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4. Precipitation forms in the
clouds when water vapor
condenses into bigger and
bigger droplets of water.
When the drops are
heavy enough, they fall to
the Earth.
CLOUDS
5. If a cloud is colder, like it would
be at higher altitudes, the water
droplets may freeze to form ice.
These ice crystals then fall to
the Earth as snow, hail, or rain,
depending on the temperature
within the cloud and at the
Earth’s surface.
CLOUDS
6. Particles of dust or smoke in the atmosphere are
essential for precipitation. These particles, called
“condensation nuclei,” provide a surface for
water vapor to condense upon. This helps water
droplets gather together and become large
enough to fall to the Earth.
7. CONDENSATION NUCLEI
Condensation nuclei are tiny
particles in the air on which
water vapor condenses and
they are the key to making
clouds, fog, haze, rain, and
other forms of precipitation
8. Precipitation plays a major part in the water cycle as it
is the one which brings in the deposit of freshwater on
the planet. It can be divided into three categories
depending upon the form such as:
• Liquid water
• Ice
• Liquid water freezes when comes in contact with
the surface.
10. RAIN
Rain is the most common form, and it occurs when precipitation falls to the Earth as
water droplets. It happens because of coalescence. This is when two or more water
particles merge and form a single bubble, particle, or droplet. The shape of the water
droplets is spherical, and their sizes range from 0.1 millimeters to 9 millimeters.
11. SNOW
Snow is one of the solid types of precipitation. Snow falls when all the air
between the cloud and Earth’s surface is below freezing. Snow falls in the
form of ice crystals that are formed individually in clouds.
12. FREEZING RAIN
Freezing rain occurs when the layer of freezing air is so thin that the raindrops do
not have enough time to freeze before reaching the ground. Instead, the water
freezes on contact with the surface, creating a coating of ice on whatever the
raindrops contact.
13. SLEET
Sleet is type of precipitation distinct from snow, hail, and freezing rain. It forms
under certain weather conditions, when a temperature inversion causes snow to
melt, then refreeze.
14. HAIL
Hail is a type of precipitation, or water in the atmosphere. Hail is formed when
drops of water freeze together in the cold upper regions of thunderstorm clouds.
These chunks of ice are called hailstones. Most hailstones measure between 5
millimeters and 15 centimeters in diameter, and can be round or jagged.
16. Precipitation occurs when the atmosphere has sufficient
moisture. There must be sufficient nuclei (salt particles,
products of combustion, etc) in the atmosphere to make
condensation happen. Weather conditions must be
favorable for the condensation of water vapor to take
place.Under favorable weather conditions, water vapor
condenses over these nuclei to form tiny water droplets
of size (generally less than 0.1mm in diameter). The
clouds are carried by the wind while its turbulence helps
to retain water droplets in suspension (similar to particles
in a colloidal suspension).
17. Precipitation occurs when these water droplets come
together and coalesce, forming larger drops of water that
can dropdown. When the precipitation occurs, a
considerable part of it evaporates back into the
atmosphere.
Net precipitation at a place and its form depend on a
number of meteorological factors such as temperature,
humidity, wind, pressure in the region.
18. This process happens when the air is cooled and
saturated with the same amount of moisture. This
process of cooling air mass is performed only when the
air mass moves up to higher altitudes. The air mass can
be lifted to higher altitudes mainly by three methods
based on which there are three types of precipitation
namely:
• Cyclonic Precipitation
• Convective Precipitation
• Orographic Precipitation
19. Cyclonic Precipitation
A cyclone is a region in the atmosphere with large low pressure
having circular wind motion. The cyclonic precipitation is caused
by the movement of moist air mass to this region due to the
difference in pressure. Cyclones can be of two types frontal and
non-frontal precipitation.
• Frontal Precipitation
A frontal is called as the hot moist air mass boundary. This
precipitation is caused by the expansion of air near the frontal
surface.
• Non-Frontal Precipitation
This is a cold moist air mass boundary that moves and results in
precipitation.
20. Convective Precipitation
The air above the land area gets heated up by some
cause. The most warmer air rises up and cools and
precipitates. Convective precipitation is showery in
nature. This type of precipitation happens in varying
intensities. The areal extent of convective precipitation
is small in the range of less than 10km in diameter.
21. Orographic Precipitation
Moving air masses have chances to strike barriers like
mountains. Once they strike, they rise up which causes
condensation and precipitation. The precipitation is
greater in the windward side of the barrier compared to
the leeward side of the barrier.
23. RAIN FALL
Rainfall is the amount of precipitation, in
the form of rain (water from clouds), that
descends onto the surface of Earth,
whether it is on land or water.
24. Any form of solid
and liquid water that
falls from
atmosphere to earth
surface
DEPTH
RAIN FALL
CHARACTERISTICS
INTENSITY
DEPTH
DURATION
25. The rainfall depth indicates to
what depth liquid rainfall would
cover a horizontal surface in
an observation period if
nothing could drain, evaporate
or percolate from this surface,
expressed in millimeters (mm).
DEPTH
26. Rainfall duration is how long it rains from the
very first raindrop until the last raindrop.
DURATION
27. Rainfall intensity is the rate at
which the rainfall occurs. It is also
considered as the depth of rain
over a specified time interval.
INTENSITY
28.
29. A hyetograph is a graphical representation of the
distribution of rainfall intensity over time.
HYETOGRAPH
1.3
0.8
1.9
2.04
1.7
1.4
30. Rainfall has traditionally been measured to the
nearest 0.2mm (1 point, or 1/100th of an inch prior
to 1970), although in recent years some
observations are being reported to 0.1mm. Any
moisture less than this is recorded as a trace
Point Rainfall
measurements
31. A rain gauge is an instrument
used by meteorologists and
hydrologists to gather and
measure the amount of liquid
precipitation over a
predefined area, over a
period of time. It is used for
determining the depth of
precipitation that occurs over
a unit area and thus
measuring rainfall amount
Rain
Gauge
32. The recording of rainfall using the
standard or funnel rain gauge
is generally done manually.
These gauges work by
catching the falling rain in a
funnel-shaped collector that
is attached to a measuring
tube. The area of the
collector is 10 times that of
the tube; thus, the rain gauge
works by magnifying the
liquid by a factor of 10.
The Standard Rain
Gauge
33. The operation of a tipping bucket rain gauge is quite
different from the standard gauge. The receiving
funnel leads to one of two small buckets. Filling
of one bucket occurs at one-hundredth of an
inch. The result is a “tipping” of the liquid into
the outer shell of the gauge, triggering the
second bucket to take its place. The process
then repeats itself, allowing for precise
measurement of rainfall intensity and amount.
This gauge has become standard for wireless
weather stations.
The Tipping Bucket Rain
Gauge
34. The universal weighing rain gauge is optimal
for climatology use. This is because of a
vacuum that accounts for the effects of
wind, allowing more rain to enter the
gauge. These gauges are very precise in
measuring rainfall intensity as the
weighing mechanism at the bottom of the
collector can be used to measure depth
and time simultaneously. Recording is
carried out much in the same way as the
older versions of the tipping bucket
gauges.
The Weighing Rain
Gauge
35. Where 'n' is the number of
nearby stations, 'Pi' is
precipitation at ith station and
'Px' is missing precipitation.
1. Simple Arithmetic Mean
Method
According to the arithmetic mean
method the missing
precipitation 'Px' is given as:
Methods for estimation of
missing rainfall data
36. Where Px is the missing
precipitation for any storm at
the interpolation station 'x', Pi
is the precipitation for the
same period for the same
storm at the "ith" station of a
group of index stations, Nx
the normal annual
precipitation value for the 'x'
station and Ni the normal
annual precipitation value for
'ith' station.
2. Normal Ratio Method
According to the normal ratio
method the missing
precipitation is given as: