Sudipta Sarkar

Crop Residue Burning in Northern India: Increasing Threat to Greater India

Crop residue burning (CRB) is a recurring problem, during October–November, in the northwestern regions (Punjab, Haryana, and western Uttar Pradesh) of India. The emissions from the CRB source regions spread in all directions through long-range transport mechanisms, depending upon the meteorological conditions. In recent years, numerous studies have been carried out dealing with the impact of CRB on the air quality of Delhi and surrounding areas, especially in the Indo-Gangetic Basin (also referred to as Indo-Gangetic Plain). In this paper, we present detailed analysis using both satelliteand ground-based sources, which show an increasing impact of CRB over the eastern parts of the Indo-Gangetic Basin and also over parts of central and southern India. The increasing trends of finer black carbon particles and greenhouse gases have accelerated since the year 2010 onward, which is confirmed by the observation of different wavelength dependent aerosol properties. Our study shows an increased risk to ambient air quality and an increased spatiotemporal extent of pollutants in recent years, from CRB, which could be a severe health threat to the population of these regions. Plain Language Summary This paper shows from multiple evidence increasing effects of crop residue burning on the rest of India. This is the first work of its kind that treats this issue over rest of India at depth based on data from multiple sources and shows the ever increasing menace of biomass burning to air pollution.

Toward Long-Term Aquatic Science Products from Heritage Landsat Missions

This paper aims at generating a long-term consistent record of Landsat-derived remote sensing reflectance (Rrs) products, which are central for producing downstream aquatic science products (e.g., concentrations of total suspended solids). The products are derived from Landsat-5 and Landsat-7 observations leading to Landsat-8 era to enable retrospective analyses of inland and nearshore coastal waters. In doing so, the data processing was built into the SeaWiFS Data Analysis System (SeaDAS) followed by vicariously calibrating Landsat-7 and -5 data using reference in situ measurements and near-concurrent ocean color products, respectively. The derived Rrs products are then validated using (a) matchups using the Aerosol Robotic Network (AERONET) data measured by in situ radiometers, i.e., AERONET-OC, and (b) ocean color products at select sites in North America. Following the vicarious calibration adjustments, it is found that the overall biases in Rrs products are significantly reduced. The root-mean-square errors (RMSE), however, indicate noticeable uncertainties due to random and systematic noise. Long-term (since 1984) seasonal Rrs composites over 12 coastal and inland systems are further evaluated to explore the utility of Landsat archive processed via SeaDAS. With all the qualitative and quantitative assessments, it is concluded that with careful algorithm developments, it is possible to discern natural variability in historic water quality conditions using heritage Landsat missions. This requires the changes in Rrs exceed maximum expected uncertainties, i.e., 0.0015 [1/sr], estimated from mean RMSEs associated with the matchups and intercomparison analyses. It is also anticipated that Landsat-5 products will be less susceptible to uncertainties in turbid waters with Rrs(660) > 0.004 [1/sr], which is equivalent of ~1.2% reflectance. Overall, end-users may utilize heritage Rrs products with “fitness-for-purpose” concept in mind, i.e., products could be valuable for one application but may not be viable for another. Further research should be dedicated to enhancing atmospheric correction to account for non-negligible near-infrared reflectance in CDOM-rich and extremely turbid waters.

Methane and carbon monoxide emissions associated with aliso canyon ground storage blowout

Satellite sensors are now capable of monitoring various total atmospheric gas concentrations and meteorological parameters at different pressure levels. These sensors provide information at spatial and temporal resolutions, which can be used to alert people about possible exposure to hazardous gases, if the concentrations of these gases are found to exceed normal concentrations. Aliso Canyon is a ground storage facility located in California, where there was blow out of a well and intense gas release in the atmosphere that was first detected on 23 October 2015. In this paper, we have used satellite data to monitor methane (CH4) and carbon monoxide (CO) along with other relevant meteorological parameters. Our results show enhancement of CO and CH4 concentrations around Aliso Canyon associated with the gas leaks with the blow out.

June 19 2015 Rainfall Event Over Mumbai: Some Observational Analysis

Some of the major metropolitan centers in the world are highly susceptible to flash floods and major disruptions, owing to sudden and excessive rainfall events. The city of Mumbai, India’s financial capital, suffered one such event on 19 June, 2015. This was a second event of such nature, following the landmark event of 26 July, 2005. Such extreme rainfall events are often brought about by certain rapidly developing, local disturbances, which if actively monitored, may be provide important information that can be of great use for early warning to civic authorities and emergency planners. In this paper, we have analyzed a number of different meteorological and remotely sensed parameters, a few days before the actual event, to track the development and eventual culmination of a “perfect storm” that affected Mumbai and left the city tattered. We show how regional upper layer disturbance patterns are developed, induced by warming of sea-surface temperature (SST) and sustained by instability in the atmospheric boundary layers to quickly develop into massive cyclonic storms.