dawn, so humidity is highest prior to sunrise.

Figure 6-9

4) 4) When atmospheric lifting results from the meeting of two When atmospheric lifting results from the meeting of two air masses of different physical properties (moisture and air masses of different physical properties (moisture and temperature), the resulting form of precipitation is temperature), the resulting form of precipitation is ________ rainfall. ________ rainfall.

A. anticyclonic

B. relief

C. convectional

D. convergent

E. frontal

4) 4) When atmospheric lifting results from the meeting of two When atmospheric lifting results from the meeting of two air masses of different physical properties (moisture and air masses of different physical properties (moisture and temperature), the resulting form of precipitation is temperature), the resulting form of precipitation is ________ rainfall. ________ rainfall.

A. anticyclonic

B. relief

C. convectional

D. convergent

E. frontalExplanation: When two air masses meet, the boundary between the two is called a front. Air will rise along a frontal boundary above cold air due to the stability of the cold air mass. This is frontal precipitation.

5) 5) The most conspicuous feature of the worldwide annual The most conspicuous feature of the worldwide annual precipitation pattern is that the _______ contain the wettest precipitation pattern is that the _______ contain the wettest areas of Earth. areas of Earth.

A. tropical latitudes

B. poles

C. west coast of continents

D. Northern Hemisphere

E. continental (interior) locations

5) 5) The most conspicuous feature of the worldwide annual The most conspicuous feature of the worldwide annual precipitation pattern is that the _______ contain the wettest precipitation pattern is that the _______ contain the wettest areas of Earth. areas of Earth.

A. tropical latitudes

B. poles

C. west coast of continents

D. Northern Hemisphere

E. continental (interior) locations Explanation: The presence of the ITCZ throughout the tropics

allows for continuous rising motion and threat for rain showers. As a result, the highest rainfall totals occur in tropical regions.

6) 6) Which humidity measure shows how near, in terms of a Which humidity measure shows how near, in terms of a percentage, an air mass is to saturation?percentage, an air mass is to saturation?

A. Absolute humidity

B. Specific humidity

C. Equivalent humidity

D. Mixing ratio humidity

E. Relative humidity

Figure 6-8

6) 6) Which humidity measure shows how near, in terms of a Which humidity measure shows how near, in terms of a percentage, an air mass is to saturation?percentage, an air mass is to saturation?

A. Absolute humidity

B. Specific humidity

C. Equivalent humidity

D. Mixing ratio humidity

E. Relative humidity

Explanation: By definition, the percentage of the atmosphere that is saturated is the relative humidity.

Figure 6-8

7) 7) What property of water makes it “sticky”?What property of water makes it “sticky”?

A. Its solid floats on its liquid

B. Covalent bonding

C. Hydrogen bonding

D. Capillarity

E. EvapotranspirationFigure 6-2

7) 7) What property of water makes it “sticky”?What property of water makes it “sticky”?

A. Its solid floats on its liquid

B. Covalent bonding

C. Hydrogen bonding

D. Capillarity

E. Evapotranspiration

Explanation: The weak electrical attraction that results from the polarity of the water molecule makes water “sticky”. This polarity results from hydrogen bonding.

Figure 6-2

8) 8) Condensation is not sufficient to explain large drop Condensation is not sufficient to explain large drop growth in warm clouds. What is the growth in warm clouds. What is the primary process responsible for this?primary process responsible for this?

A. Bergeron process

B. Rain-snow melt

C. Ice melt

D. Sublimation

E. Collision and coalescence

Figure 6-27

8) 8) Condensation is not sufficient to explain large drop Condensation is not sufficient to explain large drop growth in warm clouds. What is the growth in warm clouds. What is the primary process responsible for this?primary process responsible for this?

A. Bergeron process

B. Rain-snow melt

C. Ice melt

D. Sublimation

E. Collision and coalescence

Explanation: In the tropics, ice crystals do not exist in clouds due to the warm temperatures. So, drops are forced to grow through collision and coalescence.

9) 9) Which of the following pH values is characteristic of Which of the following pH values is characteristic of acid rain?acid rain?

A. 4.5

B. 5.0

C. 5.5

D. 6.0

E. 8.0

Figure 6-39

9) 9) Which of the following pH values is characteristic of Which of the following pH values is characteristic of acid rain?acid rain?

A. 4.5

B. 5.0

C. 5.5

D. 6.0

E. 8.0

Explanation: Typical rainfall pH is on the order of 5 – 5.5. Values of pH lower than 5 are indications of acid rain. The lowest pH values of rain in the United States are below 4.5.

10) In order to grow hail in a cloud, the cloud must have10) In order to grow hail in a cloud, the cloud must have

A. rotation.

B. warm temperatures.

C. strong downdrafts.

D. strong updrafts.

E. weak updrafts.

10) In order to grow hail in a cloud, the cloud must have10) In order to grow hail in a cloud, the cloud must have

A. rotation.

B. warm temperatures.

C. strong downdrafts.

D. strong updrafts.

E. weak updrafts.

Explanation: Storms that have strong updrafts can suspend heavy hailstones in the cloud, allowing more supercooled water to freeze onto the stones and make them larger. Thus, stronger updrafts create bigger hail.

Topic 6: Atmospheric Moisture and Global Precipitation Introduction Humidity: -Absolute Humidity -Specific Humidity -Relative Humidity Atmospheric Stability.

Documents

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