Thomas J. Duck

H2O at the Phoenix Landing Site

Phoenix Ascending The Phoenix mission landed on Mars in March 2008 with the goal of studying the ice-rich soil of the planets northern arctic region. Phoenix included a robotic arm, with a camera attached to it, with the capacity to excavate through the soil to the ice layer beneath it, scoop up soil and water ice samples, and deliver them to a combination of other instruments—including a wet chemistry lab and a high-temperature oven combined with a mass spectrometer—for chemical and geological analysis. Using this setup, Smith et al. (p. 58) found a layer of ice at depths of 5 to 15 centimeters, Boynton et al. (p. 61) found evidence for the presence of calcium carbonate in the soil, and Hecht et al. (p. 64) found that most of the soluble chlorine at the surface is in the form of perchlorate. Together these results suggest that the soil at the Phoenix landing site must have suffered alteration through the action of liquid water in geologically the recent past. The analysis revealed an alkaline environment, in contrast to that found by the Mars Exploration Rovers, indicating that many different environments have existed on Mars. Phoenix also carried a lidar, an instrument that sends laser light upward into the atmosphere and detects the light scattered back by clouds and dust. An analysis of the data by Whiteway et al. (p. 68) showed that clouds of ice crystals that precipitated back to the surface formed on a daily basis, providing a mechanism to place ice at the surface. A water ice layer was found 5 to 15 centimeters beneath the soil of the north polar region of Mars. The Phoenix mission investigated patterned ground and weather in the northern arctic region of Mars for 5 months starting 25 May 2008 (solar longitude between 76.5° and 148°). A shallow ice table was uncovered by the robotic arm in the center and edge of a nearby polygon at depths of 5 to 18 centimeters. In late summer, snowfall and frost blanketed the surface at night; H2O ice and vapor constantly interacted with the soil. The soil was alkaline (pH = 7.7) and contained CaCO3, aqueous minerals, and salts up to several weight percent in the indurated surface soil. Their formation likely required the presence of water.

Mars Water-Ice Clouds and Precipitation

Phoenix Ascending The Phoenix mission landed on Mars in March 2008 with the goal of studying the ice-rich soil of the planets northern arctic region. Phoenix included a robotic arm, with a camera attached to it, with the capacity to excavate through the soil to the ice layer beneath it, scoop up soil and water ice samples, and deliver them to a combination of other instruments—including a wet chemistry lab and a high-temperature oven combined with a mass spectrometer—for chemical and geological analysis. Using this setup, Smith et al. (p. 58) found a layer of ice at depths of 5 to 15 centimeters, Boynton et al. (p. 61) found evidence for the presence of calcium carbonate in the soil, and Hecht et al. (p. 64) found that most of the soluble chlorine at the surface is in the form of perchlorate. Together these results suggest that the soil at the Phoenix landing site must have suffered alteration through the action of liquid water in geologically the recent past. The analysis revealed an alkaline environment, in contrast to that found by the Mars Exploration Rovers, indicating that many different environments have existed on Mars. Phoenix also carried a lidar, an instrument that sends laser light upward into the atmosphere and detects the light scattered back by clouds and dust. An analysis of the data by Whiteway et al. (p. 68) showed that clouds of ice crystals that precipitated back to the surface formed on a daily basis, providing a mechanism to place ice at the surface. Laser remote sensing from Mars’ surface revealed water-ice clouds that formed during the day and precipitated at night. The light detection and ranging instrument on the Phoenix mission observed water-ice clouds in the atmosphere of Mars that were similar to cirrus clouds on Earth. Fall streaks in the cloud structure traced the precipitation of ice crystals toward the ground. Measurements of atmospheric dust indicated that the planetary boundary layer (PBL) on Mars was well mixed, up to heights of around 4 kilometers, by the summer daytime turbulence and convection. The water-ice clouds were detected at the top of the PBL and near the ground each night in late summer after the air temperature started decreasing. The interpretation is that water vapor mixed upward by daytime turbulence and convection forms ice crystal clouds at night that precipitate back toward the surface.

Transport of forest fire emissions from Alaska and the Yukon Territory to Nova Scotia during summer 2004

[1] Emissions from forest fires in Alaska and the Yukon Territory were observed at Chebogue Point, Nova Scotia (43.7N, 66.1W), between 11 and 13 July 2004. Smoke aerosols were first detected in the free troposphere by a Raman lidar and extended up to 8 km altitude. The plume was not evident at the surface until the second day, when increases in CO, acetonitrile (CH3CN), benzene, and aerosol mass concentrations were observed by in situ instrumentation. Enhancement ratios for each species relative to CO agreed with the range of values from other measurements of the same plume. The surface aerosols had an elevated black carbon fraction relative to both CO and organic matter, and the ratio of black to organic carbon was higher than what is typically observed in fresh smoke. The emissions were tracked back to Alaska and the Yukon Territory using aerosol optical depth measurements from the Aqua MODIS satellite instrument, and the transport was reconstructed using the GEOS-Chem and FLEXPART atmospheric models. The analysis suggests that aerosols were injected into the atmosphere in proportion to CO and that aerosol removal processes were weak during the 7 to 9 day transit time in the free troposphere. Transport of the tracers to the ground was strongly connected to synoptic-scale features in the surface meteorology.

The Gravity Wave–Arctic Stratospheric Vortex Interaction

Abstract Four hundred and twenty-two nights of stratospheric gravity wave observations were obtained with a Rayleigh lidar in the High Arctic at Eureka (80°N, 86°W) during six wintertime measurement campaigns between 1992/93 and 1997/98. The measurements are grouped in positions relative to the arctic stratospheric vortex for comparison. Low gravity wave activity is found in the vortex core, outside of the vortex altogether, and in the vortex jet before mid-December. High gravity wave activity is only found in the vortex jet after late December, and is related to strengthening of the jet and decreased critical-level filtering. Calculations suggest that the drag induced by the late-December gravity wave energy increases drives a warming already observed in the vortex core, thereby reducing vortex-jet wind speeds. The gravity waves provide a feedback mechanism that regulates the strength of the arctic stratospheric vortex.

Modeling ozone laminae in ground‐based Arctic wintertime observations using trajectory calculations and satellite data

Reverse-trajectory calculations initialized with ozone observed by the Upper Atmosphere Research Satellite Microwave Limb Sounder (MLS) provide high-resolution ozone profiles for comparison with lidar and ozonesonde observations from the Arctic Stratospheric Observatory facility near Eureka in the Canadian Arctic (∼80°N, 86°W). By statistical measures, calculated profiles show a small average improvement over MLS profiles in the agreement of small-scale structure with that in ground-based observations throughout the stratosphere, and a larger (although still modest) and more consistent improvement in the lower stratosphere. Nearly all of the calculated profiles initialized with daily gridded MLS data show some improvement in the lower stratosphere. Even in cases where overall agreement between profiles is mediocre, there are frequently one or more individual features in the calculated profiles that strongly resemble laminae in the ground-based observations. Differential advection of ozone by the large-scale winds leads to lamination in three distinct ways. Filamentation results in lamination throughout the stratosphere, with comparable features arising from initializations with gridded MLS data and with potential vorticity/θ-space reconstructions of MLS data (reconstructed (RC) fields). Laminae also form in the middle and lower stratosphere in conjunction with intrusions into the vortex; while calculations initialized with RC fields produce laminae, the agreement of structure calculated using gridded MLS initialization data with ground-based observations is distinctly better. Inside the lower stratospheric vortex, laminae form by advection of local features in the MLS initialization fields; RC-initialized calculations fail to produce any significant features since these local ozone variations are not strongly correlated with potential vorticity. That local features observed by MLS are needed to produce laminae resembling those in independent ground-based observations at Eureka indicates that both datasets are capturing real atmospheric features.

Surface Energy Balance Framework for Arctic Amplification of Climate Change

AbstractUsing 22 Canadian radiosonde stations from 1971 to 2010, the annually averaged surface air temperature trend amplification ranged from 1.4 to 5.2 relative to the global average warming of 0.17°C decade−1. The amplification factors exhibit a strong latitudinal dependence varying from 2.6 to 5.2 as the latitude increases from 50° to 80°N. The warming trend has a strong seasonal dependence with the greatest warming taking place from September to April. The monthly variations in the warming trend are shown to be related to the surface-based temperature inversion strength and the mean monthly surface air temperatures.The surface energy balance (SEB) equation is used to relate the response of the surface temperature to changes in the surface energy fluxes. Based on the SEB analysis, there are four contributing factors to Arctic amplification: 1) a larger change in net downward radiation at the Arctic surface compared to the global average; 2) a larger snow and soil conductive heat flux change than the g...

A detailed record of high Arctic middle atmospheric temperatures

An improved method and apparatus for quickly and efficiently updating the original source volume and original target volumes after the original source volume has become temporarily unavailable. The original target volume is characterized as a source volume while the original source volume is temporarily unavailable. Transfer lists of different data blocks are generated. Data blocks not originally found on a source are copied to the target. Data blocks included on a target that were not found on the source are removed. By focusing upon specific data blocks, this technique avoids the use of filer overhead and other computational resources that would be expended if the entire volume were recopied.

Aircraft-protection radar for use with atmospheric lidars

A modified X-band radar system designed to detect aircraft during atmospheric lidar operations is described and characterized. The capability of the radar to identify aircraft approaching from a variety of directions was tested, and first detections were found to occur between the -10 and -3 dB perimeters of the gain horns antenna pattern. A model based on the radar equation projects the performance of the radar for different sizes of aircraft and at different altitude levels. Risk analysis indicates that the probability of accidently illuminating an aircraft with the laser beam during joint lidar-radar operations is low.

Lidar measurements of thin laminations within Arctic clouds

Very thin (< 10 m) laminations within Arctic clouds have been observed in all seasons using the Canadian Network for the Detection of Atmospheric Change (CANDAC) Rayleigh-Mie-Raman lidar (CRL) at the Polar Environment Atmospheric Research Laboratory (PEARL; located at Eureka, Nunavut in the Canadian High Arctic). CRL’s time (1 min) and altitude (7.5 m) resolution from 500 m to 12+ km altitude make these measurements possible. We have observed a variety of thicknesses 5 for individual laminations, with some at least as thin as the detection limit of the lidar (7.5 m). The clouds which contain the laminated features are typically found below 4 km, can last longer than 24 h, and occur most frequently during periods of snow and rain, often during very stable temperature inversion conditions. Results are presented for range-scaled photocounts at 532 nm and at 355 nm, ratios of 532/355 nm photocounts, and 532 nm linear depolarization parameter, with context provided by twice-daily Eureka radiosonde temperature and relative humidity profiles. 10 Figure 1. Thin laminated layers within an Arctic cloud. 532 nm range-scaled counts from the CRL lidar at Eureka, Nunavut showing quasihorizontal layers, as thin as 7.5 m each, within a cloud on 7 March 2016, during snowing conditions.

Infrared Measurements Throughout Polar Night using Two AERIs in the Arctic

The Extended-range Atmospheric Emitted Radiance Interferometer (E-AERI) is a moderate resolution (1 cm−1) Fourier transform infrared spectrometer for measuring the absolute downwelling infrared spectral radiance from the atmosphere between 400 and 3000 cm−1. The extended spectral range of the instrument permits monitoring of the 400–550 cm−1 (20–25 μm) region, where much of the infrared surface cooling currently occurs in the dry air of the Arctic. The E-AERI provides information about radiative balance, trace gases, and cloud properties in the Canadian high Arctic. The instrument was installed at the Polar Environment Atmospheric Research Laboratory (PEARL) Ridge Lab at Eureka, Nunavut, in October 2008. Measurements are taken every seven minutes year-round (precipitation permitting), including polar night when the solar-viewing spectrometers are not operated. A similar instrument, the University of Idaho’s Polar AERI (P-AERI), was installed at the Zero-altitude PEARL Auxiliary Laboratory (0PAL), 15 km away from the Ridge Lab, from March 2006 to June 2009. During the period of overlap, these two instruments provided calibrated radiance measurements from two different altitudes. Retrievals of total columns of various trace gases are being evaluated using a prototype version of the retrieval algorithm SFIT2 modified to analyze emission features. In contrast to solar absorption measurements of atmospheric trace gases, which depend on sunlit clear-sky conditions, the use of emission spectra allows measurements year-round (except during precipitation events or when clouds are present). This capability allows the E-AERI to provide temporal coverage throughout the four months of polar night and to measure the radiative budget throughout the entire year. This presentation will describe the new E-AERI instrument, its performance evaluations, and clear sky vs. cloudy measurements.