Atmospheric aerosols play an important role in the formation of warm clouds by acting as efficien... more Atmospheric aerosols play an important role in the formation of warm clouds by acting as efficient cloud condensation nuclei (CCN) and their interactions are believed to cool the Earth-Atmosphere system (‘first indirect effect or Twomey effect’) in a highly uncertain manner compared to the other forcing agents. Here we demonstrate using long-term (2003–2016) satellite observations (NASA’s A-train satellite constellations) over the northern Indian Ocean, that enhanced aerosol loading (due to anthropogenic emissions) can reverse the first indirect effect significantly. In contrast to Twomey effect, a statistically significant increase in cloud effective radius (CER, µm) is observed with respect to an increase in aerosol loading for clouds having low liquid water path (LWP
Surface, column and vertically resolved variations of physical and optical properties of atmosphe... more Surface, column and vertically resolved variations of physical and optical properties of atmospheric aerosol over Hyderabad, a tropical urban location in central India are explored on the basis of ground based and satellite retrieved data. Annual mean aerosol optical depth (τ) observed with Microtops sun-photometer is 0.61 ± 0.07 and seasonally it varied from 0.71 ± 0.06 in pre-monsoon to 0.55 ± 0.05 in winter. Aerosol types are categorized based on Ångström exponent (α) and τ relations; revealed that the study region is dominated by mixed type (MT) aerosol followed by urban/industrial aerosols under high τ (HUI) category. A consistent diurnal variation of black carbon (BC) is observed irrespective of seasonal variation with annual BC mass concentration is found to be 9.7 ± 1.9 µg m-3. During Telangana Survey day, which was the least pollutant day showed a reduction of 75% BC concentration during day time in comparison to five years average values, indicating the influence of anthropogenic effect over Hyderabad. Vertical information's on aerosol are analyzed using Cloud Aerosol Lidar Pathfinder Satellite Observations (CALIPSO) and ground based Lidar (LAMP) data. LAMP data analysis shows a significant elevated aerosol layer up to 4 km during pre-monsoon while aerosols are confined below 3 km during post-monsoon and winter. Long term CALIPSO observations revealed that during postmonsoon to winter, the study area is dominated (~60%) by 'urban' aerosol; while during pre-monsoon period ~75% of the aerosol type belongs to 'dusty mix' category. A decline in short wave flux at the top of the atmosphere (0.66 Wm-2 yr-1) is observed, as revealed by long term Clouds and Earths Radiant Energy System (CERES) data analysis with higher decline rate observed in winter (1 Wm-2 yr-1) followed by pre-monsoon (0.8 Wm-2 yr-1).
The Indian summer monsoon rainfall contributes about 75% of the total annual rainfall and exhibit... more The Indian summer monsoon rainfall contributes about 75% of the total annual rainfall and exhibits considerable interannual variations. The agricultural economy of the country depends mainly on the monsoon rainfall. The long-range forecast of the monsoon rainfall is, therefore of significant importance in agricultural planning and other economic activities of the country. There are various parameters which influence the amount of rainfall received during the monsoon. Some of the important parameters considered by the Indian Meteorological Department (IMD) for the study of monsoon are Outgoing Longwave Radiation (OLR), moisture content of the atmosphere, zonal wind speed, low level vorticity, pressure gradient etc. Compared to the Long Period Average (LPA) value of rain fall, the country as a whole received higher amount of rainfall in June, 2013 (34% more than LPA). The same month showed considerable decrease next year as the amount of rainfall received was around 43% less compared to LPA. This drastic difference of monsoon prompted to study the behaviour of some of the monsoon relevant parameters. In this study we have considered five atmospheric parameters as the indicators of monsoon behaviour namely vertical relative humidity, OLR, aerosol optical depth (AOD), wind at 850 hPa and mean sea level pressure (MSLP). In the initial analysis of weekly OLR difference for year 2013 and 2014 shows positive values in the month of May over northwestern parts of India (region of heat low). This should result in a weaker monsoon in 2014. This is substantiated by the rainfall data received for various stations over India. Inference made based on the analysis of RH profiles coupled with AOD values is in agreement with the rainfall over the corresponding stations. This contribution has been peer-reviewed.
In the present study we have attempted to characterize aerosols using their optical properties ov... more In the present study we have attempted to characterize aerosols using their optical properties over a tropical urban location of Hyderabad, India. We have analyzed three years of in-situ data on aerosol absorption from Aethalometer and scattering from Nephelometer measurements. Satellite based absorption measurements from ozone monitoring instrument, absorbing aerosol index are also analyzed to investigate the role of long range transport of dust. Further, the Cloud-Aerosol Lidar Pathfinder Satellite Observations (CALIPSO) data is used to study the vertical extent of aerosol particles as well as their sphericity using its particulate depolarization ratio. The study revealed that irrespective of seasonal variation, local anthropogenic fossil fuel aerosols form the predominant aerosol type over this site. Biomass/dust aerosols in their pure form are not present during the study period; however the spread of frequency distribution of scattering Angstrom exponent and absorption Angstrom exponent suggested their possible existence in mixed condition with local anthropogenic aerosols. The analysis of columnar aerosol absorption data during pre-monsoon period showed the dominance of UV absorbing dust aerosols in the study region. CALIPSO data analysis over study area showed that majority aerosols are confined within 2 km from the surface during winter while in pre-monsoon particles are distributed throughout the profile (~6 km) with extinction coefficient varying between 0.1-0.2 km-1. As the season shift from winter to pre-monsoon a change in sphericity of particle is observed. Cluster mean trajectory analysis revealed that during premonsoon majority of air mass movements (~68%) are from western side passing through dust source region like Persian Gulf and Thar Desert before entering into Indian region. During post-monsoon (~70%) and winter (~65%), majority of the air masses are coming from northwest and northeast side of the study area where biomass burning is quite frequent during this period.
h i g h l i g h t s ADRE at TOA during winter is À11.7 Wm À2 and in pre-monsoon it is À5.5 Wm À2 ... more h i g h l i g h t s ADRE at TOA during winter is À11.7 Wm À2 and in pre-monsoon it is À5.5 Wm À2 . An enhancement of atmospheric forcing of~50 Wm À2 is observed during pre-monsoon. Heating rate due to biomass burning and dust storm on local atmosphere are~2.26 and 2.08 K day À1 , respectively.
Dust storms are normally considered to be natural hazards. During such events, dust aerosol is lo... more Dust storms are normally considered to be natural hazards. During such events, dust aerosol is loaded into the atmosphere, directly reducing visibility and effectively reflecting solar radiation back to space. In the present study, an intense dust storm was monitored during the first week of June 2010 using Moderate Resolution Imaging Spectroradiometer (MODIS) Terra and Aqua data over the Indian region. A dust cloud was detected using a combination of MODIS reflective and emissive channels and moving trace/spread monitored by its multi-temporal data. The MODIS Terra-derived aerosol optical depth at 550 nm (AOD 550 ) and the aerosol index (AI) obtained from the Ozone Monitoring Instrument (OMI) were used in conjunction with National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis wind fields for the monitoring of dust clouds. The study reveals that the movement of a high concentration of dust clouds coincided with the NCEP/NCAR reanalysis meridional and zonal wind fields (>8 m s −1 ) at pressure levels of 700 hPa. The Cloud-Aerosol Lidar Pathfinder Satellite Observations (CALIPSOs) that derive vertical feature mask images also suggested that the vertical extent of the dust aerosol layer was at a height of about 6 km over northern India on 2 June 2010. The roles of long-range transport of dust over the entire Gangetic plane are analysed using back trajectories from the National Oceanic and Atmospheric Administration (NOAA) Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model. Back trajectory analysis suggests that dust clouds moving over long distances entered from the western side of India on 1 June 2010.
Dust storm events over the Arabian Sea (AS) have been detected using Moderate Resolution
Imaging ... more Dust storm events over the Arabian Sea (AS) have been detected using Moderate Resolution Imaging Spectroradiometer (MODIS) data. Shortwave Aerosol Radiative Forcing (SWARF) due to dust storm is estimated using synchronous observation of Clouds and Earth’s Energy System (CERES) and MODIS aerosol optical depth (AOD). Study established a relationship between them as SWARF = −39.12 × AOD − 16.53 (0.4 ≤ AOD ≤ 4.0) with r 2 = 0.96. The devel- oped relation can be used for quick, independent estimation of instantaneous SWARF for dust storm over the AS. The relationship can be used to explore the possible effect of dust on climate modulation in this region.
Tropospheric ozone (TO) has been derived from the Aura/Ozone Monitoring
Instrument (OMI) and the ... more Tropospheric ozone (TO) has been derived from the Aura/Ozone Monitoring Instrument (OMI) and the Aura/Microwave Limb Sounder (MLS) over the Indian sub-continent region using a tropospheric ozone residual (TOR) technique. The TO was initially retrieved at a horizontal spatial resolution following that of the Aura/ MLS (300 km), which has a lower horizontal spatial resolution than that of the Aura/ OMI (25 km). To overcome the limitations imposed by data at a lower spatial resolution, we have introduced a 2D rectangular interpolation (RI) algorithm for effective resampling of data to higher horizontal spatial resolutions. The performance of this algorithm has been evaluated by comparison against existing standard techniques such as nearest neighbourhood (NN) and kriging interpolation as well as comparison against in situ ozonesonde observations. Gridded TO estimates were subsequently generated for the region of interest at 25, 50, and 100 km horizontal spatial resolutions for further study.
Aerosol haze degrades visibility by the process of absorption and scattering of aerosols. In the ... more Aerosol haze degrades visibility by the process of absorption and scattering of aerosols. In the present study an attempt has been made to characterize the physical and optical properties of aerosols during a haze event on 29 March 2012 and assess its implication on radiative forcing. In this context representative clear (2 March 2012) and normal (19 March 2012) days were identified in terms of their Aerosol Optical Depth (AOD) loading over Hyderabad. On the hazy day, a huge spread of haze was observed over the eastern part of India by MODerate resolution Imaging Spectroradiometer (MODIS) on board Terra satellite which is represented by high Aerosol Optical Depth at 550 nm. In–situ observations on hazy day showed an enhancement of columnar AOD500 respectively by 4.5 and 1.8 fold in comparison to clear and normal days. Significant increase in the scattering coefficient and a moderate enhancement of Single Scattering Albedo (SSA) are observed on hazy day compared to normal day. Study also showed that Diffuse–to–Direct– beam irradiance Ratio (DDR) had increased 4.5 times at 496.6 nm spectral band on hazy day. LIDAR (LIght Detection And Ranging) observations on hazy night showed a threefold increase in aerosol backscattering below the Atmospheric Boundary Layer (ABL) compared to normal representative night. The hazy day is characterized by large negative surface forcing (–87.82 W m–2 ) when compared to normal day (–53.90 W m–2 ). A large positive enhancement of atmospheric forcing of 30.56 W m–2 is observed on hazy day compared to normal day.
A seven channel Aethalometer (AE31) was used to measure the black carbon (BC) mass concentrations... more A seven channel Aethalometer (AE31) was used to measure the black carbon (BC) mass concentrations at the premises of National Remote Sensing Centre (NRSC), Hyderabad during the period 2010-2012 to characterize BC temporal concentration and source identification. Diurnal variation of BC shows varied amplitude of BC mass concentration with peak during mornings and nights with minimum during afternoons of all the study periods (2010)(2011)(2012). Highest absorption coefficient at 520 nm (b abs = 38.79 Mm -1 ) was observed during post monsoon season of 2011 and lowest value observed (b abs = 22.06 Mm -1 ) during winter season of 2010. Absorption Angstrom Exponents (AAE) were analysed in the lower (370 nm-520 nm) and higher wavelength (590 nm-950 nm) region to explain the BC origin. A few number of days with high contrasting AAE in lower and higher wavelengths, responsible for the bio fuel generated BC were found during the study period. Study revealed that majority of the study period, AAE values are around 1, attributed to mainly vehicular emission. Highest AAE of 1.57 (370 nm-950 nm) was observed on 4 January, 2012. Three representative days of pre-monsoon, post-monsoon and winter were considered for analyzing daily variations of AAE in conjunction with back trajectories from NOAA HYSPLIT model to confirm the source of BC as biomass burning origin.
Dust storms are normally considered to be natural hazards. During such events, dust aerosol is lo... more Dust storms are normally considered to be natural hazards. During such events, dust aerosol is loaded into the atmosphere, directly reducing visibility and effectively reflecting solar radiation back to space. In the present study, an intense dust storm was monitored during the first week of June 2010 using Moderate Resolution Imaging Spectroradiometer (MODIS) Terra and Aqua data over the Indian region. A dust cloud was detected using a combination of MODIS reflective and emissive channels and moving trace/spread monitored by its multi-temporal data. The MODIS Terra-derived aerosol optical depth at 550 nm (AOD 550 ) and the aerosol index (AI) obtained from the Ozone Monitoring Instrument (OMI) were used in conjunction with National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis wind fields for the monitoring of dust clouds. The study reveals that the movement of a high concentration of dust clouds coincided with the NCEP/NCAR reanalysis meridional and zonal wind fields (>8 m s −1 ) at pressure levels of 700 hPa. The Cloud-Aerosol Lidar Pathfinder Satellite Observations (CALIPSOs) that derive vertical feature mask images also suggested that the vertical extent of the dust aerosol layer was at a height of about 6 km over northern India on 2 June 2010. The roles of long-range transport of dust over the entire Gangetic plane are analysed using back trajectories from the National Oceanic and Atmospheric Administration (NOAA) Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model. Back trajectory analysis suggests that dust clouds moving over long distances entered from the western side of India on 1 June 2010.
Atmospheric aerosols play an important role in the formation of warm clouds by acting as efficien... more Atmospheric aerosols play an important role in the formation of warm clouds by acting as efficient cloud condensation nuclei (CCN) and their interactions are believed to cool the Earth-Atmosphere system (‘first indirect effect or Twomey effect’) in a highly uncertain manner compared to the other forcing agents. Here we demonstrate using long-term (2003–2016) satellite observations (NASA’s A-train satellite constellations) over the northern Indian Ocean, that enhanced aerosol loading (due to anthropogenic emissions) can reverse the first indirect effect significantly. In contrast to Twomey effect, a statistically significant increase in cloud effective radius (CER, µm) is observed with respect to an increase in aerosol loading for clouds having low liquid water path (LWP
Surface, column and vertically resolved variations of physical and optical properties of atmosphe... more Surface, column and vertically resolved variations of physical and optical properties of atmospheric aerosol over Hyderabad, a tropical urban location in central India are explored on the basis of ground based and satellite retrieved data. Annual mean aerosol optical depth (τ) observed with Microtops sun-photometer is 0.61 ± 0.07 and seasonally it varied from 0.71 ± 0.06 in pre-monsoon to 0.55 ± 0.05 in winter. Aerosol types are categorized based on Ångström exponent (α) and τ relations; revealed that the study region is dominated by mixed type (MT) aerosol followed by urban/industrial aerosols under high τ (HUI) category. A consistent diurnal variation of black carbon (BC) is observed irrespective of seasonal variation with annual BC mass concentration is found to be 9.7 ± 1.9 µg m-3. During Telangana Survey day, which was the least pollutant day showed a reduction of 75% BC concentration during day time in comparison to five years average values, indicating the influence of anthropogenic effect over Hyderabad. Vertical information's on aerosol are analyzed using Cloud Aerosol Lidar Pathfinder Satellite Observations (CALIPSO) and ground based Lidar (LAMP) data. LAMP data analysis shows a significant elevated aerosol layer up to 4 km during pre-monsoon while aerosols are confined below 3 km during post-monsoon and winter. Long term CALIPSO observations revealed that during postmonsoon to winter, the study area is dominated (~60%) by 'urban' aerosol; while during pre-monsoon period ~75% of the aerosol type belongs to 'dusty mix' category. A decline in short wave flux at the top of the atmosphere (0.66 Wm-2 yr-1) is observed, as revealed by long term Clouds and Earths Radiant Energy System (CERES) data analysis with higher decline rate observed in winter (1 Wm-2 yr-1) followed by pre-monsoon (0.8 Wm-2 yr-1).
The Indian summer monsoon rainfall contributes about 75% of the total annual rainfall and exhibit... more The Indian summer monsoon rainfall contributes about 75% of the total annual rainfall and exhibits considerable interannual variations. The agricultural economy of the country depends mainly on the monsoon rainfall. The long-range forecast of the monsoon rainfall is, therefore of significant importance in agricultural planning and other economic activities of the country. There are various parameters which influence the amount of rainfall received during the monsoon. Some of the important parameters considered by the Indian Meteorological Department (IMD) for the study of monsoon are Outgoing Longwave Radiation (OLR), moisture content of the atmosphere, zonal wind speed, low level vorticity, pressure gradient etc. Compared to the Long Period Average (LPA) value of rain fall, the country as a whole received higher amount of rainfall in June, 2013 (34% more than LPA). The same month showed considerable decrease next year as the amount of rainfall received was around 43% less compared to LPA. This drastic difference of monsoon prompted to study the behaviour of some of the monsoon relevant parameters. In this study we have considered five atmospheric parameters as the indicators of monsoon behaviour namely vertical relative humidity, OLR, aerosol optical depth (AOD), wind at 850 hPa and mean sea level pressure (MSLP). In the initial analysis of weekly OLR difference for year 2013 and 2014 shows positive values in the month of May over northwestern parts of India (region of heat low). This should result in a weaker monsoon in 2014. This is substantiated by the rainfall data received for various stations over India. Inference made based on the analysis of RH profiles coupled with AOD values is in agreement with the rainfall over the corresponding stations. This contribution has been peer-reviewed.
In the present study we have attempted to characterize aerosols using their optical properties ov... more In the present study we have attempted to characterize aerosols using their optical properties over a tropical urban location of Hyderabad, India. We have analyzed three years of in-situ data on aerosol absorption from Aethalometer and scattering from Nephelometer measurements. Satellite based absorption measurements from ozone monitoring instrument, absorbing aerosol index are also analyzed to investigate the role of long range transport of dust. Further, the Cloud-Aerosol Lidar Pathfinder Satellite Observations (CALIPSO) data is used to study the vertical extent of aerosol particles as well as their sphericity using its particulate depolarization ratio. The study revealed that irrespective of seasonal variation, local anthropogenic fossil fuel aerosols form the predominant aerosol type over this site. Biomass/dust aerosols in their pure form are not present during the study period; however the spread of frequency distribution of scattering Angstrom exponent and absorption Angstrom exponent suggested their possible existence in mixed condition with local anthropogenic aerosols. The analysis of columnar aerosol absorption data during pre-monsoon period showed the dominance of UV absorbing dust aerosols in the study region. CALIPSO data analysis over study area showed that majority aerosols are confined within 2 km from the surface during winter while in pre-monsoon particles are distributed throughout the profile (~6 km) with extinction coefficient varying between 0.1-0.2 km-1. As the season shift from winter to pre-monsoon a change in sphericity of particle is observed. Cluster mean trajectory analysis revealed that during premonsoon majority of air mass movements (~68%) are from western side passing through dust source region like Persian Gulf and Thar Desert before entering into Indian region. During post-monsoon (~70%) and winter (~65%), majority of the air masses are coming from northwest and northeast side of the study area where biomass burning is quite frequent during this period.
h i g h l i g h t s ADRE at TOA during winter is À11.7 Wm À2 and in pre-monsoon it is À5.5 Wm À2 ... more h i g h l i g h t s ADRE at TOA during winter is À11.7 Wm À2 and in pre-monsoon it is À5.5 Wm À2 . An enhancement of atmospheric forcing of~50 Wm À2 is observed during pre-monsoon. Heating rate due to biomass burning and dust storm on local atmosphere are~2.26 and 2.08 K day À1 , respectively.
Dust storms are normally considered to be natural hazards. During such events, dust aerosol is lo... more Dust storms are normally considered to be natural hazards. During such events, dust aerosol is loaded into the atmosphere, directly reducing visibility and effectively reflecting solar radiation back to space. In the present study, an intense dust storm was monitored during the first week of June 2010 using Moderate Resolution Imaging Spectroradiometer (MODIS) Terra and Aqua data over the Indian region. A dust cloud was detected using a combination of MODIS reflective and emissive channels and moving trace/spread monitored by its multi-temporal data. The MODIS Terra-derived aerosol optical depth at 550 nm (AOD 550 ) and the aerosol index (AI) obtained from the Ozone Monitoring Instrument (OMI) were used in conjunction with National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis wind fields for the monitoring of dust clouds. The study reveals that the movement of a high concentration of dust clouds coincided with the NCEP/NCAR reanalysis meridional and zonal wind fields (>8 m s −1 ) at pressure levels of 700 hPa. The Cloud-Aerosol Lidar Pathfinder Satellite Observations (CALIPSOs) that derive vertical feature mask images also suggested that the vertical extent of the dust aerosol layer was at a height of about 6 km over northern India on 2 June 2010. The roles of long-range transport of dust over the entire Gangetic plane are analysed using back trajectories from the National Oceanic and Atmospheric Administration (NOAA) Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model. Back trajectory analysis suggests that dust clouds moving over long distances entered from the western side of India on 1 June 2010.
Dust storm events over the Arabian Sea (AS) have been detected using Moderate Resolution
Imaging ... more Dust storm events over the Arabian Sea (AS) have been detected using Moderate Resolution Imaging Spectroradiometer (MODIS) data. Shortwave Aerosol Radiative Forcing (SWARF) due to dust storm is estimated using synchronous observation of Clouds and Earth’s Energy System (CERES) and MODIS aerosol optical depth (AOD). Study established a relationship between them as SWARF = −39.12 × AOD − 16.53 (0.4 ≤ AOD ≤ 4.0) with r 2 = 0.96. The devel- oped relation can be used for quick, independent estimation of instantaneous SWARF for dust storm over the AS. The relationship can be used to explore the possible effect of dust on climate modulation in this region.
Tropospheric ozone (TO) has been derived from the Aura/Ozone Monitoring
Instrument (OMI) and the ... more Tropospheric ozone (TO) has been derived from the Aura/Ozone Monitoring Instrument (OMI) and the Aura/Microwave Limb Sounder (MLS) over the Indian sub-continent region using a tropospheric ozone residual (TOR) technique. The TO was initially retrieved at a horizontal spatial resolution following that of the Aura/ MLS (300 km), which has a lower horizontal spatial resolution than that of the Aura/ OMI (25 km). To overcome the limitations imposed by data at a lower spatial resolution, we have introduced a 2D rectangular interpolation (RI) algorithm for effective resampling of data to higher horizontal spatial resolutions. The performance of this algorithm has been evaluated by comparison against existing standard techniques such as nearest neighbourhood (NN) and kriging interpolation as well as comparison against in situ ozonesonde observations. Gridded TO estimates were subsequently generated for the region of interest at 25, 50, and 100 km horizontal spatial resolutions for further study.
Aerosol haze degrades visibility by the process of absorption and scattering of aerosols. In the ... more Aerosol haze degrades visibility by the process of absorption and scattering of aerosols. In the present study an attempt has been made to characterize the physical and optical properties of aerosols during a haze event on 29 March 2012 and assess its implication on radiative forcing. In this context representative clear (2 March 2012) and normal (19 March 2012) days were identified in terms of their Aerosol Optical Depth (AOD) loading over Hyderabad. On the hazy day, a huge spread of haze was observed over the eastern part of India by MODerate resolution Imaging Spectroradiometer (MODIS) on board Terra satellite which is represented by high Aerosol Optical Depth at 550 nm. In–situ observations on hazy day showed an enhancement of columnar AOD500 respectively by 4.5 and 1.8 fold in comparison to clear and normal days. Significant increase in the scattering coefficient and a moderate enhancement of Single Scattering Albedo (SSA) are observed on hazy day compared to normal day. Study also showed that Diffuse–to–Direct– beam irradiance Ratio (DDR) had increased 4.5 times at 496.6 nm spectral band on hazy day. LIDAR (LIght Detection And Ranging) observations on hazy night showed a threefold increase in aerosol backscattering below the Atmospheric Boundary Layer (ABL) compared to normal representative night. The hazy day is characterized by large negative surface forcing (–87.82 W m–2 ) when compared to normal day (–53.90 W m–2 ). A large positive enhancement of atmospheric forcing of 30.56 W m–2 is observed on hazy day compared to normal day.
A seven channel Aethalometer (AE31) was used to measure the black carbon (BC) mass concentrations... more A seven channel Aethalometer (AE31) was used to measure the black carbon (BC) mass concentrations at the premises of National Remote Sensing Centre (NRSC), Hyderabad during the period 2010-2012 to characterize BC temporal concentration and source identification. Diurnal variation of BC shows varied amplitude of BC mass concentration with peak during mornings and nights with minimum during afternoons of all the study periods (2010)(2011)(2012). Highest absorption coefficient at 520 nm (b abs = 38.79 Mm -1 ) was observed during post monsoon season of 2011 and lowest value observed (b abs = 22.06 Mm -1 ) during winter season of 2010. Absorption Angstrom Exponents (AAE) were analysed in the lower (370 nm-520 nm) and higher wavelength (590 nm-950 nm) region to explain the BC origin. A few number of days with high contrasting AAE in lower and higher wavelengths, responsible for the bio fuel generated BC were found during the study period. Study revealed that majority of the study period, AAE values are around 1, attributed to mainly vehicular emission. Highest AAE of 1.57 (370 nm-950 nm) was observed on 4 January, 2012. Three representative days of pre-monsoon, post-monsoon and winter were considered for analyzing daily variations of AAE in conjunction with back trajectories from NOAA HYSPLIT model to confirm the source of BC as biomass burning origin.
Dust storms are normally considered to be natural hazards. During such events, dust aerosol is lo... more Dust storms are normally considered to be natural hazards. During such events, dust aerosol is loaded into the atmosphere, directly reducing visibility and effectively reflecting solar radiation back to space. In the present study, an intense dust storm was monitored during the first week of June 2010 using Moderate Resolution Imaging Spectroradiometer (MODIS) Terra and Aqua data over the Indian region. A dust cloud was detected using a combination of MODIS reflective and emissive channels and moving trace/spread monitored by its multi-temporal data. The MODIS Terra-derived aerosol optical depth at 550 nm (AOD 550 ) and the aerosol index (AI) obtained from the Ozone Monitoring Instrument (OMI) were used in conjunction with National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis wind fields for the monitoring of dust clouds. The study reveals that the movement of a high concentration of dust clouds coincided with the NCEP/NCAR reanalysis meridional and zonal wind fields (>8 m s −1 ) at pressure levels of 700 hPa. The Cloud-Aerosol Lidar Pathfinder Satellite Observations (CALIPSOs) that derive vertical feature mask images also suggested that the vertical extent of the dust aerosol layer was at a height of about 6 km over northern India on 2 June 2010. The roles of long-range transport of dust over the entire Gangetic plane are analysed using back trajectories from the National Oceanic and Atmospheric Administration (NOAA) Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model. Back trajectory analysis suggests that dust clouds moving over long distances entered from the western side of India on 1 June 2010.
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Papers by subin jose
Imaging Spectroradiometer (MODIS) data. Shortwave Aerosol Radiative Forcing (SWARF)
due to dust storm is estimated using synchronous observation of Clouds and Earth’s Energy
System (CERES) and MODIS aerosol optical depth (AOD). Study established a relationship
between them as SWARF = −39.12 × AOD − 16.53 (0.4 ≤ AOD ≤ 4.0) with r 2 = 0.96. The devel-
oped relation can be used for quick, independent estimation of instantaneous SWARF for dust
storm over the AS. The relationship can be used to explore the possible effect of dust on climate
modulation in this region.
Instrument (OMI) and the Aura/Microwave Limb Sounder (MLS) over the Indian
sub-continent region using a tropospheric ozone residual (TOR) technique. The TO
was initially retrieved at a horizontal spatial resolution following that of the Aura/
MLS (300 km), which has a lower horizontal spatial resolution than that of the Aura/
OMI (25 km). To overcome the limitations imposed by data at a lower spatial
resolution, we have introduced a 2D rectangular interpolation (RI) algorithm for
effective resampling of data to higher horizontal spatial resolutions. The performance
of this algorithm has been evaluated by comparison against existing standard techniques such as nearest neighbourhood (NN) and kriging interpolation as well as
comparison against in situ ozonesonde observations. Gridded TO estimates were
subsequently generated for the region of interest at 25, 50, and 100 km horizontal
spatial resolutions for further study.
has been made to characterize the physical and optical properties of aerosols during a haze event on 29 March 2012 and
assess its implication on radiative forcing. In this context representative clear (2 March 2012) and normal (19 March 2012)
days were identified in terms of their Aerosol Optical Depth (AOD) loading over Hyderabad. On the hazy day, a huge
spread of haze was observed over the eastern part of India by MODerate resolution Imaging Spectroradiometer (MODIS)
on board Terra satellite which is represented by high Aerosol Optical Depth at 550 nm. In–situ observations on hazy day
showed an enhancement of columnar AOD500 respectively by 4.5 and 1.8 fold in comparison to clear and normal days.
Significant increase in the scattering coefficient and a moderate enhancement of Single Scattering Albedo (SSA) are
observed on hazy day compared to normal day. Study also showed that Diffuse–to–Direct– beam irradiance Ratio (DDR)
had increased 4.5 times at 496.6 nm spectral band on hazy day. LIDAR (LIght Detection And Ranging) observations on hazy
night showed a threefold increase in aerosol backscattering below the Atmospheric Boundary Layer (ABL) compared to
normal representative night. The hazy day is characterized by large negative surface forcing (–87.82 W m–2
) when
compared to normal day (–53.90 W m–2
). A large positive enhancement of atmospheric forcing of 30.56 W m–2
is observed
on hazy day compared to normal day.
Imaging Spectroradiometer (MODIS) data. Shortwave Aerosol Radiative Forcing (SWARF)
due to dust storm is estimated using synchronous observation of Clouds and Earth’s Energy
System (CERES) and MODIS aerosol optical depth (AOD). Study established a relationship
between them as SWARF = −39.12 × AOD − 16.53 (0.4 ≤ AOD ≤ 4.0) with r 2 = 0.96. The devel-
oped relation can be used for quick, independent estimation of instantaneous SWARF for dust
storm over the AS. The relationship can be used to explore the possible effect of dust on climate
modulation in this region.
Instrument (OMI) and the Aura/Microwave Limb Sounder (MLS) over the Indian
sub-continent region using a tropospheric ozone residual (TOR) technique. The TO
was initially retrieved at a horizontal spatial resolution following that of the Aura/
MLS (300 km), which has a lower horizontal spatial resolution than that of the Aura/
OMI (25 km). To overcome the limitations imposed by data at a lower spatial
resolution, we have introduced a 2D rectangular interpolation (RI) algorithm for
effective resampling of data to higher horizontal spatial resolutions. The performance
of this algorithm has been evaluated by comparison against existing standard techniques such as nearest neighbourhood (NN) and kriging interpolation as well as
comparison against in situ ozonesonde observations. Gridded TO estimates were
subsequently generated for the region of interest at 25, 50, and 100 km horizontal
spatial resolutions for further study.
has been made to characterize the physical and optical properties of aerosols during a haze event on 29 March 2012 and
assess its implication on radiative forcing. In this context representative clear (2 March 2012) and normal (19 March 2012)
days were identified in terms of their Aerosol Optical Depth (AOD) loading over Hyderabad. On the hazy day, a huge
spread of haze was observed over the eastern part of India by MODerate resolution Imaging Spectroradiometer (MODIS)
on board Terra satellite which is represented by high Aerosol Optical Depth at 550 nm. In–situ observations on hazy day
showed an enhancement of columnar AOD500 respectively by 4.5 and 1.8 fold in comparison to clear and normal days.
Significant increase in the scattering coefficient and a moderate enhancement of Single Scattering Albedo (SSA) are
observed on hazy day compared to normal day. Study also showed that Diffuse–to–Direct– beam irradiance Ratio (DDR)
had increased 4.5 times at 496.6 nm spectral band on hazy day. LIDAR (LIght Detection And Ranging) observations on hazy
night showed a threefold increase in aerosol backscattering below the Atmospheric Boundary Layer (ABL) compared to
normal representative night. The hazy day is characterized by large negative surface forcing (–87.82 W m–2
) when
compared to normal day (–53.90 W m–2
). A large positive enhancement of atmospheric forcing of 30.56 W m–2
is observed
on hazy day compared to normal day.