Continuity of climatological observations with automation ‐ temperature and precipitation amounts from AWOS (Automated Weather Observing System)

Milewska, Ewa J.; Hogg, W. D.

doi:10.3137/ao.400304

Cited by 20 publications

(9 citation statements)

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“…The number of stations with temperature and precipitation observations decreased considerably after 2005, mainly as a result of relocation and closure of traditional manual observation stations and the introduction of automated systems. Work is in progress for joining past manual and current automated weather observations in order to preserve continuity for climate trends and monitoring (Milewska et al, 2018;Milewska & Hogg, 2002;Milewska & Vincent, 2016;Vincent, Milewska, Wang, & Hartwell, 2018). Results regarding the changes in very warm and very cold temperatures (defined by the summer and winter 95th and 5th percentiles of tmax and tmin) have revealed three important pieces of information.…”

Section: Discussionmentioning

confidence: 99%

Changes in Canada's Climate: Trends in Indices Based on Daily Temperature and Precipitation Data

et al. 2018

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Trends in indices based on daily temperature and precipitation are examined for two periods: 1948-2016 for all stations in Canada and 1900-2016 for stations in the south of Canada. These indices, a number of which reflect extreme events, are considered to be impact relevant. The results show changes consistent with warming, with larger trends associated with cold temperatures. The number of summer days (when daily maximum temperature >25°C) has increased at most locations south of 65°N, and the number of hot days (daily maximum temperature >30°C) and hot nights (daily minimum temperature >22°C) have increased at a few stations in the most southerly regions. Very warm temperatures in both summer and winter (represented by the 95th percentile of their daily maximum and minimum temperatures, respectively) have increased across the country, with stronger trends in winter. Warming is more pronounced for cold temperatures. The frost-free season has become longer with fewer frost days, consecutive frost days, and ice days. Very cold temperatures in both winter and summer (represented by the 5th percentile of their daily maximum and minimum temperatures, respectively) have increased substantially across the country, again with stronger trends in the winter. Changes in other temperature indices are consistent with warming. The growing season is now longer, and the number of growing degree-days has increased. The number of heating degree-days has decreased across the country, while the number of cooling degree-days has increased at many stations south of 55°N. The frequency of annual and spring freeze-thaw days shows an increase in the interior provinces and a decrease in the remainder of the country. Changes in precipitation indices are less spatially coherent. An increase in the number of days with rainfall and heavy rainfall is found at several locations in the south. A decrease in the number of days with snowfall and heavy snowfall is observed in the western provinces, while an increase is found in the north. There is no evidence of significant changes in the annual highest 1-day rainfall and 1-day snowfall. The maximum number of consecutive dry days has decreased, mainly in the south. RÉSUMÉ [Traduit par la rédaction] Nous examinons les tendances d'indices fondés sur les températures et les précipitations quotidiennes pour deux périodes : de 1948 à 2016, pour toutes les stations au Canada, et de 1900 à 2016, pour les stations du sud du pays. Ces indices, dont certains représentent des événements extrêmes, sont considérés comme pertinents sur le plan des impacts. Les résultats montrent des changements en accord avec un réchauffement et des tendances prononcées associées à des températures froides. Le nombre de jours estivaux (lorsque la température quotidienne maximale > 25°C) a augmenté à la plupart des sites au sud de 65°N, et les nombres de jours chauds (température quotidienne maximale >30°C) et de nuits chaudes (température quotidienne minimale >22°C) ont augmenté à quelques stations, dans les régions les plus au ...

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Section: Discussionmentioning

confidence: 99%

Changes in Canada's Climate: Trends in Indices Based on Daily Temperature and Precipitation Data

et al. 2018

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“…Overall, no systematic biases were found as a result of automation as far as the instrumental systems were concerned. Based on a limited number of pairsites, the Automatic Weather Observing Systems (AWOS) have shown slightly warmer temperatures, up to 0.2°C, because of the unaspirated Stevenson screen being cluttered with additional devices (Milewska and Hogg, 2002). At Annual mean of tmean anomalies for Canada, 1948Canada, -2018.…”

Section: Discussionmentioning

confidence: 99%

“…Because many of the RCS sites have a relatively short period of data, it was often necessary to merge the RCS observations with those from the traditional older sites with longer records. To preserve the continuity of records during the modernization of the observing network, the MSC dedicated great effort and expense to installing new RCS sites in close proximity to older sites to collect parallel observations (Milewska and Hogg, 2002;Milewska and Vincent, 2016;Vincent et al, 2018b). In this study, pair-sites data (parallel observations) are used, when available, to determine whether an artificial shift is created at the joining date when the observations of two sites are merged; these data are also used to estimate the adjustments needed to homogenize the data when necessary.…”

Section: Introductionmentioning

confidence: 99%

“…e Detecting Shifts Using Parallel Observations at Pairsites The collection of parallel observations has gradually become standard practice in recent years in Canada. New RCS sites were installed in close proximity to traditional sites that had been operational longer with the purpose of collecting parallel observations (Milewska and Hogg, 2002;Milewska and Vincent, 2016). There are also a number of older sites where concurrent observations exist at pair-sites (old rural and airport sites for example), and these data were previously used for developing mathematical relations and validating daily temperature adjustments (Vincent et al, 2018b).…”

Section: Introductionmentioning

confidence: 99%

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A Third Generation of Homogenized Temperature for Trend Analysis and Monitoring Changes in Canada’s Climate

Vincent

Hartwell

2020

Atmosphere-Ocean

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This study presents the development of a new dataset of homogenized temperature for use in trend analysis and monitoring climate change in Canada. This dataset contains daily data for 780 locations across the country: 508 locations with an active station (current observations) and long record (starting prior to 1990); 53 locations with an active station and short record (starting after 1990); and 219 locations with no current observations (station closed) but with more than 30 years of data. Daily observations from nearby sites were often merged into a single record to create a long time series. This new dataset includes observations taken at Reference Climate Stations and from the Canada Aviation Weather Services, which are used to extend past climate observations into recent times. First, the data were quality controlled. The daily minimum temperature was adjusted for the change in observing time at principal stations in 1961. Parallel daily data were used to detect non-climatic shifts when the observations from nearby sites were merged. Series of annual and seasonal mean temperatures were tested for homogeneity. Daily temperatures were adjusted using a quantile-matching procedure if needed. Two main causes of data inhomogeneity affecting the trends over the 1948-2018 and 1900-2018 periods were identified. First, the change in observing time in 1961 introduced a cold bias in the annual means of the daily minimum temperatures after 1961. Second, merging observations from airport stations with older records has often created an artificial decreasing shift in the unadjusted data because of the better exposure of the instruments at airport stations. This new homogenized dataset shows a slightly stronger warming than the unadjusted data: the trend in the annual mean temperature for Canada has changed from 1.69°to 1.74°C for 1948-2018, and the trend for southern Canada has changed from 1.32°to 1.62°C for 1900-2018 because of all the adjustments applied to daily temperature in this study. RÉSUMÉ [Traduit par la rédaction] Cette étude décrit la création d'un nouvel ensemble de données de température homogénéisées destiné à l'analyse des tendances et à la surveillance des changements climatiques au Canada. Cet ensemble contient les données quotidiennes de 780 sites canadiens: 508 stations actives (rapportent actuellement) possédant un long historique de relevés (commençant avant 1990); 53 stations actives possédant un court historique de relevés (commençant après 1990); et 219 sites sans observations actuelles (stations fermées), mais comptant plus de 30 ans de données. Dans plusieurs cas, nous avons fusionné les observations quotidiennes de sites voisins afin de créer une longue série temporelle unique. Ce nouvel ensemble de données comprend des observations prises aux stations climatologiques de référence ou par les Services météorologiques à l'aviation du Canada, et sert à prolonger les observations climatologiques passées jusqu'à des périodes récentes. Tout d'abord, les données ont fait l'objet d'un contrôle de qual...

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“…Nonetheless, a few innovative techniques have been recently developed [ Della‐Marta and Wanner , 2006; Toreti et al , 2010; Wang et al 2010; Mestre et al , 2011] and have been applied to daily temperatures [ Kuglitsch et al , 2009; Brown et al , 2010; Nemec et al , 2012]. Still, more work is needed to evaluate and compare methods for homogenizing daily temperatures and especially to determine the impact of automation [ Guttman and Baker , 1996; Milewska and Hogg , 2002; Sun et al , 2005]. The QM algorithm using a reference series is currently being tested for adjusting daily temperature in a region where the neighboring series can be relatively far and of a weaker correlation with the candidate series (such as found in Canada).…”

Section: Discussionmentioning

confidence: 99%

A second generation of homogenized Canadian monthly surface air temperature for climate trend analysis

et al. 2012

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[1] This study presents a second generation of homogenized monthly mean surface air temperature data set for Canadian climate trend analysis. Monthly means of daily maximum and of daily minimum temperatures were examined at 338 Canadian locations. Data from co-located observing sites were sometimes combined to create longer time series for use in trend analysis. Time series of observations were then adjusted to account for nation-wide change in observing time in July 1961, affecting daily minimum temperatures recorded at 120 synoptic stations; these were adjusted using hourly temperatures at the same sites. Next, homogeneity testing was performed to detect and adjust for other discontinuities. Two techniques were used to detect non-climatic shifts in de-seasonalized monthly mean temperatures: a multiple linear regression based test and a penalized maximal t test. These discontinuities were adjusted using a recently developed quantile-matching algorithm: the adjustments were estimated with the use of a reference series. Based on this new homogenized temperature data set, annual and seasonal temperature trends were estimated for Canada for 1950-2010 and Southern Canada for 1900-2010. Overall, temperature has increased at most locations. For 1950-2010, the annual mean temperature averaged over the country shows a positive trend of 1.5 C for the past 61 years. This warming is slightly more pronounced in the minimum temperature than in the maximum temperature; seasonally, the greatest warming occurs in winter and spring. The results are similar for Southern Canada although the warming is considerably greater in the minimum temperature compared to the maximum temperature over the period 1900-2010.Citation: Vincent, L. A., X. L. Wang, E. J. Milewska, H. Wan, F. Yang, and V. Swail (2012), A second generation of homogenized Canadian monthly surface air temperature for climate trend analysis,

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Continuity of climatological observations with automation ‐ temperature and precipitation amounts from AWOS (Automated Weather Observing System)

Cited by 20 publications

References 5 publications

Changes in Canada's Climate: Trends in Indices Based on Daily Temperature and Precipitation Data

Changes in Canada's Climate: Trends in Indices Based on Daily Temperature and Precipitation Data

A Third Generation of Homogenized Temperature for Trend Analysis and Monitoring Changes in Canada’s Climate

A second generation of homogenized Canadian monthly surface air temperature for climate trend analysis

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