TAO, Vol. 12, No. 1, 41-62, March 2001 Inventory of Aircraft Emissions over the Taiwan Area Po-Hsiung Lin 1 , Wei-So Sun 1 , and Jen-Ping Chen 1, * (Manuscript received 12 September 2000, in final form 22 February 2001) 41 The inventory of aircraft emissions over the Taipei Flight Information Region (FIR) has been developed with 1997 as the baseline year. We first analyze the spatial and temporal distribution of flight frequency based on the official civil aviation monthly reports, airline flight schedules and pi- lots’ on-air reports. Fuel consumption and trace-gas emissions are then calculated by using the engine performance database of the International Civil Aviation Organization (ICAO) and a few other data sources. The emission inventory is further classified according to the flight types (domestic or international), aircraft types (passenger jets, cargo jets or propeller aircraft), as well as the state of aircraft operation (idle, takeoff, climb-out, cruise and approach/landing). Engine types, number of engines per aircraft, as well as engine performance at different operation states are all consid- ered in estimating the emission rates. The emission rates of six trace chemicals (NO X , CO, CO 2 , S, HC and H 2 O) are estimated for all flight routes and airports, and at different cruise altitudes. To get a sense of their relative importance, we compared the total emissions from aircraft over the Taipei FIR with those from the ground transport in Taiwan. The ratios we obtained are 14.5% for NO X , 9.5% for S, CO 2 and H 2 O, 0.86% for CO, and 0.42% for HC. About 85% of the NO X and 80% of the S, CO 2 and H 2 O were emitted into the upper troposphere, whereas most of the CO (74%) and HC (60%) were produced on the surface. A further comparison shows that the amount of aircraft-produced NO X over the Taiwan area is about 69% of those produced over Mainland China, and aircraft-produced sulfur is about 1.1% of those produced globally. (Keywords: Emission inventory, Civil aircraft, Taipei FIR) 1. INTRODUCTION Aircraft emissions have many impacts on global environment, such as the emissions of 1 Department of Atmospheric Sciences, National Taiwan University, Taipei, Taiwan, ROC *Corresponding author address: Prof. Jen-Ping Chen, Dept. of Atmospheric Sciences, National Taiwan University, #1, section 4, Roosevelt Road, Taipei, Taiwan, ROC; E-mail: jpchen@water.as.ntu.edu.tw ABSTRACT