Effects of solar radiation on local and German wheat seedlings in a Chilean high mountain station

Supraglacial ice cliffs exist on debris-covered glaciers worldwide, but despite their importance as melt hot spots, their life cycle is little understood. Early field observations had advanced a hypothesis of survival of north-facing and disappearance of south-facing cliffs, which is central for predicting the contribution of cliffs to total glacier mass losses. Their role as windows of energy transfer suggests they may explain the anomalously high mass losses of debris-covered glaciers in High Mountain Asia (HMA) despite the insulating debris, currently at the center of a debated controversy. We use a 3D model of cliff evolution coupled to very high-resolution topographic data to demonstrate that ice cliffs facing south (in the Northern Hemisphere) disappear within a few months due to enhanced solar radiation receipts and that aspect is the key control on cliffs evolution. We reproduce continuous flattening of south-facing cliffs, a result of their vertical gradient of incoming solar radiation and sky view factor. Our results establish that only north-facing cliffs are recurrent features and thus stable contributors to the melting of debris-covered glaciers. Satellite observations and mass balance modeling confirms that few south-facing cliffs of small size exist on the glaciers of Langtang, and their contribution to the glacier volume losses is very small (∼1%). This has major implications for the mass balance of HMA debris-covered glaciers as it provides the basis for new parameterizations of cliff evolution and distribution to constrain volume losses in a region where glaciers are highly relevant as water sources for millions of people.

Download Full-text

Influence of air mass origins on optical properties and PM concentrations measured at a high mountain station located in the southwestern Mediterranean

Atmospheric Research ◽

10.1016/j.atmosres.2017.07.013 ◽

2017 ◽

Vol 197 ◽

pp. 244-254 ◽

Cited By ~ 5

Author(s):

R. Castañer ◽

J.F. Nicolás ◽

J. Crespo ◽

E. Yubero ◽

N. Galindo ◽

...

Keyword(s):

Optical Properties ◽

High Mountain ◽

Air Mass ◽

Mountain Station

Download Full-text

Impacts of topographic shading on direct solar radiation for valley glaciers in complex topography

10.5194/tc-2018-64 ◽

2018 ◽

Cited By ~ 1

Author(s):

Matthew H. Olson ◽

Summer B. Rupper

Keyword(s):

Energy Balance ◽

Solar Radiation ◽

Surface Energy ◽

Surface Energy Balance ◽

Direct Solar Radiation ◽

High Mountain ◽

Clear Sky ◽

Glacier Ice ◽

North And South ◽

Predictable Characteristics

Abstract. Topographic shading, including both shaded relief and cast shadowing, plays a fundamental role in determining direct solar radiation on glacier ice. However, this parameter has been oversimplified or incorrectly incorporated in surface energy balance models in some past studies. Here we develop a topographic solar radiation model to examine the variability in irradiance throughout the glacier melt season due to topographic shading and combined slope and aspect. We apply the model to multiple glaciers in High Mountain Asia (HMA), and test the sensitivity of shading to valley-aspect and latitude. Our results show that topographic shading significantly alters the potential direct clear-sky solar radiation received at the surface for valley glaciers in HMA, particularly for north- and south-facing glaciers. Additionally, we find that shading can be extremely impactful in the ablation zone. Cast shadowing is the dominant mechanism in determining total shading for valley glaciers in parts of HMA, especially at lower elevations. Although shading has some predictable characteristics, it is overall extremely variable between glacial valleys. Our results suggest that topographic shading is not only an important factor contributing to surface energy balance, but could also influence glacier response and mass balance estimates throughout HMA.

Download Full-text

Reconstruction of global solar radiation time series from 1933 to 2013 at the Izaña Atmospheric Observatory

Atmospheric Measurement Techniques ◽

10.5194/amt-7-3139-2014 ◽

2014 ◽

Vol 7 (9) ◽

pp. 3139-3150 ◽

Cited By ~ 13

Author(s):

R. D. García ◽

E. Cuevas ◽

O. E. García ◽

V. E. Cachorro ◽

P. Pallé ◽

...

Keyword(s):

Time Series ◽

Solar Radiation ◽

North Atlantic ◽

Sunshine Duration ◽

Global Solar Radiation ◽

Global Scale ◽

High Mountain ◽

Atlantic Region ◽

Clear Sky ◽

Radiation Time

Abstract. This paper presents the reconstruction of the 80-year time series of daily global solar radiation (GSR) at the subtropical high-mountain Izaña Atmospheric Observatory (IZO) located in Tenerife (The Canary Islands, Spain). For this purpose, we combine GSR estimates from sunshine duration (SD) data using the Ångström–Prescott method over the 1933/1991 period, and GSR observations directly performed by pyranometers between 1992 and 2013. Since GSR measurements have been used as a reference, a strict quality control has been applied based on principles of physical limits and comparison with LibRadtran model. By comparing with high quality GSR measurements, the precision and consistency over time of GSR estimations from SD data have been successfully documented. We obtain an overall root mean square error (RMSE) of 9.2% and an agreement between the variances of GSR estimations and GSR measurements within 92%. Nonetheless, this agreement significantly increases when the GSR estimation is done considering different daily fractions of clear sky (FCS). In that case, RMSE is reduced by half, to about 4.5%, when considering percentages of FCS > 40% (~ 90% of days in the testing period). Furthermore, we prove that the GSR estimations can monitor the GSR anomalies in consistency with GSR measurements and, then, can be suitable for reconstructing solar radiation time series. The reconstructed IZO GSR time series between 1933 and 2013 confirms change points and periods of increases/decreases of solar radiation at Earth's surface observed at a global scale, such as the early brightening, dimming and brightening. This fact supports the consistency of the IZO GSR time series presented in this work, which may be a reference for solar radiation studies in the subtropical North Atlantic region.

Download Full-text

Interactive effects of vertical mixing, nutrients and ultraviolet radiation: in situ photosynthetic responses of phytoplankton from high mountain lakes of Southern Europe

Biogeosciences Discussions ◽

10.5194/bgd-9-9791-2012 ◽

2012 ◽

Vol 9 (7) ◽

pp. 9791-9827

Author(s):

E. W. Helbling ◽

P. Carrillo ◽

J. M. Medina-Sanchez ◽

C. Durán ◽

G. Herrera ◽

...

Keyword(s):

Global Change ◽

Solar Radiation ◽

Ultraviolet Radiation ◽

Vertical Mixing ◽

Mountain Lakes ◽

High Mountain ◽

High Mountain Lakes ◽

Phytoplankton Communities ◽

Photosynthetic Responses

Abstract. Global change, together with human activities had resulted in increasing amounts of organic material (including nutrients) received by water bodies. This input further attenuates the penetration of solar radiation leading to the view that opaque lakes are more "protected" from solar ultraviolet radiation (UVR) than clear ones. Vertical mixing, however, complicates this view as cells are exposed to fluctuating radiation regimes, which effects have in general been neglected. Even more, the combined impacts of mixing, together with those of UVR and nutrients input are virtually unknown. In this study, we carried out in situ experiments in three high mountain lakes of Spain (Lake Enol in Asturias, and lakes Las Yeguas and La Caldera in Granada) to determine the combined effects of these three variables associated to global change on photosynthetic responses of natural phytoplankton communities. The experimentation consisted in all possible combinations of the following treatments: (a) solar radiation: UVR + PAR (280–700 nm) versus PAR alone (400–700 nm); (b) nutrient addition (phosphorus (P) and nitrogen (N)): ambient versus addition (P to reach to a final concentration of 30 μg P l−1, and N to reach a N : P molar ratio of 31) and, (c) mixing: mixed (one rotation from surface to 3 m depth (speed of 1 m every 4 min, total of 10 cycles) versus static. Our findings suggest that under in situ nutrient conditions there is a synergistic effect between vertical mixing and UVR, increasing phytoplankton photosynthetic inhibition and EOC from opaque lakes as compared to algae that received constant mean irradiance within the epilimnion. The opposite occurs in clear lakes where antagonistic effects were determined, with mixing partially counteracting the negative effects of UVR. Nutrients input mimicking atmospheric pulses from Saharan dust, reversed this effect and clear lakes became more inhibited during mixing, while opaque lakes benefited from the fluctuating irradiance regime. These climate change-related nutrients input and increased mixing would not only affect photosynthesis and production of lakes, but might also further influence the microbial loop and trophic interactions via enhanced EOC under fluctuating UVR exposure.

Download Full-text

Re-construction of global solar radiation time series from 1933 to 2013 at the Izaña Atmospheric Observatory

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-7-4191-2014 ◽

2014 ◽

Vol 7 (4) ◽

pp. 4191-4227 ◽

Cited By ~ 2

Author(s):

R. D. García ◽

E. Cuevas ◽

O. E. García ◽

V. E. Cachorro ◽

P. Pallé ◽

...

Keyword(s):

Time Series ◽

Solar Radiation ◽

North Atlantic ◽

Sunshine Duration ◽

Global Solar Radiation ◽

Global Scale ◽

High Mountain ◽

Clear Sky ◽

Downward Radiation ◽

Radiation Time

Abstract. This paper presents the re-construction of the 80 year time series of daily global shortwave downward radiation (SDR) at the subtropical high-mountain Izaña Atmospheric Observatory (IZO, Spain). For this purpose, we combine SDR estimates from sunshine duration (SD) data using the Ångström–Prescott method over the 1933/1991 period, and SDR observations directly performed by pyranometers between 1992 and 2013. Since SDR measurements have been used as a reference, a strict quality control has been applied, when it was not possible data have been re-calibrated by using the LibRadtran model. By comparing to high quality SDR measurements, the precision and consistency over time of SDR estimations from SD data have successfully been documented. We obtain a overall root mean square error (RMSE) of 9.2% and an agreement between the variances of SDR estimations and SDR measurements within 92% (correlation coefficient of 0.96). Nonetheless, this agreement significantly increases when the SDR estimation is done considering different daily fractions of clear sky (FCS). In that case, RMSE is reduced by half, up to about 4.5%, when considering percentages of FCS > 40% (90% of days in the testing period). Furthermore, we prove that the SDR estimations can monitor the SDR anomalies in consistency with SDR measurements and, then, can be suitable for re-constructing solar radiation time series. The re-constructed IZO global SDR time series between 1933 and 2013 confirms discontinuities and periods of increases/decreases of solar radiation at Earth's surface observed at a global scale, such as the early brightening, dimming and brightening. This fact supports the consistency of the IZO SDR time series presented in this work, which may be a reference for solar radiation studies in the subtropical North Atlantic region.

Download Full-text

Anomalous high ozone concentrations recorded at a high mountain station in Italy in summer 2003

Atmospheric Environment ◽

10.1016/j.atmosenv.2006.10.017 ◽

2007 ◽

Vol 41 (7) ◽

pp. 1383-1394 ◽

Cited By ~ 47

Author(s):

P. Cristofanelli ◽

P. Bonasoni ◽

G. Carboni ◽

F. Calzolari ◽

L. Casarola ◽

...

Keyword(s):

High Mountain ◽

Ozone Concentrations ◽

Mountain Station

Download Full-text

Non-parametric and least squares Langley plot methods

Atmospheric Measurement Techniques ◽

10.5194/amt-9-215-2016 ◽

2016 ◽

Vol 9 (1) ◽

pp. 215-225 ◽

Cited By ~ 8

Author(s):

P. W. Kiedron ◽

J. J. Michalsky

Keyword(s):

Time Series ◽

Solar Radiation ◽

Least Squares ◽

High Mountain ◽

Moving Window ◽

Calibration Technique ◽

Air Mass ◽

Straightforward Application ◽

Straight Line ◽

Non Parametric

Abstract. Langley plots are used to calibrate sun radiometers primarily for the measurement of the aerosol component of the atmosphere that attenuates (scatters and absorbs) incoming direct solar radiation. In principle, the calibration of a sun radiometer is a straightforward application of the Bouguer–Lambert–Beer law V = V0e−τ ⋅ m, where a plot of ln(V) voltage vs. m air mass yields a straight line with intercept ln(V0). This ln(V0) subsequently can be used to solve for τ for any measurement of V and calculation of m. This calibration works well on some high mountain sites, but the application of the Langley plot calibration technique is more complicated at other, more interesting, locales. This paper is concerned with ferreting out calibrations at difficult sites and examining and comparing a number of conventional and non-conventional methods for obtaining successful Langley plots. The 11 techniques discussed indicate that both least squares and various non-parametric techniques produce satisfactory calibrations with no significant differences among them when the time series of ln(V0)'s are smoothed and interpolated with median and mean moving window filters.

Download Full-text

Impacts of topographic shading on direct solar radiation for valley glaciers in complex topography

The Cryosphere ◽

10.5194/tc-13-29-2019 ◽

2019 ◽

Vol 13 (1) ◽

pp. 29-40 ◽

Cited By ~ 6

Author(s):

Matthew Olson ◽

Summer Rupper

Keyword(s):

Energy Balance ◽

Solar Radiation ◽

Surface Energy ◽

Surface Energy Balance ◽

Direct Solar Radiation ◽

High Mountain ◽

Clear Sky ◽

Glacier Ice ◽

Solar Radiation Model ◽

North And South

Abstract. Topographic shading, including both shaded relief and cast shadowing, plays a fundamental role in determining direct solar radiation on glacier ice. However, shading has been oversimplified or incorrectly incorporated in surface energy balance models in some past studies. In addition, no systematic studies have been conducted to evaluate relationships between shading and other topographic characteristics. Here we develop a topographic solar radiation model to examine the variability in irradiance throughout the glacier melt season due to topographic shading and combined slope and aspect. We apply the model to multiple glaciers in high-mountain Asia (HMA) and test the sensitivity of shading to valley aspect and latitude. Our results show that topographic shading significantly alters the potential direct clear-sky solar radiation received at the surface for valley glaciers in HMA, particularly for north- and south-facing glaciers. Additionally, we find that shading can be extremely impactful in the ablation zone. Cast shadowing is the dominant mechanism in determining total shading for valley glaciers in parts of HMA, especially at lower elevations. Although shading can be predictable, it is overall extremely variable between glacial valleys. Our results suggest that topographic shading not only is an important factor contributing to surface energy balance but could also influence glacier response and mass balance estimates throughout HMA.

Download Full-text

Surface ozone at the Caucasian site Kislovodsk High Mountain Station and the Swiss Alpine site Jungfraujoch: data analysis and trends (1990–2006)

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-4157-2009 ◽

2009 ◽

Vol 9 (12) ◽

pp. 4157-4175 ◽

Cited By ~ 18

Author(s):

O. A. Tarasova ◽

I. A. Senik ◽

M. G. Sosonkin ◽

J. Cui ◽

J. Staehelin ◽

...

Keyword(s):

Western Europe ◽

Surface Ozone ◽

Lower Troposphere ◽

High Mountain ◽

Free Troposphere ◽

Mixing Ratios ◽

Mountain Station ◽

Ozone Trends ◽

Transport Patterns ◽

In The Beginning

Abstract. Long-term ozone measurements of two background mountain sites, namely the Kislovodsk High Mountain Station in Caucasus, Russia (KHMS, 43.70° N, 42.70° E, 2070 m a.s.l.) and the Jungfraujoch in Switzerland (JFJ, 46.55° N, 7.98° E, 3580 m a.s.l.) are compared. Despite of more than 1.5 km altitude difference ozone mixing ratios are comparable at JFJ an KHMS in the beginning of measurements (1990–1993) while the annually averaged levels at JFJ are around 15 ppb higher than the ones at KHMS for the most recent years (1997–2006). The seasonal cycle of the surface ozone mixing ratios is characterized by a double spring-summer maximum at both sites with a spring one being more pronounced for the air masses with the longest contact with the upper free troposphere and stratosphere. Ozone mixing ratio increased at JFJ but decreased at KHMS for the period 1990–2006. Trends are more pronounced for the 1990s (+0.73±0.20 ppb/year at JFJ and −0.91±0.17 ppb/year at KHMS for the period 1991–2001) in comparison with the later years (+0.04±0.21 ppb/year at JFJ and −0.37±0.14 ppb/year at KHMS for the period 1997–2006). Trends show a distinct seasonality, which is different for the different periods. To investigate possible reasons for this remarkable trends difference 3-D trajectories using LAGRANTO trajectory model are used. Effects of horizontal and vertical transport on ozone trends are considered. No substantial systematic changes in the transport patterns were detected which could lead to strong changes in the trend magnitude between 1991–2001 and 1997–2006. The geographical position of the sites relative to the main topographic features and emission sources as well as distance from the coast are interpreted to be among the main reasons for the opposite surface ozone trends. During the 90s the JFJ trend reflects increase of the ozone in the upper free troposphere/lower stratosphere, while KHMS is not sensitive to this change or even showing the opposite tendency. The analysis provided evidence for a stronger influence of processes in the lower troposphere, in particular the dramatic emission decrease in the earlier 1990s in former USSR and emissions regulations in Western Europe on the surface ozone trend at KHMS.

Download Full-text