Virtual temperature Presentation has been prepared by Denis

Virtual temperature Presentation has been prepared by Denis Shitov Group: MA-283

The main aims Definition How to derive a ‘Virtual Temperature’? Formula The relationship between virtual temperature and actual temperature Uses Conclusion

Definition Virtual temperature is the temperature at which a theoretical dry air parcel would have a total pressure and density equal to the moist parcel of air

How to derive a ‘Virtual Temperature’? Consider a volume V of moist air at temperature t and total pressure p that contains a mass md of dry air and mass mv of water vapor. The density of the moist air can be given by: Where prime ‘ indicates partial densities.

Applying the ideal gas equation for each component of the air we obtain: From Dalton’s Law of partial pressures: Substituting in the equation of density: Remember that Rd/Rv = ε => Rv= ε Rd. Therefore, substituting in the above equation M Note that we are using only Rd in this equation

Formula Tv=T(1+0.378•e/P) T - temperature of air e - water vapor pressure P - atmospheric pressure Tv = Т (1 + 0,605s) s - the specific humidity

The relationship between virtual temperature and actual temperature The virtual temperature and the actual temperature are equivalent if no water vapor is in the air and at temperatures below 0 ° C. Otherwise, the virtual temperature is always higher than the actual temperature because air is less dense for warmer air or for air with more water vapor in it.

Uses Thanks to virtual temperature in tasks of static atmosphere we can replace actual air by dry air with the same density, which leads to а simplification of the barometric formula

Also using virtual temperature can be applied to moist air equation of state and other relations are valid for dry temperature. If we enter the virtual temperature in the equation of state of moist air we can get its density: Tv - virtual temperature ρ=P/R•Tv Ρ – pressure R - gas constant of dry air

Conclusion In this work we considered how to derive a virtual temperature, the main records of formula for a virtual temperature, and relationship between virtual temperature and actual temperature

Thank you 

References http://www.igras.ru/index.php?r=199&page=1&id=7187 http://meteorologist.ru/virtualnaya-temperatura.html http://ru.wikipedia.org/wiki/Виртуальная_температура http://en.wikipedia.org/wiki/Virtual_temperature#Uses http://dic.academic.ru/dic.nsf/bse/74700/Виртуальная http://www.pmel.org/Meteorological-Glossary.htm http://en.mimi.hu/meteorology/virtual_temperature.html http://meteorology.geography-dictionary.org/Meteorology-and-Weather-Dictionary/virtual_temperature http://mtp.mjmahoney.net/www/notes/altitude/VirtualTemperature.html