Papers by Haflidi Jonsson
Journal of Geophysical Research, 2004
1] Airborne measurements of the ratio of spectral upward and downward irradiances (so-called spec... more 1] Airborne measurements of the ratio of spectral upward and downward irradiances (so-called spectral albedo) are used to derive the areal spectral surface albedo in the wavelength range from 330 to 1670 nm. The data were collected over different sea and land surfaces in cloudless atmospheric conditions during three field campaigns. Measurements from the Albedometer (developed at IfT) and the NASA Solar Spectral Flux Radiometer (SSFR) are employed. Spectral radiative transfer calculations show that atmospheric scattering and absorption within the layer beneath the flight level considerably contribute to the airborne albedo measurements reported here, even for low flight altitudes (0.2-0.5 km). To remove this atmospheric masking, a nonlinear extrapolation of the airborne albedo measurements to the ground is performed. The nonlinearity is due to the vertically inhomogeneous distribution of the particle microphysical properties. This fact underlines the importance of aerosol profile measurements for the proper correction of atmospheric masking. Examples of the extrapolated areal spectral surface albedos are discussed in terms of their solar zenith angle dependence, their small-scale, and general variability. Finally, typical areal spectral surface albedos for different sea and land surfaces, as derived from the three measurement campaigns, are supplied in parameterized form for use in radiative transfer applications. (2004), Airborne measurements of areal spectral surface albedo over different sea and land surfaces,
Journal of Geophysical Research, 2004
1] Airborne measurements of the ratio of spectral upward and downward irradiances (so-called spec... more 1] Airborne measurements of the ratio of spectral upward and downward irradiances (so-called spectral albedo) are used to derive the areal spectral surface albedo in the wavelength range from 330 to 1670 nm. The data were collected over different sea and land surfaces in cloudless atmospheric conditions during three field campaigns. Measurements from the Albedometer (developed at IfT) and the NASA Solar Spectral Flux Radiometer (SSFR) are employed. Spectral radiative transfer calculations show that atmospheric scattering and absorption within the layer beneath the flight level considerably contribute to the airborne albedo measurements reported here, even for low flight altitudes (0.2-0.5 km). To remove this atmospheric masking, a nonlinear extrapolation of the airborne albedo measurements to the ground is performed. The nonlinearity is due to the vertically inhomogeneous distribution of the particle microphysical properties. This fact underlines the importance of aerosol profile measurements for the proper correction of atmospheric masking. Examples of the extrapolated areal spectral surface albedos are discussed in terms of their solar zenith angle dependence, their small-scale, and general variability. Finally, typical areal spectral surface albedos for different sea and land surfaces, as derived from the three measurement campaigns, are supplied in parameterized form for use in radiative transfer applications. (2004), Airborne measurements of areal spectral surface albedo over different sea and land surfaces,
Current Allergy and Asthma Reports, 2004
Thunderstorms have often been linked to epidemics of asthma, especially during the grass flowerin... more Thunderstorms have often been linked to epidemics of asthma, especially during the grass flowering season; however, the precise mechanisms explaining this phenomenon are unknown. Evidence of high respirable allergen loadings in the air associated with specific meteorologic events combined with an analysis of pollen physiology suggests that rupture of airborne pollen can occur. Strong downdrafts and dry, cold outflows distinguish thunderstorm rain from frontal rain. The weather system of a mature thunderstorm likely entrains grass pollen into the cloud base, where pollen rupture would be enhanced, then transports the respirablesized fragments of pollen debris to ground level where outflows distribute them ahead of the rain. The conditions occurring at the onset of a thunderstorm might expose susceptible people to a rapid increase in concentrations of pollen allergens in the air that can readily deposit in the lower airways and initiate asthmatic reactions.
Geophysical Research Letters, 1993
The eruption of the Mt. Pinatubo volcano in the Philippines in June 1991 has resulted in increase... more The eruption of the Mt. Pinatubo volcano in the Philippines in June 1991 has resulted in increases in the surface and mass concentrations of aerosol particles in the lower stratosphere. Airborne measurements made at midlatitudes between 15 and 21 km from August 1991 to March 1992 show that, prior to December 1991, the Pinatubo aerosol cloud varied widely in microphysical properties such as size distribution, number, surface and volume concentrations and was also spatially variable. Aerosol surface area concentration was found to be highly correlated to extinction at visible and near-infrared wavelenghts throughout the measurement period. Similarly, backscatter at common lidar wavelengths was a good predictor of aerosol volume concentrations. These results support the use of satellite extinction measurements to estimate aerosol volume or mass if temporal changes in the relationships between the variables are considered.
Journal of Geophysical Research, 2006
Program conducted an Intensive Operations Period (IOP) to measure the radiative effects of aeroso... more Program conducted an Intensive Operations Period (IOP) to measure the radiative effects of aerosol and clouds. A suite of both in situ and remote sensing measurements were available to measure aerosol and cloud parameters. This paper has three main goals: First, it focuses on comparison between in situ retrievals of the radiatively important drop effective radius r e and various satellite, airborne, and surface remote sensing retrievals of the same parameter. On 17 May 2003, there was a fortuitous, near-simultaneous sampling of a stratus cloud by five different methods. The retrievals of r e agree with one another to within $20%, which is approximately the error estimate for most methods. Second, a methodology for deriving a best estimate of r e from these different instruments, with their different physical properties and sampling volumes, is proposed and applied to the 17 May event. Third, the paper examines the response of r e to changes in aerosol on 3 days during the experiment and examines the consistency of remote sensing and in situ measurements of the effect of aerosol on r e . It is shown that in spite of the generally good agreement in derived r e , the magnitude of the response of r e to changes in aerosol is quite sensitive to the method of retrieving r e and to the aerosol proxy for cloud condensation nuclei. Nonphysical responses are sometimes noted, and it is suggested that further work needs to be done to refine these techniques.
Aerosol Science and Technology, 2005
Data are reported for both airborne and wind tunnel testing of the aerosol inlet on the CIRPAS Tw... more Data are reported for both airborne and wind tunnel testing of the aerosol inlet on the CIRPAS Twin Otter research aircraft. Though utilizing different instrumentation and assumptions, results from the two test venues show broad agreement. The roll off in ...
Journal of Atmospheric Chemistry, 2003
During the ACE-Asia field campaign, 41 aerosol filter samples were obtained by airborne sampling ... more During the ACE-Asia field campaign, 41 aerosol filter samples were obtained by airborne sampling over the ocean to the north, south and west of Japan, generally under conditions of outflow from the Asian continent. These samples were analyzed for their water-soluble chemical components, particularly organic species. Suites of inorganic anions, carbohydrates, organic acids and metallic elements were identified and quantified (21 distinct species). Simultaneously, measurements were made of the aerosol hygroscopicity and light scattering. A factor analysis performed on the compositional data identified several sources for the aerosols sampled during the field campaign. Regression of the light-scattering data onto tracers for each of these factors suggests that the aerosol light scattering could be largely attributed to three of these factors: anthropogenic emissions, biomass burning, and soil dust. Similarly, the aerosol hygroscopicity was largely consistent with an empirical mixing model based on past measurements of the hygroscopicity of these individual aerosol types. Limited size-resolved , aerosol composition measurements were also obtained and suggested different sources for various chemical species.
Atmospheric Environment, 2004
Oxalic acid is the most abundant dicarboxylic acid found in the troposphere, yet there is still n... more Oxalic acid is the most abundant dicarboxylic acid found in the troposphere, yet there is still no scientific consensus concerning its origins or formation process. Recent studies have suggested mechanisms for its formation in cloud water from gaseous precursors. Comparison of the characteristics of oxalic acid and nss sulfate, a chemical with a known incloud formation pathway, provides some support for an aqueous formation mechanism for oxalic acid. Analysis of the filters collected from the CIRPAS Twin Otter aircraft during CARMA I, a field campaign designed to study the marine stratocumulus off the coast of Monterey, CA, by a five stage Micro-Orifice Impactor (MOI) revealed a peak in the concentration distribution at a diameter of 0.26-0.44 mm, similar to the size distribution found for nss sulfate and corresponding to the droplet mode in the aerosol size distribution. An air-equivalent average of 2.0370.47 mg m À3 (standard error) of sulfate was observed in the collected marine cloud water, in excess to below-cloud concentrations by 1.16 mg m À3 on average. This suggests in-cloud production similar in concentration to previous field campaigns in coastal marine atmospheres. Oxalate was observed in the clouds at air-equivalent concentrations of 0.2170.04 mg m À3 , in excess to below-cloud concentrations by 0.14 mg m À3 and suggesting an in-cloud production as well. The tentative identification in cloud water of one of the intermediate species in the aqueous oxalate production mechanism lends further support to an in-cloud oxalate source. r
Atmospheric Chemistry and Physics Discussions, 2008
... Authors: Sorooshian, A.; Murphy, SM; Hersey, S.; Gates, H.; Padro, LT; Nenes, A.; Brechtel, F... more ... Authors: Sorooshian, A.; Murphy, SM; Hersey, S.; Gates, H.; Padro, LT; Nenes, A.; Brechtel, FJ; Jonsson, H.; Flagan, RC; Seinfeld, JH. ... Amines were found to be a significant atmospheric base even in the presence of ammonia; particulate amine concentrations are estimated as at ...
Journal of Geophysical Research, 2000
Measurements acquired from the Office of Naval Research (ONR) Pelican research aircraft during th... more Measurements acquired from the Office of Naval Research (ONR) Pelican research aircraft during the second Aerosol Characterization Experiment (ACE 2) are analyzed to derive values for the dry (RH = 40%) aerosol number-to-volume ratio in the submicron size range. This ratio is found to be relatively constant, with a mean value of 168 _+ 21 gm -3, in agreement with previous studies elsewhere. The impact of ambient relative humidity (RH) on the dry number-to-volume is also quantified and a procedure for estimating the dry from the ambient ratio established. Finally, the feasibility of a remote retrieval of the aerosol number concentration in the submicron size range, essentially the cloud condensation nucleus concentration active at a nominal 0.2% supersaturation, is partially assessed.
Tellus Series B-chemical and Physical Meteorology, 2004
A B S T R A C T Airborne data are presented on the impact of cloud processing on the aerosol mass... more A B S T R A C T Airborne data are presented on the impact of cloud processing on the aerosol mass light-scattering efficiency. The measurements, on marine stratocumulus, suggest that cloud processing significantly enhanced the mass light-scattering efficiency in three of the five cases analysed. Enhancements were of the order of 10% for air detraining from the cloud deck relative to non-detraining air. A diagnostic modelling analysis suggested that the observed enhancements were consistent with the previously proposed explanation of in-cloud sulfate production in the particle size range for efficient light scattering.
Journal of The Atmospheric Sciences, 2006
A cloud rift is characterized as a large-scale, persistent area of broken, low-reflectivity strat... more A cloud rift is characterized as a large-scale, persistent area of broken, low-reflectivity stratocumulus clouds usually surrounded by a solid deck of stratocumulus. A rift observed off the coast of California was investigated using an instrumented aircraft to compare the aerosol, cloud microphysical, and thermodynamic properties in the rift with those of the surrounding solid stratocumulus deck. The microphysical characteristics in the solid stratocumulus deck differ substantially from those of a broken, cellular rift where cloud droplet concentrations are a factor of 2 lower than those in the solid cloud. Furthermore, cloud condensation nuclei (CCN) concentrations were found to be about 3 times greater in the solid-cloud area compared with those in the rift. Although drizzle was observed near cloud top in parts of the solid stratocumulus cloud, the largest drizzle rates were associated with the broken clouds within the rift area and with extremely large effective droplet sizes retrieved from satellite data. Minimal thermodynamic differences between the rift and solid cloud deck were observed. In addition to marked differences in particle concentrations, evidence of a mesoscale circulation near the solid cloud-rift boundary is presented. This mesoscale circulation may provide a mechanism for maintaining a rift, but further study is required to understand the initiation of a rift and the conditions that may cause it to fill. A review of results from previous studies indicates similar microphysical characteristics in rift features sampled serendipitously. These observations indicate that cloud rifts are depleted of aerosols through the cleansing associated with drizzle and are a manifestation of natural processes occurring in marine stratocumulus.
Geophysical Research Letters, 2002
Journal of Geophysical Research, 2006
1] Oxalic acid is often the leading contributor to the total dicarboxylic acid mass in ambient or... more 1] Oxalic acid is often the leading contributor to the total dicarboxylic acid mass in ambient organic aerosol particles. During the 2004 International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) field campaign, nine inorganic ions (including SO 4 2À ) and five organic acid ions (including oxalate) were measured on board the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Twin Otter research aircraft by a particle-into-liquid sampler (PILS) during flights over Ohio and surrounding areas. Five local atmospheric conditions were studied: (1) cloud-free air, (2) power plant plume in cloud-free air with precipitation from scattered clouds overhead, (3) power plant plume in cloud-free air, (4) power plant plume in cloud, and (5) clouds uninfluenced by local pollution sources. The aircraft sampled from two inlets: a counterflow virtual impactor (CVI) to isolate droplet residuals in clouds and a second inlet for sampling total aerosol. A strong correlation was observed between oxalate and SO 4 2À when sampling through both inlets in clouds. Predictions from a chemical cloud parcel model considering the aqueous-phase production of dicarboxylic acids and SO 4 2À show good agreement for the relative magnitude of SO 4 2À and oxalate growth for two scenarios: power plant plume in clouds and clouds uninfluenced by local pollution sources. The relative contributions of the two aqueous-phase routes responsible for oxalic acid formation were examined; the oxidation of glyoxylic acid was predicted to dominate over the decay of longer-chain dicarboxylic acids. Clear evidence is presented for aqueous-phase oxalic acid production as the primary mechanism for oxalic acid formation in ambient aerosols.
Journal of Geophysical Research, 2007
This study analyzes 27 cumuliform and stratiform clouds sampled aboard the CIRPAS Twin Otter duri... more This study analyzes 27 cumuliform and stratiform clouds sampled aboard the CIRPAS Twin Otter during the 2004 ICARTT (International Consortium for Atmospheric Research on Transport and Transformation) experiment. The dataset was used to assess cloud droplet closure using i) a detailed adiabatic cloud parcel model, and, ii) a state-ofthe-art cloud droplet activation parameterization. A unique feature of the dataset is the sampling of highly polluted clouds within the vicinity of power plant plumes.
Journal of Geophysical Research, 2006
1] Raman lidar water vapor and aerosol extinction profiles acquired during the daytime over the D... more 1] Raman lidar water vapor and aerosol extinction profiles acquired during the daytime over the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site in northern Oklahoma (36.606 N, 97.50 W, 315 m) are evaluated using profiles measured by in situ and remote sensing instruments deployed during the May 2003 Aerosol Intensive Operations Period (IOP). The automated algorithms used to derive these profiles from the Raman lidar data were first modified to reduce the adverse effects associated with a general loss of sensitivity of the Raman lidar since early 2002. The Raman lidar water vapor measurements, which are calibrated to match precipitable water vapor (PWV) derived from coincident microwave radiometer (MWR) measurements were, on average, 5-10% (0.3-0.6 g/m 3 ) higher than the other measurements. Some of this difference is due to out-of-date line parameters that were subsequently updated in the MWR PWV retrievals. The Raman lidar aerosol extinction measurements were, on average, about 0.03 km À1 higher than aerosol measurements derived from airborne Sun photometer measurements of aerosol optical thickness and in situ measurements of aerosol scattering and absorption. This bias, which was about 50% of the mean aerosol extinction measured during this IOP, decreased to about 10% when aerosol extinction comparisons were restricted to aerosol extinction values larger than 0.15 km À1 . The lidar measurements of the aerosol extinction/backscatter ratio and airborne Sun photometer measurements of the aerosol optical thickness were used along with in situ measurements of the aerosol size distribution to retrieve estimates of the aerosol single scattering albedo (w o ) and the effective complex refractive index. Retrieved values of w o ranged from (0.91-0.98) and were in generally good agreement with w o derived from airborne in situ measurements of scattering and absorption. Elevated aerosol layers located between about 2.6 and 3.6 km were observed by the Raman lidar on 25 and 27 May. The airborne measurements and lidar retrievals indicated that these layers, which were likely smoke produced by Siberian forest fires, were primarily composed of relatively large particles (r eff $ 0.23 mm) and that the layers were relatively nonabsorbing (w o $ 0.96-0.98). Preliminary results show that major modifications that were made to the Raman lidar system during 2004 have dramatically improved the sensitivity in the aerosol and water vapor channels and reduced random errors in the aerosol scattering ratio and water vapor retrievals by an order of magnitude. Citation: Ferrare, R., et al. (2006), Evaluation of daytime measurements of aerosols and water vapor made by an operational Raman lidar over the Southern Great Plains,
Journal of The Atmospheric Sciences, 2003
Regions of enhanced humidity in the vicinity of cumulus clouds, so-called cloud halos, reflect fe... more Regions of enhanced humidity in the vicinity of cumulus clouds, so-called cloud halos, reflect features of cloud evolution, exert radiative effects, and may serve as a locus for new particle formation. Reported here are the results of an aircraft sampling campaign carried out near Oahu, Hawaii, from 31 July through 10 August 2001, aimed at characterizing the properties of trade wind cumulus cloud halos. An Aerodyne Research, Inc., fast spectroscopic water vapor sensor, flown for the first time in this campaign, allowed characterization of humidity properties at 10-m spatial resolution. Statistical properties of 60 traverses through cloud halos over the campaign were in general agreement with measurements reported by Perry and Hobbs. One particularly long-lived cloud is analyzed in detail, through both airborne measurement and numerical simulation, to track evolution of the cloud halos over the cloud's lifetime. Results of both observation and the simulation show that cloud halos tend to be broad at lower levels and narrow at upper levels, and broader on the downshear side than on the upshear side, broadening with time particularly in the downshear direction. The high correlation of clear-air turbulence distribution with the halo distribution temporally and spatially suggests that the halo forms, in part, due to turbulent mixing at the cloud boundary. Radiative calculations carried out on the simulated cloud and halo field indicate that the halo radiative effect is largest near cloud top during mature and dissipation stages. The halo-enhanced atmospheric shortwave absorption, averaged over this period, is about 1.3% of total solar absorption in the column.
Journal of Geophysical Research, 2003
1] During July 2002, measurements of cloud condensation nuclei were made in the vicinity of south... more 1] During July 2002, measurements of cloud condensation nuclei were made in the vicinity of southwest Florida as part of the Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE) field campaign. These observations, at supersaturations of 0.2 and 0.85%, are presented here. The performance of each of the two CCN counters was validated through laboratory calibration and an in situ intercomparison. The measurements indicate that the aerosol sampled during the campaign was predominantly marine in character: the median concentrations were 233 cm À3 (at S = 0.2%) and 371 cm À3 (at S = 0.85%). Three flights during the experiment differed from this general trend; the aerosol sampled during the two flights on 18 July was more continental in character, and the observations on 28 July indicate high spatial variability and periods of very high aerosol concentrations. This study also includes a simplified aerosol/CCN closure analysis. Aerosol size distributions were measured simultaneously with the CCN observations, and these data are used to predict a CCN concentration using Köhler theory. For the purpose of this analysis, an idealized composition of pure ammonium sulfate was assumed. The analysis indicates that in this case, there was good general agreement between the predicted and observed CCN concentrations: at S = 0.2%, N predicted /N observed = 1.047 (R 2 = 0.911); at S = 0.85%, N predicted /N observed = 1.201 (R 2 = 0.835). The impacts of the compositional assumption and of including in-cloud data in the analysis are addressed. The effect of removing the data from the 28 July flight is also examined; doing so improves the result of the closure analysis at S = 0.85%. When omitting that atypical flight, N predicted /N observed = 1.085 (R 2 = 0.770) at S = 0.85%.
Tellus Series B-chemical and Physical Meteorology, 2000
Islands during the second Aerosol Characterization Experiment (ACE-2) in June/July 1997. We prese... more Islands during the second Aerosol Characterization Experiment (ACE-2) in June/July 1997. We present CLEARCOLUMN results obtained by combining airborne sunphotometer and in-situ (optical particle counter, nephelometer, and absorption photometer) measurements taken aboard the Pelican aircraft, space-borne NOAA/AVHRR data and ground-based lidar and sunphotometer measurements. During both days discussed here, vertical profiles flown in cloud free air masses revealed three distinctly different layers: a marine boundary layer (MBL) with varying pollution levels, an elevated dust layer, and a very clean layer between the MBL and the dust layer. A key result of this study is the achievement of closure between extinction or layer aerosol optical depth (AOD) computed from continuous in-situ aerosol size-distributions and composition and those measured with the airborne sunphotometer. In the dust, the agreement in layer AOD (λ=380-1060Ênm) is 3-8%. In the MBL there is a tendency for the in-situ results to be slightly lower than the sunphotometer measurements (10-17% at λ=525 nm), but these differences are within the combined error bars of the measurements and computations.
Environmental Science & Technology, 2007
2006). Chemical composition of secondary organic aerosol formed from the photooxidation of isopre... more 2006). Chemical composition of secondary organic aerosol formed from the photooxidation of isoprene, J. Phys. Chem. A, 110, 9665-9690.
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Papers by Haflidi Jonsson