MODULE 3: PRECIPITATION

Question 1

It is the general term for all forms of
moisture emanating from the clouds and falling to the
ground.

Answer 1

Precipitation

Question 2

TYPES OF PRECIPITATION

Answer 2

CONVECTIONAL PRECIPITATION

FRONTAL PRECIPITATION

OROGRAPHIC PRECIPITATION

CYCLONIC PRECIPITATION

Question 3

This type of precipitation is in the form of local whirling thunderstorms and is typical of the tropics.

Answer 3

CONVECTIONAL PRECIPITATION

Question 4

It is when the air close to the warm earth gets heated and rises due to its low density, cools adiabatically to form a cauliflower shaped cloud, which finally bursts into a
thunderstorm.

When accompanied by destructive winds, they are called ______.

Answer 4

CONVECTIONAL PRECIPITATION;
TORNADOS

Question 5

When two air masses due to contrasting temperatures and densities clash with each other, condensation and precipitation occur at the surface of contact.

This surface of contact is called a ____ or ________.

Answer 5

FRONTAL PRECIPITATION;
FRONT or FRONTAL SURFACE

Question 6

TYPES OF FRONTAL PRECIPITATION

Answer 6

COLD FRONT
WARM FRONT
STATIONARY FRONT
OCCLUDED FRONT

Question 6

If a cold air mass drives out a
warm air mass, it is called a ____?

Answer 6

COLD FRONT

Question 7

If a warm air mass replaces the
retreating cold air mass, it is
called a ____?

Answer 7

WARM FRONT

Question 7

If two air masses are drawn simultaneously towards a low-pressure area, the front developed is _______ and is called a
________.

Answer 7

STATIONARY;
STATIONARY FRONT

Question 8

Cold fronts move faster than warm fronts and usually overtake them, the frontal surfaces of cold and warm air sliding against each other. This phenomenon is called ________, and the resulting frontal surface is called an ______.

Answer 8

OCCLUSION;
OCCLUDED FRONT

Question 9

This type of precipitation is caused by the uplift of moist air as it flows over a mountain or other elevated terrain.

As the air rises, it cool and condenses, forming clouds and precipitation.

Answer 9

OROGRAPHIC PRECIPITATION

Question 10

This type of precipitation is due to lifting of moist air converging into a low-pressure belt, due to pressure differences created by the unequal heating of the earth’s surface.

Answer 10

CYCLONIC PRECIPITATION

Question 11

Here the winds blow spirally inward counterclockwise in the northern hemisphere and clockwise in the
southern hemisphere.

Answer 11

CYCLONIC PRECIPITATION

Question 12

2 TYPES OF CYCLONE

Answer 12

TROPICAL CYCLONE
EXTRA TROPICAL CYCLONE

Question 13

It is also called hurricane or typhoon of
comparatively small diameter of 300-1500 km causing high wind velocity and heavy precipitation,

Answer 13

TROPICAL CYCLONE

Question 14

This type of cyclone is of large diameter up to 3000 km causing widespread frontal type precipitation.

Answer 14

EXTRA TROPICAL CYCLONE

Question 15

FORMS OF PRECIPITATION

Answer 15

DRIZZLE
RAIN
GLAZE
SLEET
SNOW
SNOWFLAKES
HAIL
DEW
FROST
FOG
MIST

Question 16

It is a light steady rain in fine drops (0.5 mm) and intensity less than 1 mm/h.

Answer 16

Drizzle

Question 17

It is the condensed water vapor of the atmosphere falling in drops from the clouds of sizes larger than 0.5 mm. The maximum size is about 6 mm.

Answer 17

Rain

Question 18

It is a freezing of drizzle or rain when they come in contact with cold objects.

Answer 18

Glaze

Question 19

It is a frozen rain drops while falling through air at subfreezing temperature.

Answer 19

Sleet

Question 20

It is ice crystals resulting from sublimation.

Answer 20

Snow

Question 21

It is ice crystals fused together.

Answer 21

Snowflakes

Question 22

It is moisture condensed from the atmosphere in small drops upon cool surfaces.

Answer 22

Dew

Question 22

It is a small lumps of ice larger than 5 mm in diameter formed by alternate freezing and melting, when they are carried up and down in highly turbulent air currents.

Answer 22

Hail

Question 23

It is a a feathery deposit of ice formed on the ground or on the surface of exposed objects by dew or water vapor that has frozen.

Answer 23

Frost

Question 23

It is a thin cloud of varying size at the surface of the earth by condensation of atmospheric vapor.

Answer 23

Fog

Question 24

It is a very thin fog.

Answer 24

Mist

Question 25

Characteristics of Precipitation

Answer 25

INTENSITY FREQUENCY DURATION

Question 26

It refers to the amount of precipitation that falls during a specific time period, typically measured in millimeters or inches per hour. Higher intensity precipitation events are often associated with more extreme weather conditions, such as thunderstorms, hurricanes, or heavy snowfall.

Answer 26

INTENSITY

Question 27

It refers to how often precipitation events of a certain intensity occur over a specific time period, typically measured in terms of the number of events per year. Frequency analysis can be used to identify the probability of extreme precipitation events occurring in a given region, which can help inform planning and management decisions.

Answer 27

FREQUENCY

Question 28

It refers to how long a precipitation event lasts, typically measured in hours. Longer-duration precipitation events can lead to more widespread and sustained impacts, such as flooding or erosion.

Answer 28

DURATION

Question 28

Patterns of Precipitation

Answer 28

SPATIAL DISTRIBUTION TEMPORAL DISTRIBUTION

Question 29

It refers to the pattern of where precipitation falls over a specific area. This can be influenced by a variety of factors, such as topography, distance from water sources, and prevailing wind patterns.

Answer 29

SPATIAL DISTRIBUTION

Question 29

It is expressed in terms of the depth to which rainfall water would stand on an area if all the rain were collected on it.

Answer 29

PRECIPITATION

Question 29

It refers to the pattern of when precipitation occurs over a specific time period, such as a day, a month, or a year. This can be influenced by seasonal and climatic factors, as well as weather patterns such as fronts and atmospheric disturbances.

Answer 29

TEMPORAL DISTRIBUTION

Question 30

It may be measured by a network of rain gauges which may either be of non-recording or recording type.

Answer 30

RAINFALL

Question 30

TYPE OF RAIN GAUGES

Answer 30

NON-RECORDING RAIN GAUGE RECORDING RAIN GAUGE

Question 31

It is a rain gauge which does not provide the distribution of amount of precipitation in a day. It simply gives the amount of precipitation after 24 hours (daily precipitation).

Answer 31

NON-RECORDING RAIN GAUGE

Question 32

This is also called self-recording, automatic or integrating rain gauge. This type of rain gauge has an automatic mechanical arrangement consisting of a clockwork, a drum with a graph paper fixed around it and a pencil point, which draws the mass curve of rainfall.

Answer 32

RECORDING RAIN GAUGE

Question 33

This consists of a cylindrical receiver 30 cm diameter with a funnel inside. Just below the funnel a pair of tipping buckets is pivoted such that when one of the bucket receives a rainfall of 0.25 mm it tips and empties into a tank below, while the other bucket takes its position, and the process is repeated.

Answer 33

TIPPING BUCKET RAIN GAUGE

Question 34

It is where the mass curve, the depth of rainfall in a given time, the rate or intensity of rainfall at any instant during a storm, time of onset and cessation of rainfall, can be determined.

Answer 34

RECORDING RAIN GAUGE

Question 35

Types of recording rain gauges

Answer 35

TIPPING BUCKET RAIN GAUGE WEIGHING TYPE RAIN GAUGE FLOAT TYPE RAIN GAUGE

Question 36

The tipping of the bucket actuates on electric circuit which causes a pen to move on a chart wrapped round a drum which revolves by a clock mechanism. This type cannot record ____.

Answer 36

SNOW

Question 37

It is when a certain weight of rainfall is collected in a tank, which rests on a spring- lever balance, it makes a pen to move on a chart wrapped round a clock-driven drum.

Answer 37

WEIGHING TYPE RAIN GAUGE

Question 38

It is where the rotation of the drum sets the time scale while the vertical motion of the pen records the cumulative precipitation.

Answer 38

WEIGHING TYPE RAIN GAUGE

Question 39

It is where the rain is collected in a float chamber, the float moves up which makes a pen to move on a chart wrapped round a clock driven drum. When the float chamber fills up, the water siphons out automatically through a siphon tube kept in an interconnected siphon chamber.

Answer 39

FLOAT TYPE RAIN GAUGE

Question 40

It is where the clockwork revolves the drum once in 24 hours. The clock mechanism needs rewinding once in a week when the chart wrapped round the drum is also replaced.

Answer 40

FLOAT TYPE RAIN GAUGE

Question 41

____ is the rainfall at a single station. For small areas less than 50 square kilometers, It may be taken as the average depth over the area. In large areas, there will be a network of rain gauge stations. As the rainfall over a large area is no uniform, the average depth of rainfall over an area is determined by the following three methods

Answer 41

Point Rainfall

Question 42

MEASUREMENT METHODS

Answer 42

ARITHMETIC AVERAGE METHOD THIESSEN POLYGON METHOD ISOHYETAL METHOD

Question 43

This method is fast and simple and yields good estimates in flat country if the gauges are uniformly distributed and the rainfall at different stations do not vary very widely from the mean. The limitation can be partially overcome if the topographic influences and aerial representativity are considered in the selection of gauge sites.

Answer 43

ARITHMETIC AVERAGE METHOD

Question 43

It is obtained by simply averaging arithmetically the amounts of rainfall at the individual rain-gauge station in the area

Answer 43

ARITHMETIC AVERAGE METHOD

Question 44

This method attempts to allow for non-uniform distribution of gauges by providing a weighting factor for each gauge. The station are plotted on a base map and are connected by straight lines. Perpendicular bisectors are drawn to the straight lines, joining adjacent stations to form polygons, known as ______.

Answer 44

THIESSEN POLYGON METHOD; THIESSEN POLYGON

Question 45

In this method, the point rainfalls are plotted on a suitable base map and the lines of equal rainfall (isohyets) are drawn giving consideration to orographic effects and storm morphology. The average rainfall between successive isohyets taken as the average of the two isohyetal values are weighted with the area between the isohyets, added up and divided by the total area which gives the average depth of rainfall over the entire basin.

Answer 45

ISOHYETAL METHOD

Question 45

The results obtained are usually more accurate than those obtained by simple arithmetic averaging. The gauges should be properly located over the catchment to get regular shaped polygons. However, one of the serious limitations of the Thiessen method is its non-flexibility since a new Thiessen diagram has to be constructed every time there is a change in the rain gauge network.

Answer 45

THIESSEN POLYGON METHOD

Question 45

TYPES OF ANALYSIS OF RAINFALL DATA

Answer 45

DESCRIPTIVE STATISTICS TIME-SERIES ANALYSIS SPATIAL ANALYSIS CORRELATION ANALYSIS

Question 46

It can be used to summarize precipitation data, such as the mean, median, and standard deviation of precipitation amounts.

Answer 46

DESCRIPTIVE STATISTICS

Question 46

It involves analyzing the changes in precipitation amounts over time, such as seasonal or annual trends.

Answer 46

TIME-SERIES ANALYSIS

Question 47

It involves analyzing the distribution of precipitation across a region or area, such as the variation in precipitation amounts between different cities or regions.

Answer 47

SPATIAL ANALYSIS

Question 48

It involves examining the relationship between precipitation and other variables, such as temperature, humidity, or atmospheric pressure, to understand the factors that influence precipitation patterns.

Answer 48

CORRELATION ANALYSIS