Showing papers in "International Journal of Climatology in 1984"

Spatial patterns of precipitation in England and Wales and a revised, homogeneous England and Wales precipitation series

Abstract: The spatial patterns of precipitation variability over the United Kingdom are examined for the period 1861–1970 using principal components analysis. Most of the variance (around 50 per cent) is explained by the first component, which is characterized by uniform variability over the whole region. Higher-order components isolate differential variability between different regions. The first four components are essentially the same for all months, all seasons and the annual total, highlighting the intra-annual constancy of inter-regional variability and pointing to strong geographical and topographical control. A subdivision of the analysis period into two halves produces no change in the component patterns, but changes in the variance explained by the first component imply that summer precipitation has become less spatially variable since 1915. On the basis of the principal components analysis the England and Wales region is divided into five coherent subregions. A regression technique is developed to produce a homogeneous area-average precipitation series for England and Wales using the longest site precipitation records available and maintaining even spatial coverage. The method used allows changes in the reliability of the area-average due to changes in the density of station coverage to be quantified. An empirical relationship between the standard error of estimate of area-averaged precipitation and the number of recording sites is derived. Significant inhomogeneities in the Nicholas and Glasspoole England and Wales precipitation series at 1915 and 1957 are detected and quantified. The Nicholas and Glasspoole series as a whole is found to underestimate precipitation amounts noticeably in the late eighteenth and early nineteenth centuries.

Northern Hemisphere extratropical cyclone activity for four mid-season months

Abstract: Cyclone frequency, cyclogenesis and the primary and secondary tracks followed by extratropical cyclones within the Northern Hemisphere are examined for the four mid-season months: January, April, July and October. The data for these four months were compiled from several sources for the period 1958–1977. Cyclogenesis was defined as the point of origin of a cyclone provided it maintained a closed isobar for 24 hours. Cyclone frequency was determined from the number of occurrences of an extratropical cyclone passing through a 5° latitude-longitude grid box. Analyses of the grid values of cyclone frequency reveal relative maxima which define the cyclone tracks. The tracks are partitioned into primary and secondary tracks depending on the size of the relative maxima of cyclone frequency. Cyclogenesis is concentrated in the lee of major mountain ranges and along the east coasts of Asia and North America, with cyclogenesis in coastal North America found nearer the coastline than in the Asian area. A major cyclogenetic region also exists in the Gulf of Genoa-Northern Italy region of the Mediterranean Sea, but here cyclogenesis is confined to the cooler seasons. As expected the areas of most frequent cyclogenesis shift poleward during the warmer months. Similarly, cyclone frequency exhibits a poleward displacement during the warmer months. It is also noted that whereas winter (January) is characterized by a significantly greater cyclone frequency over the ocean than over land, summer (July) finds the frequency over the continent about as large as over the oceans. Similarly there are significant poleward displacements of cyclone tracks in summer, but the displacement is in no way uniform over the hemisphere. These results can be compared with earlier hemispheric studies of cyclone activity.

African mean wind changes between sahelian wet and dry periods

Abstract: African free air wind velocity data for wet and dry periods in the Sahel have been analysed objectively by the Cressman scheme and show that the lower troposphere easterly jet over west Africa is stronger in the dry period whereas the analogous easterly jet to the south of the equator exhibits greater vertical shear in the wet period. Two possible explanations, based on modulations of the meridional temperature gradients across the jet, are offered.

A generalized classification of South African summer rain-bearing synoptic systems

Abstract: S-mode principal component analysis has been applied to standardized monthly South African rainfall fields and the synoptic systems represented on the higher eigenvectors identified by matching the spatial distribution of rainfall on each component with that of the various weather systems as revealed by satellite imagery. Summer systems identified include cloud bands connecting the tropical and temperate circulations, tropical and subtropical cyclones, coastal depressions, cyclones on the continental west coast and troughs associated with cold fronts on the east coast. The new classification is contrasted with earlier equivalent schemes. The uses of the results in terms of the search for geophysical controls on the development of each of the identified systems are discussed.

The Southern Oscillation, sea-surface-temperature, and interannual fluctuations in Australian tropical cyclone activity

Abstract: The relationship between interannual variations of the number of tropical cyclones observed in the Australian region during a cyclone season and the Southern Oscillation (SO) has been explored. Strong, significant, stable correlations were found between the SO and cyclone numbers. Years with relatively many tropical cyclones were preceded by high North Australian SST, low east Pacific SST and low Darwin pressure. Such years also tended to be followed by the reverse pattern. The study confirms an earlier suggestion (Nicholls, 1979a) that Australian tropical cyclone activity is predictable some months prior to the start of the cyclone season. The observed correlations may result from feedback between the atmosphere and the ocean.

A system for predicting the onset of the north Australian wet-season

Abstract: An index is defined for the date of onset of the north Australian wet-season, based on rainfalls observed at ten stations across tropical Australia. The index is shown to be reasonably representative of wet-season onset throughout the area of interest. Some suggestion of bimodality is found in the frequency distribution of onset dates. An operationally feasible method for predicting the probability that the wet-season will commence late is presented, building on earlier published work which has established the feasibility of prediction of seasonal rainfall near the date of onset of the wet. The forecast method uses the linear logistic equation and Darwin pressures observed in months prior to the onset to make predictions. Acceptable forecasts can be issued four months prior to onset. Two examples of the use of the method are provided.

The southern oscillation and its relation to the monsoon rainfall

Abstract: The interannual fluctuations in the Southern Oscillation indices (Wright, 1975) and their relations to the Indian monsoon (June-September) rainfall have been examined for the period of 106 years from 1875 to 1980. The monsoon rainfall is significantly (99.9 per cent level) correlated with the Southern Oscillation indices for the seasons: MJJ (0.59), ASO (0.67), NDJ (0.53), and FMA of the following year (0.38). The fluctuations in the Southern Oscillation index for the ASO season appear strongly related to the nearly simultaneous monsoon rainfall of India. This implies that the large positive (negative) value of the Southern Oscillation index, signifying strengthening (weakening) of the Walker circulation coincides with large excess (deficient) monsoon rainfall over India. The coherence spectrum reveals that the Southern Oscillation index and the monsoon rainfall are highly correlated in the period range of about 2–2.5 years and 4–6 years. The first of these periods corresponds with the Quasi-Biennial Oscillation and the latter agrees with the features of the Southern Oscillation, suggesting a strong link between Indian monsoon rainfall and these two phenomena. The striking feature of the composites of the Southern Oscillation index averaged for all the drought years and for all the flood years is the simultaneous occurrence of low (high) Southern Oscillation index and droughts (floods) in India. However, this association has limited use in long-range prediction. A preliminary study suggests that a nearly simultaneous occurrence of major climatic anomalies of the tropics, such as droughts in India and El Nino off the coast of Peru, are linked to the Southern Oscillation, indicating some kind of time dependent zonal east-west circulation, i.e. Walker circulation.

The atmospheric modulation of extended wet and dry spells over South Africa, 1958–1978

Abstract: Differences in annual geopotential heights at the 850 and 500 mb levels between 16 pairs of stations have been submitted to principal component analysis to identify the most important statistically uncorrelated pressure patterns accounting for the variance of the annual pressure field over South Africa and adjacent oceans. By correlating component scores for the period 1958/9 to 1977/8 with annual rainfall an attempt has been made to determine the regional rainfall responses to variations in different circulation types. Regional variations in annual rainfall are shown to be significantly linked to variations in both low latitude forcing, associated with tropical easterly airflow and cyclonic wave perturbations therein, and mid-latitude forcing, associated with a variety of both cyclonic and anti-cyclonic perturbations in the westerlies. It has been shown that it is primarily variations in the atmospheric field of motion at the 500 mb level that are responsible for year-to-year differences in annual rainfall totals.

Influence of evaporation in semi-arid regions on the July circulation: A numerical study

Abstract: In this study, two 47-day simulations were made with the general circulation model of the Goddard Laboratory for Atmospheric Sciences starting from the observed initial conditions for 15 June (00Z) 1979 as produced by NMC analysis. In the first simulation, the soil moisture was normally initialized and then allowed to vary by the model generated surface water balance. In the second simulation, the evaporation was prescribed and maintained zero in four chosen semi-arid regions: the Sahel, the Thar Desert border in the Indian subcontinent, the Great Plains in North America and north-east Brazil in South America. Elsewhere the soil moisture was calculated as in the first simulation. The two runs were identical in all other respects. The local climatology simulated by the GCM was analysed in the four anomaly regions. The mean July precipitation increased slightly in the Great Plains and Sahel regions, while it increased substantially (∼70 per cent) in the Thar Desert border region. However, in the north-east Brazil region it decreased slightly. Relative thermal lows were created in each region, along with enhanced rising motion. There was also an increase in the mean monthly diabatic heating in all four regions. An analysis of the vertical structure of the moisture convergence field revealed that there was an increase in the low level moisture convergence in all of the anomaly regions. This compensated for the local moisture deficit created by the lack of evaporation. These results are based on one set of simulations representing the month of July. Further simulations would be required in order to evaluate their statistical significance.

The North-West Australian cloud band: climatology characteristics and factors associated with development

Abstract: The broad characteristics of the North-west Australian Cloud Band, frequently observed across the Australian continent, are outlined. The cloud in the Band is most frequently first apparent within approximately 5° latitude and 17° longitude of 12DS 100°E, and may extend from there for several thousand kilometres, typically towards the east-south-east. It is found to be most in evidence during the winter months. Various atmospheric features associated with the development of the Cloud Band are discussed.

Temporal and spatial characteristics of Arizona dust storms (1965-1980)

Abstract: Hourly meteorological data for four first order stations (Phoenix, Tucson, Winslow and Yuma) were used to identify dust storms which occurred in Arizona from 1965 to 1980. Supporting data on diurnal dust storm frequencies for three Air Force bases in southern Arizona were also used in the analysis. In this study, dust storms have been defined as blowing dust events when visibility is reduced to si-6 km. Data, however, were also collected for all events when visibility was sll-3 km which is the dust storm definition used by Orgill and Sehmel (1976). In general, Yuma experiences the most dust storms per year followed closely by Phoenix, with Tucson and Winslow having very few events. Dust storms at Phoenix, on average, tend to be more severe than those experienced at the other sites. The most intense and frequent dust storms in Arizona occur during the summer months and are associated with strong downdrafts generated by intense thunderstorm activity. Several less intense dust storms of longer duration also occur at most sites during the late winter and early summer months with peak occurrence in April. These events are usually associated with cyclonic storm activity including cold frontal passages and upper level cut-off lows which are common throughout the state at this time of year. Phoenix and Tucson are dominated by late, afternoon dust storms (1700–1800 h) especially during the summer months. Start times are much more irregular at Yuma and Winslow but modes are evident al 0900 h and 1200 h respectively. Phoenix and Tucson experience relatively short duration dust storms averaging 66 and 15 minutes, respectively. Although these dust storms are relatively short, they are rather intense, which is indicated by low visibilities associated with these dust storms. In contrast, storms at Yuma and Winslow are typically longer, lasting more than two hours (160 and 202 minutes, respectively). The dust storm frequency patterns based on visibility criteria pose an important question as to whether higher annual sediment fluxes result from many low-to-intermediate magnitude events or fewer, higher magnitude events. This question cannot be readily answered at the present time because of the lack of sediment load data during dust storms. Although meteorological conditions may play a major role in dust storm generation, detailed research is required to evaluate the relative importance of antecedent moisture conditions, surface soil and vegetation conditions, and anthropogenic factors.

The influence of clouds on climate with A focus on high latitude interactions

Abstract: The global cloud distribution is recognized as forming a major component of the Earth's climate through its influence on both the energy and moisture exchanges in the earth-atmosphere system. This review concentrates on the radiative effects of clouds and examines a number of modelling and empirical studies that have addressed the possible significance of the role of cloud cover in climate change. This question is still not fully resolved. One reason for this is inadequate data and, therefore, some of the cloud climatologies available and the associated problems of data collection and interpretation are discussed. The review focuses specifically on interactions at high latitudes and describes recent studies which suggest that there may be a relationship between sea ice extent and cloud cover. Some possible consequences of this are discussed in the context of a high latitude response to climate change.

Air temperature variations in Greece. Part 1. Persistence, trend, and fluctuations

Abstract: This paper considers annual and seasonal variations of temperatures at three stations in Greece with at least 80 years of records. The extent and nature of non-random changes, such as persistence, trend and fluctuations, are investigated. There is statistical evidence of both Markov linear and non-linear persistence in the data depending on stations and season. The trend analysis showed little of significance, probably because of the time periods chosen. The data were subjected to a ‘lowpass filter’ of a Gaussian type and the series of fluctuations which resulted are discussed. Finally the data for all three stations were combined and filtered in order to show changes that have occurred in the Greek region during the twentieth century.

On the cause of ‘fram’ type seasonal change in diurnal amplitude of air temperature in polar regions

Abstract: The cause of Fram' type seasonal trend of diurnal amplitude of air temperature is investigated from the viewpoint of the surface energy balance. First, the cause of diurnal amplitude of the surface temperature is examined. Then, the effect of the atmosphere between the surface and the screen-level on the amplitude of air temperature is evaluated. The data of the energy balance used in this work were collected at the base camp of the Axel Heiberg Island Expedition (79°25′N, 90°45′W, 200 m) in the Queen Elizabeth Islands, N.W.T., Canada. This site shows a typical ‘Fram’ type trend of diurnal amplitude with annual maximum in April, the summer minimum in June and a secondary peak in August. The April maximum is due to extremely slow sublimation and heat conduclion in the subsurface. The decrease in the amplitude during the later dry snow period in May and early June is due to a gradual increase in sublimation which is induced by the temperature increase. During the melt in June, the diurnal amplitude of the surface temperature is effectively reduced owing to the diurnal change of the latent heat of fusion. After the snow melt, the diurnal amplitude of absorbed global radiation is tripled compared with April. The temperature amplitude remains small, however, owing to the rapid increase in the diurnal amplitudes of energy sinks. The cause of the slight recovery of the diurnal temperature amplitude in August is the decrease in the sensible heat flux. Throughout the entire period, the result of the heat exchange is reflected in a larger temperature variation under lower temperature due to the Stefan-Boltzmann law. This effect contributes to a larger diurnal amplitude in spring.

Indian rainfall in relation to the sunspot cycle: 1871–1978

Abstract: The paper presents the results of a detailed study of the annual rainfall of India in relation to the sunspot cycle for the period 1871 to 1978. Rainfall time series of individual stations as well as of meteorological subdivisions have been examined for the full period (108 years) and for two half periods. The correlation coefficients (CC) of 306 stations for the full period lie between 4–0–29 and −0–14 with a preponderance of positive over negative values in the ratio 4:1. Twenty-six CC values are significant at the 5 per cent level. The CC values for the two subseries reveal appreciable temporal variations, the correlations being higher for the first half. Lag correlations between the rainfall and sunspot series indicate that the CC values tend to increase when the rainfall is correlated with sunspot numbers 1 to 3 years later and to decrease when correlated with sunspot numbers 1 to 3 years earlier. Examination of the all-India rainfall series and the sunspot series for the full period shows that excess rainfall years were significantly more during the ascending phase of alternate cycles. Superposed epoch analysis and the Student t test show that the rainfall around the maximum of even cycles characterized by high sunspot activity is significantly higher than the corresponding rainfall in the odd cycles with lesser spot activity. Correlation study with a 15-year sliding window reveals large temporal variations in the CC values. Although most of the variance in the rainfall time series is due to causes unconnected with the sunspot cycle, the present study suggests the existence of a weak positive association between Indian rainfall and sunspots on the 22-year time scale, although the causal connection is unknown.

Riverflow reconstruction from precipitation data

Abstract: In the United Kingdom few river catchments have overflow records longer than 35 years. The wealth of precipitation data in the United Kingdom enables long records of riverflow to be produced with a catchment model calibrated over the recent period. For most parts of England and Wales it is shown that monthly sequences of riverflow that account for 90–95 per cent of the variance of the measured riverflow can be produced back to 1860. Reconstructions are made on 10 catchments (size range 400–4500 km2) in both upland and lowland Britain. Reliable reconstructions are possible using as few as 4 rainguage records. The reconstructions provide not only a valuable database for the study of the effect of climatic change on riverflow, but also allow stationarity, homoscedasticy and changes in the frequency of extreme events to be examined. It is shown that on the 10 catchments extreme droughts with a duration of 18 months are three times more likely to have occurred between 1925 and 1979 than between 1870 and 1924. The significance of this and other findings are discussed in the context of water resource analysis. The reconstructed riverflows, apart from their obvious use for water resource analysis, also provide a valuable climatological database for the possible further extension of riverflow using proxy climate indicators such as tree rings.

Monthly estimates of wind speed and wind run for Australia

Abstract: This paper introduces the first comprehensive wind speed and wind run maps for Australia. Maps for January, April, July and October based on analyses for all twelve months are presented and discussed. They show, in turn, the distributions of mean 9 a.m. and mean 3 p.m. wind speed at a height of 10 m, the distribution of the ratio between mean daily wind speed and the mean of 9 a.m. and 3 p.m. wind speeds and, finally, the distribution of mean daily wind run at a height of 2 m. The wind speed and wind run maps have been produced from Laplacian smoothing spline surfaces fitted to wind speed observations and to wind run observations and estimates at approximately 500 Bureau of Meteorology stations. The ratio maps, which may be used to estimate wind run from 9 a.m. and 3 p.m. wind speeds, have been similarly produced from data at just 73 Bureau of Meteorology anemograph stations but with independent validation at 68 stations which record both wind speed and wind run. The fitted surfaces are functions of latitude, longitude and a suitable transformation of distance inland from the coast. The degree of data smoothing imposed by the surface fitting procedure has been chosen to minimize for each surface the mean square predictive error estimate as measured by generalized cross-validation.

Homogeneity analysis of rainfall series: An application of the use of A realistic rainfall model

Abstract: One approach in the stochastic modelling of rainfall is to derive a distribution function which has physically meaningful parameters. Such a distribution is derived from a Poisson process of rainfall occurrence with an independent exponentially distributed rainfall amount. The distribution appears to fit monthly precipitation totals extremely well. This type of model has many potential applications in climatology and hydrology. The homogenizing of long term rainfall sequences is one of these, and a methodology for this process is presented here. A 130 year record, from Auckland, New Zealand with three changes of site, is used to evaluate the procedure described. The significant advantage in the proposed method is that the homogeneity testing is done within the single rainfall record and the use of comparison stations is not required.

On the climate of dome C, antarctica, in relation to its geographical setting

Abstract: Automatic weather stations have been successfully deployed in the hostile climate of Antarctica, where temperatures can drop below −80°C and wind speeds are up to 100m.p.h. These stations use satellites for transmission of their data (Argos System). Three years of data had been collected at Dome C (3280m), East Antarctica, before breakdown of the equipment occurred in January 1983. These data were analysed and compared with data from other stations in Antarctica. Results show that the temperature at Dome C can drop very low (−84.6°C), a new absolute world minimum is not expected to be found, however. The annual course of the temperature displays the typical ‘coreless’ winter phenomenon, with no systematic temperature changes for 4 to 5 months, and mean temperatures of about −60°C during this time. This fits well into the picture found at other high altitude inland stations of Antarctica. The wind speeds observed at Dome C were the lightest, not only of all interior stations in Antarctica, but of all antarctic stations, including coastal and near-coastal ones. This illustrates the well-known dependence of the katabatic winds on slope angles and topography. Despite steep and deep surface inversions, katabatic winds generated at higher elevations on the continental slopes do not appear to override Dome C, but flow around it. By contrast, the winds observed in the coastal regions of Adelie Land, some 1000 km away from Dome C, belong to the strongest found anywhere on the earth. Another indication that Dome C is free from any gravity flow can be found in the fact that the winds display a diurnal maximum during the summer months around noon or early afternoon, at a time when the inversion strength is at a minimum. For gravity flow, one would expect a minimum in wind speed at that time, as observed in the coastal region.

Weather-type classification by factor analysis in the Thessaloniki area

Abstract: In an attempt to study weather and climatological conditions in the Thessaloniki area during the winter period, a weather-type classification is proposed according to principles first adopted by Russian authors. The methods of factorial analysis are used for this weather-type classification. A study of the monthly and yearly frequencies of good, unpleasant, cloudy or overcast weather allows us to better understand the area's ‘atmospheric quality’ affecting man's life in it.

The relationship of soil temperature to vegetation height

Abstract: Using extensive observations of air and soil temperatures made under a variety of vegetated surfaces (forest, heather and grass) the influence of vegetation characteristics on the mean soil temperature is considered. It is demonstrated that the main influence is the height of the vegetation, with canopy density only a subsidiary factor. Consideration of the energy balance from two catchments in Wales (one forested and one grassland) strongly suggests that it is the aerodynamic resistance (itself related to vegetation height) which is the determining factor.

The effect of weather map scale on the results of A synoptic climatology

Abstract: The results of an objective synoptic climatology of glacier mass balance in south-western Canada are affected by the scale and degree of generality of the synoptic patterns used Two scales of 500 mb daily weather maps are compared Statistical analysis shows little direct relationship between the two scales: the smaller, high wave number patterns vary randomly within the more general flow of the larger circulation patterns However, further analysis suggests that the smaller synoptic patterns control glacier mass balance in coastal British Columbia Glacier accumulation in the Canadian Rockies is more closely related to larger-scale atmospheric flow

Riverflow reconstruction from tree rings in southern Britain

Abstract: The results are statistically significant, and the stability of the regression models is verified using independent data. The reconstructions are more reliable for low flow events; a finding which is potentially useful for water resource planning. The reconstructions indicate a possible increase in the frequency of extreme low flows over the period 1755-1859, compared to 1860-1979, which although not of conclusive statistical significance, warrants further investigation.

Rainfall over the southern slopes of the Himalayas and the adjoining plains during ‘breaks’ in the monsoon

Abstract: During ‘breaks’ in the south-west (or summer) monsoon there is a general cessation of rainfall activity over most of the Indian area, but this activity increases over the southern slopes of the Himalayas and its adjoining plains. In this study, rainfall distribution during the ‘break’ monsoon situations has been studied, over the southern slopes of the Sikkim, Nepal and Uttar Pradesh Himalayas (i.e. from longitude 78°E to 89°E) and their adjoining plains. Rainfall distributions during the major ‘break’ situations which occurred during the principal monsoon months of July and August of the period from 1957 to 1969 were studied. This study has shown that, on a ‘break’ day, positive percentage departures of rainfall as high as 100 to 300 per cent have occurred at stations located in the outer Himalayas and the adjoining plains of north Bengal, east and central Nepal, Bihar and east Uttar Pradesh. However, the width of this heavy rain-belt is maximum over the hills and plains of south-eastern Nepal and the adjoining plains of north Bihar. This study has also shown that on a ‘break’ day there is a decrease of rainfall activity over the Himalayas west of longitude 80°E. Decrease of rainfall also takes place along a narrow belt immediately to the south of the great Himalayan range to the east of longitude 80cE outside Sikkim. Over the adjoining Gangetic plains, an increase in rainfall is noticed even to the south of the Ganga river in Bihar and its neighbourhood. Thus, owing to the increase in rainfall activity during ‘break’ monsoon situations in the catchments of Himalayan rivers located in Sikkim and Nepal, a peculiar situation arises which is responsible for causing floods in the downstream plains which experience almost drought conditions.

Estimating solar radiation in A tropical environment using satellite data

Abstract: Daily values of satellite derived reflectivity and daily totals of incoming solar radiation were obtained over a six-month period for a network of stations in tropical Queensland, Australia. A definite linear relationship was observed between the reflectivity of the earth-atmosphere system and the atmospheric transmissivity calculated as the portion of extraterrestrial radiation reaching the surface. The scatter in the relationship was largely due to variation in the number of satellite scans available each day and to variations in aerosol absorption. Using the regression model, the transmissivity of solar radiation has been calculated over the entire study region for the months of August 1982 and January 1983. The spatial variability of incoming solar radiation has been discussed. It was found that the spatial pattern is strongly dependent on topography and wind direction.

The annual and seasonal distribution of fronts over central-southern Europe and the Mediterranean

Abstract: An analysis of the frequency of occurrence of fronts over central-southern Europe and the Mediterranean was carried out based on daily synoptic charts for the nine year period from 1971 to 1979. Tables and charts are presented showing the annual and seasonal frontal frequencies over the area, and the variation of average frequency of fronts with latitude and longitude is demonstrated. The distribution of the frequency of fronts fits in with generally accepted models of hemisphere circulation. An interesting feature is the relative importance of each type of front to the seasonal patterns which emerge. Cold fronts contribute strongly in all seasons with frequencies of approximately 1 in every 10 days in spring, summer and autumn and of 1 each week in winter.

Method of study and cartography of the potential Sunny periods in mountainous areas

Abstract: In mountainous areas, the duration of sunny periods is an important but often unknown climatic parameter. The difference in amounts of sunshine between exposed and shade sides of mountains must be treated circumspectly, sometimes corrected, for it is dependent on the action of shadows and thus can sometimes reduce the amount of sunshine at a given spot quite considerably. By using a computerized calculation comparing the apparent movement of the sun and the positions of the summits surrounding a given point, the duration of sunshine at this given point can be calculated for a chosen period of the year. This same calculation repeated for frequent points within a same area is transferred to a grid. This grid can be used to draw maps of the potential amount of sunshine for that area at a precise date or between two given dates. This kind of study can be a valuable aid, not only in research into the environment (the amount of insolation is a determining factor in the melting of snow or ice, the evaporation of lakes, the development of vegetation etc.) but also in the planning of an area (solar energy, exposition of buildings in an urban setting, research into sites for new tourist resorts etc.).

What if increases in atmospheric CO2 have an inverse greenhouse effect? I: Energy balance considerations related to surface albedo

Abstract: An analysis of northern, low and southern latitude temperature trends of the past century, along with available atmospheric CO2 concentration and industrial carbon production data, suggests that the true climatic effect of increasing the CO2 content of the atmosphere may be to cool the Earth and not warm it, contrary to most past analyses of this phenomenon. A physical mechanism is thus proposed to explain how CO2 may act as an inverse greenhouse gas in Earth's atmosphere. However, a negative feedback mechanism related to a lowering of the planet's mean surface albedo, due to the migration of more mesic-adapted vegetation onto arid and semi-arid lands as a result of the increased water use efficiency which most plants experience under high levels of atmospheric CO2, acts to counter this inverse greenhouse effect. Quantitative estimates of the magnitudes of both phenomena are made, and it is shown that they are probably compensatory. This finding suggests that we will not suffer any great climatic catastrophe but will instead reap great agricultural benefits from the rapid increase in atmospheric CO2 which we are currently experiencing and which is projected to continue for perhaps another century or two into the future.