bluuebunny/crossref_metadata_2025 huggingface dataset:
Particulate emissions from a mid‐latitude prescribed chaparral fire
Authors: Cofer Wesley R. , Levine Joel S. , Sebacher Daniel I. , Winstead Edward L. , Riggin Philip J. , Brass James A. , Ambrosia Vincent G.
Published: February 2008

Smoke aerosol was collected on filters from a helicopter during a 400‐acre (1.62 km2) prescribed chaparral burn in the San Dimas Experimental Forest on December 12, 1986. Hi‐VoI samplers were used to collect particles on both Teflon and glass fiber filters. Scanning electron microscopy of the filters revealed particles that ranged in size from about 0.1 to 100 μm. Many of the large particles (>10 μm) that appeared irregularly shaped at low magnifications were found at higher magnification to be highly agglomerated smaller spheres, often showing signs of partial coalescence. Energy dispersive analysis of X rays (EDAX) revealed carbon, oxygen, magnesium, aluminum, silicon, calcium, and iron as the primary elemental composition of the aerosols. Extractions of aerosol components in water/methanol mixtures, followed by ion Chromatographic analysis, indicated that significant levels of nitrite (NO2−), nitrate (NO3−), sulfate (SO4=), chloride (Cl−), phosphate (PO4≡), oxylate (C2O4=), sodium (Na+), ammonium (NH4+), and potassium (K+) were associated with the particles. The proportions of NO3−, NO2−, PO4≡, Na+, and C2O4 = leached from the aerosol appeared to remain relatively constant in the smoke plume collections. Analysis of soluble NH4 +, Cl−, K +, and SO4 = ions, however, suggested that either possible changes in the nature of the emissions had occurred during different stages of combustion, or that ongoing smoke plume chemistry might have influenced the levels of these ions, or both. The soluble ionic portion of the aerosol was estimated to be about 2% by weight. The first known determinations of phosphate anion from particulates collected in a biomass burn plume are reported.
Identification of cloud‐free pixels in inhomogenous surfaces from AVHRR radiances
Authors: Sakellariou N. K. , Leighton H. G.
Published: February 2008

A new method of distinguishing clear and cloud‐contaminated pixels from AVHRR data is described. Whereas most previous methods have difficulty in identifying cloud‐contaminated pixels when the background is inhomogenous, such as is the case for coastal regions or continental regions containing vegetated land and bare soil or land and water, the present method is particularly suited to these situations. Examination of the measured reflectivities in channels 1 and 2 of the AVHRR for these backgrounds and for clear skies suggests that the reflectivities are related linearly. The linear relationship is understandable in terms of pixels being comprised of linear combinations of two different surface types. Advantage is taken of this relationship as well as the radiance in channel 4 to identify cloud‐free pixels for complex surface conditions. The technique is readily automated and combined with other techniques that may be more suitable for homogenous backgrounds.
Insoluble particles in Antarctic ice: Background aerosol size distribution and diatom concentration
Authors: Ram Michael , Gayley Robert I. , Petit Jean‐Robert
Published: February 2008

We have measured insoluble particle size distributions covering the radius range 0.05–1.31 μm. for six sections of ice core from Dome C, Antarctica. Two of the sections are from the Holocene, two are from the last glacial maximum (LGM), and another two are from the period that preceded it. Our measurements lead us to the conclusion that the southern hemisphere insoluble background aerosol size distribution, in the range of our measurements, has not changed significantly over the 26,000‐year period that we studied. We also compared the concentration of diatoms in a sample of Holocene ice with that in two samples of LGM ice and found that the concentration of diatoms whose largest dimension was equal to or greater than 10 μm. was 20 times larger during the LGM, the same as the ratio we measured for the concentration of insoluble particles. We interpret this to mean that the higher dust levels were mainly due to an increase in wind strength rather than to increased continental aridity.
Observations of vertical velocities in the tropical upper troposphere and lower stratosphere using the Arecibo 430‐MHZ radar
Authors: Cornish C. R.
Published: February 2008

We report the first clear‐air observations of vertical velocities in the tropical upper troposphere and lower stratosphere (8–22 km) using the Arecibo 430‐MHz radar. Oscillations in the vertical velocity near the Brunt‐Väisälä period are observed in the lower stratosphere during the 12‐hour observation period. Frequency power spectra from the vertical velocity time series show a slope between −0.5 and −1.0. Vertical wave number spectra computed from the height profiles of vertical velocities have slopes between −1.0 and −1.5. These observed slopes do not agree well with the slopes of +1/3 and −2.5 for frequency and vertical wave number spectra, respectively, predicted by a universal gravity‐wave spectrum model. The spectral power of wave number spectra of a radial beam directed 15° off‐zenith is enhanced by an order of magnitude over the spectral power levels of the vertical beam. This enhancement suggests that other geophysical processes besides gravity waves are present in the horizontal flow. The steepening of the wave number spectrum of the off‐vertical beam in the lower stratosphere to near −2.0 is attributed to a quasi‐inertial period wave, which was present in the horizontal flow during the observation period.
Procrustes target analysis: A multivariate tool for identification of climate fluctuations
Authors: Richman Michael B. , Easterling William E.
Published: February 2008

Agriculturally important climate fluctuation types are identified by using an expert systems approach to synthesize information concerning the sensitivity of various aspects of Midwestern corn production to climatic variability. This information forms target criteria which are the basis for subsequent multivariate analysis using a technique new to meteorology, Procrustes Target Analysis (PTA), to fit the target to climatological data. Mathematical derivation of PTA is presented, along with an example of its application. The results of the analysis indicate that significant climate anomalies exist in the Midwest which agree with the target coefficients. Their spatial evolution is presented. Further investigation reveals that coherent areas of these fluctuations persist for large periods of the 15‐year windows examined and that they appear to impact corn production.
Altitude and temperature of the mesopause at 69°N latitude in winter
Authors: Neuber R. , von der Gathen P. , von Zahn U.
Published: February 2008

Temperature profiles of the altitude region 80–110 km are derived from the measurement of the Doppler width of the laser‐excited D2 resonance line of free sodium atoms. For the altitude range 85–95 km the altitude resolution, integration time, and error bar of individual temperature points are typically 1 km, 10 min, and ±5 K, respectively. Temperature data obtained during the two winter seasons 1985/1986 and 1986/1987 near Andenes, Norway (69°N, 16°E), are presented. For December–March, 743 temperature profiles are combined into four monthly mean profiles. For each of the 4 months the altitude of the mesopause is found to be 100±2 km. The mesopause temperature is close to 193 K from December through February but drops to 170 K in March. We found this in both years of our measurements.
Influence of solar radiation and heat emission on radon 222 daughter concentrations in surface air
Authors: Fujinami Naoto , Esaka Shinobu
Published: February 2008

Observations of short‐lived radon 222 daughter concentrations in surface air have been continuously carried out at a site near the Japan Sea coast for a period of about 1 year, together with measurements of solar and net radiation amounts. It is concluded from the analysis of these data that increases of solar radiation during the daytime and heat emission during the nighttime cause progressive decreases and increases of the radon daughter concentration, respectively.
Lidar observations of sporadic sodium layers at Mauna Kea Observatory, Hawaii
Authors: Kwon K. H. , Senft D. C. , Gardner C. S.
Published: February 2008

The characteristics of very dense, narrow upper atmospheric Na layers observed above Mauna Kea, Hawaii (19°50′N, 155°28′W) are described. These layers were observed on a total of 16 occasions during 30 hours of lidar measurements from January 17 to 22, 1987. The most prominent sporadic layer, which formed on the night of January 21, exhibited a peak density of 2.8×104 cm−3 near 96 km, with a full width of about 2 km. The rapid growth and decay of the layer lasted for about 40 min. The apparent Na production and decay rates of this layer were approximately 60 cm−3 s−1. Even after the decay, the narrow layer was observed continuously for almost 8 hours. During this period the layer moved downward steadily, with a mean apparent velocity of 31 cm s−1. The most significant characteristic of the 16 sporadic layers appears to be occurrence times. The layers formed either in the late evening, between 2100 and 2330 LST, or in the early morning, between 0300 and 0600 LST. The layers of the early morning began forming within a short time span of 15 min from 0253 to 0308 LST on 3 different days. The mean time of the maximum peak density of the early morning layers occurred about 6 hours after that of the late evening layers. The mechanisms responsible for creating these layers appear to be related to diurnal tides and sporadic E layers.
Measurements of nitric oxide between 0–12 km altitude and 67°N to 60°S latitude obtained during STRATOZ III
Authors: Drummond J. W. , Ehhalt D. H. , Volz A.
Published: February 2008

Using a chemiluminescent detector, vertical profiles of NO were measured during the STRATOZ III mission from June 4–26, 1984. The mission's flight track started close to Paris, went west across the North Atlantic, south along the east coast of North America and the west coast of South America. It returned north along the east coast of South America, crossed the Atlantic around the equator and continued north along the west coast of North Africa and continental Europe. It covered the latitudes between 67°N and 60°S and the altitudes between 0 and 12 km. The coastal profiles in the northern hemisphere and in the tropics exhibited a C shape, with higher NO concentration values in the planetary boundary layer and the upper troposphere, whereas the measurements over the ocean showed low values in the upper troposphere. The NO mixing ratios in the southern hemisphere, south of 20°S latitude, were lower than in the northern latitudes and showed little increase in the upper troposphere. The two‐dimensional NO distribution along the flight track is derived, and the possible sources of the NO in the high troposphere are briefly discussed.
Contribution of tropical winds to subseasonal fluctuations in atmospheric angular momentum and length of day
Authors: Benedict William L. , Haney Robert L.
Published: February 2008

Changes in the globally integrated angular momentum of the atmosphere from 1983 to 1987 were computed from Fleet Numerical Oceanography Center wind analyses and compared to astronomically measured changes in length of day obtained from the U.S. Naval Observatory. In agreement with previous studies, the two time series are highly coherent and in phase at periods ranging from 40 days up to the longest periods that are resolved by the data. By examining the contribution to the global atmospheric angular momentum from the tropical and extratropical regions separately, it is found that fluctuations in the Earth's angular momentum and length of day at subseasonal periods of 50–100 days are dominated by wind changes in the tropics.
Climatology and trends of mesospheric (58–90 km) temperatures based upon 1982–1986 SME Limb scattering profiles
Authors: Clancy R. Todd , Rusch David W.
Published: February 2008

Global observations of ultraviolet limb radiances from the Solar Mesosphere Explorer (SME) have been analyzed to obtain atmospheric temperature profiles over the altitude range 58–90 km. The temperature analysis is based upon vertical profiles of Rayleigh scattering, which are derived from the SME ultraviolet limb radiances. Comparisons are provided with lidar and Stratosphere and Mesosphere Sounder (SAMS) temperature observations at 65 km altitude, and with previous temperature climatologies of the mesosphere. SME monthly average temperature profiles are presented for 10° latitude intervals between 70°S and 70°N latitudes, over the January 1982 to September 1986 time period. The altitude resolution (∼4 km), latitudinal coverage (with 5° resolution), 5‐year term, and mesopause coverage of these temperature observations allow new insight into the average mesospheric temperature structure and unique observations of mesospheric temperature trends corresponding to the 1982–1986 solar maximum to solar minimum cycle. The SME temperature observations define large (10–30 K) semiannual oscillations of equatorial mesopause temperatures; mid‐latitude temperature inversions in the winter mesosphere accompanied by steep mesospheric temperature gradients at low latitudes, and −1.5 to +1 K/year trends, which suggest an intensification of these latitude‐dependent temperature gradients over the 1982–1986 period. The SME temperature trends are ∼4 times smaller than those reported by Mohanakumar (1985), Groves (1986), and Chanin et al. (1987) for solar cycle variations of temperatures in the altitude region 65–70 km.
Ozone precursors and ozone photochemistry over eastern North Pacific during the spring of 1984 based on the NASA GTE/CITE 1 airborne observations
Authors: Chameides W. L. , Davis D. D. , Gregory G. L. , Sachse G. , Torres A. L.
Published: February 2008

Simultaneous, high‐resolution measurements of O3, NO, CO, dew point temperature, and UV flux obtained during the NASA Global Tropospheric Experiment Chemical Instrumentation Test and Evaluation (GTE/CITE 1) spring 1984 airborne field exercise over the eastern North Pacific Ocean are analyzed. Mid‐tropospheric CO, O3, and NO mixing ratios averaged about 120 parts per billion by volume (ppbv), 50 ppbv, and 10 parts per trillion by volume (pptv), respectively. Statistical analysis of the high‐resolution data indicates the existence of two ozone sources: one related to the downward transport of ozone‐rich air from the upper troposphere and stratosphere and the other to the transport of ozone‐rich air from the continents. Modeling calculations based on these average levels imply that from the surface to about 8 km, photochemical reactions probably supplied a net sink of ozone to the region overlying the eastern North Pacific Ocean during the sampling period. However, because the NO levels measured during the flights were frequently at or near the detection limit of the instruments and because our results are very sensitive to the absolute NO levels and their temporal variability, our conclusion must be considered provisional.
Stratospheric aerosol mass content estimated by lidar after El Chichón eruptions
Authors: Gobbi Gian Paolo , Adriani Alberto , Congeduti Fernando
Published: February 2008

Lidar soundings of stratospheric aerosols performed in Frascati (41.8°N; 12.7°E) between April 1982 and October 1985 are reported. Measurements cover the buildup and most of the decline of the aerosol cloud generated by the eruptions of the Mexican volcano El Chichón (March/April 1982). Single‐wavelength lidar profiles provide height‐resolved information about the particle content of the region investigated. Data are analyzed under the assumption of a linear relationship between backscattering efficiency and particle size. Such procedure allows an estimate of aerosol mass load from lidar profiles. Results are compared with “in situ” measurements and discussed.
Parameterized desert/clear atmosphere limb‐darkening model derived from Earth Radiation Budget Satellite along‐track measurements
Authors: Brooks David R. , Fenn Marta A.
Published: February 2008

During January and August 1985 the Earth Radiation Budget Satellite from the Earth Radiation Budget Experiment (ERBE) was operated in a unique along‐track mode that allows all points along the ground track to be viewed over an entire range of viewing zenith angles at essentially constant solar zenith angle. These conditions are ideal for deriving a longwave limb‐darkening model. An analytic model that predicts longwave radiance as a function of atmospheric path length is presented. Model parameters derived from the along‐track data demonstrate that clear desert limb darkening exhibits a greater variety of diurnal, seasonal, and scene‐dependent variability than is present in the corresponding ERBE limb‐darkening models. Conversion of radiance to radiant exitance using both the derived and ERBE models show that the ERBE algorithms underestimate representative monthly mean daytime regional (2.5°×2.5°) desert radiant exitances by amounts ranging from 0.4 to less than 5 W/m2, a maximum difference of about 1.6%.
Application of angular models to AVHRR data for determination of the clear‐sky planetary albedo over land surfaces
Authors: Gutman G. , Gruber A. , Tarpley D. , Taylor R.
Published: February 2008

Clear‐sky planetary albedos are derived from NOAA 9 Advanced Very High Resolution Radiometer (AVHRR) data during 1986 over the U.S. Great Plains with several distinct surface types (shrubland, grassland, deciduous, and coniferous forests). The cloud‐free observations are selected using a combination of absolute threshold and spatial coherence cloud‐screening procedures. The broadband albedo is approximated from the narrow‐band visible and near‐infrared albedo. Bidirectional reflectivity models are applied to account for the effect of Sun‐target‐sensor geometry. The corrected albedos are converted to daily means using a directional model to account for the dependence upon Sun angle. The results indicate that the present Earth radiation budget models can be efficiently applied to AVHRR data to determine the clear‐sky planetary albedos and to remove the apparent albedo discontinuity on images of mapped data.
Balloon‐borne measurements of the stratospheric ion conductivity profile at low latitude
Authors: Beig G. , Sidhu J. S. , Das S. R. , Chakrabarty D. K.
Published: February 2008

A simple and straightforward technique has been used on balloons to measure the conductivity of ions in the altitude region of 20 to 36 km from a low‐latitude station. The sensor used was spherical in shape. Results of two such flights are discussed in this report. The values of conductivity of both positive and negative ions were found to be approximately equal and these were about (2–6)×10−12 mho m−1.
Stratospheric ozone measurements from the 1985 MAP/GLOBUS NOx campaign
Authors: Robbins D. , Aimedieu P. , Goutail F. , Pelon J. , Pommereau J.‐P. , Iwagami N. , Ogawa T. , Koike M. , Shibasaki K. , Marché P. , Naudet J. P. , Rigaud P. , Huguenin D. , Lenoble J. , Maddrea G. , McCormick M. P.
Published: February 2008

Nine experiments obtained stratospheric ozone measurements during the fall 1985 Middle Atmosphere Program (MAP) Global Budget of Stratospheric Trace Constituents (GLOBUS) NOx campaign. Measurements are grouped into four sets from four air masses and compared. Agreement between individual experiments and weighted mean profiles is generally within 10% and within absolute accuracies. Dobson Umkehr values in layer 5 differ by more than absolute accuracies from weighted mean profiles. Brewer sonde values for one data set are outside absolute accuracies near the ozone peak. Solar UV occultation measurements are 30–35% less than the weighted mean profile and outside absolute accuracies. Measurements from the Exospheric Satellite (EXOS‐C) backscattered ultraviolet (BUV) experiment, not previously compared with other techniques, agree within 10–15% of weighted mean profiles. Results of the campaign are generally consistent with those of four previous intercomparison campaigns.
Mountain waves, polar stratospheric clouds, and the ozone depletion over Antarctica
Authors: Cariolle D. , Muller S. , Cayla F. , McCormick M. P.
Published: February 2008

We report observations of ozone column and clouds at typically stratospheric altitudes, obtained during the 1987 Airbone Antarctic Experiment from the TIROS Operational Vertical Sounder (TOVS)/High‐Resolution Infrared Sounder (HIRS 2) instrument on the National Oceanic and Atmospheric Administration NOAA 10 satellite. Cloud formation occurs mainly along the coast of Antarctica when strong tropospheric winds blow from the ocean to the continent. The period of September 2–9 provides a good example of the formation of localized high‐altitude clouds over the Palmer Peninsula and the Weddell Sea. The appearance of these clouds (a subset of the more prevalent polar stratospheric clouds (PSCs)) is consistent with the presence of a strong tropospheric jet over the elevated topography of the peninsula. Mountain waves and their associated high‐altitude adiabatic cooling are the driving mechanism for the cloud formation. On the basis of the cloud area coverage and wind analyses, we estimate that in the altitude range 14–18 km the air within the polar vortex has spent 5% of its time inside these clouds from early August to late September. The importance of this observation for springtime ozone depletion mechanisms is discussed. It is also concluded that the TOVS data set recorded during the past decade would be suitable to search for a possible trend in the cloud amount. Such a trend could be relevant to the rate of the Antarctic ozone depletion.
Lagrangian photochemical modeling studies of the 1987 Antarctic spring vortex: 1. Comparison with AAOE observations
Authors: Jones R. L. , Austin J. , McKenna D. S. , Anderson J. G. , Fahey D. W. , Farmer C. B. , Heidt L. E. , Kelly K. K. , Murphy D. M. , Proffitt M. H. , Tuck A. F. , Vedder J. F.
Published: February 2008

In this paper, results from a photochemical model integrated along ensembles of 8‐day air parcel trajectories are used to simulate the latitude and vertical composition gradients observed from the ER‐2 aircraft during the 1987 Airborne Arctic Ozone Experiment (AAOE). The photochemical model used includes heterogeneous chemical reactions when polar stratospheric clouds are inferred, from local temperature and pressure, to be present. The model results were found to be very sensitive to NOy mixing ratios and the frequency of polar stratospheric clouds (PSCs). Trajectories often showed instantaneous (adiabatic) cooling rates of up to 30 K d−1, with air parcels even at high latitudes spending substantial periods outside modeled clouds. This leads to a photochemical “balance” in the model calculations between the perturbations to the composition caused by the heterogeneous reactions and the restoring effects of HNO3 destruction. For the period of interest (early September 1987), the model was able to simulate well both the latitude gradient of ClO on the 428 K potential temperature surface and the ClO vertical gradient at 72° S. The model simulated well the NO and NOy, concentrations at high latitudes inside the dehydrated, denitrified region, although NO values outside were significantly overestimated. There is evidence from the chlorine and the nitrogen species partitioning in the model that even outside the denitrified, dehydrated region the chemical composition is perturbed. It is argued that heterogeneous processing on type I PSCs has occurred in this outer region, but without denitrification or dehydration. Model results imply that the BrO observations made from the ER‐2 within the dehydrated, denitrified region are consistent with there being approximately 5 parts per trillion by volume of BrOy at 428 K in spring. Within the high ClO region, ozone destruction rates are calculated to exceed 2% d−1 with approximately 80% due to the ClO dimer mechanism.
A new source of horizontal electric fields in the mid‐latitude stratosphere
Authors: Holzworth R. H.
Published: February 2008

Superpressure balloon‐borne instruments that measure the vector stratospheric electric field at latitudes near 45°±10°S reveal several features in fair weather that cannot be attributed to ionospheric, thunderstorm, or other known sources. Over 180 days of electric field, conductivity, and current density data have been taken at the constant altitude of 26 km, using long‐duration balloon flights in the southern hemisphere. Throughout these data the fair‐weather horizontal electric field has a magnitude (10–50 mV m−1) that cannot be due to mid‐latitude ionospheric dynamo action. Furthermore, the fields are highly variable in amplitude, almost turbulent in appearance, while the vector direction steadily rotates in a counterclockwise manner. The period of this rotation is close to the quasi‐inertial wave period for the latitude of the balloon. For these flights the electric field rotation period varies between 14 and 21 hours. Some possible causes that might explain the electric field and current measurements reported herein are discussed.
On dynamics and transport near the polar mesopause in summer
Authors: McIntyre Michael E.
Published: February 2008

Some basic aspects of dynamics and transport in polar regions within one or two scale heights of the summer mesopause are examined, and the implications for local one‐dimensional photochemical modeling of those regions discussed. Included is a simple thought experiment on gravity wave breaking that throws further light on the so‐called “turbulent Prandtl number” question, and related questions. The “downward control” of time averaged, zonally averaged upwelling by gravity wave breaking is noted, and a one‐dimensional modeling strategy suggested in which the transport of water vapor and other constituents from below is characterized by a single parameter, defining a mean upwelling velocity inversely proportional to the mean mass density. It is suggested that, at and below noctilucent cloud altitudes, vertical mixing should be altogether neglected.
Cloud field classification based upon high spatial resolution textural features: 2. Simplified vector approaches
Authors: Chen D. W. , Sengupta S. K. , Welch R. M.
Published: February 2008

The huge volume of data being collected in global climate studies makes it necessary to develop efficient automatic data analysis methods. While most cloud classification algorithms are based upon multispectral signatures, there is growing use of textural features. The results given in Part 1 of this study demonstrate that textural features computed from the Gray Level Cooccurrence Matrix (GLCM) approach produce high cloud classification accuracies. The present study compares classification results derived from two vector approaches, Sum and Difference Histogram (SADH) and Gray Level Difference Vector (GLDV), with those from the GLCM approach. It is found that the SADH approach produces accuracies equivalent to those obtained using GLCM, but with greater ability to resolve error clusters; also, there is a 30% savings in run time and a 50% savings in storage requirements. The GLDV approach suffers a slight degradation in classification accuracy but has a 40% savings in run time and an 87% savings in storage requirements. Textural features are not highly sensitive to moderate variations in cloud threshold selection. However, the whole cloud, rather than only the brightest portions of the cloud, produce the highest classification accuracies. A very important result is that spatial information content and classification accuracy are preserved even at lower radiometric resolutions with effective gray levels of 16. means that significantly low resolution digitized versions of satellite imagery retain essentially the full spatial information content of the original digital data. Substitution of digitized imagery can significantly reduce the expense of many remote sensing studies.
Clear‐sky vertical profiles of trace gases as influenced by upstream convective activity
Authors: Pickering Kenneth E. , Dickerson Russell R. , Luke Winston T. , Nunnermacker Linda J.
Published: February 2008

We describe an experiment that shows the importance of convection in long‐range transport of air pollutants and in enhancing upper tropospheric ozone production. A research flight was conducted during clear‐sky summertime conditions over north‐central Oklahoma and central Kansas to measure vertical profiles of CO, O3, reactive nitrogen compounds, and a variety of meteorological variables. Correlation analyses were conducted on the profiles of pairs of the trace gases to infer sources of these gases. Areas of ozone predominantly produced photochemically in the troposphere and smaller areas with ozone of primarily stratospheric origin were identified. Meteorological analyses indicated that increased CO and NOy concentrations found at high altitude were carried by convective clouds from the boundary layer to the upper troposphere. High levels of ozone precursors were still discernable a great distance (600 km) downwind. Net O3 production was computed for the lower and upper troposphere, while net destruction was computed for the midtroposphere, where NO levels were very low.
An infrared radiative scheme for the numerical models of weather and climate
Authors: Shibata K. , Aoki T.
Published: February 2008

An accurate but computationally fast scheme of the infrared radiative transfer is developed based upon the multiparameter random model to be used in climate and numerical prediction models. The entire infrared spectrum is divided into four spectral regions, 20–550, 550–800, 800–1200, and 1200–2200 cm−1, including the H2O rotation and 6.3‐μm bands, the CO2 10‐ and 15‐μm bands, and the O3 9.6‐ and 14‐μm bands. The continuum absorption of H2O is incorporated in all the spectral regions. The mean diffuse transmittances in each region for homogeneous paths are calculated by a line‐by‐line method, and they are approximated with a simple exponential function which contains 10 or 12 parameters. The transmittance calculations through inhomogeneous atmospheres are carried out by the modified Godson method, which independently uses the Godson method to the line and wing parts of the transmission function. This method is found to be more economical in computation time than the current Godson method, keeping the same precision. The errors in heating rates calculated by this scheme for the model atmospheres are less than 0.3 K/d in the troposphere and stratosphere, and less than 0.8 K/d above the stratopause. The errors in radiative fluxes are less than 0.8 W/m2 both at the Earth's surface and the top of the atmosphere. It is also shown that the accuracy of this scheme does not degrade when the CO2 concentration is doubled. It is pointed out that the inclusion of the H2O continuum in 20–550 cm−1, O3 14 μm in 550–800 cm−1, and CO2 10μm in 800–1200 cm−1 significantly affects radiative flux and cooling rate.
Measurements of size and composition of particles in polar stratospheric clouds from infrared solar absorption spectra
Authors: Kinne S. , Toon O. B. , Toon G. C. , Farmer C. B. , Browell E. V. , McCormick M. P.
Published: February 2008

The attenuation of solar radiation between 1.8‐ and 15‐μm wavelength was measured with the airborne (DC‐8) Jet Propulsion Laboratory Mark IV interferometer during the Airborne Antarctic Ozone Expedition in 1987. The measurements not only provide information about the abundance of stratospheric gases, but also about the optical depths of polar stratospheric clouds (PSCs) at wavelengths of negligible gas absorption. The spectral dependence of the PSC optical depth contains information about PSC particle size and particle composition. Thirty‐three PSC cases were analyzed and categorized into two types. Type I clouds contain particles with radii of about 0.5 μm and nitric acid concentrations greater than 40%. Type II clouds contain particles composed of water ice with radii of 6 μm and larger. Cloud altitudes were determined from 1.064‐μm backscattering observations of the airborne (DC‐8) Langley DIAL lidar system. Based on the PSC geometrical thickness, both mass and particle density were estimated. Type I clouds typically had visible wavelength optical depths of about 0.008, mass densities of about 20 ppb, and about 2 particles/cm3. The observed type II clouds had optical depths of about 0.03, mass densities of about 400 ppb mass, and about 0.03 particles/cm3. The detected PSC type I clouds extended to altitudes of 21 km and were nearly in the ozone‐depleted region of the polar stratosphere. Although PSC type II clouds under different temperature regimes may extend to similar high altitudes, the observed type II cases during September were predominantly found at altitudes below 15 km. Some of these low‐altitude clouds may have been associated with cirrus clouds that extended well below the DC‐8 aircraft. Simultaneous spectroscopic measurements of nitric acid vapor within the polar vortex (Toon et al., this issue) display lower concentrations in the presence of PSC type I clouds, the deficit being close to the amount of solid nitric acid inferred from the optical depths of these PSCs. This further supports the view that the type I PSCs contain frozen nitric acid.
Infrared aircraft measurements of stratospheric composition over Antarctica during September 1987
Authors: Toon G. C. , Farmer C. B. , Lowes L. L. , Schaper P. W. , Blavier J.‐F. , Norton R. H.
Published: February 2008

The Jet Propulsion Laboratory Mark IV interferometer recorded high‐resolution, infrared solar spectra from the NASA DC‐8 aircraft during flights over Antarctica in September 1987. The atmospheric absorption features in these spectra have been analyzed to determine the burdens of O3, NO, NO2, HNO3, ClNO3, HCl, HF, CO2, CH4, N2O, HCN, CO, H2O, CFCl3, and CF2Cl2. The results show a “collar” of high HNO3 and ClNO3 surrounding a “core” in which the burdens of these and of HCl and NO2 are very low. Clear increases in the burdens of HF and HNO3 were observed during the course of September in the vortex core. HCl and NO2 exhibited smaller, less significant increases. The burdens of the tropospheric source gases, N2O, CH4, HCN, CFCl3, CF2Cl2, CO, and H2O, were observed to be much smaller over Antarctica than at mid‐latitudes. This, together with the fact that HF over Antarctica was more than double its mid‐latitude value, suggests that downwelling had occurred.
Instrument description of the airborne microwave temperature profiler
Authors: Denning Richard F. , Guidero Steven L. , Parks Gary S. , Gary Bruce L.
Published: February 2008

The microwave temperature profiler (MTP) is a passive microwave radiometer installed in the NASA ER‐2 aircraft and used to measure profiles of air temperature versus altitude. It operates at 57.3 and 58.8 GHz, where oxygen molecules emit thermal radiation. Brightness temperature is measured at a selection of viewing elevation angles every 14 s. MTP was the only remote sensing experiment aboard the ER‐2 during the Airborne Antarctic Ozone Experiment. This paper describes hardware, calibration, and performance aspects of the MTP.
Stratospheric N2O5 profiles at sunrise and sunset from further analysis of the ATMOS/Spacelab 3 solar spectra
Authors: Rinsland C. P. , Toon G. C. , Farmer C. B. , Norton R. H. , Namkung J. S.
Published: February 2008

The detection of N2O5 in the stratosphere was reported by Toon et al. (1986) and Toon (1987) based on measurements of the absorption by the N2O5 bands at 1246 and 1720 cm−1 in solar occultation spectra recorded at sunrise near 47°S latitude by the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment during the Spacelab 3 (SL3) shuttle mission (April 29 to May 6, 1985). In this work we report additional measurements and analysis of stratospheric N2O5 derived from the ATMOS/SL3 spectra. The primary results are the detection and measurement of N2O5 absorption at sunset in the lower stratosphere, the inversion of a precise (∼10%) N2O5 sunrise vertical distribution between 25.5‐ and 37.5‐km altitude, and the identification and measurement of absorption by the N2O5 743‐cm−1 band at sunrise. Assuming 4.32×10−17 and 4.36×10−17 cm−1/molecule cm−2 for the integrated intensities of the 1246‐ and 743‐cm−1 bands, respectively, at stratospheric temperatures, retrieved volume mixing ratios (VMRs) in parts per billion by volume (ppbv) at sunrise (47°S latitude) are 1.32±0.34 at 37.5 km, 1.53±0.35 at 35.5 km, 1.63±0.36 at 33.5 km, 1.60±0.34 at 31.5 km, 1.43±0.30 at 29.5 km, 1.15±0.24 at 27.5 km, and 0.73±0.15 at 25.5 km. Retrieved VMRs in ppbv at sunset (31°N latitude) are 0.13±0.05 at 29.5 km, 0.14±0.05 at 27.5 km, and 0.10±0.04 at 25.5 km. Quoted error limits (1 sigma) include the error in the assumed band intensities (∼20%). Within the error limits of the measurements the inferred mixing ratios at sunrise agree with diurnal photochemical model predictions obtained by two groups using current photochemical data. The measured mixing ratios at sunset are lower than the model predictions with differences of about a factor of 2 at 25‐km altitude.
Statistical precipitation cell parameter estimation using passive 118‐GHz O2 observations
Authors: Gasiewski A. J. , Staelin D. H.
Published: February 2008

The use of passive 118‐GHz O2 observations of rain cells for precipitation parameter estimation is demonstrated by a nonlinear statistical cell top altitude retrieval operator. The retrieval operator consists of a Karhunen‐Loève (KL) transformation followed by a rank reduction, a nonlinear operator, and a linear minimum mean square error estimator. Statistics were derived from an ensemble of 118‐GHz convective rain cell core observations over land, along with coincident estimates of the cell top altitude obtained by optical stereoscopy. The observations were made using the millimeter‐wave temperature sounder (MTS) scanning spectrometer aboard the NASA ER‐2 high‐altitude research aircraft during the Genesis of Atlantic Lows Experiment (GALE) and the Cooperative Huntsville Meteorological Experiment (COHMEX), 1986. The retrieval operator applied to MTS data yielded an rms discrepancy of 2.0 km for a combined cumulus, mature, and dissipating cell observation set and 1.6 km for the cumulus‐only set. Comparison of the 118‐GHz cell top altitude retrieval with coincident radar reflectivity data for a case of mature convection indicates that the 118‐GHz altitude retrieval tracks the 5‐ to 10‐dBZ reflectivity level over weak precipitation and the 20‐dBZ reflectivity level over strongly convective cores. A slight improvement of the 118‐GHz altitude retrieval discrepancy to 1.5 km rms is facilitated for the cumulus‐only set by including information on the atmospheric temperature profile and cell size from the 118‐GHz observations. Because of the ability of downward viewing microwave channels to probe beneath cloud tops and the sensitivity of these channels to precipitation, the 118‐GHz cell top altitude retrievals provide a more meaningful measure of the precipitation altitude than do optical or infrared retrievals. By using the KL decomposition followed by a nonlinear transformation, it is shown that 2 to 3 observable degrees of freedom exist in the 118‐GHz rain cell core perturbation spectra, implying that at least one other meteorological parameter, independent of cell top altitude, can be retrieved from these data.
Atmospheric and depositional environments traced from unique chemical compositions of the snow over an inland high plateau, Antarctica
Authors: Kamiyama Kokichi , Ageta Yutaka , Fujii Yoshiyuki
Published: February 2008

Surface snow samples from the inland high plateau, East Queen Maud Land, Antarctica, show unique chemical characteristics. They are characterized by high acidity accompanying the high electrical conductivity, so that the hydrogen ion is the dominant ion, coupling with chloride and nitrate ions. The chemical composition differs sharply from sea salts. These characteristics appear more clearly than previously reported in Antarctica and are most strongly developed in snow samples from the high region. The tritium content increases in the inland high area, especially in the region higher than 3600 m asl (above sea level), which corresponds to the region where the effects of katabatic wind have vanished in the glaciological observations. The highest tritium content occurs in the vertical profile at a snow pit (3761 m asl, 77°00′S, 35°00′E), which corresponds to the snow deposition in 1966. The concentration is the highest ever reported in Antarctica and is almost as high as the one observed in the precipitation in the inland region of North America, which is the highest value ever reported in the world. All the results suggest that most of the ions contained in snow samples from the inland high plateau, especially higher than 3600 m asl, are not brought directly through the troposphere from the sea around Antarctica but from the higher atmosphere and that they are under the influence of the physicochemical reactions occurring there.
Chemistry of marine aerosols over the western Pacific Ocean
Authors: Zhou Ming yu , Yang Shao jin , Parungo Farn P. , Harris Joyce M.
Published: February 2008

During the first cruise operated by the United States of America and the People's Republic of China cooperative program, from December 12, 1985, to February 21, 1986, aerosol samples were collected with a KA‐200 Anderson cascade impactor and a KB‐120 sampler. Neutron activation analysis was used to determine the elemental composition of the aerosols. Maximum mass concentrations of sea‐salt elements (Na, Cl, and Br) were found in the size range 3.3–4.7 μm. The “bulk” enrichment factor for Cl in aerosols, relative to Na in seawater, was close to unity, but a very pronounced depletion was found for Br. The enrichment factor for Cl in different size ranges decreased with increasing particle size and for Br had a U‐shaped curve. The size distributions for Fe, Al, and Sc over the remote ocean and over the ocean area close to the Asian continent were quite different. Aerosols over the western Pacific showed significant enrichment of Sb and Se, relative to Fe. Some characteristics of marine aerosols are discussed as they relate to long‐range transport of crustal elements and pollution elements from the Asian continent to the western Pacific.
Mesoscale precipitation patterns in extratropical cyclones and implications for cyclone development
Authors: Tweedy David L.
Published: February 2008

Analysis of the surface distribution of precipitation associated with intense extratropical cyclones reveals elongated maxima aligned with the steering flow. Rapidly intensifying cyclones create precipitation maxima which are better defined and contain more moisture than weaker cyclones. The distributions are associated with the formation of a precipitation generating zone (PGZ) aligned with the midtropospheric jet ahead of and parallel to the surface cold front extending southward from the surface low. These zones tend to move along their axes and are host to the most frequent and intense convective activity in the extratropical cyclone. Hourly rain gage measurements at sites in their path indicate an average of three precipitation peaks in 16 storms studied, although radar echoes disclose that many mesoscale structures with high reflectivity are simultaneously active. It is hypothesized that formation of such zones is most pronounced when momentum transport out of the jet increases the advection of warm moist air at low levels, thereby sustaining or increasing convective instability. In this context, the PGZ becomes the dominant feature of the extratropical cyclone and is crucial to intensification.
Stabilization functions of unforced cumulus clouds: Their nature and components
Authors: Ramirez Jorge A. , Bras Rafael L. , Emanuel Kerry A.
Published: February 2008

Is there an intrinsic characteristic of free moist atmospheric convection that induces a particular type of space‐time structure within cloud fields? What is the expected nature of the spatial distribution of cumuli within unforced cumulus cloud fields? This paper is one of two in this collection that addresses these fundamental questions. The thermodynamic effects of convection are quantified as functions of changes of convective available potential energy (CAPE) induced by the convective overturning. The time rate of change of CAPE is parameterized in terms of a kernel of influence or stabilization function. A three‐dimensional cloud model is used to infer and quantify stabilization functions by performing single‐cloud experiments. Measured stabilization functions are positive everywhere, decreasing away from the cloud center. Stabilization functions are decomposed into various thermodynamic contributions involving pressure, temperature, and moisture changes in the boundary layer and above. It is observed that the major contribution to the environmental stabilization comes from the drying of the planetary boundary layer induced by subsidence. The thermodynamic effect of nonprecipitating and precipitating convection is to reduce CAPE in the surrounding environment and hence reduce the conditional probability of further convection nearby. A new hypothesis with respect to the spatial distribution of cumuli is postulated. The inhibition hypothesis states that, under completely homogeneous external conditions and assuming a spatially random distribution of cloud‐trigering mechanisms, the spatial distribution of cumuli in the resulting cloud field must be regular, as opposed to either random or clustered, because cumulus clouds tend to reduce the available energy for convection, thereby inhibiting further convection nearby.
A statistical model of extreme storm rainfall
Authors: Smith James A. , Karr Alan F.
Published: February 2008

A model of storm rainfall is developed for the central Appalachian region of the United States. The model represents the temporal occurrence of major storms and, for a given storm, the spatial distribution of storm rainfall. Spatial inhomogeneities of storm rainfall and temporal inhomogeneities of the storm occurrence process are explicitly represented. The model is used for estimating recurrence intervals of extreme storms. The parameter estimation procedure developed for the model is based on the substitution principle (method of moments) and requires data from a network of rain gages. The model is applied to a 5000 mi2 (12,950 km2) region in the Valley and Ridge Province of Virginia and West Virginia.
Estimation of multidimensional precipitation parameters by areal estimates of oceanic rainfall
Authors: Valdés J. B. , Nakamoto S. , Shen S. S. P. , North G. R.
Published: February 2008

The parameters of the multidimensional precipitation model proposed by Waymire et al. (1984) are estimated using the areal‐averaged radar measurements of precipitation of the Global Atlantic Tropical Experiment (GATE) data set. The procedure followed was the fitting of the first‐ and second‐order moments at different aggregation scales by nonlinear regression techniques. The numerical estimates of the parameters using different subsets of GATE information were reasonably stable, i.e., they were not affected by changes of the area‐averaging size, temporal length of the records, and percentage of areal coverage of rainfall. This suggests that the estimation procedure is relatively robust and suitable to estimate the parameters of the multidimensional model in areas of sparse density of rain gages. The use of the space‐time spectrum of rainfall to help in the determination of sampling errors due to intermittent visits of future space‐borne low‐altitude sensors of precipitation is also discussed.