Aerosol single-scattering albedo (SSA) is the most critical factor for the accurately calculating of aerosol radiative effects, however, the observation of vertical profiles of SSA is difficult to realize. Current assessments of aerosol radiative effects remain uncertain because of the lack of long-term, high-resolution vertical profiles of SSA observations. High-resolution SSA vertical profiles were observed in a semi-arid region of Northwest China during winter using a tethered balloon. The observed SSA vertical profiles were used to calculate the aerosol direct radiative forcing and radiative heating rates. Significant differences in the calculated radiative forcing were found (e.g., a 48.3% relative difference for the heating effect in the atmosphere at 14:00) between the observed SSA profiles and the constant assumption with SSA = 0.90. Diurnal variations in the vertical distribution of SSA decisively influenced direct radiative forcing of aerosols. Furthermore, high-resolution vertical profiles of absorbing aerosols and meteorological parameters provide robust observational evidence of the heating effect of an elevated absorbing aerosol layer. This study provides a more accurate calculation of aerosol radiative forcing using observed aerosol SSA profiles. The scarcity of single-scattering albedo (SSA) observations is the most critical factor limiting the accurate calculations of aerosol radiative effects. A tethered balloon platform was used to obtain long-term, high-resolution observations of the SSA and estimate aerosols' radiative effects. The relative differences in the heating rate and direct radiative forcing calculations using the observed SSA and a constant assumed SSA (i.e., ignoring the vertical distribution of absorbing aerosols) were quantified. The effects of diurnal variations in the vertical distribution of SSA on aerosol direct radiative forcing are summarized. This study has important scientific implications for assessing the radiative effects of aerosols in semi-arid regions, that are highly sensitive to climate change. Tethered balloon observations acquired high-resolution vertical aerosol single-scattering albedo (SSA) profiles The assumed SSA profiles caused a 48.3% relative error in radiative forcing in the atmosphere compared to the observed profiles at 14:00 A robust observational evidence of atmospheric heating by absorbing aerosols above the boundary layer was provided

Aerosol optical properties, including absorption and scattering coefficients (B-abs, and B-scat), extinction coefficient (B-ext), single scattering albedo (SSA), and so forth, are critical metrics to estimate the radiative balance of the atmosphere. However, their ground measurements are sparsely distributed in the world, where Central Asia is void in these measurements. We had been performing the measurements of AOPs and BC with a photoacoustic extinctiometer (PAX) in Jimunai, a border town of China neighboring Kazakhstan, Central Asia, from Aug 2016 to Apr 2019. This three-year study first reported statistically significant trends of B-abs, B-scat, B-ext, SSA, and derived concentrations of BC (Mann-Kendall trend test, p-value 0.05) in the Central-Asian area. B-abs and B-scat show increasing trends and SSA was decreasing determined by the greater increasing pace of B-abs than B-scat. Seasonal and diurnal variations of the AOPs were associated with climate shift and residents' commute activity, respectively. The difference in the magnitudes and trends of AOPs between the measurements and satellites' observations advise that more care should be invested when choosing remote-sensing data to represent the AOPs at a specific site. The increasing trend of derived BC concentrations is reflected in the deposition record of BC in a snowpit of the nearby Muz Taw glacier. We suppose that the dramatically increasing BC particles emitted from Jimunai are significant factors triggering the melting of the adjacent mountain glaciers. The outflow of dust from the neighboring Gurbantiinggiit Desert could occasionally invade into Jimunai and deteriorate the local air quality, as evidenced by a probable dust event captured by the PAX on Feb 15, 2018. Finally, we outlook the future perspectives of measurements in Jimunai as a long-standing station.

Arctic navigability is crucial to the global economy and landscape, while there is an omission in understanding how Arctic navigability changes as a function of 1.5 degrees C of the Paris Agreement. This study investigated the impact of 1.5 degrees C global warming above the preindustrial level on sea ice conditions and accessibility of the Northern Sea Route (NSR) and Northwest Passage (NWP) with the Polar Operational Limit Assessment Risk Indexing System and new risk demarcation criteria. The Arctic is colder on the Canadian side than on the European side under 1.5 degrees C warming. Sea ice is mostly less than three years old, and the younger, thinner and less concentrated ice is mainly in the seas along the NSR. Ships above Polar Class (PC) 6 might be unimpeded along two passages all the year. Besides, the NSR and NWP have great potential for PC6 ships in October-December, while it is only the NSR for PC7 ships. Caution is still required when navigating the western East Siberian Sea, its surrounding straits, and the Parry Channel. These changes in hydrological conditions are important for global shipping, and this work is helpful for supporting coordinated international decision-making.

The Northeast Passage (NEP) holds immense potential as a link for maritime transport activities between Europe and Asia, primarily due to the extended sailing season resulting from global warming. However, the economic viability of the Arctic shipping route remains disputed. This study aims to comprehensively evaluate the feasibility of container transportation along the NEP compared to that along the Suez Canal Route (SCR) by using current (2021-2023) and future (2025-2065) scenarios. The results reveal that larger vessels have lower CO2 emissions and costs than small vessels in the NEP, but the costs for larger vessels in the NEP are still higher than those in the SCR throughout both summer and winter seasons under the current scenario. The outcomes also show that a progressive carbon tax scheme will increase the unit shipping costs for all routes in the future scenario, with the NEP being most economically viable during summer. Furthermore, the extended navigable period (NP) bolsters the NEP's economic cost advantage during a seasonal period. Nevertheless, from a year-round operations standpoint, the NEP remains less competitive than the SCR before 2065. The conclusions drawn from this research serve as a significant resource for decision-makers when formulating operational plans.

Dust aerosol has an impact on both the regional radiation balance and the global radiative forcing estimation. The Taklimakan Desert is the focus of the present research on the optical and micro-physical characteristics of the dust aerosol characteristics in Central Asia. However, our knowledge is still limited regarding this typical arid region. The DAO-K (Dust Aerosol Observation-Kashgar) campaign in April 2019 presented a great opportunity to understand further the effects of local pollution and transported dust on the optical and physical characteristics of the background aerosol in Kashgar. In the present study, the consistency of the simultaneous observations is tested, based on the optical closure method. Three periods dominated by the regional background dust (RBD), local polluted dust (LPD), and Taklimakan transported dust (TTD), are identified through the backward trajectories, combined with the dust scores from AIRS (Atmospheric Infrared Sounder). The variations of the optical and micro-physical properties of dust aerosols are then studied, while a direct comparison of the total column and near surface is conducted. Generally, the mineral dust is supposed to be primarily composed of silicate minerals, which are mostly very weakly absorbing in the visible spectrum. Although there is very clean air (with PM2.5 of 21 mu g/m(3)), a strong absorption (with an SSA of 0.77, AAE of 1.62) is still observed during the period dominated by the regional background dust aerosol. The near-surface observations show that there is PM2.5 pollution of similar to 98 mu g/m(3), with strong absorption in the Kashgar site during the whole observation. Local pollution can obviously enhance the absorption (with an SSA of 0.72, AAE of 1.58) of dust aerosol at the visible spectrum. This is caused by the increase in submicron fine particles (such as soot) with effective radii of 0.14 mu m, 0.17 mu m, and 0.34 mu m. The transported Taklimakan dust aerosol has a relatively stable composition and strong scattering characteristics (with an SSA of 0.86, AAE of similar to 2.0). In comparison to the total column aerosol, the near-surface aerosol has the smaller size and the stronger absorption. Moreover, there is a very strong scattering of the total column aerosol. Even the local emission with the strong absorption has a fairly minor effect on the total column SSA. The comparison also shows that the peak radii of the total column PVSD is nearly twice as high as that of the near-surface PVSD. This work contributes to building a relationship between the remote sensing (total column) observations and the near-surface aerosol properties, and has the potential to improve the accuracy of the radiative forcing estimation in Kashgar.

Atmospheric aerosols are very crucial from air pollution and health perspective as well as for regional and global climate. This paper attempts to summarize the aerosol loading and their properties such as Aerosol Optical Depth (AOD), Single Scattering Albedo (SSA), Angstrom exponent, and Radiative forcing, over India. All the above mentioned parameters have shown significant variability with change in the site and season. From various studies it was observed that AOD is relatively higher over Northern part of India as compared to Southern and Eastern part. Generally, lower values of SSA were observed over all sites during winter and post-monsoon seasons which indicates the dominance of absorbing type aerosol during these seasons. Also the ARF within atmosphere showed comparatively higher values during November-December and lower value during August and September all over the India. The current state of knowledge about aerosol sources, interactions and their effects on environment is limited because of its complexity. Therefore, more focused research in needed to understand the aerosol's role in climatic phenomenon.

Although a rapid decrease in sea ice due to global warming has improved the navigable potential of the Arctic passages, the extent to which this area will become viable for commercial shipping in the future remains unclear. This study investigated the accessibility of the Northern Sea Route and Northwest Passage under global warming of 2 degrees C and 3 degrees C. We applied the Polar Operational Limit Assessment Risk Indexing System to measure navi-gability by considering the impacts of sea ice and ice resistance of ships. Except for the Parry Channel, surface air temperature is positive in the Seas along two passages in September under 2 degrees C warming. With global warming of 3 degrees C, the warming area extends northward, and the concentration of sea ice drops below 20%. The thickness of the sea ice is still substantial in the eastern Beaufort Sea and the waters within the Canadian Arctic Archipelago and north of Greenland, both of which can restricting the opening of the Arctic passages. Temperature increases cause sea ice to be younger and are more pronounced in the seas on the European side of the Arctic. The results indicate that changes in sea ice improve the navigability of the Arctic passages. Ships in Polar Class 6 may be unimpeded along two Arctic passages in November from 2 degrees C warming onward, whereas ordinary ships may be capable of passing the Northern Sea Route with global warming of 3 degrees C, with maximum potential in September. This study provides an important reference for planning global shipping in the Arctic in the future, even with some uncertainty in the model projections.

The navigation potential of the Arctic has improved with the rapid retreat of sea ice under continuous warming. The comprehensive evaluation of Arctic accessibility for low ice-breaking ships (civil use) in the mid-century is important to support coordinated international decision-making. In this study, the hydrological conditions and navigation potential in key areas and crucial straits along the Northern Sea Route (NSR) and Northwest Passage (NWP) were assessed under Shared Socioeconomic Pathways (SSPs) using the Polar Operational Limit Assessment Risk Indexing System. The results showed that the most critical areas for navigation in the mid-century (2046-2055) are the waters around the New Siberian Islands and within the Parry Channel. Arctic navigability improves from SSP1-2.6 to SSP2-4.5 to SSP5-8.5, and the accessibility for PC7 ships under SSP2-4.5 is even better for OW ships under SSP5-8.5. The route on the north side of the New Siberian Islands is a relatively good choice within the NSR, and the southern route has a better navigation potential than the Parry Channel within the NWP. In addition, the accessibility of the Dmitrii Laptev Strait is better than that of the Sannikov Strait at a monthly scale, although the latter has more navigable days. However, there is little difference in accessibility between the eastern and western parts of the Parry Channel. The best navigation potential through the above straits is in September for ordinary ships, and the optimal time window is delayed and extended for PC7 ships. The results can serve as references for policy-making and navigation planning in the Arctic.

In this work we present the results of the four-years (2015-2018) data-analysis of aerosols optical extensive properties such as scattering (sigma(sc)) and backscattering coefficients (sigma(bsc)), scattering Angstrom exponent (SAE), single scattering albedo (SSA), and asymmetry parameter (g). They were measured at three GAW (Global Atmosphere Watch-WMO) regional observatories in the South of Italy: CGR (Capo Granitola), LMT (Lamezia Terme) and ECO (Lecce). The aim of this work is to characterize the optical properties of the aerosols, in terms of scattering, absorption and radiative forcing, to study their relationship with the equivalent black carbon (eBC) mass concentration, meteorological parameters and to evaluate their variability in the Central Mediterranean area. From the mean values of SAE (1.73 ECO, 1.93 LMT) and SSA (0.81 ECO, 0.78 LMT) observations can be argued that ECO and LMT are mainly influenced by ultrafine particles, while CGR, with mean values of SAE and SSA of 1.15 and 0.87, respectively, is characterized by natural sources, mainly marine. In all stations, g(550) is very similar, 0.68 at CGR and 0.63 at LMT, with the greatest value (0.70) at ECO. The aerosol optical properties, at the three stations, are significantly influenced by the meteorological conditions. The daily pattern for eBC concentration at ECO and LMT is essentially influenced by local activities, namely due to vehicular traffic, and, for LMT, to local sea-land breeze circulation. Wood burning is the main source contribute to eBC concentration in the remote site of CGR. Aerosols optical properties were analysed in the cold (from October to March) and warm (from April to September) period in the three observatories to highlight the behaviour of optical parameters as a response to changing black carbon concentration, especially, from local sources. As expected, three observatories exhibited low values of SSA, during the cold season, 0.87 at CGR, 0.78 at LMT and 0.80 at ECO, which confirm an increment of industrial/traffic and wood combustion contributions at the three observatories. SSA values are very similar in warm and cold period, especially in the middle part of the day. A persistent and important results in the findings of this study is that aerosol optical properties vary widely from station to station throughout the central Mediterranean basin. Thus, the wide spatial and temporal variability of aerosol characteristics in the basin need additional investigations to study the relationship between particle size distribution, optical parameters and local sources contribution at the three sites. Further, our results show a negative radiative forcing of aerosols, with mean values of -58.8 at CGR, -45.4 at LMT and - 55.9 at ECO, according also to several studies in central Mediterranean area.

The present work is aimed to analyze aerosols optical properties and to estimate aerosol radiative forcing (ARF) from January to December 2013, using sky radiometer data over Rohtak, an urban site in North-Western India. The results reveal strong wavelength dependency of aerosol optical depth (AOD), with high values of AOD at shorter wavelengths and lower values at longer wavelength during the study period. The highest AOD values of 1.07 +/- 0.45 at 500 nm were observed during July. A significant decline in Angstrom exponent was observed during April-May, which represents the dominance of coarse mode particles due to dust-raising convective activities. Aerosols' size distribution exhibits a bimodal structure with fine mode particles around 0.17 mu m and coarse mode particles with a radius around 5.28 mu m. Single scattering albedo values were lowest during November-December at all wavelengths, ranging from 0.87 to 0.76, which corresponds to the higher absorption during this period. Aerosols optical properties retrieved during observation period are used as input for SBDART (Santa Barbara DISORT Atmospheric Radiative Transfer) to estimate the direct ARF at the surface, in the atmosphere and at the top of the atmosphere (TOA). The ARF at the TOA, surface and in the atmosphere are found to be in the range of -4.98 to -19.35 W m(-2), -8.01 to -57.66 W m(-2) and +3.02 to +41.64 W m(-2), respectively. The averaged forcing for the whole period of observations at the TOA is -11.26 W m(-2), while at the surface it is -38.64 W m(-2), leading to atmospheric forcing of 27.38 W m(-2). The highest (1.168 K day(-1)) values of heating rate was estimated during November, whereas the lowest value (0.084 K day(-1)) was estimated for the February.