Wednesday, March 27, 2013


1. ‘Mother of pearl’ or ‘nacreous’ clouds are found in stratosphere. Noctiluent clouds are found in Mesosphere.

Division of Ionosphere (60-640 Km)
1. D layer- 60-. Km -Reflects signals of low frequency radio waves only. Disappears with sunset.
2. E layer -99-130 km- Called Kenley- Heaviside layer. Reflects medium & high frequency radio waves. Produced by ultraviolet photons reacting with nitrogen. Disappears with sunset.
3. Sporadic E Layer -110 km- Associated with very high velocity winds & created under special circumstances. Reflects VHF waves
4. E2 layer- 150 km- Produced by reaction of UV photons with O2. Disappears with night.
5. F Layer -1550-380 km- Consists of F1 & F2 layers collectively called Appleton layer. Reflects medium & high frequency radio waves.
6. G layer 400 km & above Persists day & night but not detectable as F layer reflects all the waves reflected by this layer. Interaction of UV photon with nitrogen produces free electrons here.

2. The auroras are maximum when the sun is very active. Hence they are opposite of sun spot cycle. Inside the magnetosphere are the Van Allen radiation belts concentrated in two bands at about 3000 km & 16000 km.

3. According to Wein’s displacement law, hotter the object smaller the wavelength. According to
Stefan Boltzman law influx of radiation is proportional to the fourth power of absolute temperature
of the radiating body.

4. Heat Budget: Out of the 100 units of incoming solar radiation, 35 units (27-clouds, 2-snow, 6 atmosphere top) are reflected back as albedo. Out of the remaining 65 units, 14 units are absorbed by atmosphere & 51 units by earth surface. The earth radiates back 17 units directly into space & remaining 34 units are absorbed by atmosphere. The atmosphere than radiates back the 48 units absorbed by it.

5. Green house gases include CFCs, Nitrous oxide, water vapour & ozone. CFCs account for 25 % of
green house effect & methane for 15 %. Carbon dioxide leads with 55 %.

6. The greatest range of temperature occurs at latitude 60 N.

7. The major types of inversion are: radiation, air drainage, frontal, advection, subsidence. Advection inversion generally occurs when a warm air passes over cold water surface.

8. Highs are Siberian, Hawaiian & Siberian. Lows are Aleutian & Icelandic.

9. Anemometer is used for measuring the speed of wind. Beaufort scale deals with the wind speed & ranges from calm wind to hurricane.

10. Jet streams are fastest during winter season. They blow from west to east.

11. A mist becomes a fog when visibility is reduced to less than a km. Dry adiabatic rate is 10 C per 1000m & moist adiabatic rate is 6 C per 1000m. Stability occurs when the dry adiabatic rate is higher than the normal lapse rate & instability occurs when normal lapse rate is greater than the dry adiabatic lapse rate. If normal lapse rate is lower than wet adiabatic rate it leads to absolute stability & vice versa.

12. Sleet is partially melted snowflakes while hail refers to small balls of ice. Rime refers to very small super cooled droplets which strike ground & tend to freeze immediately on impact.

13. Four principal forms of airmasses are continental polar (cP), maritime polar (mP), continental tropical (cT), and maritime tropical (mT). Thermodynamic modification results in airmasses becoming warm represented by W or cold (K). Mechanical or dynamic modification causes it to become stable (s) or unstable (u).

14. Baroclinic zone is where distinct air mass regions exist & where Fronts separate warmer from colder air. Barotropic is region of uniform temperature distribution with lack of fronts. Temperate cyclones are formed under baroclinic condition & tropical under barotropic condition.

15. Anticyclones are larger than cyclones. Airflow converges aloft in anticyclones & diverges in case of cyclones. Katabatic wind blows from mountains to valley & anabatic vice versa.

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