Anisotropy Parameterization Development and Evaluation for Glacier Surface Albedo Retrieval from Satellite Observations

Ren, Shaoting; Miles, Evan; Li, Jia; Menenti, Massimo; Kneib, Marin; Buri, Pascal; McCarthy, Mike; Shaw, Thomas E.; Yang, Wei; Pellicciotti, Francesca

doi:10.3390/rs13091714

Cited by 11 publications

(16 citation statements)

References 56 publications

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“…The modeled glacier albedo in the uppermost zones of the catchment (>6,000 m.a.s.l.) gives a slight bias compared to the LS8 observations and matches the ST2 data well especially during winter, which points to the discrepancy between the two remotely sensed products and associated uncertainties (Ren et al., 2021).…”

Section: Resultsmentioning

confidence: 69%

“…We derived glacier albedo values from Landsat 8, “LS8,” and Sentinel 2, “ST2,” following the approach of Ren et al. (2021) (Text S4.3 in Supporting Information ) and compared them to simulated mean glacier albedo values (excluding debris‐covered areas) per 200 m elevation band (Figure 3b). Modeled glacier albedo reproduces the seasonal cycle at lowest elevation (4,800–5,000 m.a.s.l.…”

Section: Resultsmentioning

confidence: 99%

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Land Surface Modeling in the Himalayas: On the Importance of Evaporative Fluxes for the Water Balance of a High‐Elevation Catchment

Buri,

Fatichi,

Shaw

et al. 2023

Water Resources Research

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High Mountain Asia (HMA) is among the most vulnerable water towers globally and yet future projections of water availability in and from its high‐mountain catchments remain uncertain, as their hydrologic response to ongoing environmental changes is complex. Mechanistic modeling approaches incorporating cryospheric, hydrological, and vegetation processes in high spatial, temporal, and physical detail have never been applied for high‐elevation catchments of HMA. We use a land surface model at high spatial and temporal resolution (100 m and hourly) to simulate the coupled dynamics of energy, water, and vegetation for the 350 km2 Langtang catchment (Nepal). We compare our model outputs for one hydrological year against a large set of observations to gain insight into the partitioning of the water balance at the subseasonal scale and across elevation bands. During the simulated hydrological year, we find that evapotranspiration is a key component of the total water balance, as it causes about the equivalent of 20% of all the available precipitation or 154% of the water production from glacier melt in the basin to return directly to the atmosphere. The depletion of the cryospheric water budget is dominated by snow melt, but at high elevations is primarily dictated by snow and ice sublimation. Snow sublimation is the dominant vapor flux (49%) at the catchment scale, accounting for the equivalent of 11% of snowfall, 17% of snowmelt, and 75% of ice melt, respectively. We conclude that simulations should consider sublimation and other evaporative fluxes explicitly, as otherwise water balance estimates can be ill‐quantified.

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Section: Resultsmentioning

confidence: 69%

Section: Resultsmentioning

confidence: 99%

Land Surface Modeling in the Himalayas: On the Importance of Evaporative Fluxes for the Water Balance of a High‐Elevation Catchment

Buri,

Fatichi,

Shaw

et al. 2023

Water Resources Research

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“…4, Azha, and Xueyougu Glaciers revealed additional insights on temporal and spatial changes (Figure 5). We have improved and evaluated a method to correct glacier and snow reflectance for anisotropy and retrieve better albedo (hemispherical reflectance) [21]. The anisotropy correction was developed using airborne directional measurements of spectral reflectance and comparing alternate parameterizations [21].…”

Section: Research Results and Conclusionmentioning

confidence: 99%

“…We have improved and evaluated a method to correct glacier and snow reflectance for anisotropy and retrieve better albedo (hemispherical reflectance) [21]. The anisotropy correction was developed using airborne directional measurements of spectral reflectance and comparing alternate parameterizations [21]. This method was applied to retrieve glacier albedo in the entire WNM using MODIS data for the period 2001-2020 (Figure 6).…”

Section: Research Results and Conclusionmentioning

confidence: 99%

Multi-Source Hydrological Data Products to Monitor High Asian River Basins and Regional Water Security

Menenti

et al. 2021

Remote Sensing

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This project explored the integrated use of satellite, ground observations and hydrological distributed models to support water resources assessment and monitoring in High Mountain Asia (HMA). Hydrological data products were generated taking advantage of the synergies of European and Chinese data assets and space-borne observation systems. Energy-budget-based glacier mass balance and hydrological models driven by satellite observations were developed. These models can be applied to describe glacier-melt contribution to river flow. Satellite hydrological data products were used for forcing, calibration, validation and data assimilation in distributed river basin models. A pilot study was carried out on the Red River basin. Multiple hydrological data products were generated using the data collected by Chinese satellites. A new Evapo-Transpiration (ET) dataset from 2000 to 2018 was generated, including plant transpiration, soil evaporation, rainfall interception loss, snow/ice sublimation and open water evaporation. Higher resolution data were used to characterize glaciers and their response to environmental forcing. These studies focused on the Parlung Zangbo Basin, where glacier facies were mapped with GaoFeng (GF), Sentinal-2/Multi-Spectral Imager (S2/MSI) and Landsat8/Operational Land Imager (L8/OLI) data. The geodetic mass balance was estimated between 2000 and 2017 with Zi-Yuan (ZY)-3 Stereo Images and the SRTM DEM. Surface velocity was studied with Landsat5/Thematic Mapper (L5/TM), L8/OLI and S2/MSI data over the period 2013–2019. An updated method was developed to improve the retrieval of glacier albedo by correcting glacier reflectance for anisotropy, and a new dataset on glacier albedo was generated for the period 2001–2020. A detailed glacier energy and mass balance model was developed with the support of field experiments at the Parlung No. 4 Glacier and the 24 K Glacier, both in the Tibetan Plateau. Besides meteorological measurements, the field experiments included glaciological and hydrological measurements. The energy balance model was formulated in terms of enthalpy for easier treatment of water phase transitions. The model was applied to assess the spatial variability in glacier melt. In the Parlung No. 4 Glacier, the accumulated glacier melt was between 1.5 and 2.5 m w.e. in the accumulation zone and between 4.5 and 6.0 m w.e. in the ablation zone, reaching 6.5 m w.e. at the terminus. The seasonality in the glacier mass balance was observed by combining intensive field campaigns with continuous automatic observations. The linkage of the glacier and snowpack mass balance with water resources in a river basin was analyzed in the Chiese (Italy) and Heihe (China) basins by developing and applying integrated hydrological models using satellite retrievals in multiple ways. The model FEST-WEB was calibrated using retrievals of Land Surface Temperature (LST) to map soil hydrological properties. A watershed model was developed by coupling ecohydrological and socioeconomic systems. Integrated modeling is supported by an updated and parallelized data assimilation system. The latter exploits retrievals of brightness temperature (Advanced Microwave Scanning Radiometer, AMSR), LST (Moderate Resolution Imaging Spectroradiometer, MODIS), precipitation (Tropical Rainfall Measuring Mission (TRMM) and FengYun (FY)-2D) and in-situ measurements. In the case study on the Red River Basin, a new algorithm has been applied to disaggregate the SMOS (Soil Moisture and Ocean Salinity) soil moisture retrievals by making use of the correlation between evaporative fraction and soil moisture.

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“…Although this approach still retains some mixed pixels that can lead to low albedo, it is an inevitable compromise since the limited number of MODIS pixels with 100% glacier fractional abundance was insufficient to capture spatial patterns and changes of albedo in the WNM. The method applied to retrieve albedo in this study was developed for clean ice (Ren and others, 2021), so the debris-covered glaciers were excluded. The impact of excluding debris-covered glaciers on regional glacier albedo was limited, since these glaciers account for 2% of total glacier area only.…”

Section: Datamentioning

confidence: 99%

Changes in glacier albedo and the driving factors in the Western Nyainqentanglha Mountains from 2001 to 2020

Ren

Menenti

2023

J. Glaciol.

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Glacier surface albedo dominates glacier energy balance, thus strongly affecting the glacier mass balance. Glaciers in the Western Nyainqentanglha Mountains (WNM) experienced large mass losses in the past two decades, but long-term changes of glacier albedo and its drivers are less understood. In this study, we retrieved glacier albedo with MODIS reflectance data to characterize the spatiotemporal variability of albedo from 2001 to 2020. Air temperature, rainfall, snowfall and deposition of light-absorbing impurities (LAIs) were evaluated as potential drivers of the observed variability in glacier albedo. The results showed that: (1) the glacier albedo experienced large inter-annual fluctuations, with the mean albedo being 0.552 ± 0.002 and a clear decreasing trend of 0.0443 ± 2 × 10−4 dec−1 in the WNM. The fastest decline was observed in autumn and in the vicinity of the equilibrium line altitude, indicating an extended melt season and an expansion of the ablation region to higher elevation; (2) local meteorology and LAIs deposition are the main drivers of glacier albedo change, but their effects on seasonal albedos are different due to different glacier processes. Both air temperature and the balance between liquid and solid precipitation affect summer and autumn albedos due to glacier ablation. Air temperature is the main driver of spring and winter albedos due to sublimation and metamorphism of snow, while snowfall carried by westerlies has limited influence on these two seasonal albedos due to less snowfall. LAIs mainly affect spring albedo due to high concentration coupled with the southerly wind in spring. These findings highlight the significance of changes in glacier albedo and the key role of local meteorology and LAIs deposition in determining such changes, which play an important role in glaciological and cryosphere processes.

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Anisotropy Parameterization Development and Evaluation for Glacier Surface Albedo Retrieval from Satellite Observations

Cited by 11 publications

References 56 publications

Land Surface Modeling in the Himalayas: On the Importance of Evaporative Fluxes for the Water Balance of a High‐Elevation Catchment

Land Surface Modeling in the Himalayas: On the Importance of Evaporative Fluxes for the Water Balance of a High‐Elevation Catchment

Multi-Source Hydrological Data Products to Monitor High Asian River Basins and Regional Water Security

Changes in glacier albedo and the driving factors in the Western Nyainqentanglha Mountains from 2001 to 2020

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