Within-type variability of 700 hPa winter circulation patterns over the Lake Superior basin

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.

show abstract

“…Yarnal, 1993;Brinkmann, 1999b). The NCEPR data are on a 2.5°× 2.5°grid, but the radiosonde data used in this study were not gridded.…”

Section: Discussionmentioning

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

View full text Add to dashboard Cite

show abstract

“…The analysis was restricted to the winter months of a 25 yr period (December 1962to February 1987 for which daily 700 hPa maps had been classified in an earlier study (Brinkmann 1999a;hereafter B99a). The data set thus consists of 2250 d or 75 mo.…”

Section: Methodsmentioning

confidence: 99%

Local versus remote grid points in climate downscaling

Brinkmann

2002

Clim. Res.

View full text Add to dashboard Cite

The association between daily as well as monthly winter precipitation and concurrent 700 hPa heights for 3 different North American precipitation regimes was examined using correlation fields and a typing of daily 700 hPa height patterns. Wet days, regardless of circulation type, were found to be associated with negative height anomalies immediately to the west or northwest of the precipitation regions, at the 'local' grid point. These small-scale height anomalies were found to represent traveling short waves that were missed by the circulation typing scheme. The correlation fields between monthly precipitation and concurrent 700 hPa heights revealed a westward shift of the height minima to a location west of 100°W, to a 'remote' grid point. The nature of these remote minima was examined using the 10 wettest and 10 driest months. Decomposition of the height anomalies at the remote grid points into between-type and within-type contributions revealed that while some of the negative heights during wet months are due to an increase in the frequency of circulation patterns with below normal heights (such as troughs or weak ridges), more than two-thirds of the contribution comes from height depressions superimposed upon the larger-scale patterns and most of these are associated with positive vorticity. This leads to the conclusion that the correlation minima west of 100°W at the monthly time scale reflect the frequent generation of short waves during wet months over the well-known North American cyclogenetic region east of the Rocky Mountains. These results have 2 implications with respect to statistical downscaling. First, regarding techniques designed to extract information from a single grid point: the optimum grid point location may be a function of the time scale under consideration. Second, regarding techniques designed to extract information from large-scale circulation patterns: the difficulties in capturing the very important but small short waves limit their usefulness. KEY WORDS: Precipitation · 700 hPa · Circulation pattern typing · North America · DownscalingResale or republication not permitted without written consent of the publisher Clim Res 21: 27-42, 2002 cal to this approach since the circulation features of significance to the local climate need to be captured. Most investigators place the window over and to the west of the area of interest because weather systems travel from west to east. Using information from the nearest grid point also makes physical sense because the atmospheric conditions at the nearest point should be most similar to those over the area of interest. However, it has been shown that for some parts of the country the strongest correlation between local precipitation and geopotential heights is not at the nearest (local) but at a remote grid point (generally to the west of the area of interest).Specifically, Stidd (1954) computed correlation fields between 700 hPa heights and a series of state-wide precipitation totals for winter months and found that almost all of ...

show abstract

“…3, previous studies suggested that global warming might induce changes in circulation patterns that are linked to European temperatures, in terms of their frequencies but also modifying their underlying mechanisms (Belleflamme et al 2015;Brinkmann 1999). Therefore, it is important to highlight that global warming would influence both, frequency and within-types changes (Cahynová and Huth 2016).…”

Section: Weather Types Variations and Temperature Changesmentioning

confidence: 97%

Assessment of an extended version of the Jenkinson–Collison classification on CMIP5 models over Europe

2017

View full text Add to dashboard Cite

the warmer seasons over Southeast and Southwest Europe, respectively. Our results indicate that in winter the Westerly type has significant impacts on positive anomalies of maximum and minimum temperature over most of Europe. Except in winter, the warmer temperatures are linked to Easterlies, Anticyclonic and Low Flow conditions, especially over the Mediterranean area. Furthermore, we show that changes in the frequency of weather types represent a minor contribution of the total change of European temperatures, which would be mainly driven by changes in the temperature anomalies associated with the weather types themselves.

show abstract

Within-type variability of 700 hPa winter circulation patterns over the Lake Superior basin

Cited by 22 publications

References 26 publications

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

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

Local versus remote grid points in climate downscaling

Assessment of an extended version of the Jenkinson–Collison classification on CMIP5 models over Europe

Contact Info

Product

Resources

About