Aerosol black carbon quantification in the central Indo-Gangetic Plain: Seasonal heterogeneity and source apportionment

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2019EA000620

On the Relationship Between Aerosol and Boundary Layer Height in Summer in China Under Different Thermodynamic Conditions

A better understanding of land cover/land use changes (LCLUC) and their interactions with the atmospheric environment is essential for the sustainable management of natural resources, environmental protection, air quality, agricultural planning and food security. The 15 papers published in this focus issue showcase a variety of studies relating to drivers and impacts of LCLUC and air pollution in different South/Southeast Asian (S/SEA) countries. This synthesis article, in addition to giving context to the articles in this focus issue, also reviews the broad linkages between population, LCLUC and air pollution. Additionally, we identify knowledge gaps and research priorities that are essential in addressing air pollution issues in the region. We conclude that for effective pollution mitigation in S/SEA countries, quantifying drivers, sources and impacts of pollution need a thorough data analysis through ground-based instrumentation, models and integrated research approaches. We also stress the need for the development of sustainable technologies and strengthening the scientific and resource management communities through capacity building and training activities to address air pollution issues in S/SEA countries.

https://iopscience.iop.org/article/10.1088/1748-9326/aa9c5d/pdf

Land cover, land use changes and air pollution in Asia: a synthesis

Exceedances and trends of particulate matter (PM2.5) in five Indian megacities.

Black carbon aerosol in India: A comprehensive review of current status and future prospects

Boundary layer dynamics play an important role in determining precipitation structure during convective processes. The radar reflectivity profiles which depend on the sixth moment of rain drop size distribution (DSD) can be employed to sense the precipitation processes. The height profiles of DSD significantly depend on the vertical wind velocity. The observations with a micro rain radar (MRR), an FMCW radar, over Kolkata, have been utilized to study the drop size distribution and its relationship with radar reflectivity at Ka-band. A sharp decrease of radar reflectivity in the height range 1–2 km corresponds to an increase of downdraft velocity observed around the same height range. This indicates that the increased downdraft causes breakup of rain drops into smaller sizes. The split in the Doppler spectrum, known as aliasing effect, is most prominent near the boundary layer height and has been employed to estimate downward wind velocity.

Rain Radar Studies of Boundary Layer Dynamics at a Tropical Location

Raindrop size distribution (DSD) parameters need to be estimated to determine rainfall from radar measurements of backscattered signals in the precipitating medium and to study microphysics of precipitation under varying atmospheric conditions. A technique is proposed to estimate the DSD parameters from Global Precipitation Measurement (GPM) dual-frequency products at Ku and Ka bands, which has been validated with ground-based disdrometer measurements obtained during the five-year period 2014–2018 over a tropical location, Kolkata (<inline-formula> <tex-math notation="LaTeX">$22^{\circ }54^{\prime} \text{N}$ </tex-math></inline-formula>, <inline-formula> <tex-math notation="LaTeX">$88^{\circ }35^{\prime} \text{E}$ </tex-math></inline-formula>), India. The present method yields the three parameters of the DSD model in terms of a gamma function, namely, intercept (<inline-formula> <tex-math notation="LaTeX">$N_{0}$ </tex-math></inline-formula>), shape (<inline-formula> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>), and slope (<inline-formula> <tex-math notation="LaTeX">$\Lambda$ </tex-math></inline-formula>). Based on a proposed optimization technique, the most appropriate <inline-formula> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>–<inline-formula> <tex-math notation="LaTeX">$\Lambda $ </tex-math></inline-formula> relationship is determined during a GPM satellite pass to obtain the DSD parameters. The derived parameters have yielded mass-weighted mean diameter (<inline-formula> <tex-math notation="LaTeX">$D_{m}$ </tex-math></inline-formula>) data that show much better agreement with ground-based DSD measurements than that provided by GPM dual-frequency precipitation radar (DPR) product. This method has also been used to obtain the height profiles of DSD that broadly correlate with ground-based micro rain radar (MRR) observations, showing how DSD varies at different altitudes. The present results demonstrate that the proposed technique is effective in obtaining three-parameter DSDs over a tropical location and offers a useful method to study the microstructure of rain using space-borne radar.

Three-Parameter Rain Drop Size Distributions From GPM Dual-Frequency Precipitation Radar Measurements: Techniques and Validation With Ground-Based Observations

Atmospheric gravity waves are generated by the interplay of earth's gravity and buoyancy effect on an air parcel. The zonal and meridional wind and temperature perturbations observed in the troposphere and stratosphere exhibit signature of gravity waves. These gravity waves can originate from different excitation mechanisms such as deep convection in the tropics, orographic effects and various meteorological disturbances. We have studied the gravity wave generated due to an intense tropical cyclone named, Phailin, using radio occultation data from COSMIC over the Indian region. The radio occultation data are used to obtain the vertical profiles of atmospheric refractivity that bear the manifestation of gravity waves at different heights. The dry temperature and water vapor pressure from the refractivity profile yield the potential energy and the water vapor intrusion due to gravity waves in the lower stratosphere (18–25 km) during the tropical cyclone.

Atmospheric Gravity Wave Features Related to Stratospheric Moistening During Tropical Cyclones

Atmospheric gravity waves are generated by the interplay of earth's gravity and buoyancy effect on an air parcel. The zonal and meridional wind and temperature perturbation observed in the troposphere and stratosphere exhibits signature of gravity waves. The seasonal analysis of gravity wave activity has been made for the present tropical location, Kolkata $(22.5726^{\circ}\mathrm{N}, 88.3639^{\circ}\mathrm{E})$ using radiosonde data. Gravity wave generated due to intense tropical cyclone Aila has been investigated using COSMIC radio occultation data over the Indian region. The gravity wave energy calculated from temperature profile perturbations shows a significant enhancement during the cyclone which is accompanied by a low outgoing long wave radiation (OLR) indicating the presence of strong convective activities. An intrusion of water vapor into the lower stratosphere over the cyclone affected region is detected from Stratosphere-troposphere Processes And their Role in Climate data (SPARC).

Soumyajyoti Jana

Papers

Rain Radar Studies of Boundary Layer Dynamics at a Tropical Location

Three-Parameter Rain Drop Size Distributions From GPM Dual-Frequency Precipitation Radar Measurements: Techniques and Validation With Ground-Based Observations

Atmospheric Gravity Wave Features Related to Stratospheric Moistening During Tropical Cyclones

Gravity Wave Behavior Associated With Strong Convective Activities During Tropical Cyclone Aila