Atmospheric carbon monoxide (CO) distributions are controlled by anthropogenic emissions, biomass burning, transport and oxidation by reaction with the hydroxyl radical (OH). Quantifying trends in CO is therefore important for understanding changes related to all of these contributions. Here we present a comprehensive record of satellite observations from 2000 through 2011 of total column CO using the available measurements from nadir-viewing thermal infrared instruments: MOPITT, AIRS, TES and IASI. We examine trends for CO in the Northern and Southern Hemispheres along with regional trends for Eastern China, Eastern USA, Europe and India. We find that all the satellite observations are consistent with a modest decreasing trend similar to -1% yr(-1) in total column CO over the Northern Hemisphere for this time period and a less significant, but still decreasing trend in the Southern Hemisphere. Although decreasing trends in the United States and Europe have been observed from surface CO measurements, we also find a decrease in CO over E. China that, to our knowledge, has not been reported previously. Some of the interannual variability in the observations can be explained by global fire emissions, but the overall decrease needs further study to understand the implications for changes in anthropogenic emissions.

The advanced E-Region Wind Interferometer (ER-WIN II) combines the imaging capabilities of a CCD detector with the wide field associated with field-widened Michelson interferometry. This instrument is capable of simultaneous multi-directional wind observations for three different airglow emissions (oxygen green line (O(S-1)) at a height of similar to 97 km, the (P)Q(7) and P-P(7) emission lines in the O-2(0-1) atmospheric band at similar to 93 km and P-1(3) emission line in the (6, 2) hydroxyl Meinel band at similar to 87 km) on a three minute cadence. In each direction, for 45 s measurements for typical airglow volume emission rates, the instrument is capable of line-of-sight wind precisions of similar to 1 ms(-1) for hydroxyl and O(S-1) and similar to 4 ms(-1) for O-2. This precision is achieved using a new data analysis algorithm which takes advantage of the imaging capabilities of the CCD detector along with knowledge of the instrument phase variation as a function of pixel location across the detector. This instrument is currently located in Eureka, Nunavut as part of the Polar Environment Atmospheric Research Laboratory (PEARL) (80 degrees N, 86 degrees W). The details of the physical configuration, the data analysis algorithm, the measurement calibration and validation of the observations from December 2008 and January 2009 are described. Field measurements which demonstrate the capabilities of this instrument are presented. To our knowledge, the wind determinations with this instrument are the most accurate and have the highest observational cadence for airglow wind observations of this region of the atmosphere and match the capabilities of other wind-measuring techniques.

[1] Four years of trace gas measurements have been acquired using the Bruker 125HR Fourier Transform Infrared (FTIR) spectrometer installed at the Polar Environment Atmospheric Research Laboratory (PEARL) in the Canadian high Arctic. These have been compared with data from three models, namely the Canadian Middle Atmosphere Model Data Assimilation System (CMAM-DAS), the Global Environmental Multiscale stratospheric model with the online Belgium Atmospheric CHemistry package (GEM-BACH), and the off-line 3D chemical transport model SLIMCAT to assess the total reactive nitrogen, NO(y), budget above Eureka, Nunavut (80.05 degrees N, 86.42 degrees W). The FTIR data have been also compared with satellite measurements by the Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS). The FTIR is able to measure four of the five primary species that form NO(y): NO, NO(2), HNO(3), and ClONO(2), while the fifth, N(2)O(5), was obtained using the N(2)O(5)/(NO + NO(2)) ratio derived from the models and ACE-FTS. Combining these results, a four-year time series of NO(y) 15-40 km partial columns was calculated. Comparisons with each model were made, revealing mean differences (+/- standard error of the mean) relative to the FTIR of (-16.0 +/- 0.6)%, (5.5 +/- 1.0)%, and (-5.8 +/- 0.4)% for CMAM-DAS, GEM-BACH, and SLIMCAT, respectively. The mean difference between the ACE-FTS and FTIR NO(y) partial columns was (5.6 +/- 2.3)%. While we found no significant seasonal and interannual differences in the FTIR NO(y) stratospheric columns, the partial columns display nearly twice as much variability during the spring compared to the summer period.

Weather observations made at Eureka, on Ellesmere Island in the Canadian High Arctic, have been archived since 1953. The time series, averages, and seasonal cycles of surface temperature, pressure, dew point, relative humidity, cloud cover, wind speed, and direction are presented for the period from 1954 to 2007. Also shown are the time series and averages for the 500 mb temperature, 900 to 500 mb thickness, 500 mb wind speed, and various boundary-layer stability parameters. Some of the main trends found are 1) an annual average surface warming of 3.2 degrees C since 1972, with summer exhibiting the least warming, 2) a reduction in the frequency of strong anticyclonic events in the winter, 3) a reduction in surface wind speeds except in the summer, 4) a 1.0 degrees C warming in the 500 mb temperature since 1961, with the greatest warming occurring in the spring and summer, and 5) a 10% increase in precipitable water all year round since 1961 but dominated by the spring, summer, and autumn seasons. The importance of open water in the Arctic Ocean for summer temperatures and humidity, of the North Atlantic Oscillation for winter interannual pressure variability, and of precipitable water for winter temperatures are highlighted in this climatology.

The meteor trail echo decay rates are analysed on-site to provide daily temperatures near 90 km. In order to get temperatures from trail decay times, either knowledge of the pressure or the background temperature height gradient near 90 km is required (Hocking, 1999). Hocking et al. (2004) have developed an empirical 90 km temperature gradient model depending only on latitude and time of year, which is used in the SKiYMET on-site meteor temperature analysis. Here we look at the sensitivity of the resulting temperature to the assumed gradient and compare it and the temperatures with daily AuraMLS averages near Eureka. Generally there is good agreement between radar and satellite for winter temperatures and their short-term variations. However there is a major difference in mid-summer both in the temperatures and the gradients. Increased turbulence in summer, which may overwhelm the ambipolar diffusion even at 90 km, is likely a major factor. These differences are investigated by generating ambipolar-controlled decay times from satellite pressure and temperature data at a range of heights and comparing with radar measurements. Our study suggests it may be possible to use these data to estimate eddy diffusion coefficients at heights below 90 km. Finally the simple temperature analysis (using satellite pressures), and a standard meteor wind analysis are used to compare mean diurnal variations of temperature (T) with those of zonal wind (U) and meridional wind (V) in composite multi-year monthly intervals.

[1] Biomass burning is a major source of pollution in the tropical Southern Hemisphere, and fine mode carbonaceous particles are produced by the same combustion processes that emit carbon monoxide ( CO). In this paper we examine these emissions with data from the Terra satellite, CO profiles from the Measurement of Pollution in the Troposphere (MOPITT) instrument, and fine-mode aerosol optical depth (AOD) from the Moderate-Resolution Imaging Spectroradiometer ( MODIS). The satellite measurements are used in conjunction with calculations from the MOZART chemical transport model to examine the 2003 Southern Hemisphere burning season with particular emphasis on the months of peak fire activity in September and October. Pollutant emissions follow the occurrence of dry season fires, and the temporal variation and spatial distributions of MOPITT CO and MODIS AOD are similar. We examine the outflow from Africa and South America with emphasis on the impact of these emissions on clean remote regions. We present comparisons of MOPITT observations and ground-based interferometer data from Lauder, New Zealand, which indicate that intercontinental transport of biomass burning pollution from Africa often determines the local air quality. The correlation between enhancements of AOD and CO column for distinct biomass burning plumes is very good with correlation coefficients greater than 0.8. We present a method using MOPITT and MODIS data for estimating the emission ratio of aerosol number density to CO concentration which could prove useful as input to modeling studies. We also investigate decay of plumes from African fires following export into the Indian Ocean and compare the MOPITT and MODIS measurements as a way of estimating the regional aerosol lifetime. Vertical transport of biomass burning emissions is also examined using CO profile information. Low-altitude concentrations are very high close to source regions, but further downwind of the continents, vertical mixing takes place and results in more even CO vertical distributions. In regions of significant convection, particularly in the equatorial Indian Ocean, the CO mixing ratio is greater at higher altitudes, indicating vertical transport of biomass burning emissions to the upper troposphere.

Objective To gather information from senior dental students about their future career plans, with particular emphasis on work-life balance issues, their attitudes towards the NHS and retirement plans. Method Senior dental students at the Universities of Dundee and Manchester were asked to complete a voluntary anonymous questionnaire. Results In all 141 questionnaires were completed, 42 by students in Manchester and 114 in Dundee. On qualification nearly all surveyed intend to work full time but after five years one quarter (26%) of females intend to work part time. This is significantly (p < 0.05) different from males where nearly all (98%) intend to work full time. Although the majority (65%) intend to work in general practice significant numbers (19%) wish to have a career in hospital dentistry and very few (3%) in community dentistry. Senior students seem to show no more commitment to the NHS than those in our previous study of dental school applicants. Only 3% intend to work exclusively for the NHS and 18% intend to work exclusively in the private sector. Surprising numbers had plans to retire or go part time before 60 years of age. Only 20% of the sample intended to continue working full time after the age of 60 years. The mode age that those surveyed intended to start a family was 30 years and a large majority of both sexes thought this would interrupt their professional life. More than half of the sample intend to take time out of dentistry until their children attended primary school (female 63%, male 38%) and 6% (female 6%, male 8%) until secondary school. Conclusions Many of our findings suggest that future generations of dentists may have a pattern of professional life that will have the effect of reducing their clinical commitment, although it is not possible to determine how significant an effect this will have on the workforce. It may, however, be appropriate to take career intention into account when workforce planning.

This Study assesses the relation between the year-to-year variability of the semidiurnal tides (SDT) observed at high latitudes of both hemispheres and the global stratospheric stationary planetary wave (SPW) with zonal wavenumber S = 1 (SPW1) derived from the UKMO temperature data. No significant positive correlation can be identified between the interannual variability of the Northern Hemisphere (NH) SDT and the Southern Hemisphere (SH) SPW1 for austral late-winter months. In contrast, a good consistency is evident for the interannual variations between the SDT observed at Rothera (68 degrees S, 68 degrees W) and the Arctic SPW1 for NH mid-winter months. Since it has been observed that during austral summer the non-migrating SDT often plays a significant role at the latitude of Rothera, a physical link between the SH SDT and the NH SPW is suggested. This asymmetry in the interhemispheric link is also noted in a recent study. (C) 2009 Elsevier Ltd. All rights reserved.

Using both thermal infrared (TIR) and near infrared (NIR) channels of MOPITT (Measurements of Pollution in the Troposphere) on EOS-Terra, we demonstrate the first coincident multispectral retrievals of carbon monoxide (CO) from space. Exploiting both TIR and NIR channels has been possible due to recent progress in characterizing NIR channel radiance errors. This has allowed us to trade off sensitivity to near surface CO for larger random errors in the combined retrieval. By examining retrieval diagnostics such as DFS (degrees of freedom for signal) and averaging kernels for the multispectral retrieval (TIR + NIR) as compared to the TIR-only retrieval, we find that adding the NIR channel to the retrieval significantly increases sensitivity to CO, especially near the surface, but with high spatial variability due to surface albedo variations. The cases with the largest increases in DFS are over regions with low thermal contrast between the surface and lower atmosphere. In the tropics (23.4 degrees S-23.4 degrees N), the fraction of daytime land cases with at least 0.4 DFS in the surface layer (surface to 800 hPa) is 20% for TIR-only retrievals compared to 59% for multispectral retrievals. Vertical resolution for the surface layer is also improved, in some cases from around 6 km for TIR-only to roughly 1 km for TIR + NIR. Since we apply a single a priori CO profile (unlike MOPITT V4) and error covariance in all the retrievals reported here, these increases are due solely to the addition of the NIR channel. Enhanced sensitivity to near surface CO is especially evident in a case study for central/east Asia where source regions for urban areas with high population density are clearly identifiable. Although these retrievals are still a research product and require further validation and scientific evaluation, they demonstrate the increased sensitivity to CO in the lowermost troposphere that can be obtained from multispectral MOPITT data.