Manora Peak Research Articles

Effect of cloud reflection on direct aerosol radiative forcing: a modelling study based on lidar observations

In the present study, we have utilized light detection and ranging (lidar) and sun photometer observations to derive vertical distribution and optical depth of aerosols over Manora Peak (29.54° N, 79.45° E, 1956 m above mean sea level). The vertical profiles of aerosols revealed the presence of aerosol layer at 0.75 km above the surface and contribute about 68% to the total aerosol optical depth (AOD) at 0.50 µm wavelength during the observational period. Our observational site being a mountainous terrain site, we observe cloud formation taking place over the surface most of the time. In this context, it is essential to quantify the effect of cloud reflection on aerosol radiative forcing. In order to address the above issue, we have approached an integral way that combining model with observations. Optical Properties of Aerosols and Clouds (OPAC) model is used to derive aerosol and cloud optical properties. The estimated average single scattering albedo is about 0.85 for an AOD of 0.13 at 0.50 µm wavelength. The assumed effective radius, number density of cloud drop and vertical extent of cloud are 7.33 μm, 170 cm–3 and 100 m, respectively, which gives the visible optical depth of 4.0 at 0.50 µm wavelength. For mean conditions of aerosol optical properties and 25% of cloud cover, the diurnal mean surface aerosol radiative forcing is about −10.0 W m−2 (for aerosol above and below the cloud case). The top of the atmospheric aerosol radiative forcing is in the range of +6.5 W m−2 to +0.5 W m−2, and atmospheric forcing (AF) ranges from +16.5 W m−2 to +10.5 W m−2 when the aerosol layer is above and below the cloud. The cloud layer enhances and reduces the AF as compared to clear sky by 4.5 Wm−2 and 1.5 Wm−2 when aerosol layer is mostly above the cloud and below the cloud, respectively. Hence, the present study emphasizes the importance of the knowledge of cloud properties along with the aerosol vertical profiles in cloudy atmosphere.

Estimation of the mixing layer height over a high altitude site in Central Himalayan region by using Doppler lidar

A Doppler lidar was installed at Manora Peak, Nainital (29.4°N; 79.2°E; 1958 amsl) to estimate mixing layer height for the first time by using vertical velocity variance as basic measurement parameter for the period September–November 2011. Mixing layer height is found to be located ~0.57±0.1 and 0.45±0.05km AGL during day and nighttime, respectively. The estimation of mixing layer height shows good correlation (R2>0.8) between different instruments and with different methods. Our results show that wavelet co-variance transform is a robust method for mixing layer height estimation.

Aerosol vertical profiles strongly affect their radiative forcing uncertainties: study by using ground-based lidar and other measurements

In the present study, we illustrate for the first time that direct aerosol radiative forcing has large uncertainty due to diversity in simulated vertical profile of aerosol over Manora Peak, Nainital (considered to be free troposheric site). In order to have a comprehensive picture, we choose March and October months as representative months of high and low aerosol mass loading over the site, respectively. Monthly averaged aerosol optical depths (AODs) at 0.5 μm are ∼0.30 (±0.02) and 0.13 (±0.01), respectively, during the above months. The derived aerosol extinction profile showed an elevated aerosol layer with maximum extinction of ∼0.10 ± 0.01 km−1 (0.08 ± 0.02 km−1) at ∼1.12 km (0.75 km) during March (October) month. The elevated aerosol layer contributed 44% and 68% to the total AOD during March and October months, respectively. The observed AODs at different wavelengths and black carbon (BC) measurements were used to estimate the other aerosol optical parameters, which are crucial in aerosol radiative forcing. The derived aerosol extinction profile has been used in radiative transfer (RT) model in addition to the standard aerosol extinction profile of RT model along with the aerosol optical properties. Our results indicate that there is an increment in surface radiative forcing, which is ∼10% (25%) due to the insertion of derived aerosol extinction profile for the same columnar properties of aerosols during March (October). Moreover, we found that higher the aerosol layer contribution to the total AOD, the more the uncertainty in aerosol radiative forcing. Apart from this, significant differences were also found in atmospheric forcing at each altitude due to variation in vertical profile of aerosol extinction, which leads the modification of the thermal structure of the atmosphere. Hence, our study has emphasized the importance of proper selection of aerosol vertical profile to obtain more realistic values of radiative forcing.

Characteristics of black carbon over Delhi and Manora Peak—a comparative study

AbstractThe characteristics of aerosol black carbon (BC) were studied at two different climatic regimes, i.e. Delhi and Manora Peak during winter and spring of 2007. Spring BC was found to be ∼59% lower at Delhi and ∼23% higher at Manora Peak than their corresponding winter BC. Diurnal BC variation showed two enhanced peaks at Delhi (morning and night) whereas a single late afternoon peak at Manora Peak. Delhi BC showed a clear correlation with prevailing winds whereas no correlation was observed at Manora Peak. The major contribution of BC at Manora Peak can be expected from biomass burning while at Delhi fossil fuel dominates. Copyright © 2012 Royal Meteorological Society

Black carbon aerosols over Manora Peak in the Indian Himalayan foothills: implications for climate forcing

This letter presents the contribution of black carbon (BC) to the total aerosol optical depth (AOD) and subsequently to the direct radiative forcing (DRF) at Manora Peak in the Indian Himalayan foothills. Measurements of the chemical composition of aerosols, carried out from July 2006 to May 2007, together with concurrently measured BC mass concentrations were used in an aerosol optical model to deduce the radiatively important aerosol optical parameters for composite aerosols. On the other hand, BC mass concentrations alone were used in the optical model to deduce the optical parameters solely for BC aerosols. The derived aerosol optical parameters were used independently in a radiative transfer model to estimate the DRF separately for composite and BC aerosols. The average BC mass concentration was found to be 0.98 (±0.68) μg m−3 during the entire observation period, which contributes <3% to the total aerosol mass and ∼17% to the total AOD at Manora Peak. The mean surface forcing was found to be − 14.0 (±9.7) and − 7.4 (±2.1) W m−2, respectively for composite and BC aerosols whereas mean atmospheric forcing was about +14 (±10) and +10 (±3) W m−2 for these aerosols. These results suggest that BC aerosols exert relatively large surface heating (∼45% higher) as compared to composite aerosols and contribute ∼70% to the total atmospheric forcing at Manora Peak. Such a large warming effect of BC may affect the strength of Himalayan glaciers, monsoon circulation and precipitation over the Indian region.

Aerosol optical properties over Delhi and Manora Peak during a rare dust event in early April 2005

Dust storm events are annual phenomena observed over the Indo-Gangetic plain (IGP) during the pre-monsoon period (May–June). These dust storms affect the air quality, weather conditions and radiation budget of the region. In this paper we characterize the aerosol optical parameters associated with a rare dust storm event that hit the IGP during early April 2005. This event was considered rare as it occurred much earlier than the general occurrence of dust storms in India (May–June), and in the year 2005, the warmest year in the span of the previous hundred years. In this study we considered the optical aerosol parameters for two places in the IGP: Delhi (28.5° N, 77.2° E, 325 m asl) and the high altitude station, Manora Peak (29.4° N, 79.5° E, 1958 m asl). Of the two selected stations, Delhi represents a highly populated and polluted location whereas Manora Peak represents a cleaner location in the central Himalayan region. During this dust storm event, the aerosol optical depth (AOD) was observed to increase considerably. The increment was 2.6–4.6 times over Delhi and 1.6–3.2 times over Manora Peak at wavelengths 380 and 1020 nm, respectively, with respect to the background values, whereas the Ångström exponent (α) for both the stations remained close to zero during the event. The effect shows a considerable increase in direct dust radiative forcing in terms of a reduction in the broadband global irradiance for Delhi as well as for Manora Peak stations. The direct aerosol radiative forcing thus obtained was about 34% in the 400–1100 nm wavelength band at Manora Peak.

Radiative effects of elevated aerosol layer in Central Himalayas

Systematic observations of light detection and ranging (LIDAR) to detect elevated aerosol layer were carried out at Manora Peak (29.4° N, 79.5° E, ∼1960 m a.s.l), Nainital, in the Central Himalayas during January–May 2008. In spite of being a remote, high-altitude site, an elevated aerosol layer is observed quite frequently in the altitude range of 2460–4460 m a.s.l with a width of ∼2 km during the observation period. We compare these profiles with the vertical profiles observed over Gadanki (13.5° N, 79.2° E, ∼370 m a.s.l), a tropical station, where no such elevated aerosol layer was found. Further, there is a steady increase in aerosol optical depth (AOD) from January (winter) to May (summer) from 0.043 to 0.742, respectively, at Manora Peak, indicating aerosol loading in the atmosphere. Our observations show north-westerly winds indicating the convective lifting of aerosols from far-off regions followed by horizontal long-range transport. The presence of strongly absorbing and scattering aerosols in the elevated layer resulted in a relatively large diurnal mean aerosol surface radiative forcing efficiency (forcing per unit optical depth) of about −65 and −63 W m−2 and the corresponding mean reduction in the observed net solar flux at the surface (cooling effect) is as high as −22 and −30 W m−2. The reduction of radiation will heat the lower atmosphere by redistributing the radiation with heating rate of 1.13 and 1.31 K day−1 for April and May 2008, respectively, in the lower atmosphere.

Altitude variation of aerosol properties over the Himalayan range inferred from spatial measurements

Altitude variations of the mass concentration of black carbon, number concentration of composite aerosols are examined along with the columnar spectral aerosol optical depths using state of the art instruments and the Ångström parameters are inferred from the ground based measurements at several altitude levels, en route from Manora Peak, Nainital (∼1950 m above mean sea level) to a low altitude station Haldwani (∼330 m above mean sea level) at its foothill within an aerial distance of <10,000 m. The measurements were done during the winter months (November–February) of 2005, 2006 and 2007 under fair weather conditions. The results show a rapid decrease in all the measured parameters with increase in altitude, with >60% contribution to the AOD coming from the regions below ∼1000 m. The Ångström wavelength exponent remained high in the well mixed region, and decreased above. The normalized AOD gradient was used to estimate aerosol mixing height, which was found to be in the altitude range 1000–1500 m, above which the particle concentrations are slowly varying as a function of altitude. The heating rate at the surface is found to be maximum but decreases sharply with increase in altitude. Analysis of the wavelength dependence of absorption aerosol optical depth (AAOD) showed that the aerosol absorption over the site is generally due to mixed aerosols.

Study of atmospheric aerosols over the central Himalayan region using a newly developed Mie light detection and ranging system: preliminary results

A LIDAR system to receive Mie backscattered photons has been developed at the Manora peak, Nainital, India and it is the first of its kind in the central Himalayan region. The system is sensitive to receive backscattered photons from heights up to ∼20 km (above ground level). The atmospheric extinction profiles using Mie LIDAR have been estimated for the first timeatthissiteinJanuary(winter)andMarch(spring)seasonsinthreecampaignsandmaximum valuesarefoundtobe ∼0.01,0.03,and0.08km −1 ,respectively.Theaerosolopticaldepth(AOD) values are found to be ∼0.051, 0.098, and 0.233 in three campaigns, respectively, showing enhancement from January (winter) to March (spring) indicating a seasonal variation. AOD values of LIDAR, aerosol robotic network, and moderate resolution imaging spectroradiometer were found within the standard deviations. The aerosol loading at the site has increased during the last decade as evident from previous studies. C 2011 Society of Photo-Optical Instrumentation

Long-term record of aerosol optical properties and chemical composition from a high-altitude site (Manora Peak) in Central Himalaya

Abstract. A long-term study, conducted from February 2005 to July 2008, involving chemical composition and optical properties of ambient aerosols from a high-altitude site (Manora Peak: 29.4° N, 79.5° E, ~1950 m a.s.l.) in the central Himalaya is reported here. The total suspended particulate (TSP) mass concentration varied from 13 to 272 μg m−3 over a span of 42 months. Aerosol optical depth (AOD) and TSP increase significantly during the summer (April–June) due to increase in the concentration of mineral dust associated with the long-range transport from desert regions (from the middle-East and Thar Desert in western India). The seasonal variability in the carbonaceous species (EC, OC) is also significantly pronounced, with lower concentrations during the summer and monsoon (July–August) and relatively high during the post-monsoon (September–November) and winter (December–March). On average, total carbonaceous aerosols (TCA) and water-soluble inorganic species (WSIS) contribute nearly 25 and 10% of the TSP mass, respectively. The WSOC/OC ratios range from 0.36 to 0.83 (average: 0.55 ± 0.15), compared to lower ratios in the Indo-Gangetic Plain (range: 0.35–0.40), and provide evidence for the enhanced contribution from secondary organic aerosols. The mass fraction of absorbing EC ranged from less than a percent (during the summer) to as high as 7.6% (during the winter) and absorption coefficient (babs, at 678 nm) varied between 0.9 to 33.9 Mm−1 (1 Mm−1=10−6 m−1). A significant linear relationship between babs and EC (μgC m−3) yields a slope of 12.2 (± 2.3) m2 g−1, which is used as a measure of the mass absorption efficiency (σabs) of EC.

Characteristics of aerosol black carbon mass concentration over a high altitude location in the Central Himalayas from multi-year measurements

Multi-year measurements of near surface aerosol black carbon (BC) mass concentration, made from a high altitude station at Manora Peak (29.4° N, 79.5° E, 1958 m msl) in the Central Himalayas, using a 7-channel Aethalometer for 38 months from November 2004 to December 2007, are examined. Temporally, BC exhibited well-defined diurnal variations, comprising of a single prominent peak occurring in the late afternoon (before sunset) hours during the months from October to March, while these variations were insignificant during April to September. These were found to be closely associated with the dynamics of atmospheric boundary layer (ABL), and pose a form that is distinctly different from those reported for the plains. BC mass concentrations were always higher by a factor of about 2 during daytime than the concentrations during nighttime. Seasonally, BC mass concentrations were higher during spring (with a mean value of 1.34 ± 0.05 µg m − 3 ), which are attributed to lifting up of pollutants from the valley (below the mountain peak) by the convective boundary layer and increased local emissions. The concentration decreased by a factor of 2 in summer (0.53 ± 0.02) and recovered during autumn (1.03 ± 0.04). The long-term average value was 0.99 ± 0.02 µg m − 3 . Examination of the wavelength dependence revealed that BC observed at this location is generally dominated by fossil fuel combustion.

Absorption Coefficient and Site-Specific Mass Absorption Efficiency of Elemental Carbon in Aerosols over Urban, Rural, and High-Altitude Sites in India

Temporal and spatial variability in the absorption coefficient (b(abs), Mm(-1)) and mass absorption efficiency (MAE, sigma(abs), m(2)g(-1)) of elemental carbon (EC) in atmospheric aerosols studied from urban, rural, and high-altitude sites is reported here. Ambient aerosols, collected on tissuquartz filters, are analyzed for EC mass concentration using thermo-optical EC-OC analyzer, wherein simultaneously measured optical-attenuation (ATN, equivalent to initial transmittance) of 678 nm laser source has been used for the determination of MAE and absorption coefficient. At high-altitude sites, measured ATN and surface EC loading (EC(s), microg cm(-2)) on the filters exhibit linear positive relationship (R(2) = 0.86-0.96), suggesting EC as a principal absorbing component. However, relatively large scatter in regression analyses for the data from urban sites suggests contribution from other species. The representative MAE of EC, during wintertime (Dec 2004), at a rural site (Jaduguda) is 6.1 +/- 2.0 m(2)g(-1). In contrast, MAE at the two high-altitude sites is 14.5 +/- 1.1 (Manora Peak) and 10.4 +/- 1.4 (Mt. Abu); and that at urban sites is 11.1 +/- 2.6 (Allahabad) and 11.3 +/- 2.2 m(2)g(-1) (Hisar). The long-term average MAE at Manora Peak (February 2005 to June 2007) is 12.8 +/- 2.9 m(2)g(-1) (range: 6.1-19.1 m(2)g(-1)). These results are unlike the constant conversion factor used for MAE in optical instruments for the determination of BC mass concentration. The absorption coefficient also shows large spatiotemporal variability; the lower values are typical of the high-altitude sites and higher values for the urban and rural atmosphere. Such large variability documented for the absorption parameters suggests the need for their suitable parametrization in the assessment of direct aerosol radiative forcing on a regional scale.

Investigation of star clusters found in the 2mass catalog

AbstractWe have launched a program of UBVR CCD photometric investigations of new clusters detected in the 2mass catalog based on an automatic detection method, which uses a convolution with a density function. Three new clusters, Koposov 12, Koposov 53 and Koposov 77 were observed in UBVI with the 104 cm Sampurnanand telescope located at ARIES, Manora Peak, India. Their ages, distances, color excesses and metallicities have been derived using photometric data.

An integrated analysis of lidar observations in association with optical properties of aerosols from a high altitude location in central Himalayas

AbstractIn order to study the aerosol backscatter profiles, a portable micro pulse lidar (MPL) system was installed in the year 2006 at Manora Peak, (29°22′N, 79°27′E, ∼1960 m amsl) Nainital, a high altitude location in the central Himalayas. In the present study the results of observed lidar profiles, columnar aerosol optical depths (AOD) and prevailing meteorology during May 2006 to June 2007 are presented. Although the lidar was operated from a sparsely inhabited free tropospheric site, nevertheless the height distribution of aerosol layers are found to be extended up to the summit of ∼2 km above the ground level (AGL). The backscatter ratio (BSR) varies from ∼10 to ∼20 having lowest values during post‐monsoon and highest during pre‐monsoon period. The observed boundary layer height during the post monsoon was shallower to the pre‐monsoon period. Occasionally the lidar profiles reveal the presence of cirrus clouds at an altitude of 8–10 km AGL. The extended lidar observations over Manora Peak not only provided the profiles of aerosol extinction coefficient but also significantly substantiate the elevated aerosol layers and clouds, which are important in the study of climate modelling. Copyright © 2009 Royal Meteorological Society

Retrieval of Columnar Aerosol Size Distributions from Spectral Attenuation Measurements over Central Himalayas

Extensive measurements of spectral aerosol optical depths (AODs) were made at Manora Peak, Nainital (29.4o N, 79.5o E, ~1958 m above mean sea level) in the central Himalayas, using a ten channel multi-wavelength solar radiometer during January 2002 to December 2005. Using these spectral AOD values, the columnar size distribution [CSD; nc(r)] function of aerosols have been derived. The CSD, retrieved from spectral AODs are, in general, bimodal (combination of power law and unimodal log normal distribution) with a prominent secondary (or coarse) mode occurring at a fairly large value of radius (r > 0.5 µm), while the primary (or fine) mode either does not appear explicitly or perhaps occurs below the radius  0.1 µm. The bimodal nature of CSDs indicates the presence of fine as well as coarse mode aerosols over the observational site. The effective radius, total aerosol number content and columnar mass loading computed from deduced CSD shows minimum values during winter (November to February) and maximum during summer (March to June) months. The share of sub micron and super micron aerosols to the total aerosol number concentration (Nt) indicates the dominance of sub micron aerosols to the Nt and it accounts for > 90% during the study period.

Retrieval of Columnar Aerosol Size Distributions from Spectral Attenuation Measurements over Central Himalayas

Extensive measurements of spectral aerosol optical depths (AODs) were made at Manora Peak, Nainital (29.4°N, 79.5°E,~1958 m above mean sea level) in the central Himalayas, using a ten channel multi-wavelength solar radiometer during January 2002 to December 2005. Using these spectral AOD values, the columnar size distribution [CSD; n(subscript c)(r)] function of aerosols have been derived. The CSD, retrieved from spectral AODs are, in general, bimodal (combination of power law and unimodal log normal distribution) with a prominent secondary (or coarse) mode occurring at a fairly large value of radius (r＞0.5 μm), while the primary (or fine) mode either does not appear explicitly or perhaps occurs below the radius ≌0.1 μm. The bimodal nature of CSDs indicates the presence of fine as well as coarse mode aerosols over the observational site. The effective radius, total aerosol number content and columnar mass loading computed from deduced CSD shows minimum values during winter (November to February) and maximum during summer (March to June) months. The share of sub micron and super micron aerosols to the total aerosol number concentration (N(subscript t)) indicates the dominance of sub micron aerosols to the N(subscript t) and it accounts for ＞90% during the study period.

Atmospheric abundances of primary and secondary carbonaceous species at two high-altitude sites in India: Sources and temporal variability

Based on the time-series analyses of bulk-aerosol samples, we report on the large-scale temporal variability in the atmospheric abundances of elemental carbon (EC) and organic carbon (OC) at two high-altitude sites, Manora Peak (1950 m asl in north India) and Mt. Abu (1680 m asl in western India). The total suspended particulate (TSP) mass concentration in the ambient atmosphere also exhibits large seasonal variability at both the sites; varying from 13.4 to 432.3 μg m −3 at Mt. Abu and 12.7 to 271.7 μg m −3 at Manora Peak. The relatively high abundance of TSP, occurring during Apr–Jun, is associated with enhanced contribution from mineral dust. Both, OC and EC abundances at Manora Peak are nearly 2–3 times higher than those at Mt. Abu; the minimum concentrations occurring during the high-dust season (Apr–Jun) and monsoon season (Jul–Aug) and maximum in winter months (Dec–Mar). At Mt. Abu, annual-average abundances of OC (range: 0.9–12.3 μg m −3; Av = 3.7 μg m −3) and EC (range: 0.06–2.3 μg m −3; Av = 0.5 μg m −3) account for about 10 and 2% of the TSP, respectively. In contrast, annual-average concentrations of OC and EC at Manora Peak are 8.7 μg m −3 (range: 2.0–22.3 μg m −3) and 1.1 μg m −3 (range: 0.14–2.7 μg m −3), respectively; and account for about 14 and 2% of the TSP. The OC/EC ratios at the two sites (Manora Peak, range: 4.8–14.9 and Mt. Abu, range: 3.0–11.5) are significantly higher compared to those reported in the literature (2.0–3.0) for the urban regions. The high OC/EC ratios and low EC concentrations are attributed to relative dominance of organic carbon derived from biomass burning (crop waste). The average contribution of total carbonaceous aerosols (TCA; TCA = 1.6 × OC + EC) to TSP is ∼24% at Manora Peak and that at Mt. Abu is only 15%. The relatively high contribution of TCA, at Manora Peak, is influenced by the regional emission sources in north India. The contribution of secondary organic carbon (SOC) to OC, calculated based on minimum OC/EC ratio method, averages around 27% at Manora Peak and ∼16% at Mt. Abu; and brings to focus its significant role on a regional scale. The low EC concentration together with significant contribution of OC and SOC to TCA and their temporal variability suggests reassessment of relative amounts of absorbing (BC) and scattering (OC) species used in the radiative forcing models on a regional scale.

Physical and optical characteristics of atmospheric aerosols during ICARB at Manora Peak, Nainital: A sparsely inhabited, high-altitude location in the Himalayas

Collocated measurements of the optical and physical properties of columnar and near-surface aerosols were carried out from Manora Peak, Nainital (a sparsely inhabited, high altitude location, ∼2 km above mean sea level, in the Himalayas), during the Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB) under the Geosphere Biosphere Programme of the Indian Space Research Organization (ISRO-GBP). Under this, observational data of spectral aerosol optical depths (AOD), mass concentration of aerosol black carbon (MB), mass concentration (MT) and number concentration (Nt) of composite (total) aerosols near the surface and meteorological parameters were collected during the period February 15 to April 30, 2006. Though very low (<0.1 at 500 nm) AODs were observed during clear days, as much as a four-fold increase was seen on hazy days. The Angstrom exponent (α), deduced from the spectral AODs, revealed high values during clear days, while on hazy days α was low; with an overall mean value of 0.69 ± 0.06 for the campaign period. BC mass concentration varied between 0.36 and 2.87 μg m−3 and contributed in the range 0.7 to 1.8% to the total aerosol mass. Total aerosol number concentration and BC mass concentration showed diurnal variation with a midnight and early morning minimum and a late afternoon maximum; a pattern quite opposite to that seen in low altitude stations. These are attributed to the dynamics of the atmospheric boundary layer.

Short-Period Modulations in Aerosol Optical Depths over the Central Himalayas: Role of Mesoscale Processes

Abstract Multiyear measurements of spectral aerosol optical depths (AODs) were made at Manora Peak in the central Himalaya Range (29°22′N, 79°27′E, ∼1950 m above mean sea level), using a 10-channel multiwavelength solar radiometer for 605 days during January 2002–December 2004. The AODs at 0.5 μm were very low (≤0.1) in winter and increased steeply to reach high values (∼0.5) in summer. It was observed that monthly mean AODs vary significantly (by more than a factor of 6) from January to June. Strong short-period fluctuations (within a daytime) were observed in the AODs. Further investigations of this aspect have revealed that boundary layer dynamics plays a key role in transporting aerosols from the polluted valley region to higher altitudes, causing large contrast in AODs between forenoon and afternoon. The seasonal variations in AODs, while examined in conjunction with synoptic-scale wind fields, have revealed that the transport of dust aerosols from arid regions to the valley regions adjacent to the observational site and their subsequent transport upward by boundary layer dynamics are responsible for the summer increases.

Comment on “Surface changes in solar irradiance due to aerosols over central Himalayas” by U. C. Dumka et al.

Comment on “Surface changes in solar irradiance due to aerosols over central Himalayas” by U. C. Dumka et al.