Urbanization and seasonal temperature trends: observational evidence from a data‐sparse part of North America

Abstract:Reliable time-series is the basic ingredient when analysing climatic changes. However, the errors in real data are frequently of the same order as the signal being sought. Therefore, the available long-term monthly series of Spanish minimum and maximum temperatures have been compiled from the late 19th century on, in order to compile a high-quality data set. The series are organized into climatically homogeneous regional groups and, in each group, the detection and adjustment is based on relative homogeneity and an analysis of the stationarity of the whole set of temperature-difference series. These series are scanned with moving t, Alexandersson, and Mann-Kendall tests. The detected inhomogeneities are adjusted by weighted averages of the regional series. The method is iterative and advances in steps of detection, adjustment, and actualization. Individual inhomogeneous data are discarded and gaps are filled by similar weighted multiple means.For the analysis of the temperature evolution in the Iberian Peninsula, each region is finally represented by one local series and the regional average. The urban effect on minimum temperatures is adjusted by an empirical method, and for Madrid also by a correction derived from new homogenized data. Generally, rigorous homogeneity cannot be achieved because the initial data quality is deficient in many cases and metadata are sparse. Nevertheless, the data homogeneity and quality has been considerably enhanced: the total error margin in a series is of the order of 0.3°C-0.4°C, under consideration of a worst-case error accumulation. On the other hand, the number of inhomogeneities is considerable and their average amplitude is of the order of 1°C reflecting the much larger error margin in the raw data. The homogenized dataset compiled constitutes an important basis for the subsequent detection of thermal changes in Spain in the last 130 years, on a clearly higher confidence level than before.

Section: The Empirical Urban Adjustmentsupporting

confidence: 79%

Homogenization of long‐term monthly Spanish temperature data

Staudt

Esteban‐Parra

Castro‐Díez

2007

“…In developing the data set, we attached substantial weight to the concept that the impact of urban warming on SAT records is generally proportional to population (e.g. Karl et al, 1988;Englehart and Douglas, 2003). Consequently, the decision was made to include only stations that are located in .…”

Section: Data Set Developmentmentioning

confidence: 99%

“…Recently, this line of inquiry has been extended to include much of northern * Correspondence to: Phil J. Englehart,3500 N 57th St.,Kansas City,KS 66104,USA; Mexico and the border region of the USA (Englehart and Douglas, 2003). Several factors may explain why SAT variability for Mexico has not received more research attention.…”

Section: Introductionmentioning

confidence: 99%

Characterizing regional‐scale variations in monthly and seasonal surface air temperature over Mexico

Englehart

Douglas

2004

Self Cite

Monthly and seasonal variations in surface air temperature (SAT) over Mexico have not received much research attention, a situation partly reflecting the lack of a coherent historical data set. As a step toward rectifying the data gap, this study outlines the development of a gridded monthly (2.5°× 2.5°lat.-long.) SAT data set for Mexico. Using the data set, we investigate several basic dimensions of SAT variability. Our analysis demonstrates that much of the variability can be compactly expressed in terms of four regions which are physically plausible with respect to the country's climatology. Not surprisingly, persistence is an important component of regional SAT variability. Evaluated month to month, persistence tends to be greatest during the warm season, whereas across seasons there is evidence for persistence of warm season anomalies into the following cool season, behaviour that is consistent with positive feedback relationships between SAT, rainfall and land surface conditions. The regional time series display longer period variability that is partially linked to the state of the large-scale, slowly evolving climate modes of the Atlantic multidecadal oscillation and the Pacific decadal oscillation. Analyses are also presented to describe teleconnections between SAT and the El Niño-southern oscillation phenomena, and SAT and other large-scale atmospheric modes, such as the Pacific North American pattern and the North Atlantic oscillation.

“…where no buildings existed previously, was monitored by Landsberg and Maisel (1972), who reported that over a period of 3 years, a heat island of up to 4.5°C appeared as the newly established town of Columbia, Maryland grew to a population of 10 000 residents. Analyses of longterm temperature records in several locations -Turkey (Tayanc and Toros, 1997); Alaska (Magee et al, 1999); Athens (Philandras et al, 1999); South Korea (Choi et al, 2003); and North America (Engelhart and Douglas, 2003) -show an increase in the UHI effect paralleling increasing urbanisation.…”

Section: Introductionmentioning

confidence: 99%

Intra‐urban differences in canopy layer air temperature at a mid‐latitude city

Erell

Williamson

2006

133

Abstract:Detailed meteorological measurements were carried out in two urban street canyons in central Adelaide and at two reference sites in a suburban location and at an exposed site near the middle of the city for an extended period of nearly a year. The meteorological records revealed substantial differences between air temperature in the urban street canyons and both reference sites. The nocturnal urban heat island observed in most cities was noted in Adelaide street canyons, too. However, the frequent occurrence of a daytime cool island during summer, albeit much weaker than the night-time phenomenon, is less expected. Both phenomena are attributed at least in part to the increase in surface area participating in energy exchanges with the atmosphere in an urban street canyon compared to a typical rural site, and hence in an increase in the effective thermal mass. The presence of additional thermal mass is manifested not only in the dampening of the diurnal temperature range in the city, but also in a noticeable time lag in the maximum intensity of the daytime cool island. The measurements also demonstrate an observable difference in the daily progression of air temperature between a north-south street canyon and an adjacent east-west oriented street.