Influence of the North Atlantic Subtropical High on wet and dry sea-breeze events in North Carolina, United States

Abstract

The sea-breeze (SB) is an important source of summertime precipitation in North Carolina (NC, southeast United States). However, not all SB events produce precipitation. A climatology of wet and dry SB events in NC is used to investigate the conditions that are conducive to precipitation associated with the sea breeze.Radar imagery was used to detect 88 SB events that occurred along the NC coast between MaySeptember of 2009-2012. The majority (85%) of SB events occurred during offshore flow (53%) or during flow that was parallel to the coast (22%). SB events were separated into dry (53%) and wet (47%) events and differences in the dynamic and thermodynamic parameters of the environment in which they formed were analyzed. Significant differences in dynamic and thermodynamic conditions were found. SB dry events occurred under stronger winds (6.00 ± 2.36 ms -1 ) than SB wet events (4.02 ± 2.16 ms -1 ). Moreover, during SB wet events larger values of convective available potential energy and lower values of convective inhibition were present, conditions that favor precipitation. Overall, the SB wet events accounted for 20-30% of the May-September precipitation along the NC coastal region. The position of the North Atlantic Subtropical High (NASH) controls both moisture availability and winds along the NC coast, thus providing a synoptic-scale control mechanism for SB precipitation. In particular, it was shown that when the NASH western ridge is located along the southeast coast of the United States, it causes a moist southwesterly flow along the NC coast that may favor the occurrence of SB wet events.Keywords: Sea breeze; precipitation; North Carolina; North Atlantic Subtropical High; wind direction; wind speed. Luchetti, N.T., Nieto Ferreira, R. Rickenbach, T.M., Nissenbaum, M.R. and McAuliffe J.D.Investigaciones Geográficas, nº 68, pp. 09 -25. ResumenLa brisa marina (BM) es una importante fuente de precipitación de verano en Carolina del Norte (NC en su sigla en inglés), sudeste de Estados Unidos. Sin embargo, no todos los eventos de BM producen precipitación. En este trabajo se utiliza una climatología de eventos de BM lluviosos y secos en NC para investigar las condiciones que conducen a la precipitación.Se utilizaron imágenes de radar para detectar 88 eventos de BM ocurridos a lo largo de la costa NC entre mayo y septiembre de 2009 a 2012. La mayoría (85%) de los eventos de BM ocurrieron durante períodos de viento hacia el mar (53%) o viento paralelo a la costa (22%). Los eventos BM se separaron en eventos secos (53%) y lluviosos (47%) y se analizaron las diferencias en los parámetros dinámicos y termodinámicos del entorno en el que se formaron. Se encontraron diferencias significativas en las condiciones dinámicas y termodinámicas. Eventos de BM secos ocurrieron bajo vientos más fuertes (6,00 ± 2,36 ms-1) que los eventos de BM lluviosos (4,02 ± 2,16 ms-1). Las BM lluviosas ocurrieron bajo valores de energía potencial convectiva disponible más altos y valores del parámetro de inhibición convectiva más ...

Effects of the North Atlantic Subtropical High on summertime precipitation organization in the southeast United States

“…On daily timescales, Luchetti et al . (2017) found that the NASH western ridge helps control moisture availability and winds along the North Carolina coast, thus providing a synoptic‐scale control mechanism for sea breeze precipitation. In particular, they showed that when the NASH western ridge is located along the southeast coast of the United States, its associated moist southwesterly flow along the North Carolina coast favours the occurrence of precipitation along the sea breeze front.…”

Means and Long-Term Trends of Global Coastal Zone Precipitation

“…In response to this, studies suggest that the highs in the Northern Hemisphere 29 and Southern Hemisphere 30 subtropical oceans are becoming more intense and expanding landward, leading to a greater moisture flux into the CZ. Sea-breeze circulations (SBC) are also dependent on the land-ocean thermal contrast, and the added moisture and energy would be conducive to the generation of mesoscale precipitation fronts that can penetrate further into the interior 31 . Furthermore, if the interior has higher elevations oriented along the coastline, this would result in a greater frequency of orographically enhanced rainfall, boosting the upward trend 11,13 .…”