Showing papers in "Theoretical and Applied Climatology in 1987"

Thermal comfort of man in different urban environments

Abstract: On July 29, 1985, a hot summer day, biometeorological measurements were performed simultaneously in three different urban structures within the city of Munich and in the trunk space of a nearby tall spruce forest. Based on the results of these experiments the following thermophysiologically relevant biometeorological indices were calculated: Predicted mean vote, skin wettedness and physiologically equivalent temperature. These three indices are derived from different models for the human energy balance. They allow the assessment of the thermal components of the microclimates at the selected sites with regard to application in urban planning. The results quantitatively show the great heat stress in the urban structure “street canyon, exposed to south”, whereas in the “trunk space of the tall spruce forest” there is nearly an optimal climate even on hot summer days. Between these extremes the results for “street canyon, exposed to north” show a little higher heat load than for “backyard with trees”.

Recent changes in Phoenix, Arizona summertime diurnal precipitation patterns

Abstract: Summertime diurnal precipitation patterns for Phoenix, Arizona are analyzed for the period 1954 through 1985. Although the mean precipitation amounts and frequencies for the entire summer monsoon season have not shown any significant effects from the rapidly developing urban heat island, diurnal patterns have displayed substantial changes in the recent period of explosive population growth. During the most recent 16 years, late afternoon and evening storms have become more frequent and produce greater rainfall totals. Sharp declines are noted in the frequency of rain events between midnight and noon; especially large drops occur in the rainfall amounts between 9.00 and 12.00 MST. These findings appear to be consistent with several mechanisms proposed to explain the unusual diurnal character of the summertime rainfall in the Phoenix, Arizona area.

A comparison of the chemical composition of fog and rainwater collected in the Fichtelgebirge, Federal Republic of Germany, and from the South Island of New Zealand

Abstract: We measured ionic compounds in rain and fog at two remote sites in the South Island of New Zealand and at two sites in the Fichtelgebirge, F. R. of Germany. In the Fichtelgebirge high concentrations of H3O+, NO 3 − , SO 4 2− and NH 4 + indicate an anthropogenic impact, whereas in New Zealand concentrations were generally very low except for seasalt derived ions such as Na+, Cl− and Mg2+ at one site near the coast which receives precipitation from maritime sources. Remarkable differences occur in the acidity of hydrometeors in New Zealand and the Fichtelgebirge. The low pH values of the Fichtelgebirge (pH ≈ 4.2) are due to an excess of strong mineral acids, whereas the acidity of rain and fog in New Zealand is controlled by dissolved CO2 (pH ≈ 5.6). In the Fichtelgebirge, acidity in fog is much higher than in rain, whereas no difference could be observed in New Zealand due to marine influences and the lack of strong mineral acids. Rain of different trajectories of air flow in New Zealand is accompanied by a wide range of ionic concentrations.

Contributions to the knowledge of the fluctuations of the Dead Sea level

Abstract: After an extended critical evaluation of a wealth of historical sources, the history of the Dead Sea level fluctuations is reviewed with accuracy since 1800 (Klein, 1961). Earlier data since 1100 AD based on landmarks and tree-ring data (Klein, 1982, 1985) are also summarized. Since 1930 interannual fluctuations are compared with area-averaged rainfall data from the western and eastern part of the catchment, as well as with rainfall records from Jerusalem and Amman. Correlation analysis lead to two linear regression equations for the period 1930/1931–1962/1963 (undisturbed) and 1963/1964–1983/1984 after diversion of water from Lake Tiberias and Jordan River. From these equations, the average annual effect of this diversion results to about −24 cm; in very moist years this effect is insignificant.

Comparison of penman and thornthwaite methods of estimating potential evapotranspiration for indian conditions

Abstract: Thornthwaite's (1948) empirical method of estimating potential evapotranspiration (PE) has been preferred by several scientists in India to Penman's (1948) theoretical combination approach, because of the former's simplicity. However, in view of the doubts expressed in various quarters regarding the applicability of Thornthwaite's method for monsoon climates, a comparison is made of the performance of these two methods over different parts of India, using about 26 years of data at 15 stations spread over the country. Various aspects of the manifestations and their differences are presented. It is found that Thornthwaite's method gives considerably higher estimates ofPE and shows lower inter-annual variability than Penman's method during the southwest monsoon season. A systematic annual variation of the difference between the two methods is also noticed which is found to be mainly due to the actual vapor pressure and sunshine duration included in Penman's method.

Use of a synoptic classification scheme to define seasons

Abstract: This paper presents a synoptic surface weather map classification scheme, and uses the categorization technique to meteorologically define seasons. Winter is defined as that period of the year in which a location is most frequently poleward of the polar front, while summer occurs when the site is most commonly equatoward. Fall and Spring are the transition periods when, respectively, increasingly more frequent and less frequent periods of time poleward of the polar front occur. Using 10 years of data, the application of this definition of seasons to the Gulf and Atlantic coasts of the United States is presented. While the frequency of the specific types of major synoptic weather features varied with latitude, the meteorological definitions of season are comparatively invariant with latitude (differing by no more than a month) for this geographic area. Using the meteorological definitions of season, the average winter for this region occurs from late October or early November to late March or early April. Summer is from late May to early June until late August or late September.

Homogeneity, spatial correlation and spectral variance analysis of long European and North American air temperature records

Abstract: Recently the authors have collected 242 surface air temperature records all over the world covering at least the 1881–1980 observation period. In this paper results of the statistical analysis of 118 European and 64 North American records are presented. As a first step the homogeneity of these records is tested using different statistical techniques. Secondly, the spatial correlations are assessed. These correlations appear to increase with the latitude and continentality of the stations. Finally, the spectral variance is analyzed using the conventional autocorrelation and the maximum entropy technique. Moreover, these techniques are applied in a “dynamic” way (moving with time). On the basis of this “integrated” and “dynamic” analysis the spatial pattern of spectral variance is characterized.

On the estimation of long-wave radiation flux from clear skies

Abstract: Data from measurements of long-wave radiation at Barcelona were used to test the validity of several methods for computing this component of the radiation balance in clear sky conditions. Two types of formulae, the analytically derived formulae of Swinbank and Brutsaert 1 and 2 and the empirically obtained formulae of Brunt, Idso and Jackson and Idso 1 and 2 were used in the test. Most of these methods are derived for a particular location and utilize local empirical coefficients. However, there are several which have been considered more universal. Estimates by the two methods give approximately the same value when the screen level air temperature is above 0°C. In addition, the test for temperatures below 0°C shows several discrepancies between the observed and estimated values of long-wave atmospheric radiation. This fact suggests that modifications may be needed for both analytical and empirical formulae. However, since we have few measurements in the temperature regime below 0°C, this statement cannot be justified as a conclusion of this study.

Rainfall teleconnections in northern and northeastern Africa

Abstract: In comparison to the time-series of rainfall in the Sahel-Sudan belt, given by several authors, runoff series from the Blue Nile and Atbara river (representing rainfall in western Ethiopia) and rainfall data from southern Somalia were described. No cross-correlation between Somalia and other series was found; the cross-correlation between the Sahel-Sudan belt and Ethiopia became significant only after about 1950. Simultaneously the persistence of rainfall anomalies in the Sudan-Sahel belt, including those of the Republic Sudan, exceeded the low values recorded until 1940. Since the vertically integrated water vapour transport over the belt of tropical summer rains came from SSW, i.e. from the semihumid to humid region of the northern Zaire basin, a possible contribution of biogeophysical effects due to manmade conversion of natural vegetation into arable lands ought to be discussed as a factor contributing to the increasing persistency and spatial coherency.

A Study of the Seasonal Variation of Rain-Days of Different Categories in Nigeria in Relation to the Miller Station Types for Tropical Continents

Abstract: The seasonal distribution of rain-days of different categories, namely: rain-days of light showers, rain-days of moderate showers and rain-days of heavy rainfall, were analysed for Nigeria in this study. The areal distribution of the seasonal variation types identified for each rainday category was then examined in relation to the zonal pattern of station types derived by Miller (1971) for tropical continents. Both the areal distribution of the seasonal variation types depicted by rain-days of moderate rainfall and by rain-days ofheavy rainfall were found to conform fully to Miller's theoretical model for the country. Only the areal distribution of the seasonal variation types depicted by rain-days of light rainfall was found not to conform to this theoretical model.

Long-range seasonal rainfall forecast for Zimbabwe and its relation with El-Niño/Southern Oscillation (ENSO)

Abstract: This investigation shows a fairly definite connection between the mean seasonal rainfall in a rainy season and the ground minimum temperature in the preceding two winter seasons in Zimbabwe. The latter is considered to represent the intensity of the “over land high” over Botswana and the corresponding degree of cooling of the subcontinent during the winter season. This “over land high” is related to the east-west overturning Walker Circulation. This relationship emphasizes that the rainfall variability over Zimbabwe is strongly linked to the ENSO phenomenon.

Clear sky ultraviolet-B radiation in the English Midlands: A comparison of measured and modelled values

Abstract: Spectral measurements were made of solar ultraviolet-B (UVB) irradiance at Sutton Bonington (52° 50′N, 1° 15′W) under cloudless skies using a Licor LI 1800 scanning spectroradiometer. The finite bandpass of the instrument and the steep shape of the UVB spectra caused overestimation of irradiance at short wavelengths. Spectra were corrected mathematically for these effects. The corrected spectra were compared to estimates of global UVB irradiance as a function of zenith angle and amount of ozone. Comparisons were made at 300 nm, 310 nm and 320 nm. Estimates were significantly greater (p = 0.05) than the measurements except at 320 nm where differences were not significant. The differences may have been the result of overestimation of UVB at short wavelengths, since some of the assumptions on which the estimates were based may not be valid for Sutton Bonington conditions.

Further evidence of the 11-year solar cycle in stratospheric-lower mesospheric ozone and temperatures

Abstract: The response of the stratosphere and lower mesosphere to the quasi-eleven-year solar activity cycle (indicated by sunspot variations) was studied using temperature data obtained from rockets which are mostly based on a datasonde system throughout the decade 1969–1978. It is suggested that the highest correlation between the long-term stratospheric-lower mesospheric temperature fluctuations and the Zurich sunspot number is obtained with a time lag of one year (sun leading). A comprehensive insight into the actual process accounting for the observed correlation would be gained from improved observational data, including observations of solar ultraviolet behavior.

Planetary radiation budget over North Africa from satellite data

Abstract: The large desert regions over North Africa are of particular importance to our climate and are therefore modelled numerically as part of sensitivity studies. The result of these models needs verification, but diagnostic studies of atmospheric energetics also require accurate values of the radiation budget at the upper boundary of the climate system. The radiation “anomaly” above Northern Africa is now established from various satellite data. However, it is suspected that there are serious errors caused in particular by angular and temporal sampling. A sample of NIMBUS-7 ERB—measurements (16.–30. June 1979) was therefore reanalysed, including the missing diurnal cycle which was reconstructed from the corresponding METEOSAT measurements. These more complete data on diurnal cycles change the results on outgoing thermal fluxes and net radiation by up to almost 60 Wm−2, thus changes of the sign of net radiation also occur over several regions.

On the mesoscale distribution of precipitation deficits

Abstract: Minor shifts in the pattern of the general circulation frequently result in the development of a mosaic of localized wet and dry patches, creating regions of mesoscale drought. A method of identifying the spatial pattern of such droughts is developed, using the conditional probability of adjacent stations experiencing precipitation deficits simultaneously. The method was tested using seasonal data for the eastern portion of North Carolina, U.S.A. The resulting patterns can be related to the synoptic climatology of the area. Summer reveals numerous small areas of precipitation deficit, while the other seasons have larger deficit areas which reflect changing depression tracks, coastal influences, and rainshadow effects. Comparison of the results with the commonly used Palmer Drought Severity Index indicates that the latter is an appropriate measure only when drought is widespread, and cannot be used to identify mesoscale droughts. The present method allows identification of areas prone to mesoscale drought, suggests causal mechanisms, and provides a basis for monitoring the development of such droughts.

Photosmog modeling using two reaction mechanisms of different complexity

Abstract: This paper deals with box model simulations of photochemical smog formation caused by motorcar emissions. Diurnal variations of emission rates are calculated on the basis of assumed traffic cycles. For the description of photochemical transformations, two reaction mechanisms of different complexity are applied. Simulation results achieved with the reaction mechanism of Atkinson, Lloyd and Winges (ALW mechanism) show the influence of air temperature and of CO and SO2 emissions on the ozone formation. Calculations for various assumed compositions of the emitted hydrocarbons using the ALW mechanism reveal that the diurnal variation of ozone strongly depends on the subdivision of the hydrocarbon emissions. Predictions of the ozone formation using the compact mechanism of Eschenroeder and Martinez (EM mechanism) agree fairly well with corresponding diurnal concentration profiles predicted by the ALW mechanism. Hence, if the ALW mechanism is valid, the EM mechanism may be used to obtain a reasonable impression of the diurnal variation of ozone in an urban airshed. In particular, inclusion of the EM mechanism in complex three-dimensional dispersion models might allow the combined description of dispersion and photochemical transformation of pollutants in urban areas.

Surface energy budget model of a cave

Abstract: A simple surface energy budget model is developed and validated for an aboriginal rock art site in Western Australia. The thermal regime of the rock face is strongly dependent on the sky view factor for a vertical surface element and the sensible and latent heat fluxes are shown to be relatively unimportant. Using climatological data, the model is extended to form the basis for appropriate environmental management and conservation of the rock art.

A further note on extreme monsoonal rainfall deficits in India

Abstract: In a previous paper, maps were provided of the extreme monsoonal rainfall deficits likely to occur somewhere within individual Standard Meteorological Sub-Divisions in India. The present paper extends this study to similar evaluations for areas of radius 150 km around each of the 306 stations used in the previous study. Maps are presented of percentage rainfall deficits (or percentage of average values) with return periods of 2, 5, 10 and 50 years, and of the spatial pattern of return periods for deficits of 40%, 50%, 60% and 70% below the average. In addition, there are graphs for 25 stations displaying the relationships between deficit intensity and return period.

Field estimates of alfalfa evapotranspiration by energy balance-resistance modelling

Abstract: Estimates of mean daily evapotranspiration using the aerodynamic resistance-surface energy balance (ARSEB) model of Monteith were obtained for three periods during 3 September (day of year 246) to 15 November (day 319) 1983 in an alfalfa (Medicago sativa L.) field in central Arizona near Coolidge. These estimates were compared with Penman method estimates, within situ soil water balance (SWB) method estimates, and with long-term soil water depletion-based estimates of evapotranspiration for central Arizona. The SWB method estimates were obtained from soil moisture data collected to 1.5 m depth at 60 field sites, and to 1.8 m depth at 16 of the 60 sites. During relatively wet field conditions in September, daily estimates from the ARSEB method were on average about 19% to 23% lower than estimates from the Penman and SWB methods, respectively. However, for these wetter conditions, soil moisture data were only collected to 1.5 m depth. Thus, the SWB method may have overestimated evapotranspiration because drainage below the crop root zone was not measured. During drier conditions later in the season, ARSEB estimates of daily evapotranspiration were on average about 5% greater than Penman estimates. Also, ARSEB estimates were on the average about 24% to 35% greater than SWB method estimates. Agreement was good between ARSEB method estimates and long-term alfalfa evapotranspiration estimates by Erie et al. (1981) for central Arizona.

Comparison of environmental radioactivities at Chandigarh and Tokyo

Abstract: By comparing the natural activities in biosphere and building materials at Chandigarh and Tokyo, we found that at both these places, contamination due to nuclear bomb explosions and nuclear power plants is absent. However, in earth and building materials, members of the radioactive thorium series and40K are in large quantities at Tokyo compared to Chandigarh. The relative concentration of radioactive uranium is comparable at both these places.

The effects of aerosols on the response of a two-dimensional zonally-averaged climate model

Abstract: The response of climate processes to changes in aerosols is investigated using a two-dimensional zonally-averaged climate model. To account for the spatial and temporal heterogeneities of aerosol distributions, a strongly scattering maritime aerosol over ocean and a strongly absorbing rural aerosol over land are used in the layer between the surface and the 700 mb level. The effects of aerosols, gases and clouds on the radiative transfer are computed concurrently using a parameterized form of a two-stream approximation. Aerosols induce a reduction of the solar absorption at the surface and an enhancement of atmospheric absorption. The resulting changes in the climate model parameters are not only a function of the radiatively-active atmospheric constituents, but also of the amplifying or dampening effects of feedback processes employed in the model calculations. For the specified aerosol types and the optical thickness distribution given by Potter and Cess, the annual temperature change at the surface is −2.1 °C with ice-albedo feedback. Without ice-albedo feedback the corresponding value is −1.4 °C. In the present study aerosols produce a cooling effect in the atmosphere at all latitudes.

Solar irradiance in NW Italy

Abstract: An analysis is made of the monthly mean global and diffuse irradiance values recorded by the Genoa University Geophysical Institute radiation network to derive characteristic elements of the solar climate in four typical NW Italy locations. Diffuse irradiation was estimated for the stations where diffuse irradiation data were not recorded, by using correlations between measured data with clearness parameter and sunshine index. Local factors which affect the attenuation of global irradiance under cloudless skies are discussed.

Observed energy flux anomalies during MONEX-79 over the Bay of Bengal

Abstract: The dominant surface energy budget parameters, namely the net radiation fluxes, must be precisely known for an understanding of southwest monsoon behaviour and the early stages of formation of a meteorological system, ie trough, low pressure, depression, cyclone etc, and break monsoon conditions over the Bay of Bengal region The data measured during the MONEX-79 period from July 16–31 are used in order to study the fluctuations of energy fluxes and the net radiation in the month of July over the region During this period the total energy flux is increasing from South to North with a maximum over the head of the Bay However, the fluctuation of net radiation is not significant There is an outstanding increase in the energy flux with anomalies of values 240 W/m2

Stochastic intervention analysis of rainfall

Abstract: Urbanization and industrialization are claimed to affect local climate and to increase precipitation in urban and surrounding rural areas. In the past, considerable meteorologic data have been collected in urban areas and the effects of urbanization on precipitation and other variables have been analyzed by using various techniques. In evaluating urban effects on precipitation, changes in precipitation due to urban effects must be distinguished from changes which are due to natural variability, noise effect, and sampling error. Stochastic intervention analysis is used in this study to establish the statistical significance of changes in monthly precipitation attributed to the effects of urbanization and industrialization and to investigate the nature of these changes. Intervention analysis is especially useful in the analysis of correlated and seasonal monthly rainfall data. Intervention analysis is used to determine whether changes have occurred in the overall mean value or in warm and cold seasons. Monthly rainfall data from Laporte and St. Louis areas are analyzed and the results are presented.

Periodic variations in Stratospheric and low Mesospheric zonal wind in the two hemispheres

Abstract: The long-term, annual, semiannual and terannual waves in mean zonal wind in the Stratosphere and lower Mesosphere are analysed using data from rocket soundings for the region 70° S-80° N for the period 1969–1978. Differences between the hemispheres were obtained and possible reasons are discussed. The Northern middle latitude westerly belt of the long-term zonal wind is higher than that of the Southern middle latitude. The Southern maximum of the annual wave does not appear to be elongated much more than that of the Northern hemisphere. The semiannual double-lobed tropical center seems to be influenced by the lower Stratosphere of the Southern hemisphere. The results from the behaviour of the semiannual wave support the wave absorption hypothesis. The main maximum of the terannual wave is possibly larger in the Southern hemisphere. Differences from previous findings in the literature are discussed as each topic is presented.

Statistical-climatological investigations concerning the heat content of air (enthalpy)

Abstract: The aim of this paper is to investigate the heat content of air (enthalpy) in a statistical-climatological manner. The knowledge of the heat content of air is useful especially for technical meteorology and air conditioning techniques. Enthalpy depends linearely on air temperature and water vapor pressure. Assuming that these factors are independent of each other and that the temperature follows a Gaussian distribution and the vapor pressure a Gamma distribution, it is possible to derive a theoretical distribution function. A critical examination of this independence for two observation stations (Hohe Warte, Vienna; 48° N, 16° E and Sonnblick; 47° N, 12° E) showed that there exists a linear relationship between temperature and vapor pressure at the selected 5%-level. Furthermore it was established that a Gaussian distribution or the sum of up to a maximum of three Gaussian distributions may be fitted to the empirical distribution of temperature. Contrary to the general assumption, it was not always possible to fit a Gamma distribution to the empirical distribution of vapor pressure. Taking into consideration the above-mentioned dependence, the enthalpy was interpreted as a linear transformation of temperature. Consequently, a Gaussian distribution or a sum of up to a maximum of three Gaussian distributions has been fitted to the empirical distribution of enthalpy. By this method, bimodal distributions may also be fitted. The Fisher-Test showed that this type of fitting may be considered significant at the 5%-level for all observation times except one at the investigated observation stations.

Heat budget of air passing through a hot tunnel in northeastern Japan

Abstract: A geothermal and meteorological observation was carried out inside a hot tunnel (named Torigoe tunnel) penetrating through a volcanic zone in northeastern Japan, just after it has been penetrated. Rock wall surface temperature, some thermal properties of rock samples, temperature profile in slender pits drilled into the rock body, temperature of water flowing on the floor and the meteorological elements of air passing through the tunnel are contained in the observation. Introducing the coefficient of heat transfer determined from the Reynolds analogy for turbulent forced convection in a circular tube, the heat budget of the air-tunnel system is investigated with those observed data. The results show that the net sensible heat of 58.61 kW is drawn out from the tunnel by air passing through it and seems to be overcompensated by the net heat supply of 67.21 kW from the rock wall to air, while for the net latent heat removal of 101.56 kW by air the apparent undercompensation of 80.01 kW is found from the water flowing on the floor. Consideration is carried out on such excess and deficiency of heat supplies.

Air-Sea Fluxes over the Global Oceans During the FGGE Year

Abstract: Vertical fluxes of momentum, sensible and latent heat have been estimated over the surface of the global oceans. A three-dimensional mesh grid 32 longitude points, 17 latitude points and 365 days from December 1, 1978 to November 30, 1979 is used to obtain seasonal and annual mean values of the surface fluxes. The global climatology shows the seasonal variation, the continental influence, the principal ocean currents and the typical middle latitude (30°–50°) and tropical effects (30°S–30°N). The annual mean of latent heat shows greater flux over the subtropical regions (~ 280 W/m2) than in the polar regions (~ 80 W/m2). On the other hand, the annual mean of sensible heat shows greater flux over the polar regions (~ 100 W/m2) than in the tropics (~ 40 W/m2). Time series analyses of the daily estimates of the surface fluxes show greater energy at high frequencies due to the surface effect; however, the low-frequency spectra show relatively high energy at the 30- to 50-day mode, especially for the middle latitude regions. The 30–50 day filtered data for the surface fluxes, presented in time/latitude cross-sections for the middle latitude regions show a westerly wave propagation with wave numberK = 2 and phase speed of the order of 12 degrees/day from June to August over the southern hemisphere at 55°S.