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An editorial is presented on the outcomes of the 28th United Nations Climate Change Conference of the Parties (COP-28) held in Dubai, emphasizing the importance of international collaboration to address climate change. Topics include the conference's goals to limit global temperature increases, India's climate goals, and developments in climate finance, including the loss and damage fund.

The article offers information on the global acknowledgment of climate change as a reality caused by human intervention, with topics including the consequences of climate change, regional and global environmental concerns, and unique challenges faced by India, particularly the receding Sundarbans mangrove forest.

The article discusses the need for rural electrification using hybrid solar-wind energy systems to address the challenges of climate change and increasing energy demand in India. Topics include the rise in greenhouse gas concentrations; the importance of renewable energy sources like solar and wind; and the role of hybrid energy systems in providing a balanced solution for rural electrification while reducing the impact on climate.

The article focuses on the environmental impact and heritage preservation of Lonar Lake, a unique geological formation in India. It addresses the effects of climate change on heritage sites, particularly those vulnerable to rising sea levels and emphasizes the urgent need for mitigation measures. It also discusses the ecological damage and degradation faced by Lonar Lake due to shifting perimeters and other factors, highlighting the importance of immediate conservation efforts.

An editorial is presented on challenges faced by Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) to develop healthy ecosystems and biodiversity that are fundamental to life on Earth. Topics include threat to fishing cats is habitat destruction due to anthropogenic activities and climate change; and India's wetlands are at risk of destruction due to human settlement, drainage for agriculture, pollution and logging.

An introduction is presented in which the editor discusses several articles published within issue on topics related to climate change and health.

Climate change has great significance in Asia in general, and India in particular; and atmospheric aerosols have a decisive role in this. The climate forcing potential of aerosols is closely linked to their optical, microphysical and chemical properties. Systematic efforts to characterize these properties over the Indian region started about 5 decades ago, and evolved over the years through concerted efforts in the form of long-term scientific programmes as well as concerted fields experiments. All these have resulted in this activity becoming one of the most vibrant fields of climate research in India and have brought several important issues in the national and international foci. The field experiment, RAWEX--GVAX (Regional Aerosol Warming Experiment--Ganges Valley Aerosol Experiment), conducted during 2011-12 jointly by the US Department of Energy, Indian Space Research Organization and Department of Science and Technology, has emerged as a direct outcome of the above efforts. This overview provides a comprehensive account of the development of aerosol--climate research in India and south Asia, and the accomplishment and newer issues that warranted the above field campaign. Details of RAWEX--GVAX, the major outcomes and the subsequent and more recent efforts are presented, followed by the way forward in this field for the next several years to come. [ABSTRACT FROM AUTHOR]

In this paper, we evaluate the performance of the chemical transport model 'CHIMERE' over large Indian region (4-37.5°N; 67-88.5°E) for multiple years (2006, 2007 and 2008) by comparing the model simulations with concurrent aerosol measurements from different locations. Model simulated near-surface black carbon mass concentrations agreed satisfactorily with measurements at various locations (oceanic, inland and island sites), in general, except during monsoon months, when the model under-predicted the measurements. Similar results were obtained when model simulated column integrated PM10 mass concentrations were correlated with MODIS-derived aerosol optical depth (AOD), using AOD as a proxy for aerosol loading. The under-performance of the model during monsoon arises, at least partly, due to the model-simulated rainfall being higher than the actual rainfall over the Indian domain, during the monsoon season. Notwithstanding these, the general performance of the CHIMERE model to simulate aerosol loading over Indian domain during dry months is, in general, found to be satisfactory. [ABSTRACT FROM AUTHOR]

In order to understand the regional climate implications of aerosols over Indo-Gangetic Plains (IGP), a major Indo-US field experiment, Ganges Valley Aerosol Experiment (GVAX) was conducted during 2011-12. Atmospheric Radiation Measurement (ARM) mobile facility (AMF) was deployed at the northern Indo-Gangetic Plain over the high-altitude site, Manora Peak, Nainital (29°21'33.84"N, 79°27'29.27"E, 1980 m amsl) in Central Himalayas, for an year-round meas- urement of aerosols, clouds and other climate-relevant atmospheric parameters. One of the objectives of GVAX was examining the ability of models to simulate aerosols over Indian region and validate the simulations. In part-1 of this two-part paper, we examine use of the chemical transport model 'CHIMERE' to simulate aerosol fields over Indian region (4-37.5°N; 67-88.5°E) for multiple years (2006, 2007 and 2008) by simulating the spatial and temporal distribution of PM10, BC mass concentrations and OC/BC ratios. It is seen that the model successfully captures the broad features of the regional distribution of aerosols, including the most conspicuous IGP hotspot and its seasonality. [ABSTRACT FROM AUTHOR]

Even though satellite observations are the most effective means to gather global information in a short span of time, the challenges in this field still remain over continental landmass, despite most of the aerosol sources being land-based. This is a hurdle in global and regional aerosol climate forcing assessment. Retrieval of aerosol properties over land is complicated due to irregular terrain characteristics and the high and largely uncertain surface reflection which acts as 'noise' to the much smaller amount of radiation scattered by aerosols, which is the 'signal'. In this paper, we describe a satellite sensor - the 'Aerosol Satellite (AEROSAT)', which is capable of retrieving aerosols over land with much more accuracy and reduced dependence on models. The sensor, utilizing a set of multi-spectral and multi-angle measurements of polarized components of radiation reflected from the Earth's surface, along with measurements of thermal infrared broadband radiance, results in a large reduction of the 'noise' component (compared to the 'signal'). A conceptual engineering model of AEROSAT has been designed, developed and used to measure the landsurface features in the visible spectral band. Analysing the received signals using a polarization radiative transfer approach, we demonstrate the superiority of this method. It is expected that satellites carrying sensors following the AEROSAT concept would be 'self-sufficient', to obtain all the relevant information required for aerosol retrieval from its own measurements. [ABSTRACT FROM AUTHOR]

During a series of measurements, simultaneous measurements were made of spectral aerosol optical depths (AOD), black carbon (BC) mass concentration, total and size segregated composite aerosol mass concentrations at the second campus of Indian Institute of Science (IISc), Challakere, Karnataka. Surprisingly, most of the aerosol mass is found in the submicron size range, which is unusual for a dry region. Unexpectedly large enhancement in BC aerosol concentration was observed during the morning hours (6-8 a.m.), both during summer and winter, which is mysterious and hence requires further study. However, BC mass fraction, which is one of the most important climaterelevant parameters was 3.3% of total aerosol mass, implying a significantly low aerosol-induced absorption of solar radiation and hence consequent atmospheric warming. Based on our initial measurements as well as 11 years of satellite data analysis, we conclude that this location is best suited for establishing a climate observatory. [ABSTRACT FROM AUTHOR]

Atmospheric chemistry is a branch of atmospheric science where major focus is the composition of the Earth's atmosphere. Knowledge of atmospheric composition is essential due to its interaction with (solar and terrestrial) radiation and interactions of atmospheric species (gaseous and particulate matter) with living organisms. Since atmospheric chemistry covers a vast range of topics, in this article the focus is on the chemistry of atmospheric aerosols with special emphasis on the Indian region. I present a review of the current state of knowledge of aerosol chemistry in India and propose future directions. [ABSTRACT FROM AUTHOR]

The author offers insights on environmental concerns associated with carbon dioxide emissions associated with the airline industry. Topics discussed include the contribution of greenhouse gases (GHG) to global warming according to the United Nations (UN) Intergovernmental Panel on Climate Change (IPPCC), the smoke produced by the burning of aviation fuel, and the carbon footprints linked to long-distance air travel.

Knowledge of aerosol radiative forcing over land is essential to answer crucial questions related to climate change. Retrieval of aerosol properties over land is complicated due to irregular terrain characteristics and high surface reflection. The retrieval of algorithms used in conventional satellite sensors for continental regions is not completely free from the high reflectance effect and hence leads to large uncertainties in the retrieved parameters. We propose a dedicated satellite sensor namely multi-angle polarization imager (MAPI). The main characteristic of MAPI is multi-spectral and multi-angle measurements of polarized components of reflected radiation from the Earth. The proposed sensor has capability of aerosol retrieval over land. The sensor also has the ability to discriminate dust aerosols (which is the major natural aerosol over land) from other aerosols (using infrared radiance). This is the first step towards separating natural and anthropogenic aerosols, which is needed for the scientific community at large. [ABSTRACT FROM AUTHOR]

The article presents author's comments on the issues related to Earth. It focuses on the climate change and increasing global temperature. It mentions that the anthropogenic emission of greenhouse gases is the major contributor to the risk. It states that there is an increasing demand for actions to control the emissions that are effecting the climate.

An introduction to the journal is presented in which the guest editor discusses the Mars Orbiter Mission (MOM) of the Indian Space Research Organization for the launch of an elliptical orbit in Mars.

Continuous analytical measurements of the loading and optical properties of near-surface aerosols over the megacity Bengaluru, in south India, are examined for the impact of the national lockdown (LD) associated with COVID-19 pandemic. The near total shutdown of rail, road, and air traffic as well as total closure of most of the business establishments and IT industry, especially during the first phase of the LD, is found to dramatically reduce black carbon (BC) abundance. Within one week of the first week of the LD phase 1 (LD1), the ambient BC concentration at the urban centre came down to levels comparable to those reported for remote rural locations, primarily due to >60% reduction in BC from fossil fuel (BCff) emissions. On the other hand, BC from biomass burning (BCwb) did not show any conspicuous impact. Consequently, the fraction of BCwb to BC more than doubled and the spectral absorption coefficient increased from ~1.15 to ~1.4. The single scattering albedo increased from its prevailing mean value 0.66 before LD to 0.74 during LD1 and then gradually decreased to 0.68 with increasing relaxations on vehicular traffic. The results reveal the unequivocal role of vehicular emissions in impacting the aerosol loading and their optical properties over Bengaluru. The study also shows how the environment responded to the gradual relaxations in the subsequent phases of LD. It is interesting to note that a few spells of strong rainfall towards the fourth phase of the LD impacted the aerosols non-selectively leading to sharp decrease in all the quantities. However, owing to the non-selective nature of the washout this large reduction in loading did not impact the single scattering albedo, unlike the case with the LD. [ABSTRACT FROM AUTHOR]

Long-term and continuous measurements of aerosol concentration and optical properties from the Challakere Climate Observatory, located in a remote rural semi-arid region northwest of Bengaluru, are examined for the impact of the prolonged and phased national lockdown during the COVID-19 pandemic. The analyses revealed that the lockdown, which almost brought all the anthropogenic activities (particularly associated with fossil fuel use such as in transport and industrial sectors) to a standstill and then slowly relaxed in phases, had very little impact on the aerosol properties at this remote site, in sharp contrast to the impacts seen in the major urban conglomerate, Bengaluru, located about 230 km southeast to Challakere. Rather than impacts from anthropogenic sources associated with fossil fuel combustion, the aerosol characteristics at Challakere are strongly influenced by regional and synoptic meteorology. The findings re-emphasize that the emissions from fossil fuel combustion in industrial and automobile sector are the major source of aerosols (especially absorbing type) over urban and semi-urban environments. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses articles in the issue including field observations to understand temperature and precipitation changes in the Himalayas, mass balance and ice thickness in assessing the effect of changing climate, and mass loss analysis by geodetic method.

The author comments on the United Nations (UN) Climate Change Conference held in Lima, Peru in December 2014, the 20th yearly session of the Conference of the Parties (COP 20) of the UN Framework Convention on Climate Change (UNFCCC). Participants reached a consensus to plan their national contributions to reduce emissions, or Intended Nationally Determined Contributions (INDC), which may determine future mitigation strategies. Issues raised by the event include the feasibility of INDC.

An introduction to a series of articles about the regional aerosol warming experiment - Ganges Valley aerosol experiment (RAWEX-GVAX) published within the issue is presented.

Extensive measurements of columnar aerosol optical depth (AOD), composite (MT) and black carbon aerosol mass (MB) concentrations were made over the tropical Indian and Southern Oceans as a part of the Pilot Expedition to the Southern Ocean during the boreal winter. The AOD, MT and MB show large latitudinal gradient towards south up to ITCZ. Beyond ITCZ, up to 56°S, AOD and MB show very low and steady values. However MT shows large variations in the Southern Ocean due to the enhanced production of sea salt aerosols associated with high sea surface winds. The short wave aerosol radiative forcing at the surface over north of equator is in the range - 10 to - 23 W m-2, whereas that over the Southern Ocean was in the range - 4 to - 5 W m-2. The corresponding atmospheric forcing was in the range of 6-13 W m-2 and 0.8-1.4 W m-2. This large north-south change in the aerosol radiative forcing has important implications to the meridional circulation and hence to climate. [ABSTRACT FROM AUTHOR]

An extensive field study, RAWEX--GVAX, was carried out during a 10-month (June 2011-March 2012) campaign at ARIES, Nainital and observations on a wide range of parameters like physical and optical properties of aerosols, meteorological parameters and boundary layer evolution were made. This work presents results obtained from high-frequency (four launches per day), balloon-borne observations of meteorological parameters (pressure, temperature, relative humidity, wind speed and wind direction). These observations show wind speed as high as 84 m/s near the subtropical jet. It is shown that reanalysis wind speeds are in better agreement at 250 hPa (altitude of subtropical jet) than those above or below this value (100 hPa or 500 hPa). These observations also demonstrate that AIRS-derived temperature profiles are negatively biased in the lower altitude region, whereas they are positively biased near the tropopause. WRF simulated results are able to capture variations in temperature, humidity and wind speed profile reasonable well. WRF and AIRS-derived tropopause height, tropopause pressure and tropopause temperature also show agreement with radiosonde estimates. [ABSTRACT FROM AUTHOR]

We present the measurements of cloud-base height variations over Aryabhatta Research Institute of Observational Science, Nainital (79.45°E, 29.37°N, 1958 m amsl) obtained from Vaisala Ceilometer, during the nearly year-long Ganges Valley Aerosol Experiment (GVAX). The cloud-base measurements are analysed in conjunction with collocated measurements of rainfall, to study the possible contributions from different cloud types to the observed monsoonal rainfall during June to September 2011. The summer monsoon of 2011 was a normal monsoon year with total accumulated rainfall of 1035.8 mm during June-September with a maximum during July (367.0 mm) and minimum during September (222.3 mm). The annual mean monsoon rainfall over Nainital is 1440 ± 430 mm. The total rainfall measured during other months (October 2011-March 2012) was only 9% of that observed during the summer monsoon. The first cloud-base height varied from about 31 m above ground level (AGL) to a maximum of 7.6 km AGL during the summer monsoon period of 2011. It is found that about 70% of the total rain is observed only when the first cloud-base height varies between surface and 2 km AGL, indicating that most of the rainfall at high altitude stations such as Nainital is associated with stratiform low-level clouds. However, about 25% of the total rainfall is being contributed by clouds between 2 and 6 km. The occurrences of high-altitude cumulus clouds are observed to be only 2-4%. This study is an attempt to fill a major gap of measurements over the topographically complex and observationally sparse northern Indian region providing the evaluation data for atmospheric models and therefore, have implications towards the better predictions of monsoon rainfall and the weather components over this region. [ABSTRACT FROM AUTHOR]

The RAWEX-GVAX field campaign has been carried out from June 2011 to March 2012 over a high altitude site Manora Peak, Nainital (29.4°N; 79.2°E; 1958 m amsl) in the central Himalayas to assess the impacts of absorbing aerosols on atmospheric thermodynamics and clouds. This paper presents the preliminary results of the observations and data analysis of the Doppler Lidar, installed at Nainital. Strong updrafts with vertical winds in the range of ~2-4 ms-1 occurred during the daytime and throughout the season indicating thermally driven convection. On the other hand during nighttime, weak downdrafts persisted during stable conditions. Plan Position Indicator scan of Doppler Lidar showed north-northwesterly winds in the boundary layer. The mixing layer height, derived from the vertical velocity variance, showed diurnal variations, in the range ~0.7-1 km above ground level during daytime and very shallow during nighttime. [ABSTRACT FROM AUTHOR]