Wednesday 18 May 2022

Fireball meteor over southwest England.

Witnesses across much of southern, central and northwest England, as well as the Chanel Islands and parts of Wales, France, Belgium and the Netherlands, have reported observing a bright fireball slightly before 9.45 pm local time (slightly before 8.45 pm GMT) on Monday 16 May 2022. The fireball is described as having moved from southeast to northwest first appearing over Southampton and vanishing over to the east of Bristol. A fireball is defined as a meteor (shooting star) brighter than the planet Venus. These are typically caused by pieces of rock burning up in the atmosphere, but can be the result of man-made space-junk burning up on re-entry.

 
A bright fireball meteor on 16 May 2022, observed from Slough in Berkshire. Shamalia Siddiqi/Twitter/BBC.
 
Objects of this size probably enter the Earth's atmosphere several times a year, though unless they do so over populated areas they are unlikely to be noticed. They are officially described as fireballs if they produce a light brighter than the planet Venus. The brightness of a meteor is caused by friction with the Earth's atmosphere, which is typically far greater than that caused by simple falling, due to the initial trajectory of the object. Such objects typically eventually explode in an airburst called by the friction, causing them to vanish as an luminous object. However, this is not the end of the story as such explosions result in the production of a number of smaller objects, which fall to the ground under the influence of gravity (which does not cause the luminescence associated with friction-induced heating).
 
 
Heat map showing areas where sightings of the meteor were reported (warmer colours indicate more sightings), and the apparent path of the object (blue arrow). American Meteor Society.

These 'dark objects' do not continue along the path of the original bolide, but neither do they fall directly to the ground, but rather follow a course determined by the atmospheric currents (winds) through which the objects pass. Scientists are able to calculate potential trajectories for hypothetical dark objects derived from meteors using data from weather monitoring services.

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Tuesday 17 May 2022

Three dead and several missing following landslide in Assam State, India.

Three people have died and several more are missing following a landslide in Assam State, India, on Saturday 14 May 2022. The incident happened in the evening when part of a hillslope in Dimo Hasao District collapsed following several days of heavy rain in the area associated with the Indian Monsoon Season. Landslides are a common problem after severe weather events, as excess pore water pressure can overcome cohesion in soil and sediments, allowing them to flow like liquids. Approximately 90% of all landslides are caused by heavy rainfall.

 
A landslide in Dimo Hasao District, Assam, which killed at least three people on Saturday 14 May 2022. Press Trust of India.

The incident comes amid widespread flooding in Assam, which has displaced thousands of people in five districts, and at least eighty homes destroyed in 10 villages. Numerous roads and rail lines have been swept away, severely hampering travel within the state. Monsoon Season typically lasts from May to October each year in Assam, and frequently brings with it flooding and related events. However, this year many areas of the state also had unusual pre-monsoonal rains through much of April, which led to the ground already being waterlogged by the time the monsoon arrived, and therefore a much more rapid onset of flooding problems.

 
Diagrammatic representation of wind and rainfall patterns in a tropical monsoon climate. Geosciences/University of Arizona.

Monsoons are tropical sea breezes triggered by heating of the land during the warmer part of the year (summer). Both the land and sea are warmed by the Sun, but the land has a lower ability to absorb heat, radiating it back so that the air above landmasses becomes significantly warmer than that over the sea, causing the air above the land to rise and drawing in water from over the sea; since this has also been warmed it carries a high evaporated water content, and brings with it heavy rainfall. In the tropical dry season the situation is reversed, as the air over the land cools more rapidly with the seasons, leading to warmer air over the sea, and thus breezes moving from the shore to the sea (where air is rising more rapidly) and a drying of the climate. This situation is particularly intense in South Asia, due to the presence of the Himalayas. High mountain ranges tend to force winds hitting them upwards, which amplifies the South Asian Summer Monsoon, with higher winds leading to more upward air movement, thus drawing in further air from the sea.

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Sunday 8 May 2022

One dead and thousands need hospital treatment as dust storms sweep across Iraq.

One person has died and about 5000 more have needed hospital treatment as a series of dust storms swept across Iraq last week. The majority of cases were from Baghdad, Anbar, and Najaf provinces, with the elderly and people with existing respiratory problems, such as asthma, being particularly vulnerable. Most patients were sent home after receiving oxygen treatment, although more serious cases were retained for further treatment. At the worst times flights within the country were cancelled.

 
A dust storm enveloping Baghdad on Sunday 1 May 2022. Ahmad Al-Rubaye/AFP/Getty Images.

Iraq is prone to dust storms, particularly during the summer months, when a long dry season is combined with prevailing winds blowing down from the mountainous northwest of the country towards the Persian Gulf. These are driven by high pressures over the Black Sea, and eastern Mediterranean, but typically lose their moisture on the western sides of the mountains, bringing water to western Turkey, but warm, dry air to Iraq and Arabia.

 
A patient receives treatment for dust inhalation in a hospital in Baghdad. Reuters.

While this is an expected problem, the dust storms have been getting much more severe in recent years, due to a combination of rising temperatures and lower rainfall. Temperatures in the country now exceed 50°C regularly in the summer months, and the coutry has received 50% less rainfall this year than last year. Predictions based upon current global warming models suggest that the Tigris and Euphrates rivers, which provide most of the country's water, could run dry in the summer months within 20 years, potentially making parts of the country uninhabitable.

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Crocodile killed following death of child in Siaya County, Kenya.

A Crocodile has been killed after a fatal attack on a child in Siaya County, Kenya, on Saturday 7 April 2022. The Animal is reported to have snatched a three-year-old boy and mauled him to death while his helpless mother looked on. in the East Asembo area, where the family has gone to collect water from Lake Victoria. The same Crocodile, described as over five metres in length, was later killed by local fishermen who caught the Animal by offering it meat attached to a hook and rope, before dragging it from the water and attacking it with pangas and axes. 

 
Crocodile killed by localfishermen in East Asembo, Kenya, on Saturday 7 May 2022. Isaiah Gwengi/The Standard.

The Kenya Wildlife Service has warned against villagers taking such matters into their own hands, asking that instead such attacks are reported so that the problem can be addressed by proffesionals who may be able to relocate problem Animals. Nile Crocodiles, Crocodylus niloticus, are considered to be of Least Concern under the terms of the  International Union for the Conservation of Nature’s Red List of  Threatened Species, but are still protected in many countries, due to historic hunting which decimated populations in many areas. The number of attacks on Humans by Crocodiles and Hippopotemus on the Kenyan shores of Lake Victoria have risen sharply in recent years, something which is thought to be driven by a rising Human population encroaching on areas where the Animals live. In August 2020 a 32-year-old woman was killed by a Crocodile while collecting water from the same beach.

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Asteroid 2022 JK passes the Earth.

Asteroid 2022 JK passed by the Earth at velocity of 22.15 km per second and a distance of about 411 400 km (1.01 times the average distance between the Earth and the Moon, or 0.28% of the distance between the Earth and the Sun), slightly before 1.45 am GMT on Tuesday 3 May 2022. There was no danger of the asteroid hitting us, though were it to do so it would not have presented a significant threat. 2022 JK has an estimated equivalent diameter of 9-27 m (i.e. it is estimated that a spherical object with the same volume would be 9-27 m in diameter), and an object of this size would be expected to explode in an airburst (an explosion caused by superheating from friction with the Earth's atmosphere, which is greater than that caused by simply falling, due to the orbital momentum of the asteroid) between 35 and 20 km above the ground, with only fragmentary material reaching the Earth's surface.

 
The relative positions of 2022 JK and the Earth on at 2.00 am on 3 May 2022. JPL Small Body Database.

2022 JK was discovered on 3 May 2022 (the day of its closest encounter with the Earth) by the University of Tokyo's Kiso Observatory.  The designation 2022 JK implies that the asteroid was the tenth object (asteroid K - in numbering asteroids the letters A-Z, excluding I, are assigned numbers from 1 to 25, with a number added to the end each time the alphabet is ended, so that A = 1, A1 = 26, A2 = 51, etc., which means that K = 10) discovered in the first half of May 2022 (period 2022 J - the year being split into 24 half-months represented by the letters A-Y, with I being excluded).

 
The orbit and current position of 2022 JK. The Sky Live 3D Solar System Simulator.

2022 JK is calculated to have a 1494 day (4.09 year) orbital period, with an elliptical orbit tilted at an angle of 0.82° to the plain of the Solar System which takes in to 0.59 AU from the Sun (59% of the distance at which the Earth orbits the Sun, and inside the orbit of the planet Venus) and out to 4.53 AU (4.53 times the distance at which the Earth orbits the Sun, and more than three times the distance at which the planet Mars orbits). It is therefore classed as an Apollo Group Asteroid (an asteroid that is on average further from the Sun than the Earth, but which does get closer). This means that 2022 JK has occasional close encounters with the Earth, with the last thought to have happened in November 1976. The asteroid also has occasional close encounters with the planet Jupiter, with the last thought to have happened in December 1961 and the next predicted for March 2033.

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