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SUBMITTED BY:MANORAMA MUKUT 01 AGM/13

TEMPORAL & SPATIAL TEMPORAL & SPATIAL VARIATION OF VARIATION OF TEMPERATURE & TEMPERATURE & PRESSURE ON EARTHPRESSURE ON EARTH

Temperature Basics Temperature Basics Temperature : Measure of average kinetic energy

(motion) of individual molecules in matter

Three temperature scales (units): Kelvin (K), Celsius (C), Fahrenheit (F)– All scales are relative– degrees F = 9⁄5 degrees C + 32

– degrees K = degrees C + 273.15

Vertical Variation of Temperature The rate of decrease in temperature

of air with increase in height as it moves upward due to adiabatic cooling is termed as adiabatic lapse rate.

The average lapse rate upto tropopause is 6.5degrees/km.

A posit ive lapse rate means decrease in temperature with height whereas a negative lapse rate is called inversion inversion in which temperature increases with height.

Atmosphere and Temperature

Due to surface heating (Longwave, Latent heat, Sensible heat)

Due to ozone absorption of sunlight

Due to Solar winds, Cosmic rays

Decreasing rate w/ height (Lapse rate):6.5 oC/km

Spatial variation of Temperature

temperature across the latitude i.e change in temperature with horizontal distance is known as Temperature gradientTemperature gradient..

The isothermsisotherms joins the places of equal temperature and thus exhibit the horizontal distribution of temperature.

Factors affecting Temperature on Earth

LatitudeAltitudeLand and water massOceanic currentsTopography of landForest and vegetationClouds and rainfall

Variation of temperature with latitude:-

Variation in Temp. of Land & Water bodies

Temporal VariaTion of TemperaTure

Diurnal variation:- Minimum temperature at sunrise. Continuous rise in temperature upto noon. Difference between the max. and min. temp.

attained is referred to as the daily range. Diurnal temp. range is the greatest at low

latitudes and continental locations. Least at high latitudes and at maritime

locations.

Diurnal VariaTionS

ANNUAL PATTERN OF TEMPERATURE

Difference between highest and lowest temperature attained during the year is annual range(diff. between average temperature of the warmest & coldest month).

2 temperature maxima and 2 minima in the tropics.

Smallest range occurs near equator & largest in high latitudes.

MONTHLY AVERAGE TEMPERATURE

Pressure Essentials Pressure – force exerted/unit area. units - Pascals (Pa) or millibars (mb) (1 mb =

100 Pa) Average surface pressure over globe: 1013.2 mb. Atmosphere is mixture of gases -> partial

pressure. Dalton’s Law: sum of partial pressures equals

total pressure

Pressure gradient (pressure difference between two locations/distance) gives rise to a force (pressure gradient force), which sets the air in motion.

IDEAL GAS LAW

Describes relationships between pressure, temperature, and density (Start w/ molecular movement in sealed container Pressure proportional to rate of coll isions between molecules and walls).

At constant temperatures, an increase in air density wil l cause a pressure increase (Add more molecules increase density increase rate of coll isions raise pressure)

Under constant density, an increase in temperature wil l lead to an increase in pressure (Raise temperature increase speed of molecules increase rate of coll isions raise pressure)

Pressure = density x temperature x 287 J kg-1 K-1

[ p = ρTR]

Pressure decreases with height

Because downward gravity force is balanced by vertical pressure gradient force (called hydrostatic equilibrium)

ΔΔ p/p/ΔΔ z = z = ρρ ggPressure decreases non-linearly with height (Because air is compressible, so denser near the surface)

Vertical pressure distribution: Hydrostatic equilibrium

ρρgg

ΔΔp/p/ΔΔzz

Spatial distribution of Pressure

Pressure maps depict isobars, lines of equal pressure Through analysis of isobaric charts, pressure gradients are

apparent Steep pressure gradients are indicated by closely spaced

isobars Typically only small gradients

exist across large spatial scales

(4% variation at continental

scale), smaller than

vertical gradients.

Causes of Horizontal Variation of Pressure• Differential heating producing density

contrasts and atmospheric circulation.

• Gravitational pull of moon causing atmospheric tides.

• Effect of latitude forming symmetrical pattern of pressure zones on the earth.

Global Pressure Belts

• Along the equator, doldrums or equatorial lowsdoldrums or equatorial lows are found.

• Sub tropic highsSub tropic highs are found at 25degree-30degree north and south.

• Sub polar lows Sub polar lows are found at 60-70degree north and south latitude.

• Polar highs Polar highs at poles.at poles.

GLOBAL PRESSURE GLOBAL PRESSURE BELTSBELTS

PERIODIC VARIATION

Atmosphere is a dynamic medium. Periodic pressure change occurs daily

& characteristic of tropics & sub-tropics.

Air pressure shows 2 highs & 2 low points each day.

Peak pressure occurs at 10.00a.m & 10.00p.m while low points midway at 4.00p.m & 4.00a.m; caused by solar tide or thermal tide.

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