P. Pradeep Kumar

Partially soluble organics as cloud condensation nuclei: Role of trace soluble and surface active species

[1]xa0The ability of partially soluble organic species to act as cloud condensation nuclei (CCN) has been studied. A Kohler model incorporating solute solubility and droplet surface tension describes the behavior of solid adipic and succinic acid particles, whereas solid azelaic acid activates much more efficiently that predicted. In addition, it was shown that trace levels of either sulfate or surface active species have a dramatic effect on the activation of adipic acid, a moderately soluble organic, as predicted by the full Kohler model. For internally mixed particles in the atmosphere, these effects will greatly enhance the role of organic aerosols as CCN.

Formation of cloud condensation nuclei by oxidative processing: Unsaturated fatty acids

[1]xa0The ability of submicron oleic acid and linoleic acid particles, or condensation nuclei (CN), to act as cloud condensation nuclei (CCN) has been investigated using a tandem differential mobility analyzer (TDMA) coupled to a flow tube reactor and a thermal gradient diffusion chamber (TGDC). The size change and CCN properties of pure oleic acid, mixed oleic acid/methanol, and pure linoleic acid particles have been investigated as a function of exposure to ozone. Pure oleic and linoleic acid particles were CCN inactive for all particle diameters (≤300 nm) and supersaturations (≤1%) studied. The mixed oleic acid/methanol particles, however, had a critical activation diameter of 188 nm for an experimental water supersaturation of 0.6%. Under low ozone exposures (<1 × 10−4 atm s), both the oleic acid and linoleic acid particles decreased in size. In particular, oleic acid particles lost 25% of their initial volume, consistent with the loss of nonanal, a volatile reaction product. However, no increase in CCN activity was observed at these exposures. Under conditions of much higher ozone exposure, e.g., 0.42 atm s, the pure oleic acid particles became CCN active, with a critical activation diameter of 161 nm at 0.6% supersaturation. CCN activity for the linoleic acid particles was never observed, even under these high ozone exposures not typically observed in the atmosphere. By contrast, the mixed oleic acid/methanol particles showed enhanced activation under atmospherically relevant ozone exposures (<1 × 10−4 atm s). These results suggest that the products of the ozone plus unsaturated fatty acid reaction do promote the CCN activity of the particles; however, the degree of activity is dependent on both the level of ozone exposure and the chemical nature of the particle. These results are the first to demonstrate that the CCN properties of pure organic aerosols can be modified through oxidative processing.

Global distribution of nitric oxide produced by lightning and its seasonal variation

The global distribution of NO production due to lightning has been estimated using the lightning discharge frequency observed from the global distribution of thunderstorm activity obtained from the ISSS-b satellite observations during June 1978 to May 1980 and issued by Radio Research Laboratories, Japan. The seasonal and latitudinal variation has been investigated. The annual production of NO by lightning from the present study is found to be 2 Tg N yr−1.

A laboratory study of ice nucleation due to electrical discharge

Abstract Experiments were performed in a walk-in cold room where the lowest attainable temperature is −30 °C to investigate the effect of electrical discharge and high electric fields on ice nucleation. Experiments were carried out at cloud temperatures varying from −9 to −12 °C. It was observed that ice nucleation does occur inside the cloud if there is an electrical discharge inside the cloud. However, not all electrical discharges resulted in ice nucleation. In no case was ice nucleation observed in the presence of high electric fields with no discharge. No ice nucleation was noted in the cloud when the Liquid Water Content (LWC) was greater than 2.1 g m −3 .

Trends in seasonal temperatures over the Indian region

An investigation has been carried out to identify the trends in maximum, minimum and mean temperatures and temperature range over the Indian land mass during the winter (January, and February), pre-monsoon (March–May), southwest monsoon (June–September) and post-monsoon (October–December) seasons by using high resolution daily gridded data set prepared by India Meteorological Department for the period of 1969–2005. It has been observed that the maximum temperatures over the west coast of India show rising trend in winter, southwest monsoon and post-monsoon seasons but the maximum temperatures do not show any significant trend over the other parts of the country. Minimum temperatures show increasing trend over the North Indian states in all seasons and they show an increasing trend over the west coast of India in winter and southwest monsoon seasons. Mean temperature shows an increasing trend over the west coast of India during winter and southwest monsoon seasons. Decreasing trend is observed in the temperature range over North India in all seasons due to increasing trend in minimum temperature.

WRF model sensitivity for simulating intense western disturbances over North West India

During winter season, large amount of precipitation is received in the Northwestern part of India due to eastward moving low pressure synoptic weather systems called western disturbances (WDs). These WD’s disturbs the life in Northern India with heavy precipitation, cold wave and fog. The objective of the present study is to examine model sensitivity of different physical parameterization schemes incorporated in the weather research and forecasting model and to identify a combination of the best physics options suited for this region during the passage of a western disturbance. Four cases of intense western disturbances 13–17 January 2002 (case-1), 5–8 February 2002 (case-2), 16–19 January 2013 (case-3) and 4–7 February 2013 (case-4) which affected the northwest India has been simulated with different physics configurations in the model. The model simulation from different physics configurations are validated with the observational datasets and error statistics are presented. It is found that, the performance of the combination of National Severe Storms Laboratory one moment, Kain–Fritsch, Yonsei University, rapid radiative transfer model and Dudhia schemes as a microphysics, cumulus, planetary boundary layer, longwave radiation and shortwave radiation parameterization schemes respectively gives a better simulation of the weather during WD’s over this region. It is found that, in all WD cases intensity and movement of the precipitation, circulation and low pressure area (geopotential height) over the region is well predicted by the model.

Interpolation of missing data using nonlinear and chaotic system analysis

A new method for interpolating missing data in a time series is introduced. The method uses local flow approximation for interpolation and is based on a suitable modification of some recent developments in predicting nonlinear and chaotic time series. The method has been tested for various geophysical and climatic time series. We find that in many cases the method gives better results than the cubic spline. The real power of this method is seen when there are several consecutive missing values in the series.

Inter annual variability of tropospheric NO2 and tropospheric ozone over Maharashtra (India) : the role of lightning

ABSTRACT The seasonal and inter annual variability of Tropospheric Nitrogen dioxide (NO2), Ozone (O3) and lightning activity over Maharashtra and adjoining part of states (15.5°N-22.5°N, 72.5°E-81.5°E) of India, is analyzed to study the role of lightning activity in the seasonal variation of NO2 and O3. Satellite observations of Tropospheric NO2 and O3 from Aura- Ozone Monitoring Instrument (OMI)/Microwave Limb Sounder (MLS) for the period 2005–2016 and lightning data of 2014–2016 from lightning detection network over Maharashtra are used for analysis. Analyses show that the seasonal variations of all the three quantities are closely related to each other. The scatter plot between monthly NO2 concentration verses monthly lightning activity for years 2014–2016 also show good correlation between these two parameters (r = 0.71, significant at 99.9%). Our analysis demonstrates that the seasonal and inter-annual variations in NO2 and O3 are affecting by lightning activity over study region. However, biomass burning during April-May and increased air pollution during winter months (November-January) also play important role in the intra seasonal variations of NO2 and O3 over this region.

Effect of sulfates and chlorides on electrification by a noninductive process applicable to stratiform clouds

[1]xa0Laboratory investigations have been carried out to find the sign and magnitude of charge transfer during the collision between ice crystals and graupel in the presence of supercooled water droplets inside a cylindrical steel chamber kept inside the walk-in cold room, which can reach a temperature of −30°C. The experiments were performed with pure water (Milli-Q, 18.2 Megohms-cm) and with a trace amount of ammonium sulfate and sodium chloride at different concentrations at low rime accretion rate (<0.1 g m−2 s−1), similar to stratiform clouds in the temperature range −6°C to −26°C. The cloud was composed of supercooled water and vapor was produced by boiling premixed solutions containing trace amount of impurities. The impurities are carried into the cloud by the bubble-breaking mechanism. This way of introducing impurities is different from the earlier experiments. The experiments were carried out at a constant impact velocity of 2.2 m/s. At higher temperatures, the sign of the graupel charging during the ice crystal–graupel collision for pure water obeys that of earlier studies. With a trace amount of ammonium sulfate and sodium chloride, the sign of charge transfer is different from that of pure water. The effect of cloud droplet spectra on the sign of charge transfer for pure water were in agreement with earlier studies but differed for sodium chloride.

Climate Change Impacts: Central Himalaya

This chapter provides a brief description of glaciers in Uttarakhand Himalaya and witnessed the impact of climate changes over the past few decades. Glaciers are inhomogeneously distributed from north-west to south-east along Himalaya, and recent studies have brought out that shrinking of glaciers is taking place at alarming rate. Observations over Central Himalayan region have revealed an average retreat of glaciers about 17 m in last six decades, and Gangotri, Chaurabari, Pindari, and Dokriani are some of the major glaciers of Uttarakhand Himalaya that have experienced the impact of climate change. The Central Himalayan region is endowed with efficient hydrological cycle fed by prevailing favorable weather patterns such as western disturbances in winter and monsoons in summer, but there has been a general trend of depleting water availability at source region due to climate change in past century. Climate change has adversely affected the water resources, forest and biodiversity, agriculture and human health; all these aspects are summarized in the context of Uttarakhand state. As per IPCC 2013 report and the analysis of long period available data on rainfall suggests that extreme weather events and natural disasters are likely to increase. An example of natural disaster took place at Deoli village in Almora district is also presented.