Climate Zones of the Conterminous United States Defined Using Cluster Analysis

Fovell, Robert G.; Fovell, Mei-Ying C.

doi:10.1175/1520-0442(1993)006<2103:czotcu>2.0.co;2

Cited by 328 publications

(211 citation statements)

References 22 publications

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“…A more detailed spatial analysis, eventually based on statistical clusterization, would require a larger number of stations' data which are not available, and should also involve other variables besides temperature (Fovell and Fovell, 1993).…”

Section: Data Control and Indices Calculationmentioning

confidence: 99%

Changes in temperature extremes over Italy in the last 44 years

Toreti

Desiato

2007

Intl Journal of Climatology

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Changes in temperature extremes over Italy from 1961 to 2004 were evaluated on the basis of minimum and maximum temperatures measured by 49 synoptic stations uniformly distributed over the country. A set of extreme temperature indices of the Commission for Climatology/Climate Variability and Predictability (CCl/CLIVAR) Working Group on Climate Change Detection was calculated and statistically analysed in order to detect the presence of trends and quantify the variations of the indices for different time periods. Most of the indices, averaged over all stations, show a cooling trend until the end of the 1970s followed by a more pronounced warming trend in the last 25 years. The net variation of the indices reflects an increase in the extremes of the temperature distribution. Among the most significant results, an average increase of 12.3 summer days and 12.4 tropical nights in the overall 44 years are estimated. No significant differences between northern, central and southern Italy are found for most indices, indicating that the trends originate from large-scale climate features; however, the largest increase of tropical nights is observed at coastal stations.

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Section: Data Control and Indices Calculationmentioning

confidence: 99%

Changes in temperature extremes over Italy in the last 44 years

Toreti

Desiato

2007

Intl Journal of Climatology

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“…This multivariate method has come to be recognized as an effective statistical tool to deal with tasks as grouping time series, climatological regions, weather events, etc. (Fovell and Fovell 1993;Gramsch et al 2006;Pires et al 2008a, b). For a detailed description, see Wilks (2006).…”

Section: Periods and Sampling Sitesmentioning

confidence: 99%

SO2 in Beirut: air quality implication and effects of local emissions and long-range transport

Afif

Chélala

Borbon

et al. 2008

Air Qual Atmos Health

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While sulfur dioxide (SO 2 ) emissions have been dramatically restricted in the past few decades, some cities in developing countries still encounter high pollution levels. This makes it essential to implement an air quality monitoring network in these sensitive regions. Results from a program of measuring groundlevel concentration of SO 2 (from December 2004 till July 2006) at 22 curbside and background sites within the city of Beirut (Lebanon) are presented for the first time. Four-week sampling period measurements were made over 20 periods for all sites by passive sampling. Low SO 2 concentrations were observed (3.1 parts per billion on average for the whole period). This value is among the lowest observed in urban areas worldwide. Thus, Beirut is not polluted by SO 2 on an annual basis. Highest concentrations were measured in winter time, resulting from low height of the boundary layer and higher emissions of SO 2 (e.g., heating). Cluster analysis revealed two different SO 2 variation patterns over the city (high-and low-level patterns), highlighting the effects of local sources location and wind direction variability on SO 2 distribution. Analysis of seasonal variations pointed out a springtime SO 2 maximum in 2005. Beside local sources, long-range transport can account for an important source of SO 2 in Beirut, explaining around 50% of SO 2 levels within the city.

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“…The similarity is taken as the average of these squared distances over all observations within the two clusters. One of the most difficult problems in the application of cluster analysis is the determination of the proper number of clusters (Kalkstein et al, 1987;Fovell and Fovell, 1993). In this analysis, several clustering 'cut-off rules' including the pseudo-F statistic (Calinski and Harabasz, 1974) and simple plots of cluster merging level versus number of clusters are applied.…”

Section: Development Of the Synoptic Classificationsmentioning

confidence: 99%

Evaluation of the NCEP–NCAR reanalysis in terms of synoptic‐scale phenomena: a case study from the Midwestern USA

Schoof

Pryor

2003

Intl Journal of Climatology

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We evaluate the ability of the National Centers for Environmental Prediction (NCEP)-National Center for Atmosphere Research (NCAR) reanalysis to represent the synoptic-scale climate of the Midwestern USA relative to radiosonde data. Independent, automated synoptic classifications, based on rotated principal component analysis (PCA) of 500 hPa geopotential heights, 850 hPa air temperatures, and 200 hPa wind speeds and a two-step clustering algorithm, result in a 15-type NCEP-NCAR synoptic classification and a 14-type radiosonde classification. The classifications are examined in terms of similarities and differences in the modes of variance manifest in the PCA solutions, the spatial patterns and variability of input variables within each weather type, and the temporal variability of the occurrence of each weather type. The classifications are then compared in terms of these characteristics and the degree of mutual class occupancy. Although the classifications identify a number of the same weather types (in terms of the input data, PCA solution, and mutual occupancy), the correspondence is imperfect. To assess whether the differences in the classifications are due to errant assignment of data to clusters or to differences in the fundamental modes present in the data sets as represented by the PC loadings and scores, a third targeted classification is undertaken that categorizes the NCEP-NCAR reanalysis data according to the radiosonde PCA solution. This classification exhibits a higher degree of similarity to that derived using the radiosonde data (in terms of both interpretability and mutual class occupancy), but the solutions still exhibit considerable differences. It is probable that the discrepancies are partly a function of the differing data structures and densities, but they may also reflect differences in the intensity of synoptic-scale phenomena as manifest in the data sets.

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Climate Zones of the Conterminous United States Defined Using Cluster Analysis

Cited by 328 publications

References 22 publications

Changes in temperature extremes over Italy in the last 44 years

Changes in temperature extremes over Italy in the last 44 years

SO2 in Beirut: air quality implication and effects of local emissions and long-range transport

Evaluation of the NCEP–NCAR reanalysis in terms of synoptic‐scale phenomena: a case study from the Midwestern USA

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