SOUSY Svalbard Radar for atmospheric research to study weather, winds, waves and turbulence

1. SOUSY Svalbard Radar for atmospheric research to study weather, winds, waves and turbulence in the polar region A contribution to understand Global Climate Change SOUSY-SMART Svalbard Middle Atmosphere Research and Technology

2. The studies of Sun-Earth relations comprise a multidisciplinary synergy of science and education. Such studies are performed on a global scale. The polar regions are of high relevance, since in the polar upper atmosphere phenomena from above, resulting from the effect of the solar wind on the Earth's atmosphere and ionosphere and phenomena from below, such as atmospheric waves propagating upwards from the lower atmosphere, are merging. The relative importance of these effects from above and below are studied continuously and extensively. • The polar summer mesosphere is extremely cold between 80 km and 90 km altitude, such that ice particles form, resulting in Noctilucent Clouds and in particular radar scattering, manifest in Polar Mesosphere Summer Echoes known as PMSE. The polar stratosphere (10-50 km) and troposphere (0-10 km) are strongly affected by dynamic processes occurring in connection with the polar vortex.The relation to weather changes and the ozone budget in polar regions is evident. • Mesosphere-stratosphere-troposphere (MST) radars have proved to contribute significantly to the studies of these processes. For this purpose the Max-Planck-Institut für Aeronomie had set up an MST VHF radar in Longyearbyen on Svalbard: the SOUSY Svalbard Radar (78°N, 16°E). It is obvious that such MST radar studies are carried out in combination with other related observations, i.e. with the EISCAT Svalbard Radar, and with several in-situ and ground-based experiments performed by several research groups to study the polar atmosphere, enhanced by introducing new technology (SOUSY-SMART).

3. The SOUSY Svalbard Radar (SOUSY) operates on 53.5 MHz with an average power up to 3 kW, a high-gain 356 Yagi-antenna array of 95 meters diameter (see left-side photo), allowing five beam pointing directions at and close to the zenith. In addition the system consists of digital radar control, a high sensitivity receiver and signal processing units. Raw data are stored on disk, tape and CD-ROM. Result data can also be displayed in real-time on-site and and on the internet, presently under: Radars am IAP, Svalbard, Aktuelle Messung, PMSE, Troposphäre at • <www.iap-kborn.de/messungen/index_d.htm> • Impressive echoes can frequently be ob- • served from altitudes 80-110 km, which • result of scatter from meteors.The above • panel shows a meteor echo lasting over • almost 10 seconds.These echoes provide • information on the orbit of the originating meteorite and the meteor shower. Atmospheric winds and temperatures are deduced from the meteor echo trail. • During summer months strong echoes occur from altitudes 80 km to 95 km, which are the co-called Polar Mesosphere Summer Echoes (PMSE). The lower panel shows a 12-hour sequence of the echo power, the vertical air velocity and turbulence intensity observed with the SSR over Longyearbyen on 13 June 1999. These PMSE are sensible tracers of atmospheric waves. A se-quence of these, covering a period of one hour, is shown in the upper right-hand panel.The vertical velocity amplitudes can be as large as ±5 m/s. • The long-term observations of these PMSE over Svalbard can be used as an indicator of global change of temperature and water vapor at these altitudes.

4. The SOUSY-SMART Radar is a proper instrument for studies of these PMSE. The combination with the EISCAT Svalbard Radar provides a unique and novel tool for investigating the complex scatter processes from the dusty plasma in the very high latitude summer mesopause region. The suitable combination with other instruments, such as optical observations by spectrometers and lidars etc., together with educational facilities, such as UNIS, makes Longyearbyen a globally outstanding focal point for middle and upper atmosphere science. In addition, the SSR is an appropriate instrument for investigations of the meteorology of the lower stratosphere and troposphere. It is the first radar of this kind at the high polar latitudes of 78 degrees North. • The SOUSY Svalbard Radar SMART can continuously measure the horizontal and vertical wind in the lower atmosphere up to about 15 km height with a resolution of 150 meters. The radar reflectivity, related to the radar echo power, provides most valuable information on the height and structure of the tropopause and weather fronts. Examples of such data, collected over a period of four days, are presented in the figure, where the upper panel shows the vertical velocity and the lower panel the radar reflectivity. The variation of the tropopause (green band in the middle of the lower panel) are indicators of regions of troposphere-stratosphere exchange, which have an effect on the ozone budget in the Arctic. • Such profiles can be obtained with a best time resolution of 30 seconds. They are highly useful for detection of clear-air turbulence (large vertical velocity variations up to 1-2 m/s (red/green) observed in the beginning and the middle of the shown period), which would be useful for air traffic warning, and can be applied for improved weather forecasting (winds and rain/snow in Longyearbyen) by real-time analyzing variations of frontal structures aloft by operating the SOUSY Svalbard Radar in the wind profiler mode. • SOUSY stands for SOUnding SYstem - a system of instruments to remotely sound the atmosphere from the ground. The SOUSY Svalbard Radar has now been taken ove by the University in Tromsø and should be upgraded with new technology: SOUSY Svalbard Middle Atosphere Research and Technology (SMART). This will widen the scientific community and increase the research results, which are highly useful for better understanding of the Earth’s atmosphere and space environment, and for studies of global climate change. • @ jr, Max-Planck-Institut für Aeronomie, 37191 Katlenburg-Lindau, Germany, February 2002. • The SOUSY Svalbard Radar SMART is now operated by the Tromsø Geophysical Observatory, • University of Tromsø, Norway, October 2003.