A study of the dynamics of the equatorial lower stratosphere by use of ultra‐long‐duration balloons: 1. Planetary scales

Vial, F.; Hertzog, Albert; Mechoso, Carlos R.; Basdevant, C.; Cocquerez, Philippe; Dubourg, Vincent; Nouel, F.

doi:10.1029/2000jd000241

Cited by 27 publications

(30 citation statements)

References 26 publications

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“…The bias is also seen in comparisons with GPS-derived temperatures (Gobiet et al, 2005). Vial et al (2001) found a warm bias of about 0.5 K around 1 September 1998, at 60 hPa (20 km). This does not disagree with the present results since the flights they studied were closer to the equator.…”

Section: Temperatures and Windsmentioning

confidence: 68%

“…From three long-duration super-pressure balloon flights launched at 0.1 • N from Ecuador, Vial et al (2001) studied the accuracy of both ECMWF temperatures and winds at around 60 hPa from late August to mid October 1998 in the equatorial region. They found a warm bias of the ECMWF temperatures of about 0.5 K compared with longduration balloons.…”

Section: Introductionmentioning

confidence: 99%

“…The horizontal balloon velocity is a very good approximation of the horizontal air velocity (Vial et al, 2001). In order to mimic the balloon behaviour in the vertical, isopycnic trajectories were computed for BP, while MIR trajectories were obtained by forcing the pressure to the observed balloon pressure.…”

Section: Trajectoriesmentioning

confidence: 99%

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Accuracy of analyzed temperatures, winds and trajectories in the Southern Hemisphere tropical and midlatitude stratosphere as compared to long-duration balloon flights

et al. 2006

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Abstract. Eight super-pressure balloons floating at constant level between 50 and 80 hPa and three Infra-Red Montgolfier balloons of variable altitude (15 hPa daytime, 40-80 hPa night time) have been launched at 22 • S from Brazil in February-May 2004 in the frame of the HIBISCUS project. The flights lasted for 7 to 79 days residing mainly in the tropics, but some of them passed the tropical barrier and went to southern midlatitudes. Compared to the balloon measurements just above the tropical tropopause the ECMWF operational temperatures show a systematic cold bias of 0.9 K and the easterly zonal winds are too strong by 0.7 m/s. This bias in the zonal wind adds to the ECMWF trajectory errors, but they still are relatively small with e.g. about an error of 700 km after 5 days. The NCEP/NCAR reanalysis trajectory errors are substantially larger (1300 km after 5 days). In the southern midlatitudes the cold bias is the same, but the zonal wind bias is almost zero. The trajectories are generally more accurate than in the tropics, but for one balloon a lot of the calculated trajectories end up on the wrong side of the tropical barrier and this leads to large trajectory errors.

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Section: Temperatures and Windsmentioning

confidence: 68%

Section: Introductionmentioning

confidence: 99%

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Accuracy of analyzed temperatures, winds and trajectories in the Southern Hemisphere tropical and midlatitude stratosphere as compared to long-duration balloon flights

et al. 2006

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“…SPB are constant density (isopycnic) balloons flying between 58 hPa (19.9 km) and 65 hPa (19.2 km) depending on the weight of the payload. The SPB flights are described in detail by Vial et al (2001) and Hertzog and Vial (2001). Following scientific objectives, balloon capacity and evolution of technology, various payloads are often flown together: always a Samba or Inmarsat service payload of CNES for controlling the flight (cut down if below a prescribed altitude), coupled or not with H 2 O or Rumba scientific payloads of LMD (Laboratoire de Météorologie Dynamique) or the SAOZ of Service d'Aéronomie.…”

Section: Datamentioning

confidence: 99%

“…7 are shown trajectories for three representative, but (for clarity) fairly short flights. The top panel shows the 19980907 flight path at the equator which, as the other two 1998 flights, also at the equator (trajectories not shown), exhibits meridional displacements likely caused by Rossby-gravity waves (see Vial et al (2001) and Hertzog and Vial (2001) For each trajectory, the spherical distance between the observed and calculated trajectories was calculated as a function of time since the trajectory start point. For each of the 18 flights for which trajectory comparisons were carried out, the average distance as a function of time is plotted in Fig.…”

Section: Trajectory Comparisonmentioning

confidence: 99%

Evaluation of ECMWF ERA-40 temperature and wind in the lower tropical stratosphere since 1988 from past long-duration balloon measurements

Christensen

Knudsen

Pommereau³

et al. 2007

Atmos. Chem. Phys.

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16 K in 1988-1989, to +0.26 K in 1994-1996 and −0.46 K after 1998, the latter being fully consistent with recent evaluations of ECMWF operational analysis from radio occultation and in situ longduration balloon observations. The amplitude of the bias and its evolution are very similar to the results of a previous evaluation from radiosondes in 1991-2003, suggesting that the origin of the drift of ERA-40 might be mainly due to errors in the series of satellite measurements of MSU, replaced by AMSU in 1998, assimilated in the model.The ERA-40 zonal wind speed in the lower stratosphere appears slightly overestimated by 0.7-1.0 m/s on average in both the tropics and equatorial region, that is by 5-10% compared to the average 10-20 m/s wind speed. This bias, fully consistent with a recent evaluation of ECMWF operational analysis in 2004, is found constant during the whole 1988-2001 period, suggesting a shortfall in the variabililty of ERA-40 horizontal winds in the lower stratosphere in the tropics and the equatorial region. Finally calculated trajectories using ERA-40, frequently used for analysing field observaCorrespondence to: T. Christensen (tic@dmi.dk) tions, are found in error compared to that of the balloons by ±500 km after 5 days and ±1000 km after 10 days.

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Kelvin and Rossby‐gravity wave packets in the lower stratosphere of some high‐top CMIP5 models

et al. 2014

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We analyze the stratospheric Kelvin and Rossby‐gravity wave packets with periods of a few days in nine high‐top (i.e., with stratosphere) models of the fifth Coupled Model Intercomparison Project (CMIP5). These models simulate realistic aspects of these waves and represent them better than the tropospheric convectively coupled waves analyzed in previous studies. There is nevertheless a large spread among the models, and those with a quasi‐biennial oscillation (QBO) produce larger amplitude waves than the models without a QBO. For the Rossby‐gravity waves this is explained by the fact that models without a QBO never have positive zonal mean zonal winds in the lower stratosphere, a situation that is favorable to the propagation of Rossby‐gravity waves. For the Kelvin waves, larger amplitudes in the presence of a QBO is counter intuitive because Kelvin waves are expected to have larger amplitude when the zonal mean zonal wind is negative, and this is always satisfied in models without a QBO. We attribute the larger amplitude to the fact that models tuned to have a QBO require finer vertical resolution in the stratosphere. We also find that models with large precipitation variability tend to produce larger amplitude waves. However, the effect is not as pronounced as was found in previous studies. In fact, even models with weak precipitation variability still have quite realistic stratospheric waves, indicating either that (i) other sources can be significant or that (ii) the dynamical filtering mitigates the differences in the sources between models.

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A study of the dynamics of the equatorial lower stratosphere by use of ultra‐long‐duration balloons: 1. Planetary scales

Cited by 27 publications

References 26 publications

Accuracy of analyzed temperatures, winds and trajectories in the Southern Hemisphere tropical and midlatitude stratosphere as compared to long-duration balloon flights

Accuracy of analyzed temperatures, winds and trajectories in the Southern Hemisphere tropical and midlatitude stratosphere as compared to long-duration balloon flights

Evaluation of ECMWF ERA-40 temperature and wind in the lower tropical stratosphere since 1988 from past long-duration balloon measurements

Kelvin and Rossby‐gravity wave packets in the lower stratosphere of some high‐top CMIP5 models

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