Geoscience Reference
In-Depth Information
4. Summary
In this study, we assessed the anthropogenic contribution to the ADRF
in the IGB and studied its spatial and temporal distribution. The Indo-
Gangetic haze induces mean annual forcing of
−
2
.
9
±
4
.
3,
−
25
.
5
±
12
.
9, and
9Wm
−
2
in clear-sky condition. Over Kanpur, the anthropogenic
aerosols account for more than 76% of the total aerosol mass, and contribute
to 60-65% of the total ADRF at surface annually. On regional scale,
the contributions of anthropogenic (
+22
.
6
±
11
.
49%) aerosols
are almost equal, suggesting the importance of natural aerosols in this
region. The surface cooling is highest in the winter and pre-monsoon
seasons, whereas the spatial heterogeneity is highest in the pre-monsoon
and monsoon seasons. Less spatial heterogeneity in the winter and post-
monsoon seasons suggest that the anthropogenic pollution is quite uniform
throughout the IGB. Anthropogenic contribution is persistently found to be
high in the eastern IGB (
∼
51%) and natural (
∼
70%). Mean annual clear-sky TOA, surface, and
atmospheric forcing due to anthropogenic aerosols in the IGB are +0
>
±
6
.
8,
9Wm
−
2
, respectively.
The atmosphere is getting heated by more than 0.9 K day
−
1
in the
winter and pre-monsoon seasons. Anthropogenic aerosols contribute 55%
to the mean (
−
12
.
6
±
6
.
7, and +12
.
6
±
6
.
19 K day
−
1
over IGB.
Persistently, large reduction of surface solar irradiance would affect the
radiative balance at the surface by decreasing either the latent heat flux
through suppressed evaporation or sensible heat flux or both. Such large
aerosol loading in the atmosphere would also alter the cloud microphysics
through indirect effect. Hence there is a need to understand the effect of the
aerosols on the regional hydrological cycle in much better way, which would
require more
±
SD) annual heating rate of 0
.
64
±
0
.
in situ
measurements to reduce the present-day uncertainty
of the ADRF.
Acknowledgments
The authors acknowledge the support of Department of Science and
Technology. The efforts of PIs of Kanpur AERONET site are appreciated.
References
1. J. T. Houghton
et al.
,
Climate Change 2001: The Scientific Basis
(Cambridge
University Press, 2001), 881 pp.
2. V. Ramanathan
et al.
,
J. Geophys. Res.
28
(2001) 28371.
