The non-uniform distribution of aerosol sources and sinks, their differing sizes, short atmospheric lifetimes and intermittent removal processes means that the spatial distribution of aerosols is also non-uniform. The amount of aerosols varies substantially between locations and from year to year, and also exhibits a strong seasonal cycle. Evaluation of the effects of aerosols on climate requires high-resolution measurement of the spatial and temporal variation of aerosol amounts and their properties. An effort is made in the present study to understand global and regional aerosol columnar and vertical variability. In the mid-latitudes in the southern hemisphere, aerosol optical depths (AOD) are better represented by data from the MODIS (Moderate resolution Imaging Spectro-radiometer) sensor whilst in the northern hemisphere, because of the presence of a desert in the tropical latitudes, CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) observes higher AODs compared to MODIS. The natural dust and burning biomass aerosols seem to dominate the total AOD, and show a strong seasonal cycle with increased dust aerosols during the spring and summer, and burning biomass aerosols dominating during September-November. South East Asia and East Asia shows a small aerosol occurrence at higher altitudes, mainly attributed to convective activities.

To better understand the impact of aerosols on climate, the regional aerosol variability must be understood and quantified, rather than simply using a global average. Hence, this study also focuses on the variability of aerosols over East Asia. The annual variation from different sensors shows the same variability: maximum AOD during the spring season (due to dust transport and smoke aerosols), and a minimum during the summer monsoon period (due to the wash out effect or aerosols acting as cloud condensation nuclei). However, the sensors used also differ considerably from one another and therefore it is necessary to establish a combined approach using all the different sensors to obtain a better perspective. The maximum dust loading over East Asia occurs in March-May, and the maximum smoke aerosol loading occurs during June-August, mainly as a result of wind transport from Southern China. The vertical aerosol distribution of aerosols is very important in understanding aerosol-cloud interaction processes. Across East Asia we observe that dust aerosols in spring show a broad distribution from the surface to 10 km altitude, while in June-August, a lower dust loading is seen. While the smoke aerosols show similar concentrations in both March– May and June– August, the altitude at which they are dominant differs; in March– May, the smoke layer is present at higher altitude than that observed in June– August. This may prove an important observation to help explain in detail the differing radiative effects and aerosol-cloud interaction phenomena over East Asia.

1. INTRODUCTION

1.1 Purpose of this research

1.2 Background

1.3 Distribution of Aerosols in the Atmosphere

1.4 Types of Aerosols

1.5 Climatic Effects of Aerosols

2. DATA AND METHODOLOGY

3. RESULTS AND DISCUSSION

3.1 Global perspective

3.2 Region-wise aerosol profile characteristics

3.3 East Asia regional perspective

4. CONCLUSIONS