Spatial and Temporal Fluctuations of Monthly Raidfall in the British Isles and Variations in the Mid‐latitude Westerly Circulation

Mayes, Julian

doi:10.1002/(sici)1097-0088(199605)16:5<585::aid-joc24>3.0.co;2-#

Cited by 47 publications

(32 citation statements)

References 24 publications

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“…This is most marked at western sites, which also exhibit a concurrent increase in winter (DJF) precipitation totals since the mid-1970s. This evidence supports the conclusions of Mayes (1996), of recent enhanced seasonality of precipitation. However, unlike evidence from Ireland (Kiely, 1999), there are no significant changes in annual precipitation totals, even at western sites.…”

Section: Discussionsupporting

confidence: 91%

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Precipitation and the North Atlantic Oscillation: a study of climatic variability in northern England

Fowler

Kilsby

2002

Intl Journal of Climatology

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Variations in precipitation in Yorkshire, UK, are linked to large-scale atmospheric circulation using the North Atlantic Oscillation (NAO) index, objective Lamb weather types, and long-term seasonal and annual precipitation indices at seven sites. Since the 1960s, a significant decrease in summer precipitation has been observed across the region, with increasing winter precipitation at western locations since 1970. At western sites, precipitation is highly correlated to the NAO, with positive and negative winter-NAO indices producing anomalies from the long-term winter precipitation average of 112% and 77% respectively. The recent winter half-year precipitation increase is concentrated in March and related to a large increase in monthly NAO and the increased occurrence of westerly weather types. The decrease in summer precipitation, however, is caused by both declining receipt from westerly weather types and their decreased occurrence. This is significantly correlated to a decreasing summer index for the NAO. The NAO, the frequency of weather types and precipitation totals are all intimately linked on an annual and monthly time scale. Strong connections between winter precipitation and the NAO may prove very important, particularly in western Yorkshire where most surface water supplies are located. If the NAO can be predicted using sea-surface temperature, it may allow the estimation of winter reservoir replenishment in western Yorkshire a few months in advance. This may provide an important predictor of future hydrological drought episodes and facilitate forward planning and management of water resource systems located in climatologically similar regions of the UK.

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Section: Discussionsupporting

confidence: 91%

“…This produced results that accord with those of other researchers (e.g. Mayes, 1996). The DJF/JJA ratio was the highest of the 123 year record in 1995, and at 4.04, almost double the second-placed 1994.…”

Section: Inter-annual and Inter-seasonal Variabilitysupporting

confidence: 91%

Precipitation and the North Atlantic Oscillation: a study of climatic variability in northern England

Fowler

Kilsby

2002

Intl Journal of Climatology

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“…Mayes (1996) observed an increase in autumn and winter rainfall in northern and western areas of the UK between 1941-1970 and 1961-1990 periods, and other authors have observed an enhanced seasonality in rainfall, with positive trends in winter rainfall over the 1961-1995 period (Jones and Conway, 1997;Osborn et al, 2000), which have been particularly pronounced in Northern and western areas. These changes are generally attributed to enhanced westerly airflows in winter months, associated with positive phases of the North Atlantic oscillation (NAO).…”

Section: Runoffmentioning

confidence: 86%

An assessment of trends in UK runoff and low flows using a network of undisturbed catchments

2006

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In many parts of the world attempts to discern climatic-driven changes in river flow patterns are hindered by the combined impact of other, more direct anthropogenic disturbances such as abstraction and impoundments. This study capitalises on a newly defined 'benchmark' network of natural catchments in the UK to discern natural variability in flow regimes. Trend tests were applied to time series of runoff and indicators of low-flow magnitude and duration for two study periods to assess the sensitivity of trends to the frame of reference over which tests were conducted. Notwithstanding the volatility of the recent past, the results demonstrate a general stability in runoff and low flows since the early 1960s. The strongest signal to emerge from the study is a positive runoff trend for catchments in Scotland, which was resilient to the effect of the study periods. There was also some indication of increasing runoff in maritime western areas of England and Wales. These increases in maritime areas are likely to reflect the dominance of westerly airflows in the recent past, associated with an increase in the North Atlantic Oscillation (NAO) Index. For low flows, there were no compelling trends -significant positive trends over the 1973-2002 period are influenced by a sequence of notably dry years at the start of the period and were not observed over a 40-year time-frame. There are some indications of a tendency towards decreasing low flows in some eastern catchments, but this is supported by few significant results. The results of this study provide a baseline against which to assess longer-term change from historical flow time series and to monitor future change in the benchmark network.

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“…As a consequence, a significant fraction of local variability can be explained by more predictable large-scale oscillation patterns. This also applies to temperature, in spite of its great time and space variability, as shown by some workers who evaluated the correlation of temperature with indices describing some well-known planetary-scale oscillations, like the NAO and ENSO (Hurrell, 1995;Kutiel et al, 1996;Mayes, 1996;Valero et al, 1996).…”

Section: Relationship Between Wintertime Temperature and Atmospheric mentioning

confidence: 98%

Wintertime surface temperature in Egypt in relation to the associated atmospheric circulation

Hasanean

2004

Intl Journal of Climatology

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Mean wintertime temperatures (December, January, February) recorded during the period 1905-2000 at 18 weather stations distributed across Egypt were analysed to reveal spatial and temporal patterns of long-term trends. The relationship between winter atmospheric circulation indices and winter temperature in Egypt is examined using correlation analysis. The atmospheric circulation is represented by four indices: the well-known El Niño-southern oscillation (ENSO), North Atlantic oscillation (NAO) index, East Atlantic-West Russia (EAWR) index, and East Atlantic (EA) index.Surface temperature is a stable climatic element whose coefficient of variation (COV) is lower during winter. A statistically significant relation between COV and latitude indicates that stations in the south, Upper Egypt, are more variable than stations in the north, Lower Egypt. Increasing and decreasing winter surface temperature trends were found. In general, wintertime temperature has increased (warming) at most stations. Decreasing trends (cooling) are observed mainly over Upper Egypt. The upward trends in mean winter temperature during the 1910s-30s, mid 1970s, and early 1980s-2000 and the downward trends during the 1940s and 1960s are prominent features of the temporal distributions. The warming period that occurred early in the century may be explained by changes in circulation. Striking upward trends are most remarkable during the last 20 years. This could be attributed not only to human activities, but also to atmospheric circulation changes. No detectable connection between Egypt temperature and either ENSO or EA index was found during winter. A statistically significant negative relationship between winter temperature and winter NAO index can be observed. The NAO index is more dominant in determining winter temperature than ENSO circulation. A significantly stronger negative relationship between temperature over Egypt and the winter EAWR index values is detected.

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Spatial and Temporal Fluctuations of Monthly Raidfall in the British Isles and Variations in the Mid‐latitude Westerly Circulation

Cited by 47 publications

References 24 publications

Precipitation and the North Atlantic Oscillation: a study of climatic variability in northern England

Precipitation and the North Atlantic Oscillation: a study of climatic variability in northern England

An assessment of trends in UK runoff and low flows using a network of undisturbed catchments

Wintertime surface temperature in Egypt in relation to the associated atmospheric circulation

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