HUMIDITY,
WATER, AND
WATER VAPOR
NATURE AND BEHAVIOR OF WATER
VAPOR
• Water is the only substance
that exists on Earth in each of
its three states and easily changes from one state to
another
• Water sometimes changes its location by changing state in
the continuous pattern called the water cycle or hydrologic
cycle
• The sun provides the energy to power the water cycle
• When water changes state in the water cycle, the total
number of water particles remains the same. The changes of
state include melting, sublimation, evaporation, freezing,
MELTING
When solid ice gains heat, it
changes state from solid ice to liquid
water in a process called melting
SUBLIMATION
Solid to gas without becoming a
liquid
EVAPORATION
When water absorbs enough heat it
becomes a gas (water vapor)
CONDENSATION
When water vapor loses thermal
energy and becomes liquid water
DEPOSITION
Occurs when water vapor changes state
directly from gas to solid
LATENT HEAT OF
VAPOARTION
The latent heat of vaporization is the
thermal energy required for a liquid to
vaporize to a gas or the amount that is
released when a gas condenses to a
liquid.
Factors affecting evaporation
TEMPERATURE
The rate of evaporation is proportional to temperature. Increasing the
temperature increases the speed of all molecules in the liquid and
brings many closer to the level required to break through the surface.
DEGREE OF
As the air above the liquid gains more water particles, an increasing
SATURATION
number are returned to the water, thus decreasing the net rate of
evaporation.
WIND SPEED
Up to a certain limit, increasing wind speeds remove evaporating
water and thus keep the moisture supply in the air over the water at a
low value
COMPOSITION OF
Evaporation
varies inversely with the salinity of the
WATER
water, proceeding at a greater rate from fresh water
than from salt water.
AREA OF
If
two volumes of water are equal, evaporation wil be
EVAPORATION
greater for the one having the larger exposed surface.
DISTRIBUTION OF WATER
VAPOR IN THE ATMOSPHERE
•The distribution of water in the atmosphere is directly
related to the distribution of temperature
• Water vapor is important for a number of different
reasons, but its presence in the atmosphere is one of the
most important
• Water vapor is present within the atmosphere in varying
amounts but is a vital component of the hydrologic cycle
• In the atmosphere, water vapor can exist in trace
amounts or even make up as much as 4% of the
atmosphere. This concentration depends largely on
where the water vapor levels are measured
• On average, the value of water vapor in the
atmosphere is 2-3% in arid of very cold lactations
such as polar regions — the amount of water vapor in
the air is much lower.
HUMIDITY AND ITS
MEASUREMENT
CAPACITY
AND
• At any SATURATION
given temperature, the maximum amount possible is
called the capacity of the air. One definition of saturation is that
capacity has been reached.
• Saturation can be achieved by either increasing the water
content or decreasing the temperature.
• Saturation deficit – the difference between the capacity of the
air and the actual humidity.
VAPOR
PRESSURE
ACTUAL VAPOR PRESSURE
• the amount of water vapor in terms of the amount
of pressure exerted by the water vapor
molecules alone .
SATURATION VAPOR PRESSURE
• the pressure that the water vapor molecules
would exert if the air were saturated.
INTERRELATIONSHIPS OF HUMIDITY
INSTRUMENT
• Humidity is the amount of moisture in the air. It can be
expressed as absolute, relative, or specific humidity.
From the relative humidity, the partial pressure is determined
because relative humidity is equal to the ratio of the partial
pressure to the saturation vapor pressure. Thus,
RH=
e
x100
E
And
RH x E
e = 100
e is partial pressure
E is saturation vapor pressure
Once the partial pressure of water vapor is
obtained from the above simple
relationship, other quantities such as
absolute humidity, the specific humidity
and mixing ratio can also be obtained
quickly from the following formulas
AH = 217e/T in grams per cubic meter
where T is absolute temperature
SH= 623e/p ( more exactly, 623/p –
0.377e ) in grams per kilogram where p
is atmospheric pressure, and
MR= 623e/p – e in grams per kilogram
HUMIDITY INSTRUMENT
The measurement of
humidity in the air is known
as hygrometers and the
instruments fall under the
general name of
hygrometers include;
PSYCHROMETERS or wet and dry bulb
hygrometer
-
-
Tools used to measure relative
humidity (RH)
- Dry bulb refers to the actual
temperature
Wet bulb refers to the dew point
HYDROGRAPH
This instrument makes
a continuous record
of humidity
HYTHEROGRAP
H
Is a combination of the
thermograph and
the hydrograph, the
two units being
placed in the same
case.
HUMIDITY AND CARGO
• To cope with VENTILATION
the problem of ventilating cargo
holds, a knowledge of humidity and its
measurement is of utmost value.
• It is important to remember that correct
ventilation of general cargo spaces depends
upon the relationship between the dew point of
the air of the cargo spaces and that of the
outside air.
If the dew point of the outside air is higher that the dew
point of the cargo space, ventilation must be restricted.
(2) If the dew point of the outside air is lower than the dew
point of the space, ventilate.
(3) After loading in a cool climate and proceeding into
warmer weather, great care must be taken and
ventilation restricted. Cargo temperatures are slow to
rise and the temperatures are slow to rise and
temperature will have to be carefully watched. When
the cargo has warmed up and the conditions of dew
point are as in (2) above, then normal ventilation can
commence.
(1)
CONDENSATION OF
MOISTURE
CONDENSATION
PROCESS
• Condensation occurs
when the air temperature
falls below the dew point
temperature. The saturated
air then begins to convert
some of its water to a liquid
form.
DEW
• liquid condensation on
surface
• occurs early morning on
windless cloudless days
• air immediately
aboveground cools,
reaches dew point
FROST
• frost is not frozen dew
• frost forms when
condensation takes place
below freezing
temperatures.
PRECIPITATION PROCESS
-
Precipitation is any liquid or frozen water that
forms in the atmosphere and falls to the earth.
- It comes in many forms, like rain, sleet, and
snows.
- Precipitation forms in the clouds when water
vapor condenses into bigger droplets of water
WEATHER
MODIFICATION
Is the act of intentionally manipulating or
altering the weather
•USE OF SILVER IODIDE
CRYSTALS
Silver iodide is burned from ground based
generators or released from aircraft. Upon
reaching the cloud, the silver iodide acts as
an ice forming nuclei to aid in the
production of snowflakes.
• USE OF DRY
ICE
To promote ice crystals growth, intensely cold dry ice
pellets are dropped from airplanes into clouds having
near freezing temperatures.
• Two effects should occur:
(1) Air should be cooled sufficiently so that ice
crystal condensation should occur in the clouds.
(2) Water vapor condensing onto the ice crystals
should release enough latent heat to cause
continued rising and adiabatic cooling of the air
to promote further condensation and thus keep
the process going.
EVALUATION OF SEEDING
• the evaluation of cloud seeding has been based on
statistical comparisons of rhe amount of frequency of
rainfall expected with that observed after seeding.
• It is known that precipitation from clouds on the
windward sides of mountains has been increased up to
10% of what would have occurred through natural
process.
RAIN
- Most common type
of precipitation
- Is when liquid
droplets fall to the
surface of the
earth
SNOW
- Snow forms when
water vapor turns
directly into ice
without ever passing
through a liquid state.
This happens as
water condenses
around an ice crystal.
SLEET
- Sleet consist of
transparent, globular,
solid grains of ice formed
by freezing of raindrops or
freezing of largely melted
ice crystals falling through
a layer of sub freezing air
near the Earth’s surface
HAIL
- Hail is created when
moisture and wind are
together
- Inside the
cumulonimbus clouds
ice crystals form and
begin to fall towards
the surface of the earth
MEASUREMENT OF PRECIPITATION
RAIN GAUGE
• are most commonly
used for the
measurement of
precipitation, both in
terms of rainfall and
snow.
MEASURING THE DEPTH OF
SNOW
-
Depth of snow fall at a particular place can
be measured by the following methods;
• STANDARD RAIN GAUGES
• SNOW GAUGES
• BY SCRATCHING SNOW PACKS
DISTRIBUTION OF
PRECIPITATION
The global distribution of precipitation is
influenced by the general circulation of the
atmosphere, proximity to large bodies of
water and topography.
- Precipitation is most abundant where air
rises, and least abundant when it sinks.
It also tends to be greater near oceans and
lakes, and in higher elevations.
-
-
CONDENSATION
PRECIPITATION
EVAPORATION
SNOWMELT
GROUNDWATER
GROUP 4 REPORTERS:
BSED-SCIENCE 1A
CORTON,
JENELYN
CUARTERO,
SARAH
DANTE, JERIC
DARANTINAO,
MARK
DELA PEÑA,
HAZEL