Two-year Microwave Radiometric Observations of Low-level Boundary-layer Temperature Inversion Signatures

Temperature inversion indicates that the atmospheric temperature decreases with increasing height. Its occurrence tends to inhibit vertical motion of the atmosphere. Under the occurrence of temperature inversion, air pollutants cannot be dissipated through vertical mixing of the atmosphere and are accumulated near the surface. When temperature inversion lasts for a long time, human health can be in jeopardy due to deterioration of air quality and secondary pollutants, which are formed through atmospheric photochemistry and more toxic than original ones. It is vital to investigate the dynamics of temperature inversion for understanding and resolving its resulting problems. In this paper, temperature inversion signatures over three major cities on Taiwan are analyzed. They are measured by ground- based microwave radiometers installed in Taipei, Taichung and Kaohsiung from 2002 to 2004 supported by the Environment Protection Agency (EPA) of Taiwan. Characteristics of temperature inversion at the three cities are extracted using different classification methods. The characteristics of temperature inversion in Taichung and Kaohsiung show a similar trend but are different from that in Taipei. The numbers of the occurrence of temperature inversion in Taichung and Kaohsiung were much larger than that in Taipei. The main types of temperature inversion in Taiwan are radiation and frontal inversions. Compared to frontal inversion, radiation inversion on average occurs at a lower altitude, lasts a longer period, has a deeper thickness, and reaches a higher temperature difference of inversion. Frontal inversion plays a significant role for the inversion event lasting over 12 hours.