North Atlantic air pressure and temperature conditions associated with heavy rainfall in Great Britain

Abstract

Severe flooding in the United Kingdom is often linked to the occurrence of heavy rainfall events, which can be characterized by the synoptic scale meteorological conditions over the North Atlantic region. Seasonal heavy rainfall events (summer and winter 1-day maxima) were extracted from 125 locations across Great Britain over the period 1950-2017. For each event, anomaly sealevel pressure and 2 m air temperature conditions across the North Atlantic sector were extracted. In contrast to earlier studies, these two datasets were combined and clustered to identify how the pressure and temperature conditions co-vary within each half-year to produce heavy rainfall events. Distinctly different spatial patterns were found for four classes in summer and for three classes in winter. For all classes there is a negative sea-level pressure anomaly centred over or near the British Isles. However, whereas in summer the low pressures are associated with either predominantly cold or warm anomalies over most of the North Atlantic, in winter two phases of a smaller-scale fourpole temperature pattern emerges. Nevertheless, for one of the winter classes the cold anomaly over the northwest Atlantic is so deep, persistent and widespread that, unusually for the winter season, a significant relationship between the class's frequency of occurrence and the Atlantic Multidecadal Oscillation (AMO) index is found (r = −.39). Further, for both seasons heavy rainfall occurs when the AMO and the North Atlantic Oscillation (NAO) are in opposing phases. Particularly, positive NAO and negative AMO result in heavy rainfall in western Britain. Two classes in each season are consistent with positive and negative phases of the NAO, and the two non-NAO summer classes are associated with a northward extension of the subtropical high pressure and heavy rainfall in the southeast. The association between heavy rainfall and large-scale circulation and temperature drivers can find application in, for example, weather generators.

Abrupt drought termination in the British–Irish Isles driven by high atmospheric vapour transport

“…Positive NAO conditions were found to promote the development of ARs that draw atmospheric moisture from subtropical sources under a south-westerly airflow (Stohl et al 2008). It is perhaps no surprise that abrupt DTs are more prevalent under positive NAO conditions, which generally bring more winter storms, higher IVT, increased rainfall and higher temperatures across the BII and Northern Europe (Li et al 2020, Barnes et al 2022. Even within the UK there are spatio-temporal variations in the influence of NAO on rainfall and river flows, with positive NAO found to be more important primarily in the north-west and in winter (West et al 2021).…”

Using multi criteria decision analysis in a geographical information system framework to assess drought risk

“…Future rainfall, maximum temperature, minimum temperature and evapotranspiration ( Fig. 7 ) maps values were then standardized, so seasons could be more readily compared, by subtracting the monthly mean and subsequently dividing by the standard deviation ( Barnes et al., 2022 ).…”

“…Near Future Period 2021–2050. Rainfall maps were has been standardized so seasons could be more readily compared, by subtracting the monthly mean and subsequently dividing by the standard deviation a methodology used by Barnes et al. (2022) .…”

Estimating agricultural ammonia volatilization over Europe using satellite observations and simulation data

“…Ammonia loss to transport is the highest in regions neighboring the Atlantic Ocean, accounting for 30 %, 27 %, 32 %, and 34 % of total sinks in regions A, D, E, and G respectively. These regions are exposed to the North Atlantic Drift, also known as the Gulf Stream, that is associated with high wind speed and cyclonic activity (Barnes et al, 2022). In other regions, 14 % to 22 % of the total ammonia is lost to transport mechanisms, and in all regions, 11 to 22 % is lost to dry deposition (Figure 3).…”