Balloon Data Research Articles

Atmospheric boundary layer development over a narrow coastal plain during onshore flow

A study of the structure of the daytime atmospheric boundary layer during onshore flow over a narrow coastal plain is presented. The main emphasis of the study is on the nature and causes of heating and cooling observed in the boundary layer temperature profiles. Measurements included vertical temperature profiles above at least two sites derived from radiosondes and aircraft, as well as surface estimates of radiative and sensible heat fluxes. Surface meteorological and pilot balloon data were also available, providing further evidence of short-term changes in atmospheric boundary layer structure. The Manawatu case was representative of autumnal anticyclonic conditions with weak pressure gradients, and illustrated typical diurnal development of a convective boundary layer over a coastal plain bordered by mountain ranges, with a transition from a stable nocturnal situation to a well-mixed profile in the afternoon. The profiles show surface input of heat propagating upwards through the boundary layer during the day, as well as entrainment of heat at the top associated with shear induced turbulence and/or penetrative convection. Applying a one-dimensional model, estimates of boundary layer heat budget components were obtained for four time periods during the day. Later periods were affected by cumulus cloud development at the top of the boundary layer, resulting in significant changes in individual components. Input of sensible heat from the surface decreased, while the addition of heat to the boundary layer from both cloud condensation and advection increased.

A comparative study of prognostic MM5 meteorological modeling with aircraft, wind profiler, lidar, tethered balloon and RASS data over Philadelphia during a 1999 summer episode

This study presents a comparative evaluation of the prognostic meteorological Fifth Generation NCAR Pennsylvania State University Mesoscale Model (MM5) using data from the Northeast Oxidant and Particle Study (NE-OPS) research program collected over Philadelphia, PA during a summer episode in 1999. A set of model simulations utilizing a nested grid of 36 km, 12 km and 4 km horizontal resolutions with 21 layers in the vertical direction was performed for a period of 101 h from July 15, 1999; 12 UTC to July 19, 1999; 17 UTC. The model predictions obtained with 4 km horizontal grid resolution were compared with the NE-OPS observations. Comparisons of model temperature with aircraft data revealed that the model exhibited slight underestimation as noted by previous investigators. Comparisons of model temperature with aircraft and tethered balloon data indicate that the mean absolute error varied up to 1.5 °C. The comparisons of model relative humidity with aircraft and tethered balloon indicate that the mean relative error varied from −11% to −22% for the tethered balloon and from −5% to −30% for the aircraft data. The mean relative error for water vapor mixing ratio with respect to the lidar data exhibited a negative bias consistent with the humidity bias corresponding to aircraft and tethered balloon data. The tendency of MM5 to produce estimates of very low wind speeds, especially in the early-mid afternoon hours, as noted by earlier investigators, is seen in this study also. It is indeed true that the initial fields as well as the fields utilized in the data assimilation also contribute to some of the differences between the model and observations. Studies such as these which compare the grid averaged mean state variables with observations have inherent difficulties. Despite the above limitations, the results of the present study broadly conform to the general traits of MM5 as noted by earlier investigators.

Blocking, descent and gravity waves: Observations and modelling of a MAP northerly föhn event

AbstractA northerly föhn event observed during the special observational period of the Mesoscale Alpine Programme is investigated based on observational analysis and numerical modelling. The focus of this study includes three dynamical processes associated with mountain perturbations and their interactions, namely, windward flow blocking, descent and warming on the lee side, and mountain waves. Observations indicate the presence of a deep weak‐flow layer underneath a stable layer, associated with Alpine‐scale blocking. Satellite imagery reveals a föhninduced cloud‐free area to the south of the Alps, which is consistent with flow descent diagnosed from radiosondes and constant‐volume balloons. Moderate‐amplitude stationary waves were observed by research aircraft over the major Alpine peaks. Satellite images and balloon data indicate the presence of stationary trapped‐wave patterns located to the north of the Alpine massif.Satisfactory agreement is found between observations and a real‐data COAMPS simulation nested to 1 km resolution. COAMPS indicates the presence of trapped waves associated with a sharp decrease of Scorer parameter above a stable layer in the mid‐troposphere. Underneath the stable layer, moist low‐level flow is blocked to the north of the Alps. The warm air in the stable layer descends in the lee and recovers its altitude over a relatively short horizontal distance through a hydraulic jump.Blocking reduces the effective mountain and hence significantly reduces mountain drag. A simple empirical formula for estimation of the effective mountain height, he, is derived based on numerical simulations. The formula states he/hc=√h/hc, where h is the real mountain height and hc is the critical mountain height to have flow stagnation. Copyright © 2005 Royal Meteorological Society.

Astronomical site ranking based on tropospheric wind statistics

High-altitude wind speeds have been adopted as a parameter for astronomical site selection based on the relationship found at the Paranal and Cerro Pachón sites between the average velocity of the turbulence (V0) and winds at the 200-mbar pressure level (V200). Although this relationship has not been checked at any other site in the world and a connection between image quality and V200 has not been proven anywhere, high-altitude wind speed (V200) is a parameter for checking the suitability of sites for adaptive optics and surveying potential sites for extremely large telescopes. We present comprehensive and reliable statistics of high-altitude wind speeds and the tropospheric flows at the location of five important astronomical observatories. We have used the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis data base to collect wind data at nine tropospheric pressure levels for the five selected sites. For comparison and validation of the data from the climate diagnostic model, we have also obtained wind profiles from radiosonde stations. The degrees of correlation found indicate a high level of significance between NCEP/NCAR Reanalysis and balloon data bases, pointing to NCEP/NCAR Reanalysis as a useful data base for site characterization. Statistical analysis exclusively of high-altitude winds points to La Palma as the most suitable site for adaptive optics, with a mean value of 22.13 m s−1 at the 200-mbar pressure level. La Silla is at the bottom of the ranking, with the largest average value 200 mbar wind speed (33.35 m s−1). We have found a clear annual periodicity of high-altitude winds for the five sites under study. We have also explored the connection of high- to low-altitude atmospheric winds as a first approach of the linear relationship between the average velocity of the turbulence and high-altitude winds. We may conclude that high- and low-altitude winds show good linear relationships at the five selected sites. The highest correlation coefficients correspond to Paranal and San Pedro Mártir, while La Palma and La Silla show similar high- to low-altitude wind connection. Mauna Kea shows the smallest degree of correlation, which suggests a weaker linear relationship. Our results support the idea of high-altitude winds as a parameter for ranking astronomical sites in terms of their suitability for adaptive optics, although we have no evidence for adopting the same linear coefficient at different sites. The final value of this linear coefficient at a particular site could drastically change the interpretation of high-altitude wind speeds as a direct parameter for site characterization.

Small-Scale Mixing, Large-Scale Advection, and Stratospheric Tracer Distributions

Abstract The vertical mixing of tracers in the stratosphere is mainly due to patches of three-dimensional turbulence, which are highly intermittent in time and space. A simple heuristic model of this form of mixing is developed and employed to examine the effect of small-scale mixing on passive stratospheric tracers. The model is based on random-walk ideas, and it leads to an analog of the usual advection–diffusion equation in which the diffusion operator is replaced by a convolution operator taking the intermittency of the mixing into account. In its simplest form, this operator is defined by two parameters; these are estimated from midlatitude lower-stratospheric balloon data using a stochastic model of turbulent patches. The behavior of tracer distributions in some idealized flows shows how intermittency makes mixing less effective in damping the small-scale tracer fluctuations that arise through differential advection. This has consequences for stratospheric tracer distributions, which are demonstrated using numerical simulations based on observed stratospheric winds. Specifically, the new model of mixing leads to a horizontal tracer spectrum that is shallower, and closer to a k−2 power law, than the spectrum obtained with a diffusive parameterization of mixing. The horizontal scale below which intermittent mixing differs significantly from diffusion is estimated to be 15 km or so; remarkably, this coincides with the dissipative scale below which dissipation by small-scale mixing is crucial for tracer evolution.

The MaCWAVE/MIDAS rocket and ground‐based measurements of polar summer dynamics: Overview and mean state structure

The MaCWAVE/MIDAS collaborative rocket and ground‐based measurement programs were performed at the Andøya Rocket Range and the nearby ALOMAR observatory in northern Norway during July 2002. The summer component of the MaCWAVE (Mountain and Convective Waves Ascending Vertically) program was focused on gravity wave propagation, instability, and wave‐wave and wave‐mean flow interaction dynamics contributing to summer mesopause structure and variability. The MIDAS (Middle Atmosphere Dynamics and Structure) program concentrated on small‐scale dynamical and microphysical processes near the summer mesopause. Our merged program yielded a comprehensive data set comprising two ∼12‐hour rocket salvoes, including 25 MET rockets and 5 sounding rockets, ground‐based lidar, radar, and balloon data, and coordinated overpasses of the TIMED satellite. This paper describes the measurement program and rationale, the mean state observed during the rocket salvoes, and evidence that the mean state structure during 2002 differed in important respects from previous years.

Large magnetic anomalies over Russia revealed by balloon data

Large magnetic anomalies over Russia revealed by balloon data

Observations of transient luminous events (TLEs) associated with negative cloud to ground (−CG) lightning strokes

A balloon campaign was conducted in summer, 1999, to measure the stratospheric electromagnetic fields associated with sprites. Ground observations for detection of sprites included low light level TV (LLTV) observations from three sites. Flight 1 flew from Palestine, Texas at 01:14:31 UTC to 09:45:00 UTC on 07/06/1999. Flight 3 of the campaign flew from Ottumwa, Iowa at 00:39:32 UTC to 11:12:00 UTC on 08/21/99. During flight 3, 26 sprite halos associated with positive cloud‐to‐ground (+CG) strokes and 17 −CG sprite halos were observed. Of these, 22 +CG and 12 −CG sprite halos were observed by the ground observatories. Seven of the +CG and all 17 −CG halos were not followed by sprites. Next the balloon data were examined during and after the times of the recorded NLDN strokes during 4.1 hours of data. An additional 88 −CG TLEs were found in the flight 3 data and 56 TLEs (7 +CG, 49 −CG) were found in the flight 1 data. It appears that −CG TLEs, mostly spriteless halos, occurred 5–7 times more often than the +CG TLEs. The halo appears to be a fundamental mesospheric response to lightning.

Statistics and analysis of high-altitude wind above the Canary Islands observatories

High-altitude wind has been recently proposed as an important parameter to be taken into account for astronomical site selection. We present here comprehensive and reliable statistics for wind speeds at the 200 mbar (v200 hereafter) pressure level (approximately 12 km above the Canary Islands) based on long-term climate diagnostics archive and balloon data. The results presented in this paper demonstrate the remarkably good behaviour of the high-altitude wind above the Canarian archipelago, with low mean values of v200 (22.12 m s−1 above the Roque de los Muchachos Observatory, hereafter ORM) and provide independent confirmation of the potential of the ORM and the Teide Observatory (OT) for adaptive optics. A comparison of v200 values from a climatological data base and in situ measurements with radiosondes launched from Santa Cruz de Tenerife reveals an excellent level of agreement, which lends support to the claim that climate diagnostic measurements provide a useful tool for astronomical site assessment, although a rigorous control of data quality, analysis and cross comparison needs to be performed before the method becomes extensively used. Moreover, the correlation of the results for La Palma and Tenerife confirms the homogeneity of the Canarian sky at the tropopause level. The analysis of frequency and variability of v200 led us to propose a seasonal periodicity of v200.

Secondary proton flux induced by cosmic ray interactions with the atmosphere

The atmospheric secondary antiproton flux is studied for detection altitudes extending from sea level up to about three earth radii, by means of a three-dimensional Monte Carlo simulation, successfully applied previously to other satellite and balloon data. The calculated antiproton flux at mountain altitude is found to be in fair agreement with the recent BESS measurements. The flux obtained at balloon altitude is also in agreement with calculations performed in previous studies and used for the analysis of balloon data. The flux at sea level is found to be significant. The antineutron flux is also evaluated. The antiproton flux is prospectively explored up to around $2\ifmmode\times\else\texttimes\fi{}{10}^{4}\mathrm{km}$ from the Earth. The results are discussed in the context of the forthcoming measurements by large acceptance experiments.

Secondary antiproton flux induced by cosmic ray interactions with the atmosphere

The atmospheric secondary antiproton flux is studied for detection altitudes extending from sea level up to about three earth radii, by means of a three-dimensional Monte Carlo simulation, successfully applied previously to other satellite and balloon data. The calculated antiproton flux at mountain altitude is found to be in fair agreement with the recent BESS measurements. The flux obtained at balloon altitude is also in agreement with calculations performed in previous studies and used for the analysis of balloon data. The flux at sea level is found to be significant. The antineutron flux is also evaluated. The antiproton flux is prospectively explored up to around $2\ifmmode\times\else\texttimes\fi{}{10}^{4}\mathrm{km}$ from the Earth. The results are discussed in the context of the forthcoming measurements by large acceptance experiments.

A comparison study of RAMS simulations with aircraft, wind profiler, lidar, tethered balloon and RASS data over Philadelphia during a 1999 summer episode

Abstract This study presents comparisons of Colorado State University's prognostic mesoscale Regional Atmospheric Modeling System (RAMS 4.3) results with observational data obtained from aircraft, wind profiler, lidar, tethered balloon and RASS during the Northeast Oxidant and Particle Study (NE-OPS) field program at Philadelphia, PA during a summer episode in 1999. Model simulations were performed for the 15–20 July 1999 period. The comparison of model-predicted temperatures with aircraft and tethered balloon data revealed that the mean relative error exhibited the same general trend in time for temperature noted by earlier investigators. The comparisons of model relative humidity with aircraft and tethered balloon indicate that the mean relative error varied from −13% to −21%. The mean relative error for water vapor mixing ratio with respect to lidar data exhibited a negative bias consistent with humidity bias corresponding to aircraft and tethered balloon. The largest root mean square (rms) errors obtained from 36 km resolution RAMS results and the regular upper air rawinsonde stations are associated with the relative humidity values. The smallest rms errors for any variable are all associated with the lower atmosphere while the largest rms errors are associated with the upper/mid-tropospheric region. The difficulty in correctly predicting upper level humidity is due to lack of consistency in the upper level moisture observations while the lower rms errors of relative humidity close to surface are due to increased availability of moisture data at surface. The results of the present study, by utilizing a variety of diverse observational platforms, broadly confirm the general traits of RAMS performance noted by earlier investigators.

Vertical profiles of O3, NO2, NOx, VOC, and meteorological parameters during the Berlin Ozone Experiment (BERLIOZ) campaign

During the intensive observational periods of the BERLIOZ campaign (20 and 21 July 1998 and 3 August 1998), vertical profiles from 0 to 800 m above ground of O3, NO2, NOx, selected VOC, and meteorological parameters were measured by means of a comprehensive tethered balloon system at Papstthum, a rural site 50 north west of the city of Berlin. Every 2 hours a complete profile was obtained. The VOC were collected on charcoal tubes simultaneously at four different heights over time intervals of 3 hours. The measurement systems participated at the quality assurance measures of the BERLIOZ campaign and fully complied with the data quality objectives. The balloon data provide important information on the vertical gradients of the trace gases at Pabstthum and clearly identify the development of the boundary layer in the course of the day. This information is important for the interpretation of the radical measurements discussed in the accompanying publications. They also give insight in the vertical extent of air masses of different chemical regimes and their temporal evolution. During the morning hours of 20 July the evolution of the city plume passing the measurement site with a vertical extension of 800 m could be documented. Owing to degradation by the reaction with NO a reduced O3 concentration level was observed within the plume in the morning hours of 20 July. The highest peak concentrations of the campaign observed on ground level in the morning of 21 July could not be attributed to the Berlin city plume.

A Large-Eddy Simulation Study of the Convective Boundary Layer over Philadelphia during the 1999 Summer NE-OPS Campaign

This study presents a large-eddy simulation (LES) study of the convective boundary layer on August 1, 1999 over Philadelphia, PA during a summer ozone episode. The study is an evaluation of the Colorado State University's Regional Atmospheric Modeling System Version 4.3 (RAMS4.3) with the LES option using Northeast Oxidant and Particulate Study (NE-OPS) data. Simulations were performed with different imposed sensible heat fluxes at the ground surface. The model was initialized with the atmospheric sounding data collected at Philadelphia at 1230 UTC and model integrations continued till 2130 UTC. The resulting mean profiles of temperature and humidity obtained from the LES model were compared with atmospheric soundings, tethered balloon and aircraft data collected during the NE-OPS 1999 field campaign. Also the model-derived vertical profiles of virtual temperature were compared with NE-OPS Radio Acoustic Sounder System (RASS) data while the humidity profiles were compared with NE-OPS lidar data. The comparison of the radiosonde data with the LES model predictions suggests that the growth of the mixing layer is reasonably well simulated by the model. Overall, the agreement of temperature predictions of the LES model with the radiosonde observations is good. The model appears to underestimate humidity values for the case of higher imposed sensible heat flux. However, the humidity values in the mixing layer agree quite well with radiosonde observations for the case of lower imposed sensible heat flux. The model-predicted temperature and humidity profiles are in reasonable agreement with the tethered balloon data except for some small overestimation of temperature at lower layers and some underestimation of humidity values. However, the humidity profiles as simulated by the model agree quite well with the tethered balloon data for the case of lower imposed sensible heat flux. The model-predicted virtual temperature profile is also in better agreement with RASS data for the case of lower imposed sensible heat flux. The model-predicted temperature profile further agrees quite well with aircraft data for the case of lower imposed heat flux. However, the relative humidity values predicted by the model are lower compared with the aircraft data. The model-predicted humidity profiles are only in partial agreement with the lidar data. The results of this study suggest that the explicitly resolved energetic eddies seem to provide the correct forcing necessary to produce good agreement with observations for the case of an imposed sensible heat flux of 0.1 K m s−1 at the surface.

Validation of ILAS v5.2 data with FIRS‐2 balloon observations

Comparisons of remote sensing stratospheric mixing ratio profiles for O3, H2O, N2O, HNO3, and NO2 are shown between data (version 5.2) obtained by the Improved Limb Atmospheric Spectrometer (ILAS) on board the Japanese Advanced Earth Observing Satellite (ADEOS) and the Smithsonian Astrophysical Observatory far‐infrared spectrometer (FIRS)‐2 balloon‐borne spectrometer from a flight on 30 April 1997 originating in Fairbanks, Alaska. Submillimeter wave remote sensing and UV in situ observations of mixing ratios of O3 from Jet Propulsion Laboratory (JPL) instruments obtained on board the same balloon gondola are also used for comparison with ILAS mixing ratios of O3. The remote sensing balloon observations occurred roughly 5° latitude, and the in situ 2° latitude, north of the nearest ILAS observations and were taken between 0700 and 1300 local solar time (LST), while the ILAS data were taken at the previous local sunset (near 2100 LST). Back trajectories from the locations and times of balloon data sets to the prior local sunset were within 2° latitude and 10° longitude of the nearest ILAS occultation; the validation therefore effectively occurred in very nearly the same air mass as was observed with ILAS, and well within a 1‐day time interval. The mixing ratio profiles of all of the compared molecules (O3, HNO3, N2O, H2O, and NO2) agree to within the combined uncertainties with only minor systematic offsets.

Air mass motion, temperature, and humidity over the Arabian Sea and western Indian Ocean during the INDOEX intensive phase, as obtained from a set of superpressure drifting balloons

During the Indian Ocean Experiment (INDOEX) Intensive Field Phase, 17 superpressure balloons drifting at lower tropospheric levels were launched from Goa to sample the motion and meteorological characteristics of polluted air masses originating from the Indian subcontinent. The mass flow, as expected, is attracted to the Intertropical Convergence Zone (ITCZ), which is reached in about 7 days. Successive trajectories show evidence of shifts in the flow regime, consistent with Meteosat‐5 imagery and illustrative of the Madden–Julian oscillation. Balloons also show evidence of coastal anticyclonic circulations off the western coast of India, linked to both the orography of the Ghâts and the diurnal coastal wind mesoscale wind systems. These mesoscale circulations may be important in the transport of anthropogenic or mineral pollutants across the coast. The meteorological data gathered on board the balloons were systematically compared with European Centre for Medium‐Range Weather Forecasts (ECMWF) analyses interpolated in time and space at the balloons' successive locations every half‐hour. The agreement is generally good in terms of wind velocities, temperature, and humidity. However, above the marine boundary layer, balloon data seem to indicate a cold bias of analyzed temperatures and a northeasterly bias of horizontal winds. The underestimation of variability in the analyzed winds can be partly explained by mesh size smoothing in the analysis system.

Comparison of POAM III ozone measurements with correlative aircraft and balloon data during SOLVE

The Polar Ozone and Aerosol Measurement (POAM) III instrument operated continuously during the Stratospheric Aerosol and Gas Experiment (SAGE) III Ozone Loss and Validation Experiment (SOLVE) mission, making approximately 1400 ozone profile measurements at high latitudes both inside and outside the Arctic polar vortex. The wealth of ozone measurements obtained from a variety of instruments and platforms during SOLVE provided a unique opportunity to compare correlative measurements with the POAM III data set. In this paper, we validate the POAM III version 3.0 ozone against measurements from seven different instruments that operated as part of the combined SOLVE/THESEO 2000 campaign. These include the airborne UV Differential Absorption Lidar (UV DIAL) and the Airborne Raman Ozone and Temperature Lidar (AROTEL) instruments on the DC‐8, the dual‐beam UV‐Absorption Ozone Photometer on the ER‐2, the MkIV Interferometer balloon instrument, the Laboratoire de Physique Molèculaire et Applications and Differential Optical Absorption Spectroscopy (LPMA/DOAS) balloon gondola, the JPL in situ ozone instrument on the Observations of the Middle Stratosphere (OMS) balloon platform, and the Système D'Analyze par Observations Zénithales (SAOZ) balloon sonde. The resulting comparisons show a remarkable degree of consistency despite the very different measurement techniques inherent in the data sets and thus provide a strong validation of the POAM III version 3.0 ozone. This is particularly true in the primary 14–30 km region, where there are significant overlaps with all seven instruments. At these altitudes, POAM III agrees with all the data sets to within 7–10% with no detectable bias. The observed differences are within the combined errors of POAM III and the correlative measurements. Above 30 km, only a handful of SOLVE correlative measurements exist and the comparisons are highly variable. Therefore, the results are inconclusive. Below 14 km, the SOLVE comparisons also show a large amount of scatter and it is difficult to evaluate their consistency, although the number of correlative measurements is large. The UV DIAL, DOAS, and JPL/OMS comparisons show differences of up to 15% but no consistent bias. The ER‐2, MkIV, and SAOZ comparisons, on the other hand, indicate a high POAM bias of 10–20% at the lower altitudes. In general, the SOLVE validation results presented here are consistent with the validation of the POAM III version 3.0 ozone using SAGE II and Halogen Occultation Experiment (HALOE) satellite data and in situ electrochemical cell (ECC) ozonesonde data.

Comparison of simulated longitudinal profiles of hadronic air showers with MASS2 balloon data

The KASKADE and CORSIKA air shower generators are compared to the data collected by MASS2 balloon experiment in 1991. The test of longitudinal profile for proton, helium and muon flux production provide good constraints on these air shower generators. KASKADE and CORSIKA especially with the new simulator UrQMD for low energies are found to fit these data well. This study is limited to a comparison of longitudinal profiles and therefore does not provide constraints on the overall shower development.

Seasonal variation of water vapor in the lower stratosphere observed in Halogen Occultation Experiment data

The seasonal cycle of water vapor in the lower stratosphere is studied based on Halogen Occultation Experiment (HALOE) satellite observations spanning 1991–2000. The seasonal cycle highlights fast, quasi‐horizontal transport between tropics and midlatitudes in the lowermost stratosphere (near isentropic levels ∼380–420 K), in addition to vertical propagation above the equator (the tropical “tape recorder”). The rapid isentropic transport out of the tropics produces a layer of relatively dry air over most of the globe throughout the year, and the seasonal cycle in midlatitudes of both hemispheres (and over the Arctic pole) follows that in the tropics. Additionally, the Northern Hemisphere summer monsoon has a dominant influence on hemispheric‐scale constituent transport. Longitudinal structures in tropical water vapor and ozone identify regions of strong coupling to the troposphere; an intriguing result is that the solstice minima in water vapor and ozone are spatial separated from maximum convection and coldest tropical temperatures. Detailed comparisons with tropical aircraft measurements and the long record of balloon data from Boulder, Colorado, demonstrate the overall high quality of HALOE water vapor data.

The use of long‐duration balloon data to determine the accuracy of stratospheric analyses and forecasts

Wind velocity data from seven high‐altitude long‐duration balloon flights are compared with stratospheric analyses and forecasts produced by the U.K. Meteorological Office (UKMO) and the Data Assimilation Office (DAO). The results suggest that biases in both the UKMO and DAO analyses arise from the displacement of the polar night jet to higher latitudes in the winter and from a cold bias in the stratosphere in the summer. At high latitudes the DAO analysis performs better than the UKMO analyses, with the use of a rotated pole in the DAO system the most likely cause of the improvement. The trajectories for each flight were simulated using UKMO and DAO 5‐day forecasts and by using simple persistence techniques. It is shown that UKMO and DAO forecasts based on better initial analyses produced trajectories that were more accurate. On the 1‐day forecast timescale there is little difference between the techniques, but on the 2‐ to 5‐day range the trajectories based on forecasts generally performed significantly better than persistence. The results demonstrate the usefulness of stratospheric balloon data for validating both analyses and forecasts.