摘要:

Multiple scattering significantly affects atmospheric photodissociation rates, particularly at wavelengths greater than 290 nm. Incorporating the effects of multiple scattering into a one‐dimensional transport‐kinetics model led to dramatic changes in the concentration profiles of many trace species; thus it is important to include multiple scattering when model results are compared with observational data. The effect on model sensitivity of including multiple scattering ranged from no change in ΔO3compared with the pure absorption calculation to a significant increase in ΔO3depending upon the model chemistry. The change in ΔO3due to multiple scattering was small in comparison with the change in ΔO3resulting from varying chemical reaction rates. Variations in surface albedo had little effect on model sens

ISSN:0148-0227    

DOI:10.1029/JC083iC07p03563

年代:1978

数据来源: WILEY

摘要:

The Naval Electronics Laboratory Center (now Naval Ocean Systems Center) made directional measurements of very low frequency sferics in the Union City, Oklahoma, tornadic storm on May 24, 1973. These data verify the interesting findings of two earlier directional sferics studies. Whereas sferics activity in tornado‐producing storms is known to peak near tornado time, all these studies show conclusively that sferics do not originate in the tornado itself but rather throughout the parent thunderstor

ISSN:0148-0227    

DOI:10.1029/JC083iC07p03571

年代:1978

数据来源: WILEY

摘要:

Instrumentation using fast logic circuits and a wide band receiving system (20–80 MHz) to determine direction of arrival of individual VHF electromagnetic impulses from lightning discharge processes was tested successfully at the Kennedy Space Center (KSC) during the 1976 Thunderstorm Research International Program (Trip 76). Time difference of arrival of impulses was used to measure the azimuth from a pair of horizontally spaced antennas and the elevation from a pair of vertically spaced antennas. Although the base line of each pair was only 13.74 m, the time difference measurements were made with 0.4‐ns resolution so that the direction to the source could be determined to an accuracy of ±0.5°. Directions of the individual impulses were represented in real time on a 60° azimuth and 30° elevation format and photographed with a 16‐mm movie camera. Two stations separated by about 17.8 km simultaneously recorded direction data for discharges from over three dozen thunderstorms in the KSC area. A description of this technique and the results of the Florida tests are presented. Analysis of these data revealed that (1) fine structure of lightning discharges could be accurately located and tracked with this technique by using triangulation methods, (2) branching and structure in the discharge processes could be observed, (3) most lightning activity occurred about 5–6 km high, near the −10°C temperature level, and (4) considerable movement of discharge centers occurred as the lightning processes permeated the thunderstorm volume at progression speeds of abo

ISSN:0148-0227    

DOI:10.1029/JC083iC07p03575

年代:1978

数据来源: WILEY

摘要:

The surface aerosol in the NE trade wind region at the island of Sal, Cape Verde Islands, was studied in a comprehensive research program. The knowledge of this aerosol is important in view of the large source represented by the Sahara for mineral particles and the worldwide transport over the Atlantic Ocean and further. Aerosol properties such as total size distribution, mass, sea salt, mineral, organic compound content, water adsorption, optical properties, and soil material were studied in a 3‐week field campaign in summer 1973. The aerosol observed has a particle concentration comparable to that of ‘clean air’ and a total mass like that of ‘polluted air’ (see the definition by Study of Man's Impact on Climate (1971)). Its sea salt content is comparatively small, and its water uptake is somewhat similar to that of pure ammonium sulfate. The content of organic material is similar to that of background aerosols, but the turbidity resembles that of polluted city air. The source strength of the Sahara desert for aerosol particles was estimated from 2 years of optical measurements and found to be greater than was previously

ISSN:0148-0227    

DOI:10.1029/JC083iC07p03585

年代:1978

数据来源: WILEY

摘要:

An attempt was made to predict categories of cold season temperature for 19 cities in the central and eastern United States. Classification equations were developed by using discriminant analysis based on 23 years of historical data (1949–1971) in which the discriminating variables (predictors) are principal components of the mean 700‐mbar heights during November over the northern hemisphere; sea surface temperatures of the eastern North Pacific, eastern tropical Pacific, and North Atlantic oceans; and a southern oscillation index for the fall season. Separate sets of equations were developed for varying duration of the prediction, from 1 to 4 months, and for two or three categories of mean temperature. An independent sample of years was reserved for testing the reliability of the equations. ‘Forecasts’ made by each set of equations were compared with observed categories of mean temperature for five recent winters (1972–1976), not included in the dependent sample. The sets of equations derived for discriminating between above‐ and below‐normal mean temperatures for the 4‐month season (December‐March) and between three groups for the 3‐month winter season (December‐February) performed significantly better than chance expectation. Values of 63% and 45%, respectively, were correct. Additionally, when the persistence forecast category was the same as the forecast category of our model for the December‐March period in the two‐group discrimination, the prediction category was correct 86% of the time over the five test winters. This situation occurred, on the average, for about half the cities in each year. These results indicate that objective methods, using statistical relationships, can be useful for winter temperature predictions, but considerable im

ISSN:0148-0227    

DOI:10.1029/JC083iC07p03601

年代:1978

数据来源: WILEY

摘要:

Langmuir circulations in a wind wave tank have been observed and measured by a variety of methods including dye patterns and floating surface tracers. On the basis of measurements of cellular wavelength λcas a function of surface wavelength λwand depthHa tentative functional relation for the dependence of λc/Hupon λw/His proposed. The experiments clearly imply that the waves play an important role in the mechanism of formation of the Langmuir circulations but that the depth of the layer has a significant modifying influence. On the basis of certain ‘rake’ experiments and other indirect observations it is proposed that when λw/H<1, the primary scale of Langmuir circulations, related to λw, transfers energy to a larger scale that is commensurate with the depth such that λc/H≃ 2. Under these circumstances, two distinct scales of Langmuir circulations may exist si

ISSN:0148-0227    

DOI:10.1029/JC083iC07p03617

年代:1978

数据来源: WILEY

摘要:

Changes in heat content of the upper ocean for two adjacent 1° × 1° areas (56°–57°N, 164°–166°W) in the eastern Bering Sea were investigated with the data from three quasi‐synoptic surveys in June, August, and September 1976. Data from current meters indicated that the net flow was very weak, and advection of heat was neglected. The mean local change of heat content for the two areas for the June–August period was 0.20 cal cm−2min−1; during August–September the local change was 0.06 cal cm−2min−1. Mean surface exchange for the two periods was estimated by recently evaluated empirical formulas (using data from satellite photographs and weather reports) to obtain values of 0.20 and 0.05 cal cm−2min−1. The data also suggested that the gain of heat through horizontal diffusion was not more than 0.01 cal cm−2min−1. Thus for both periods there was excellent agreement between the local change of heat and the net surface exchange. It appears that net radiation is typically the dominant heat flux affecting much of the eastern Bering Sea in summer, although in early fall, evaporation starts to assume importance. This region is quite unusual in that heat advection and diffusion have little effect on the heat balance. Lack of motion allows the effects of various p

ISSN:0148-0227    

DOI:10.1029/JC083iC07p03635

年代:1978

数据来源: WILEY

摘要:

A simple model of heat transport through young sea ice is combined with climatological data on air temperatures and incoming radiation in the central Arctic to predict how each component of the surface heat balance is affected by changes in ice thickness. Results indicate that during the cold months the net heat input to the atmosphere from ice in the 0‐ to 0.4‐m range is between 1 and 2 orders of magnitude larger than that from perennial ice. Once the ice exceeds a meter in thickness, there is little change in any of the heat fluxes as the ice thickens. Although both the amount of absorbed shortwave radiation and the emitted longwave radiation depend on ice thickness, it is the turbulent fluxes which undergo the largest changes. The rate of heat exchange over thin ice is shown to be extremely sensitive to snow depth and assumed boundary layer temperatures. It is concluded that with the present ice thickness distribution in the central Arctic, total heat input to the atmospheric boundary layer from regions of young ice is equal to or greater than that from regions of open water or thick

ISSN:0148-0227    

DOI:10.1029/JC083iC07p03646

年代:1978

数据来源: WILEY

摘要:

It has been known for some time that a frontal zone exists in the slope water, which lies between the Gulf Stream and the shelf break off Nova Scotia, where the temperature jumps from 7°C to 11°C and the salinity from 34.8‰ to 35.2‰ in a horizontal distance of a few kilometers. Data taken from this area with a yo‐yoing CTD (conductivity‐temperature‐depth probe) have been analyzed and show that at the front the two water masses interleave with a vertical scale of the order of 10 m. The interleaving layers are coherent for several kilometers in the cross‐frontal direction and for at least 17 km in the long‐frontal direction. The data suggest that considerable vertical mixing, through double diffusive processes, and horizontal mixing, through interleaving processes, occur in the frontal zone. Vertical eddy coefficients of 8 × 10−4m2/s for heat and 3 × 10−4m2/s for salt are calculated for the water column between 40 and 160 m at the front by using Turner's (1965, 1967) formulae to calculate the double diffusive fluxes across the interfaces of the layers. The horizontal eddy diffusion coefficients at the front are calculated to be 10 m2/s for heat and 9 m2/s for salt. The estimated annual vertical heat flux at the front into the coastal water is 15% of the solar input to the shelf water, and the salt flux is 10% of that needed to produce shelf water from the freshwater runoff. Horizontal mixing across the front is shown to be large enough to explain the observed annihilation of the Labrador Slope Water during the time that it takes to travel along the Scotian Shelf. The high vertical mixing at the front may provide a significant v

ISSN:0148-0227    

DOI:10.1029/JC083iC07p03659

年代:1978

数据来源: WILEY

摘要:

Trace gas measurements (222Rn, CO, CH4), weather satellite images, and conventional meteorological observations established the existence of a pronounced land and sea breeze regime at the Sepik River coast. Its interaction with the synoptic wind field was evaluated. Considerable natural variability of atmospheric CO and CH4was observed. CCl4behaved similarly to man‐made CCl3

ISSN:0148-0227    

DOI:10.1029/JC083iC07p03672

年代:1978

数据来源: WILEY