Sensitivity of bare soil albedo to surface soil moisture on the moraine of the Zongo glacier (Bolivia)

Gascoin, Simon; Ducharne, Agnès; Ribstein, Pierre; Perroy, E.; Wagnon, Patrick

doi:10.1029/2008gl036377

Cited by 37 publications

(33 citation statements)

References 23 publications

(24 reference statements)

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“…Future applications are certainly possible, especially considering the low cost, the autonomy of the LCA in terms of energy, and the very small size of the sensors. For example, the LCA could be useful to spatialize in situ albedos in glacierized catchments both on the glacier, where the evolution of the snow cover can be monitored, and in the non-glacierized part for the evolution of the seasonal snow cover and, more generally, the changes in the ground albedo due to, for example, variations in the soil moisture (Gascoin et al, 2009). The comparison between the LCA measurements and LANDSAT images during the period extending from 18 October 2015 to 30 June 2016 showed that the LCA is a powerful tool that can be used to quantify the evolution of the albedo index and characterize the surface state of the glacier by distinguishing between fresh snow, dirty snow, and ice.…”

Section: Discussionmentioning

confidence: 99%

Technical note: A low-cost albedometer for snow and ice measurements – theoretical results and application on a tropical mountain in Bolivia

Condom

Dumont²,

Mourre

et al. 2018

Geosci. Instrum. Method. Data Syst.

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Abstract. This study presents a new instrument called a lowcost albedometer (LCA) composed of two illuminance sensors that are used to measure in situ incident and reflected illuminance values on a daily timescale. The ratio between reflected vs. incident illuminances is called the albedo index and can be compared with actual albedo values. Due to the shape of the sensor, the direct radiation for zenith angles ranging from 55 to 90 • is not measured. The spectral response of the LCA varies with the solar irradiance wavelengths within the range 0.26 to 1.195 µm, and the LCA detects 85 % of the total spectral solar irradiance for clear sky conditions. We first consider the theoretical results obtained for 10 different ice and snow surfaces with clear sky and cloudy sky incident solar irradiance that show that the LCA spectral response may be responsible for an overestimation of the theoretical albedo values by roughly 9 % at most. Then, the LCA values are compared with two "traditional" albedometers, which are CM3 pyranometers (Kipp & Zonen), in the shortwave domain from 0.305 to 2.800 µm over a 1-year measurement period (2013) for two sites in a tropical mountainous catchment in Bolivia. One site is located on the Zongo Glacier (i.e., snow and ice surfaces) and the second one is found on the crest of the lateral moraine (bare soil and snow surfaces), which present a horizontal surface and a sky view factor of 0.98. The results, at daily time steps (256 days), given by the LCA are in good agreement with the classic albedo measurements taken with pyranometers with R 2 = 0.83 (RMSD = 0.10) and R 2 = 0.92 (RMSD = 0.08) for the Zongo Glacier and the right-hand side lateral moraine, respectively. This demonstrates that our system performs well and thus provides relevant opportunities to document spatiotemporal changes in the surface albedo from direct observations at the scale of an entire catchment at a low cost. Finally, during the period from September 2015 to June 2016, direct observations were collected with 15 LCAs on the Zongo Glacier and successfully compared with LANDSAT images showing the surface conditions of the glacier (i.e., snow or ice). This comparison illustrates the efficiency of this system to monitor the daily time step changes in the snow and ice coverage distributed on the glacier. Despite the limits imposed by the angle view restrictions, the LCA can be used between 45 • N and 45 • S during the ablation season (spring and summer) when the melt rate related to the albedo is the most important.

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Section: Discussionmentioning

confidence: 99%

Technical note: A low-cost albedometer for snow and ice measurements – theoretical results and application on a tropical mountain in Bolivia

Condom

Dumont²,

Mourre

et al. 2018

Geosci. Instrum. Method. Data Syst.

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“…Domingo et al, 2000;Lobell and Asner, 2002;Gascoin et al, 2009). This limitation is justified for two reasons: First, soil hydrology is represented by a rather crude bucket model in JSBACH of 1 m depth, while albedo is only affected by soil water if the upper few millimetres to centimetres of the soil are wet (Gascoin et al, 2009). This effect can thus not be included in the current version of JSBACH in an appropriate way.…”

Section: Dynamic Background Albedomentioning

confidence: 99%

The effect of a dynamic background albedo scheme on Sahel/Sahara precipitation during the mid-Holocene

2011

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Abstract.We have implemented a new albedo scheme that takes the dynamic behaviour of the surface below the canopy into account, into the land-surface scheme of the MPI-ESM. The standard (static) scheme calculates the seasonal canopy albedo as a function of leaf area index, whereas the background albedo is a gridbox constant derived from satellite measurements. The new (dynamic) scheme additionally models the background albedo as a slowly changing function of organic matter in the ground and of litter and standing dead biomass covering the ground. We use the two schemes to investigate the interactions between vegetation, albedo and precipitation in the Sahel/Sahara for two time-slices: preindustrial and mid-Holocene. The dynamic scheme represents the seasonal cycle of albedo and the correspondence between annual mean albedo and vegetation cover in a more consistent way than the static scheme. It thus gives a better estimate of albedo change between the two time periods. With the introduction of the dynamic scheme, precipitation is increased by 30 mm yr −1 for the pre-industrial simulation and by about 80 mm yr −1 for the mid-Holocene simulation. The present-day dry bias in the Sahel of standard ECHAM5 is thus reduced and the sensitivity of precipitation to mid-Holocene external forcing is increased by around one third. The locations of mid-Holocene lakes, as estimated from reconstructions, lie south of the modelled desert border in both mid-Holocene simulations. The magnitude of simulated rainfall in this area is too low to fully sustain lakes, however it is captured better with the dynamic scheme. The dynamic scheme leads to increased vegetation variability in the remaining desert region, indicating a higher frequency of green spells, thus reaching a better agreement with the vegetation distribution as derived from pollen records.

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“…But Idso et al 's [1975] work has been challenged by more recent studies which indicated that, for many soil types, a nonlinear exponential relationship is more appropriate to depict the dependence of bare soil albedo on water content [ Duke and Guérif , 1998; Liu et al , 2002; Lobell and Asner , 2002; Wang et al , 2005; Gascoin et al , 2009a].…”

Section: Introductionmentioning

confidence: 99%

Dependence of bare soil albedo on soil moisture on the moraine of the Zongo glacier (Bolivia): Implications for land surface modeling

et al. 2009

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[1] Although the dependence of bare soil albedo on soil moisture is a familiar observation, it is not commonly represented in climate modeling. We investigate the impact of this dependence in a land surface model using meteorological data collected on the moraine of a Bolivian glacier. The relationship which is implemented to simulate albedo variations with soil moisture is deduced from a previous field study. The model is set up at the scale of the meteorological station plot to have the most accurate control on the model calibration and validation. A snow parameter is modified to account for the fact that the model was designed for larger cell sizes. Water content measurements are used to calibrate the parameter controlling the vertical water fluxes within the soil surface layer. This allows us to enhance the model's ability to capture the fast changes in surface soil moisture. The comparison of simulated ground heat flux and outgoing longwave radiations with observations shows that the model performs well despite the fact that all other parameters are set a priori on the basis of local properties of the surface. The results show that the dependence of bare soil albedo on soil moisture, which causes an increase in the net radiation, importantly influences the turbulent fluxes at the annual and monthly time scales. The mean annual evaporation is increased by 12%. As a consequence, this parameterization modifies the computed runoff, which is reduced by more than 5% during the rainy season.

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Sensitivity of bare soil albedo to surface soil moisture on the moraine of the Zongo glacier (Bolivia)

Cited by 37 publications

References 23 publications

Technical note: A low-cost albedometer for snow and ice measurements – theoretical results and application on a tropical mountain in Bolivia

Technical note: A low-cost albedometer for snow and ice measurements – theoretical results and application on a tropical mountain in Bolivia

The effect of a dynamic background albedo scheme on Sahel/Sahara precipitation during the mid-Holocene

Dependence of bare soil albedo on soil moisture on the moraine of the Zongo glacier (Bolivia): Implications for land surface modeling

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