This study estimates the ground-level PM10 concentration by effectively combining the Aerosols Optical Depth (AOD) from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite retrievals and ...Weather Research and Forecasting Model coupled with Chemistry (WRF-Chem). The model simulates typical dust storm events 17th-22nd April 2010 and 05th–10th May 2010 which has severely affected air quality in North and Northwestern India. The satellite retrievals shows high AOD (>1.0) over Indo Gangetic Plains and nearby Thar Desert. The model captures the spatial pattern of AOD very well however, it underestimates high aerosol loading in comparision to MODISAOD. The modeled AOD (MODELAOD) shows an underestimation by 37% with MODISAOD over the study region. Therefore, the WRF-Chem model Particulate Matter (PM10) and MODELAOD are scaled using satellite MODISAOD to provide a better estimation of the particulate pollution. The results shows better estimation, trend and correlation (R = 0.83) of the PM10 with hourly observations at Delhi monitoring station and a Mean Bias (MB) of 61 μg/m3 during the satellite overpass time. The comparison of estimated PM with daily averaged observations of PM10 from Central Pollution Control Board (CPCB) at stations of Jaipur, Jodhpur, Kota, and Delhi showed a strong agreement with an correlation of (R) of 0.81, 0.70, 0.77 and 0.78, respectively.
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•High-resolution WRF-Chem model applied to simulate PM10 over India.•Underestimation of PM10 improved using scaling-method for dust episodes.•The estimated scaled-up PM correlated well with the observational data.
In this study, the aerosol behavior during two contradictory events, i.e., dust storm (DS) and Diwali (DW) has been studied over Jaipur. The aerosol particle number concentration shows distinct ...features between DS and DW events. The total ANC was found minimum during DS while maximum during DW. The 24 h mean of total ANC was 9.15 × 10
4
(±7.71 × 10
4
) and 5.38 × 10
5
(±3.73 × 10
5
particles/l) during DS and DW, respectively. The total ANC increases from 7.78 × 10
4
to 5.32 × 10
5
and 3.52 × 10
5
to 1.70 × 10
6
particles/l in 24 h during DS and DW, respectively. In DS, the ANC in coarse mode (2 < particle diameter < 20 μm) is significantly high while in DW, the ANC in fine mode (0.3 < particle diameter < 2 μm) exhibits higher concentration. During dust episode, a significant change in ANC (3.0 × 10
3
to 1.12 × 10
5
particles/l) was observed for the particle of size range in 2.0–20 μm with a slight increase in particles number concentration (7.48 × 10
4
to 4.20 × 10
5
particles/l) in 0.3–2.0 μm range is also observed. During DS, the fine and coarse mode particles increased 4.61 and 36.44 times while during DW, it increased 3.83 and 0.95 times, respectively. The relatively high particle levels during DW are attributed for two reasons: local emissions due to burning of fire crackers and meteorological conditions, i.e., low wind speeds and low mixing-layer heights lead to relatively high particle concentrations.
Multi-year Aerosol Robotic Network (AERONET) direct Sun retrieved and inversion algorithm derived aerosol products at a semi-arid, urban site, Jaipur (26.90° N, 75.80° E) and island observing site, ...Maldives Climate Observatory-Hanimaadhoo (MCO-Hanimaadhoo, 6.74° N, 73.17° E) are analysed to investigate heterogeneity in aerosol optical and microphysical properties. Results reveal the existence of a large seasonal diversity in the frequency distributions of aerosol optical depth (AOD
500
nm
, AOD
1020
nm
) and Ångström exponent (AE
440-870
nm
) during different seasons at Jaipur and MCO-Hanimaadhoo. These are indicative of the advection of different aerosol types (viz., black carbon (BC) aerosol, organic aerosol, sulfate particle, dust, sea salt, nitrate particle, and mixtures thereof) from a variety of production mechanisms influenced by strong seasonal changes of anthropogenic activities as well as modulations induced by the climatic condition. The cumulative frequency analysis of the single scattering albedo (SSA) difference (i.e. ΔSSA = SSA
440
nm
- SSA
1020
nm
) shows that at Jaipur ΔSSA is predominantly negative (around 88% days) while at MCO-Hanimaadhoo it is positive (around 74% days). The positive and negative values of ΔSSA are respectively linked to a stronger absorption by BC mixed anthropogenic pollution aerosols at 1020 nm and to a stronger absorption by mineral dust containing iron oxide at 440 nm. The spectral behaviour of SSA, thus, facilitates investigation of the existence of iron oxide or BC in aerosols. The 'Bivariate Kernel density' plots of SSA versus fine-mode fraction (FMF) of AOD
440
nm
/AE
440-870
nm
reveal that at Jaipur the aerosol ensemble consists of coarse-mode particles (AE and FMF cluster in the range 0.2-0.4), a dominant category along with significant fine-mode and much less mixed category. At MCO-Hanimaadhoo fine-mode particle category (with FMF and AE cluster in the range 0.90-0.95 and 1.2-1.6 respectively) is the only dominant category. The persisting log-normal bimodal feature in aerosol volume size distribution (AVSD) is observed both at Jaipur and MCO-Hanimaadhoo. The modal volume concentration of coarse-mode aerosol decreases from FMF of AOD
675
nm
= 0.25 (inherently belonging to the coarse-mode regime) to FMF of AOD
675
nm
= 0.95 (inherently belonging to the fine-mode regime). This transformation in coarse-to fine-mode volume concentration is associated with a steady rise in AE
440-874
nm
supporting this changeover.
Fog occurs more frequently over urban areas than rural areas. It may occur due to increased air pollution emanating from variety of sources in the urban areas. The increased pollution levels may lead ...to the atmospheric reactions resulting into the formation of secondary pollutants that may also lead to the needed cloud condensation nuclei. Northern regions of India experience severe foggy conditions during the winter period (November–January) each year. In this study, we have simultaneously measured the particulate mass concentration (0.23 µm to 20 µm), meteorological parameters and atmospheric visibility in Mega city Delhi during a winter month of the years 2007– 2008 in order to have an improved understanding of their role in fog formation. The effects of aerosols on fog formation are discussed through an analysis of trends in fog frequency and comparison with meteorological parameters, and visibility as an indicator of aerosol load. This satisfies the precondition for using these relations. The association between the meteorological parameters (visibility, depression temperature) and air pollutants are examined. The Windows software SPSS (version 17.0) is used to fit a linear regression model. The model explained the variation in visibility due to depression temperature and aerosols load.
The present analysis deals with one of the most debated aspects of the studies on the upper troposphere/lower stratosphere (UTLS), namely the budget of water vapour (H2O) at the tropical tropopause. ...Within the French project “Multiscale water budget in the upper troposphere and lower stratosphere in the TROpics” (TRO-pico), a global-scale analysis has been set up based on space-borne observations, models and assimilation techniques. The MOCAGE-VALENTINA assimilation tool has been used to assimilate the Aura Microwave Limb Sounder (MLS) version 3.3 H2O measurements within the 316–5 hPa range from August 2011 to March 2013 with an assimilation window of 1 h. Diagnostics based on observations minus analysis and forecast are developed to assess the quality of the assimilated H2O fields. Comparison with an independent source of H2O measurements in the UTLS based on the space-borne Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) observations and with meteorological ARPEGE analyses is also shown. Sensitivity studies of the analysed fields have been performed by (1) considering periods when no MLS measurements are available and (2) using H2O data from another MLS version (4.2). The studies have been performed within three different spaces in time and space coincidences with MLS (hereafter referred to as MLS space) and MIPAS (MIPAS space) observations and with the model (model space) outputs and at three different levels: 121 hPa (upper troposphere), 100 hPa (tropopause) and 68 hPa (lower stratosphere) in January and February 2012. In the MLS space, the analyses behave consistently with the MLS observations from the upper troposphere to the lower stratosphere. In the model space, the analyses are wetter than the reference atmosphere as represented by ARPEGE and MLS in the upper troposphere (121 hPa) and around the tropopause (100 hPa), but are consistent with MLS and MIPAS in the lower stratosphere (68 hPa). In the MIPAS space, the sensitivity and the vertical resolution of the MIPAS data set at 121 and 100 hPa prevent assessment of the behaviour of the analyses at 121 and 100 hPa, particularly over intense convective areas as the South American, the African and the Maritime continents but, in the lower stratosphere (68 hPa), the analyses are very consistent with MIPAS. Sensitivity studies show the improvement on the H2O analyses in the tropical UTLS when assimilating space-borne measurements of better quality, particularly over the convective areas.
In the present study, a first systematic evaluation and analysis of long-term (2009-2020) gridded datasets (0. 5^{\circ}\times 0.625) of total columnar ozone (TCO) from Modern-Era Retrospective ...Analysis for Research and Applications, version 2 (MERRA-2TCO) is carried out over the Indian subcontinent. The \text{MERRA} -2_{\text{TCO}} is first validated with observed (\text{IMD}_{\text{TCO}}) and then further compared with Atmospheric Infrared Sounder (\text{AIRS}_{\text{TCO}}) satellite dataset. For an in-depth comparison and statistical analysis, the dataset has been segregated into seven distinct regions, i.e. Western Himalaya (WH), Northeast (NE), North Central (NC), Northwest (NW), West Peninsula India (WPI), East Peninsula India (EPI), and South Peninsula India (SPI). Descriptive statistics (NMSE, FB, R, FA2 and d) reveals significant correlation of MERRA -2_{\text{TCO}} with \text{IMD}_{\text{TCO}} over Delhi (NMSE=0.0013, FB=-0.029) and Varanasi (NMSE=0.0008, FB=-0.014) cities. Further, a comparison of \text{MERRA} -2_{\text{TCO}} with \text{AIRS}_{\text{TCO}} represents the NMSE values ranging from 0.0023-0.0047 DU and a correlation coefficient of 0.62-0.87 in different regions of India. In support of Brewer's circulation pattern, an increasing strong shift of columnar ozone from low (SPI) to high (WH) latitudinal regions in annual variation (2009-2020) is observed. Our finding indicate that the MERRA-2 ozone dataset can be effectively used for ozone air quality studies over the Indian regions and the analysis may highlight the necessity for independent, reliable, consistent, and accurate ozone observations.
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