bluuebunny/crossref_metadata_2025 huggingface dataset:
Calibration, comparison, and correction of net radiation instruments used during FIFE
Authors: Field R. T. , Fritschen L. J. , Kanemasu E. T. , Smith E. A. , Stewart J. B. , Verma S. B. , Kustas W. P.
Published: February 2012

Net all‐wave radiation was observed at 22 surface sites during the 1987 observation year of the First ISLSCP Field Experiment (FIFE). Eight groups of investigators employed seven different designs of net radiometer by five different manufacturers. To establish true differences in received net radiation among sites requires knowledge of differences due to instrument performance. After careful Sun/shade calibration, side‐by‐side comparison revealed daytime differences as large as 5 to 7% for instruments of the same manufacture and 10 to 15% between manufacturer. The largest differences are between instruments with so‐called “thin windows” and “thick windows” and between instruments of “double‐dome” and “single‐dome” design. Comparisons with four‐component reference net radiation observations reveal that the double‐dome and thick window instruments have substantially lower sensitivity to longwave (thermal) net radiation than to shortwave (solar) net radiation. The magnitude of the sensitivity difference is greater when the sky is clear than when cloudy. Observations with thin window instruments agreed more closely with the reference component net radiation. Field observations made with double‐dome radiometers can be corrected when net shortwave radiation is separately measured. Such a correction is shown to reduce the systematic root‐mean‐square differences among instruments to between one half and one quarter of those shown by uncorrected measurements. When net shortwave radiation is not available, correction according to a regression comparison against a “standard” net radiometer may be used. This reduced the systematic root‐mean‐square differences by up to one half of their uncorrected values. From this analysis it is estimated that the regression corrected daytime net radiation observations reported to the FIFE Information System include systematic‐root‐mean‐square instrumental differences of 15 to 35 W m−2.
Ground‐based infrared measurements of carbonyl sulfide total column abundances: Long‐term trends and variability
Authors: Rinsland C. P. , Zander R. , Mahieu E. , Demoulin P. , Goldman A. , Ehhalt D. H. , Rudolph J.
Published: February 2012

Total vertical column abundances of carbonyl sulfide (OCS) have been derived from time series of high‐resolution infrared solar absorption spectra recorded at the National Solar Observatory McMath solar telescope facility on Kitt Peak (altitude 2.09 km, latitude 31.9°N, longitude 111.6°W), southwest of Tucson, Arizona, and at the International Scientific Station of the Jungfraujoch (altitude 3.58 km, latitude 46.5°N, longitude 8.0°E), in the Swiss Alps. The analysis of both data sets is based on nonlinear least squares spectral fittings of narrow intervals centered on lines of the intense ν3 band of OCS, the P(37) transition at 2045.5788 cm−1 and the P(15) transition at 2055.8609 cm−1, with a consistent set of spectroscopic line parameters. The Kitt Peak measurements, recorded on 30 different days between May 1977 and March 1991, show a 10% peak‐to‐peak seasonal cycle with a summer maximum and a winter minimum and a trend in the total column abundance equal to (0.1 ± 0.2)% yr−1, 2σ. Jungfraujoch solar spectra recorded on 67 different days between October 1984 and April 1991 have been analyzed. The fitted trend in the Jungfraujoch total columns, (−0.1 ± 0.5)% yr−1, 2σ, is consistent with the Kitt Peak trend results within the errors. The Jungfraujoch total columns show a more complex seasonal variation than noted in the Kitt Peak data. The mean of the daily averaged total columns, 8.44 × 1015 molecules cm−2 above Kitt Peak and 6.41 × 1015 molecules cm−2 above the Jungfraujoch station, correspond respectively to mean tropospheric mixing ratios of 0.54 ± 0.04 and 0.52 ± 0.04 parts per billion by volume; these values are consistent with previously reported remote and in situ measurements. Taken together, the results from the two sites indicate that there has been no significant change in the OCS total column abundance at northern mid‐latitudes over the last decade.
Formation of OH radicals in the gas phase reactions of O3 with a series of terpenes
Authors: Atkinson Roger , Aschmann Sara M. , Arey Janet , Shorees Basima
Published: February 2012

The gas phase reactions of O3 with ethene, isoprene, and a series of monoterpenes have been investigated at 296 ± 2 K and atmospheric pressure of air in the presence of cyclohexane at concentrations sufficient to essentially totally scavenge any OH radicals formed. The expected products of the OH radical‐initiated reaction of cyclohexane, cyclohexanone and cyclohexanol, were observed in all cases. From a knowledge of the chemistry of cyclohexane in these reaction systems and as a result of cyclohexanone and cyclohexanol formation yield data obtained in subsidiary experiments, the formation yields of OH radicals in these O3‐alkene reactions were derived. The OH radical formation yields obtained from the gas phase reactions of O3 with alkenes were ethene, 0.12; isoprene, 0.27; camphene, ≤0.18; 3‐carene, 1.06; limonene, 0.86; myrcene, 1.15; ocimene (a cis‐, trans‐ mixture), 0.63; β‐phellandrene, 0.14; α‐pinene, 0.85; β‐pinene, 0.35; sabinene, 0.26; and terpinolene, 1.03, all with estimated overall uncertainties of a factor of ∼ 1.5. For a‐pinene the effect of varying the water vapor concentration was investigated and no change in the OH radical formation yield was observed over the range of (2.5–24) × 1016 molecules cm−3 of water vapor. The experimental conditions were such that formation of OH radicals from HO2 radicals was of minor importance, and the OH radical formation yields given above refer to direct formation of OH radicals and not HO2 radicals.
Variations of mean zonal winds relating to the ozone hole
Authors: Kawahira Kohji , Hirooka Toshihiko
Published: February 2012

Dynamical effects on the development of the Antarctic ozone hole have been investigated through the analysis of the interannual variations of the monthly mean zonal winds in the southern hemisphere (SH) stratosphere using the National Meteorological Center (NMC) analyzed geopotential height data, below and above 50 mbar, and the United Kingdom Meteorological Observatory (UKMO) analyzed temperature data, from which geopotential heights are calculated. It is found that the year‐to‐year changes of the mean zonal winds in the SH winter and spring (August, September, and October) in the lower stratosphere have shown no clear trends during the period from 1980 to 1988, in contrast to the ozone depletion and temperature decline. However, surprisingly, there are apparent differences in the zonal wind comparison between the 1980s and the early 1970s which are cited from the new CIRA model compiled by Barnett and Corney (1985). The differences in the Antarctic lower stratosphere in the winter and spring are evident in that the zonal winds poleward (equatorward) of 60°S become weaker (stronger) in the 1980s by over 10 m/s than in the early 1970s. On the other hand, the amplitudes of stationary waves of wavenumber 1 in the 1980s become weaker by about half of the amplitudes in the early 1970s. These results indicate that the dynamical condition appropriate for the development of the ozone hole, less poleward transport of heat and ozone by planetary waves, had been already present during the appearance of the ozone hole in about 1980 and has still continued.
Future CH4 emissions from rice production
Authors: Anastasi C. , Dowding M. , Simpson V. J.
Published: February 2012

CH4 emissions from rice paddies have been estimated to the year 2025. A model based on current rice production per capita values (1989) for the 94 major rice‐producing countries and United Nations population predictions was used to calculate future emission fluxes of CH4. Results show that CH4 emissions from rice paddies are predicted to increase by an average of 1.1% yr−1 from the 1990 level of 97 Tg yr−1 to 145 Tg yr−1 in 2025.
Model for coefficients of turbulence and effective Prandtl number produced by breaking gravity waves in the upper atmosphere
Authors: Gavrilov Nikolai M. , Yudin Valerij A.
Published: February 2012

A mathematical model is developed for the calculation of turbulent characteristics within zones of wave‐induced convective and dynamical instability. The model is based on the closure of spectral turbulent equations using a semiempirical hypothesis for the spectral characteristics of turbulence. Expressions are obtained for the mean values of coefficients of turbulent viscosity and heat conduction, evaluated over one period of the internal gravity wave (IGW). Evaluations are made of typical effective turbulent Prandtl numbers for the inhomogeneous turbulence which is produced by breaking saturated and nonsaturated IGW in the middle and upper atmosphere.
Carbon dioxide budget in a temperate grassland ecosystem
Authors: Kim Joon , Verma Shashi B. , Clement Robert J.
Published: February 2012

Eddy correlation measurements of CO2 flux made during May–October 1987 and June–August 1989 were employed, in conjunction with simulated data, to examine the net exchange of CO2 in a temperate grassland ecosystem. Simulated estimates of CO2 uptake were used when flux measurements were not available. These estimates were based on daily intercepted photosynthetically active radiation, air temperature, and extractable soil water. Soil CO2 flux and dark respiration of the aerial part of plants were estimated using the relationships developed by Norman et al. (1992) and Polley et al. (1992) at the study site. Our results indicate that the CO2 exchange between this ecosystem and the atmosphere is highly variable. The net ecosystem CO2 exchange reached its peak value (12–18 g m−2 d−1) during the period when the leaf area index was maximum. Drought, a frequent occurrence in this region, can change this ecosystem from a sink to a source for atmospheric CO2. The degree to which this grassland can become a source of CO2 appears to depend not only on the severity and duration of the drought but also on the timing of the drought event in relation to the growth stage of the prairie vegetation. Comparison with data on dry matter indicated that the aboveground biomass accounted for about 45–70% of the net carbon uptake, suggesting the importance of the below ground biomass in estimating net primary productivity in this ecosystem.
Surface flux measurements in FIFE: An overview
Authors: Kanemasu E. T. , Verma S. B. , Smith E. A. , Fritschen L. J. , Wesely M. , Field R. T. , Kustas W. P. , Weaver H. , Stewart J. B. , Gurney R. , Panin G. , Moncrieff J. B.
Published: February 2012

In 1987 the Surface Flux Group of the first ISLSCP Field Experiment (FIFE) operated 22 stations at 20 sites. In 1989, 13 sites were instrumented. A variety of sensors were employed to calculate the fluxes of mass and energy. An effort was made throughout the FIFE campaign to compare sensors. A series of papers in this special issue present these group studies and efforts. These papers principally report the 1987 campaign, although two papers report station intercomparison during 1989. Additional papers examine the time‐space variability of heat, moisture, and momentum fluxes, as well as analyses of the properties of the CO2 fluxes and their relationships to water stress. In this overview paper we describe the basic methodologies of the measurements, provide details on the sensor systems used by members of the Surface Flux Group, and provide a summary of the flux articles appearing in this special issue.
Spatial variability of evaporation derived from aircraft and ground‐based data
Authors: Holwill C. J. , Stewart J. B.
Published: February 2012

Ground‐based measurements of radiative surface temperature and energy fluxes at site 26 (8739‐ECB) have been used to correct aircraft measurements of radiative surface temperature made over the Institute of Hydrology (IH) site and to estimate the spatial variation of sensible and latent heat fluxes around the site. Over 80% of a 5‐ by 5‐km area surrounding the IH site, the sensible heat flux varied between 30 and 90 W m−2 and the evaporation between 4.5 and 5.5 mm d−1. Extrapolation to site 16 (4439‐ECV) gave reasonable agreement between estimated and measured sensible heat fluxes, after adjustment for the enhanced rate of transfer at site 16 caused by additional roughness and wind speed.
Biomass Burning Airborne and Spaceborne Experiment in the Amazonas (BASE‐A)
Authors: Kaufman Y. J. , Setzer A. , Ward D. , Tanre D. , Holben B. N. , Menzel P. , Pereira M. C. , Rasmussen R.
Published: February 2012

In the Biomass Burning Airborne and Spaceborne Experiment in the Amazonas (BASE‐A), conducted in September 1989, trace gas and particulate matter emissions were measured from biomass burning due to deforestation and grassland fires in South America. This information is required for a better understanding of the environmental impacts of biomass burning in the tropics and to improve algorithms for remote sensing of biomass burning from satellite platforms. The field experiment utilized the twin‐engine Embraer Bandeirante EMB‐1Ol instrumented aircraft of the Brazilian Institute for Space Research (INPE). Concentrations of ozone, CO2, CO, CH4, and particulate matter were measured from the aircraft. Fires were observed from satellite imagery, and the smoke optical thickness, particle size, and profiles of the extinction coefficient were measured using sunphotometers in the aircraft and from the ground. Four smoke plumes were sampled, three vertical profiles were measured, and extensive ground measurements were conducted of smoke optical characteristics for different smoke types. The collected data were analyzed for determining the emission ratios and combustion efficiency (the efficiency of a fire to convert the total burned carbon to carbon dioxide) and were compared with the results from fires in North America. Combustion efficiency was found to be higher in the tropics (97% for the cerrado and 90% for the deforestation fires) with emission factors similar to those of North American fires, for a given combustion efficiency. A strong relation was found between the spatial distribution of fires (up to 9000 per day in one state) and ozone concentration (up to 80 ppbv) and between biomass burning and concentrations of trace gases, particulate matter, and ozone. These relations strongly suggest a correlation between biomass burning in the tropics and ozone formation. An optical model of the smoke aerosol was derived and applied to radiance measurements. The smoke single scattering albedo was computed from the graphitic carbon concentration (assuming external mode mixture) as 0.90 ± 0.01. The particles effective radii were 0.1 to 0.2 μm, except for 1‐day aged smoke with values up to 0.4 μm. Radiance measurements indicate that the width of the particle size distribution may be smaller in the tropics than for North American fires. The measured optical properties of smoke and the high correlation between emitted trace gases and particles form a basis for remote sensing of radiatively important trace gases and particulate matter from biomass burning using AVHRR imagery.
Characteristics of Antarctic stratospheric aerosols during the 1987 ozone depletion episode based on SAGE II satellite observations
Authors: Lin N.‐H. , Saxena V. K.
Published: February 2012

The stratospheric aerosols play an important role in the formation of polar stratospheric clouds which are linked to Antarctic ozone depletion. The aerosol extinction profiles for higher latitudes have been monitored by the SAGE II (Stratospheric Aerosol and Gas Experiment II) satellite. In this study, features of Antarctic stratospheric aerosols during the ozone depletion episode of October 1987 are investigated based on the SAGE II data. The study focuses on (1) inferring the aerosol size spectrum using a modified randomized minimization search technique and (2) investigating the vertical, zonal, and columnar averages of aerosol properties such as extinction coefficient, optical depth, mean and effective radii, mass loading, total number concentration, and surface area concentration, together with the ozone concentration. The aerosol size distribution is found to be bimodal in several instances. An enhanced aerosol layer of relatively larger particles at altitudes between 21 and 23 km was found in Antarctic region. The effective radius can be fitted by Angström coefficient using either a linear or quadratic equation. On the average, in the region below 18 km, maximum values for the parameters of mass loading, total number, and surface area concentration were found to be located just above the region of the most severe ozone depletion. As to the columnar aerosol properties, bimodal feature in the size distribution is found during the days when the peak values of optical depth are greater than 10−3. Relatively abundant population of smaller particles is associated with the region of severe ozone depletion. The distinct latitudinal gradients of these aerosol parameters suggest that the stratospheric a rosols are separated into two regimes near 62°S–63°S, probably as a result of the dynamics introduced by polar vortex. Smaller and larger particles dominate at higher and lower latitudes, respectively. The standard deviation for both mean and effective radii are about 20–25% of the mean values. The fluctuation of the mass loading is about 50% from the mean and about 90% for the total number. The mean optical depth in 15–30 km layer is of the order of 10 −3. The average columnar ozone amount is about 95 DU (Dobson unit) with the amplification of about 48 DU. It is pointed out that the reported features of the stratospheric aerosols in the Antarctic region are useful in providing insights into the mechanisms for ozone depletion.
Surface ozone concentrations in Europe: Links with the regional‐scale atmospheric circulation
Authors: Davies T. D. , Kelly P. M. , Low P. S. , Pierce C. E.
Published: February 2012

Daily surface ozone observations from 1978 (1976 for some analyses) to 1988 for Bottesford (United Kingdom), Cabauw, Kloosterburen (The Netherlands), Hohenpeissenberg, Neuglobsow, Hamburg, and Arkona (Germany) are used to analyze links between surface ozone variations and the atmospheric circulation. A daily Europe‐wide synoptic classification highlights marked differences between surface ozone/meteorology relationships in summer and winter. These relationships are characterized by correlations between daily surface ozone concentrations at each station and a local subregional surface pressure gradient (a wind speed index). Although there are geographical variations, which are explicable in terms of regional climatology, there are distinct annual cycles. In summer, the surface ozone/wind speed relationship exhibits the expected negative sign; however, in winter, the relationship is, in the main, strongly positive, especially at those stations which are more influenced by the vigorous westerlies. Spring and autumn exhibit negative, positive, or transitional (between summer and winter) behavior, depending on geographical position. It is suggested that these relationships reflect the importance of vertical exchange from the free troposphere to the surface in the nonsummer months. Composite surface pressure patterns and surface pressure anomaly (from the long‐term mean) patterns associated with high surface ozone concentrations on daily and seasonal time scales are consistent with the surface ozone/wind speed relationships. Moreover, they demonstrate that high surface ozone concentrations, in a climatological time frame, can be associated with mean surface pressure patterns which have a synoptic reality and are robust. Such an approach may be useful in interpreting past variations in surface ozone and may help to isolate the effect of human activity. It is also possible that assessments can be made of the effect of projected future changes in the atmospheric circulation. This potential is illustrated by the fact that up to 65% of the interannual variance in 6‐month mean surface ozone concentrations can be explained by the subregional wind speed index.
Spectral ultraviolet‐B radiation fluxes at the Earth's surface: Long‐term variations at 39°N, 77°W
Authors: Correll David L. , Clark Carl O. , Goldberg Bernard , Goodrich Vernon R. , Hayes Douglass R. , Klein William H. , Schecher William D.
Published: February 2012

Precision Measurements of UVB global irradiance in 5‐nm‐wide spectral bands centered from 290 to 320 nm were made continuously from September 1975 through December 1990. The spectral radiometer was calibrated at roughly monthly intervals. Annual maximum monthly means for total daily radiation, radiation at solar noon, and clear sky radiation at small secants all were observed to be significantly higher during the period from 1983 through 1989. The maximum monthly mean of integrated 295–320 nm total daily radiation in 1986 was 29% above the long‐term mean, 47% above the maximum in 1982, and 54% above the mean maxima for 1979–1982. These interannual changes were largest for the shorter wavelengths but were significant for all spectral bands. Interannual variations in clear sky radiation were largest at small secants. For maximum monthly means of integrated 295–320 nm flux, the secant 1.2 maximum in 1989 was 19% above the long‐term mean and the average of the maxima during 1983–1989 was 13% above the long‐term mean.
Atmospheric boundary layer studies in FIFE: Challenges and advances
Authors: Kelly Robert D.
Published: February 2012

In a brief review and introduction of 13 other articles concerning the atmospheric boundary layer (ABL), attention is focused on challenges and advances in experimental design and analysis represented by those studies, which are part of the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE). The articles not only address problems posed by the experimental site itself (size, inhomogeneity of terrain, and vegetation) but also examine relationships between the ABL and remote sensing measurements. They also scrutinize various ABL data for internal consistency, for example, in budget studies, and for comparisons with other ABL results and with data from surface measurements. Finally, new and existing analysis techniques are presented and evaluated, for example, for ABL self‐preservation, extraction of wind velocities from lidar reflectivity data, estimation of surface heat flux from Doppler lidar data, two‐dimensional maps of ABL and surface variables, sensitivity of aircraft data to surface variations, and contribution of individual ABL structures to flight‐level fluxes. Besides adding to our understanding of ABL processes, the studies point out several problems that need to be addressed by the measurement and modeling communities.
On the transient response of a simple coupled climate system
Authors: Kim Kwang‐Yul , North Gerald R. , Huang Jianping
Published: February 2012

This paper presents quasi‐analytical solutions to a class of coupled atmosphere‐ocean models for time‐dependent ramp‐ and step‐forced climate changes. The model consists of a conventional two‐dimensional energy balance model of the atmosphere with an oceanic mixed layer coupled to a deep ocean having vertical heat transports due to horizontally uniform vertical diffusion and upwelling. The solution is partitioned into the particular or asymptotic part and the homogeneous or transient part. This partitioning facilitates understanding the different time constants involved in the problem. For ramp forcing there are two time constants: the lag time in the asymptotic straight line warming solution and the characteristic adjustment time to the asymptotic curve. The lag behind the “no inertia” warming is a few decades, while the adjustment time to the asymptotic curve is several hundred years due to the restructuring of the thermal profile near the main thermocline. This is in strong contrast to the step‐forcing scenario where the adjustment time to the new constant steady state is only a few decades. The latter experiment suggests that step‐forcing scenarios are not very similar to ramp‐forcing scenarios. The model produces a warming of ∼ 0.5°C over the last hundred years provided the simulation is started 200 years ago. An interesting feature of the solutions is that the land surface areas lead the ocean surface areas in heating up by O (0.1°C). This may lead eventually to a fairly robust signature of the greenhouse forcing. Future models of this type probably need more horizontal dependence on the vertical heat transport parameters as well as horizontal transport mechanisms.
Longwave radiation budget parameters computed from ISCCP and HIRS2/MSU products
Authors: Wu Man Li C. , Chang Lang‐Ping
Published: February 2012

Despite the large discrepancies between the International Satellite Cloud Climatology Project (ISCCP) retrieved cloud fields and the high‐resolution infrared radiation sounder 2 (HIRS2) retrieved cloud fields, the outgoing longwave radiation (OLR) computed based on these two cloud fields are quite similar due to the cancelation effect of cloud top altitudes and cloud amount on OLR. The accuracy of temperatures and humidities on the computation of OLR is as important as the clouds. For example, the large regional discrepancies of the order of 30 W m−2 found over northern Africa are largely due to surface temperature differences. Most extensive discrepancies over the ocean are due to humidity differences. Harmonic analysis has been applied to OLR, clear sky OLR, and cloud radiative forcing at the top of the atmosphere for July 1983 using the ISCCP products. The results show that the diurnal variations of these parameters from 60°S to 60°N are larger over land than over the ocean. The clear sky OLR peaks around 1500 LST, usually over land areas, and is associated with the surface/air temperature maximum. The OLR over cloudy regions shows a similar diurnal phase as the cloud top pressure. The cloud radiative forcing at the top of the atmosphere has maximum value near 2100 LST over the U.S. Rocky Mountain areas and near 0000 and 0300 LST over equatorial Africa and southern portions of North Africa. The ISCCP‐computed longwave cloud radiative forcing has smaller diurnal variations over the ocean than the HIRS2‐computed longwave cloud radiative forcing. The difference between the twice‐a‐day monthly mean and the 8‐times‐a‐day monthly mean is small when using the ISCCP cloud products. The global mean bias of OLR from 60°S to 60°N is around 0.74 W m−2 with a standard deviation of 1.57 W m−2. Locally, the bias can be as large as 5 to 10 W m−2. This appears to indicate that the twice‐a‐day measurements of the HIRS2/MSU (around 0315 and 1515 LST, which are the equatorial cross times at nadir track) can be used to derive monthly mean OLR without significant bias.
Vertical profiles of ozone between 0 and 400 meters in and above the African equatorial forest
Authors: Cros B. , Fontan J. , Minga A. , Helas G. , Nganga D. , Delmas R. , Chapuis A. , Benech B. , Druilhet A. , Andreae M. O.
Published: February 2012

Ozone concentrations have been measured in the northern Congo, near Impfondo (1°37 N, 18°04 E) during the DECAFE experiment in February 1988. This period corresponds to the dry season in the northern part of the equatorial region. The measurements were carried out simultaneously (1) at ground level in a large clearing, (2) inside the forest between 0 and 30 m, and (3) above the forest with a captive balloon flying up to 400 m. The results presented here are compared with the data obtained in the Mayombe forest in the southern part of Congo, near Dimonika in June 1988, during the dry season. For both northern and southern forested areas the ozone concentrations measured at ground level in a large clearing exhibit daily variations with maxima in the afternoon range between 10 and 30 parts per billion by volume (ppbv) and minima at the end of the night between 4 and 15 ppbv. The characterics of each surface ozone cycle are analyzed. Inside the forest, ozone concentrations are found very low near the ground and rarely exceed 15 ppbv above the canopy. At night the ozone concentrations are always close to zero at any level from the ground to the top of the canopy. Ozone removal processes are mainly located in the canopy. The ozone concentration above the forest is seen to increase in the early morning. Likely, this ozone production has a photochemical origin, the precursors coming from soils and biomass burning. The relationships among the vertical profiles of ozone, temperature, and water vapor are discussed.
Annual and interannual variations of Earth‐emitted radiation based on a 10‐year data set
Authors: Bess T. Dale , Smith G. Louis , Charlock Thomas P. , Rose Fred G.
Published: February 2012

Earth‐emitted radiation varies in space and time due to variations of atmospheric and surface temperature, clouds, and water vapor. The method of empirical orthogonal functions (EOFs) has been applied to a 10‐year data set of outgoing longwave radiation to study this variability. Spherical harmonic functions are used as a basis set for producing equal area map results. The following findings are noted. The first EOF accounts for 66% of the variance. After that, each EOF accounts for only a small variance, forming a slowly converging series. The first two EOFs describe mainly the annual cycle. The third EOF is primarily the semiannual cycle, although many other EOFs also contain significant semiannual parts. These results reaffirm earlier studies based on a shorter data set. In addition, a much stronger spring/fall mode was found in the central equatorial Pacific Ocean for the second EOF than had been found earlier. This difference is attributed to the use of broadband radiometer data which were available for the present study. The earlier study used data from a window‐channel instrument which is not as sensitive to water vapor variations. The fourth EOF describes much of the 1976–1977 and 1982–1983 ENSO phenomena. There is typically a gap in the spectrum between a semiannual peak and the annual cycle for all but the first EOF. A semiannual dipole straddles the Asian‐Australian monsoon track.
NO versus N2O emissions from an NH4+‐amended Bermuda grass pasture
Authors: Hutchinson G. L. , Brams E. A.
Published: February 2012

We used an enclosure technique to monitor soil NO and N2O emissions during early summer regrowth of Bermuda grass (Cynodon dactylon) on sandy loam in a humid, subtropical region of southern Texas. The evolution of both gases was substantially higher from plots harvested at the beginning of the experiment and fertilized 5 days later with 52 kg N ha−1 as (NH4)2SO4 than from plots not harvested or fertilized. Emission of NO, but not N2O, was stimulated by clipping and removing the grass, probably because eliminating the shading provided by the dense grass canopy changed these plots from cooler to warmer than unharvested plots, thereby stimulating the activity of soil microorganisms responsible for NO production. Neither gas flux was significantly affected by application of N until the next rainfall dissolved and moved the surface‐applied fertilizer into the soil. Immediately thereafter, emissions of NO and N2O increased dramatically to peaks of 160 and 12 g N ha−1 d−1, respectively, and then declined at rates that closely paralleled the nitrification rate of added NH4+, indicating that the gases resulted from the activity of nitrifying microorganisms, rather than denitrifiers. Nitric oxide emissions during the 9‐week measurement period averaged 7.2 times greater than N2O emissions and accounted for 3.2% of the added N. The data indicate that humid, subtropical grasslands, which not only have large geographical extent but also have been subject to intense anthropogenic disturbance, contribute significantly to the global atmospheric NOx budget.
A simple lightning parameterization for calculating global lightning distributions
Authors: Price Colin , Rind David
Published: February 2012

A simple parameterization has been developed to simulate global lightning distributions. Convective cloud top height is used as the variable in the parameterization, with different formulations for continental and marine thunderstorms. The parameterization has been validated using two lightning data sets: one global and one regional. In both cases the simulated lightning distributions and frequencies are in very good agreement with the observed lightning data. This parameterization could be used for global studies of lightning climatology; the Earth's electric circuit; in general circulation models for modeling global lightning activity, atmospheric NOx concentrations, and perhaps forest fire distributions for both the present and future climate; and, possibly, even as a short‐term forecasting aid.
Aerosol and cloud condensation nuclei measurements in the Kuwait plume
Authors: Hudson James G. , Clarke Antony D.
Published: February 2012

Fast response in situ particle measurements within the Kuwait oil smoke plume showed that about 70% of the particles are cloud condensation nuclei (CCN) active at about 1% super saturation. The CCN size range included the entire measured particle size range between 0.024 and 1 μm. The portion of the aerosol spectrum below 0.1 μm appeared to be internally mixed (various compositions within each particle), while the larger particles tended to be externally mixed (various compositions for different particles but homogeneous composition within each particle). The majority of the CCN are very water soluble (critical supersaturations below 0.2%). This significant CCN source could have important climatic effects by altering cloud albedo and precipitation. However, cloud scavenging will reduce the atmospheric lifetimes of the particles, which is an important consideration in large‐scale atmospheric injections such as nuclear winter scenarios.
A study of the astronomical theory of ice ages in a two‐dimensional nonlinear climate model
Authors: Lin R.‐Q. , Huang R.‐X. , Apel J. R.
Published: February 2012

We introduce a new one‐level nonlinear seasonal energy balance climate model with a two‐dimensional land‐sea geography to study the astronomical theory of ice ages. The new model is more physically consistent and mathematically reliable than those previously reported. The model reproduces the current climate state and explains how the Earth's orbit causes ice ages. We have found a set of bifurcation points of warm and cold orbit for both backward and forward processes. Moreover, we found that because the Earth's orbit varies slowly, gradual increases (or decreases) in the concentration of CO2 will also cause sudden climate transitions. Thus, variations in the Earth's orbit and the concentration of CO2 appear to be the two major mechanisms that cause ice ages or climate changes; furthermore, these changes are usually sudden. Finally, we predict the near‐future climate resulting from a continual increase in CO2 concentration. The model does not yet include slower components such as the deep‐ocean circulation. Therefore, variations occur more rapidly than in the real world.
Radiation budget studies using collocated observations from advanced very high resolution radiometer, high‐resolution infrared sounder/2, and Earth Radiation Budget Experiment instruments
Authors: Ackerman Steven A. , Frey Richard A. , Smith William L.
Published: February 2012

Collocated observations from the Advanced Very High Resolution Radiometer (AVHRR), High‐Resolution Infrared Sounder/2 (HIRS/2), and Earth Radiation Budget Experiment (ERBE) instruments onboard the NOAA 9 satellite are combined to describe the broadband and spectral radiative properties of the Earth‐atmosphere system. Broadband radiative properties are determined from the ERBE observations, while spectral properties are determined from the HIRS/2 and AVHRR observations. The presence of clouds, their areal coverage, and cloud top pressure are determined from a combination of the HIRS/2 and the AVHRR observations. The CO2 slicing method is applied to the HIRS/2 to determine the presence of upper level clouds and their effective emissivity (product of cloud area amount and emissivity). The AVHRR data collocated within the HIRS/2 field of view are utilized to determine the uniformity of the scene and retrieve sea surface temperature. Changes in the top of the atmosphere longwave and shortwave radiative energy budgets, and the spectral distribution of longwave radiation are presented as a function of cloud amount and cloud top pressure. The radiative characteristics of clear sky conditions over oceans are presented as a function of sea surface temperature and atmospheric water vapor structure. The importance of spectral information in assessing changes in the top of the atmosphere radiative energy budget is demonstrated.
A modeling study of the time‐averaged electric currents in the vicinity of isolated thunderstorms
Authors: Driscoll Kevin T. , Blakeslee Richard J. , Baginski Michael E.
Published: February 2012

A thorough examination of the results of a time‐dependent computer model of a dipole thunderstorm revealed that there are numerous similarities between the time‐averaged electrical properties and the steady state properties of an active thunderstorm. Thus, the electrical behavior of the atmosphere in the vicinity of a thunderstorm be can be determined with a formulation similar to what was first described by Holzer and Saxon in 1952. From the Maxwell continuity equation of electric current, a simple analytical equation was derived that expresses a thunderstorm's average current contribution to the global electric circuit in terms of the generator current within the thundercloud, the intracloud lightning current, the cloud‐to‐ground lightning current, the altitudes of the charge centers, and the conductivity profile of the atmosphere. This equation was found to be nearly as accurate as the more computationally expensive numerical model, even when it is applied to a thunderstorm with a reduced conductivity thundercloud, a time‐varying generator current, a varying flash rate, and a changing lightning mix.
Reactive nitrogen, ozone, and nitrate aerosols observed in the Arctic stratosphere in January 1990
Authors: Kondo Y. , Aimedieu P. , Koike M. , Iwasaka Y. , Newman P. A. , Schmidt U. , Matthews W. A. , Hayashi M. , Sheldon W. R.
Published: February 2012

Total reactive nitrogen (NOy), nitrate aerosols, and ozone were measured between 12 and 30 km on board balloons launched from Esrange, near Kiruna, Sweden (68°N, 20°E), on January 18 and 31, 1990. A series of ozone measurements were performed using small balloons in addition to the measurements made simultaneously with NOy on the large gondola. On January 18, Kiruna was located inside the polar vortex, while it was outside the vortex on January 31. The NOy mixing ratio inside the vortex was 5 ± 1 parts per billion by volume (ppbv) at the altitudes between 20 and 22 km. This value is considerably smaller than the value of about 13 ppbv that is expected from gas phase chemistry, indicating that a degree of denitrification had occurred by mid‐January in 1990. On the other hand, the NOy mixing ratio outside the vortex in the same altitude region ranged between 6 and 13 ppbv, suggesting less denitrification outside the vortex. The cause of the denitrification is interpreted in terms of the very cold stratospheric temperature that prevailed from December 1989 to January 1990. The mixing ratios of nitric acid in gas phase (Schlager et al., 1990) and particulate phase (Hofmann et al., 1990) were measured on January 31, but not on the same gondola. The HNO3/NOy ratio was close to unity in a polar stratospheric cloud but decreased to 0.75 ± 0.05 outside the cloud. Assuming this ratio, HNO3 has been found to be highly supersaturated over nitric acid trihydrate particles.
Ground level measurements of air conductivities under Florida thunderstorms
Authors: Blakeslee Richard J. , Krider E. Philip
Published: February 2012

Values of the positive and negative polar conductivities under summer thunderstorms in Florida are highly variable and exhibit a significant electrode effect, but the total conductivity usually remains close to values found in fair weather, 0.4 to 1.8×10−14 S/m. With these values a method proposed by Krider and Musser in 1982 for estimating the total conductivity from changes in the slope of the electric field recovery following a lightning discharge will be extremely sensitive to small time variations in the local Maxwell current density and must be modified to include these effects.
Kuwaiti oil fires: Compositions of source smoke
Authors: Cofer Wesley R. , Stevens Robert K. , Winstead Edward L. , Pinto Joseph P. , Sebacher Daniel I. , Abdulraheem Mahmood Y. , Al‐Sahafi Mohammed , Mazurek Monica A. , Rasmussen Rei A. , Cahoon Donald R. , Levine Joel S.
Published: February 2012

While the Kuwaiti oil‐fire smoke plumes manifested a pronounced impact on solar radiation in the Gulf region (visibility, surface temperatures, etc.), smoke plume concentrations of combustion‐generated pollutants suggest that the overall chemical impact on the atmosphere of the smoke from these fires was probably much less than anticipated. Combustion in the Kuwaiti oil fires was surprisingly efficient, releasing on average more than 93% of the combusted hydrocarbon fuels as carbon dioxide (CO2). Correspondingly, combustion‐produced quantities of carbon monoxide (CO) and carbonaceous particles were low, each ∼2% by weight. The fraction of methane (CH4) produced by the fires was also relatively low (∼0.2%), but source emissions of nonmethane hydrocarbons were high (∼2%). Processes other than combustion (e.g., volatilization) probably contributed significantly to the measured in‐plume hydrocarbon concentrations. Substantially different elemental to organic carbon ratios were obtained for aerosol particles from several different types of fires/smokes. Sulfur emissions (particulate and gaseous) measured at the source fires were lower (∼0.5%) than predicted based on average sulfur contents in the crude. Sulfur dioxide measurements (SO2) reported herein, however, were both limited in actual number and in the number of well fires sampled. Nitrous oxide (N2O) emissions from the Kuwaiti oil fires were very low and often could not be distinguished from background concentrations. About 25–30% of the fires produced white smoke plumes that were found to be highly enriched in sodium and calcium chlorides.
A catchment scale water balance model for FIFE
Authors: Famiglietti J. S. , Wood E. F. , Sivapalan M. , Thongs D. J.
Published: February 2012

A catchment scale water balance model is presented and used to predict evaporation from the King's Creek catchment at the First ISLSCP Field Experiment site on the Konza Prairie, Kansas. The model incorporates spatial variability in topography, soils, and precipitation to compute the land surface hydrologie fluxes. A network of 20 rain gages was employed to measure rainfall across the catchment in the summer of 1987. These data were spatially interpolated and used to drive the model during storm periods. During interstorm periods the model was driven by the estimated potential evaporation, which was calculated using net radiation data collected at site 2. Model‐computed evaporation is compared to that observed, both at site 2 (grid location 1916‐BRS) and the catchment scale, for the simulation period from June 1 to October 9, 1987.
Spatial and temporal variations of the fluxes of carbon dioxide and sensible and latent heat over the FIFE site
Authors: Desjardins R. L. , Schuepp P. H. , MacPherson J. I. , Buckley D. J.
Published: February 2012

Airborne measurements of flux densities of carbon dioxide (CO2), sensible heat, and latent heat (H2O) obtained over the First ISLSCP Field Experiment (FIFE) site during three intensive field campaigns in 1987 and one in 1989 are examined to characterize the spatial and temporal variations of CO2 and energy transfer processes. These data were collected by the National Research Council Twin Otter using low‐level flight patterns, all flown at constant pressure altitude during relatively clear days. The spatial variations are larger in 1989 than in 1987 and a higher correlation is observed between the fluxes and the surface features. The temporal patterns are easier to characterize with the relatively homogeneous situation of 1987. Functional relationships obtained between fluxes of CO2 and latent heat, CO2 fluxes and greenness index, latent heat fluxes and greenness index, and between sensible heat fluxes and surface air temperature differences are presented for one day in 1987 and one in 1989 as an example of the kind of information that can be obtained from grid flights at constant pressure altitude.
Satellite monitoring of smoke from the Kuwait oil fires
Authors: Limaye Sanjay S. , Ackerman Steven A. , Fry Patrick M. , Isa Majeed , Ali Habib , Ali Ghulam , Wright Allan , Rangno Art
Published: February 2012

The smoke from the oil fires in Kuwait was easily visible in observations from weather satellites in polar and geosynchronous orbits. A portable work station provided these data for planning the National Center for Atmospheric Research and University of Washington research aircraft flights out of Bahrain during the Kuwait Oil‐Fire Smoke Experiment. Meteosat visible and infrared satellite observations indicate that the smoke often traveled southeast along the west shore of the Persian Gulf as far as Bahrain, at which point it typically turned west or continued south toward the Arabian coast. The smoke was difficult to detect from satellite observations as it moved over water and at large distances from the source during the night from infrared observations. Also notable among the daily satellite images were the frequent, intense dust storms that seemed to form in Syria and northern Iraq and transport dust southeastward over Kuwait, and often to northwestern Saudi Arabia. Clouds were virtually absent during the months of May and June within the first several hundred kilometers along the plume direction. Surface temperatures in Bahrain during April and August 1991 were lower than average by as much as 1°–3.2°C, and are significant compared to the climatological variability of average minimum and mean temperatures for the summer months.
Chemical composition of emissions from the Kuwait oil fires
Authors: Ferek Ronald J. , Hobbs Peter V. , Herring John A. , Laursen Krista K. , Weiss Ray E. , Rasmussen Rei A.
Published: February 2012

Airborne measurements in the srnoke from the Kuwait oil fires in May and June 1991 indicate that the combined oil and gas emissions were equivalent to the consumption of about 4.6 million barrels of oil per day. The combustion was relatively efficient, with about 96% of the fuel carbon burned emitted as CO2. Particulate smoke emissions averaged 2% of the fuel burned, of which about 20% was soot. About two‐thirds of the mass of the smoke was accounted for by salt, soot, and sulfate. The salt most likely originated from oil field brines, which were ejected from the wells along with the oil. The salt accounts for the fact that many of the plumes were white. SO2 and NOx were removed from the smoke at rates of about 6 and 22% per hour, respectively. The high salt and sulfate contents explain why a large fraction of the particles in the smoke were efficient cloud condensation nuclei.