Abstract:
The influences of the springtime northern Indian biomass burning are shown for the
first time over the central Himalayas by using three years (2007–2009) of surface and
space based observations along with a radiative transfer model. Near‐surface ozone,
black carbon (BC), spectral aerosol optical depths (AODs) and the meteorological
parameters are measured at a high altitude site Nainital (29.37°N, 79.45°E, 1958 m amsl)
located in the central Himalayas. The satellite observations include the MODIS
derived fire counts and AOD (0.55 mm), and OMI derived tropospheric column NO₂,
ultraviolet aerosol index and single scattering albedo. MODIS fire counts and BC
observations are used to identify the fire‐impacted periods (372 h during 2007–2009) and
hence the induced enhancements in surface BC, AOD (0.5 mm) and ozone are estimated
to be 1802 ng m−³ (∼145%), 0.3 (∼150%) and 19 ppbv (∼34%) respectively. Large
enhancements (53–100%) are also seen in the satellite derived parameters over a 2° × 2°
region around Nainital. The present analysis highlights the northern Indian biomass
burning induced cooling at the surface (−27 W m ̵²) and top of the atmosphere (−8 W m ̵²)
in the lesser polluted high altitude regions of the central Himalayas. This cooling leads to
an additional atmospheric warming of 19 W m ̵² and increases the lower atmospheric
heating rate by 0.8 K day ̵¹ . These biomass burning induced changes over the
central Himalayan atmosphere during spring may also lead to enhanced short‐wave
absorption above clouds and might have an impact on the monsoonal rainfall.
