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Beljaars, Paul R

doi:10.1093/jaoac/78.1.243

Cited by 2 publications

(5 citation statements)

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“…There is no parametrization of moistening by methane oxidation. The set of major parametrizations is completed by a boundary-layer scheme (Beljaars 1995) and a land-surface scheme (Viterbo and Beljaars 1995).…”

Section: The Ecmwf Forecasting Systemmentioning

confidence: 99%

“…Initial winds and temperatures above 40 hPa for the 50-level version were taken from the UARS analyses produced routinely by the UK Meteorological Office (Swinbank and O'Neill 1994). Sea surface temperatures were set periodically to the evolving NCEP analyses for the period 1995(Reynolds and Smith 1994. The 50-level simulation was subsequently extended for a further six years as it was found to be producing a realistic-looking QBO.…”

Section: Stratospheric Humidity In Multi-year Simulationsmentioning

confidence: 99%

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Stratospheric water vapour and tropical tropopause temperatures in ECMWF analyses and multi-year simulations

SIMMONS¹,

UNTCH²,

JAKOB³

et al. 1999

Quarterly Journal of the Royal Meteorological Society

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Stratospheric humidity analyses produced operationally by the European Centre for Medium-Range Weather Forecasts (ECMWF) are discussed for the period since late January 1996 when the practice of resetting the upperlevel specific humidity to a fixed value at each analysis time was abandoned. Near-tropopause analyses are in reasonable overall agreement with independent observations. Very low humidities occur in conjunction with deep convection and a particularly cold tropopause over the equatorial western Pacific during the northern winter. Drying occurs also in the cold core of the Antarctic polar-night vortex. The lower stratosphere is moistened in the outer tropics and subtropics in summer and autumn, predominantly in the northern hemisphere. Changes associated with the latest occurrence of El Niiio are illustrated.Analysed temperatures near the tropical tropopause are generally in good agreement with corresponding radiosonde measurements, with standard-level biases of the order of 0.5 degC or less. The past two years are the coldest by about 1 degC in a series of tropical mean 100 hPa analyses extending back to 1979. A cooling trend of about 0.6 degC per decade is seen in the global means of the 100 hPa analyses.Moisture is spread zonally and upward from the tropical tropopause as the data assimilation proceeds, but the rate of upward transfer is much faster than observed. Substantial lateral mixing can occur within the stratosphere over the course of a season. Moistening at middle and high latitudes due to mixing with more humid tropospheric air is confined, realistically, to a shallow layer at the base of the stratosphere.The rate of upward transfer of tropical stratospheric moisture is much more realistic in a multi-year simulation using a version of the model that has finer stratospheric resolution than the version used for the operational data assimilation. Temperatures at the tropical tropopause and in the Antarctic polar night are accurately simulated, apart from excessive persistence of cold south-polar temperatures in late winter and early spring. The latter is conducive to drying the model stratosphere; lack of a parametrization of moistening due to methane oxidation is an obvious deficiency in this regard.

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Section: The Ecmwf Forecasting Systemmentioning

confidence: 99%

Section: Stratospheric Humidity In Multi-year Simulationsmentioning

confidence: 99%

Stratospheric water vapour and tropical tropopause temperatures in ECMWF analyses and multi-year simulations

SIMMONS¹,

UNTCH²,

JAKOB³

et al. 1999

Quarterly Journal of the Royal Meteorological Society

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“…During the last decade, it has been recognized that convective boundary layers (CBLs) are affected by large eddies. These eddies produce essential convergence/ divergence ow patterns in the surface layer, even in the absence of a mean wind (Businger et al 1971;Businger 1973;Schumann 1988;Sykes et al 1993;Beljaars 1995;Zilitinkevich et al 1998), resulting in turbulence production. Thus, even in zero mean wind a minimum friction velocity U ¤ could be determined.…”

Section: Introductionmentioning

confidence: 99%

“…In the case of zero mean vector wind, the scalar wind speed equals V gust . The gustiness wind speed has been suggested to be proportional to W ¤ by numerous theoretical schemes (see Schumann 1988;Sykes et al 1993;Beljaars 1995;Zilitinkevich et al 1998):…”

Section: Introductionmentioning

confidence: 99%

“…Their empirical coef cients, wherever these exist, were estimated by tting to available data. Schumann (1988), Sykes et al (1993) and Beljaars (1995) used data from large-eddy simulations (LESs; Schmidt and Schumann 1989;Sykes et al 1993). Zilitinkevich et al (1998) utilized data from eld measurements from the Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE;Fairal et al 1996), the San Clemente Ocean Probing Experiment (SCOPE; Krop i and Clifford 1994) and BOREX-95 (Mikkelsen et al 1996).…”

Section: Introductionmentioning

confidence: 99%

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Considerations on minimum friction velocity

Akylas

Tsakos

Tombrou

et al. 2003

Quart J Royal Meteoro Soc

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SUMMARYThe concept of the minimum friction velocity is studied using three different methods of scalar averaging for the calculation of the stresses. Particular emphasis is given to the extraction of the in uence of a non-zero ambient wind shear observed in eld measurements. Data from three different experimental sites in Athens with high roughness values are analysed in order to provide information concerning the dependence of the dimensionless minimum friction velocity on the dimensionless roughness length. Data from the BOREX-95 experiment have also been re-analysed according to the methodologies presented in this study. The results are compared to the large-eddy simulations that are considered to be a reference study on shear-free convection.

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Liaison Committee

Cited by 2 publications

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Stratospheric water vapour and tropical tropopause temperatures in ECMWF analyses and multi-year simulations

Stratospheric water vapour and tropical tropopause temperatures in ECMWF analyses and multi-year simulations

Considerations on minimum friction velocity

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