Lapse Rate and Humidity: Temperature Inversion and Pattern of Lapse Rate

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Lapse Rate and Temperature Inversion

Temperature Lapse Rate

Decrease of temperature with height

Environmental Lapse Rate

Decrease of temperature at any given place and time

Temperature Inversion

Increase of temperature with height

Pattern of Lapse Rate

Pattern of Lapse Rate

Pattern of Lapse Rate

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If air temperature at heights h1 and h2 are T1 and T2 respectively, the lapse rate is given by

Adiabatic Lapse Rate

Decrease of temperature of air parcel with increase in height when no heat is exchanged with the surrounding

Adiabatic Lapse Rate

Adiabatic Lapse Rate

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Atmospheric Stability Condition

Stable

  • Environmental Lapse rate < Dry-adiabatic lapse rate

  • Sub Adiabatic condition

Conditionally Stable

Wet-adiabatic lapse rate<Environmental Lapse rate < Dry-adiabatic lapse rate

Unstable

  • Environmental Lapse rate > Dry-adiabatic lapse rate

  • Super Adiabatic condition

  • Humidity - Amount of water vapour in given volume of air.

  • Expressed in terms of g/m3, g/cm3, mg/cm3.

  • Mixing Ratio - Ratio of weight of water vapour to the weight of per unit volume of dry air.

  • Saturation Mixing Ratio - Concentration of maximum of water vapour in a dry air to certain volume and mass.

Relation between humidity, mixing ratio and saturation mixing ratio

Sounding Instruments

  • Radiosonde: Measures temperature, pressure and relative humidity of air.

  • Rawinsonde: Measures wind speed and direction along with temperature, pressure and relative humidity.

Multiple Choice Questions

1. For which among the following, lapse rate is negative?

  1. Temperature inversion

  2. Increase of temperature with height

  3. Decrease of temperature with height

  4. Both a and b

Answer: d

2.Which among the following is the wet-adiabatic lapse rate?

  1. 6°C/km

  2. 6.5°C/km

  3. 9.8°C/km

  4. 7°C/km

Answer: a

3. When environmental lapse rate is less than dry adiabatic lapse rate, the atmosphere is

  1. Stable

  2. Unstable

  3. Conditionally stable

  4. Both b and c

Answer: a

4. The relative humidity and the saturation mixing ratio of a given environmental condition is 0.4 and 0.05 g/kg respectively. What is the mixing ratio?

  1. 0.1 g/kg

  2. 0.2 g/kg

  3. 0.3 g/kg

  4. 0.4 g/kg

Answer: b

5. Which instrument measures wind speed and direction along with temperature, pressure and relative humidity?

  1. Radiosonde

  2. Hygrometer

  3. Psychrometer

  4. Rawinsonde

Answer: d

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