A Simulated Climatology of Asian Dust Aerosol and Its Trans-Pacific Transport. Part I: Mean Climate and Validation

Abstract

The Northern Aerosol Regional Climate Model (NARCM) was used to construct a 44-yr climatology of spring Asian dust aerosol emission, column loading, deposition, trans-Pacific transport routes, and budgets during 1960-2003. Comparisons with available ground dust observations and Total Ozone Mapping Spectrometer (TOMS) Aerosol Index (AI) measurements verified that NARCM captured most of the climatological characteristics of the spatial and temporal distributions, as well as the interannual and daily variations of Asian dust aerosol during those 44 yr. Results demonstrated again that the deserts in Mongolia and in western and northern China (mainly the Taklimakan and Badain Juran, respectively) were the major sources of Asian dust aerosol in East Asia. The dust storms in spring occurred most frequently from early April to early May with a daily averaged dust emission (diameter d Ͻ 41 m) of 1.58 Mt in April and 1.36 Mt in May. Asian dust aerosol contributed most of the dust aerosol loading in the troposphere over the midlatitude regions from East Asia to western North America during springtime. Climatologically, dry deposition was a dominant dust removal process near the source areas, while the removal of dust particles by precipitation was the major process over the trans-Pacific transport pathway (where wet deposition exceeded dry deposition up to a factor of 20). The regional transport of Asian dust aerosol over the Asian subcontinent was entrained to an elevation of Ͻ3 km. The frontal cyclone in Mongolia and northern China uplifted dust aerosol in the free troposphere for trans-Pacific transport. Trans-Pacific dust transport peaked between 3 and 10 km in the troposphere along a zonal transport axis around 40°N. Based on the 44-yraveraged dust budgets for the modeling domain from East Asia to western North America, it was estimated that of the average spring dust aerosol (diameter d Ͻ 41 m) emission of ϳ120 Mt from Asian source regions, about 51% was redeposited onto the source regions, 21% was deposited onto nondesert regions within the Asian subcontinent, and 26% was exported from the Asian subcontinent to the Pacific Ocean. In total, 16% of Asian dust aerosol emission was deposited into the North Pacific, while ϳ3% of Asian dust aerosol was carried to the North American continent via trans-Pacific transport.

Influence of Dust Storm Frequency in Northern China on Fluctuations of Asian Dust Frequency Observed in Japan

“…This situation is favorable to suppress deposition of the dust aerosols and to lead a high concentration condition, and consequently Asian dust is easily recognized. The process is supported by the results of numerical experiments (Wang and Fang 2006;Zhao et al 2006). Wang and Fang (2006) reveals that ascending motion existed in the warm sector, which lifted dust up to 300 hPa.…”

“…Concentration of dust aerosols decrease gradually as the distance from the source regions increases due to diffusion and gravitational removal (dry and wet deposition). Actually, observational (e.g., Sun et al 2001) and modeling (e.g., Zhao et al 2006) studies indicated that maximum of dust deposition was found over the dust source and nearby regions with most of the emitted dust redeposited onto the dust source areas. Asian dust observed manually and it can not be recognized when the concentration is too low.…”

Eolian dust input to the Subarctic North Pacific

“…8). The highest dust fluxes of ∼2-4 g/m 2 /yr are observed west of ∼165 • E and south of ∼45 • N in the southwestern part of the INOPEX cruise track, along the middle of the main pathway of the westerly jet transporting dust over the North Pacific (Husar et al, 2001;Uematsu et al, 2003;Weber et al, 1996;Yumimoto et al, 2009;Zhao et al, 2006). To the north and east of this region, dust fluxes gradually decrease to ∼1-2 g/m 2 /yr over the remainder of the SNP.…”

Based on the earth's surface layer dust flux field observation and study on collection efficiency

“…It is the second largest shifting sand desert in the world, with about 85% of shifting sand dunes (Sun and Liu, 2006).As an area where sandstorms occur frequently, it is known as an important sand-dust source in China (Wang et al, 2000;Qian et al, 2002;Zhou et al, 2002).Sandstorms caused by soil wind erosion in this region have produced great effects on the climatic change in East Asia (Zhao et al, 2006). The Tazhong was regarded as for the saltation activity observation experiment.…”