Meteorological atmospheric boundary layer measurements and ECMWF analyses during summer at Dome C, Antarctica

Genthon, Christophe; Town, Michael S.; Six, Delphine; Favier, Vincent; Argentini, Stefania; Pellegrini, A.

doi:10.1029/2009jd012741

Cited by 86 publications

(152 citation statements)

References 37 publications

(69 reference statements)

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“…To our knowledge, no previous study has performed an evaluation of MODIS LST with as much detail and as many in situ observations. Further, by comparing in situ surface temperature instead of in situ nearsurface air temperature, we avoid the uncertainties in the observation of T 2 m over the Antarctic Plateau as documented in Genthon et al (2010). Hourly MODIS T s from 2000 to 2011 was used to evaluate the accuracy of snow surface temperature in the ERA-Interim reanalysis and the one produced by a stand-alone simulation with the Crocus snowpack model using ERA-Interim forcing.…”

Section: Discussionmentioning

confidence: 99%

“…The difficulty of properly estimating the surface turbulent fluxes under very stable conditions has been extensively documented (for example Brun et al (1997), Martin and Lejeune (1998), Essery and Etchevers (2004), Anderson and Neff (2008), Sukoriansky et al (2006), Town and Walden (2009), Genthon et al (2010), Holtslag et al (2013)). Ad hoc treatments are often introduced in meteorological and snow models to solve the problem, as was done in SURFEX/Crocus with the introduction of the limitation in the Richardson number.…”

Section: Causes Of the Era-interim Warm Biasmentioning

confidence: 99%

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Using MODIS land surface temperatures and the Crocus snow model to understand the warm bias of ERA-Interim reanalyses at the surface in Antarctica

et al. 2014

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Abstract. Moderate-Resolution Imaging spectroradiometer (MODIS) land surface temperatures in Antarctica were processed in order to produce a gridded data set at 25 km resolution, spanning the period 2000-2011 at an hourly time step. The Aqua and Terra orbits and MODIS swath width, combined with frequent clear-sky conditions, lead to very high availability of quality-controlled observations: on average, hourly data are available 14 h per day at the grid points around the South Pole and more than 9 h over a large area of the Antarctic Plateau. Processed MODIS land surface temperatures, referred to hereinafter as MODIS T s values, were compared with in situ hourly measurements of surface temperature collected over the entirety of the year 2009 by seven stations from the Baseline Surface Radiation Network (BSRN) and automatic weather stations (AWSs). In spite of an occasional failure in the detection of clouds, MODIS T s values exhibit a good performance, with a bias ranging from −1.8 to 0.1 • C and errors ranging from 2.2 to 4.8 • C root mean square at the five stations located on the plateau. These results show that MODIS T s values can be used as a precise and accurate reference to test other surface temperature data sets. Here, we evaluate the performance of surface temperature in the European Centre for MediumRange Weather Forecasts (ECMWF) reanalysis known as ERA-Interim reanalysis. During conditions detected as cloud free by MODIS, ERA-Interim shows a widespread warm bias in Antarctica in every season, ranging from +3 to +6 • C on the plateau. This confirms a recent study which showed that the largest discrepancies in 2 m air temperature between ERA-Interim and the global temperature data set HadCRUT4 compiled by the Met Office Hadley Centre and the University of East Anglia's Climatic Research Unit occur in Antarctica. A comparison with in situ surface temperature shows that this bias is not strictly limited to clear-sky conditions. A detailed comparison with stand-alone simulations by the Crocus snowpack model, forced by ERA-Interim, and with the ERA-Interim/land simulations, shows that the warm bias may be due primarily to an overestimation of the surface turbulent fluxes in very stable conditions. Numerical experiments with Crocus show that a small change in the parameterization of the effects of stability on the surface exchange coefficients can significantly impact the snow surface temperature. The ERA-Interim warm bias appears to be likely due to an overestimation of the surface exchange coefficients under very stable conditions.

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Section: Discussionmentioning

confidence: 99%

Section: Causes Of the Era-interim Warm Biasmentioning

confidence: 99%

Using MODIS land surface temperatures and the Crocus snow model to understand the warm bias of ERA-Interim reanalyses at the surface in Antarctica

et al. 2014

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“…Air temperature at 2 m and wind speed are also observed with an automatic weather station (AWS). Errors of these measurements are caused, among other things, by radiative heating of the shelter housing the thermometer (Genthon et al, 2010) and inaccuracy in the reference black body of the IR sensor. Overall, we estimate that the accuracy is 1.5 • C for the air and snow skin temperatures.…”

Section: Methodsmentioning

confidence: 99%

“…Overall, we estimate that the accuracy is 1.5 • C for the air and snow skin temperatures. We also used temperature, humidity and wind speed data at 4 m height from the 45 m height tower where sensors are ventilated as detailed by Genthon et al (2010).…”

Section: Methodsmentioning

confidence: 99%

“…These data are provided on a 3 h time step and have been processed as in Brun et al (2013). Operational analyses from the European Centre for Medium-Range Weather Forecasts (ECMWF) similar to ERA-Interim have been evaluated at Dome C with respect to field measurements of temperature, humidity and wind speed at different levels on a 45 m tower by Genthon et al (2010). They determined a small warm bias of temperature relative to observations for all height.…”

Section: Modelingmentioning

confidence: 99%

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The growth of sublimation crystals and surface hoar on the Antarctic plateau

et al. 2014

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Abstract. On the Antarctic plateau, precipitation quantities are so low that the surface mass budget is for an important part determined by exchanges of water vapor between the snow surface and the atmosphere surface. At Dome C (75 • S, 123 • E), we have frequently observed the growth of crystals on the snow surface under calm sunny weather. Here we present the time variations of specific surface area (SSA) and density of these crystals. Using the detailed snow model Crocus, we conclude that the formation of these crystals was very likely due to the nighttime formation of surface hoar crystals and to the daytime formation of sublimation crystals. These latter crystals form by processes similar to those involved in the formation of frost flowers on young sea ice. The formation of these crystals impacts the albedo, mass and energy budget of the Antarctic plateau. In particular, the SSA variations of the surface layer can induce an instantaneous forcing at the snow surface up to −10 W m −2 at noon, resulting in a surface temperature drop of 0.45 K. This result confirms that snow SSA is a crucial variable to consider in the energy budget and climate of snow-covered surfaces.

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Characteristics of the near‐surface atmosphere over the Ross Ice Shelf, Antarctica

2016

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Two years of data from a 30 m instrumented tower are used to characterize the near-surface atmospheric state over the Ross Ice Shelf, Antarctica. Stable stratification dominates the surface layer at this site, occurring 83% of the time. The strongest inversions occur for wind speeds less than 4 m s À1 and the inversion strength decreases rapidly as wind speed increases above 4 m s À1 . In summer unstable stratification occurs 50% of the time and unstable conditions are observed in every season. A novel aspect of this work is the use of an artificial neural network pattern identification technique, known as self-organizing maps, to objectively identify characteristic potential temperature profiles that span the range of profiles present in the 2 year study period. The self-organizing map clustering technique allows the more than 100,000 observed potential temperature profiles to be represented by just 30 patterns. The pattern-averaged winds show distinct and physically consistent relationships with the potential temperature profiles. The strongest winds occur for the nearly well mixed but slightly stable patterns and the weakest winds occur for the strongest inversion patterns. The weakest wind shear over the depth of the tower occurs for slightly unstable profiles and the largest wind shear occurs for moderately strong inversions. Pattern-averaged log wind profiles are consistent with theoretical expectations. The log wind profiles exhibit a kinked profile for the strongest inversion cases indicative of decoupling of the winds between the bottom and top of the tower. PUBLICATIONS

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Meteorological atmospheric boundary layer measurements and ECMWF analyses during summer at Dome C, Antarctica

Cited by 86 publications

References 37 publications

Using MODIS land surface temperatures and the Crocus snow model to understand the warm bias of ERA-Interim reanalyses at the surface in Antarctica

Using MODIS land surface temperatures and the Crocus snow model to understand the warm bias of ERA-Interim reanalyses at the surface in Antarctica

The growth of sublimation crystals and surface hoar on the Antarctic plateau

Characteristics of the near‐surface atmosphere over the Ross Ice Shelf, Antarctica

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