Increased dust aerosols in the high troposphere over the Tibetan Plateau
from 1990s to 2000s
Abstract
The dust aerosols are a major type of aerosol over the Tibetan Plateau
(TP) and influence climate at local to regional scales through their
effects on thermal radiation and snow-albedo feedback. Based on the
Modern-Era Retrospective Analysis for Research and Applications, Version
2 (MERRA-2) aerosol dataset, we report an increase of 34% in the
atmospheric dust in the high troposphere over the TP during the spring
season in the 2000s in comparison to the 1990s. This result is supported
by an increase of 157% (46%) in the dust deposition flux in the
Mugagangqiong (Tanggula) ice cores and an increase of 69% in the
Aerosol Index (AI) from Earth Probe (EP) Total Ozone Mapping
Spectrometer (TOMS), as well as by increases of simulated dust aerosols
over the TP derived from the Community Earth System Model (CESM) and
models from the Coupled Model Intercomparison Project Phase 6 (CMIP6).
The increased atmospheric dust over the TP is caused in two aspects: (1)
there was a higher dust emission over the Middle East during the 2000s
than during the 1990s, which is explained by less precipitation and
25.8% higher in cyclone frequency over the Middle East. The increased
cyclones uplift more dust from the surface over the Middle East to the
central Asia in the middle troposphere. (2) Enhanced mid-latitude zonal
winds help transport more dust in the middle troposphere from the
central Asia to the Northwest China and thereafter an increase in
northerly winds over Northwest China propels dust southward to the TP.