TY - JOUR
T1 - Long-term (2008–2018) aerosol properties and radiative effect at high-altitude sites over western trans-Himalayas
AU - Dumka, U. C.
AU - Ningombam, Shantikumar S.
AU - Kaskaoutis, D. G.
AU - Madhavan, B. L.
AU - Song, H. J.
AU - Angchuk, Dorje
AU - Jorphail, Sonam
N1 - Publisher Copyright:
© 2020 Elsevier B.V.
PY - 2020/9/10
Y1 - 2020/9/10
N2 - Analysis of the climatology of aerosol properties is performed over Hanle (4500 m) and Merak (4310 m), two remote-background sites in the western trans-Himalayas, based on eleven years (2008–2018) of sun/sky radiometer (POM-01, Prede) measurements. The two sites present very similar atmospheric conditions and aerosol properties allowing us to examine them as continuous single-data series. The annual average aerosol optical depth at 500 nm (AOD500) is 0.04 ± 0.03, associated with an Ångström exponent (AE440 – 870) of 0.58 ± 0.35 and a single scattering albedo (SSA500) of 0.95 ± 0.05. AOD500 exhibits higher values in May (~0.07) and lower in winter (~0.03), while AE400 – 870 minimizes in spring, indicating influence by coarse-mode dust aerosols, either emitted regionally or long-range transported. The de-convolution of AOD500 into fine and coarse modes justifies the aerosol seasonality and sources, while the marginal diurnal variation in all aerosol properties reveals a weak influence from local sources, except for some few aerosol episodes. The aerosol-volume size distribution presents a mode value at ~10 μm with secondary peaks at accumulation (~ 2 μm) and fine modes (~0.03 μm) and low variability between the seasons. A classification of the aerosol types based on the fine-mode fraction (FMF) vs. SSA500 relationship reveals the dominance of aerosols in the FMF range of 0.4–0.6, characterized as mixed (39%), followed by fine aerosols with high scattering efficiency (26%), while particles related to dust contribute ~21%, with low fractions of fine-absorbing aerosols (~13%). The aerosol radiative forcing (ARF) estimates reveal a small cooling effect at the top of the atmosphere (−1.3 Wm−2), while at the surface, the ARF ranges from −2 Wm−2 to −6 Wm−2 on monthly basis. The monthly-mean atmospheric radiative forcing (~1 to 4 Wm−2) leads to heating rates of 0.04 to 0.13 K day−1. These ARF values are higher than the global averages and may cause climate implications over the trans-Himalayan region.
AB - Analysis of the climatology of aerosol properties is performed over Hanle (4500 m) and Merak (4310 m), two remote-background sites in the western trans-Himalayas, based on eleven years (2008–2018) of sun/sky radiometer (POM-01, Prede) measurements. The two sites present very similar atmospheric conditions and aerosol properties allowing us to examine them as continuous single-data series. The annual average aerosol optical depth at 500 nm (AOD500) is 0.04 ± 0.03, associated with an Ångström exponent (AE440 – 870) of 0.58 ± 0.35 and a single scattering albedo (SSA500) of 0.95 ± 0.05. AOD500 exhibits higher values in May (~0.07) and lower in winter (~0.03), while AE400 – 870 minimizes in spring, indicating influence by coarse-mode dust aerosols, either emitted regionally or long-range transported. The de-convolution of AOD500 into fine and coarse modes justifies the aerosol seasonality and sources, while the marginal diurnal variation in all aerosol properties reveals a weak influence from local sources, except for some few aerosol episodes. The aerosol-volume size distribution presents a mode value at ~10 μm with secondary peaks at accumulation (~ 2 μm) and fine modes (~0.03 μm) and low variability between the seasons. A classification of the aerosol types based on the fine-mode fraction (FMF) vs. SSA500 relationship reveals the dominance of aerosols in the FMF range of 0.4–0.6, characterized as mixed (39%), followed by fine aerosols with high scattering efficiency (26%), while particles related to dust contribute ~21%, with low fractions of fine-absorbing aerosols (~13%). The aerosol radiative forcing (ARF) estimates reveal a small cooling effect at the top of the atmosphere (−1.3 Wm−2), while at the surface, the ARF ranges from −2 Wm−2 to −6 Wm−2 on monthly basis. The monthly-mean atmospheric radiative forcing (~1 to 4 Wm−2) leads to heating rates of 0.04 to 0.13 K day−1. These ARF values are higher than the global averages and may cause climate implications over the trans-Himalayan region.
KW - Aerosol optical properties
KW - Aerosol radiative forcing
KW - Aerosol size distribution
KW - Aerosol types
KW - High-altitude site
KW - Trans-Himalayas
UR - http://www.scopus.com/inward/record.url?scp=85085235432&partnerID=8YFLogxK
U2 - 10.1016/j.scitotenv.2020.139354
DO - 10.1016/j.scitotenv.2020.139354
M3 - Article
C2 - 32470663
AN - SCOPUS:85085235432
SN - 0048-9697
VL - 734
JO - Science of the Total Environment
JF - Science of the Total Environment
M1 - 139354
ER -