Study of vertical potential temperature gradient during a few acute air pollution episode in Tehran

Subject Areas : environmental management

Tahereh Ghassami ¹ ( )
Ali Akbar Bidokhti ² ( )
Abdollah Sedaghat Kerdar ³ ( )
Fatemeh Sahraian ⁴ ( )

Received: 2008-06-28 Accepted : 2008-12-07 Published : 2010-09-23

Keywords: Air pollution, Potential Temperature, Stability, Instability, Inversion,

Abstract :

The potential temperature of an air parcel is defined as the temperature which the parcel of air would have if it changed adiabatically from its existing pressure P and temperature T to a standard pressure P0 (generally taken as 1000 mb). Generally, the vertical gradient of potential temperature is used to determine the stability of the air parcel. In this study diurnal variation of potential temperature gradients in the planetary boundary layer of Tehran was considered in two cases, a (convective condition during the day), b (stable condition at night).The data were taken from the air pollution monitoring stations of Tehran for a few acute air pollution episodes in Nov. and Sep. 2001 and Dec.2002. By calculating, three different categories of temperature inversion were found, namely, high, moderate, and weak. We also showed that there is a good correlation between the variation of maximum concentration of NOX, SO2, CO and the potential temperature gradient. This correlation coefficient is about 0.4.