Vikram Sarabhai Space Centre

About: Vikram Sarabhai Space Centre is a facility organization based out in Thiruvananthapuram, India. It is known for research contribution in the topics: Aerosol & Ultimate tensile strength. The organization has 2092 authors who have published 3058 publications receiving 47975 citations. The organization is also known as: VSSC.

Altitude profiles of aerosol BC, derived from aircraft measurements over an inland urban location in India

Abstract: [1] Altitude profiles of aerosol black carbon (BC) in the atmospheric boundary layer and above it were measured for the first time in India, over the urban location Hyderabad, onboard an aircraft during two consecutive days of February 2004. The profiles on both the days were consistent, and showed a rapid decrease in BC concentration within the boundary up to ∼550 m AGL (where convective activity prevailed). Sodar measurements from the nearby location revealed the mean boundary layer height to be ∼600 m during the flight period. The decrease in BC above the boundary layer was quite weak up to ∼2.2 km AGL.

Chemical, microphysical, and radiative effects of Indian Ocean aerosols

Abstract: Received 19 April 2002; revised 2 August 2002; accepted 6 August 2002; published 14 December 2002. [1] Extensive and long-term multistation measurements of aerosol properties and radiative fluxes were carried out in the haze plume off the South Asian continent. These experiments are carried out at Kaashidhoo Climate Observatory (KCO) (4.95� N, 73.5� E), Minicoy (8.5� N, 73.0� E), and Trivandrum (8.5� N, 77.0� E). In addition, the top of the atmosphere fluxes were measured simultaneously by the CERES radiation budget instrument. Long-term observations (more than 15 years) over Trivandrum show that there is a gradual increase in aerosol visible optical depth from � 0.2 in 1986 to � 0.4 in 1999. Pre- and post-monsoon aerosol characteristics are examined to study the seasonal variations. The impact of aerosols on short-wave radiation budget is estimated using direct observations of solar radiation using several independent ground-based radiometers and satellite data as well as from modeled aerosol properties. It was observed that ‘‘excess absorption’’ is not needed to model diffuse fluxes. The lower atmospheric heating due to absorbing aerosols was as high as � 20 W m � 2 which translates to a heating rate perturbation of � 0.5� K/day. The effect of aerosol mixing state (internally and externally) on aerosol forcing appears to be negligible. A sensitivity study of the effect of aerosols over land in contrast to that over the ocean shows an enhancement in lower atmosphere heating by about 40% simultaneous with a reduction of � 33% in surface cooling. Increasing sea-surface winds increase aerosol cooling due to increased sea salt aerosol concentrations, which can partly offset the heating effect due to absorbing aerosols. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 1610 Global Change: Atmosphere (0315, 0325); 1704 History of Geophysics: Atmospheric sciences; 4801 Oceanography: Biological and Chemical: Aerosols (0305); KEYWORDS: aerosols, radiative forcing, climate, chemical composition

Temporal heterogeneity in aerosol characteristics and the resulting radiative impact at a tropical coastal station -Part 1: Microphysical and optical properties

Abstract: . In Part 1 of this two-part paper, we present the results of extensive and collocated measurements of the columnar and near-surface (in the well mixed region) properties of atmospheric aerosol particles at a tropical coastal location, Trivandrum (8.55° N; 76.97° E), located close to the southwest tip of Indian peninsula. These are used to evolve average, climatological pictures of the optical and microphysical properties and to delineate the distinct changes associated with the contrasting monsoon seasons as well as the transition from one season to the other. Our observations show a dramatic change in the columnar aerosol optical depth (AOD) spectra, being steep during winter monsoon season (WMS, months of December through March) and becoming quite flat during summer monsoon season (SMS, June through September). The derived Angstrom exponent (α) decreases from a mean value of 1.1±0.03 in WMS to 0.32±0.02 in SMS, signifying a change in columnar aerosol size spectrum from an accumulation mode dominance in WMS to a coarse mode dominance in SMS. The composite aerosols near the surface follow suit with the share of the accumulation mode to the total mass concentration decreasing from ~70% to 34% from WMS to SMS. The overall mass burden also decreases in tandem. The changes in α are well correlated to those in the accumulation fraction of the mass concentration. Long-term measurements of the concentration of aerosol black carbon (BC), show prominent annual variations, with its mean value decreasing from as high as 6 μg m−3 in WMS to 2 μg m−3 in SMS. Correspondingly, its mass mixing ratio to the composite aerosols comes down from 11% to 4%. The changes in AOD and α are significantly positively correlated to those of BC concentration. The columnar properties are, in general well associated with the features near the surface. The implications of these changes to the optical properties and single scattering albedo and the resulting impact on direct radiative forcing are examined in the companion paper (Part 2).