Coastal winds and low‐level jets: Simulations for sea gulfs

Abstract

The reasons for the relatively strong coastal afternoon surface winds observed along the Gulf of Finland were studied by using a high‐resolution two‐dimensional numerical model in typical summertime conditions. Sea breeze effects were included by defining a clear sky, whereas they were minimized by alternatively defining a thick cloud cover. The geostrophic wind was varied both in speed and direction. A case‐study was made with a three‐dimensional operational forecast model with results that agreed with the two‐dimensional experiments and observations. Strongish afternoon surface winds nearly parallel with the coastline were obtained in the overcast gulf experiments. In these cases, well‐mixed air entering the smooth sea slantwise from over land commenced an inertial oscillation downstream such that the emerging low‐level jet maximum was located just above the opposite coast, causing the strong winds there. If the sky was clear, sea breezes and strong convective mixing further enhanced the coastal surface winds to supergeostrophic speeds. In contrast, weak coastal winds occurred when the sea breeze and the basic flow were nearly opposite. Given the gulf geometry, the sea breeze cell from the opposite coast could be advected over the gulf in a suitable basic flow, which resulted in another minimum in the coastal wind speed as a function of geostrophic wind direction. Copyright © 2005 Royal Meteorological Society.

Radiative and turbulent heating rates in the clear‐air boundary layer

“…In the UH mesoscale model this turbulence scheme has produced results in agreement with observations of basic variables and turbulent fluxes (from aircraft and towers) in many different environments, including: the tropical Pacific and Africa (Savijärvi 1997;Savijärvi and Matthews 2004); Midwest USA (Savijärvi 1991); northwest China (Savijärvi and Jin 2001); over boreal forests (Savijärvi and Amnell 2001); coastal zones (Savijärvi 2004;Savijärvi et al 2005); sea ice (Vihma and Brümmer 2002); even the Mars Viking and Pathfinder landing sites (Savijärvi and Siili 1993;Savijärvi et al 2004).…”

Cold air outbreaks over high-latitude sea gulfs

“…When the sea gulf was colder than the air, as during spring and early summer, anti-heat island circulation features were evident, while later in the summer with the sea slightly warmer than the air, heat island circulations did not quite show up. The sea breeze aspects were addressed by Savija¨rvi et al (2005) and Gahmberg et al (2010), and the small-scale local wind features near the coastlines by Savija¨rvi (2004). The present article now completes this series of studies for the mesoscale and local winds around the coasts of a highlatitude sea gulf by considering cases where the sea is a lot (20Á30 K) warmer than the air.…”

“…The model has been applied previously in many studies of sea/land breeze and sea ice edge winds with realistic results (e.g. Savija¨rvi and Matthews, 2004;Vihma et al, 2005;Savija¨rvi et al, 2005;Gahmberg et al, 2010;Savija¨rvi, 2011a,b); these references and the references therein provide further details of the model. The environment for the present wintertime simulations is the same as in the summertime simulations of Savija¨rvi (2011a): the 2-D model is set across an idealised 80 km wide eastÁwest sea ('Gulf of Finland') at 608N in a horizontal grid of 132 points 2 km apart.…”

The easternmost tropical Pacific. Part II: Seasonal and intraseasonal modes of atmospheric variability

“…Among them, it is cited, the dynamics of the CLLJ on various time scales (Amador, 1998;Wang et al, 2006;Amador, 2008), the WHWP variability (Wang et al, 2006), the interaction of the SST with synoptic scale systems (Salinas, 2006;Méndez, & Magaña, 2010;Serra, Kiladis, & Hodges, 2010), the ITCZ-CLLJ interaction (Hidalgo, Durán-Quesada, Amador, & Alfaro, 2015), ENSO-CLLJ interactions (Amador, 2008), and other global scale signals (Savijarvi, Niemela, & Tisler, 2005;Amador, Alfaro, Lizano, & Magaña, 2006).…”