Cold Season Temperature Research Articles

Relationships between circulation strength and the variability of growing-season and cold-season climate in northern and central Europe

This paper examines variability in surface climate and the relationship with two circulation indices using recently produced 200–250 year long European daily and monthly climatic series. Assessments are made of the influence of circulation indices (zonal over western Europe and average pressure over central Europe) on regional temperature, precipitation and drought series for northern and central Europe. Changes in the circulation are shown to be very important during the winter in northern Europe, but only over western and central Europe in summer. Circulation indices in winter, however, only explain up to 25% of surface-climate variability and, except for the British Isles, do not explain any decadal and longer timescale variability in summer. Extreme temperatures and growing-season and frost-season durations and degree-day series are calcu lated for four sites (Central England, Stockholm, Uppsala and St. Petersburg). Degree-day counts are shown to be very strongly correlated (r > 0.9) to average extended summer (‘growing’ season, May to September) and extended winter (‘frost’ season, October to April) temperatures. Durations of the growing and frost seasons are only weakly correlated (r ~ 0.2–0.4) with the appropriate extended seasonal temperatures or degree-day counts. Warmer growing/frost seasons, therefore, need not necessarily be longer/shorter. Counts of extremely warm days in each year are more highly correlated with the growing-season mean temperature than with coldseason temperature. Similarly, counts of extremely cold days in each year are more highly correlated with cold-season temperature than with growing-season temperature. Both the growing-season temperature and the corresponding degree-day counts clearly show warmer temperatures over all series in Fennoscandia before 1860. Over central Europe, and for the Central England temperature series, growing seasons now are of similar warmth to those before 1860. Annually averaged temperatures across the three regions indicate long-term warming which is, however, almost entirely the result of warming during the October to April period.

Variability and trends of sub-continental scale surface climate in the twentieth century. Part II: AOGCM simulations

This work presents an analysis of simulated temperature and precipitation variability and trends throughout the twentieth century over 22 land regions of sub-continental scale in the HADCM3 and HADCM2 (two realizations) coupled models. Regional temperature biases in the HADCM3 and HADCM2 are mostly in the range of –5 K to +3 K for the seasonal averages and –3 K to +2 K for the annual average. Seasonal precipitation biases are mostly in the range of –50% to 75% of present day precipitation, with a tendency in both models to overpredict cold season precipitation. Except for cold season temperature in mid- and high-latitude Northern Hemisphere regions, the average climatology of the HADCM2 and HADCM3 is of comparable quality despite the lack of an ocean flux adjustment in the HADCM3. Both models show warming trends of magnitude in line with observations, although the observed inter-regional patterns of warming trend are not well reproduced. Measures of temperature and precipitation interannual to interdecadal variability in the models are in general agreement with observations except for Northern Hemisphere summer temperature variability, which is overestimated. The models somewhat underestimate the inter-decadal variations in interannual variability measures observed during the century and overestimate the range of anomalies. Both models tend to overpredict the occurrences of short persistences (1–3 years) and underpredict the occurrence and maximum length of long persistences (greater than three years), which is an indication of a deficiency in the simulation of long-lived anomaly regimes. Compared to observations, the models produce a higher magnitude of temporal anomaly correlation across regions and correlation between temperature and precipitation anomalies for a given region. This suggests that local processes that may be effective in decoupling the observed regional anomalies are not captured well. Overall, the variability measures in the HADCM2 and HADCM3 are of similar quality, indicating that the use of a flux correction in the HADCM2 does not strongly affect the regional variability characteristics of the model.

Impacts of 1997—98 El Niño Generated Weather in the United States

This paper assesses the major impacts on human lives and the economy of the United States resulting from weather events attributed to El Niño 1997–98. Southern states and California were plagued by storms, whereas the northern half of the nation experienced much above normal cold season temperatures and below normal precipitation and snowfall. Losses included 189 lives, many due to tornadoes, and the major economic losses were property and crop damages from storms, loss of business by the recreation industry and by snow removal equipment/supplies manufacturers and sales firms, and government relief costs. Benefits included an estimated saving of 850 lives because of the lack of bad winter weather. Areas of major economic benefits (primarily in the nation's northern sections) included major reductions in expenditures (and costs) for natural gas and heating oil, record seasonal sales of retail products and homes, lack of spring flood damages, record construction levels, and savings in highway-based and airline transportation. Further, the nation experienced no losses from major Atlantic hurricanes. The net economic effect was surprisingly positive and less government relief was needed than in prior winters without El Niño influences. The estimated direct losses nationally were about $4 billion and the benefits were approximately $19 billion. The highly accurate long-range predictions issued by the Climate Prediction Center in the summer of 1997 for the winter conditions led to some major benefits. For example, the predictions led California to conduct major mitigation efforts and the results suggest these led to a major reduction in losses. Several utilities in the northern United States used the winter forecasts to alter their strategy for purchasing natural gas, leading to major savings to their customers.

Variations of mean cold season temperature, precipitation and snow depths during the last 100 years in the former Soviet Union (FSU)

Variations of temperature, precipitation and snow depths during the last 50–100 years, up to 1984, are investigated for mean cold season values (November to April) for 110 locations in the Former Soviet Union (FSU). Following quality checking, statistical analyses are performed on the data. There is cold season warming after 1953 or after 1966 over almost all the FSU apart from eastern Siberia, but temperature variations significantly affect the mean snow depths only in some sensitive areas of the Caucasus, central Asia, and the western European territory. Mean snow depth time series reveal contrasting local trends. Higher precipitation and snow depths are measured in eastern European Russia from 50° to 65 °N and in some areas of western Siberia at the beginning of the twentieth century. Otherwise, precipitation variations have little influence on the mean cold season snow depths over much of the FSU after 1930. Some predominant periodicities are detected for mean cold season temperature, but not for precipitation and snow depths.

Winter season temperature outlooks by objective methods

An attempt was made to predict categories of cold season temperature for 19 cities in the central and eastern United States. Classification equations were developed by using discriminant analysis based on 23 years of historical data (1949–1971) in which the discriminating variables (predictors) are principal components of the mean 700‐mbar heights during November over the northern hemisphere; sea surface temperatures of the eastern North Pacific, eastern tropical Pacific, and North Atlantic oceans; and a southern oscillation index for the fall season. Separate sets of equations were developed for varying duration of the prediction, from 1 to 4 months, and for two or three categories of mean temperature. An independent sample of years was reserved for testing the reliability of the equations. ‘Forecasts’ made by each set of equations were compared with observed categories of mean temperature for five recent winters (1972–1976), not included in the dependent sample. The sets of equations derived for discriminating between above‐ and below‐normal mean temperatures for the 4‐month season (December‐March) and between three groups for the 3‐month winter season (December‐February) performed significantly better than chance expectation. Values of 63% and 45%, respectively, were correct. Additionally, when the persistence forecast category was the same as the forecast category of our model for the December‐March period in the two‐group discrimination, the prediction category was correct 86% of the time over the five test winters. This situation occurred, on the average, for about half the cities in each year. These results indicate that objective methods, using statistical relationships, can be useful for winter temperature predictions, but considerable improvement is still needed.

On a technique to describe crop and weather relationships

A stepwise linear regression technique is applied to the description of hay yields in Iceland with nitrogen application, last year's yield, mean warm season and cold season temperatures. The paper sets out to show that useful structural equations can be obtained for a crop in a marginal region of the earth's surface. It should therefore be of value over far wider areas of the globe.

ARCTIC ICE AND SEA TEMPERATURE ANOMALIES IN THE NORTHEASTERN NORTH ATLANTIC AND THEIR SIGNIFICANCE FOR SEASONAL FORESHADOWING LOCALLY AND TO THE EASTWARD1

An analysis was made of a combined 6 yr with an extreme northerly ice limit and relatively high sea temperatures and 6 yr with an extreme southerly ice limit and relatively low sea temperatures, respectively, in the northeastern North Atlantic during April–September and the contemporary and Subsequent October–March air temperatures and precipitation locally and to the eastward. The results obtained indicate a relationship with the contemporary and, because of the persistence of the circulation, also the subsequent cold season temperature and precipitation progressively later in Iceland, Europe, the Middle East, northern Pakistan, and India, in keeping with the general movement of weather systems from west to east in the middle and high latitudes. One may expect, following further study of the relationship from a consideration of anomalies of individual years, that a basis for foreshadowing the cold season temperature and precipitation in the northeastern North Atlantic, Europe, the Middle East, northern Pakistan, and India will become available early in October.