High-altitude Station Research Articles

Black carbon in cloud-water and rain water during monsoon season at a high altitude station in India

We present results of measurements of black carbon (BC) from ground-based wet-only rainwater (RW) and cloud-water (CW) sampling at a mountain field station, Sinhagad, situated in south western Indi ...

Boundary Layer Characteristics over a High Altitude Station, Mauna Loa Observatory

The unique boundary layer at Mauna Loa Observatory (3396 meters) is examined with a combination of radiosondes launched from the observatory and a novel aerosol profiling technique called CLidar or camera lidar. This boundary layer is influenced by a combination of radiation winds, due to the heating and cooling of the surrounding lava, and off-island winds. Typically an upslope surface wind forms after sunrise as the ground heats up. The reverse occurs after sunset as the ground cools and a temperature inversion, tens of meters thick forms. Aerosol increases for the first 90 to 160 meters and then decreases to free tropospheric levels. The 90 to 160 m aerosol peak indicates the vicinity of the upslope/downslope interface in the air flow. An upper transition is seen in the aerosol gradient at about 600 meters above the observatory (4000 m Above Sea Level). This transition is also seen in radiosonde potential temperature data. The sondes indicate that the air above the nighttime downslope surface region usually has an upslope component. Some of this counter-flowing air can be entrained in the downslope air, possibly influencing the sampling of aerosols and trace gases at the observatory.

Evaluation of Atmospheric PCDD/Fs at Two High-Altitude Stations in Vietnam and Taiwan during Southeast Asia Biomass Burning

Dioxin and dioxin-like compounds such as polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) are persistent organic pollutants (POPs) generated through human activities. In recent times, extreme weather events such as wild fires have significantly affected the remobilization and successive bioavailability of PCDD/Fs. In Seven South East Asian Studies (7-SEAS), a Southeast Asia biomass burning event that influenced the environmental outcome and transport of PCDD/Fs in Taiwan was investigated on the basis of a climate change situation. During the 7-SEAS campaign on 20-28 March, 2011, significantly high levels of atmospheric PCDD/Fs were observed at Lulin mountain in central Taiwan and in the source region of Northern Vietnam (Son La). Measurements indicated that the patterns of variation of atmospheric PCDD/Fs at both locations were similar, but with a time lag of approximately 2 to 3 days. At Mt. Lulin, there was a significant increase of PCDD/F concentrations from 3.69 to 11.1 fg I-TEQ m^(-3) and 3.32 to 19.1 fg I-TEQ m^(-3) to reach their peaks on 23 March and 26 March. In this study, a tracer simulation using the Weather Research and Forecasting model coupled with chemistry was conducted to investigate the effects of the Southeast Asia biomass burning. The combined results of air mass paths simulation and satellite data can be used as evidence supporting the hypothesis that the source of the increasing PCDD/F level is originated from biomass-burning regions in Indochina, particularly Northern Vietnam and Northern Thailand.

The Zugspitze Raman Lidar: System Testing

A high-power Raman lidar system has been installed at the high-altitude research station Schneefernerhaus (Garmisch-Partenkirchen, Germany) at 2675 m a.s.l., at the side of the existing wide-range differrential-absorption lidar. An industrial XeCl laser was modified for polarized single-line operation at an average power of about 175 W. This high power and a 1.5-m-diameter receiver are expected to allow us to extend the operating range for water-vapour sounding to more than 25 km, at an accuracy level of the order of 10 %. In addition, temperature measurements in the free troposphere and to altitudes beyond 80 km are planned. The system is currently thoroughly tested and exhibits an excellent performance up to the lowermost stratosphere. We expect that results for higher altitudes can be presented at the meeting.

Atmospheric Particle Size Distributions in the Spanish Network of Environmental DMAs (REDMAAS)

The present work is a first approach to the study of the spatio-temporal variability of the submicrometer atmospheric aerosol in Spain. The aerosol measurements have been obtained simultaneously at seven monitoring stations that compose the REDMAAS network during two measurement campaigns corresponding to summer and winter seasons.In both summer and winter periods those measurement stations with a direct influence of anthropogenic emissions recorded the highest concentrations of particle number. In the summer campaign, the average daily pattern of the aerosol size distribution in the traffic and background urban stations was conditioned by the traffic emissions and secondary aerosol formation through photochemical reactions (new particle formation events, NPF). However, the secondary aerosol had a higher contribution to the aerosol total number concentration in the rural background and high-altitude stations. In the winter campaign, in all sampling sites with the exception of Izaña station, the traffic and domestic activity emissions had a greater contribution than secondary aerosol formation on particle number total concentration.New particle formation events were identified at all sites during the summer period, and at sites without direct influence of anthropogenic emissions during the winter campaign. Some aerosol shrinkage processes were also observed at the Madrid and El Arenosillo stations.

Long and short-term atmospheric radiation analyses based on coupled measurements at high altitude remote stations and extensive air shower modeling

In this paper are described the ACROPOL and OPD high-altitude stations devoted to characterize the atmospheric radiation fields. The ACROPOL platform, located at the summit of the Pic du Midi in the French Pyrenees at 2885 m above sea level, exploits since May 2011 some scientific equipment, including a BSS neutron spectrometer, detectors based on semiconductor and scintillators. In the framework of a IEAv and ONERA collaboration, a second neutron spectrometer was simultaneously exploited since February 2015 at the summit of the Pico dos Dias in Brazil at 1864 m above the sea level.The both high station platforms allow for investigating the long period dynamics to analyze the spectral variation of cosmic-ray- induced neutron and effects of local and seasonal changes, but also the short term dynamics during solar flare events.This paper presents long and short-term analyses, including measurement and modeling investigations considering the both high altitude stations data. The modeling approach, based on ATMORAD computational platform, was used to link the both station measurements.

Assessment of aerosol optical and micro-physical features retrieved from direct and diffuse solar irradiance measurements from Skyradiometer at a high altitude station at Merak: Assessment of aerosol optical features from Merak.

Optical and micro-physical features of aerosol are reported using Skyradiometer (POM-01L, Prede, Japan) observations taken from a high-altitude station Merak, located in north-eastern Ladakh of the western trans-Himalayas region during January 2011 to December 2013. The observed daily mean aerosol optical depth (AOD, at 500 nm) at the site varied from 0.01 to 0.14. However, 75 % of the observed AOD lies below 0.05 during the study period. Seasonal peaks of AOD occurred in spring as 0.06 and minimum in winter as 0.03 which represents the aged background aerosols at the site. Yearly mean AOD at 500 nm is found to be around 0.04 and inter-annual variations of AOD is very small (nearly ±0.01). Angstrom exponent (a) varied seasonally from 0.73 in spring to 1.5 in autumn. About 30 % of the observed a lies below 0.8 which are the indicative for the presence of coarse-mode aerosols at the site. The station exhibits absorbing aerosol features which prominently occurred during spring and that may be attributed by the transported anthropogenic aerosol from Indo-Gangatic Plain (IGP). Results were well substantiated with the air mass back-trajectory analysis. Furthermore, seasonal mean of single scattering albedo (SSA at 500 nm) varied from of 0.94 to 0.98 and a general increasing trend is noticed from 400 to 870 nm wavelengths. These features are apparently regional characteristics of the site. Aerosol asymmetry factor (AS) decreases gradually from 400 to 870 nm and varied from 0.66 to 0.69 at 500 nm across the seasons. Dominance of desert-dust aerosols, associated by coarse mode, is indicated by tri-modal features of aerosol volume size distribution over the station during the entire seasons.

Handover Performance of Unstable-Yaw Stratospheric High-Altitude Stations

Stratospheric platform (SP) is a new technique for providing mobile and data communications and is capable to add many advantages to the users compared to conventional terrestrial and satellite systems. A very competing problem of this emerging system is the positional instability of SP which affects the system performance. In this paper, one main problem of SP positional instabilities--which is the rotation drift--is described and analyzed and its impact on the call handover in cellular systems is also investigated. The total handover due to both user mobility and platform positional instability is explained and determined. In addition, an expression for the number of handed calls is deduced which has been shown as function of user density, distribution, platform angular shift due to rotation, cell geometry, and number of active calling users. The analysis of this number shows the serious effects of the rotational motion instability on the system performance.

Mapping of maximum snow load values for the 50-year return period for Croatia

Snow load is an important climatic element that is, together with minimum and maximum temperatures and wind load, a part of the national annex of standards for the design of structures. In particular, the characteristic snow load, defined as the maximum snow load at the ground for the 50-year return period, has to be estimated and a map has to be supplied as part of the national annex. The method for the estimation of this parameter at the station locations is presented, followed by the geostatistical mapping procedure used to estimate this parameter for the whole territory of Croatia. Snow load is defined as a product of snow density, snow depth and gravitational acceleration. Although snow depths are measured at a large number of meteorological stations, snow loads are not easy to estimate because of very few snow density measurements. To overcome this, snow density was fitted to snow depth data using linear regression according to the daily pairs of values from 13 meteorological stations. Since snow density changes with elevations and seasons, the stations are divided into three subsets according to station elevation (lower than 600 m, 600–1000 m high and higher than 1000 m) and the regression equations are also built on a monthly basis. These modelling results allowed the estimation of the snow load at 96 low-elevation stations, eight higher elevation stations and one high-altitude station based on the monthly maximum snow depths and the model estimated snow densities. Based on the monthly maximum snow loads, the series of maximum annual snow loads can be calculated for 118 locations. These series of annual maximum snow loads are the basis for the estimation of the annual maximum snow load values for the 50-year return period, by means of an extreme value distribution.Finally, the estimated annual maximum snow load values for the 50-year return period at 118 stations constitute the input for the geostatistical procedure of mapping this parameter for the territory of Croatia.

Inspection of high–concentration CO2 events at the Plateau Rosa Alpine station

The Plateau Rosa Alpine station (Italy) has collected atmospheric concentrations of carbon dioxide since 1989. If the complete set of hourly data is observed, two distinct and exceptional very high concentration events are evident for February 2004. Similar and almost contemporary peaks were registered at the European high–altitude stations of Zugspitze–Schneefernerhaus and Sonnblick in the Alps, and at Mt. Cimone in the Northern Apennines. A regional meteorological model (the Weather Research and Forecast) was applied over a medium–high resolution grid to study the evolution of the meteorological fields and to identify the trajectories of the polluted air masses during the CO2 observed peaks. The results show that, during both episodes, atmospheric circulation conveyed highly polluted air from the European plains to the Alpine stations. This conclusion has been also confirmed through concentration measurements of the atmospheric trace gases in the same area.

Major contribution of neutral clusters to new particle formation at the interface between the boundary layer and the free troposphere

Abstract. The formation of new aerosol particles in the atmosphere is a key process influencing the aerosol number concentration as well as the climate, in particular at high altitude, where the newly formed particles directly influence cloud formation. However, free tropospheric new particle formation (NPF) is poorly documented due to logistic limitations and complex atmospheric dynamics around high-altitude stations that make the observation of this day-time process challenging. Recent improvements in measurement techniques make now possible the detection of neutral clusters down to ~ 1 nm sizes, which opens new horizons in our understanding of the nucleation process. Indeed, only the charged fraction of clusters has been reported in the upper troposphere up to now. Here we report day-time concentrations of charged and neutral clusters (1 to 2.5 nm mobility diameter) recorded at the interface between the boundary layer (BL) and the FT as well as in the FT at the altitude site of Puy de Dôme (1465 m a.s.l.), central France, between 10 and 29 February 2012. Our findings demonstrate that in the FT, and especially at the interface between the BL and the FT, the formation of 1.5 nm neutral clusters significantly exceeds the one of ionic clusters during NPF events, clearly indicating that they dominate in the nucleation process. We also observe that the total cluster concentration significantly increases during NPF events compared to the other days, which was not clearly observed for the charged cluster population in the past. During the studied period, the nucleation process does not seem to be sulfuric acid-limited and could be promoted by the transport of pollutants to the upper troposphere, coupled with low temperatures.

Retrieval of ethane from ground-based FTIR solar spectra using improved spectroscopy: Recent burden increase above Jungfraujoch

An improved spectroscopy is used to implement and optimize the retrieval strategy of ethane (C2H6) from ground-based Fourier Transform Infrared (FTIR) solar spectra recorded at the high-altitude station of Jungfraujoch (Swiss Alps, 46.5°N, 8.0°E, 3580m a.s.l.). The improved spectroscopic parameters include C2H6 pseudo-lines in the 2720–3100cm−1 range and updated line parameters for methyl chloride and ozone. These improved spectroscopic parameters allow for substantial reduction of the fitting residuals as well as enhanced information content. They also contribute to limiting oscillations responsible for ungeophysical negative mixing ratio profiles. This strategy has been successfully applied to the Jungfraujoch solar spectra available from 1994 onwards. The resulting time series is compared with C2H6 total columns simulated by the state-of-the-art chemical transport model GEOS-Chem. Despite very consistent seasonal cycles between both data sets, a negative systematic bias relative to the FTIR observations suggests that C2H6 emissions are underestimated in the current inventories implemented in GEOS-Chem. Finally, C2H6 trends are derived from the FTIR time series, revealing a statistically-significant sharp increase of the C2H6 burden in the remote atmosphere above Jungfraujoch since 2009. Evaluating cause of this change in the C2H6 burden, which may be related to the recent massive growth of shale gas exploitation in North America, is of primary importance for atmospheric composition and air quality in the Northern Hemisphere.

Early history of high-altitude physiology.

High-altitude physiology can be said to have begun in 1644 when Torricelli described the first mercury barometer and wrote the immortal words "We live submerged at the bottom of an ocean of the element air." Interestingly, the notion of atmospheric pressure had eluded his teacher, the great Galileo. Blaise Pascal was responsible for describing the fall in pressure with increasing altitude, and Otto von Guericke gave a dramatic demonstration of the enormous force that could be developed by atmospheric pressure. Robert Boyle learned of Guericke's experiment and, with Robert Hooke, constructed the first air pump that allowed small animals to be exposed to a low pressure. Hooke also constructed a small low-pressure chamber and exposed himself to a simulated altitude of about 2400 meters. With the advent of ballooning, humans were rapidly exposed to very low pressures, sometimes with tragic results. For example, the French balloon, Zénith, rose to over 8000 m, and two of the three aeronauts succumbed to the hypoxia. Paul Bert was the first person to clearly state that the deleterious effects of high altitude were caused by the low partial pressure of oxygen (PO2), and later research was accelerated by high-altitude stations and expeditions to high altitude.

Wintertime Subkilometer Numerical Forecasts of Near-Surface Variables in the Canadian Rocky Mountains

Abstract Numerical weather prediction (NWP) systems operational at many national centers are nowadays used at the kilometer scale. The next generation of NWP models will provide forecasts at the subkilometer scale. Large impacts are expected in mountainous terrain characterized by highly variable orography. This study investigates the ability of the Canadian NWP system to provide an accurate forecast of near-surface variables at the subkilometer scale in the Canadian Rocky Mountains in wintertime when the region is fully covered by snow. Observations collected at valley and high-altitude stations are used to evaluate forecast accuracy at three different grid spacing (2.5, 1, and 0.25 km) over a period of 15 days. Decreasing grid spacing was found to improve temperature forecasts at high-altitude stations because of better orography representation. In contrast, no improvement is obtained at valley stations due to an inability of the model to fully capture at all resolutions the intensity of valley cold pools forming during nighttime. Errors in relative humidity reveal that the model tends to overestimate relative humidity at all resolutions, without improvement with decreasing grid spacing. Wind speed forecasts show large improvements with decreasing grid spacing for high-altitude stations exposed to or sheltered from wind. However, no systematic improvement with decreasing grid spacing is found for all stations, which is similar to previous studies. In addition, the model’s sensitivity at subkilometer grid spacing is investigated by evaluating the effects of (i) accounting for additional drag generated by subgrid orographic features, (ii) considering slope angle and aspect on surface radiation, and (iii) using high-resolution initialization for the surface fields.

Characterization of Black Carbon Aerosols over Darjeeling - A High Altitude Himalayan Station in Eastern India

A continuous monitoring of black carbon (BC) aerosols was carried over a high altitude station Darjeeling (27°01′N, 88°15′E; 2200 m a.s.l.) at eastern part of Himalaya in India during January 2010–December 2011. In this article, we have presented the results of our analysis of the data collected during this interval. This study is focused on the investigation of the temporal variations, potential sources, long-range transport of BC aerosols along with the meteorological impact on these aerosols. BC is found to exhibit strong seasonal variation with the maximum concentration during premonsoon (5.0 ± 1.1 µg/m3) followed by winter (3.9 ± 2.2 µg/m3), postmonsoon (2.9 ± 1.0 µg/m3) and minimum during monsoon (1.7 ± 0.7 µg/m3). BC concentration varied between 0.2–12.8 µg/m3 with an average of 3.4 ± 1.9 µg/m3 over the entire period of study. The diurnal variation of BC aerosol shows sharp morning and evening peaks associated to the local anthropogenic activities as well as the impact of up-slope mountain wind. Amongst the long distant sources, BC concentration associated with the transport from Middle East countries and passing over South West countries like Pakistan, Afghanistan and Indo-Gangetic Plain is found to be comparatively higher. It is observed that the contributions of local emissions, long-range transport and mountain wind transport are approximately 56%, 27% and 17%, respectively, towards the total BC loading over Darjeeling during premonsoon. Fossil fuel emissions during premonsoon and biomass burning during winter are the major sources of BC with the overall dominance of fossil fuel burning throughout the entire study period. The BC concentration over Darjeeling is found to be much higher than any other high altitude stations in India and Nepal and even higher and comparable with some of the metro-cities in India.

Temporal asymmetry in aerosol optical characteristics: A case study at a high-altitude station, Hanle, in Ladakh region

Diurnal features of aerosol optical depth (AOD) at a high-altitude station, Hanle (4500m amsl) in the western Himalayas, were studied using direct/diffuse solar irradiance measurement from a Skyradiometer (Prede) during October 2007 to December 2010. The study reveals a diurnal asymmetry in the measured aerosol characteristics, with three types of diurnal variation in AOD. Among them, Types I and II are prominent during pre-monsoon, while Type III dominates during post-monsoon. Type I appears to be associated with new-particle formation process from gaseous precursors, in addition to the combination of anthropogenic and desert-dust aerosols, probably brought by the prevailing westerly/south-westerly winds during the pre-monsoon season. The diurnal feature of the Type II may be attributed by the transported desert-dust aerosols brought by the prevailing winds. Further, Type III may be associated with the aged background aerosols over the region, pertaining to a small contribution from gaseous precursors.

Temperature trend–altitude relationship in China during 1963–2012

Based on daily air temperature data from 745 stations in China, the present study investigates the regional characteristics of temperature trend and the dependence of temperature changes on the altitude during the period of 1963–2012. There is a consistent warming trend throughout the country except for the southwest China where a cooling trend is identified. Moreover, significant warming trend exists in highland areas such as the Northeast, Inner Mongol, and the Tibet region. Compared with other seasons, the warming trend is most pronounced in highland regions in winter. In summer, the temperature has no obvious increasing trend in north China, while the cooling trend is found in south China. The relationship between altitude and temperature trend is further investigated by dividing China into three subregions according to the altitude—below 200, 200–2,000, and above 2,000 m. Although there is no simple linear relationship between elevation and warming trend on national scale, the temperature trend–altitude relation is different among the three regions. The temperature trend decreases with altitude below 200 m while increases from 200 to 2,000 m, and a weak positive temperature trend–altitude relation is found over 2,000 m. The strongest temperature trend–altitude relations are found in the subtropical regions, especially pronounced south of 36°N in China. The magnitudes of decreases from 200 to 2,000 m are one order lower than the increases below 200 m. Low-altitude stations appear to be influenced more by anthropogenic aerosols. High-altitude stations are mostly located in flat terrain and sparsely populated region. Therefore, temperature trends change with elevations.

Can monsoon moisture arrive in the Qilian Mountains in summer?

The isotopic composition of precipitation has been measured in samples simultaneously collected during individual precipitation events at a high-altitude station (Hulugou at 3260 m a.s.l.) in the middle Qilian Mountains, northwestern China. The observed changes of δ18O (δD) and deuterium excess with surface air temperature, precipitation and season have been evaluated to derive information on water vapor sources and the effects from monsoon moisture. The results indicated monsoonal moisture can arrive in the Qilian Mountains in summer, as indicated by: (1) under temperatures between 8 °C and 15 °C, the precipitation events are characterized by the decrease of δ18O and d excess owing to the influence from monsoonal moisture; (2) δ18O and δD showed statistically negative correlation with precipitation, which reflected the amount effect in at precipitation events scale; (3) not only the water vapor transporting vector but also composite circulation maps verified the arrival of monsoonal moisture in summer along the eastern margin of the Tibetan Plateau, which made a great contribution to regional precipitation under climate warming.

Aerosol radiative forcing over a high-altitude station Merak, in the trans-Himalayan region during advection of anthropogenic events from the Indo-Gangetic Plain

Advection of anthropogenic aerosols from the Indo-Gangetic Plain (IGP) and dust aerosols from distant deserts towards a high-altitude station Merak, in the trans-Himalayan region are reported during June–July 2011. In order to differentiate the advection event, aerosol optical properties were examined during aged background conditions at the site. During the aged background conditions, aerosol optical depth (AOD at 500 nm) and Angstrom exponent (α) at the station were ∼0.06 and 1.36, respectively which were increased to 0.13 and 1.62, respectively during the advection event. Further, a strong signature of fine-mode aerosol volume size distribution, dominated by absorbing aerosols, was observed during the advection event. The average atmospheric forcing during the aged background condition was found to be 0.57 Wm−2 (with corresponding heating rate of 0.05 Kday−1) and these results were enhanced to 2.58 Wm−2 (with corresponding heating rate of 0.22 Kday−1) during the advection event. The present study reveals that during the advection event, heating rate in the atmosphere was increased by about four times than the aged background condition. Such atmospheric warming in the region may influence the melting of the Himalayan glaciers and consequently it may effect the local atmospheric circulation.

Simple equations for temperature simulations on mid-latitude volcanic islands: a case study from Jeju (Republic of Korea)

Volcanic islands can be characterized by remarkable surface air temperature variability. The distribution of weather stations in these settings, however, is typically too sparse to reliably describe temperature patterns which can complicate regional-scale hydrologic analyses. Here, a simple method is presented to estimate near surface air temperatures for such a setting (Jeju Island, Republic of Korea). The method utilizes temperature lapse rates (TLR; the change in temperature with elevation) which are computed for Tmin, Tave, and Tmax for two distinct hemispheres: the more arid northern flanks and the more humid southern flanks of the central orographic divide. Computed TLRs vary greatly with season and location relative to the orographic divide and, unlike in continental mountainous settings, are generally highest for Tmin in winter. Cross-validation results indicate a good match between modeled and measured values particularly for high altitude stations that are characterized by highest precipitation rates. Because temporally changing TLRs perform better than the often applied theoretical constant environmental lapse rate of 6.5 °C/km, monthly mean TLRs compiled from temperature data from Jeju Island are presented here as proxies for surface air temperature simulation efforts in similar settings for which only limited climatic data are available.