Download weather - Sikkim Springs

WEATHER
Why study weather?
ACWADAM
Plot no.4, Lenyadri CoCo-op Hsg. Society, Sus Road, Pashan
Pune
Phone:020--25871539
Phone:020
Email: [email protected]
Why study Weather?
Affects Nature as well
as lives and livelihoods
natural disasters like
floods
Droughts
Cyclones
Storms
Landslides
Weather is one of the fundamental process that shapes the
earth
– Weathering
– Erosion
Human activities like industries cause adverse effect on climate
– Acid rain due to excessive SO2 and NO.
– Air pollution due to CO2 emitted from vehicles
In the past human settlements have been affected by the change in
climatic conditions
– Desertification of Middle East
Lives and livelihood
Heat wave (More than average temp.)
Cold wave (Less than average temp.)
Affects farmers the most …..
Damage to crops due to;
Delayed rainfall
Excessive rainfall
Untimely rainfall
No rainfall
Affects the cattle and other livestock
Thus affects the total economy of the country
In India:
Diversity in weather conditions or weather types
More than 70% people are engaged in agriculture with almost 80%
of them depending on rain.
Weather data is necessary for any kind of planning of watershed
program
For the study of water balances….
balances….
…And for the sustainable development and management of the
program
Lack of scientific knowledge and data for analysis
Need to understand Weather for a total implementation
of a watershed project as weather plays a key role in the
entire program
India: Rainfall –Annual and Monsoon season
Source: Indian Meteorological dept.
Weather science
The science of studying
weather is called as
Meteorology-Meteorology
– where some predictions
can be made using
atmospheric conditions.
– Or some data can be
generated using simple
equipments.
– Which in turn can be used
for better implementation
of a watershed project
Measurement of weather
parameters like evaporation help
in many ways for better
understanding of the area
Weather
Weather is the specific condition of the
atmosphere at a particular place and time.
It is measured in terms of wind
wind,, temperature
temperature,,
humidity,, atmospheric pressure,
humidity
pressure, cloudiness
cloudiness,,
and precipitation
precipitation..
In most places, weather can change from hourhour-totohour, dayday-toto-day, and seasonseason-toto-season.
The average weather over a longer period is
known as the climate
climate..
What causes weather?
Changes in weather occur
due to the movement of air,
driven by
– the heat energy from the sun;
– the rotation of the Earth.
Together these forces drive
the atmosphere to circulate
on a global scale.
scale.
The local temperature,
pressure, moisture
content, precipitation,
cloud cover, and wind
describe the air mass, and
together these make up the
weather.
Satellite image indicates: Temperature, cloud cover, Sea surface
temperature over the world.
Weather factors
Global scale
Regional scale
Some other factors influencing weather are:
Geographic location:
location: whether it is in the tropics, equator
or temperate region
Surface features and terrain:
terrain: Whether it is an island or
peninsular region, hilly area or plains
Altitude:: whether it is closer to sea or it is located at a
Altitude
high elevation
Parameters
Basically when we
speak of weather we
speak about:
atmosphere,
Rainfall/precipitation
cloudiness,
wind speed & wind
direction
Other factors we
consider during
watershed
management are:
Atmospheric pressure
Humidity
Solar radiation
Evaporation
Evapotranspiration
Atmosphere
It is a mixture of gases.
Transfer of energy takes place in the atmospere
Protects earth from harmful solar radiation
Comprises of four layers Troposphere, Stratosphere,
Mesosphere and Thermosphere
Clouds
Low
Level
cloud
Medium
Level
cloud
High
level
cloud
A cloud is a collection of
minute particles of water or
ice suspended in the air.
air.
Important for energy balance
of the earth.
Important for water transport
Instrumental in determining
climatic zones of the earth
Classified into low level,
medium level and high level
clouds
Wind and solar radiation
Wind
Wind is simply air in
motion.
Generally flows over the
surface of earth from high
pressure to low pressure.
pressure.
Winds are determined by
the direction from which
they blow e.g. easterlies/
westerly.
The two commonly
measured parameters
used to measure wind are:
direction and speed.
Solar radiation
Solar radiation is the
intensity of the sun’s rays
reaching the surface of the
earth.
More the solar radiation
more will be the losses of
water vapour from the
surface.
Atmospheric pressure and humidity
Atmospheric pressure
Humidity
Pressure on a point on the
ground, is the weight of
the column of air above
that point.
point.
Depends upon the altitude.
Sea level -more pressure
than mountain peak
Never constant and keep
changing depending upon
convergence or
divergence of air on global
scale.
Generally, some measure
of the water vapour
content of the air.
At different temperatures
the air contain different
amounts of water vapour
Warm air can hold more
water vapour than cold air.
Generally measured in the
form of relative humidity in
percentage (water vapour
in a column of air)
Evaporation and Evapotranspiration
Evaporation
It is the process by which
water becomes vapour
suspended in air molecule.
It is directly proportional to
temperature and wind
speed and inversely
proportional to the
humidity.
Evapotranspiration
Evapotranspiration is a
measurement of the
amount of water vapor
returned to the air in a
given area.
The losses are by:
– evaporation and
– transpiration (active exhalation
of water through plant skin)
Opposite of rainfall
Rainfall/Precipitation
Any liquid or solid form
of water particles that
falls from the
atmosphere and reaches
the Earth's surface is
known as precipitation.
Precipitation can occur
in a variety of forms
such as drizzle, hail,
rain, sleet or snow.
snow.
Rainfall processes
Orographic rainfall:
rainfall:
Due to effect of altitude.
Convection: Most
Convection:
common process
Cyclonic wedging:
wedging: When two air fronts
meet this type of rain occurs. Heavy
rainfall for about 77-8 hours
Easily measurable
units on field:
Evaporation
Rainfall
Hydrological cycle
In a hydrological cycle, Inflow and Outflow of
water is very important.
Inflow is by means of Rain, hail, dew or snow.
snow.
Outflow is by means of evaporation and
transpiration..
transpiration
Other weather factors add to or reduce the rate of
evaporation.
Therefore measurement of weather parameters
are necessary in the study of hydrological cycle
and eventually watershed management.
Measurement of rainfall
gives a clear idea about
excess or deficit of
rainfall-- Useful for
rainfall
calculating
1.Surface runoff
2.Infiltration
3.Recharge;;
3.Recharge
and also for planning the
next crop using soil
moisture content as an
indicator.
In a watershed,
I=O+ losses;
losses; where I in
inflow and O is outflow .
To get the balance,
correct knowledge of
total rainfall received
over certain area is
important.
Rainfall is measured
using rain gauges and is
expressed in mm or
inches of rainfall over
the area.
Rainfall can be measured on
field using simple rain
gauges
The losses in water cycle occures in many ways.
1. Absorbed by the soil through infiltration
2. Flow as surface flow or runoff
3. Water held in soil or surface gets evaporated or is
transpired by vegetation.
This loss can be measured in meteorology using
instruments like evaporimeters
The evaporation is measured in mm/day
Evaporation can also be measured using empirical
formulae where other factors like wind speed, humidity,
solar radiation and pressure are taken into consideration.
Impacts on livelihood
Different areas with
different weather
conditions (Micro
climate)
Weather conditions
differ within 10 km.
Example: Kolwan
valley
Area 80 sq/km
E-W distance 12km.
Rain gauges installed
at 8 villages
Karmoli
Average rainfall at Karmoli: 1400mm
Average rainfall at Chikhalgaon:
1800mm.
Average rainfall at Hadashi: 2200mm
Average evaporation at Bhalgudi: 7-7.6mm/day
Average evaporation at
Chale: 6-6.5mm/day
Average evaporation at
Chikhalgaon: 6.2-6.8mm/day
Though weather conditions remain constant over the
period, there is a great variability within the area.
Two examples in Pune district illustrated bellow:
bellow:
Kolwan valley
Distance from Pune:40 km
Geology: Deccan basalt
Soil type: Red to reddish brown
silty soils and black clayey soils
(alfisols &vertisols)
Average rainfall: 1800mm
Climate: semiarid
Crops: Rice, sugarcane & wheat
Area covered under DPAP
Purandhar
Distance from Pune:60 km
Geology: Deccan basalt
Soil type: Red to reddish brown
silty soils and black clayey soils
(alfisols &vertisols)
Average rainfall: 500mm
Climate: semiarid
Crops: Jowar, ground nut and
orchards
Area covered under DPAP
Watershed approach may be
different for the two areas
Kolwan valley
More rainfall therefore
more runoff… need to
impound runoff.
Structures may be
constructed in such a way
that it should sustain at
high intensity rainfall
conditions.
Alternative source for
water like springs can be
considered
Purandhar
Less rainfall therefore all
water needs to be
harvested using trenches
etc.
Limited structures could be
constructed considering
recharge and discharge
areas.
Proper water management
should be done involving
community participation
Different methods of water
management required for different
areas
Breaching of earthen check dam
due to heavy rainfall
Adequate water storage
through earthen check dam in
Purandhar
Impact assessment
As the difference is so significant within such a
small distances, there is a great need to have
accurate data for a specific area of interest.
At government level, rainfall and evaporation data
is available at taluka HQ which may not represent
the actual value at the field.
Therefore such data if generated locally, may
prove useful for watershed planning and
development of the area.
As solution to different areas may be different and
same parameters can not be applied everywhere.
In watershed management program weather data
can be used for:
Construction of structures;
Deciding upon crop to be grown in the area;
Implementation of other watershed techniques
like contour trenching, bunds etc;
Calculating water budget for accurate
management of water available resources;
Future planning of other schemes
Preparation of data base for future generation for
reference or academic purposes.
Thank
you
for your
attention