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A rising source of outdoor emissions in northwestern India is crop residue burning, occurring after the monsoon (kharif ) and winter (rabi) crop harvests. In particular, post-monsoon rice residue burning, which occurs annually from October to November and is linked to increasing mechanization, coincides with meteorological conditions that enhance short-term air quality degradation. Here we examine the Global Fire Emissions Database (GFED), whose bottom-up emissions are based on the 500-m burned area product, MCD64A1, derived from Moderate Resolution Imaging Spectroradiometer (MODIS) observations. Using a household survey from 2016, we find that MCD64A1 tends to underestimate burned area in many surveyed villages, leading to poor representation of small, scattered fires and consequent spatial biases in model results. To more accurately allocate such small fires and resolve sub-village heterogeneity, we use an experimental hybrid MODIS-Landsat method (ModL2T) to map burned area at 30-m spatial resolution, which results in 44±21% higher burned area than MCD64A1 and up to 105±52% increase in dry matter emissions over GFEDv4s. In our validation and assessments, we find that ModL2T performs better relative to MCD64A1 in terms of bias and omission error, but may introduce commission error due to conflation of burning with harvest and still underestimate burned area due to Landsat's coarse temporal resolution (every 16 days). We conclude that while MODIS and Landsat provide more than two decades worth of observations, their spatio-temporal resolution is too coarse to overcome several region-specific challenges: small median landholding size (1-3 ha), quick harvest-to-sowing turnover period, prevalence of partial burning, and increasing haziness. To further constrain agricultural fire emissions in northwestern India and improve model estimates of associated public health impacts, integration of finer resolution imagery, as well as better understanding of the spatial patterns in burn rates, burn practices, and fuel loading, is requisite.

Persistent and widespread fog affects several densely populated and agriculturally fertile basins around the world. Dense and polluted fog is especially known to impact transportation, air quality, and public health. Here we report a striking observation of holes in fog over urban areas in satellite imagery. The extent of fog holes appear highly correlated with city populations in fog‐prevalent regions of Asia, Europe, and the United States. We find the highest frequency and largest extent of fog holes over Delhi along with suppressed fog fraction, amidst increased fog occurrence over the Indo‐Gangetic Plains, based on 17 years of satellite data (2000–2016). This apparent urban heat impact is characterized in sharp urban‐rural gradients in surface temperatures and fog thickness. Urban heating seems to have already amplified the long‐term fog decline in Europe and the United States and should be assessed over regions undergoing urban expansion including India, where no previous linkages are reported between urban heating and fog.

Since the Green Revolution in the mid-1960s, a widespread transition to a rice–wheat rotation in the Indian state of Punjab has led to steady increases in crop yield and production. After harvest of the summer monsoon rice crop, the burning of excess crop residue in Punjab from October to November allows for rapid preparation of fields for sowing of the winter wheat crop. Here we use daily satellite remote sensing data to show that the timing of peak post-monsoon fire activity in Punjab and regional aerosol optical depth (AOD) has shifted later by approximately two weeks in Punjab from 2003 to 2016. This shift is consistent with delays of 11–15 d in the timing of maximum greenness of the monsoon crop and smaller delays of 4–6 d in the timing of minimum greenness during the monsoon-to-winter crop transition period. The resulting compression of the harvest-to-sowing period coincides with a 42% increase in total burning and 55% increase in regional AOD. Potential drivers of these trends include agricultural intensification and a recent groundwater policy that delays sowing of the monsoon crop. The delay and amplification of burning into the late post-monsoon season suggest greater air quality degradation and public health consequences across the densely populated Indo-Gangetic Plain.

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International audienceA new hot filament chemical vapor deposition with direct current plasma assistance (DC HFCVD) chamber has been designed for an intense nucleation and subsequent growth of diamond films on Si(100).Growth process as well as the If(V) characteristics of the DC discharge are reported. Gas phase constituents activation was obtained by a stable glow discharge between two grid electrodes coupled with two sets of parallel hot filaments settled in-between and polarised at the corresponding plasma potential. The sample is negatively biased with a small 10-15 V extraction potential with respect to the cathode grid.Such design allows to create a high density of both ions and radicals that are extracted and focussed onto the surface of the sample.The current density onto the sample can be finely tuned independently of the primary plasma.A homogeneous plasma fully covering the sample surface is visualized. Consequently, a high-density nucleation (>1010 cm-2) occurs

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