Appearance of night-shining clouds has increased

First spotted in 1885, silvery blue clouds sometimes hover in the night sky near the poles, appearing to give off their own glowing light. Known as noctilucent clouds, this phenomenon began to be sighted at lower and lower latitudes -- between the 40th and 50th parallel -- during the 20th century, causing scientists to wonder if the region these clouds inhabit had indeed changed -- information that would tie in with understanding the weather and climate of all Earth.

A NASA mission called Aeronomy of Ice in the Mesosphere, or AIM, was launched in 2007 to observe noctilucent clouds, but it currently only has a view of the clouds near the poles. Now scientists have gathered information from several other missions, past and present, and combined it with computer simulations to systematically show that the presence of these bright shining clouds have indeed increased in areas between 40 and 50 degrees north latitude, a region which covers the northern third of the United Sates and the lowest parts of Canada. The research was published online in the Journal of Geophysical Research: Atmospheres on March 18, 2014.

"Noctilucent clouds occur at altitudes of 50 miles above the surface -- so high that they can reflect light from the sun back down to Earth," said James Russell, an atmospheric and planetary scientist at Hampton University in Hampton, Va., and first author on the paper. "AIM and other research has shown that in order for the clouds to form, three things are needed: very cold temperatures, water vapor and meteoric dust. The meteoric dust provides sites that the water vapor can cling to until the cold temperatures cause water ice to form."

To study long-term changes in noctilucent clouds, Russell and his colleagues used historical temperature and water vapor records and a validated model to translate this data into information on the presence of the clouds. They used temperature data from 2002 to 2011 from NASA's Thermosphere Ionosphere Mesosphere Energetics and Dynamics, or TIMED, mission and water vapor data from NASA's Aura mission from 2005 to 2011. They used a model previously developed by Mark Hervig, a co-author on the paper at GATS, Inc., in Driggs, Idaho.

The team tested the model by comparing its output to observations from the Osiris instrument on the Swedish Odin satellite, which launched in 2001, and the SHIMMER instrument on the U.S. Department of Defense STPSat-1 mission, both of which observed low level noctilucent clouds over various time periods during their flights. The output correlated extremely well to the actual observations, giving the team confidence in their model.

The model showed that the occurrence of noctilucent clouds had indeed increased from 2002 to 2011. These changes correlate to a decrease in temperature at the peak height where noctilucent clouds exist in the atmosphere. Temperatures at this height do not match temperatures at lower levels -- indeed, the coldest place in the atmosphere is at this height during summertime over the poles -- but a change there certainly does raise questions about change in the overall climate system.

Russell and his team will research further to determine if the noctilucent cloud frequency increase and accompanying temperature decrease over the 10 years could be due to a reduction in the sun's energy and heat, which naturally occurred as the solar output went from solar maximum in 2002 to solar minimum in 2009.

"As the sun goes to solar minimum, the solar heating of the atmosphere decreases, and a cooling trend would be expected," said Russell.

NASA's Goddard Space Flight Center in Greenbelt, Md. manages the TIMED mission for the agency's Science Mission Directorate at NASA Headquarters in Washington. The spacecraft was built by the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

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First measurement flight: Research aircraft HALO explores trade wind clouds

Which climate effects do clouds have? Under what conditions do they warm or cool the atmosphere? Today, after more than five years of preparation, the specially equipped research aircraft HALO (High Altitude and Long Range Research Aircraft) takes off for its first measurement flight in atmospheric research. Prof. Bjorn Stevens and Dr. Lutz Hirsch from the Max Planck Institute for Meteorology (MPI-M) leave Oberpfaffenhofen in Germany for a ten-hour flight to Barbados.

They will operate numerous measuring instruments on board HALO on behalf of the German atmospheric research: "A day we have eagerly awaited," says Stevens. "It is the first major mission to exploit the novel capabilities of HALO to measure vertical profiles of all components of atmospheric water -- like vapor, liquid and ice, in both cloud and precipitation forms, as well as the aerosol particles upon which cloud droplets form -- from a high altitude. A new era of airborne atmospheric research." The aircraft, equipped with a large amount of advanced technology, is an initiative by German climate and environmental research institutions (see below) and is operated by the German Aerospace Center (DLR).

The flight is part of the NARVAL project (Next-generation Aircraft Remote-Sensing for Validation Studies) and will provide the scientists with more detailed information on the constitution of tropical clouds (Fig. 1). The transatlantic flights from Oberpfaffenhofen to Barbados will complement the stationary measurements of the cloud observatory on Barbados. The collected data will contribute to a better understanding of cloud and precipitation processes and will help to reduce uncertainties in climate models.

Remote sensing instruments, located in the "Belly Pod" underneath the aircraft?s hull, will detect vertical profiles of temperature and humidity and the distribution of droplets and aerosols (Fig. 2). Additionally, so-called dropsondes will be released during the flight. These radiosondes usually ascend from Earth with the help of a weather balloon and perform measurements on their way through the atmosphere. This time, they will be dropped by parachute and will glide back to the ground.

The first measurement flight is a joint project of the MPI-M with the Meteorological Institute of the University Hamburg, DLR, Universities of Cologne, Leipzig and Heidelberg and the Forschungszentrum J?lich. It will take the scientists on a long-haul flight to Barbados, where the MPI-M cloud observatory is located, and back. Ideally, comparison measurements with the satellite CloudSat will be performed during the flights. The satellite measures the Atlantic clouds in trajectories crosswise to the flight route. Short flights of HALO in parallel with these satellite trajectories make it possible to verify the satellite?s measurements (Fig. 3): the aircraft flies at a lower altitude than the satellite and can therefore detect the clouds much more accurate.

In total, the air route Oberpfaffenhofen -- Barbados and back should be flown three times in December 2013 ("NARVAL South"). During the second flight, a local flight from Barbados eastward through the trade wind clouds is planned. The aim is to detect clouds that are directly heading for the Barbados cloud observatory and to compare them to the land-based cloud observatory data.

The second part of the mission will be carried out under the direction of the University Hamburg in January ("NARVAL North"). HALO will be based on Iceland to examine the backsides of fronts over the North Atlantic. The amount of precipitation on the backsides of fronts is a controversial topic in science because satellite observations and model calculations provide different results. "Measured values are missing?? because ships do not sail in these typical storm zones" says principal investigator Prof. Felix Ament from the Center for Earth System Research and Sustainability (CEN), University of Hamburg. "A successful HALO mission could provide important facts and eliminate a 'blank spot' on the map of science."

The research aircraft HALO is an initiative by German climate and environmental research institutions. HALO is funded by: Federal Ministry of Education and Research (BMBF), German Research Foundation (DFG), Helmholtz Association, Max Planck Society, Leibniz Association, Free State of Bavaria, Karlsruhe Institute of Technology (KIT), GFZ German Research Centre for Geosciences, Forschungszentrum J?lich and German Aerospace Center (DLR)

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A Few Clouds and 79 F at Miami International Airport, FL

]]>Winds are East at 3.5 MPH (3 KT). The pressure is 1016.1 mb and the humidity is 82%. Last Updated on May 20 2011, 5:53 am EDT.

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A Few Clouds and 90 F at Miami International Airport, FL

]]>Winds are East at 10.4 MPH (9 KT). The pressure is 1016.0 mb and the humidity is 44%.The heat index is 92. Last Updated on May 19 2011, 1:53 pm EDT.

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