Correcting for the influence of frozen lakes in satellite microwave radiometer observations through application of a microwave emission model

Lemmetyinen, Juha; Kontu, Anna; Karna, J.-P.; Vehviläinen, Juho; Takala, Matias; Pulliainen, Jouni

doi:10.1016/j.rse.2011.09.008

Cited by 24 publications

(12 citation statements)

References 35 publications

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“…For the subarctic (Figure ), there is greater disagreement between SSM/I and simulated T B at 19 GHz due to the high lake fraction in this region, a source of positive bias in HUT simulations identified in previous studies [ Derksen et al ., ; Gunn et al ., ; Lemmetyinen et al ., ]. At 37 GHz (where lake ice fraction also introduces some additional uncertainty), the results are similar as at the high Arctic site: the range in simulated T B from the HUT simulations with varying stratigraphic inputs extends far below the SSM/I measured brightness temperatures.…”

Section: Resultsmentioning

confidence: 99%

Physical properties of Arctic versus subarctic snow: Implications for high latitude passive microwave snow water equivalent retrievals

Derksen

Lemmetyinen

Toose

et al. 2014

J. Geophys. Res. Atmos.

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Two unique observational data sets are used to evaluate the ability of multi-layer snow emission models to simulate passive microwave brightness temperatures (T B ) in high latitude, observation sparse, snow-covered environments. Data were utilized from a coordinated series of 18 sites measured across the subarctic Northwest Territories and Nunavut, Canada in April 2007 during a 1000 km segment of a 4200 km snowmobile traverse from Fairbanks, Alaska to Baker Lake, Nunavut (~64°N). In April 2011, a network of 22 high Arctic sites was sampled across a 60 × 60 km study area on the Fosheim Peninsula, Ellesmere Island (~80°N). In comparison to sites across the subarctic, high Arctic snow was more spatially variable, thinner (site averages between 15 and 25 cm versus 30 to 40 cm), colder (À25°C versus À10°C), composed of fewer layers, had a proportionally higher fraction of wind slabs (storing 57% of the snow water equivalent (SWE) versus 15%), with these slabs comparatively denser (often exceeding 450 g/cm 3 , compared to 350 g/cm 3 in the subarctic). The physical snow measurements were used as inputs to snow emission model simulations.The radiometric difference between simulations of "typical" arctic and subarctic snow reached 30 K at 37 GHz. Sensitivity analysis showed that this T B difference could be partitioned between the effects of physical temperature (~5 K between À25°C and À10°C), wind slab density (~5 K between 0.40and 0.35 g/cm 3 ), and vertical depth hoar fraction (~20 K between 70% and 30% vertical fraction of total snow depth). Model simulations at the satellite scale (625 km 2 ) were produced using the observational spread for snow depth and snow stratigraphy. The range of T B from simulations with varied stratigraphy extended unrealistically far below the magnitude of satellite measured T B , illustrating that the snow depth first guess is very important for SWE retrieval schemes that are based on forward emission model simulations.

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Section: Resultsmentioning

confidence: 99%

Physical properties of Arctic versus subarctic snow: Implications for high latitude passive microwave snow water equivalent retrievals

Derksen

Lemmetyinen

Toose

et al. 2014

J. Geophys. Res. Atmos.

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“…-Water bodies strongly affect microwave emission of the ground, which is known to lead to underestimation of SWE in passive microwave-based retrievals (Rees et al, 2006;Lemmetyinen et al, 2011). For the abovementioned N Canada data set, water bodies might explain the significant bias of 36 mm , but the average values (120 mm) are also sufficiently high that saturation effects (Luojus et al, 2010) are likely to contribute to the bias.…”

Section: Snowmentioning

confidence: 98%

“…The largest impact on SWE retrievals is most likely during lake freezing and snow cover buildup in fall, when GlobSnow SWE retrievals must be considered highly uncertain. In the future, enhanced SWE retrieval algorithms taking the effect of water bodies explicitly into account (e.g., Lemmetyinen et al, 2011) may become available.…”

Section: Snowmentioning

confidence: 99%

Transient modeling of the ground thermal conditions using satellite data in the Lena River delta, Siberia

et al. 2017

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Abstract. Permafrost is a sensitive element of the cryosphere, but operational monitoring of the ground thermal conditions on large spatial scales is still lacking. Here, we demonstrate a remote-sensing-based scheme that is capable of estimating the transient evolution of ground temperatures and active layer thickness by means of the ground thermal model CryoGrid 2. The scheme is applied to an area of approximately 16 000 km 2 in the Lena River delta (LRD) in NE Siberia for a period of 14 years. The forcing data sets at 1 km spatial and weekly temporal resolution are synthesized from satellite products and fields of meteorological variables from the ERA-Interim reanalysis. To assign spatially distributed ground thermal properties, a stratigraphic classification based on geomorphological observations and mapping is constructed, which accounts for the large-scale patterns of sediment types, ground ice and surface properties in the Lena River delta.A comparison of the model forcing to in situ measurements on Samoylov Island in the southern part of the study area yields an acceptable agreement for the purpose of ground thermal modeling, for surface temperature, snow depth, and timing of the onset and termination of the winter snow cover. The model results are compared to observations of ground temperatures and thaw depths at nine sites in the Lena River delta, suggesting that thaw depths are in most cases reproduced to within 0.1 m or less and multi-year averages of ground temperatures within 1-2 • C. Comparison of monthly average temperatures at depths of 2-3 m in five boreholes yielded an RMSE of 1

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“…Microwave emissions from a non-scattering atmosphere are governed by both air temperature and atmosphere optical thickness, which is approximately the sum of the optical thickness of oxygen, cloud liquid water, and atmospheric water vapor (Wang and Tedesco, 2007;Du et al, 2015). Microwave emissions from a lake with an upper layer that may consist of water, ice, and snow are determined by a number of factors; these factors include lake surface roughness, water dielectric properties mainly affected by water salinity and temperature, ice thickness and dielectric properties, and snow cover dielectric properties mainly controlled by snow density and wetness, snow particle size, and stratification of snow and ice layers (Du et al, 2010;Lemmetyinen et al, 2010Lemmetyinen et al, , 2011. Despite the complexity of the lake emission problem, sharp changes in satellite microwave T b observations at multiple frequencies are evident during the transitions between lake freeze-up and breakup periods.…”

Section: Algorithm Theoretical Basismentioning

confidence: 99%

Satellite microwave assessment of Northern Hemisphere lake ice phenology from 2002 to 2015

Kimball

Duguay

et al. 2017

The Cryosphere

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Abstract.A new automated method enabling consistent satellite assessment of seasonal lake ice phenology at 5 km resolution was developed for all lake pixels (water coverage ≥ 90 %) in the Northern Hemisphere using 36.5 GHz H-polarized brightness temperature (T b ) observations from the Advanced Microwave Scanning Radiometer for EOS and Advanced Microwave Scanning Radiometer 2 (AMSR-E/2) sensors. The lake phenology metrics include seasonal timing and duration of annual ice cover. A moving t test (MTT) algorithm allows for automated lake ice retrievals with daily temporal fidelity and 5 km resolution gridding. The resulting ice phenology record shows strong agreement with available ground-based observations from the Global Lake and River Ice Phenology Database (95.4 % temporal agreement) and favorable correlations (R) with alternative ice phenology records from the Interactive Multisensor Snow and Ice Mapping System (R = 0.84 for water clear of ice (WCI) dates; R = 0.41 for complete freeze over (CFO) dates) and Canadian Ice Service (R = 0.86 for WCI dates; R = 0.69 for CFO dates). Analysis of the resulting 12-year (2002-2015) AMSR-E/2 ice record indicates increasingly shorter ice cover duration for 43 out of 71 (60.6 %) Northern Hemisphere lakes examined, with significant (p < 0.05) regional trends toward earlier ice melting for only five lakes. Higherlatitude lakes reveal more widespread and larger trends toward shorter ice cover duration than lower-latitude lakes, consistent with enhanced polar warming. This study documents a new satellite-based approach for rapid assessment and regional monitoring of seasonal ice cover changes over large lakes, with resulting accuracy suitable for global change studies.

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Correcting for the influence of frozen lakes in satellite microwave radiometer observations through application of a microwave emission model

Cited by 24 publications

References 35 publications

Physical properties of Arctic versus subarctic snow: Implications for high latitude passive microwave snow water equivalent retrievals

Physical properties of Arctic versus subarctic snow: Implications for high latitude passive microwave snow water equivalent retrievals

Transient modeling of the ground thermal conditions using satellite data in the Lena River delta, Siberia

Satellite microwave assessment of Northern Hemisphere lake ice phenology from 2002 to 2015

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