bluuebunny/crossref_metadata_2025 huggingface dataset:
Regional variations in the annual cycle of rainfall in Ireland as revealed by principal component analysis
Authors: Logue J. J.
Published: February 2007

Principal component analysis is applied to long‐term average monthly rainfall amounts expressed as percentages of the annual average in order to study variations in the annual cycle of average rainfall in Ireland. It is found that these variations can be described in terms of two principal components (PCI and PC2) which together account for about 80 per cent of the total variance. PCI represents a tendency for rainfall to be high in summer as compared to winter and is a maximum in the midlands and north‐east. PC2 represents a tendency for the first half of the year to be relatively wet and the second relatively dry and is a maximum in the south‐east. Physical explanations for these features of the rainfall climate are suggested.
Climatological premises of soil drought forecasting
Authors: Sadowski M. J.
Published: February 2007

Argumentation and premises to formulate soil drought forecasting in Poland in the summer of 1982 are presented in this paper. The forecast was formulated in the spring of 1982 and was based on such premises as the relationship between mean atmospheric pressure for the summer season APL (May‐August) and the atmospheric pressure of the proceeding winter season APZ (January‐March), long‐lasting sea surface temperature (SST) anomalies in the Norwegian Sea and the central part of the northern Atlantic which preceded the occurrence of drought, and the frequency of drought in Poland.

It has been stated that a good relationship exists between the atmospheric pressure departure in a summer with soil drought and the same values for the preceding winter season. In the area with values of winter and summer pressure departure higher than 4hPa only summer soil drought occurred in Poland during the twentieth century. Such summer seasons are preceded by long periods with SST anomalies in the M and K/R weather ship areas. As a rule when either of these regions has positive anomalies then the other has negative.

Weather conditions in the summer of 1982 have confirmed the correctness of the argument which ended in the formulation of a forecast, as well as the high consistency of forecast weather conditions with those which occurred.
Temporal and spatial characteristics of Arizona dust storms (1965–1980)
Authors: Nickling W. G. , Brazel A. J.
Published: February 2007

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.
A global archive of land cover and soils data for use in general circulation climate models
Authors: Wilson M. F. , Henderson‐Sellers A.
Published: February 2007

A new global archive of soil type and land cover data derived for use in GCM climate models is described. The data are archived al a resolution of 1° latitude × 1° longitude. The method of construction of the component data sets is given together with ‘reliability estimates’. The soils data form the only published data set designed specifically for use in climate studies. The land cover data are compatible with the soils data, forming a coherent and complete data set and seem to be comparable with other land cover information. Recommendations are made about combining and coarsening the data to the grid of any general circulation climate model. Methods of parameterizing surface radiative and hydrological properties in climate models are proposed.
Local winds in the southern alps, new zealand
Authors: Sturman A. P. , Fitzsimons S. J. , Holland L. M.
Published: February 2007

A study is made of local wind development in New Zealand alpine valleys. The general characteristics of alpine airflow regimes are examined using both climato logical and case study approaches. Thermo topographic and dynamic effects are the major influences on valley airflow, the relative significance of each varying spatially as well as seasonally and diurnally. Case studies show that clear relationships exist between micro meteorological characteristics within an alpine valley and the phases of local wind development. In particular, boundary layer stability and energy flow characteristics are seen to vary with different phases of local wind development. The examples studied illustrate basic characteristics of local airflow, but particularly the development of nocturnal mountain winds with a transition to daytime up‐valley flow. The airflow shows classic local wind characteristics, regarding depth, speed, and return currents. An intermediate layer frequently occurs between the alpine valley wind regime and the gradient flow above. This layer of generally light winds may be persistently north‐westerly and the result of regional dynamic forcing of the gradient wind. Alternatively, under weak gradient airflow, it may exhibit variability indicating regional thermal forcing.
Temporal and spatial rainfall variability in the mountainous region of the reventazón river basin, costa rica
Authors: Chacón R. E. , Fernandez Walter
Published: February 2007

Two seasonal periods with different rainfall characteristics were identified in the mountainous region of the Reventazón River basin, Costa Rica, a region of about 1770km2 with altitudes in the 50O‐3000km range. These seasonal periods are December‐April, in which orographic rain predominates, and May‐November, in which convective showers predominate.

The temporal variability of rainfall in the study area was examined using the coefficient of variation. It was found that the largest values of the coefficient of variation occur at high altitudes and the lowest values at middle altitudes. They are large in the December‐April period and small in the May‐November period.

Correlation analysis was used to determine the spatial variability of rainfall in the study area. The results obtained show that the monthly and seasonal values of the correlation coefficient are generally larger than 0.7 over the study area in the December‐April period. In the May‐November period, the values of the correlation coefficient are in general quite small, less than 0‐3 for distances less than 50 km in the case of seasonal totals. In this latter period, a few values of the correlation coefficient larger than 0.7 are observed, but they correspond to areas with correlation radii less than 3 km.
Vertical velocity forced by topography in the southern hemisphere
Authors: Vianello Rubens Leite
Published: February 2007

The vertical component of wind forced by topography in the Southern Hemisphere is calculated using the equation given by Saltzman and Irsch (1972). This equation contains the contribution of Ihe zonal mean. Results show that the vertical velocity forced by topography in the Southern Hemisphere is in genera! comparable to that in the Northern Hemisphere. As in the case of the Northern Hemisphere, the zonal deviations of wind contribute significantly to the vertical velocity.
Urban modification of diurnal temperature cycles in birmingham, U.K.
Authors: Johnson D. B.
Published: February 2007

The urban heat island has traditionally been studied by showing its magnitude at a particular point in time, normally at night, when it reaches its maximum. The following paper adopts the strategy of Oke and Maxwell (1975) using heating and cooling rates to study the heat island. This method has the advantage of showing how the heat island develops and decays throughout the day. As the results reveal the most important changes occur at sunrise and sunset, the relative importance of the generating processes are considered with reference to the radiation budget of the urban surface. Results are reinforced by using urban and rural thermograph data.
Intra‐ and inter‐hemispheric teleconnections using seasonal southern hemisphere sea level pressure
Authors: Harnack Robert P. , Harnack Jeremi
Published: February 2007

In this study spatial and temporal relationships involving Southern Hemisphere (SH) sea level pressure (SLP) were examined using a 25‐year data set assembled for this purpose, with special emphasis on discovering inter‐hemispheric teleconnections in the seasonal SLP field. Principal component and correlation analysis was employed. The most important findings include:

Season‐to‐season autocorrelation of SLP is at least as large in the SH as in the Northern Hemisphere (NH), though the amount of area of significant autocorrelation is not great in either hemisphere (i.e. a total global area of 17‐24 per cent).

Principal component (PC) analysis performed on SH SLP in conjunction with Monte Carlo tests of significance showed that three or four PCs, explaining 40 to 58 per cent of the variance, represent the climatic signal in the data set.

Field significance tests applied to each teleconnection map, produced for each grid point in the SH, implied that there is a strong likelihood of real inter‐hemispheric relationships in NH winter. There was much less certainty in the other seasons. Examination of significant teleconnection maps suggested SH links to the Southern Oscillation, the North Atlantic Oscillation, Siberian High strength, and the ‘West Pacific pattern’ described by Wallace and Gutzler (1981).
Large‐scale features of satellite‐derived outgoing long‐wave radiation in relation to monsoon circulation over the indian region
Authors: Prasad K. D. , Verma R. K.
Published: February 2007

The monthly mean outgoing long‐wave radiation data from June 1974 o May 1981 were analysed for dominant eigenvector patterns. The first three eigenvector patterns explain nearly 93 per cent of the total variance. The first eigenvector pattern exhibits an annual cycle with a pronounced variation in the outgoing long‐wave radiation over the tropical belt between 10 and 20°N. This is largely indicative of strong seasonal shift of the major area of cloudiness associated with the Intertropical Convergence Zone. The second eigenvector pattern shows an out‐of‐phase relationship between north India and the equatorial region, having a pronounced semi‐annual oscillation. The third eigenvector pattern exhibits the characteristic features of the north‐east monsoon over south‐east peninsular India. The first and second harmonics, corresponding to annual and semi‐annual oscillations, exhibit the major characteristic features of the first two eigenvectors, respectively.

The interannual variation of the outgoing long‐wave radiation for the summer monsoon period shows a close association with the large‐scale monsoon rainfall over India.

It is concluded that the satellite‐derived outgoing long‐wave radiation can be used to monitor more comprehensively the large‐scale monsoon circulation and its year‐to‐year variability in view of its spatial coverage over oceanic areas.
Climatic subdivisions in saudi arabia: An application of principal component analysis
Authors: Al‐Jerash Mohammad A.
Published: February 2007

Two computer programs were executed on the available climatic data of fifty stations dispersed throughout Saudia Arabia. The first was a program for calculating the variables that represent potential evapotranspiration, soil moisture content and actual evapotranspiration. The aim of this step was to broaden the base of analysis whereby the processing of twenty‐four climatic variables becomes possible. The second was a principal component analysis program. The application of this program was carried out in two stages. First, on the twenty‐four climatic variables. This has led to the identification of five climatic components as being the principal factors that control the spatial variations of the climate in Saudi Arabia. Secondly, on the scaled distance matrix that was originally calculated using the station scores of the five components. This resulted in grouping the fifty climatic stations into six categories each of which represents a distinct spatial climatic subdivision of the country.
The extrapolation of recent climatological series with spectral canonical regression
Authors: Guiot Joel
Published: February 2007

This paper describes a simple but efficient method, based on classical techniques, which enables one lo estimate missing data and to extrapolate short instrumental climate series from other instrumental or proxy ones. By mutually exclusive digital filters, the variations of the data are decomposed into a rough spectrum. A canonical analysis is performed on each of these parts, providing relationships for each principal time‐scale. A global equation is then computed by inverse transformation. Generally, the predictands are better fitted by this method than by a standard regression. The improvement is shown for both instrumental and proxy data. The method can easily be applied in many topics where relationships between two groups of variables have to be estimated: agroclimatology, ecology and geophysics in general. It can run on a microcomputer with a BASIC program available from the author.

By this method, a reconstruction of June‐July temperature at Marseille (France) is proposed showing a period of weak variability of the temperature during 1400‐1850, that is to say a period of rare warm summers with very cold summers only in the early 16th and late 17th centuries. An extrapolation of the instrumental series at Nice from corresponding series of Marseille and Gap is also developed.
Seasonal relationships between indian summer monsoon rainfall and the southern oscillation
Authors: Parthasarathy B. , Pant G. B.
Published: February 2007

Association between the all‐India summer monsoon (June to September) rainfall and an index of the Southern Oscillation (SO) is studied in relation to the vagaries of the monsoon rainfall and the seasonal characteristics of the SO. The Southern Oscillation index (SOI) used is the difference of normalized sea surface pressure between Tahiti and Darwin, two stations located in the core regions of the circulation systems associated with the SO. The data length of 46 years from 1935 to 1980 is used in the detailed examination of the nature of association between these parameters.

The SOI values of different months and standard seasons show opposite tendencies during deficient and excess years of all‐India monsoon rainfall. The correlation coefficients (CC) between the all‐India monsoon rainfall series and the SOIs of summer monsoon (JJA), autumn (SON) and winter (DJF) minus spring (MAM) seasons are significant at the 1 per cent level. The correlations have been examined by dividing the series into two equal halves of 23 years and different sliding window widths of 10, 20 and 30 years. The least squares fit line is represented by the equation y (all‐India monsoon rainfall) =85.9 ‐ 2.7x (DJF minus MAM, SOI), the variance explained by this line is about 13 per cent. In view of the large spatial variability of the summer monsoon rainfall the correlations are examined for the rainfall series of various meteorological subdivisions of the country. The CC between the monsoon rainfall of the subdivisions north of 16°N and west of 80°E and the SOI series of DJF minus MAM is significant at the 5 per cent level or above.

Potentialities of the SOI of DJF minus MAM, an important premonsoon circulation parameter, are examined for the seasonal prediction of Indian summer monsoon rainfall, and the limitations of single parameter prediction models are discussed.
Synoptic and satellite aspects of the southwestern u.s. summer ‘monsoon’
Authors: Carleton A. M.
Published: February 2007

Satellite infrared imagery for three years (1980, 1981, 1982) are analysed using a colour enhancement technique to derive a cloud climatology of the southwest United States summer ‘monsoon’. Diurnally‐stratified and weekly statistics are obtained for different cloud levels and used as an index of the monsoon intensity in each year. Strong diurnal variations in cloudiness, related to surface heating, are identified for July and August, as are marked interannual differences. These regional‐scale cloud variations are found to correlate more closely with the 700mb wind direction than with the height of the 700 mb pressure surface when considered for a representative station (Winslow, Arizona). A satellite‐based definition of ‘monsoon’ best considers variations of the total cloud rather than of any individual cloud level(s).

Several surface and 700 mb synoptic circulation indices are identified and related statistically to the intraseasonal cloudiness changes. The most significant association is found for the variations in latitude of the Bermuda high pressure ridge that presumably relates to changes in subsidence. However, the sign of this relationship may reverse in years when other circulation systems, notably the North Pacific anticyclone, also influence the desert Southwest. Consideration of the zonal westerly index between 45 and 65°N tends to improve the correlation between the Bermuda ridge and summer monsoon cloudiness over the region. Such cloud‐circulation studies have implications not only for climate dynamics but also for ongoing solar energy research in the American Southwest.
A contribution to the upper‐air climatology of tropical south america
Authors: Chu Pao‐Shin
Published: February 2007

An upper‐air climatology of tropical South America is presented using objectively analysed geopotential height, temperature and wind data from various radiosonde stations for the common period 1970‐1974.

In the lower troposphere the South Atlantic high dominates the geopotential height patterns extending deeply into interior Brazil in Southern winter. In the upper troposphere, contour gradients are concentrated around the subtropical region in winter. Temperature analysis shows the steep meridional gradient in winter. In summer, the Peruvian‐Bolivian Altiplano heating effect is manifested in the mid‐tropospheric temperature fields and also in the thickness field.

Lower‐tropospheric flow throughout the year is marked by an anticyclonic turning of easterlies over much of eastern Brazil. Easterlies originating from the South Atlantic high penetrate further inland in Southern winter. Upper‐tropospheric flow changes dramatically from mainly westerly in winter to a well‐defined anticyclone over the Altiplano and a trough downstream over northeast Brazil in summer. Thickness and temperature patterns indicate that the upper anticyclone is maintained by a warm‐core system whereas the trough is marked by a relatively cold temperature. Upper tropospheric flows are equivalent barotropic in nature over tropical South America. The map discussion of summer and winter circulation is complemented by cross‐sections of meridional wind component along approximately 60°W.
On the zonally averaged temperature in the southern hemisphere
Authors: Satyamurty P. , Brahmananda Rao V.
Published: February 2007

The observed meridional temperature gradients in the middle and high latitudes of the southern hemisphere are much higher than the critical gradients necessary for the manifestation of baroclinic instability in a two‐level quasi geostrophic model. This is in contrast to the ‘baroclinic adjustment’ observed in the northern hemisphere by Stone (1978).
Energy balance climate modelling: An alternative dynamic parameterization
Authors: Cerveny Randall S. , Balling Robert C.
Published: February 2007

This paper describes a dynamic parameterization for a simple global climate model that is based on the planetary boundary layer equations of horizontal motion. This new parameterization resolves many of the problems associated with other representations of the general circulation in simple climatic models. The model developed in this study accurately simulates the presently observed zonally‐averaged temperature and wind field patterns. Sensitivity tests demonstrate that a model with the new dynamic parameterization meets or exceeds the performance levels of other one‐dimensional energy balance global climate models. By solving many of the problems associated with the available alternative circulation parametcrizations, the new circulation representation based on the equations of motion appears to improve the quality of the popular simple climate models.
On the radiation budget in the alps
Authors: Müller Hans
Published: February 2007

This study reviews the investigations on the radiation budget in the Alps at elevations above 1500 m a.s.l. Regarding outgoing radiation, only that from snow and ice is considered. Physical relationships between radiation and variables such as elevation, month and cloud amount are discussed. The individual components of the radiation budget are analysed first, and then an attempt is made to synthesize radiation balances.

Elevation dependencies between 2000 and 3500 m a.s.l. in the canton of Valais (south‐western Switzerland) in summer (June to August) for average cloud conditions (1931‐1960) are as follows: the cloud amount increases from 0.507 to 0.582. The maxima occur in June. Global radiation increases from 22.7 to 23.6 MJm−2d−1. The maxima occur in June. Counter‐radiation decreases from 25.8 to 21.9 MJm−2d−1. The maxima occur in July. For average albedo, the radiation balance of horizontal glacier surfaces decreases from 15.3 to 5.3 MJm−2 d−1, with the maxima occurring in July. For albedo conditions after snowfall, the radiation balance decreases from 2.7 to 1.3 MJm−2dd−1, the maxima occurring in June or July.

The study has the following applications, among others: it can (1) contribute to the understanding of the genesis of the climate of the Alps, (2) assist in the development of runoff models for heavily glacierized basins and (3) be helpful in the use of solar energy.
Long‐term trends of surface air temperature in india
Authors: Hingane L. S. , Rupa Kumar K. , Ramana Murty Bh. V.
Published: February 2007

Salient features of the long‐term variation of surface air temperature for India as a whole and for different regions of the country have been presented. Temperature data at 73 fairly widespread stations, for the period 1901‐1982. have been used in the study. Seasonal and annual temperature anomaly series have been obtained for the different regions. Such series have also been obtained for latitude‐ and longitude‐wise classifications. The long‐term variation in the temperature has been evaluated by linear trend.

The results indicate a slight but definite warming trend in the mean annual Indian temperatures. This warming is found to be mainly contributed by the post‐monsoon and winter seasons. West coast, interior peninsula, north central and north‐east regions of the country have shown pronounced warming in the mean annual temperatures. The post‐1940 cooling reported for the Northern Hemisphere is not conspicuous in the mean annual Indian temperature anomalies.
Anomalous mid‐atmospheric heights and persistent thunderstorm patterns over florida
Authors: Michaels P. J.
Published: February 2007

A principal component analysis (PCA) of Florida thunderstorm patterns (1948‐1982) revealed three statistically significant spatial modes of variation from summer‐to‐summer. The most important was in the region of sea breeze convergence, which has been previously hypothesized to be the main initiator of summer thunderstorms over peninsular Florida.

A companion analysis of 500 mb height data over the south‐eastern U.S. uncovered only one significant pattern of variation from the mean, when tested against uncorrelated data. We hypothesized, prior to testing, that dynamic considerations would make it negatively correlated with the most important thunderstorm pattern. A subsequent regression analysis allows that hypothesis to continue to be entertained. A canonical analysis verifies this finding.

The results suggest that the sea‐breeze‐related thunderstorm patterns are influenced over seasonal and longer time scales by the first 500 mb component. There has been a significant secular change both in the most important thunderstorm pattern and its related 500 mb pattern over the period of this study.
Climatology of the terrestrial seasonal water cycle
Authors: Willmott Cort J. , Rowe Clinton M. , Mintz Yale
Published: February 2007

Calculations of the spatial and seasonal variations of the continental fields of snow‐cover, soil moisture and evapotranspiration are presented and interpreted. The calculations were made with a water budget analysis that is based on observed average monthly precipitation and an estimate of potential evapotranspiration derived from observed average monthly surface temperature, using a modified version of the method of Thornthwaite. Monthly average water budget analyses were made for 13,332 stations over the globe and, then spatially interpolated to a regular grid at 1° by 1° latitude‐longitude intervals. From the monthly fields on a 4° by 5° subset of the 1° by 1° grid, the annual mean and standard deviation as well as the first and second annual harmonics were extracted and are displayed on global maps. Of the three fields, soil moisture has the largest space‐time variation; snow‐cover the smallest variation; and evapotranspiration an intermediate level of variation.
Variation of spatial annual precipitation sums in central europe in the period 1881‐1980
Authors: Brázdil R. , Ŝamaj F. , Valoviĉ Ŝ.
Published: February 2007

The analysis of atmospheric precipitation variation in Central Europe in the period 1881‐1980 is based on the series of the so‐called spatial annual precipitation sums for the F.R.G., the G.D.R., Poland, Bohemia, Moravia, Slovakia and Hungary and for the Baur series. The annual precipitation variation in the above period is studied by means of series of 5‐year and 11‐year gliding means. Methods of autocorrelation analysis, spectral analysis (partly according to Blackman and Tukey, partly maximum entropy spectral analysis), coherency analysis and numerical bandpass filtering were used for analysing precipitation periodicities and cycles.

In the period studied, the western part of Central Europe (the Baur series, F.R.G., also G.D.R.) shows a generally increasing precipitation trend at below‐mean sums approximately up to 1920, whereas a more or less decreasing tendency is typical of the remaining series. Periods with analogous lengths appear in precipitation series in the whole of Central Europe and at the same time the lengths of significant periods are shortened from 4.4 and 5.0a (a = year) in the western part to 3.3 and 3.6a in the eastern part. At the same time, significant coherence among the studied series most frequently appears for periods of 2.5 and 13.3a. Periods with lengths of 2‐3 years take a more conspicuous part in the total variance of the corresponding series (about 30 per cent), except in the cases of Slovakia and Hungary, where the maximum share is shifted to oscillations with periods of 3‐4 years and for the F.R.G. and the Baur series to the interval of 4‐6 years. The course of the filtered series refers to the length and phase instability of the periodicities found, which complicates the use of the knowledge obtained for long‐term precipitation forecasting.
A comparative performance analysis of three meteorological drought indices
Authors: Olukayode Oladipo E.
Published: February 2007

Three indices for designating drought are examined and their comparative performance in depicting periods of different drought intensities is discussed. These indices are the rainfall anomaly index (RAI), Bhalme and Mooley drought index (BMDI) and the Palmer drought index (PDI). Using data from Nebraska state as an example, the three indices all appear to be effective in detecting drought periods. The results of the analysis suggest that precipitation is the most important climatic element as an input into meteorological drought. It can, therefore, be concluded that for meteorological purposes, and when undertaking single‐station analysis, simple indices with rainfall as the only input perform comparatively as well as the more complicated indices in depicting periods and intensity of drought.
Climate reconstruction from tree rings: Part 2, spatial reconstruction of summer mean sea‐level pressure patterns over Great Britain
Authors: Briffa K. R. , Jones P. D. , Wigley T. M. L. , Pilcher J. R. , Baillie M. G. L.
Published: February 2007

We present a methodology for the reconstruction of spatial climate patterns over the British Isles using tree rings. The predictands are mean sea‐level pressures averaged over May to July for a 16‐point grid centred over the British Isles. The predictors are ring widths from a network of 14 oak tree‐ring chronologies (Quercus petraea Liebl. and Q. robur L.) in Britain and northern France. Major spatial modes of variance in the climate data are linked directly with those of the ring‐width data via a series of principal component regressions. Reconstruction performance is assessed by examining calibration and verification statistics at individual grid points and for individual pressure principal component amplitudes. The reconstruction equations are examined in order to identify, region by region, which chronologies are most valuable. This diagnostic approach to reconstruction assessment, when coupled with information on the statistical quality of the chronologies themselves, can suggest areas where future field‐work would be most valuable. Though limited in scale, these pressure reconstructions are the first to have been made using trees from maritime sites, and are the first to be comprehensively verified using independent pressure data.
Precursors of the Southern Oscillation
Authors: Wright Peter B.
Published: February 2007

Evidence is presented of the existence of three largely independent precursors of changes in the Southern Oscillation (SO). In a region of the south‐east Pacific, anomalously high SST, low pressure, low cloudiness and weak winds tend to occur in December‐February (DJF) prior to a year of low SO index. In the equatorial Atlantic, anomalously warm sea in DJF tends to follow a period of low SO index and precede a year of high index. Cold SST in a region near northern Australia is associated in every season with a trend towards warmer SST in the equatorial east Pacific, and in most months with anomalous westerly winds in the equatorial west Pacific. Plausible physical scenarios are proposed to explain the relationships.
Temporal fluctuations of daily rainburst and the cycle of the lunar year
Authors: Ghayoor Hassan Ali
Published: February 2007

The purpose of this research is to investigate climatic fluctuations connected with the cycles of the lunar year. The rainfall data belonging to the Balcombe station, Sussex, England, are used. From these data, variations in the frequency per year of daily rainfalls over 25 mm, which in this research are called daily rainbursts, are investigated, and the results show that there is a quasi‐regular fluctuation, connected with the cycles of the moon, in the number of daily rainbursts.
Factors affecting the isotopic composition of daily rainfall at Driby, Lincolnshire
Authors: Heathcote John Anthony , Lloyd John William
Published: February 2007

To further the understanding of the relationships between past climatic conditions and the hydrogen and oxygen isotope composition of old groundwaters, a study of the relationship between the composition of daily rainfall and meteorological parameters at a single site was made. The composition of daily rainfall was found to be extremely variable, with little seasonal dependence, and with no clear relationship to daily mean air temperature. This is typical of a maritime climate, although the site studied is located on the east coast of England. The most important control on composition is the origin of the precipitating air mass, whether Atlantic or Continental. The possibility of investigating past climates is discussed.
Relationships between raindays, mean daily intensity and monthly rainfall in the tropics
Authors: Jackson I. G.
Published: February 2007

There are limitations in using monthly rainfall totals in studies of rainfall climatology as well as in hydrological and agricultural investigations. Analysis of data for a range of tropical rainfall stations suggests that a better relationship exists between monthly rainfall and number of rain days than between monthly rainfall and mean daily rainfall intensity. In the former case, a logarithmic relationship is most appropriate, whereas for the latter a linear form is adopted. Deviations from the relationships show contrasts between stations and also within seasons at individual stations, suggesting the need for caution in attempting to generalize about tropical rainfall conditions. For some stations and at the start of rainy seasons, the two parameters examined suggest that the character of rainfall may create agricultural and hydrological problems greater than monthly totals suggest.
A geography of dust storms in South‐West Asia
Authors: Middleton N. J.
Published: February 2007

Mean annual dust storm frequencies are mapped for south‐west Asia (Iran, Afghanistan, Pakistan and India) showing areas of greatest activity in two regions: an area at the convergence of the borders of Iran, Afghanistan and Pakistan that comprises the Seistan Basin, Registan and north‐western Baluchistan; and the plains of Afghan Turkestan. The highest average annual number of dust storm days is 80.7 at Zabol in Iranian Seistan. Little dust‐raising activity occurs on the Indian peninsula. Dust storms occur principally during the dry season months of spring and summer.

Local and regional meteorological conditions associated with dust storms are described, ranging from the short‐lived dust devil measuring tens of metres across to dust plumes visible on satellite imagery. Dust is transported from the region north to Asian states of the U.S.S.R., south over the Arabian Sea and east over south‐east Asia. The importance of soils in the wind erosion system is indicated. Dust storms commonly occur on fine‐grained material, particularly loess, alluvium, silt, clay and other outwash sediments. Dust storms have received a variety of names locally in the region.

Dust storm frequency during the peak season in northern India is found to be poorly related to mean rainfall, mean wind speed and a climatic wind erosion factor,Cdeveloped by Chepilet al.(1962).
Relationships between extremes of the Southern oscillation and the winter climate of the Anglo‐American Pacific Coast
Authors: Yarnal Brent , Diaz Henry F.
Published: February 2007

Warm and cold events in the central and eastern equatorial Pacific represent the two extreme climatic states of the Southern Oscillation and are related to pronounced winter climate anomalies along the Pacific coast of Anglo‐America. Previous research has demonstrated that the Pacific/North American (PNA) pattern may be the typical response of the northern hemisphere winter atmosphere to tropical forcing during warm events. In general, the anomalous flow associated with the PNA pattern raises winter temperatures along the entire length of the Anglo‐American west coast. Precipitation is enhanced in the vicinity of the Alaskan panhandle, but is suppressed to the south. During cold event winters, the dominant 700 mb anomaly strongly resembles the PNA pattern, but with a reversed polarity. Most cold event winters are associated with below normal temperatures along the west coast, while precipitation significantly decreases in the Alaskan panhandle and increases to the south. Thus, the climate anomalies experienced along the Anglo‐American west coast during cold events are in the opposite sense to those of warm events.

Precipitation, and to a lesser extent temperature anomalies, are sensitive to minor fluctuations in the general placement and orientation of the PNA pattern, which in turn are related to shifts in the position of the polar front jet stream and associated storm track. Thus, a number of disparate climate anomalies are possible in the study area during warm event winters, depending upon the positioning of the long‐wave pattern over the north Pacific and North America.

Although the PNA and ‘reverse PNA’ patterns can occur in any winter, they are significantly more frequent during warm and cold events, respectively, than in other winters. The west coast temperature and precipitation anomalies associated with the PNA (‘reverse PNA’) during warm event (cold event) winters can occur during any winter displaying the PNA (‘reverse PNA’) pattern, regardless of the presence of a warm (cold) event in the equatorial Pacific. A dynamical model is proposed to explain the observed teleconnection between the Anglo‐American west coast and cold Southern Oscillation events.
Simulation of time series of temperature and precipitation over Eastern England by an atmospheric general circulation model
Authors: Reed D. N.
Published: February 2007

Time series of temperature and precipitation from a 3‐year integration of a 5‐level general circulation model (Corby et al., 1977) by the Dynamical Climatology branch of the U.K. Meteorological Office are studied. These are used to establish, and criticize, the ability of the model to simulate some aspects of the observed climate in a single grid box of the model (the eastern England grid box). Problems concerning the comparison of time series of model data with time series compiled from meteorological observations are discussed and some techniques for overcoming these problems developed.
The relationship of weather types to dust storm generation in Arizona (1965–1980)
Authors: Brazel A. J. , Nickling W. G.
Published: February 2007

A general classification of dust weather types for Arizona first‐order stations was developed using synoptic data derived from surface, 850 mb, and 500 mb pressure and wind characteristics from daily weather maps for 321 observed dust storms during 1965–1980. Four major dust weather types were identified: (1) frontal, (2) thunderstorm/convective, (3) tropical disturbance and (4) upper level/cut‐off low. Frontal dust storms (Type 1) occur most frequently during the late autumn, winter and spring and can be divided into two subtypes; pre‐frontal dust and post‐frontal dust. Dust storms generated by thunderstorm or strong convective activity (Type 2) are most frequent during the summer months and are typified by large scale pressure pattern variability, particularly at the upper levels of the troposphere. Dust storms associated with tropical disturbances (Type 3) are infrequent at all stations but are typically very intense, long lasting events. The upper level/cut‐off low type (Type 4) dust storms usually occur during May and June and from September to November and are associated with upper level split flow, where high amplitude ridging to the north and troughing to the south occurs across the western U.S.A. Although dust storms can be traced to specific synoptic events, the interannual variability of dust storms shows a strong correspondence to antecedent winter moisture variability, probably reflecting an overriding control by surface crusting and vegetative effects on dust generation.
Rotation of principal components
Authors: Richman Michael B.
Published: February 2007

Recent research has pointed to a number of inherent disadvantages of unrotated principal components and empirical orthogonal functions when these techniques are used to depict individual modes of variation of data matrices in exploratory analyses. The various pitfalls are outlined and illustrated with an alternative method introduced to minimize these problems via available linear transformations known as simple structure rotations. The rationale and theory behind simple structure rotation and Procrustes target rotation is examined in the context of meteorological/climatological applications. This includes a discussion of the six unique ways to decompose a rotated data set in order to maximize the physical interpretability of the rotated results.

The various analytic simple structure rotations available are compared by a Monte Carlo simulation, which is a modification of a similar technique developed by Tucker (1983), revealing that the DAPPFR and Promax k = 2 rotations are the most accurate in recovering the input structure of the modes of variation over a wide range of conditions. Additionally, these results allow the investigator the opportunity to check the accuracy of the unrotated or rotated solution for specific types of data. This is important because, in the past, the decision of whether or not to apply a specific rotation has been a ‘blind decision’. In response to this, a methodology is presented herein by which the researcher can assess the degree of simple structure embedded within any meteorological data set and then apply known information about the data to the Monte Carlo results to optimize the likelihood of achieving physically meaningful results from a principal component analysis.
A comparison of synoptic classification schemes based on ‘objective’ procedures
Authors: Key Jeff , Crane Robert G.
Published: February 2007

Various ‘objective’ methods of classifying the atmospheric circulation are compared in order to determine whether the different methods result in similar groupings of circulation types, and also to examine the question of how much subjectivity is present in each of the typing schemes. The results indicate a high degree of subjectivity within each approach and that the different classification schemes do give rise to the production of different synoptic types. A method which groups days based on the sum of squares difference between cases (Kirchhofer method) gives the best overall classification, but only classifies 80 per cent of the days. A technique that clusters days based on principal component scores gives a larger mean sum of squares difference between the type patterns and the individual cases, but classifies all of the days.
Diurnal variation of planetary radiation budget parameters from geostationary satellites
Authors: Pinker R. T. , Ewing J. A. , Gruber A.
Published: February 2007

Studies of diurnal variation in the planetary radiation budget parameters from space are possible only with observations from geosynchronous satellites. Such studies are necessary to establish possible bias in the radiation budget estimates derived currently from polar orbiting satellites. This paper outlines a preliminary approach to estimate the diurnal variation of the net radiation at the top of the atmosphere, using the Geostationary Operational Environmental Satellite (GOES) visible (0.55–0.75 μm) and IR window (10.5–12.5 μm) observations. Model development and analysis used GOES‐E data for the summer of 1982. This paper is the first to report monthly averaged diurnal variations in the planetary radiation budget parameters for several months. The possible error in the daily mean net radiation when derived from one observation per day instead of hourly observations, was also estimated. Computational experiments were conducted with different calibration techniques to assess the possible bias error in the quantities derived due to calibration.
A synoptic climatology of major avalanche winters in Norway
Authors: Fitzharris B. B. , Bakkehøi S.
Published: February 2007

A near continuous record of avalanche deaths in Norway is compiled for 130 years from 1855, and shows a distinct downward trend, but large variations from winter to winter, with a periodicity of 12–13 years. Twelve major avalanche winters are selected, and their synoptic climatology examined using Grosswetterlagen, an index of atmospheric circulation over southern Norway, and monthly sea level pressure anomaly maps. More than one climatological pattern is needed to explain these winters. Major avalanche winters tend to be cold in December and/or January, and have more meridional and less mixed weather types compared with minor avalanche winters. Some have enhanced north or east circulations associated with large anomalies in the semi‐permanent pressure systems. Others display intense anticyclonic blocking near Britain that maintains sustained west to north‐west airflows onto Norway. A switch in circulation pattern from these to a more southerly regime is also important. These aspects of synoptic climatology are related to the mechanisms for producing big avalanches.
Specification of monthly mean surface temperature anomalies in Europe and Asia from concurrent 700 mb monthly mean height anomalies over the Northern Hemisphere
Authors: Klein William H. , Yang Runhua
Published: February 2007

Specification equations for the monthly mean air temperature anomalies at 115 surface stations in Eurasia are derived by applying a stepwise forward screening procedure to the simultaneous monthly mean 700 mb height anomalies at 134 grid points in the northern hemisphere and the previous month's local temperature. These equations explain about 65 per cent of the temperature variance by an average of only 4.7 variables, but with marked regional, seasonal and month‐to‐month variations. The main properties of the equations are highlighted by means of several maps and graphs that delineate important spatial and temporal variations.

The average properties of the specification equations in the European sector closely resemble those derived previously for North America. However, the results are consistently poorer for stations in Asia, not only for the annual mean, but also during each of the four seasons. Furthermore, the phases of seasonal variation are opposite in Europe and Asia. In both sectors, however, the equations are better in winter than in summer at coastal stations, but the reverse is true at continental stations. The average error in specifying monthly average surface temperature from perfect 700 mb height forecasts should be less than 0.9°C in Europe and 1.2°C in Asia about two‐thirds of the time.