Geoscience Reference
In-Depth Information
Fig. 4. Monthly contribution of anthropogenic aerosols to the total ADRF at surface
over Kanpur (in percentage) for 5 years. The annual mean (
±
SD) value is written over
each box.
surface ADRF are 64.1%, 65.3%, 64.6%, 63.7%, and 60.2% for 2001,
2002, 2003, 2004, and 2005, respectively. The large SD indicates the high
variability within a year. In 2005, the proportion of anthropogenic aerosols
to total aerosol surface forcing is lowest on annual scale. Further analysis
based on seasons reveals that the proportion in the pre-monsoon season
is lowest (37%) in 2004. In the years 2003 and 2005, the proportions are
very low (
42%) in the monsoon season also. In the winter season, the
anthropogenic contribution is uniform in all 5 years (88-89%), suggesting
insignificant inter-annual variation.
The monthly mean spatial distributions of anthropogenic surface and
atmospheric forcing over the IGB are illustrated in Fig. 5(a). The mean
annual clear-sky TOA, surface, and atmospheric anthropogenic forcing
in IGB are +0
<
9Wm
−
2
, respectively.
The major difference in the spatial distributions of the anthropogenic
surface forcing with total surface forcing is the persistent high values of
anthropogenic forcing in the eastern IGB throughout the year except July-
August, when monsoonal rain removes major fraction of aerosols from the
atmosphere. However, the anthropogenic surface forcing over the urban
centers like Kanpur and Delhi are still high (
±
6
.
8,
−
12
.
6
±
6
.
7, and +12
.
6
±
6
.
15 W m
−
2
), which shows
that even in the monsoon season, the washout of aerosols by monsoonal
rain is not so effective as compared to the eastern IGB. Immediately
after the monsoon season, anthropogenic surface forcing starts building
>−
