An atmospheric science – a high flying career

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Dr Andrew Kaye

https://www.isis.stfc.ac.uk/Pages/Dr-Andrew-Kaye.aspx#

As an atmospheric scientist Dr Kaye was lucky enough to spend nearly 10 year of his career as a Civilian Flight Test Observer with the Royal Air Force, managing access to the Met. Office C-130 flying laboratory. His experiments ranged from Cloud Physics through Atmospheric Chemistry to remote sensing.

Dr Kaye was born in the UK but he did not grow up there. He attended schools in Chicago and Sudbury Ontario in Northern Canada where his father was a university professor. His father’s job as a scientist was the reason why he had lived in three countries by the time he was ten.

His science background is very varied. He completed his degree in physics and geography at York University in Toronto and remained there to complete a PhD in experimental space science.

https://www.yorku.ca/

https://en.wikipedia.org/wiki/York_University

Dr Kaye’s PhD research was part of a planetary atmospheres group. He worked on the Earth’s atmosphere, but he had colleagues who were working on Voyager data from Saturn and other planetary atmospheric data. He was lucky to share an office with one of the first Canadian astronauts.

https://voyager.jpl.nasa.gov/mission/science/saturn/

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Three Voyager 2 images, taken through ultraviolet, violet and green filters, were combined to make this photograph.

When he had completed his PhD Dr Kye started a postdoc at the United Kingdom Atomic Energy Authority looking at aerosol releases from coastal nuclear reactors into the atmosphere.

https://en.wikipedia.org/wiki/United_Kingdom_Atomic_Energy_Authority

The United Kingdom Atomic Energy Authority is a UK government research organisation responsible for the development of nuclear fusion power.

In 1991 Dr Kaye saw an advert in New Scientist, with a photograph of the Hercules aircraft, wanting somebody to act as a scientific liaison and work for the natural environment, research council.

https://en.wikipedia.org/wiki/Natural_Environment_Research_Council

https://en.wikipedia.org/wiki/Lockheed_C-130_Hercules

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The Lockheed C-130 Hercules is an American four-engine turboprop military transport aircraft designed and built originally by Lockheed (now Lockheed Martin). Capable of using unprepared runways for takeoffs and landings, the C-130 was originally designed as a troop, medevac, and cargo transport aircraft.

Dr Kaye joined NERC in 1992 and it’s the work that he did on that aircraft that was the focus of his talk.

Dr Kaye managed a remote sensing facility within NERC moving on to responsive mode services, which provided all kinds of scientific services to the research community.

Towards the end of his time with NERC he managed the atmospheric polar science and e-science portfolios managing the science budgets.

Dr Kaye then joined the Science and technology research council as business manager for the science program.

https://en.wikipedia.org/wiki/Science_and_Technology_Facilities_Council

The Science and Technology Facilities Council (STFC) is a United Kingdom government agency that carries out research in science and engineering, and funds UK research in areas including particle physics, nuclear physics, space science and astronomy (both ground-based and space-based).

Since 2010 Dr Kaye has been managing the ISIS and CLF scientific visitor Program.

https://www.isis.stfc.ac.uk/Pages/home.aspx

https://en.wikipedia.org/wiki/ISIS_Neutron_and_Muon_Source

The ISIS Neutron and Muon Source is a pulsed neutron and muon source, established 1984 at the Rutherford Appleton Laboratory of the Science and Technology Facilities Council, on the Harwell Science and Innovation Campus in Oxfordshire, United Kingdom. It uses the techniques of muon spectroscopy and neutron scattering to probe the structure and dynamics of condensed matter on a microscopic scale ranging from the subatomic to the macromolecular.

https://www.clf.stfc.ac.uk/Pages/home.aspx

https://en.wikipedia.org/wiki/Central_Laser_Facility

Central Laser Facility (CLF) is a research facility in the UK. It is part of the Rutherford Appleton Laboratory. The facility is dedicated to studying the applications of high energy lasers. It was opened in 1976. As of 2013 there are 5 active laser laboratories at the CLF: Vulcan, Astra Gemini, Artemis, ULTRA, and OCTOPUS. The facility provides both high-power and high-sensitivity lasers for study across broad fields of science from atomic and plasma physics to medical diagnostics, biochemistry and environmental science. Also through the Centre for Advanced Laser Technology and Application (CALTA), CLF is responsible for laser development. DiPOLE is the brainchild of that project.

Dr Kaye’s job involves helping researchers from all over the world, who come to the Rutherford Appleton laboratory to use the scientific facilities.

https://stfc.ukri.org/about-us/where-we-work/rutherford-appleton-laboratory/

https://en.wikipedia.org/wiki/Rutherford_Appleton_Laboratory

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The Rutherford Appleton Laboratory (RAL) is one of the national scientific research laboratories in the UK operated by the Science and Technology Facilities Council (STFC). It began as the Rutherford High Energy Laboratory, merged with the Atlas Computer Laboratory in 1975 to create the Rutherford Lab; then in 1979 with the Appleton Laboratory to form the current laboratory.

Atmospheric Physics

One of the things Dr Kaye loves about atmospheric science is that you can see it in action all around you every day. His specialty is cloud physics and condensation nuclei that form cloud droplets.

https://en.wikipedia.org/wiki/Cloud_condensation_nuclei

Cloud condensation nuclei or CCNs (also known as cloud seeds) are small particles typically 0.2 µm, or 1/100 the size of a cloud droplet on which water vapour condenses. Water requires a non-gaseous surface to make the transition from a vapour to a liquid; this process is called condensation. In the atmosphere, this surface presents itself as tiny solid or liquid particles called CCNs. When no CCNs are present, water vapour can be supercooled at about −13 °C for 5–6 hours before droplets spontaneously form.

One cold morning, when taking his son to school, Dr Kaye noticed exhaust plumes coming from the chimneys of a power station and identified several thermal inversions.

https://en.wikipedia.org/wiki/Inversion_(meteorology)

In meteorology, an inversion, also known as a temperature inversion, is a deviation from the normal change of an atmospheric property with altitude. It almost always refers to an inversion of the thermal lapse rate. Normally, air temperature decreases with an increase in altitude. During an inversion, warmer air is held above cooler air; the normal temperature profile with altitude is inverted.

An inversion traps air pollution, such as smog, close to the ground. An inversion can also suppress convection by acting as a “cap”. If this cap is broken for any of several reasons, convection of any moisture present can then erupt into violent thunderstorms. Temperature inversion can notoriously result in freezing rain in cold climates.

https://www.naturphilosophie.co.uk/temperature-inversions-city-pollution-defunct-jet-engines/

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http://essentialpilot.co.za/2019/07/13/how-temperature-inversions-affect-flying-conditions/

Dr Kaye noticed that the different thermal inversions were reaching different levels depending on which chimney they were escaping from.

The plumes that reached the greatest height in the atmosphere were warmer and had more water vapour in them. Dr Kaye was able to photograph the plumes and obtained a tephigram for the day.

http://www.met.reading.ac.uk/~sgs02rpa/TEACHING/Tephigram.pdf

The Tephigram is one of a number of thermodynamic diagrams designed to aid in the interpretation of the temperature and humidity structure of the atmosphere and used widely throughout the world meteorological community. It has the property that equal areas on the diagram represent equal amounts of energy; this enables the calculation of a wide range of atmospheric processes to be carried out graphically.

A blank tephigram is shown below; there are five principal quantities indicated by constant value lines: pressure, temperature, potential temperature (θ), saturation mixing ratio, and equivalent potential temperature (θe) for saturated air.

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https://en.wikipedia.org/wiki/Tephigram

The name evolved from the original name “T-ø -gram” to describe the axes of temperature (T) and entropy ø used to create the plot. Usually, temperature and dew point data from radiosondes are plotted on these diagrams to allow calculations of convective stability or convective available potential energy (CAPE). Wind barbs are often plotted at the side of a tephigram to indicate the winds at different heights.

https://en.wikipedia.org/wiki/Radiosonde

A radiosonde is a battery-powered telemetry instrument carried into the atmosphere usually by a weather balloon that measures various atmospheric parameters and transmits them by radio to a ground receiver.

In simple terms the tephigram is a plot of temperature energy in the atmosphere.

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The above image shows Dr Kaye’s tephigram. He has highlighted two lines by colouring one red and one blue. The blue line is the temperature of the air and it is rising up.

Warm air rises and as it does so it cools, but in this case the air isn’t cooling as much as expected. It isn’t rising.

When warm air is allowed to rise it rapidly becomes cooler, more dense than its surroundings and sink back down.

https://thehomeschoolscientist.com/convection-current-experiment/

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The red line on Dr Kaye’s tephigram is called the dewpoint and is effectively a measure of relative humidity. When the dew point gets to the actual temperature that’s the level at which cloud will form. At this point it will start to release thermal energy from the water condensing and then rise as a cloud.

The tephigram shows two thermal inversions. The first one is where the dewpoint hits the temperature and then there’s a second one quite a bit higher up.

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The above image shows that Dr Kaye’s photograph and the tephigram matched. He knew the height of the chimney so he was able to estimate the height of the inversions.

The tephigram had been taken by a radiosonde in Cornwall on the morning of February, the 12th 1999 when the picture was taken.

The picture shows one of the cooling towers plume rising to a different level to the other one. This shows the two plumes had different energies. One thermal inversion was due to one plume and the other thermal inversion was due to a second. The higher plume was the result of a gas fired power generator. The lower one was the result of a coal/oil power plant (which no longer exists)

https://en.wikipedia.org/wiki/Didcot_power_stations

Didcot power station (Didcot B Power Station) is an active natural gas power plant that supplies the National Grid. A combined coal and oil power plant, Didcot A, was the first station on the site which opened in 1970 and was demolished between 2014 and 2020.

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Didcot Power Station, including the former Didcot A.

Dr Kaye developed a great interest in flying as he grew up. His favourite aircraft was known as Snoopy XV-208, which was a converted Hercules aircraft that the Met office ran with the Royal Air Force as a flying laboratory.

https://www.metoffice.gov.uk/

https://en.wikipedia.org/wiki/Met_Office

The Meteorological Office, abbreviated as the Met Office is the United Kingdom’s national weather service.

https://cockpitrevolution.ecwid.com/Lockheed-C130-hercules-W2-Snoopy-XV208-p126262891

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https://www.raf.mod.uk/

https://en.wikipedia.org/wiki/Royal_Air_Force

The Royal Air Force (RAF) is the United Kingdom’s aerial warfare force. It was formed towards the end of the First World War on 1 April 1918, becoming the first independent air force in the world, by regrouping the Royal Flying Corps (RFC) and the Royal Naval Air Service (RNAS).

Snoopy was Dr Kaye’s primary aircraft but he did manage two other aircraft for NERC at various times. One was a Piper chieftain named G-NERC (below left), which was a remote sensing aircraft followed by a German aircraft, D-CALM (below right).

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D-CALM was a much more capable remote sensing aircraft.

Dr Kaye managed the crew, the facility and the data processing as part of his job, He was actually a civilian flight test observer.

The team had to keep log books, with all of their training and flights and Dr Kaye has a record of every flight he has made. It’s 21 years since he made his last flight on the Hercules and he clocked up over 700 hours of Hercules time.

As a flight test observer Dr Kaye’s job was to be aircraft scientist and he was in command of the science part of the flight,

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The image above is Dr Kaye’s computer screen. Part of his job was to make sure that the aircraft was in the right place to deliver the science that the other scientists on board were going to work on.

For a flight Dr Kaye would have produced a flight plan. During the flight he would have to listen to the flight crew plus the scientific crew, which could include 19 people running instruments, measuring things, discussing things and running computer equipment. He could also end up listening to air traffic control in case they wanted the plane to return.

The Hercules could descend to 50 feet, which would take it below any little micro inversions near the surface overland. In some cases, it could go as low as 100 feet but generally you can’t go below 1000 feet in built up areas because people get upset when planes get close to their roofs.

By changing the flight different things could be measured. Descending or climbing at a fixed rate could produce a profile of the atmosphere. This would throw up areas of interest where the plane could then fly level to investigate further.

Work included calibrating and validating satellite interpretations of the surface, by removing or correcting for the atmosphere. A satellite, orbiting the Earth would enable the atmosphere to be profiled at a great height, whilst the plane would produce a profile at a low height. This gave the scientists detailed information about the atmosphere that they were looking through to see from the ground or the sea surface.

One of Dr Kaye’s flight missions involved studying gyres in the Mediterranean, where the water circulates near the Straits of Gibraltar. This was done in conjunction with the Royal research ship Discovery

https://noc.ac.uk/facilities/ships/rrs-discovery

https://en.wikipedia.org/wiki/RRS_Discovery_(1962)

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RRS Discovery was a British Royal Research Ship operated by NERC.

https://en.wikipedia.org/wiki/Ocean_gyre

In oceanography, a gyre is any large system of circulating ocean currents, particularly those involved with large wind movements. Gyres are caused by the Coriolis effect; planetary vorticity, horizontal friction and vertical friction determine the circulatory patterns from the wind stress curl (torque).

Gyre can refer to any type of vortex in an atmosphere or a sea, even one that is man-made, but it is most commonly used in terrestrial oceanography to refer to the major ocean systems.

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https://en.wikipedia.org/wiki/North_Atlantic_Gyre

The gyre has a pronounced thermohaline circulation, bringing salty water west from the Mediterranean Sea and then north to form the North Atlantic Deep Water.

https://en.wikipedia.org/wiki/Strait_of_Gibraltar

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The Strait of Gibraltar, also known as the Straits of Gibraltar, is a narrow strait that connects the Atlantic Ocean to the Mediterranean Sea and separates the Iberian Peninsula in Europe from Morocco in Africa.

The advantage of flying as well as sailing allowed the teams to produce profiles above the aircraft and map the sea surface temperature around the aircraft ship to give them a much bigger scale piece of work.

A lot of the work carried out by Dr Kaye was done in collaboration with other large scientific projects.

https://youtu.be/cWI8_IP3uRU

Dr Kaye showed a video of one of his operations.

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His job was to use a small computer and keyboard and in the above image you can see a tephigram, but he could use it to cycle through all of the different screens in the cabin. It meant that he could view something that one of his colleagues considered to be interesting.

Dr Kaye’s job also involved cloud observations during the flight.

Dr Kaye and his colleagues had to undergo training in case anything went wrong:

Flight medicals – someone could get taken ill on board;

https://www.skybrary.aero/index.php/Medical_Emergencies_-_Guidance_for_Flight_Crew

Dingy drills – there was always the risk that they might actually have to ditch the aircraft, in which case they would have to get into a dinghy and survive and do that.

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Dingy drills were carried out all year, rain and shine, summer or winter. In the above image is an object with a square hole in it. This represented a window of a plane and the trainees had to jump through it and inflate a dinghy, to rescue each other. Sometimes the drill took place at sea.

https://www.youtube.com/watch?v=sClyUv9Nw_o

https://www.mindef.gov.sg/web/portal/rsaf/news-and-publications/featured-stories/story-detail/2020/Aircrew_Water_Survival_Training

Smoke and fumes (in flight) drill – Basically firefighting drills and putting on oxygen masks. This might involve putting masks on colleagues and strapping them into their seats as the aircraft might have to be depressurized to allow doors to be opened to allow smoke out.

The RAF also have a part to play in rescuing

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Back to the science

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https://ncas.ac.uk/our-services/atmospheric-observations/facility-for-airborne-atmospheric-measurements/

http://arsf.nerc.ac.uk/index.asp?cookieConsent=A

In 2014, the management of the ARSF was transferred to the British Antarctic Survey. The ARSF has now been renamed the NERC Airborne Research Facility (NERC ARF), but retains its worldwide remit and suite of airborne remote sensing instrumentation

https://www.bas.ac.uk/polar-operations/sites-and-facilities/aircraft/mission-planning/

Dr Kaye did cloud physics work, satellite calibrations and boundary layer turbulence studies, which involved looking at how air mixes from the lower levels. Although, primarily, he was interested in the opposite kind of situations where there was a thermal inversion that capped the air

Dr Kaye also did atmospheric radiation studies, looking at solar light coming into the atmosphere and a lot of atmospheric chemistry studies. And then, of course, just regular weather system stuff.

Often during the flights Dr Kaye had people helping him and he was able to participate in experiments that other people were running.

The Pitot static head and gust probe along with some other instruments are on the nose well ahead of the air disturbed by the aircraft.

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https://en.wikipedia.org/wiki/Pitot-static_system

A pitot-static system is a system of pressure-sensitive instruments that is most often used in aviation to determine an aircraft’s airspeed, Mach number, altitude, and altitude trend. A pitot-static system generally consists of a pitot tube, a static port, and the pitot-static instruments. Other instruments that might be connected are air data computers, flight data recorders, altitude encoders, cabin pressurisation controllers, and various airspeed switches.

https://glossary.ametsoc.org/wiki/Gust_probe

An air velocity sensing instrument usually mounted on the front of an aircraft that resolves turbulent fluctuations in all three components relative to the aircraft.

Most of the equipment was in the wing pods on the outer ends of the wing or on the top or bottom of the aircraft.

Snoopy had a big advantage in that it could carry 12 hours’ worth of fuel. A lot of science could be done on a 12-hour flight, which means Dr kaye could fly almost to Iceland and back.

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With a strategic stopover Snoopy could operate between the UK and Africa (and anywhere in between).

Profiles could be taken 50 feet over the sea (or 100 feet on land) up to 30000 feet. An altimeter informs the pilots how far above the ground they are.

https://en.wikipedia.org/wiki/Altimeter

If the plane is to drop to 50 feet there is a list of things that need to be done to ensure that the plane can rise again. One of these is to actually pull the circuit breakers on the landing gear, so you don’t suddenly have the landing gear coming down and causing drag and other problems for the pilot.

At 50 feet white caps can be seen on the water. Whitecaps are the sea foam crest over the waves.

https://en.wikipedia.org/wiki/Sea_foam

Sea foam, ocean foam, beach foam, or spume is a type of foam created by the agitation of seawater, particularly when it contains higher concentrations of dissolved organic matter (including proteins, lignins, and lipids) derived from sources such as the offshore breakdown of algal blooms.

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The above image was taken about 1500 to 2000 miles from the coast of England, so Snoopy was well out in the Atlantic

Most of the cargo hold contained equipment and part of Dr Kaye’s job was to make sure that the researchers from the different universities built their equipment to the right standards and got it approved so that it could be on the aircraft.

The hold was not exactly spacious and it was very noisy (85dB of continuous sound).

Instruments were placed on tables with springs. The displacement of the cabin floor was a millimetre at a 60 hertz migration frequency on the prop line. It was very tiring to work in that space because of all the shaking.

https://www.southernwings.co.nz/aircraft-propeller-basics/

One of Dr Kaye’s jobs was to plan the flights and to set it up with the aircrews. One of his trips was from Santa Maria and this particular one was called the tropical Arc manoeuvre where he flew out from Santa Maria and then did a zigzag. Up and down from a certain height down to the surface, to build a picture of a curtain of air coming into the island

https://en.wikipedia.org/wiki/Santa_Maria_Island

Santa Maria is an island in the eastern group of the Azores archipelago (south of the island of São Miguel) and the southernmost island in the Azores. The island is known for its white sand beaches, distinctive chimneys, and dry warm weather.

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Some of the flight plans were quite complicated,

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The above image shows profiling up and down. pick some areas and come back and then do two “curtains” across at a high and low level.

One trip involved flying over Caithness.

https://en.wikipedia.org/wiki/Caithness

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Caithness is a historic county, registration county and lieutenancy area of Scotland.

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The aim of this trip was to measure the methane emissions from the bogland in the summer, where the methane boils off the bog.

The above image shows the aircraft track of the flight when the team flew the plane on various levels from high to low. The reason it zigzags at the bottom is because there’s a ridge of hills and the plane had to fly in the valleys for safety.

To keep safe, the plane would fly through the valley and then descend to the right altitude. Go to the north turn round come back through the valley and then turn around again and what the team were doing on this experiment was filling large bags with samples of air and GPS marking the time and the position where the bag was filled. This enabled them to go back and build up a picture of the emissions.

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The above image shows that on this day there was a thermal inversion that capped the air and the wind is blowing across Caithness. Downwind the concentration is pretty constant at 1850 parts per million billion of methane. But upwind the value has elevated to about 1950 hundred parts per billion more of methane.

The team could look at the different levels and see how much gas was coming off. This gave them an average emission flux over 50 kilometres of the Caithness/Sutherland, which is 270 micro moles of methane per metre squared per hour. The scientists could measure exactly what was coming off the bog at a certain spot by using a metre square sampling tube but what they couldn’t do was to scale it up which is what the team could do with the aircraft.

The experiment was scaled up. Two more flights took place, one of which was around Britain (see image below). There was a capped inversion and tedlar bags were used to sample the air throughout the journey.

https://www.techinstro.com/tedlar-bag/

Tedlar bags are designed to collect gas and air samples.

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The data from the flight described above were looking at the emissions of carbon dioxide, nitrous oxide and nitric oxide from the United Kingdom. At this time the Kyoto Protocol for global climate change was being negotiated.

https://en.wikipedia.org/wiki/Kyoto_Protocol

The Kyoto Protocol is an international treaty which extends the 1992 United Nations Framework Convention on Climate Change (UNFCCC) that commits state parties to reduce greenhouse gas emissions, based on the scientific consensus that (part one) global warming is occurring and (part two) that human-made CO2 emissions are driving it. The Kyoto Protocol was adopted in Kyoto, Japan, on 11 December 1997 and entered into force on 16 February 2005. There are currently 192 parties (Canada withdrew from the protocol, effective December 2012) to the Protocol.

The results from this flight were so important that the initial results were faxed to the government minister in Kyoto during the negotiations. Because the team didn’t want to have numbers coming out in a publication that would be different from the numbers the minister had seen and cause any potential embarrassment to the government on its negotiating position.

Dr Kaye regards this as a high point in his involvement with the science because the information gleaned helped develop policy on climate change.

When international experiments were carried out aircraft were used on different sides of the ocean to collect data. One major international program lasted a couple of years, and at one point, two aircraft had to be flown wingtip to wingtip at several different levels. This was to make sure that all of the instruments were measuring comparable things.

This was an absolute test to make sure that the ozone monitor in one aircraft was measuring the same concentrations of ozone as the other. Different instruments were measuring different chemicals and different radiated fluxes correctly.

During the procedure both planes were in contact with each other talking about the different instruments and making sure that each knew what each other’s instruments were doing in broad terms. This was to be sure that the data collected could later be written up as a proper into comparison between the two aircraft. This was a US and European project.

Another project involved the D-CALM plane which was bristling with atmospheric chemistry equipment, but again, it had to fly wingtip to wingtip with another plane for a while.

In 1999 there was a solar eclipse and Dr Kaye got funding to take Snoopy out into the solar eclipse track, which the image below shows

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Solar eclipse track from six degrees West out to about 20 degrees West.

https://en.wikipedia.org/wiki/Solar_eclipse

A solar eclipse occurs when a portion of the Earth is engulfed in a shadow cast by the Moon which fully or partially blocks sunlight. This occurs when the Sun, Moon and Earth are aligned. Such alignment coincides with a new moon indicating the Moon is closest to the ecliptic plane. In a total eclipse, the disk of the Sun is fully obscured by the Moon.

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Normally during sunrise and sunset the sun’s rays get take a long time to be filtered out and disappear because they are travelling through a long path in the atmosphere.

But during a solar eclipse because the moon cuts off the Sun’s light and you get a very dramatic reduction in solar flux and then a restart.

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The image above shows JO1D and JNO2, and these are the two wavelengths of sunlight that split oxygen atoms to create ozone creating the ozone layer. Another wavelength splits nitrogen dioxide into nitrous oxide.

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The image above shows the results from equipment onboard that measured the quantity of nitrous oxide. The concentration dropped off dramatically at the time of the totality of the eclipse and then came back again with some oscillations but it fits nicely to the photo flux, as measured by the aircraft instruments.

Because the plane was at several thousand feet above, the team could see that the sea surface got dark below them because there was no sunlight coming down on us. But they could actually get sunlight coming from the side so they didn’t notice it getting dark.

Questions and answers

1) Did you ever have to use the dinghy?

No, we were fortunate. It’s one of those things you prepare for the worst and hope you never have to do it so it’s really a case of just making sure everyone in the crew knew what to do.

The closest we ever got to an in-flight emergency was when we were flying over East Anglia and one of the flight deck windows cracked. The pilots pulled us into a descent and the flight engineer pulled the pressurization. Our ears were going crazy because the aircraft is losing pressure, but within about two minutes we were down to 10,000 feet, which you can safely fly unpressurized.

2) What holds a cloud together?

There’s some really fun maths you can do, but basically when you an aerosol into the air clouds can form.

https://en.wikipedia.org/wiki/Aerosol

An aerosol (abbreviation of “aero-solution”) is a suspension of fine solid particles or liquid droplets in air or another gas.

https://earthobservatory.nasa.gov/features/Aerosols/page4.php

Most clouds owe their existence to aerosols that serve as the tiny “seeds,” called cloud condensation nuclei.

The charges of the various particles keep them together. A positively charged particle will attract a negatively charged particle.

So, clouds do tend to stay together rather than break apart because of the attraction between the droplets as they grow but they are not solid because aircraft can fly through them.

The droplets in the cloud are all slightly different sizes and because of that, although the air is rising, the droplets are slowly falling at different rates. They’re falling within the air they are in. The droplets are going up with the air but falling downwards.

The smaller droplets rise faster than the bigger ones but they are also falling within the air. Eventually the bigger droplets bump into the little ones below them and then they coalesce and become bigger cloud droplets.

Eventually, the droplets become big enough to become raindrops and fall out of the cloud. They can also freeze and then the ice crystals travel at different speeds to the droplets but what gets really interesting is that when they start bumping off of one another and rising at different speeds they actually collect different electrical charges.

So, when they bang together, you get differential charges building in the cloud, and of course that’s how you get lightning and effects like that within cloud.

https://en.wikipedia.org/wiki/Lightning

Lightning is a naturally occurring electrostatic discharge during which two electrically charged regions in the atmosphere or ground temporarily equalize themselves, causing the instantaneous release of as much as one gigajoule of energy.

The three main kinds of lightning are distinguished by where they occur: either inside a single thundercloud, between two different clouds, or between a cloud and the ground.

3) Have you done any thunderstorm science and, if so, what was the experience like?

We didn’t specifically do thunderstorm work. We tried to avoid thunderclouds because they tended to be rather energetic. But I do remember once seeing a little bubble, and before we gone very much further it just rocketed up to 35,000 feet and became a thundercloud. The aircrew basically steered the plane around it. However, even in temperate cloud work that we did we kept the flight radar set to clouds and turbulence.

Very occasionally we’d be coming along and the the air crew saying warned that something didn’t look good and everyone braced. Then it would be like a roller coaster where you’d suddenly go through a sheer in the atmosphere and the aircraft would jump around a little bit, and it could get quite rough at times.

In fact, we used to always say you can tell who were the experienced people in the aircraft, because they took their airsickness tablets all the time, because there were days when the flights were really rough.

4) What was your most interesting flight?

Well, the craziest one was actually one we were doing an instrument test flight, where we had a new computer system on board, and if you ever bored enough to read the manual that comes with your computer, there’s actually the thing that tells you it’s only guaranteed up to 10,000 feet, or something air pressure wise because within a hard disk the heads ride on air to so they don’t bang into the recording material.

And, of course, in an aircraft you’re sometimes depressurized in the cabin at 10,000 feet. Vibrations can occur so you want to make sure that the computer system can read and write data properly. So, we were doing a test flight where we tested all the different things and I asked the flight leader, who ran the computer system, if there was anything else that needed to be checked. He said, we need some pitch and yaw to just do a final check on the computer, to see if it can cope.

https://en.wikipedia.org/wiki/Aircraft_principal_axes

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An aircraft in flight is free to rotate in three dimensions: yaw, nose left or right about an axis running up and down; pitch, nose up or down about an axis running from wing to wing; and roll, rotation about an axis running from nose to tail. The axes are alternatively designated as vertical, transverse, and longitudinal respectively. These axes move with the vehicle and rotate relative to the Earth along with the craft.

The process was rather uncomfortable and they travelled close to zero g. The plane climbing at full throttle from 10000 feet.

https://en.wikipedia.org/wiki/Weightlessness

They repeated the process did three or four times to test the computer drive’s ability to read and write data, to make sure it would all work.

5) Did you see any snow in the clouds?

We, did fly in icy conditions. A lot of people don’t realise this but cloud droplets are water. But in clouds water doesn’t freeze until minus 40 degrees Celsius. And that’s because for ice crystals to form you actually have to have a nucleus for the crystal to grow on.

In a cloud there’s certain types of nucleus. A particular kind of nucleus needs to be present nuclei for snowflakes to seed in the cloud.

But of course, you’ve got an aircraft bombing through the cloud and the wings’ surface and the nose of the aircraft are a solid surface that ice crystals can grow on.

So, you can be in a liquid phase cloud, which immediately starts building up ice on the aircraft surfaces. This situation can be very dangerous if it’s not controlled. There are de-icing and anti-icing systems and most aircraft actually have surfaces on the wing which they can heat up to stop the ice forming in the first place.

However, sometimes you actually get do get ice building up and you have to drop to a different level to melt the ice off the aircraft.

So, I’ve not seen snow in a cloud, but I’ve seen ice forming on the windscreen wipers on the outside of the cabin window on the flight deck.

6) During your career, have you observed much change in the chemistry of climate change?

Not, specifically in the chemistry, because of course we were measuring the things which they’re still measuring today. The numbers have changed but for me it’s much more obvious. Just seeing the changes around snow forming where I grew up in the winters now.

And the climate here in England, just in the change in the 30 years I’ve lived here. Being a scientist who’s studied climate change I’m aware of what those changes are likely to be and I can observe them in my garden.

7) How often did you see some cetaceans on the low level see flights?

Believe it or not, we actually did see a whale once. But it was very fleeting so we didn’t really get a good look at it. Unfortunately, because a lot of my work was low level over the sea, there was a significant number of bird strikes on the aircraft. A gannet broke a pressure seal at one point because we were flying at a low level over the sea which wasn’t a particularly pleasant thing.

8) Did you see a lot of birds?

We did see a lot of them and that was one of the problems as they tended to get in the way. In the 700 hours that I flew I only experienced three or four bird strikes. This wasn’t a huge number but the birds were a problem so we did have to try and avoid them.

9) When you are gathering the air in bags how did you avoid getting a bird in a bag?

Basically, the bag had a very small pipe as an opening so we probably wouldn’t have gotten a bird in there.

10) What was your most dangerous flight?

Descending to 50 feet is fraught with danger. However, considering health and safety rules the aircrew managed it very effectively so we were never in any real danger. Even though it seemed scary with the clouds bouncing around the aircraft was quite capable of surviving it and being flown safely.

There wasn’t danger per se. We were aware that the oxygen supply on board was liquid oxygen. The instruments required lots of high-pressure cylinders of gases to do the analysis with. We were working with scientific equipment which could be dangerous if they were not handled properly.

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