Morning Glory cloud

A Morning Glory cloud formation between Burketown and Normanton, Australia.

The location of the Gulf of Carpentaria.

Satellite photo of morning cloud formations over the Gulf of Carpentaria. Northern part of the visible linear cloud is North Australian Squall Line, Morning Glory cloud is the very southern part of this linear cloud.

The Morning Glory cloud is a rare meteorological phenomenon occasionally observed in different locations around the world. The southern part of Northern Australia's Gulf of Carpentaria is the only known location where it can be predicted and observed on a more or less regular basis. The settlement of Burketown attracts glider pilots intent on riding this phenomenon. (see Burketown, Queensland#Climate)

Description

Morning Glory clouds can most often be observed in Burketown in September to mid-November, when the chance to see it early in the morning is approximately 40%.^[1]

A Morning Glory cloud is a roll cloud that can be up to 1,000 kilometres (620 mi) long, 1 to 2 kilometres (0.62 to 1.2 mi) high, often only 100 to 200 metres (330 to 660 ft) above the ground and can move at speeds up to 60 kilometres (37 mi) per hour. Sometimes there is only one cloud, sometimes there are up to eight consecutive roll clouds.

The Morning Glory is often accompanied by sudden wind squalls, intense low-level wind shear, a rapid increase in the vertical displacement of air parcels, and a sharp pressure jump at the surface. In the front of the cloud, there is strong vertical motion that transports air up through the cloud and creates the rolling appearance, while the air in the middle and rear of the cloud becomes turbulent and sinks.

The cloud can also be described as a solitary wave or a soliton, which is a wave that has a single crest and moves without changing speed or shape.

History of exploration

Unusual cloud formations have been noticed here since ancient times. The local Garrawa Aboriginal people called it kangólgi^[1]. Royal Australian Air Force pilots first reported this phenomenon in 1942.

The Morning Glory cloud of the Gulf of Carpentaria has been studied by multiple teams of scientists since the early 1970s. The first studies were published by Reg H.Clarke (University of Melbourne)^[1]. Multiple studies have followed since then, proposing diverse mathematical models explaining the complex movements of air masses in region.

Causes

Despite being studied extensively, the Morning Glory cloud is not clearly understood.

Regardless of the complexity behind the nature of this atmospheric phenomenon, some conclusions have been made about its causes. Through research, one of the main causes of most Morning Glory occurrences is due to the mesoscale circulations associated with sea breezes that develop over the peninsula and the gulf. On the large scale, Morning Glories are usually associated with frontal systems crossing central Australia and high pressure in northern Australia. Locals have noted that the Morning Glory is likely to occur when the humidity in the area is high, which provides moisture for the cloud to form, and when strong sea breezes have blown the preceding day.

Scenario for formation

The following is a summary of the conditions that cause the Morning Glory cloud to form in the Gulf of Carpentaria (after hypothesis of R.H.Clarke, as described in 1981)^[1]. First, Cape York which is the peninsula that lies to the east of the gulf is large enough that sea breezes develop on both sides. The breeze from the Coral Sea coast blows in from the east and the breeze from the gulf blows in from the west. The two breezes meet in the middle of the peninsula, forcing the air to rise there and form a line of clouds over the spine of the peninsula. When night comes, the air cools and descends and at the same time a surface inversion forms over the gulf (where air temperature increases with height). The densities in this stable layer are different above and below the inversion. The air descending from the peninsula to the east goes underneath the inversion layer and this generates a series of waves or rolling cylinders which travel across the gulf. These cylinders of air roll along the underside of the inversion layer, so that the air rises at the front of the wave and sinks at the rear. In the early morning, the air is saturated enough so that the rising air in the front produces a cloud, which forms the leading edge of the cylinder, and evaporates in the back, hence forming the Morning Glory cloud. The cloud lasts until the surface inversion disappears with the heating of the day.

This is one scenario that explains the formation of the Morning Glory Cloud over the Gulf of Carpentaria, but other explanations have also been proposed.

There are other ways in which Morning Glory clouds form, especially in rarer cases in other parts of the world, but these are far less understood.

Local weather lore in the area suggests that when the fridges frost over and the café tables' corners curl upwards at the Burketown Pub, there is enough moisture in the air for the clouds to form. Reportedly, all winds cease at ground level as the cloud passes over.^[2]

One vantage point to see Australia's Morning Glory is from Burketown in the remote Far North Queensland around September and October.^{[citation needed]} Towns in this part of the world are small and a long way apart, and Burketown has an influx of glider and hang-glider pilots at this time of year.

Other reported occurrences

Although the Morning Glory clouds over the southern part of Carpentaria Gulf are the most frequent and only here they can be predicted at a certain time of year, similar phenomena occasionally have been observed in other areas of the world, e.g. over the Central United States, the English Channel, over Berlin, Germany, Eastern Russia, as well as other maritime regions of Australia.

Morning Glory type roll clouds have been reported to occasionally happen off the Mexican coast in the Sea of Cortez. The phenomenon has also been observed from Sable Island, a small Canadian island located 180 km southeast of Nova Scotia; a Morning Glory cloud also passed through Yarmouth, Nova Scotia in April 2009^[3]. In contrast to Australia’s Gulf of Carpentaria where the Morning Glory cloud is visible in the morning, the clouds experienced in Nova Scotia have all occurred during the evening. Rare examples have been observed via satellite observation over the Joseph Bonaparte Gulf in the Eastern Kimberley region of Australia as well as over the Arabian Sea. A Morning Glory cloud was observed in 2007 over the Campos dos Goytacazes bay in the state of Rio de Janeiro, Brazil^[4]. In August 2011, it happened again over Peregrino Field in South Campos Basin in Brazil^[5].

Notes

1. ^ ^{a b c d} "Morning Glory of Carpentaria Gulf". Wondermondo. http://www.wondermondo.com/Countries/Au/AU/Queensland/CarpentariaMornGlory.htm. 
2. ^ Gavin Pretor-Pinney (2006). The Cloudspotter's Guide. Hodder & Stoughton. ISBN 0-340-89589-6.  Chapter 13, The Morning Glory the cloud that glider pilots surf, pp 283-305
3. ^ http://www.cjls.com/news.php?ID=446
4. ^ http://blog.vils.com.br/2009/07/nuvem-morning-glory-na-bacia-de-campos.html
5. ^ http://www.youtube.com/watch?v=8q5IXqhnISc

External links

• Menhofer A, Smith RK, Reeder MJ, Christie DR (1997) “Morning-Glory” Disturbances and the Environment in which They Propagate. Journal of the Atmospheric Sciences: Vol. 54, No. 13 pp. 1712–1725
• Smith, Deborah. (2002) Morning Glory lures scientists to ride cloud nine The Sydney Morning Herald: September 16, 2002 -see - http://www.austms.org.au/Jobs/Library1.html
• http://www.meteo.physik.uni-muenchen.de/~roger/Tropics/Tropclds-o.htm regarding Tropical cloud lines
• morninggloryaustralia.com Meteorological information, photos and video of the Morning Glory Cloud.
• DropBears.com on the Morning Glory phenomenon, with aerial photos of the cloud.
• hang glider soaring hang gliding on the Morning Glory phenomenon, with aerial photos and videos of the cloud.
• ABC Australia with images of soaring the Morning Glory.
• Cloud Appreciation Society Article on the Morning Glory, images, and video.
• Sable Island Green Horse Society Sable Island Soliton in the afternoon of 13 June 2003 - The same formation as a classic Gulf Morning Glory Cloud
• Sable Island Green Horse Society More photos of the Sable Island Soliton
• Wired.com Wired Science blog post about the clouds.