ENVIRONMENTAL SCIENCE

NAME :- AKSHAY JASANIENROLLMENT NO. :- 153551050002

DATE :- 25 – 07 – 2016

LAXMI INSTITUTE OF ARCHITECTURE, SARIGAM

SOLAR RADITION : is radiant energy emitted by the sun, particularly electromagnetic energy. About half of the radiation is in the visible short-wave part of the electromagnetic spectrum. The other half is mostly in the near-infrared part, with some in the ultraviolet part of the spectrum.

• The amount of radiation reaching the earth is less than what entered the top of the atmosphere we classify it in atmosphere . It has 2 categories :

1) Direct Radiation : Radiation from the sun that reaches the earth without scattering.

2) Diffuse Radiation : Radiation that is scattered by the atmosphere and cloud.

- SOLAR RADIATION

• Solar radiation is the most important weather variable that determines whether a place experiences high temperatures or is predominantly cold. The instruments used for measuring of solar radiation are the pyranometer and the pyrheliometer.

• The duration of sunshine is measured using a sunshine recorder.

What are the factors that affect the amount of solar radiation?

The factors that affect the amount of solar radiation are:

-Solar elevationWhere the sun sits in the sky determines the level of UV radiation reaching us. The reason for this is the amount of atmosphere the UV must penetrate to reach us. The longer the path through the atmosphere, the more UV that is absorbed, and this occurs when the sun is near the horizon, whereas when the sun is directly above us the amount of atmosphere is lower which means that less UV is absorbed and a higher level reaches us.

-OzoneOzone is an important part of our atmosphere and high levels of ozone absorb higher levels of UV. Since the discovery of the hole in the ozone over the Antarctic in the early 1980s ozone levels have been observed to decline worldwide, resulting in increased levels of solar UV reaching the earth’s surface.

-Cloud coverHaving a cover of cloud over the sky can reduce the amount of UV radiation reaching the earth’s surface. This is particularly the case when there are significant levels of cloud cover. However it would be wrong to assume that some level of cloud cover means that the UV level is below a level that requires protection. Sometimes reflection of the sun’s rays of clouds can increase UV levels above the expected values.

-Ground surface reflectivityWith solar UV radiation we probably think that the threat comes from above, however there are some surfaces that can increase the ambient levels of UV through reflection. Metal surfaces, concrete and beach sand can all reflect UV back onto a person, increasing the risk of skin damage. Reflected UV is also harmful because the body’s natural defences of the face such as eyebrows, eye sockets and eye lids do not provide protection against the angle of reflected UV.

-AltitudeUV increases at higher altitudes as the atmosphere has less chance to absorb the incoming UV. It has been found that UV increases by up to 4% for every 300m increase in altitude.

-Aerosols and pollutantsSmall particles suspended in the air can scatter solar UV. Whilst the effect is minor it can still have an impact on levels of UV reaching the earth’s surface.

-Direct and diffuse UVUV radiation has the ability to diffuse, which means that if even if you are standing under shade but you can see large areas of the sky, the scattered UV can still reach you. This explains why shade, even though it is an important part of sun protection, does not provide adequate protection on its own.

GLOBAL WIND AND THEIR CAUSES

WINDS : Wind is the movement of air due to a difference in atmospheric pressure, caused by differential heating of land and water mass on the earth’s surface by solar radiation of earth.

• It is a major design consideration for architects because its affects indoor comfort conditions by influencing the convective heat exchanges of a building envelope, as well as causing air infiltration into the building.

• To understand earth’s wind patterns you must think about the weight of the air….•Weight changes with temperature…-Cool Air- Sinks! & Hot Air – Rises!• On a global scale, the rising, sinking, and flowing air creates Earth’s prevailing winds.- Earths rotation causes prevailing winds to curve east to west.• These winds can cool and heat a region, as well as make it drier or wetter.

• Global wind patterns : winds are named by the direction from which they blow. The globe is encircled by 6 major wind belts, 3 in each hemisphere. From pole to equator, they are the polar easterlies, the westerlies, and the trade winds. all six belts move north in summer & south in the northern winter. Becoz the coriolis effect cause global winds to curve, they cannot flow directly from the poles to equator. Instead, global winds travel along 3 routes in each hemisphere. These routes, which circle the world, are called global wind belts.

Coriolis Effect

- Because the Earth rotates, and consists of a mixture of land and sea, the Coriolis Effect exists.- The Coriolis Effect is the movement of particles (such as air) to the right in the Northern Hemisphere.

DIFFERENT CLIMATIC CONDITIONS OF INDIA

DIFFERENT CLIMATIC CONDITIONS OF INDIA

1) Hot and Dry :- Characteristics : The Hot & Dry Zone lies in the western & the central part of India : Jaisalmer,Jodhpur

are some of the towns that experiences this type of climate.- A typical hot & dry region usually flat with sand or rocky ground conditions & sparse vegetation

comprising cacti, thorny trees and bushes.- There are very few sources of water on the surface,& the underground water level is also very low.- Due to intense solar radiation, the ground & the surroundings of this region are heated up quickly

during day time. In summer , the maximum ambient temp. are high.- This region receive less rainfall.• Hot winds blow during the day in summers and sand storms are also experienced. • the night is usually cool and pleasant. A generally clear sky, with high solar radiation causing an

uncomfortable glare, is typical of this zone.• As the sky is clear at night, the heat absorbed by the ground during the day is quickly dissipated to the

atmosphere. Hence, the air is much cooler at night than during the day.

2) Warm & Humid :- Characteristics : The Warm & Humid zone covers the coastal parts of the country. some cities that fall

under this zone are Mumbai, Chennai, Kolkata.- The High Humidity encourages abundant vegetations in these regions.- The diffuse fraction of solar radiation is quite high due to cloud cover, and the radiation can be intense

on clear days. The dissipation of the accumulated heat from the earth to the night sky is generally marginal due to presence of clouds.hence,the diurnal variation in temperature is quite low. in summer, temperatures can reach as high during the day & night. Although the temperatures are not excessive, the high humidity causes discomfort.

- An important characteristics of this region is relative humidity, which is generally very high throughout the year.

- Precipitation is also high. Hence, the provision for quick drainage of water is essential in this zone.- The wind is generally from one or two prevailing directions ranging from extremely low to very high.

wind is desirable in this climate ,as it can cause sensible cooling of the body.- The main design criteria in the warm and humid region are to reduce heat gain by providing shading,

and promote heat loss by maximizing cross ventilation. Dissipation of humidity is also essential to reduce discomfort.

3) Moderate:- Characteristics :Pune and Bangalore are examples of cities that fall under this climatic zone.- Areas having a moderate climate are generally located on hilly or high plateau regions with fairly

abundant vegetation.- the solar radiation in this region is more or less the same throughout the year.- Being located at relatively higher elevations, these places experience lower temperatures than hot

and dry regions.- The temperatures are neither too hot nor too cold.- Relative humidity is low in winters and summers.- Winters are dry in this zone .Winds are generally high during summer. Their speed and direction

mainly depend upon topography. The sky is mostly clear with occasional presence of low, dense clouds during summers.

- The design criteria in the moderate zone are to reduce heat gain by providing shading, and to promote heat loss by ventilation.

4) Cold & Cloudy :- Characteristics : Generally, the northern part of India experiences this type of climate. Most cold and

cloudy regions are situated at high altitudes.Ootacamund,Shimla,shillong,Srinagar and Mahabaleshwar are examples of places belonging to this climatic zones.

• These are generally highland regions having abundant vegetation in summer.• The intensity of solar radiation is low in winter with a high percentage of diffuse

radiation.Hence,winters are extremely cold In summer the maximum ambient temperature during day & night, making summer quite pleasant.

• The relative humidity is generally high and is distributed evenly throughout the year.• This region experiences cold winds in the winter season.Hence,protection from winds is essential in

this type of climate.• The sky is overcast for most part of the year except during the brief summer.• Conditions in summer are usually clear and pleasant , but owing to cold winters.• The main criteria for design in the cold and cloudy region aim at resisting heat loss by insulation and

infiltration, and promoting heat gain by directly admitting and trapping solar radiation within the living space.

5) Cold and Sunny :- Characteristics : The cold and sunny type of climate is experienced in Leh (Ladakh).- This region is mountainous, has a little vegetation, and is considered to be a cold desert.- The solar radiation is generally intense with a very low percentage of diffuse radiation.- Winters are extremely cold.- The relative humidity is consistently low & precipitation is generally less>- winds are occasionally intense. The sky is fairly clear throughout the year with a cloud cover.- As this region experiences cold desert climatic conditions, the design criteria are to resist heat loss by

insulation and controlling infiltration.- Simultaneously, heat gain needs to be promoted by admitting and trapping solar radiation within the

living space.

6) Composite:- Characteristics :The composite zone covers the central part of India. some cities that experiences this

type of climate are New Delhi, Kanpur and Allahabad.- A variable landscape and seasonal vegetation characterize this zone. the intensity of solar radiation is

very high in summer with diffuse radiation amounting to a small fraction of the total.- In monsoon the intensity is low with predominantly diffuse radiation .- The presence of high humidity during monsoon months is one of the reasons why places like New

Delhi and Nagpur are grouped under the composite and not hot and dry climate.- This region receives strong winds during monsoons from the south-east and dry cold winds from

north-east.- In summer, the winds are hot and dusty. The sky is overcast and dull in the monsoon, clear in winter

and frequently hazy in summer.- Generally. Composite regions experience higher humidity levels during monsoons than hot and dry

zones. Otherwise most of their characteristics are similar to the latter.- Thus, the design criteria are more or less the same as for hot and dry climate except that maximizing

cross ventilation is desirable in the monsoon period.