Balloon Soundings Research Articles

The kinetic to potential energy ratio and spectral separability from high‐resolution balloon soundings near the Andes Mountains

The ratio R between the spectral kinetic and potential energies as a function of vertical wavenumber has been calculated from high‐resolution data obtained with open stratospheric balloons near the Andes Mountains. Two segments of altitude in the troposphere and stratosphere respectively were analyzed. The ratio values are larger in both the troposphere and stratosphere than those predicted from the separability of wavenumber and frequency spectra. A comparison was made with previous statistical results from soundings over flat terrain extending up to log m (cy/m) = −2.0. Our calculations prolong this interval to −2.0 ≤ log m ≤ −0.7. In the stratosphere, a remarkable similarity between that earlier work and ours is observed. This also happens in the troposphere, but only up to log m = −1.4. As suggested by the other authors, the enhanced R values might be explained by the propagation of inertial gravity waves generated in the mountain relief (this is supported by rotational spectra calculated here). Previous evidence in favor of spectral separability obtained by other authors has been extended here for larger wavenumbers by the observed constancy of the ratio between the temperature and vertical velocity spectra. In both the troposphere and the stratosphere, this ratio appears to be fairly uniform and similar to previous results obtained by other authors at lower resolution.

Lower stratospheric radiative heating rates and sensitivities calculated from Antarctic balloon observations

Temperature, water vapor, and ozone profiles from balloon soundings at McMurdo Station, Antarctica, during winter 1994 were used to calculate the diabatic heating rate in the lower stratosphere. These three variables represent the necessary inputs to a clear‐sky radiative heating rate calculation. Accurate profiles of these variables without recourse to ancillary climatological databases provide a means of testing the importance of realistic water vapor and ozone distributions to the lower stratospheric heating rate. Water vapor at wavelengths greater than 17 µm contributes as much cooling as CO2 in the lower stratosphere during winter. Dehydration begins in midwinter and causes a decrease in the cooling rate (increase in the heating rate) by 30%. Ozone depletion affects both longwave and shortwave heating rates in the altitude region where the ozone loss occurs. The longwave heating decreases by 0.3 K d−1 (potential temperature) and is comparable in magnitude to that of the decrease in shortwave heating for a balloon sounding in early October. Significant longwave heating increases of 0.6 K d−1 also occur above the region of ozone depletion as a result of higher penetration of upwelling radiation emitted by the surface. Sensitivity studies of the impact of tropospheric clouds at McMurdo show that the lower stratospheric heating rates can decrease by 0.08 to 0.26 K d−1 (vertically averaged) (18 to 60%), depending on the cloud parameterization used. Time series of the calculated heating rate at McMurdo show the effects of dehydration, ozone loss, and the increase of the heating rate (decrease of the cooling rate) as the temperatures decrease and approach radiative equilibrium through the winter.

Gravity wave characteristics in the lower atmosphere at south pole

A 4‐year (1993–1996) temperature and wind data set obtained from over 2000 high‐resolution balloon soundings at South Pole is used to study gravity wave characteristics in the troposphere and lower stratosphere. Extensive analyses of energy density, spectra, and static stability are performed to present a comprehensive view of the gravity wave characteristics in the lower atmosphere at South Pole. Our results show that the gravity waves are ubiquitous and often fairly strong at South Pole, even though the generation mechanisms are not clear. Gravity wave characteristics are, in general, similar to those obtained at other high‐latitude southern hemisphere stations. Potential energies vary between about 0.5 J/kg and 5 J/kg with season and altitude. Variations in kinetic energies are not well correlated with potential energy variations and range from 1 J/kg to 11 J/kg. We observe significant seasonal variations of the slope and magnitude of the vertical wavenumber spectrum of temperature fluctuations, especially in the stratosphere. In general, the gravity waves in the stratosphere are stronger (weaker) in austral spring (fall). Wave activity in the troposphere has little seasonal dependence. Stability analysis shows that instabilities are more likely to occur in the troposphere than in the stratosphere. The probability of wave instability is 13.7% in the troposphere and 5.4% in the stratosphere. This is due to the less stable stratification in the troposphere, where the buoyancy period averages 8.3 min compared to 4.9 min in the stratosphere. Dynamic (shear) instability is more likely to occur than convective instability (11% versus 2.6% in the troposphere and 4.7% versus 0.7% in the stratosphere), due to the prevailing strong wind shear. The instability probabilities vary seasonally with the austral winter exhibiting the highest probability of instabilities (dynamic and convective instabilities combined) in both the troposphere and stratosphere.

Ozone loss rates in the Arctic stratosphere in the winter 1991/92: Model calculations compared with match results

We present box model calculations of ozone loss rates corresponding to the results of the Match experiment 1991/92. The Match technique infers chemical ozone depletion from an analysis of pairs of balloon soundings that measure ozone in the same airparcel at different points of a calculated trajectory. It allows a quantitative comparison with model results because the exposure of the observed air‐masses to sunlight is well known. The model significantly underestimates the loss rates inferred for January to mid‐February. Extensive sensitivity studies show that the discrepancy between model and Match results cannot be explained by the known uncertainties in the model parameters.

Estimates of cloud charge densities in thunderstorms

The total charge density and the precipitation charge density inferred from six balloon soundings of electric field and precipitation charge are compared in order to examine the distribution of cloud charge density in small New Mexican mountain thunderstorms. Cloud charge density magnitudes were typically less than 2.0 nC m−3, and the maximum cloud charge densities were −2.1 and +6.7 nC m−3. The cloud charge density made a significant contribution to the total charge density in most of the thunderstorm depth, especially in the upper positive and upper negative charge regions, where all the charge was typically on cloud particles. The largest positive cloud charge densities were found just above the main negative charge region. In the lower part of the main negative charge region, the cloud charge density was the major contributor to the total charge density, and the precipitation charge played a minor role. The cloud charge density was often zero in lower positive charge regions but was 20–50% of the total charge density in two cases. Between the upper positive charge region and the bottom of the main negative charge region the cloud charge density changes polarity and tends to become increasingly negative with decreasing altitude.

Charged precipitation and electric field in two thunderstorms

The net electric charge density on all particles inside a thunderstorm can be estimated from measurements of the electric vector along a mainly vertical path of a balloon‐borne sensor. In addition, the net charge density on precipitation particles such as raindrops, hail, and graupel can be deduced from measurements of the charge on each individual particle. This paper reports on two balloon soundings of electric field and precipitation charge in two different storms in central New Mexico. The two soundings are similar at lower heights and different at higher heights, possibly because one balloon ascended outside the main convective updraft core of the storm, while the other balloon ascended within the updraft. Six charge regions were inferred from the sounding outside the updraft core in the convective region. In the lowest four charge regions, including the lower positive, main negative, and two oppositely charged regions in between, the detected precipitation charge density (on particles with individual charges of at least 10 pC) was of the same polarity and as large or larger in magnitude than the total charge density. At the top of and 0.4 km above the main negative charge region a large number density (about 125 m−3) of negatively charged precipitation particles were detected; these particles had larger mean charge (−48.6 pC) than any other group of positive or negative particles detected elsewhere in the sounding. The second electric field sounding was typical of updraft soundings below 8.0 km, and the precipitation particles detected were all positively charged below 5.3 km and all negatively charged above. The detected precipitation charge density, although smaller in magnitude, was of the same polarity as the total charge density in the lower positive and main negative charge regions.

Surface air mass origins during the First Aerosol Characterization Experiment (ACE 1)

During the First Aerosol Characterization Experiment (ACE 1) a number of meteorological and atmospheric composition measurements were made to identify anthropogenically impacted conditions and to infer information about air parcels during transport to the sampling point. Radon was used as an indicator of land contact supported by back trajectory calculations; additional information on anthropogenic sources was obtained from the concentrations of condensation nuclei and elemental carbon. A limited extension of the air mass categorization utilizes altitude profiles of potential temperature and water content derived from balloon soundings at the fixed sites. The four surface platforms were found to sample a very similar range of conditions, from very clean marine air masses to those strongly influenced by anthropogenic sources. Although this was expected because the study area is essentially encompassed by the one meteorological system, the precise origins of air masses were usually different for each platform, even, for example, when the Discoverer was within a hundred kilometres of Cape Grim. There was good agreement between the different air mass indicators under conditions when they could be compared. Radon was present when the back trajectory indicated passage over land at low altitude. Vertical profiles of potential temperature and water concentration were generally consistent with the origin of back trajectories. Excursions in the concentrations of condensation nuclei and elemental carbon occurred during periods of elevated radon concentrations when the path from land was short. However, these coincident periods of elevated concentration were rare when there was a long enough time from land for the different processing of each species to take effect.

Observations of Tropical Stratospheric Winds before World War II

This paper discusses observations of the winds in the tropical stratosphere taken before the advent of regular operational balloon soundings in this region. These observations are at least broadly consistent with modern measurements, in the sense that they show that the winds in the tropical stratosphere have been undergoing some strong interannual variations over the last century. However, the available data appear to be too sparse to construct a detailed chronology of the quasi-biennial oscillation before about 1950.

An analysis of 25 Years of balloonborne aerosol data in search of a signature of the subsonic commercial aircraft fleet

The University of Wyoming balloonborne condensation nuclei (CN) record for 1973–1997 was analyzed to determine possible effects of commercial aircraft on the 8.6–12.7 km altitude range of the atmosphere, which includes the primary commercial airlanes between 29 and 41 kft. Thin layers of highly concentrated CN are often observed in this region of the atmosphere. Generally, aircraft flight information is not available for past balloon soundings making it impossible to ascribe a source to any specific observed CN layers. However, a CN layer observed in March 1997 was traced to a particular aircraft thus supporting the hypothesis that at least some of the observed layers are contrail remnants. Using the Laramie data set, a method was developed to quantify the enhancement in CN concentration induced by aircraft in comparison with natural background levels. We estimate conservatively that the contribution of the commercial aircraft fleet in the vicinity of Laramie, Wyoming, averaged over the period of record, amounts to about 10% of the background CN concentration. The frequency of occurrence of the CN layers approximately doubled from 1980 to 1992.

Ground‐based measurements of tropospheric and stratospheric BrO at Arrival Heights, Antarctica

Ground‐based measurements of BrO slant column densities (SCDs) were performed using zenith sky DOAS (Differential Optical Absorption Spectroscopy) during autumn (February to May) and spring (August to October) of 1995 at Arrival Heights (77.8°S, 166.7°E).In both August and September, single episodes of sudden large BrO column enhancement (of magnitude 3.5 and 3.2 × 1014 molec. cm−2 respectively) were observed. The episode in August did not coincide with changes of other stratospheric parameters (OClO, NO2 and temperature). Furthermore, the diurnal variation in the SCD during these events was indicative of a tropospheric rather than a stratospheric absorber. The tropospheric BrO mixing ratios deduced from the data are similar to those observed by ground‐based measurements in the Arctic boundary layer (∼30 ppt).Simultaneous balloon soundings, one during each of the two events, showed statistically significant (2 σ) tropospheric ozone depletion between 0.5 and 2 km in August and 1.5 and 2.8 km in September. Our results strongly suggest that halogen catalysed boundary layer ozone depletion not only occurs in the Arctic but also in Antarctica. This has the implication that Arctic Haze and anthropogenic influence is unlikely as a cause for this phenomenon.

Thunderstorm Initiation, Organization, and Lifetime Associated with Florida Boundary Layer Convergence Lines

Abstract The initiation, organization, and longevity of thunderstorms associated with boundary layer convergence lines in the Cape Canaveral, Florida, vicinity are examined using data from the Convection and Precipitation/Electrification (CaPE) experiment. The project was conducted during July and August 1991 under low vertical wind shear situations. This observational study is based on Doppler radar, mesonet, balloon sounding, and satellite data. The primary convergence lines studied were the east coast sea-breeze front (ECSBF) and a frequently occurring gust front from the west termed the west coast front (WCF) that originates with storms initiated by the west coast sea-breeze front. Significantly fewer storms were associated with the ECSBF in comparison to the WCF. This was because the convergence with the ECSBF was shallower and weaker and the updrafts were shallow and tilted. The environmental winds were generally westerly near the top of the ECSBF and at storm steering level. As a result, the low-le...

Photochemical ozone production in the convective mixed layer, studied with a tethered balloon sounding system

In 1987, 1988, and 1990, four measuring campaigns with a tethered balloon sounding system were performed in a semirural area in Belgium to study the ozone distribution in the boundary layer in relation to meteorological parameters, during episodes of photochemical ozone production in the convective mixed layer. The detailed profiles of the ozone concentration between sunrise and sunset were used for a calculation of the change rate of the ozone column density in the boundary layer. These values allowed us to determine for the first time the integrated ozone production rates in the convective mixed layer, making use of a simplified form of the continuity equation of ozone mass. From all the measuring campaigns a range of integrated ozone production rates from 0 to 9 μg m−2 s−1 was found. Peak values of the ozone production rate were observed when the direct solar radiation intensity rises for the first time in the course of a day to about 400 W m−2 before noon. The upper envelope of a scatterplot of all ozone production rates as a function of the direct solar radiation shows a linear course up to about 650 W m−2. Beyond this value the intensity of direct solar radiation is no longer a rate‐limiting factor in the photochemical ozone production process in the boundary layer; under these conditions the ozone production is limited by the supply rate of hydrocarbons. In general, the measured ozone production rates also show an increase with increasing ambient temperatures. At temperatures larger than 24°C the integrated net ozone production rate during the campaigns was always at least 3 μg m−2 s−1 when the direct solar radiation values were larger than 350 W m−2 . The surface ozone deposition velocity at the site of the campaigns was determined from the ozone data through an indirect method that does not require any parameterization of the vertical ozone flux; at daylight conditions an upper limit of 1.4 cm s−1 was found.

High‐resolution temperature profiles measured with stratospheric balloons near the Andes Mountains

A spectral analysis of two balloon soundings of temperature performed in the troposphere and lower stratosphere over the Andes Mountains in Argentina with a vertical resolution of 10 m has been performed. The first and second soundings, launched at the same location, were performed during unusually calm and disturbed atmospheric conditions respectively. Considerable deviations from the −3 value predicted for the spectral slopes in the power‐law range by current saturation theories are found. These departures are reduced if the data resolution at disposal is diminished, thereby eliminating the highest wavelength harmonics. Slopes do not clearly steepen with increasing height as suggested by other authors and topography seems to be responsible for this fact at low altitudes. The spectral amplitude increase with height detected from recent lidar data is corroborated only in the sounding with calm atmospheric conditions. Spectra are found to scale with the buoyancy frequency not as simply as suggested by the saturation models.

Vertical wavenumber spectra of wind and temperature from high‐resolution balloon soundings over Illinois

We spectrally analyzed high‐resolution balloon measurements of vertical profiles of temperature and horizontal wind in the troposphere and lower stratosphere over very flat terrain in Illinois. This paper is principally concerned with spectra in the power law range at vertical wavenumbers m ≥10−3 cycle/m. The logarithmic spectral slopes and amplitudes are found to have only insignificant dependencies on meteorological parameters, including time of day, season, wind speed and direction, vertical shear, etc., except that between the troposphere and stratosphere the spectral amplitude scales as (N2)q with q ∼0.3, where N is the buoyancy frequency. The mean slopes are ≈−3 in the stratosphere and ≈ −2.6 in the troposphere. On the average the individual spectra with larger amplitudes have less negative spectral slopes. The wide variation of spectral slopes (σ≈0.5) and amplitudes and the weak dependence on N2 are quite inconsistent with the predictions of theories of saturated spectra. Further, the wind spectra in the troposphere and stratosphere are correlated, which suggests some unsaturated propagation between the regions. The ratio of kinetic to potential energy spectra is constant versus m, consistent with the linear gravity wave polarization relations. The magnitude of the model ratio can be brought into agreement with the observed ratio by assuming a model intrinsic frequency spectrum varying as ω−p with p ∼5/3 to 2 plus an enhancement of energy near the inertial frequency.

A Comprehensive System for Measuring Wake Vortex Behavior and Related Atmospheric Conditions at Memphis, Tennessee

Models of vortex behavior as a function of atmospheric conditions are being developed in an attempt to improve safety and minimize unnecessary airport capacity restrictions due to wake vortices. Direct measurements of vortices and the relevant meteorological conditions in an operational setting, which would serve to improve the understanding of vortex behavior, are scarce and incomplete. A comprehensive vortex, meteorological, and aircraft measurement system has been constructed at Memphis International Airport and operated in two 1-month periods during 1994 and 1995. A 10.6 µm continuous-wave (CW) coherent lidar was used to measure vortex parameters with high fidelity. This lidar features a number of improvements over previous systems, including an automatic vortex detection and tracking algorithm to ensure efficient scanning. Meteorological data were collected from a 45 m instrumented tower, balloon soundings, a wind profiler/radio acoustic sounding system (RASS), sonic detection and ranging (SODAR), and other sensors. This paper presents ensemble distributions of the conditions under which the over 500 aircraft were measured, and samples of vortex and atmospheric measurements. These data will be compared with theoretical predictions of vortex behavior as part of the development of an operational system designed to reduce aircraft spacings in the terminal area.

Influence of a priori profiles on trend calculations from Umkehr data

Although the new (1992) ozone profile retrieval algorithm for Umkehr measurements provides much better agreement with ozone sounding results than the old (1964) algorithm, considerable discrepancies remain with respect to ozone trends at different levels in the atmosphere. These discrepancies have been found by the comparison of long‐term trends obtained from the Umkehr measurements at Arosa and the ozone balloon soundings at Payerne (Switzerland). It is investigated here whether these obvious discrepancies can be removed by using time‐dependent a priori profiles. This procedure is successful only in the lowest part of the atmosphere, below about 19 km. To further explore this problem, synthetic Umkehr observations are calculated from the ozonesonde profiles. Trends are calculated for both the synthetic and actual Umkehr observations. The difference pattern between these Umkehr observation trends is compared with the difference in ozone profile retrieval trends from the synthetic and actual observations. The distinctive difference patterns strongly indicate an inherent disagreement between the Umkehr observations and the ozonesonde profiles. The application of corrections for stratospheric aerosol effects to the Umkehr profiles reduces, but does not eliminate, a discrepancy above 32 km. It is concluded that the discrepancies are due to the constant mixing ratio assumption used in computing the residual ozone above balloon burst level and to the fair‐weather bias of Umkehr observations (there are Umkehr observations at Arosa on fewer than 20% of the sonde observation days at Payerne). This sampling difference influences the results for the lower stratosphere. The study furthermore indicates that the ozone trends derived from Umkehr measurements for altitudes above about 32 km are robust for time‐dependent changes in the a priori profiles at lower altitudes. Based on the results of this study, we conclude with revised recommendations as to which atmospheric layers should be used for Umkehr trend studies.

High‐resolution radiosonde data offer new prospects for research

Until recently, the world's various national meteorological services routinely discarded high‐resolution data from their operational balloon soundings, saving only data at the standard levels that are required to be sent over the Global Telecommunication System for use in real‐time weather forecasting. In the last few years this situation has begun to change, and a few countries now archive data at quite high vertical resolution (∼100 m spacing or less). These high‐resolution data provide important information on the dynamics of the upper troposphere and lower stratosphere, notably in characterizing aspects of the internal gravity wave field in this part of the atmosphere. Given the importance of parameterizing gravity wave effects in numerical climate simulation models [e.g., McFarlane, 1987; Garcia and Bouille, 1994], this is an area of considerable practical significance. In addition, data assimilation and numerical weather forecasting stand to benefit from the availability of high‐resolution data.

Vertical sampling and analysis of nonmethane hydrocarbons for ozone control in urban North Carolina

As part of an effort by the state of North Carolina to develop a State Implementation Plan for ozone control in the Raleigh Metropolitan Statistical Area (MSA), vertical measurements of C2‐C10 hydrocarbons were made, in and above the surface inversion layer (SIL), as inputs to the urban airshed model (UAM). Three‐hour integrated ambient air samples were collected during August 1993 from 0500–0800 eastern daylight time (EDT). Additional samples were collected from 1200–1500 and 1700–2000 EDT on selected days. Vertical sampling was achieved from a 610‐m television tower located approximately 15 km southeast of the downtown area. Boundary layer wind and temperature profiles were determined by balloon soundings. For some compounds, e.g., propane, the average concentration was lower above the inversion layer (9.59 ppbC in the SIL and 2.08 ppbC above the SIL); however, other species such as 2‐methylpentane had higher concentrations above the inversion layer (1.28 ppbC in and 1.40 ppbC above the SIL). In addition, the vertical distributions of hydrocarbons within the convective boundary layer were compared to the vertical distribution estimated from calculations based on surface concentration, species reactivity, and eddy diffusivity. Compounds such as isoprene and N‐butane decreased as predicted by the equation, while others such as propane and benzene showed unexpected profiles. Calculations of propylene‐equivalent concentrations were used to estimate the effect of reactivity on the relative importance of individual hydrocarbons. The contribution of isoprene to the local hydrocarbon budget was analyzed and surface measurements were compared with data collected in Atlanta, Georgia, during the 1992 Southern Oxidants Study. Isoprene comprised more than 70% of the total propylene‐equivalent concentration in the afternoon in Raleigh but only 40% of the total in Atlanta.

Rocket and balloon observations of electric field in two thunderstorms

Instruments that measure the intense electric field strengths in thunderclouds (∼100 kV m−1) are designed to minimize the production of ions by small electrical discharges (coronas) emanating from the instruments themselves. The nearby charge of these ions would unpredictably disturb the natural field of the cloud. In an attempt to assess this disturbance, two different instruments (one carried by a rocket and one carried by a balloon) were launched on two occasions into thunderstorms. In spite of differing trajectories, the soundings were similar, which gives us some confidence in both instruments. In addition, the measurements revealed some interesting features of the two storms. Each storm appeared to have six significant and distinct regions of charge. The balloon soundings also revealed that lightning flashes temporarily increased the electric field strength above the thunderclouds (at altitudes from 9.7 to 14.3 km) by amounts up to 10 kV m−1, after which the fields decayed away in 50 to 125 s. One pair of ascent and descent rocket soundings, separated in time by a maximum of 60 s and horizontally by 1 to 3 km, showed little change in the thunderstorm electric field between ground and 7.5 km altitude.

Diel variations of H2O2 in Greenland: A discussion of the cause and effect relationship

Atmospheric hydrogen peroxide (H2O2) measurements at Summit, Greenland, in May–June, 1993 exhibited a diel variation, with afternoon highs typically 1–2 parts per billion by volume (ppbv) and nighttime lows about 0.5 ppbv lower. This variation closely followed that for temperature; specific humidity exhibited the same general trend. During a 17‐day snowfall‐free period, surface snow was accumulating H2O2, apparently from nighttime cocondensation of H2O and H2O2. Previous photochemical modeling (Neftel et al., 1995) suggests that daytime H2O2 should be about 1 ppbv, significantly lower than our measured values. Previous equilibrium partitioning measurements between ice and gas phase (Conklin et al., 1993) suggest that air in equilibrium with H2O2 concentrations measured in surface snow (15–18 μM) should have an H2O2 concentration 2–3 times what we measured 0.2–3.5 m above the snow surface. A simple eddy diffusion model, with vertical eddy diffusion coefficients calculated from balloon soundings, suggested that atmospheric H2O2 concentrations should be affected by any H2O2 degassed from surface snow. However, field measurements showed the absence of either high concentrations of H2O2 or a measurable concentration gradient between inlets 0.2 and 3 m above the snow. A surface resistance to degassing, that is, slow release of H2O2 from the ice matrix, is a plausible explanation for the differences between observations and modeled atmospheric profiles. Degassing of H2O2 at a rate below our detection limit would still influence measured atmospheric concentrations and help explain the difference between measurements and photochemical modeling. The cumulative evidence suggests that surface snow adjusts slowly to drops in atmospheric H2O2 concentration, over timescales of at least weeks. The H2O2 losses previously observed in pits sampled over more than 1 year are thought to have occurred later in the summer or fall, after the May–July field season.