Bh. V. Ramana Murty

Impact of alkaline particulates on pH of rain water in India

Rain water samples were collected over a period of a decade from 1974 in Pune, a city which is relatively free from industrial pollution. They were also collected at 4 places during 1974 in the region of Bombay which is highly industrialized. The samples were analyzed for major chemical components and pH. The ionic balance was computed. Samples were collected at Delhi during 1965 and 1966 and were analyzed for pH. The values were compared with those reported for 1978. The total suspended particulates (TSP) were measured at Delhi during 1980 and analyzed for water soluble components. The rain water at all the places except near the industrial source was not acidic and was characterized by the presence of excess cations, particularly Ca. The acid rain near the industrial source was associated with excess anions, especially sulphate. The difference between the cations and anions was inversely proportional to the H+ ion concentration. The pH of rain water at Delhi which was in the alkaline range during 1965 and 1966 remained alkaline even after a period of 12 yr when the city developed industrially. The TSP in the region was rich with the basic components, mainly Ca, suggesting that the alkaline property of the soil dust is mainly responsible for neutralizing the acidic effects resulting from the anthropogenic gaseous pollutants.

Trace elements and sea salt aerosols over the sea areas around the Indian sub-continent

Abstract The nature and the characteristics of trace elements and sea salt aerosols in the ocean atmosphere around the Indian sub-continent was studied. For this purpose, concentrations of the total suspended particulates (TSP) as well as of its various chemical components together with their mass size distributions were measured on 11 days in May 1983. Over the sea regions around the sub-continent, sampling was done on board the research Vessel Gaveshani using a high volume air sampler and a multistage Andersen sampler. The concentrations of soil-origin elements (Al, Fe, Mn and Ca) were found to be at a maximum over the Arabian sea region suggesting the presence of dust particulates, transported from the Arabian peninsula. The near sea water ratio of CI/ Na was observed in giant size (> 2.5 μm dia) sea salt aerosols suggested that there was very little fractionation in these aerosols. The ratio value considerably decreased in the case of sub-μm sea salt particles. The chemical components originating from soil and from sea salt showed a unimodal distribution whereas those from anthropogenic sources showed a bimodal distribution.

Trace elements in the atmospheric aerosols at Delhi, North India

The total suspended particulate (TSP) levels at Delhi (north India) were measured on 116 days between February and October 1980. The observations were stratified according to season and the values of cross-correlation of the TSP and its components were evaluated. High TSP (209 μg m-3) levels were found during the summer period associated with hot and dry weather in the region and low TSP (109 μg m-3) were found during the monsoon period. Most of the TSP mass was associated with natural soil elements, such as Fe, Al, Mn, Ca, and K. Only a fraction of the mass of the TSP was comprised of elements from anthropogenic sources, e.g., Pb, Ni, Cd, Sb, Cu, and Zn. The aerosols at Delhi were potentially basic in nature, unlike those in European countries which are acidic in nature and cause acid rainfall.

Observations of Aitken nuclei and trace gases in different environments in India

Surface measurements of Aitken nuclei have been made at a few representative environments in India. The periods of measurements have ranged from a few days to a few years depending upon the place of measurement. Aircraft measurements of Aitken nuclei were made at one of the locations during three successive monsoon periods. During part of the time simultaneous measurements were made of the trace gases SO2, NH3, NO2, and O3. The study presents the seasonal and diurnal variation of Aitken nuclei in the different environments and their association with the trace gas concentrations.

Characteristics of Raindrop Charge and Associated Electric Field in Different Types of Rain

Abstract Simultaneous measurements of raindrop charge, atmospheric electric field and rain intensity were made at Poona using fast response, continuous recording surface instruments during four types of rain: pre-monsoon (thunderstorm rain), monsoon rain type I (tight intermittent rain), monsoon rain type II (heavy continuous rain) and post-monsoon (thunderstorm rain). Measurements were also made of the conductivity of rainwater samples collected during the monsoon season. On some days of this period data on cloud thickness as obtained from the aircraft flights in the region were also available. The electric field associated with negatively charged raindrops was less negative than that associated with positively charged drops. The raindrop charge spectrum showed different characteristics during the four types of rain studied. It was broadest during the pre-monsoon rain when the convective activity was a maximum. It followed a log-normal distribution during the monsoon rain type I and it was peaked and ske...

Freezing characteristics of rain water drops with different solutes and their implication on anomalous ice crystal concentrations in clouds

In an attempt to examine the probable cause for the reported anomaly between the ice crystal-and ice nucleus concentrations in clouds, the authors have carried out laboratory experiments on the freezing of rain water drops, under various conditions of temperature, with various solutes. Sulphates, when present in adequate concentration, have been found to accelerate remarkably the process of ice-formation in the drops. The contrast noticed has been greater at warmer temperatures. The ice-forming ability of silver iodide has also improved remarkably in the presence of sulphates. Chlorides, on the contrary, not only decelerated natural ice-formation in the drops but also deactivated silver iodide. Based on certain considerations, the features observed have been interpreted to account for at least part of the anomalous ice crystal concentrations reported in clouds.

Chemical composition of rain water and rain characteristics at Delhi

Rain water samples collected with the progress of rain shower on a number of rain occasions in different seasons at Delhi have been analysed for chloride, sulphate, sodium, potassium and calcium. The trend of variations in the concentration of chloride ion in rain water with the progress of a rain shower would seem to suggest that the growth of rain drops in convective clouds at Delhi would involve a process which might be analogous to what was envisaged by Woodcock for Hawaiian rains. Further, it was noticed that the characteristics of precipitation at Delhi are dependent on the amounts of air-borne soluble particles present in the cloud forming air. Smaller cation concentration ( < 1 ppm) and higher value of Cl/Na ( > 1.8) distinguish what may be called “freezing” rain (rain from cold layer clouds) from that of the other type in which both freezing and non-freezing mechanisms operate (rain from cold convective clouds). Smaller ratio values of sulphate to chloride ( < 6) and higher ratio values of chloride to sodium ( > 1.8) characterize heavier rainfall. Probable explanations have been suggested for these observed features.

Variation of Tropospheric Temperatures over India dining 1944–85

Abstract Variation of air temperature at the surface and at four levels in the troposphere, viz., 850, 700, 500 and 200 mb, over India have been studied using the data at ten radiosonde stations for 31 to 42 years during 1944–85. Seasonal as well as annual mean temperature series have been obtained, and the general feature of the variations are discussed. Quantitative study of the temperature changes is made by evaluating the linear trends. Surface temperatures do not show appreciable trends during the last three decades over India, but at the upper levels there was a trend reversal around 1958, from warming to cooling. There is a distinct contrast between the northern and southern Indian stations during 1958–85, in that the former have shown significant cooling while the latter have shown no trends. Port Blair, the island station considerably south, however, shows slight cooling during this period. The rate of cooling increases with height, particularly at the northern stations. There is no marked inters...

Some thermodynamical and microphysical aspects of monsoon clouds

The thermodynamical and microphysical characteristics of monsoon clouds in the Poona, Bombay and Rihand regions were investigated using extensive aircraft in-cloud observations. The number of clouds sampled at Poona, Bombay and Rihand is 2199, 169 and 104 respectively.The temperatures inside the cloud are colder than its environment at Poona and Rihand. The maximum difference is about 3°C at the cloud base level and the difference decreased with height. At Bombay the difference is less than 1°C and at some levels the temperatures inside the cloud are warmer than its environment.The lapse rates of temperatures inside the cloud are slightly less than those in the immediate environment of the cloud. The environmental lapse rates are nearly equal to the saturated adiabatic value.The positive increments in liquid water content (LWC) are associated with the increments in temperature inside the cloud. Similarly positive increments in temperatures inside the cloud are associated with the increments in temperature of its immediate environment at the same level or the layer immediately above.The maximum cloud lengths observed at Poona and Bombay respectively are 14 and 3 km. The horizontal cross-section of LWC showed a maximum number of 13 peaks in clouds at Poona while only 7 peaks were observed at Bombay. The location of maximum LWC in the horizontal cross-section is more or less at the centre of the cloud. The LWC profile showed an increase with height from the base of the cloud at Poona and Bombay. There is no marked variation of LWC with height at Rihand.The total droplet concentration at different altitudes at Poona and Bombay is in the range 28–82 cm−3. The size distribution of cloud droplets experienced a broadening effect with increase in height from the cloud base at Poona. The broadening effect at Bombay is not as marked as that at Poona.

Electrical and microphysical measurements in warm cumulus clouds before and after seeding

Abstract Electrical and microphysical measurements were made in warm maritime and inland cumulus clouds, before and after seeding, by repeated aircraft penetrations at a single level, a few hundred meters above cloud base. Such measurements were also made in non-seeded clouds by single penetrations during transient flights. The electric field initially was negative in the maritime clouds which developed rain. In the cloud case which dissipated without rain it was initially positive. The field showed sign reversal with time, occasionally preceded by intensification, in all maritime clouds. The field initially was positive in inland clouds. It showed no time variation except in one cloud case where both positive and negative fields were recorded during the period of heavy rain. The droplet charge, droplet median volume diameter and liquid water content showed no marked time variation in either maritime or inland clouds. However, in the cloud case which developed heavy rain marked increases in droplet median...