Vimlesh Pant

The atmospheric global electric circuit: An overview

Research work in the area of the Global Electric Circuit (GEC) has rapidly expanded in recent years mainly through observations of lightning from satellites and ground-based networks and observations of optical emissions between cloud and the ionosphere. After reviewing this progress, we critically examine the role of various generators of the currents flowing in the lower and upper atmosphere and supplying currents to the GEC. The role of aerosols and cosmic rays in controlling the GEC and linkage between climate, solar-terrestrial relationships and the GEC has been briefly discussed. Some unsolved problems in this area are reported for future investigations.

Observed interannual variability of near-surface salinity in the Bay of Bengal

An in situ gridded data of salinity, comprising Argo and CTD profiles, has been used to study the interannual variability of near-surface salinity (within 30 m from sea surface) in the Bay of Bengal (BoB) during the years 2005-2013. In addition to the broad agreement with earlier studies on the north-to-south gradient of surface salinity and general features of seasonal variability of salinity, the data also revealed few episodes of enhanced freshening in the BoB. The observations showed distinct anomalous low salinity (< 2 psu) waters in the northern BoB during June-February of the years 2006-2007 (Y67), 2011-2012 (Y12), and 2012-2013 (Y23). The anomalous freshening during these years showed similar life cycle, such as, it starts in the northern BoB during July-September of current summer and extends up to February-March of next winter with a southward propagation. Analysis showed that the oceanic and atmospheric conditions associated with positive Indian Ocean Dipole (pIOD) lead to these freshening events, and IOD rather than El NiA±o/Southern Oscillation (ENSO) controls the interannual variability of salinity in the BoB. The mixed layer salt budget analysis indicated the dominant role of local fresh water flux (horizontal advection) on the observed salinity tendency during summer (winter) monsoon season. Enhanced precipitation associated with pIOD lead to enhanced freshening in northern BoB during June-September, which remained to this region with prevailing summer monsoon circulation. The weakening or absence of southward east India coastal current (EICC) during October-December of these freshening years trapped anomalous freshwater in the northern BoB. Key Points Anomalous freshening observed in BoB in 3 years Positive IOD initiate the freshening events in northern BoB Salt budget analysis resolve contributions from different processes © 2015. American Geophysical Union. All Rights Reserved.

Observed chlorophyll-a bloom in the southern Bay of Bengal during winter 2006–2007

The analysis of 6-year chlorophyll-a data provided by the Moderate Resolution Imaging Spectral (MODIS) radiometer revealed anomalous chlorophyll-a bloom in the southern Bay of Bengal during the winter 2006–2007. The plausible causative mechanisms for such a large chlorophyll-a during the winter 2006–2007 are analysed through surface wind field, surface net heat flux and sea surface height anomaly (SSHA) data. The chlorophyll-a bloom developed in November 2006 near the northern tip of Sumatra. It was intensified and propagated slowly westward during December 2006 to January 2007 and then weakened by February 2007. The combined effect of shallowing of thermocline and weakening of barrier layer due to anomalous westward propagating upwelling Rossby waves associated with the Indian Ocean Dipole (IOD) event and relatively strong wind field causing entrainment of subsurface nutrient-rich water to euphotic zone leads to the bloom in the southern Bay of Bengal.

Interannual variability of salinity profiles from Argo in the Bay of Bengal

A attempt has been made to understand the ground water quality by using the water quality index (WQI) in the mining region of Goa. WQI, a technique of rating water quality, is an effective tool to assess spatial and temporal changes in ground water quality. Forty five groundwater samples were collected from open and tube wells during summer, monsoon, post-monsoon and winter seasons. The groundwater samples were subjected to comprehensive physio-chemical analysis involving major cations (Ca2+, Mg2+, Na+, K+, Fe2++ ) anions ( HClO3-, Cl, SO4 2-, NO3-, F-, PO4 3-) besides general parameters (pH, EC, TDS, alkalinity, total hardness, color, turbidity). The water quality index rating was calculated to quantify overall water quality for human consumption. For calculating WQI 10 parameters, namely pH, TDS, total hardness, chloride, nitrate, turbidity, fluoride, iron, calcium hardness, magnesium hardness were considered. The values of WQI have been affected mainly by the concentration of dissolved ions (F, NO, Ca and Mg) in ground water. Concentration of dissolved solids found to be more during monsoon season. It may be due more seepage and movement of ground water due to excessive rainfall there. The values of WQI of the samples were found in the range of 8-12 for all the seasons and considered to be in the very good category.U Heat Island is a more threatening meteorological phenomenon in the longer summer tropical cities with already critical thermal regime than in the longer winter temperate cities. Further, the population growth in the tropical megacities is far greater than their counterpart temperate cities. The present paper enquires the changing trends in the urban climates. Cities are recognized as urban heat islands because their temperatures are higher by 3°C to 9°C in comparison to the temperatures of the surrounding rural areas. This thermal differential is generally proportional to the city size and morphology. Larger is the city size and more diverse are its residential, industrial and commercial functions, larger and higher is its heat dome. Urban Heat Island has become a major environmental issue particularly in view of rapid urban sprawl in the developing countries. Urban Heat Islands are the nuclei of global warming and climate change. Urban Heat Island is not a cognizable problem of towns and small cities. It is a matter of great concern to the urban planners, environmentalists and citizens of the large cities, particularly the million and megacities. However, this problem is assuming a serious dimension in a fast emerging megacity of Hyderabad. The present paper estimates heat island intensity of Hyderabad. In the wake of its rapidly growing economy, size and population, the city has experienced a population growth from 1.79 million in 1971 to 7.74 million in 2011. The corresponding built-up area has recorded a growth from 298.5 sq.km. to a sprawling 851 sq.km. The paper enquires the adverse impact of this built-up growth on the daytime as well as nocturnal temperature rise. This has rendered the urban climate increasingly taxing to the human health and comfort.M seasonal, and annual variations of salinity profiles over different sectors of the Bay of Bengal (BoB) are investigated using seven years of Argo data. The salinity profile analysis together with the analysis of variability in surface circulation and precipitation utilized to understand interannual and seasonal variability in salinity profiles over three sectors of BoB i.e., northern (NBoB), central (CBoB), and southern (SBoB). The influence of massive river outflow close to river mouths in producing the observed sea surface salinity minima in the coastal northern BoB during November-December is highlighted. Seasonal changes in salinity profiles are primarily caused by freshwater flux, mixing processes and advection. In general, NBoB remains fresher as compare to CBoB and SBoB throughout the year. Interannual variability of salinity structure was found to be maximum in NBoB, particularly in post-monsoon (ON) and winter (DJF) seasons, where the differences in surface salinity between the years were found to be up to 2 psu. CBoB shows minimum interannual variations in salinity profiles, except unusual decrease in surface salinity on two occasions. Analysis suggest crucial role of coastal currents, gyres and surface circulation in controlling seasonal and interannual variability in salinity profiles. Some unusual features observed in salinity profiles during pre-monsoon season of year 2009 in the SBoB, which is analyzed further with other data sets and discussed in detail.E fluoride concentrations have been reported in ground waters of more than 20 developed and developing countries around the world including India where 20 states are facing acute fluorosis problems. In this paper, the teeth of 152 school children (06 to 11yrs) of Govt. Primary school, Gandhoniya, Barkagaon, Hazaribag, and Jharkhand, India were surveyed and collected data were compared with Dean’s Index. The results clearly indicate that the most of them are suffering from dental fluorosis consequently creating a lot of problems such as poor health, endurance of dental abscesses, inability to chew food well, embarrassment about discoloured & damaged teeth and distraction from play & learning in the area. School based oral health check-up programme be organised regularly for awareness of general mass. It should include screening, referral and case management to ensure the timely receipt of oral health care from health professionals in the community.

Coastal upwelling features in the Arabian Sea from ROMS model

A attempt has been made to understand the ground water quality by using the water quality index (WQI) in the mining region of Goa. WQI, a technique of rating water quality, is an effective tool to assess spatial and temporal changes in ground water quality. Forty five groundwater samples were collected from open and tube wells during summer, monsoon, post-monsoon and winter seasons. The groundwater samples were subjected to comprehensive physio-chemical analysis involving major cations (Ca2+, Mg2+, Na+, K+, Fe2++ ) anions ( HClO3-, Cl, SO4 2-, NO3-, F-, PO4 3-) besides general parameters (pH, EC, TDS, alkalinity, total hardness, color, turbidity). The water quality index rating was calculated to quantify overall water quality for human consumption. For calculating WQI 10 parameters, namely pH, TDS, total hardness, chloride, nitrate, turbidity, fluoride, iron, calcium hardness, magnesium hardness were considered. The values of WQI have been affected mainly by the concentration of dissolved ions (F, NO, Ca and Mg) in ground water. Concentration of dissolved solids found to be more during monsoon season. It may be due more seepage and movement of ground water due to excessive rainfall there. The values of WQI of the samples were found in the range of 8-12 for all the seasons and considered to be in the very good category.U Heat Island is a more threatening meteorological phenomenon in the longer summer tropical cities with already critical thermal regime than in the longer winter temperate cities. Further, the population growth in the tropical megacities is far greater than their counterpart temperate cities. The present paper enquires the changing trends in the urban climates. Cities are recognized as urban heat islands because their temperatures are higher by 3°C to 9°C in comparison to the temperatures of the surrounding rural areas. This thermal differential is generally proportional to the city size and morphology. Larger is the city size and more diverse are its residential, industrial and commercial functions, larger and higher is its heat dome. Urban Heat Island has become a major environmental issue particularly in view of rapid urban sprawl in the developing countries. Urban Heat Islands are the nuclei of global warming and climate change. Urban Heat Island is not a cognizable problem of towns and small cities. It is a matter of great concern to the urban planners, environmentalists and citizens of the large cities, particularly the million and megacities. However, this problem is assuming a serious dimension in a fast emerging megacity of Hyderabad. The present paper estimates heat island intensity of Hyderabad. In the wake of its rapidly growing economy, size and population, the city has experienced a population growth from 1.79 million in 1971 to 7.74 million in 2011. The corresponding built-up area has recorded a growth from 298.5 sq.km. to a sprawling 851 sq.km. The paper enquires the adverse impact of this built-up growth on the daytime as well as nocturnal temperature rise. This has rendered the urban climate increasingly taxing to the human health and comfort.M seasonal, and annual variations of salinity profiles over different sectors of the Bay of Bengal (BoB) are investigated using seven years of Argo data. The salinity profile analysis together with the analysis of variability in surface circulation and precipitation utilized to understand interannual and seasonal variability in salinity profiles over three sectors of BoB i.e., northern (NBoB), central (CBoB), and southern (SBoB). The influence of massive river outflow close to river mouths in producing the observed sea surface salinity minima in the coastal northern BoB during November-December is highlighted. Seasonal changes in salinity profiles are primarily caused by freshwater flux, mixing processes and advection. In general, NBoB remains fresher as compare to CBoB and SBoB throughout the year. Interannual variability of salinity structure was found to be maximum in NBoB, particularly in post-monsoon (ON) and winter (DJF) seasons, where the differences in surface salinity between the years were found to be up to 2 psu. CBoB shows minimum interannual variations in salinity profiles, except unusual decrease in surface salinity on two occasions. Analysis suggest crucial role of coastal currents, gyres and surface circulation in controlling seasonal and interannual variability in salinity profiles. Some unusual features observed in salinity profiles during pre-monsoon season of year 2009 in the SBoB, which is analyzed further with other data sets and discussed in detail.E fluoride concentrations have been reported in ground waters of more than 20 developed and developing countries around the world including India where 20 states are facing acute fluorosis problems. In this paper, the teeth of 152 school children (06 to 11yrs) of Govt. Primary school, Gandhoniya, Barkagaon, Hazaribag, and Jharkhand, India were surveyed and collected data were compared with Dean’s Index. The results clearly indicate that the most of them are suffering from dental fluorosis consequently creating a lot of problems such as poor health, endurance of dental abscesses, inability to chew food well, embarrassment about discoloured & damaged teeth and distraction from play & learning in the area. School based oral health check-up programme be organised regularly for awareness of general mass. It should include screening, referral and case management to ensure the timely receipt of oral health care from health professionals in the community.