A31G-0186
Characterization and First Measurements of the new CANDAC Raman Lidar (CRL)
The Canadian Network for the Detection of Atmospheric Change (CANDAC), a collaboration between several universities and government organizations, has established a suite of instruments in Eureka, Nunavut, Canada (79°59'N, 85°56'W). As part of this program, Dalhousie University's Rayleigh-Mie- Raman lidar has been installed at the sea-level atmospheric laboratory, (ØPAL). Designed for the remote profiling aerosol content, temperature, and water vapour, the lidar will provide a detailed dataset for further investigation of atmospheric thermodynamics, radiative transfer and cloud micro-physics. The ability to retrieve signal from a wide range of altitudes is important to make the measurements as extensive as possible. This system includes a number of feathers designed to expand this range, including the dynamic movement of the field stop. The approaches used and their comprehensive characterization is presented. Updated descriptions of instrument specifications and remote operations are presented as well as a detailed characterization of the seven channels. Of particular interest are the temperature and H2O vapour mixing ratios derived from these measurements. Calibration and preliminary results are shown, and the confidence in the retrievals is discussed. The ability to retrieve signal from a wide range of altitudes is important to make the measurements as extensive as possible.
A31G-0187
Polar Sunrise 2008 Comparison of Lidar Water Vapor Measurements from the IASOA PEARL Observatory in Eureka, Canada and ACE Satellite
Water vapor is an important part of the atmosphere due to its roles in the hydrological cycle, greenhouse heating and ozone chemistry. The stratospheric ozone lidar located at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Nunavut (80.2° N, 86.4° W) is jointly operated by the Canadian Network for Detection of Atmospheric Change (CANDAC) and Environment Canada. It has recently been upgraded to measure water vapor at 150 m vertical resolution in the polar troposphere up to about six kilometers, with measurements extending above this at lower vertical resolution. Successful validation of these measurements will allow scientific studies to begin with the coincident measurements from the lidar and suite of CANDAC instruments at PEARL. In concert with the lidar's well-established ozone and temperature profiles these new water vapor measurements will allow incidents of stratosphere-troposphere exchange to be monitored as well as, when combined with other measurements from PEARL instrumentation, detailed studies of ozone chemistry to be performed. With the motion of the polar vortex bringing it overhead and away from PEARL during the course of a campaign, it is possible to look at interactions between upper tropospheric jets and the vortex. Water vapor measurements have been taken and analyzed for eleven nights during the Canadian Arctic ACE Validation Campaign in February and March 2008. Calibration of the lidar has been obtained by comparing lidar measurements from seven clear nights to water vapor measurements from the regular radiosonde launches at the Eureka Weather Station. A consistent altitude dependent bias between the two instruments is found, giving us confidence in the calibration. Calibrated lidar measurements are currently being compared to water vapour measurements from overpasses by the Atmospheric Chemistry Experiment (ACE) satellite, as well as compared to the ozone measurements obtained during the campaign.
A31G-0188
Cloud fraction statistics derived from 34-months of high spectral resolution lidar data acquired at Eureka, Canada.
The Canadian Network for the Detection of Atmospheric Change (CANDAC) and the NOAA Study of
Environmental Arctic Change (SEARCH) have installed instrumentation at Eureka(80 deg N, 86 deg W) in the
Nunavut territory of Northern Canada. These instruments include the University of Wisconsin Arctic High
Spectral Resolution Lidar(AHSRL) and the NOAA 8.6 mm wavelength cloud radar (MMCR). Both instruments
were installed in Sept 2005.
This paper presents a record of cloud cover, cloud altitude and cloud phase derived from 34-months lidar
data. It also presents comparisons between lidar, radar, and convention meteorological observations of
cloudiness. It is shown that optically thin clouds are frequently observed. As a result, the observed fractional
cloud cover depends strongly on the optical depth threshold used to define the presence of cloud.
http://lidar.ssec.wisc.edu
A31G-0189
Ice Crystals Observed in the High Arctic at Eureka
Measurements of ice crystals from surface observers, the Arctic High Spectral Resolution Lidar (AHSRL), and a millimeter cloud radar (MMCR) from the Polar Environment Atmospheric Research Laboratory (PEARL) at Eureka, Nunavut Territory (80N 86W) are presented and analyzed for their impact on surface radiation measured with the Polar Atmospheric Emitted Radiance Interferometer (PAERI). The measurements show that ice crystals blowing from the mountainous terrain make an important contribution to the suspended particulate matter in the atmosphere, and have a substantial impact on the surface radiative forcing. The interpretation is supported by MODIS satellite measurements. The results have important implications for our understanding of wintertime radiative transfer and the impact of the different types of ice crystal precipitation.
A31G-0190
Seasonal Cycling of Carbon Dioxide and Turbulent Fluxes in Arctic at the SEARCH Station Eureka, Canada
Several long-term research observatories near the coast of the Arctic Ocean have been identified for enhanced instrumentation to monitor the changing Arctic climate. Eureka site (80.0 N, 85.9 W) is a small research base on Slidre Fjord on Ellesmere Island in the Canadian territory of Nunavut established in 1947 as part of Arctic weather stations network. Beginning in 2004, remote sensors and in-situ instrumentation were installed at Eureka in framework of the Surface Fluxes at Study of Environmental Arctic Change (SEARCH) Program. Instrumentation at Eureka has included a cloud radar and lidar to monitor the cloud macro and microphysical properties and a 10-m flux tower instrumented at various heights for surface-layer turbulence measurements. Sonic anemometers are located at 3 and 8 m heights while high-speed Licor 7500 infrared gas analyzer (water moisture and carbon dioxide measurements) at 7.5 m height. Turbulent fluxes are based on the eddy-covariance technique. The thermal profile is measured by several slow T/RH sensors and differential temperature pairs at 2, 5 and 10 m heights. Surface characteristics are measured by thermal soil probes, an infrared surface temperature sensor, and a sonic snow-depth sensor. This study focuses on the dynamics of turbulent fluxes including water vapor and carbon dioxide transfer at daily and seasonal time scales based on long-term measurements made at Eureka. Different aspects of the atmospheric boundary layer behavior as well as vegetation structure at Eureka and their impact on the turbulent transfer and carbon dioxide fluxes are discussed.
A31G-0191
The First Two Years of Stratospheric Trace Gas Measurements With a New Fourier Transform Spectrometer at Eureka, Nunavut
The process of rapid stratospheric ozone loss in the polar regions begins during the polar winter, when dynamical and chemical conditions lead to the formation of reactive chlorine and bromine radicals. Long-term data sets of Arctic chemical composition measurements are needed to better understand the process of ozone loss, the links between ozone depletion and climate change, and the future evolution of ozone. For this purpose, a new high-resolution Fourier transform infrared spectrometer was installed at the Polar Environment Atmospheric Research Laboratory (PEARL) at Eureka, Nunavut in July 2006. Since then, this instrument has been used to measure solar absorption spectra in the mid-infrared. Using the optimal estimation technique, total columns and some vertical profile information can be retrieved for a suite of trace gases that are involved in the process of stratospheric ozone depletion. Total columns of O3, HCl, ClONO2, HNO3, and HF will be presented for the first two years of operation, with a focus on the two Canadian Arctic ACE Validation spring campaigns that took place in 2007 and 2008. Very different dynamical situations were observed over Eureka during these two spring periods: the impact of these conditions on the trace gas measurements will be shown.
A31G-0192
Comparison of MLT dynamics at two Arctic stations in winter
Two ground-based instruments called SATI (Spectral Airglow Temperature Imager) to monitor the airglow temperature and emission rate in the polar MLT (Mesosphere and Lower Thermosphere) region have been in operation at Resolute Bay (74.68 N, 94.90 W) and at Eureka (80.00 N, 86.25 W) since November, 2001, and November, 2007, respectively. The Eureka SATI was developed for the CANDAC (Canadian Network for the Detection of Atmospheric Change) project. The SATI instrument is a two-channel, Fabry-Perot spectrometer, and measures the OH and O2 airglow emissions at 87 km and 94 km, where the airglow emission peaks are located, from the respective annular field of views. These horizontal and vertical measurements are used to investigate the atmospheric wave dynamics in the MLT region at the two locations. The results on the wave propagation characteristics are compared and discussed.
A31G-0193
Radar, Radiometers, Interferometer and Lidar in Eureka, Canada and Barrow, Alaska for Cloud and Aerosol Studies
The NOAA Studies of Environmental Arctic Change Program (SEARCH) has cooperated with the Canadian
Network for Detection of Arctic Change (CANDAC) Program to install a suite of atmospheric sensors in
Eureka, Canada. These include cloud radar, high spectral resolution lidar, a Polar Atmospheric Emitted
Radiance Interferometer and a microwave radiometer. These instruments represent a combination of active
and passive sensors operating in a range of frequencies that collectively make comprehensive
measurements of cloud, aerosol, and clear sky properties. The measurements include parameters such as
cloud droplet and crystal sizes, cloud phase, integrated liquid water and atmospheric vapor, the boundary-
layer height, and radiative fluxes. These measurements are modeled on the longer term measurements from
similar sensors in Barrow, Alaska at the Department of Energy Atmospheric Radiation Measurement (ARM)
site. Two case studies are presented for the Barrow and Eureka sites showing mixed phase clouds
embedded in an atmosphere with detectable aerosol layers that appear to become entrained in the cloud
with consequent effects on the cloud microphysics. The case studies are interpreted in the context of the two
different locations and demonstrate the utility of the simultaneous measurements to study complex cloud and
aerosol interactions and the resulting effects on Arctic surface radiation balances in more than one region
simultaneously.
http://psd.etl.noaa.gov/psd/psd3/arctic/search/
A31G-0194
A Tale of Two Air-Temperature Records in Barrow, Alaska: 1976-2005
The National Weather Service (NWS) air temperature record from Barrow, Alaska is one of the most widely used datasets for demonstrating Arctic warming. Yet, when examining any temperature record, several factors must first be established to prove it is a reliable, unbiased archive. In the 30 years since the beginning of the GMD record, Barrow has grown from 2200 to more than 4600 residents. Recent measurements suggests that there is a substantial heat island in the village (Hinkel et al., 2003; 2004), particularly in the winter and comparison of NWS records in downtown and at the National Oceanic and Atmospheric Administration's ESRL Global Monitoring Division (GMD) data from several miles upwind of the village, show a distinct difference between urban and rural temperatures in the early portion of the record. In addition, instrumentation changes were implemented at both sites. A station move took place. Coastal influences are also large near Barrow and distance from the coast may be an influence. Unraveling the impacts of these considerations on the temperature differences between the NWS and GMD sites is challenging and this paper is only an initial investigation of these issues. However, this example is a stark illustration that the small changes measured over time are often of similar magnitude to those which can be caused by the measurements programs themselves: instrument bias and change, station moves, urbanization, etc. While recent programs such as the Historical Climate Network are great strides, additional efforts must be made to analyze and understand what trends in the past were due to what influences before it can be established that increasing temperatures are due to climate change.
A31G-0195
Arctic Mixed-Phase Cloud Microphysical Properties Deduced From ARM Surface And Aircraft Measurements During M-PACE
During the Mixed-Phase Arctic Cloud Experiment (M-PACE), persistent single-layered boundary layer stratus was observed by ground-based remote sensors at Barrow and Oliktok Point, Alaska, from 9 to 14 October 2004. The University of North Dakota (UND) Citation aircraft served as an in-situ platform to provide the bulk microphysics for the Arctic stratiform clouds. The cloud phase (mixed-phase) is identified from a suite of measurements by surface remote sensors and atmospheric radiosonde. Microphysical retrieval techniques are based upon the measurements from Millimeter-wavelength Cloud Radar (MMCR), Microwave Radiometer (MWR), and Citation aircraft. A radar reflectivity partition function has been constructed and analyzed in terms of temperature and altitude for mixed-phase clouds. The cloud phases (liquid and ice components) are partitioned and separated by the radar reflectivity partition function in combination with MMCR reflectivity measurements. Empirical radar reflectivity-based relationships are then developed and used to derive profiles of both liquid and ice microphysical properties, such as water content and particle size. The retrievals have been examined and compared with the in-situ measurements for three case studies on 9, 10, and 12 October 2004 during M-PACE. For the liquid phase properties, the averaged retrieved LWC and re are with uncertainties of 0.303±0.205 gcm-3 and 11.5±4.64 μm, which indicate about 60% and 26% higher than the in-situ measurements. For the ice phase, microphysical retrievals mainly depend on the partitioned ice phase radar reflectivity. The averaged retrieved IWC and Dei are with uncertainties of 0.037±0.029 gcm-3 and 50.5±13.3 μm, which are about 150% and 1% higher than in-situ measurements, respectively. The assessment and validation of the retrieval techniques with the observations made on 4 May 1998 during the SHEBA and FIRE-ACE field experiments in this study demonstrate that the retrieval methods are applicable to other seasons and locations in the Arctic region.
A31G-0196
The Diurnal Cycle in the NOAA/ESRL Barrow CO2 Data 1973-2007: A Long Term Record of Ecosystem Change
Atmospheric carbon dioxide has been measured continuously at the NOAA/ESRL/GMD observatory in Barrow, Alaska since 1973. The station is located 1.7 km inland from the shore of the Arctic Ocean. CO2 exchange from the undisturbed tundra along this fetch produces diurnal cycles in the atmospheric CO2 record during the summer growing season. Although these data cannot be used to directly measure the CO2 flux, useful information about seasonal and long-term variations can be derived by comparison with temperature, wind, solar radiation, and surface albedo measurements at the observatory. The amplitude of the diurnal CO2 cycle is strongly correlated with temperature and provides a measure of the time of onset and length of the growing season over 34 years.
A31G-0197
Comparison of Barrow, Alaska and Tiksi, Russia Climate variability Using Historical Meteorological Records
A digital archive of the historical Tiksi meteorological station data (1934 to present) has recently been
created for air surface temperature, surface pressure, wind velocity, and cloudiness. A detailed analysis of
the Tiksi data has been performed showing the influences of synoptic systems and cloudiness on
temperature trends and shore fast ice cycles (presented as a companion paper in this session). In this
study, the identical statistical methods are applied to the Barrow, Alaska meteorological data sets. Although
the data sets for Barrow started at the beginning of the 20th century, the data were not collected with the
same temporal regularity as the Tiksi data (4 times/day) until the 1960s; so this latter period is the focus of
comparisons.
http://psd.etl.noaa.gov/psd/psd3/arctic/search/
A31G-0198 INVITED
Climate Variability in the region of the future Tiksi Hydrometeorological Observatory A Contribution to the International Arctic Systems for Observing the Atmosphere - IASOA
In the framework of a joint Roshydromet and NOAA project entitled "Establishing a Modern Weather Station and Research Observatory in Tiksi, Russia", a digital archive of the historical Tiksi meteorological station data (1934 to present) has been created. Statistics for 4 hour, daily, monthly and seasonally averaged data have been calculated air surface temperature, surface pressure, wind velocity, and cloudiness. These suggest that the influences of synoptic systems on temperature trends are significant. Strong trends in cloudiness, (increasing in winter and decreasing in summer) have been detected that could contribute to weak positive trends of surface air temperature during these seasons. Wind analysis reveals increased southerly winds in fall, winter and spring. Sea ice cover in the adjacent to Tiksi Sogo Bay shows significant increase in the length of the ice-free season but also some increases in the fast ice seasonal maximum thickness. The data have also been used as external forcing to study the time evolution of fast ice in the study area using the AARI thermodynamic sea ice model. Two problems have been revealed. The first is connected to the relationship between measured snow deposits and the badly determined processes of snow redistribution during snowstorms. The second problem is related to absence of an adequate description of fast ice breakup in summer and re-establishment in autumn. Both these problems are significantly improved by using the historical information as model constraints.
A31G-0199
Preliminary Results from the First Deployment of a Tethered-Balloon Cloud Particle Imager Instrument Package in Arctic Stratus Clouds at Ny-Alesund
A tethered balloon system specifically designed to collect microphysical data in mixed-phase clouds was
deployed in Arctic stratus clouds during May 2008 near Ny-Alesund, Svalbard, at 79 degrees North Latitude.
This is the first time a tethered balloon system with a cloud particle imager (CPI) that records high-resolution
digital images of cloud drops and ice particles has been operated in cloud. The custom tether supplies
electrical power to the instrument package, which in addition to the CPI houses a 4-pi short-wavelength
radiometer and a met package that measures temperature, humidity, pressure, GPS position, wind speed
and direction. The instrument package was profiled vertically through cloud up to altitudes of 1.6 km. Since
power was supplied to the instrument package from the ground, it was possible to keep the balloon package
aloft for extended periods of time, up to 9 hours at Ny- Ålesund, which was limited only by crew fatigue.
CPI images of cloud drops and the sizes, shapes and degree of riming of ice particles are shown throughout
vertical profiles of Arctic stratus clouds. The images show large regions of mixed-phase cloud from –8 to –2
C. The predominant ice crystal habits in these regions are needles and aggregates of needles. The
amount of ice in the mixed-phase clouds varied considerably and did not appear to be a function of
temperature. On some occasions, ice was observed near cloud base at –2 C with supercooled cloud above
to – 8 C that was devoid of ice. Measurements of shortwave radiation are also presented. Correlations
between particle distributions and radiative measurements will be analyzed to determine the effect of these
Arctic stratus clouds on radiative forcing.
http://www.specinc.com
A31G-0200
In-Situ Radiometric Measurements of the Radiation Environment in Arctic Mixed-Phase Clouds from a Tethered Balloon System
Shortwave radiometric measurements within arctic boundary layer clouds were made with an instrument deployed on a tethered balloon system during a May/June 2008 experimental campaign at the arctic research station located at 78.9 N in Ny Alesund, Norway. This tethered balloon system enabled in-situ measurement of the mean light intensity at 500 nm and 800 nm using a specially designed radiometer attached to the tether. The balloon system had the ability to profile clouds vertically from ground level to 1.6 km and also to loiter at a fixed altitude for extended time periods. These radiometric measurements coupled with meteorological data and cloud particle images collected by other instruments attached to the balloon provide a unique picture of the radiation field within mixed-phase clouds. Data from several different deployments, encompassing a variety of cloudy sky conditions, will be presented and discussed.
A31G-0201
Surface layer temperature structure observed at Summit, Greenland
The evolution of the surface layer thermodynamic structure at Summit, Greenland was studied using high- frequency temperature measurements made during the summer of 2008. Ten fine-wire thermocouples mounted from 0.01 m to 45 m above the snow surface were continuously sampled at a frequency of 1 Hz. Preliminary results indicate the presence of strong inversions with gradients averaging about 0.3 K/m. During these inversion episodes, mixing events were observed to occur near the surface below 2 m AGL. These mixing events were decoupled from the upper levels and were associated with warming indicated by increases in temperature of approximately 4-5 K that occurred over periods of 5-30 min. Inversion destruction occurred over the course of many hours leading to the development of a neutral, mixed layer. Measurements above 30 m showed increased variance in temperature that was associated with entrainment and mixing as the surface layer warmed. However, the increased temperature variance did not occur at the surface. It is anticipated, that these high-frequency thermodynamic observations will lead to a better interpretation of atmosphere-snow interactions and associated snow photochemistry.
A31G-0202
Seasonal Behavior of Radiosonde-measured Temperature and Winds at Three Arctic Stations: Sodankyla (Finland), Barrow (Alaska), and Eureka (Canada)
A cluster analysis of temperatures, geopotential heights, and winds was performed on 60 years of rawinsonde data for three Arctic stations (Sodankyla, Barrow, and Eureka). In order to process data covering such a long period of time, it was necessary to use only surface, 1000, 850, 700, and 500 hPa levels since this was the limit of the vertical resolution in the lower troposphere in the earlier sondes. Thus, only large-scale behavior can be assessed with this analysis. The cluster analysis of sonde data produced groups of profiles that were clustered by season, showing summer, winter, and transition-season characteristics. Differences among the stations will be discussed. For instance, the Eureka profiles were more likely to have a shallow temperature inversion near the surface in the summer than Barrow, and a more pronounced temperature inversion in winter than Barrow. Individual clusters have been compared to the long-term record by comparing cluster averages of temperature with temperatures averaged over all sondes used in the analysis.
A31G-0203
Rayleigh Lidar Network Observations and Analysis of the Evolution of the Arctic Middle Atmosphere during the IPY Winter 2007-2008
A network of five Rayleigh lidars (i.e., Kuehlungsborn, Germany (54N, 12E), Chatanika, USA (65N, 147W),
Kangerlussuaq, Greenland (67N, 51W), Andoya, Norway (69N, 16E), and Eureka, Canada (80N, 86W)) has
been used to measure middle atmosphere temperature profiles through the 2007-2008 winter and spring.
These measurements are being made as part of the project Pan-Arctic Studies of the Coupled Tropospheric,
Stratospheric and Mesospheric Circulation as part of the Fourth International Polar Year (IPY-4). This
project is a component of the two full IPY proposals; International Arctic Systems for Observing the
Atmosphere (IASOA) and The Structure and Evolution of the Polar Stratosphere and Mesosphere and Links
to the Troposphere during IPY (SPARC-IPY). The lidar network is part of the Arctic Observing Network
(AON). The resolution and distribution of these lidar measurements provides the basis for a pan-Arctic
perspective of the middle atmosphere circulation. We combine these lidar data with satellite observations
and meteorological re-analyses to study the structure, evolution, and variability of the Arctic stratospheric
vortex and Aleutian anticyclone. In this study we present the evolution of the Arctic middle atmosphere
during the winter of 2007-2008. We highlight a stratospheric warming event that occurred during 20-26
February 2008. During this week the vortex was disrupted by the Aleutian anticyclone, then split at higher
altitudes, and eventually reformed. The lidar measurements show that the altitude and temperature of the
stratopause vary considerably (10 km, 30 K) from night-to-night and that the observed temperature structure
often differs from that reported by the standard climatologies (e.g., SPARC). We discuss the observations in
terms of the Study of Environmental Arctic Change (SEARCH).
http://research.iarc.uaf.edu/IPY-CTSM/index.php
A31G-0204
Evaluation of Polar WRF Across the Arctic Using IASOA Observations
The Weather Research and Forecasting (WRF) model is a regional model with ever increasing use in solving problems ranging from real-time forecasting to long duration climate simulations. Past regional models have had difficulties in properly simulating the polar atmosphere with particular problems involving the radiation and cloud processes. This study will present the results of an evaluation of the WRF model in the polar regions in comparison against observations from the International Arctic Systems for Observing the Atmosphere (IASOA) network. The observations of meteorology state variables, atmospheric radiation, and clouds will be compared against a preferred configuration of WRF physics parameterizations to evaluate the performance of WRF across multiple locations in the Arctic. The results will indicate the suitability for the use of WRF across different regions in the Arctic as well as areas of improvement. Future applications of WRF include it being the atmospheric component of a regional Arctic system model for studying climate change on the regional scale in the Arctic.