Role of meteorology and air pollution on fog conditions over Delhi during the peak winter 2024.

Severe air pollution and foggy conditions during winter are persistent challenges, pose significant health hazards, and disrupt daily routines worldwide. In this study, we have investigated the conditions favoring the prolonged fog events in Delhi during January 2024 using observations, back trajectories, and reanalysis datasets. Analysis of visibility observations reveals that foggy (54, 121, 139, and 372 half-hours of very dense, dense, moderate, and shallow fog, respectively) conditions persisted in Delhi for 46 % of the time during the study period.

Effectiveness of respiratory face masks in reducing acute PM pollution exposure during peak pollution period in Delhi.

The cities of North India, such as Delhi, face a significant public health threat from severe air pollution. Between October 2021 and January 2022, 79 % of Delhi's daily average PM (Particulate matter with an aerodynamic diameter ≤ 2.5 μm) values exceeded 100 μg/m (the permissible level being 60 μg/m as per Indian standards).

Changes in the thermodynamical profiles of the subsurface ocean and atmosphere induce cyclones to congregate over the Eastern Arabian Sea.

The Arabian Sea accounts for a small fraction of Tropical Cyclones-about 2% of the annual global mean. However, the damage they might inflict there and along its coastlines, which are thickly populated, is considerable. This study explores the influence of the changes in the vertical profiles of atmosphere and oceanic environment throughout the seasons of March-June (MAMJ) and October-December (OND) in clustering the cyclogenesis over the Eastern Arabian Sea (EAS) next to the Indian West coast in recent decades.

Sensitivity of WRF/Chem simulated PM2.5 to initial/boundary conditions and planetary boundary layer parameterization schemes over the Indo-Gangetic Plain.

The ability of a chemical transport model to simulate accurate meteorological and chemical processes depends upon the physical parametrizations and quality of meteorological input data such as initial/boundary conditions. In this study, weather research and forecasting model coupled with chemistry (WRF-Chem) is used to test the sensitivity of PM predictions to planetary boundary layer (PBL) parameterization schemes (YSU, MYJ, MYNN, ACM2, and Boulac) and meteorological initial/boundary conditions (FNL, ERA-Interim, GDAS, and NCMRWF) over Indo-Gangetic Plain (Delhi, Punjab, Haryana, Uttar Pradesh, and Rajasthan) during the winter period (December 2017 to January 2018). The aim is to select the model configuration for simulating PM which shows the lowest errors and best agreement with the observed data.

Southern hemisphere forced millennial scale Indian summer monsoon variability during the late Pleistocene.

Peninsular India hosts the initial rain-down of the Indian Summer Monsoon (ISM) after which winds travel further east inwards into Asia. Stalagmite oxygen isotope composition from this region, such as those from Belum Cave, preserve the vital signals of the past ISM variability. These archives experience a single wet season with a single dominant moisture source annually.

Drivers of air pollution variability during second wave of COVID-19 in Delhi, India.

To curb the 2nd wave of COVID-19 disease in April-May 2021, a night curfew followed by full lockdown was imposed over the National Capital Territory, Delhi. We have analyzed the observed variation in pollutants and meteorology, and role of local and transboundary emission sources during night-curfew and lockdown, as compared to pre-lockdown period and identical periods of 2020 lockdown as well as of 2018 and 2019. In 2021, concentration of pollutants (except O₃, SO₂, and toluene) declined by 4-16% during night-curfew as compared to the pre-lockdown period but these changes are not statistically significant.

Ionospheric perturbation during the South American total solar eclipse on 14th December 2020 revealed with the Chilean GPS eyeball.

The influence of the South American total solar eclipse of 14th December 2020 on the ionosphere is studied by using the continuous Chilean Global Positioning System (GPS) sites across the totality path. The totality path with eclipse magnitude 1.012 passed through the Villarrica (Lon.

Understanding the spatiotemporal variability and trends of surface ozone over India.

With rising anthropogenic activities, surface ozone levels have increased across different parts of the world including India. Previous studies have shown that surface ozone shows distinct characteristics across India but these results are based on isolated locations and any comprehensive and spatiotemporally consistent study about surface ozone variability lacks thus far. Keeping these facts in mind, we utilize ground-based observations and reanalysis datasets to investigate spatiotemporal variations of surface ozone and its linkages with meteorology and precursors over Indian region.

Comparison of INSAT-3D retrieved total column ozone with ground-based and AIRS observations over India.

Ozone plays an important role in the thermal structure and chemical composition of the atmosphere. The present study compares the temporal and spatial distributions of Total Column Ozone (TCO) over the Indian sub-continent retrieved from a geostationary Indian National Satellite (INSAT-3D) and Atmospheric Infrared Sounder (AIRS). The INSAT-3D TCO values are also evaluated against the Dobson spectrophotometer observations at two locations.

Ionospheric monitoring with the Chilean GPS eyeball during the South American total solar eclipse on 2nd July 2019.

The impact of total solar eclipse of July 2, 2019 on the Ionosphere is studied using 24 Chilean GPS stations north-south of the totality path. The total solar eclipse passed through Coquimbo region from ~ 16:38 CLT (~ 20:38 UTC) to ~ 16:40 CLT (~ 20:40 UTC) and maximum eclipse was observed ~ 16:39 CLT (~ 20:39 UTC). The total electron content (TEC) derived from GPS signals shows peculiar features.

Projections of heat stress and associated work performance over India in response to global warming.

Summertime heat stress future projections from multi-model mean of 18 CMIP5 models show unprecedented increasing levels in the RCP 4.5 and RCP 8.5 emission scenarios over India.

Assessment of the environmental health of an ecologically sensitive, semi-enclosed, basin - A water quality modelling approach.

Semi-enclosed basins are environmentally dynamic and some of the most anthropogenically affected components of the coastal realm. They can reflect various environmental impacts, thus qualifying as natural laboratories to study these impacts. The Gulf of Khambhat (GoK) is such a system where analysis of in situ parameters indicated polluted conditions.

Human influence on sub-regional surface air temperature change over India.

Human activities have been implicated in the observed increase in Global Mean Surface Temperature. Over regional scales where climatic changes determine societal impacts and drive adaptation related decisions, detection and attribution (D&A) of climate change can be challenging due to the greater contribution of internal variability, greater uncertainty in regionally important forcings, greater errors in climate models, and larger observational uncertainty in many regions of the world. We examine the causes of annual and seasonal surface air temperature (TAS) changes over sub-regions (based on a demarcation of homogeneous temperature zones) of India using two observational datasets together with results from a multimodel archive of forced and unforced simulations.