THE STORM STUDIES IN THE ARCTIC (STAR) PROJECT

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1 THE STORM STUDIES IN THE ARCTIC (STAR) PROJECT John Hanesiak 1, Ronald Stewart 1, Kent Moore 2, Peter Taylor 3, Walter Strapp 4, Mengistu Wolde 5 (1) Centre for Earth Observation Science, University of Manitoba, Winnipeg, Canada (2) Dept of Physics, University of Toronto, Toronto, Canada (3) Dept. of Earth and Space Science, York University, Toronto, Canada (4) Cloud Physics and Severe Weather Division, Environment Canada, Toronto, Canada (5) Flight Research Laboratory, National Research Council of Canada, Ottawa, Canada 1. INTRODUCTION Storms and their related hazards over the Arctic can have profound effects including loss of life and impacts on all life forms, industry, transportation, hunting, recreation, as well as on the landscape (terrestrial, sea ice and ocean). Over the past few decades, there is some evidence that the occurrence of extreme storms have increased (Stone et al. 2000; McCabe et al. 2001; Zhang et al. 2004) and further changes, including over the Arctic, are expected with anticipated climate change. Storms and associated hazards are common in the Arctic and some of the most intense storms occur in the eastern Arctic. As lowpressure systems naturally progress from the west and south, they often intensify as they track east and north (e.g. Hudson et al. 2001; Hoskins and Hodges, 2002; Intihar and Stewart, 2005). The interaction of these lowpressure systems with local significant topography can result in high wind speed (gap flow) and precipitation events (e.g. Nawri and Stewart, 2006; Martin and Moore, 2005). The fall season is the stormiest when cold air from the north crosses relatively warm surfaces and warm air from southern latitudes, acquiring a great deal of energy, allowing extreme storms to form and evolve. The Storm Studies in the Arctic (STAR) project ( focuses on these hazardous Arctic storms over the southern Baffin Island region, primarily due to existing observational infrastructure and greater population density. Iqaluit, the capital of Nunavut and located on southern Baffin Island, is a thriving city with an increasing population and industrial, tourism and recreation developments. The overall objective of this 4-year ( ) STAR project is to better understand severe Arctic storms and their associated hazardous conditions, and contributing to their better prediction. The objective will be realized through a focus on four themes: 1. Hazardous weather-related conditions in the Iqaluit area 2. Regional hazardous weather-related conditions and sea ice impacts 3. Prediction capabilities and improvements 4. User community interactions More specifically, the main hazards being investigated are: 1. Blizzards, blowing snow, and reduced visibility 2. Storms producing snow and mixed phase precipitation with significant accumulation 3. Storms, strong winds and their impact on sea ice STAR will provide, through its major field project and post-analysis, a better understanding of the physical features of Arctic storms and their hazards, the processes controlling them, and our predictive capabilities for them. All of the enhanced detailed field measurements were made in the vicinity of Iqaluit, NU, although storms affecting other communities on southern Baffin Island and CloudSat validation were also of interest.

2 2. PROJECT AREA AND INSTRUMENTS 2.1 STAR Geography STAR is geographically focused on the southern Baffin Island region, Nunavut, Canada. The area around Frobisher Bay on Southern Baffin Island is dominated by two mountain ranges (Fig 1). Meta Incognita Peninsula is characterized by low mountain ranges with a typical elevation of the higher ridges of 600 m, with peaks to about 750 m within 50 km to the west-southwest of Iqaluit. On Hall Peninsula, to the north and north-west of Iqaluit, the mountains are generally higher, reaching about 1,000 m within 100 km of the city, with a maximum elevation of 1,295 m close to the southwest coast of Cumberland Sound. These mountains have a strong impact on the surface weather near coastal communities such as Iqaluit. The highest topography, elevations in excess of 2000 m, on southern Baffin Island is associated with the Penny Ice Cap on the Cumberland Peninsula north of Pangnirtung. Available operational meteorological data on Southern Baffin Island are hourly surface observations at the locations shown in Figure 1, and twelvehourly soundings at Iqaluit. Iqaluit is located at N, W. Fig 1: STAR geographic area. 2.2 STAR Instrumentation Arctic storms and severe weather were sampled using standard meteorological field measurements and remotely sensed observations. Field measurements were collected during two field campaigns in fall 2007 (Oct 10 Nov 30) and winter 2008 (Feb 1 29). The base for the surface observations was at the Environment Canada Weather Office in Iqaluit. Meteorological instruments were installed in the last week of September and remained operational throughout the fall field campaign. Certain instrumentation remained in the field for both the fall storms project and the winter blowing snow project. The National Research Council of Canada s (NRC) Convair-580 research aircraft was instrumented by Environment Canada and NRC to collect internal storm measurements of cloud microphysics, thermodynamics, wind and the 4-D dynamic and precipitation structures of storms within a 500 km radius of Iqaluit, Nov 5-30, The aircraft enabled STAR to probe storm events as they approached the area, during their passage and departure over the study area. The aircraft also provided the only sensor validation flights for CloudSAT overpasses in the Arctic. The aircraft was equipped with meteorological instruments that measured temperature, humidity, 3-D winds and gusts, cloud microphysics fields (i.e. liquid & total water probes, icing probes, cloud particle spectrometers, dropsondes, radiometers), Ka band upward/downward looking radar and an NRC dual wavelength (W and X-band) polarimetric up/down/sideways Doppler radar providing remotely sensed measurements of clouds and precipitation. The NRC aircraft flew approximately 48 hours during the project. This time was divided over 14 missions, with variable objectives. A total of 56 dropsondes were deployed from nine of the aircraft flights. Nine flights were performed during CloudSat overpasses. During storm and interesting weather events, the standard upper air releases were supplemented with additional radiosondes, released at three-hourly or six-hourly intervals in Iqaluit. From the period of Oct 10 Nov 30, 2007, a total of 51 special radiosondes were released. A portable rawinsonde unit was taken to the community of Pangnirtung to

conduct simultaneous launches with Iqaluit during selected severe weather events. A total of 18 radiosondes were released in Pangnirtung between the dates of Nov 2 18, 2007.

3 conduct simultaneous launches with Iqaluit during selected severe weather events. A total of 18 radiosondes were released in Pangnirtung between the dates of Nov 2 18, A potable X-band Doppler radar was deployed at the Environment Canada Weather Office in Iqaluit (Oct 10 - Nov 30, 2007) since no operational radars exist in northern Canada. This instrument was used in real-time to map precipitation and wind fields within a radius of approximately 50 km of Iqaluit. It will also be used to validate satellite (CloudSAT, ASTER, MERIS, and MODIS) and surface based precipitation measurements. A passive microwave radiometer (Radiometrics WVR- 1100) provided time-series measurements of column-integrated water vapor and liquid water content and an acoustic Doppler sodar (Remtech PA1-NT) was also used to assess the three component winds between km AGL. Both instruments operated between Oct 10 Nov 30, A small mesonet of 10 automatic weather stations, within a 100 km radius of Iqaluit where installed at the end of September (Fig 2). Nine of these stations measured 3 m wind velocity, pressure, 2 m temperature, and 2 m humidity every 10-minutes. The weather stations were positioned over various forms of topography to assess storm influences on surface weather. One of the ten stations was a standard 10-m tower installation in Iqaluit. This 10-m tower was equipped with similar instrumentation as the other mesonet stations, but also had anemometers sampling at 10 m, 4 m, 3 m, 2 m and 1 m and a visibility sensor. In addition to the ten southern Baffin Island weather station sites, an additional automatic weather station was setup in the community of Pangnirtung, Oct 13 Nov 18, Special instruments set up at the Iqaluit weather office site augmented the other instrumentation. This included (1) a double fence facility with a Genore snow measurement system, (2) Thies Clima laser precipitation sensor (precipitation type, size distribution), (3) high resolution digital microphotography camera for precipitation particles. Fig 2: STAR mesonet locations. Red markers indicate real-time iridium data access. 3. ATMOSPHERIC MODELING Besides the operational GEM (Global Environmental Multi-scale) 15 km horizontal resolution model operated by Environment Canada, STAR had real-time 2.5 km horizontal resolution GEM-LAM (GEM Limited Area Model) simulations available over the STAR domain once a day. The University of Toronto also made real-time MM5 forecast model products available online each day over a similar domain as GEM-LAM. Standard model output fields were provided over the limited domain as well as specialized cross sections through Iqaluit, along and perpendicular to the terrain, along Cumberland Sound and special cross sections where required for flight planning. The model initial fields and output has been archived and special model runs will be performed in the future for further analysis and experiments. 4. STORM CASES AND THEIR FEATURES Sixteen IOPs (Intensive Observation Periods) took place between Oct 10 Nov 30, Table 1 shows the start/end dates/times, number of special rawinsondes (not including regular operational), and aircraft flight and dropsonde status. Table 2 shows the types of phenomena that were sampled during the

4 course of the project. Note that multiple types of phenomena may have been sampled on any given IOP. It can be seen that a wide variety of weather/phenomena were observed, and two IOPs with multiple aircraft flights. Some example case studies are provided in this article. IOP Start (UTC) 1 15 Oct End (UTC) 17 Oct # YFB sondes 8 Aircraft Flight # Dropsondes Oct 21 Oct Oct 27 Oct Oct 30 Oct Nov 4 Nov 4 (2 in XYP) 6 5 Nov 6 Nov 7 (4 in yes XYP) 7 6 Nov 7 Nov 1 yes Nov 8 Nov 3 yes Nov 10 Nov 1 yes Nov 12 Nov 5 yes Nov 19 Nov 23 (12 at yes ( XYP) flights) Nov 20 Nov yes ( flights) Nov 22 Nov yes Nov 23 Nov yes Nov 28 Nov yes Nov 29 Nov 3 yes Table 1: IOP, rawinsonde, aircraft and dropsonde details. YFB = Iqaluit, XVP = Pangnirtung. Phenomena / Purpose Observations Low Pressure System 7 Trough 3 Precipitation in YFB 9 Precipitation in XYP 3 Strong Winds/BS 2 Upslope Precipitation 5 Convergence Zone 2 Convection over Ocean 1 Rain/Snow Boundary 1 CloudSat 8 Table 2: Weather phenomena and/or purpose of IOPs during STAR Six closed surface low pressure systems crossed southern Baffin Island with two of them being major systems (central surface pressures < 990 hpa). One of the major systems (IOP 11) had three flights devoted to it, with dropsondes in the first flight through the warm front that contained a rain/snow boundary in northern Quebec. A significant storm that was sampled solely by aircraft was the remnants of Hurricane Noel, the most severe hurricane in 2007 in terms of casualties. The storm tracked northward into Davis Strait between Nov 4-5, 2007 as a powerful high latitude system (central pressures estimated to be 960 hpa). The STAR team had its first flight on Nov 5 into this major storm system (IOP 6) (Fig 3), reaching into its northern edge, flying at low altitudes (< 300 m - 1km ASL) inbound and higher altitudes (5 km ASL) outbound, with multiple dropsondes, full radar coverage and cloud microphysical measurements. Minimum pressures and maximum wind speeds measured at 300 m ASL were 962 hpa and >100 km h -1, respectively. Fig 3: IOP 6 flight track on a MODIS satellite image. One low-level convection case was sampled via aircraft over Hudson Strait. This system produced unexpected accumulations of snow in Iqaluit between 1900 UTC Nov UTC Nov 10. One special rawinsonde was released in Iqaluit at 2100 UTC Nov 9 to sample the thermodynamic state of the atmosphere during the event as well as microphotography. Sample data from the aircraft Ka-band radar returns are shown in Fig 4, highlighting the structure of the convective towers that were flown through. Cloud tops were >3 km with significant

SBCAPE (350-400 J kg -1 ), based upon radar and dropsonde data. Moderate turbulence was observed.

analysis is required. Fig 5: One of the IOP 11 CloudSat passes (black curved line) overlain on an IR satellite image. Cloud top temperatures are color coded in C.

A sample CloudSat mission is depicted in Figs 5-7 that took place 1648-1651 UTC Nov 17 in the STAR region (IOP 11).

The CloudSat radar shows significant widespread precipitation along its track with interesting internal precipitation structures and radar returns as high as 10 km (Fig 6).

5 SBCAPE ( J kg -1 ), based upon radar and dropsonde data. Moderate turbulence was observed. It is hypothesized that the depth of the convection/instability along with moderate hpa westerly winds (60-70 km h -1 ) caused the unexpected snowfall in Iqaluit, however, more extensive analysis is required. Fig 5: One of the IOP 11 CloudSat passes (black curved line) overlain on an IR satellite image. Cloud top temperatures are color coded in C. Fig 4: Ka-band downward looking aircraft radar during IOP 9, showing convective tower structure. A sample CloudSat mission is depicted in Figs 5-7 that took place UTC Nov 17 in the STAR region (IOP 11). The CloudSat pass was coincident with a major storm system that affected a large area, with cloud top temperatures as cold as -60 C (Fig 5). The CloudSat radar shows significant widespread precipitation along its track with interesting internal precipitation structures and radar returns as high as 10 km (Fig 6). CloudSat ice effective radii reached up to 170 µm in the lower sections of the main precipitation region. A research aircraft flight took place between UTC Nov 17 directly along part the CloudSat track. Aircraft cloud microphysical and radar measurements will be used to validate CloudSat data on this mission as well as others for the first time in high latitudes. Fig 6: CloudSat radar reflectivity (dbz) from part of the track in Fig 5. The y-axis is in km, the x-axis represents horizontal distance along the satellite track. Fig 7: same as Fig 6 but for effective ice radius (µm). 5. CONCLUDING REMARKS The STAR field project is the first of its kind in the eastern Canadian Arctic, providing a unique dataset for better understanding severe Arctic storms, weather hazards and their processes. It is also the first and only high latitude CloudSat validation dataset in the world, thus far. The field phase was conducted between Oct 10 Nov 30, 2007 and Feb Sixteen IOPs were sampled, exhibiting a variety of weather situations and mesoscale phenomena over the region. The results of the project are expected to improve

6 our current understanding of Arctic weather and to contribute to its improved prediction. Although STAR occurred over a limited region of the Arctic, the location is typical of many physiographic features in other parts of the Arctic, and hence, the physical understandings that are gained during STAR, will be applicable to many locations in the Arctic. The STAR dataset will also be a legacy for future projects in the Arctic region, including future IPY projects. 6. REFERENCES Hoskins, B. J. and K. I. Hodges, 2002: New perspectives on the Northern Hemisphere winter storm tracks. Journal of the Atmospheric Sciences, 59, Hudson, E., D. Aihoshi, T. Gaines, G. Simard, and J. Mullock, 2001: Weather of Nunavut and the Arctic. NAV Canada, Ottawa, Ontario, 246 pp. Intihar, M.R. and R.E. Stewart, 2005: Extratropical cyclones and precipitation within the Canadian Archipelago during the cold season. Arctic, 58, no. 2, Martin, R. E. and G. W. K. Moore, 2006: Transition of a synoptic system to a polar low via interaction with the orography of Greenland, Tellus, 58A, Zhang, X., J.E. Walsh, J. Zhang, U.S. Bhatt and M. Ikeda, 2004: Climatology and interannual variability of arctic cyclone activity: , J. Climate, 17, Acknowledgements This research and network is primarily funded through a network grant from the Canadian Foundation for Climate and Atmospheric Sciences (CFCAS). We also acknowledge the financial and equipment infrastructure support from the National Science and Engineering Research Council (NSERC), Canada Foundation for Innovation (CFI), and the Northern Studies Training Program (NSTP). The authors also wish to thank its many collaborators who provided significant contributions: from Environment Canada - Meteorological Research Division (MRD), Climate Research Division (CRD), Hydrometeorological and Arctic Lab (HAL), Prairie and Arctic Storm Prediction Centre (PASPC), and the Weather and Environmental Monitoring Section; from the National Research Council Flight Research Lab; Nunavut Research Institute (NRI); Qulliq Energy Corp.; Indian and Northern Affairs Canada (INAC). A special thank you to George Liu (STAR data manager), Justin Gilligan (STAR Network Manager), Shannon Fargey and Alex Laplante for providing imagery and assistance with this article as well as all of the other STAR students who participated in the field project. McCabe, G.J., M.P. Clark and M.C. Serreze, 2001: Trends in northern hemisphere surface cyclone frequency and intensity, J. Climate, 14, Nawri, N. and R.E. Stewart, 2006: Climatological features of orographic low-level jets over Frobisher Bay. Atmos.-Ocean, 44, Stone, D.A., A.J. Weaver and F.W. Zwiers, 2000: Trends in Canadian precipitation intensity, Atmos-Ocean, 38,

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