The impact of a severe dust storm that originated over the Arabian Peninsula (AP) and travelled to the Indian subcontinent during 20-26 January 2022 is examined. According to the event's synoptic analysis, the Gulf of Oman, adjacent areas of Oman and Iran had strong mid-lower tropospheric westerlies because of the configuration of north-south cyclonic and anticyclonic circulation patterns generated by a sizable north-south pressure gradient. A strong westerly wind component continued down to surface level and brought large quantities of dust from the desert region of the Middle East to the Indian subcontinent. Overall, 90% of the monitoring locations over the Indian subcontinent (mostly the western region) exceeded the national tolerable level of 100 mu g m(-3) (PM10), with peaks as high as 650 mu g m(-3). Changes in optical and physical properties of aerosols varied in accordance with the dust loading, in which absorption aerosol optical depth denotes a 10% increase in absorbing aerosols. Due to the excessive cooling effect, the near-surface air temperature dropped by -6 degrees C from its daily climatology over a sizable zone of high aerosol loading. Additionally, the dust storm prolonged the winter's harshness by lowering temperatures (from pre-dust days) in some of the most severely afflicted areas to 10-12 degrees C. Changes in wind patterns at mid- and low levels have resulted in a temperature inversion (similar to 2.5 km), which prevented trapped dust particles from being diluted, which in turn increased the likelihood of a more significant decline in air quality and affecting human health/wealth.

AbstractEffects of eccentricity and horizontal electric field (EH) on the binary‐collision outcomes of water drops are examined using numerically calculated collision characteristics from previous studies and results of simulation experiment conducted by the authors. For a fixed collision kinetic energy (CKE), filament breakups can occur at all values of eccentricity but events of coalescence decrease, and that of sheet breakup increase with increasing eccentricity in absence of EH. However, as EH increases to ∼300 kVm−1 it opposes the variability of the coalescence and sheet breakup events with eccentricity. When EH exceeds ∼300 kVm−1 the collision outcomes might be determined only by the CKE and EH. The calculated value of coalescence efficiency and total number of fragments after a binary collision decreases with an increase in EH. It is argued that an electric field can significantly modify drop size distribution in thunderclouds and needs to be considered for development of precipitation.

The analysis of Tropical Rainfall Measuring Mission-Lightning Imaging Sensor (TRMM-LIS) datasets indicates that lightning distribution in Uttarakhand significantly varies with elevation, peaking in the Himalayan foothills below 1500 m and decreasing above 4000 m. Furthermore, moderate (SLI 1–2) and mild (SLI 0–1) lightning hotspots have been identified in Uttarakhand. The monthly variations in lightning flash rate density (LFRD) and surface meteorological parameters show a moderate correlation of <0.6. However, the lag of 1 to 3 months in the meteorological parameter peak values from LFRD peak values does not support the cause-and-effect relation between them. However, LFRD is better correlated (r = 0.97) with the sensible heat fluxes (SHF). We found that the product of the Bowen ratio (BR) and convective rain rate (CRR) can serve as a good representative of lightning over this region. Principal component analysis (PCA) of the data reveals a strong relationship between LFRD and SHF, BR, the product of BR and CRR, maximum surface temperature (MST), CAPE, humidity, and CRR, emphasizing the impact of strong land surface heating, air parcel buoyancy, and deep convection on lightning. Cloud base height and latent heat flux (LHF) have weak correlations with LFRD. Eigenvalue loadings analysis indicated that CAPE, MST, humidity, and CRR are dominant factors in principal component (PC) PC1, while LFRD, BR, SHF, and the product of BR and CRR are dominant factors in PC2, influencing lightning over this region. This study offers valuable insights into the lightning distribution over Uttarakhand and its relationship with meteorological, topographical, and thermodynamic variables.

Coalescence/breakup characteristics of binary collisions of small water drops ( d S = 0.4–1.8 mm diameter) with large drops ( d L = 3–3.5 mm diameter) occurring in the absence/presence of horizontal electric field ( E H ) = 0, 100, and 300 kVm −1 have been investigated in a small vertical wind tunnel using a high‐speed digital camera. The coalescence efficiency ( E C ) of 0.299 observed for average diameters ( d L = 3.2 mm, d S = 1.2 mm) in E H = 0 decreased to 0.244/0.211 when E H is increased to 100/300 kVm −1 . The increase in the electric field reduces the probability of coalescence when Weber number (We) < 1. However, when We ≥ 1, an increase in We restricts the probability of coalescence. Our data, when plotted in the regime diagram in the We*‐ p plane, delineates the collision outcomes in all‐electric field values but does show the overlapping of some data points in the adjacent categories. After a binary collision, the relaxation time for coalescence is higher than that for the breakup. Further, the relaxation time increases from the filament to sheet to disk mode of breakup in all‐electric field values. Fragment size distributions after the filament and sheet types of breakups differ and are differently affected by the applied electric field. Higher collision kinetic energy has a tendency to increase the number of fragments of the sizes between d L and d S . It is concluded therefore that, the effect of the electric field needs to be included in the estimation of drop growth and precipitation in clouds.

More than 40 years of aerosol data including concentrations of particle number and of nine major ions collected over the Southern Ocean and coastal stations have been aggregated and filtered with back trajectories to reduce the risk of influence from adjacent continents. That provided a rich dataset including latitudinal distribution and seasonality of physical and chemical aerosol parameters that allow insights into aerosol sources over the Southern Ocean. These data together with statistics of back trajectory paths of high (75% percentile) and low (25% percentile) concentrations of the studied aerosol parameters were used to identify potential source regions of the respective compounds. For particle number concentrations, MSA, and the non-sea-salt fractions of Ca and potassium the most prominent source regions were found in high DMS-areas close to Antarctica, whereas the potential source regions of NH4 and the non-sea-salt fraction of Mg were located in part further north over the Southern Ocean. These geographical differences would reflect differences in the marine biota.

In recent years, the studies in global electric circuit (GEC) have received additional interest because of its potential to monitor climate and its use in representing the planets electrical subsystem in Earth system models. The new tools and climate models developed recently have improved our insight not only into various atmospheric processes involved in the GEC, but also in their mutual interactions on the local and global scales. The processes occurring within the atmosphere and outside it in space have been observed to influence the Earth's electrical environment. In this article, we summarize the work done in these directions and give some recommendations for better understanding of the GEC.

Atmospheric electricity parameters (AEP) measurements from Antarctica predominantly feature either the potential gradient (PG) and/or air‐Earth current (AEC) density. We report for the first time simultaneous measurements of the bipolar ions concentration/conductivity, PG, and AEC density. AEP measurements were carried out at Maitri (70.8°S, 11.8°E) from December 2018 to November 2019. We formulated a few criteria, irrespective of the weather conditions, to select the electrically quiet days and some additional criteria based on the conductivity measurements to discern globally representative data (GRD) from such days. The measurements of the PG and AEC density over the Antarctic plateau demonstrated the diurnal curves similar to the Carnegie pattern, which represents the global thunderstorms and electrified shower clouds (ESCs) occurring on different continents and oceans, we regard the data having such trend as GRD. We found significant variability in the concentration of small bipolar ions/conductivity in the austral summer which in turn affects GRD. However, the concentration of bipolar ions is nearly consistent at ∼250 negative ions cm −3 and ∼300 positive ions cm −3 in winter and enhances the probability of GRD. Such differences can arise out of the prevalent planetary boundary layer processes in the two seasons. When the PG varied between ∼50 Vm −1 and ∼150 Vm −1 and the maximum range of conductivity variations was ∼0.2 × 10 −14 ℧ m −1 , the AEPs represented the signatures of the global thunderstorm and ESC activities.

Product of Bowen ratio with the sum of precipitation rate and evaporation rate has been used as proxy to evaluate the seasonal and annual spatial distributions of lightning flash rate over South/Southeast Asian region (60–120° E, 0–40° N) with 9 models from the Coupled Model Inter-comparison Project-Phase 5 (CMIP5). The model-simulated mean LFR with each model is positively correlated with the satellite-observed LFR on both seasonal and annual scales. The satellite-observed LFR is correlated with the ensemble mean LFR of the models with a correlation coefficient of 0.93 over the region. The model-simulated LFR has also been used for projection of lightning in the late twenty-first century. Overall, the projected LFR over whole study area shows a 6.75% increase during the (2079–2088) period in high radiative forcing scenario (RCP8.5) as compared to the historic period of (1996–2005). Rise in LFR is also identified using another projected period (2051–2060) and a lower radiative forcing scenario condition (RCP4.5), though lesser in magnitude, as expected. For the projected period (2051–60) in the RCP8.5 case, LFR over the domain shows an increase of 4.3%; whereas for a lower future scenario condition (RCP4.5), it indicates a rise by 5.36% at the end of the twenty-first century. Moreover, results indicate an increase in extreme events of severe convective storms with intense lightning in mountainous dry regions at the end of the twenty-first century. It is suggested that the proxy used here is favourable for projection of LFR in this region and perhaps for the whole tropical area.

Impacts of environmental changes at Pune, India during the lockdown period imposed due to the Covid-19 pandemic, on the characteristics of the atmospheric ions and the new particle formation (i.e. the formation of molecular clusters and their subsequent growth to larger sizes) and shrinkage events have been investigated. The increase in the small and big cluster ion concentrations and the decrease in intermediate ion concentrations observed during the lockdown period have been associated with the decrease in the aerosols and precursor gases, respectively. During the NPF events, the nucleation mode particles of both polarities grow in size. However, during the unique shrinkage events observed here, particles increase in concentration but do not grow in size during the morning-to-noon period and shrink in the noon-to-evening period during the lockdown period. Simultaneously, the concentration of particles of >25 nm decrease i during the morning hours and increase during the afternoon hours .On the shrinkage event days, solar irradiance is higher and relative humidity is lower throughout the day than on the NPF/no-event days. Occurrence of shrinkage events has been proposed to be associated with the change in saturation vapour pressure of different chemical species with temperature/solar irradiance.

Based on the large exchange of heat fluxes on the Earth's surface in the tropics, we propose that the lightning flash rate (LFR) is proportional to a product of the Bowen ratio and the sum of precipitation and evaporation rates. The proposed relationship is justified on the basis of the conversion of the kinetic energy of charging hydrometeors to the energy of flash discharges. However, the proportional relationship varies depending on the season. This product explains 90% of the variance in the monthly-averaged time series of the total LFR over our study area of 0° N-40° N and 60° E-120° E including south/southeast Asia and some part of southern China. The conversion efficiency is a maximum in the pre-monsoon season and minimum in the winter season. The total heat flux best accounts for the seasonal variation of the LFR.

The role of antennas in the detection of atmospheric conduction current has been discussed since the beginning of the 20th century. Propriety of the antenna design needs to be reviewed from time to time as the measurements experience different problems on various terrains. The present work deals with such issues and brings out a suitable antenna design to detect the conduction current observed at the Indian Scientific Research Station at Maitri (70.8 degrees 5 11.7 degrees E), Antarctica. Two long wire antennas and two plate antennas are simultaneously used to monitor the air-Earth current in the open space at this station. The experiments reveal that the currents recorded by the long-wire antenna and plate antenna display similar characteristics but differ in the magnitude and the response to the varying current. On a fair-weather day the mean current density obtained by 41 m long-wire antenna is similar to 0.4 pA m(-2), 10 m long-wire antenna is 2.5 pA m(-2), 0.25 m(2) plate antenna is 3.5 pA m(-2,) and 1 m(2) plate antenna is 4.2 pA m(-2). The current sensed by 1 s and 1000 s R-C time constant do not show any significant difference in the hourly mean diurnal variation as well as in the magnitude. The study reveals that a plate antenna is a better option for the long term monitoring of air-Earth current. The simultaneously monitored potential gradient at this station and Vostok (78.4 degrees 5, 106.8 degrees E) are used to identify the local and global electric signals.

The regional variability of lightning activity over 10 different regions, selected with at least one major meteorological/topographical feature, of South Asia (8 degrees N-36 degrees N, 90 degrees E-100 degrees E) have been examined on all time scales from the data obtained from July 1995 to December 2013 from the Tropical Rainfall Measuring Mission satellite. A comparative study of the correlation coefficients calculated between lightning flash rate and convective parameters, aerosol optical depth (AOD) and topography for different regions is carried out. Impact of the progress of the Asian Monsoon on the spatio-temporal variability of flash rate is also examined. Monthly-averaged variations are annual at the regions >2,700 m in altitude and are semi-annual at the regions <2,700 m in altitude. The annually averaged flash rates increase during the study period in most of the regions. However, such long-term changes are nonlinearly related to the change in convective parameters and AOD and such inter-relationships differ from one meteorological region to another. Small changes in AOD in high altitude regions are associated with very large changes in the surface temperature and flash rate. The flash rate is strongly correlated with surface temperature in the dry region of the north-west but with CAPE in moist region of the north-east. Progress of the Asian monsoon strongly impacts the flash rate in different regions. Ratio of the amplitudes of primary to secondary maxima at land stations increases with latitude in case of the monthly-averaged variations in flash rate. The primary maxima in these variations are highly correlated with the atmospheric surface temperature. However, the secondary maxima are associated with the low-level convergence during the withdrawal phase of the monsoon. Incursion of moisture by the Bay of Bengal branch of monsoon current determines the sequence of occurrence of lightning activity in different regions along the Himalayan foothills and north-west.

The impacts of elevation, terrain slope and vegetation cover on lightning activity are investigated for contrasting environments in the north-east (NE) (21– $$29{^{\circ }}\hbox {N}$$ ; 86– $$94{^{\circ }}\hbox {E}$$ ) and the north-west (NW) (28– $$36{^{\circ }}\hbox {N}$$ ; 70– $$78{^{\circ }}\hbox {E}$$ ) regions of the Himalayan range. Lightning activity is more at a higher terrain slope/elevation in the dry NW region where vegetation cover is less, whereas it is more at a lower terrain slope/elevation in the moist NE region where vegetation cover is more. In the wet NE, 86% (84%) of the annual lightning flash rate density (LFRD) occurs at an elevation $${<} 500\ \hbox {m}$$ (terrain slope $${<} 2\%$$ ) and then sharply falls off at a higher elevation (terrain slope). However, only 49% (47%) of LFRD occurs at an elevation of $${<} 500\ \hbox {m}$$ (terrain slope $${<} 2\%$$ ) and then rather gradually falls off at a higher elevation (terrain slope) in the dry NW. The ratio of the percentages of LFRD and elevation points is much higher in the NW than in the NE above an elevation of $${\sim } 1000\ \hbox {m}$$ . The impacts of terrain slope and elevation in enhancing the lightning activity are stronger in the dry NW than in the moist NE. The correlation coefficient of the LFRD with the normalised difference vegetation index is higher in the NW than in the NE on both the regional and annual scales. Results are discussed as a caution in using any single climate variable as a proxy for projecting a change in the lightning–climate relationships in the scenario of global warming.

Continuous measurements of the concentration of Radon (222Rn) and its progenies were made with a Radon detector, RTM 2200, at a tropical site, Pune (18° 31′ N, 73° 55′ E, 560 m), India from January to December 2012. Simultaneous measurements of small ions of <1.6 nm diameter were made with a Neutral Air Ion Spectrometer (NAIS). Annually - averaged diurnal variation curves of 222Rn concentration showed a peak (~9.9 Bq m−3) at 0800 Local Time (LT) and a minimum (~5.4 Bq m−3) at 1800 LT. Diurnal variations of 222Rn concentration during winter, post-monsoon, and pre-monsoon seasons were almost similar in shape but with decreasing amplitudes in these seasons. However, during monsoon season, 222Rn concentration was the lowest and remained almost constant throughout the day. Monthly mean value of 222Rn concentration was the highest in December and the lowest in June. Polonium (218Po) concentration did not show any systematic diurnal variation. Results are explained in terms of surface meteorology, soil moisture, soil temperature, vertical wind velocity, local topography and development of atmospheric boundary layer. 222Rn concentration increased with soil moisture content of <16%, rapidly dropped down to dry soil values and then remained almost constant with increasing soil moisture. On the other hand, 222Rn concentration decreased with the increase of upward vertical wind velocity in the atmospheric boundary layer. The diurnal variations of ionization rate, directly estimated from 222Rn measurements, and calculated from ion concentration measurements showed some similarities but differed in their amplitudes. Annual effective dose of 222Rn (~0.075 mSv) as estimated from our measurements at Pune was found below the value prescribed by World Health Organization.

Surface measurements of the atmospheric electric field, conductivity, and the concentration and size distribution of submicron aerosols were made at Maitri, Antarctica, during the summer Indian Antarctic Expedition of 1996–1997. The main results obtained from these observations are summarized below: The classical concept of the global electric circuit is not validated from the diurnal variation curves of the atmospheric electric field observed during this period. The value of electrical conductivity at the ground surface does not show much diurnal variation. Aerosol size distributions at Maitri are generally trimodal and remain almost similar for several hours or even days in the absence of any meteorological disturbance. Total aerosol concentration increases by approximately an order of magnitude whenever a low-pressure system passes over the station. Observations of aerosols and conductivity made during the onward and return journeys of the cruise strongly support the transport of aerosol and trace gases with the seasonal northeasterly winds from the Indian subcontinent to the Indian Ocean. From the differences observed in latitudinal variation in aerosols and conductivity along the cruise route, one can conclude that the downward transport of the nucleation mode particles from the free troposphere to the marine boundary layer significantly contributes to the nucleation mode particle high concentrations observed up to ITCZ. Changes in the values of conductivity during two episodes of warm and cold fog are studied. Observations are interpreted in terms of ion-attachment and new particle generation processes.

The aim of this report is to document and summarize the results obtained in our wind tunnel experiments for a variety of phenomenon which need to be accounted in our understanding of the interactions of cloud electrification with its microphysics. The vertical wind tunnel developed at IITM has proved to be a good facility to investigate several critical problems in cloud microphysics. Several experiments conducted over last more than three decades in this wind tunnel provided some novel observations and large photographic data captured using a High Speed Camera on the deformation, oscillation, evaporation and breakup characteristics of charged/uncharged water drops of different sizes in absence/ presence of electric fields. However, in order to fill up the gap between the past studies mostly conducted under vertical configuration of electric field, main focus in our experiments was to study the effect of horizontal electric field (EH) on various microphysical processes in thunderclouds. This work has been extended by performing experiments on breakup of polluted and unpolluted water drops in electric field. The data has revealed some novel features of various microphysical processes occurring inside the thunderclouds.

PURPOSE:Ischemic cardiomyopathy (ICM) and non-ICM (NICM) causes of dilated cardiomyopathy with similar clinical presentation have different management and prognosis. This study employed myocardial perfusion imaging (MPI) to differentiate between the two using quantitative parameters in Indian population.METHODS AND MATERIALS:Fifty patients prospectively underwent MPI and 18F-fluorodeoxyglucose metabolism studies. P values (0.05 as significant) were calculated for the left ventricular ejection fraction (EF), end diastolic volume (EDV) at rest and stress, end systolic volume (ESV) at rest and stress, summed rest score (SRS), summed difference score (SDS), and eccentricity. On 6-month follow-up, rate of hospital admission, change in management and death was correlated for ICM and NICM. Coronary angiography (CAG) being gold standard, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and level of agreement were calculated for MPI.RESULTS:MPI and CAG had a moderate level of agreement (κ = 0.463) for differentiating ICM and NICM. The sensitivity, specificity, PPV, NPV, and diagnostic accuracy were 79.31%, 66.67%, 76.67%, 70.0%, and 74% for ICM and 66.67%, 79.31%, 70%, 76.67%, and 74% for NICM, respectively. Significant differences were seen in EDV stress (P = 0.045), EDV rest (P = 0.031), ESV rest (P = 0.034), SRS (P = 0.004), Left ventricular EF rest (P = 0.049) and SDS in ICM and NICM, respectively.CONCLUSION:EDV at rest and stress, ESV at rest, SRS, SDS, and EF at rest obtained using MPI provides precise quantitative information to differentiate ICM and NICM. It is wide and easy availability, noninvasiveness, objectivity, and near absence of complications favors it as a preferable diagnostic tool with its given sensitivity, specificity, and accuracy for the purpose.

The entirety of the Earth’s climate system is continuously bombarded by cosmic rays and exhibits about 2000 thunderstorms active at any time of the day all over the globe. Any linkage among these vast systems should have global consequences. Numerous studies done in the past deal with partial links between some selected aspects of this grand linkage. Results of these studies vary from weakly to strongly significant and are not yet complete enough to justify the physical mechanism proposed to explain such links. This review is aimed at presenting the current understanding, based on the past studies on the link between cosmic ray, lightning and climate. The deficiencies in some proposed links are pointed out. Impacts of cosmic rays on engineering systems and the possible effects of cosmic rays on human health are also briefly discussed. Also enumerated are some problems for future work which may help in developing the grand linkage among these three vast systems.

A total number of 109 new particle formation events identified in the ion-mobility spectra measured with a Neutral Cluster and Air Ion Spectrometer in the mobility range of 3.16-0.00133 cm(2) V-1 s(-1) (Diameter* range 0.36-47.1 nm) at a tropical site at Pune, (18.53 degrees N, 73.85 degrees E, 573 m amse India from March 08, 2010-December 31, 2012 are classified based on their shape characteristics under four categories. Most of these events occurred in the morning hours of the pre-monsoon season during the hottest months (April and May) of the year. The meteorological conditions and the changes in ion characteristics associated with some typical events are examined. Average ion-mobility spectrum for the event days shows a minimum in the negative big cluster ion (diameter, 0.85-1.6 nm) concentration and two maxima in the positive intermediate (diameter, 1.6-7.4 nm) and large ion (diameter, 7.4-47.1 nm) concentrations as compared to the average spectrum for all days. Analysis of 7-days airmass back trajectories shows that since the only source of big cluster ions is through the growth of small cluster ions (diameter, 0.36-0.85 nm) the growth of small to big cluster ions is faster when the airmass approaches our site from the land. Further, the concentrations of positive intermediate and light large (diameter, 7.4-22 nm) ions is more when the airmass approaches from the Arabian Sea.