Question

A radiosonde is released and sends back temperature data as shown in the diagram.

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a. Calculate the environmental lapse rates from the surface up to 3000m.

b. What type of atmospheric stability does the sounding indicate? Suppose the wind is blowing from the west and a parcel of surface air with a temperature of 10 C and a dew point of 2 C begins to rise upward along the western (windward) side of the mountain.

c. What is the relative humidity of the air parcel at 0 m before rising?

d. As the air parcel rises, at approximately what elevation would condensation begin and a cloud start to form?

e. What is the air temperature and dew point of the rising air at the base of the cloud?

f. What is the air temperature and dew point of the rising air inside the cloud at an elevation of 3000 m? (Use moist adiabatic rate of 6 C per 1000 m.)

g. At an altitude of 3000m how does the air temperature inside the cloud compare with the air temperature outside the cloud, as measured by the radiosonde? What type of atmospheric stability (stable or unstable) does this suggest? Explain.

h. At an elevation of 3000m, would you expect the cloud to continue to develop vertically? Explain.

 

Answer 1

Answer

a. Since the dry adiabatic rate and the dew point lapse rate close at 8C/km and since the temperature and the dew point differ by 8C(10C-2C) at the surface, the height Calculate the ELR

 

By formula: ELR=ΔT/h

ELR = 10- (-14)/3000= 8C/km

 

b. 8 C is between the dry adiabatic rate and moist adiabatic rate. Hence the atmosphere is conditionally stable.

c. The vapor pressure at the surface, which is equal to the saturation vapor pressure at the dew point. The saturation vapor pressure at the surface. Thus, the relative humidity is

RH= 𝑒𝑒𝑠 = 6.912.3=0.56=56%

d. of the condensation level is approximately h= 1km=1000m.

e. At the cloud base, the temperature will have dropped by 10C from the surface, hence Tbase= 0C.

f. T (3000 m) = 0°C − 2000 m × 6°C/1000 m = −12°C.

g. The inside temperature (-12 C) is higher than the outside temperature(-14C). This suggests buoyancy for the rising moist parcel. The atmospheric is Conditionally unstable.

h. As explain in part (g) the parcel would continue to rise and therefore to develop vertically.