{"id":11089,"date":"2020-02-27T07:26:57","date_gmt":"2020-02-27T12:26:57","guid":{"rendered":"https:\/\/blogs.sw.siemens.com\/simcenter\/?p=11089"},"modified":"2026-03-26T06:01:10","modified_gmt":"2026-03-26T10:01:10","slug":"mountains-arent-just-funny-theyre-hill-areas-foehn-effect","status":"publish","type":"post","link":"https:\/\/blogs.sw.siemens.com\/simcenter\/mountains-arent-just-funny-theyre-hill-areas-foehn-effect\/","title":{"rendered":"Mountains aren\u2019t just funny, they\u2019re hill areas! – Foehn Effect"},"content":{"rendered":"\n

With the ski season\nfully underway, I thought this would be a good time to turn our attention to\nmountains, specifically the effects of weather in the Alps and what causes the warming\nand drying of air. This is something that skiers, snowboarders and residents of\nmountainous regions should be familiar with. <\/p>\n\n\n\n

What I am talking\nabout is the Foehn (F\u00f6hn) effect, which regularly impacts weather conditions,\nnot just locally but often for hundreds of kilometres downwind. Simply, this is\na change from wet and cold conditions on one side of a mountain to warmer and\ndrier conditions on the other (leeward) side. This effect can often lead to\nmassive temperature differences with the greatest being on the 14th<\/sup>\nJanuary 1972 in Montana, USA. Within 24 hours the temperature changed from -48\u00b0C\nto 9\u00b0C, this is a temperature increase of 57\u00b0C!<\/p>\n\n\n\n

While we don\u2019t see\nextremes like this in the UK, the Foehn effect is most prevalent across the\nScottish highlands where the high ground along the west coast results in wet\nweather. In contrast to this the lower ground across the east of Scotland\nenjoys warmer weather with more sunshine.<\/p>\n\n\n\n

How does the Foehn effect work?<\/strong><\/h2>\n\n\n\n

When air encounters a mountain it is forced upwards, as the pressure decreases with altitude this causes the air to expand and cool. As the colder air is less able to hold water vapour, the water condenses and forms clouds. These then release the water as rain or snow above the mountain. <\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

This can enable us to\ndraw two initial observations, firstly snow is only usually at the top of\nmountains and heavier on one side. Additionally you have probably observed a\ncloudless sky on a summer\u2019s day with only a few clouds forming around mountain\npeaks. These are both due to the pressure and temperature drop which result in\ncloud formation.<\/p>\n\n\n\n

As the clouds form and then precipitate the fluid is changing from a vapour to a liquid state, this results in an irreversible heating effect due to the removal of moisture from the air. The flow of drier air passes over the mountain peak and down the leeward side which results in warm dry air. This is a great example of atmospheric thermodynamics and which can now be demonstrated in Simcenter\u2122 Flomaster\u2122.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

The image above shows the wet air on the left (windward side) that is forced up the mountain, this causes it to cool and then condense to form clouds. This then causes it to rain which results in moisture being lost and a gain in heat. This warmer air descends on the leeward side and promotes evaporation. This image only tells half the story though as we can\u2019t see the humidity change.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

At the exit of the clouds the specific humidity is set to 100% on outflow.\u00a0 This means that any super-saturation is lost (as rain).\u00a0 The specific humidity reduces but relative humidity is 100%.\u00a0 Now the air has no liquid water to condense, so the heat effect is nearly 10\u00b0C \u2013 leading to winds of 18\u00b0C.<\/p>\n\n\n\n

Why is this important?<\/strong><\/h2>\n\n\n\n

The Foehn effect can\nlead to a number of positive effects, mainly regions that experience this\nheating effect have drier climates which result in longer growing seasons. It\ndoes however have a number of negatives too. If we look back to skiing the\nwarmth from the Foehn effect is good for tourism but it increases the risk of\navalanches, it can also cause glacial melt and flooding along with contributing\nto the loss of ice shelves in Polar Regions. <\/p>\n\n\n\n

It also poses risks to\nclimbers and can be a major contributing factor to the spread of wildfires. The\ncombination of warm, dry air and high wind speeds promote the ignition and\nrapid spread of wildfires.<\/p>\n\n\n\n

There are also claims\nof Foehnkrankenheit (Foehn sickness) among people in alpine regions which\nrecent studies have suggested that there might be some truth in this as they\nhave shown correlations with migraine occurrences.<\/p>\n\n\n\n

This shows why complex physical phenomenon are very important to be able to understand fully and model accurately. We here at Siemens strive to understand these effects so that you can quickly model solutions with the highest levels of confidence and accuracy in the results.<\/p>\n","protected":false},"excerpt":{"rendered":"

With the ski season fully underway, I thought this would be a good time to turn our attention to mountains, specifically the effects of weather in the Alps and what causes the warming and drying of air. This is something that skiers, snowboarders and residents of mountainous regions should be familiar with. <\/p>\n","protected":false},"author":2295,"featured_media":11094,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"spanish_translation":"","french_translation":"","german_translation":"","italian_translation":"","polish_translation":"","japanese_translation":"","chinese_translation":"","footnotes":""},"categories":[179,182],"tags":[16],"industry":[150,171],"product":[502],"coauthors":[],"class_list":["post-11089","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-product-updates","category-tips-tricks","tag-system-simulation","industry-energy-utilities","industry-software-development","product-simcenter-flomaster"],"featured_image_url":"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/6\/2020\/02\/Waterfall-like-clouds-880466656-scaled.jpg","_links":{"self":[{"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/posts\/11089","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/users\/2295"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/comments?post=11089"}],"version-history":[{"count":2,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/posts\/11089\/revisions"}],"predecessor-version":[{"id":11095,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/posts\/11089\/revisions\/11095"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/media\/11094"}],"wp:attachment":[{"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/media?parent=11089"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/categories?post=11089"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/tags?post=11089"},{"taxonomy":"industry","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/industry?post=11089"},{"taxonomy":"product","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/product?post=11089"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/simcenter\/wp-json\/wp\/v2\/coauthors?post=11089"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}