Balloon Measurements Research Articles

Balloon measurements of stratospheric ion conductivities over the tropics

Conductivity measurements of negative and positive ions were made from about 20 to 35 km by two identical balloon-borne spherical probes at Hyderabad (17.5°N, 78.6°E), India on 22 April 1989 and 22 December 1990. One balloon was launched at 0158 h IST (Indian Standard Time) which reached its ceiling around 0330 h IST. After that time, it floated for about 3 h, 1.5 h before sunrise and 1.5 h after sunrise. Thus it gave data for both day- and night-time conditions at float altitude. The other balloon was launched at 0535 h IST. It gave data for daytime only. Several interesting results have been obtained at the float altitudes. During the night, in the flight of 22 April 1989 the conductivity values of positive ions were found to be about 1.5 times those of negative ions at the float altitude. During the day, in the flight of 22 April 1989, the positive ion conductivity values were found to increase with the increase of solar elevation angle at around 37.5 km altitude. The negative ion conductivity values, however, did not show any day-night variation. In the flight of 22 December 1990, these features were not seen. Instead, a pocket was found where conductivity values were very high (of the order of 10 −11 mho m −1) at an altitude of about 32.5 km. Also in this flight, the positive ion conductivity was always found to be approximately equal to that of the negative ion conductivity.

Direct Evidence of “Sheets” in the Atmospheric Temperature Field

This paper presents experimental evidence showing the ubiquitous presence in the lower atmosphere (at least up to 25 km) of very strong (positive) temperature gradients within very thin layers. The presence of such “sheets” in the temperature field of the free atmosphere was frequently hypothesized in order to account for the aspect sensitivity of VHF radar measurements. Owing to their high vertical resolution (20 cm) and to the fast-response thermometers used, the in situ balloon measurements discussed in this paper constitute the first direct evidence of their true existence. Statistical study of the properties of the sheets results in the following typical values: thickness 3–20 m, temperature increase 0.2–0.8 K, gradient 30–100 K/km. The sheets are frequently observed in groups, associated with and taking part in regions of high static stability. Local measurements using two pairs of sensors one meter apart indicate that the sheets are not flat and horizontal. Sometimes, clear evidence of ongoing or recent mixing, despite the strong local static stability, can account for such distortions. Observations of the same sheets by two thermometers 65 m apart (vertically) indicate vertical distortions of the sheets up to 10 m and horizontal extensions larger than 100 m. The possible contribution of the observed sheets to the VHF radar vertical reflectivity is estimated and compared with simultaneous reflectivity profiles measured by the PROVENCE radar. Without any adjustment, these profiles compare favorably, both in shape and in level, thus suggesting that the sheets can account for a significant fraction of the VHF radar vertical echoes.

High‐speed civil transport impact: Role of sulfate, nitric acid trihydrate, and ice aerosols studied with a two‐dimensional model including aerosol physics

Recent assessment studies have shown that heterogeneous chemistry could have a significant role on the model‐predicted ozone changes due to gas injection from high‐speed civil transport (HSCT) aircraft. One major limitation of these numerical experiments was the highly simplified scheme adopted for the aerosol particles and, in particular, the absence of any explicit feedback between the gas phase chemistry included in the models and the total aerosol surface density available for heterogeneous reactions. In this paper we describe a two‐dimensional model covering the whole stratosphere and troposphere which includes photochemical reactions for the sulfur cycle and a microphysical code for sulfuric acid aerosols. Starting from these particles, the same code predicts also the size distribution for nitric acid trihydrate (NAT) and ice aerosols, covering globally a particle radius range between 0.01 μm and about 160 μm. A rather simple scheme is described for nucleation and condensation processes leading to the formation and growth of NAT and ice particles, still using grid point temperature data taken from the zonally averaged climatology of the lower stratosphere. A discussion is made of the HSCT impact on ozone adopting different scenarios for the aerosols. Model results for the aerosol size distribution and for the available surface densities appear reasonable when compared to satellite and balloon measurements and to independent numerical calculations. As pointed out also by previous research work and assessment panels, our calculation shows that the ozone sensitivity to HSCT emissions largely decreases when heterogeneous chemistry is included with respect to a pure gas phase chemistry case. In addition, our results indicate that the ozone sensitivity to HSCT emission decreases even more when NAT and ice aerosols are present: this is a consequence of the aerosol‐induced stratospheric denitrification which makes the residence time of the injected odd nitrogen shorter and the relative weight of the NOx catalytic cycle smaller. Inclusion of the sulfur dioxide feedback with the sulfate aerosol surface does not change significantly the ozone depletion in our model simulation, at least in the pure sulfate case. The additional ozone change due to aircraft injection of SO2 is larger when NAT and ice aerosols are allowed to form, due to the decreased ozone sensitivity to NOx. In this version of the model no direct aircraft emission of particulate has been included as a possible source for additional condensation nuclei.

Lidar observations of atmospheric dynamics in the troposphere and lower stratosphere over Arecibo

A periodic wave structure with a vertical wave length typically 2 km between 14 and 23 km altitudes has been identified in lidar measurements of relative density profiles at 589 nm that were made by the University of Illinois group during the March/April AIDA 1989 campaign effort. The equivalent temperature fluctuations are several degrees in magnitude. Also seen are stratified aerosol layers at altitudes near 25 km with a vertical extent of ∼1 km. Both of these phenomena show a downward phase speed between 1 and 3 cm s−1. The lower periodic structure is believed to be the same phenomenon seen previously in 430‐MHz measurements of winds obtained at Arecibo Observatory. The source of this structure remains uncertain. Cornish and Larsen (1989) and Sato and Woodman (1982a) considered this structure to be a quasi‐inertial long period wave. Hines (1989) proposed instead the identification of this structure with a stationary wave system generated by orographic waves created through the interaction of the subtropical trade winds with the mountainous terrain of Puerto Rico. The higher altitude feature seen in the AIDA lidar observations is believed to be an aerosol layer with a scattering ratio of about 1.15. An alternative explanation is clear air turbulence, but the signature of the 10 K fluctuation deduced from the lidar observations was not found in the San Juan balloon measurement of the temperature profile for the lower stratosphere.

Charged precipitation measurements before the first lightning flash in a thunderstorm

On August 15, 1984, we made balloon measurements of the electric field and of the charge and vertical velocity of precipitation particles in a thunderstorm over Langmuir Laboratory. Substantial quantities of positively charged precipitation, comprising a lower positive charge center, were collected before the storm's first lightning flash. Possible origins of the positive charge are discussed. Negatively charged precipitation and positively charged cloud particles found higher in the cloud seem to have generated electrical energy in the way suggested in the typical precipitation theory of thunderstorm electrification.

Balloon observations of galactic cosmic ray helium before and during a Forbush decrease

The energy spectrum of galactic cosmic ray Helium was measured in two different balloon experiments launched four days apart from Canada: SMILI‐I on 1‐Sept‐1989 and MASS on 5‐Sept‐1989. A slow Forbush decrease began on 4‐Sept‐1989 and had not reached its maximum at the time of the MASS flight. Comparison of the balloon measurements shows a fractional decrease of 0.37 to 0.15 in the Helium flux between 200 and 450 MeV/nucleon (1.2–2.0 GV). The rigidity dependence is analyzed in two models and found to be steeper than previous observations. Interplanetary particle data and ground‐based Neutron Monitor results are consistent with the balloon observations. Probable sources for this Forbush decrease are discussed.

GRIS detections of the 511 keV line from the Galactic center region in 1992

The Gamma Ray Imaging Spectrometer (GRIS) was flown on balloons over Alice Springs, Australia on 1992 April 26 and May 7. A full Galactic center transit (about 12 hr) was achieved on both flights with the instrument working normally. The electron/positron annihilation line was detected on both flights. The line fluxes and line widths were found to be (7.7 +/- 1.2) x 10 exp -4 and (8.9 +/- 1.1) x 10 exp -4 photons/sq cm per sec and 1.3 +/- 0.7 and 3.6 +/- 1.0 keV, respectively. These results are compared to each other and earlier (1988) GRIS results to produce suggestive evidence for source variability. Near-contemporaneous OSSE/CGRO Galactic center observations indicate that the GRIS results cannot be due solely to a single point source like IE 1740.7-2942 within a few degrees of the Galactic center. The GRIS 1992 results represent the first time that successive high-resolution balloon measurements have been achieved on a time scale of days.

Results of the balloon measurements of the stratosphere radiothermal radiation at 5 mm

Original microwave radiometer with double frequency conversion developed for remote thermal sounding of the stratosphere up to 40 km is described. Radiometer operating at the slopes of two oxygen lines with resonant frequencies 57.612 and 61.151 GHz has 6 channels with bands of 3 to 150 MHz and sensitivities of 0.6 to 0.09 K, respectively. Results of two balloon flights (one with nadir microwave sounding and another with sounding at the 15° zenith angle) are presented.

Measurement distortion in aircraft, space shuttle, and balloon observations of atmospheric density and temperature perturbation spectra

Aircraft, space shuttle, and balloon observations are being used to study the density, temperature, and wind structure of the atmosphere. The horizontal and vertical wave number spectra derived from these observations are contaminated by undesired spatial and temporal variations unique to the observational geometries. We use numerical models to quantify this distortion. The results show that distortion is negligible in aircraft and space shuttle measurements of horizontal wave number spectra if the aircraft velocity is ∼100 m/s or larger and the slant angle of the shuttle reentry path is ∼0.5° or less. The distortion in balloon measurements of vertical wave number spectra is negligible provided the ascent velocity is ∼3 m/s or larger and the horizontal wind speed is not more than about 10 times the balloon ascent velocity. This latter condition can be violated during some balloon flights when horizontal winds are strong. In those circumstances the measured spectrum will be larger in magnitude and have a shallower slope than the intrinsic vertical wave number spectrum.

Comparative observations of stratospheric aerosols by ground‐based lidar, balloon‐borne polarimeter, and satellite solar occultation

The analysis of European correlative experiments of the stratospheric aerosol layer is performed for three periods. These independent experiments are lidar measurements obtained at Garmisch‐Partenkirchen, balloon measurements of the reflectance and of the polarization achieved at Aire sur l'Adour with RADIBAL experiment and transmission measurements provided by the SAGE II experiment. Comparisons of the aerosol slant optical thicknesses are performed, and the agreement is generally good. Two different schemes are used to retrieve two parameters of the size distribution from the polarization and from the transmission spectral measurements. The discrepancies that appear in a few cases for the radius comparison are analyzed.

Angiographic risk factors of luminal narrowing after coronary balloon angioplasty using balloon measurements to reflect stretch and elastic recoil at the dilatation site

Because many ongoing clinical restenosis prevention trials are using quantitative angiography to assess whether a drug is capable of reducing the amount of intimal hyperplasia, quantitative angiographic risk factors for angiographic luminal narrowing after balloon angioplasty were determined, including stretch and elastic recoil at the dilatation site. Quantitative analysis was performed on 666 lesions in 575 patients during angioplasty and at 6-month follow-up. Stretch was defined as balloon diameter minus minimal luminal diameter (MLD) before angioplasty/reference diameter, and recoil as balloon diameter minus MLD after angioplasty/reference diameter. Multivariate analysis was used to yield independent risk factors for luminal narrowing at follow-up. Predictors of absolute change in MLD were (1) relative gain at angioplasty (gain in millimeters normalized for reference diameter) and (2) lesion length. To allow risk stratification, logistic regression analysis was applied using the decrease in MLD as a binary outcome variable. A decrease in MLD at follow-up of ≥ 0.72 mm was considered significant. Variables retained in the model were: relative gain > 0.3 mm (rate ratio 2.9), relative gain 0.2 to 0.3 (rate ratio 2.1), stenosis length ≥ 6.8 (rate ratio 1.7), and thrombus after angioplasty (rate ratio 2.6). Although stretch was significantly related to luminal narrowing at univariate analysis, it was not retained in the multivariate models. A large gain in lumen diameter at angioplasty, dilation of long lesions, and angiographically determined thrombus after angioplasty were found to be accompanied by more severe luminal narrowing at follow-up.

A Dispersion Model Evaluation Study for Real-Time Application in Complex Terrain

A few tracer experiments were carried out in autumn 1984 and summer 1985 at the Lago Brasimone site, on the Appennini Mountains approximately 50 km south of Bologna with the purpose assessing the atmospheric dispersion of pollutants under drainage flow conditions. The three-dimensional transport and diffusion model MATHEW/ADPIC (M/A) has been applied to selected tracer and meteorological data with the aim of assessing the model performance under complex terrain and meteorological conditions, and its sensitivity to input data available in real-time applications. Boundary layer input parameters were derived through standard algorithms based on tethersonde and pilot balloon measurements. Model simulations of the most significant tracer experiments have been assessed by means of several evaluation criteria, and the sensitivity to some input data has been investigated. The results show that if a limited spatial uncertainty in the computed concentration pattern is taken into account, M/A provides a good agreement with observed concentrations. The quality of the results is very sensitive to the presence of wind measurements where the deviation of the flow due to the shape of the valley is observed.

Inferring the abundances of ClO and HO2 from Spacelab 3 Atmospheric Trace Molecule Spectroscopy observations

The vertical distributions of the important highly reactive stratospheric species, ClO and HO2, have been inferred from Spacelab 3 (May 1985) Atmospheric Trace Molecule Spectroscopy (ATMOS) measurements of more detectable radical and reservoir species. A simple steady state algebraic expression for ClO, utilizing the observed ClONO2/NO2 abundance ratio, approximates the ClO results of a time‐dependent photochemical model at sunset (30°N). Balloon measurements of ClO and comparisons of time‐dependent photochemical model calculations of ClONO2 and HCl with the corresponding ATMOS profiles suggest that the actual ClO values are less than the time‐dependent model profiles for ClO at sunset and sunrise (47°S). Errors in the current model simulation of the partitioning among the principal free chlorine species (HCl, ClONO2, and ClO) are indicated. However, a comparison of model results with observations of HOCl suggests that the calculated ClO abundance is not a significant overestimate of actual values. A similar methodology is applied to inferring the HO2 distribution, either algebraically using the ATMOS‐measured HO2NO2/NO2 abundance ratio or numerically utilizing the time‐dependent model. The algebraic results agree with the time‐dependent model values to better than a factor of 2 at sunrise. The accuracy of the time‐dependent model calculations of HO2 is suggested by the agreement between model results and ATMOS observations for HO2NO2 and balloon measurements Of HO2. This confirms for the first time the procedure suggested previously by a number of authors of deriving HOx abundances from observed fields of O3 and H2O.

Microphysical and Radiative Properties of Marine Stratocumulus from Tethered Balloon Measurements

Vertical profiles of cloud microphysical data and longwave and shortwave radiation measurements through the marine boundary layer were obtained using an instrument package on the NASA tethered balloon during the FIRE Marine Stratocumulus Experiment. The radiation observations were analyzed to determine heating rates inside the stratocumulus clouds during several tethered balloon flights. The radiation fields in the cloud layer were also simulated by a two-stream radiative transfer model, which used cloud optical properties derived from microphysical measurements and Mie scattering theory. The vertical profiles of the observed longwave cooling rates were similar in structure and magnitude not only to previous measurements of marine stratocumulus, but also to the cooling rates computed by the two-stream radiative transfer model. The solar heating rates measured in the clouds, however, were systematically much larger than the rates calculated in the model. Solar albedo measurements showed that the visible spectrum tended to be reflected by the clouds more than the near IR spectrum. This is similar to the results reported by Hignett, although the discrepancies between the observed and calculated near IR to visible albedo ratios were generally much smaller. The results from the flights on 10 and 13 July 1987, however, suggest that the effects of heterogeneities on the radiative transfer through the cloud may be more important in the visible than in the new IR.

Evidence from balloon measurements for chemical depletion of stratospheric ozone in the Arctic winter of 1989–90

Measurements of the vertical ozone profile with balloon-borne sensors in the Arctic during January and February 1990 indicate repeated minima in the 22-km region. A general negative correlation of the 22-km ozone mixing ratio with time spent by the air parcel in regions cold enough for the formation of polar stratospheric clouds, together with the presence of sunlight on a portion of the air-parcel trajectory, and an inability to explain the ozone minimum by conventional dynamical processes, suggest that this feature is related to chemical ozone depletion.

Long-Term Soviet Program for the Measurement of Ionizing Radiation in the Atmosphere

The balloon measurements of the ionizing radiation have been performed at several locations of the USSR and in the Antarctic every day for more than 30 years. A number of latitude surveys were also accomplished. The methods and data presentation are described.

Ozone depletion in the Arctic Vortex at alert during February 1989

Evidence for an apparent chemical depletion of ozone was observed in the Arctic polar vortex during February 1989 in the form of a depleted layer in the ozone mixing ratio altitude profile. The measurements of the distribution of ozone partial pressure in the polar vortex were conducted with ECC ozonesondes which covered the altitude range from 1 to 30 km. These balloon measurements demonstrated a depleted layer in the profile at altitudes from 18 to 24 km. The meteorological ozonesonde balloon ascents took place from January 24 to February 22 1989 from Alert, Canada at 82.5 N. A comparison of the late February ozone profiles with the late January ozone profiles indicates that the depletion was due to a process which may have occurred while the polar air was partially in sunlight. The depleted layer was similar to that observed from the South Pole base in the Antarctic inside the ozone hole in mid‐September. The depletion may have commenced at high altitudes above 22 km and moved downwards during February in a manner similar to the process in September in the Antarctic. Polar stratospheric clouds were previously observed in mid‐January over the altitude regime from 16 to 24 km.

On the effect of electron precipitation on the fair-weather electric field

In this short paper we have estimated the influence of the diurnal modulation of the electron precipitation at low and middle latitudes of the South Atlantic Magnetic Anomaly (SAMA) on the fair-weather electric field. We have used simple exponential atmospheric conductivity models, together with the ion production rates determined from balloon and rocket measurements in the SAMA. An upper limit to this influence was also calculated and compared with the normal diurnal variation of the fair-weather electric field due to the diurnal variation of the global thunderstorm activity.

Evidence for stratospheric nitric acid condensation from balloon and rocket measurements in the Arctic

Strong evidence for nitric acid condensation at altitudes of about 18–23 km is provided by balloon-and rocket-borne measurements made near Kiruna, northern Sweden, in January 1989. Nitric acid con-densation is believed to be a necessary step in the chemical pre-conditioning required for chlorine-catalysed ozone destruction.

Electrical conductivities, ion densities and mobilities in the middle atmosphere over India—balloon measurements

Polar conductivities, ion densities and mobilities measured in three balloon experiments are reported here. Of these, two were made with self-aspirated and one with pumped Gerdien condensers. These measurements were carried out over the period 1985–1986. Both positive and negative ion data were obtained only in the first flight. Positive ions were not collected in the other two flights. The conductivity profiles obtained from the self-aspirated condensers showed fluctuations around the tropopause. These were not seen when the pumped condenser was used. Reduced mobilities of both positive and negative ions agree well with those reported by other experimenters. The ion density profile from the pumped condenser measurement showed a broad maximum around 15 km, as expected from theory. The values were less than what are obtained using available ion pair production rates and recombination coefficients.