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Atmospheric Research (atmospheric + research)
Selected AbstractsSimple statistical structure in time series for daily air flow characteristicsENVIRONMETRICS, Issue 1 2008Piia Post Abstract The structure function is used for quantifying of non-stationarity in time series for certain daily air flow characteristics (DAFC). The National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis 30 year (1968,97) dataset given over 5°,×,10° latitude longitude grid is used to calculate the DAFC series for the Baltic Sea region. The quantification on the basis of the Hurst exponent H enables us to discriminate between the strong synoptic scale non-stationarity and a mild large-scale one. Presented examples show that the change of H is accompanied by a change of the distribution for the series' increments. Long-range increments for various DAFC appear to be approximately normally distributed with approximately constant variance independent of the increment length over a remarkably wide range. The property might be useful in describing a long-range variability of the air flow characteristics. Copyright © 2007 John Wiley & Sons, Ltd. [source] Estimating monthly surface winds for Scania, southern Sweden, using geostrophic wind (1899,1997)GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 2 2002Marie Ekström Wind direction conditions during the 20th century in Scania, southern Sweden, are investigated using an estimated series of monthly wind vector components (east,west u component and north,south v component). The series is developed from a regression relationship between pairwise (1973 to 1997) monthly averages of 10,m surface wind from Scania and a monthly geostrophic wind, based on mean sea level (MSL) pressure data from the National Center of Atmospheric Research (NCAR). The wind conditions during the 20th century are dominated by winds from southwesterly and westerly directions, particularly during summer and autumn. From the 1980s onwards, increased frequencies of westerly winds are evident in spring and summer; however, similarly large frequencies of westerly winds are also found during the early part of the 20th century. Analysis of the estimated wind series indicates large variation in wind direction during the investigated time period, particularly during 1930 to 1960 when large increases of easterly winds are evident in spring. Increased frequencies of easterly winds were also found in other months during this period but not to the same extent as during the spring season. Thus, the presence of periods with quite different wind characteristics suggests that the overall atmospheric circulation has experienced some shifts in this region during the 20th century. [source] Effect of late 1970's climate shift on tropospheric biennial oscillation,role of local Indian Ocean processes on Asian summer monsoonINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 4 2010Prasanth A Pillai Abstract The tropical climate has undergone noticeable changes on interdecadal time scales. The climate shift that occurred in the late 1970s attained enormous attention owing to its global-scale variations in ocean temperature, heat content and El Nino Southern Oscillation (ENSO) properties. Earlier studies presented the effect of this shift on ENSO and the Asian summer monsoon,ENSO relationship. The present study is an attempt to investigate the effect of late 1970's climate shift on tropospheric biennial oscillation (TBO), which is an important tropical phenomenon that includes both air,sea processes in the tropical Indian and Pacific Ocean regions. TBO is the tendency for the Asian,Australian monsoon system to alternate between relatively strong and weak years. The study comprises a detailed analysis of the TBO cycle in the time periods before (1951,1975) and after (1978,2002) the climate shift in 1976 with the help of National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) data sets of 200-hPa velocity potential; the Indian Ocean sea surface temperature (SST) and circulation are more obvious after the shift, although they were significant in the Pacific Ocean before 1976. The effect of ENSO in the biennial cycle is reduced with climate shift. The persistence of Asian-to-Australian summer monsoon has weakened in recent decades, as it is controlled by ENSO. Local oceanic processes in the Indian Ocean and local monsoon Hadley circulation have an increased role in the biennial oscillation of the Asian summer monsoon after 1976. Copyright © 2009 Royal Meteorological Society [source] The spatial pattern of summertime subtropical anticyclones over Asia and Africa: A climatological reviewINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 2 2010Azar Zarrin Abstract The National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) monthly mean reanalysis dataset has been used to analyze spatial variations of summertime subtropical anticyclones over the Asia,Africa region. The geopotential height and zonal wind components of 1000, 500, 200, and 100 hPa in a 30-year period (1971,2000) have been used to determine the spatial and temporal variations of the anticyclone centres, their monthly frequency and latitudinal axis variations during April,October. The results revealed that there is a clear difference in the location of the summer anticyclone centres in lower, middle and upper levels of the troposphere. In the lower levels, the Azores subtropical anticyclone is located at the east of North Atlantic. In the middle levels, the frequencies of anticyclone centre are concentrated over the northwest of Africa, Arabian Peninsula and Iranian Plateau. In the upper troposphere, the geographical location of the anticyclone centres and their frequencies in the summer season exhibit a scattered pattern from south of China up to western Iran at 200 hPa, and a bimodal pattern over the Tibetan and the Iranian Plateaus at 100 hPa. In fact, in the entire study domain, the Iranian Plateau is a preferable location of the middle and upper troposphere anticyclones. The highest observed latitude of the subtropical anticyclone at 100, 200 and 500 hPa levels have been seen over north of Tibetan plateau, a large area from east to west of Asia and Iran during August, July,August and July, respectively. The maximum monthly variation in the latitude of the ridgeline is seen at 500, 200, and 100 hPa from June to July which goes even up to 10 degrees at some longitudes. Copyright © 2009 Royal Meteorological Society [source] Global atmospheric energetics from NCEP,Reanalysis 2 and ECMWF,ERA40 ReanalysisINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 2 2009Carlos A. F. Marques Abstract The global atmospheric energy cycle is estimated on an annual basis using Reanalysis 2 data from the National Centers for Environmental Prediction and National Center for Atmospheric Research (NCEP/NCAR), and ERA 40 Reanalyses from the European Centre for Medium-Range Weather Forecasts (ECMWF) for the period 1979,2001. A formalism to avoid belowground data on pressure levels intercepted by topography is adopted. No appreciable differences were found between the two datasets from the energetics point of view. The so-called ,, and v·grad z formulations were both used for the conversions from zonal available potential energy into zonal kinetic energy (CZ) and from eddy available potential energy into eddy kinetic energy (CE). Results with both formulations are comparable only when using the formalism preventing belowground data to enter into the computations. Atmospheric energetics are also computed using ECMWF Reanalyses for the period 1958,1978. A significant increase was found in the eddy kinetic and eddy available potential energies from the early period to the later period, likely related to the assimilation in the reanalyses of satellite data after 1979. The conversion rate, CZ, was found to change its sign throughout the years. The atmospheric energy cycle using the ECMWF Reanalyses data is compared with five previous estimates. Differences in the direction of the conversion rate, CZ, between the various estimates may be explained by the different time periods chosen for averaging. Owing to the omission of belowground data, the conversion from zonal available potential energy into eddy available potential energy (CA) was somewhat smaller in ECMWF Reanalyses than in the previous estimates. Despite those differences, an overall agreement may be found between the various estimates for the atmospheric energy cycle. Copyright © 2008 Royal Meteorological Society [source] Interannual variability of atmospheric water balance over South Peninsular India and Sri Lanka during northeast monsoon seasonINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 15 2008Venkatraman Prasanna Abstract In this study we have investigated atmospheric water balance over South Peninsular India and Sri Lanka during the months October to December (OND) using computed moisture convergence (C) and residual evaporation (E) from National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data and Global Precipitation and Climatology Project (GPCP) precipitation data. The interannual signatures of OND precipitation, moisture convergence and evaporation over the South Peninsular India and Sri Lanka have been captured. The spatial and temporal characteristics of the hydrological cycle and the contribution of evaporation (E) and convergence (C) to precipitation (P) are discussed in detail. Over the South Peninsular India and Sri Lanka, evaporation (E) dominates during the entire monsoon months (OND). However, the interannual variability of precipitation over the domain is not necessarily influenced by the same criteria which influences the mean seasonal precipitation. The moisture from the Indian Ocean (IO) sector also modulates the precipitation over this region on a year-to-year basis. It has been noted that the positive northeast monsoon rainfall (NEMR) is associated with El Nino coupled with IO dipole, but negative NEMR is weakly associated only with La Nina over South Peninsular India and Sri Lanka. There also exists a significant land-atmospheric interaction over the region in modulating the hydrological cycle on a year-to-year basis. Copyright © 2008 Royal Meteorological Society [source] Intercomparison of global cloud cover fields over oceans from the VOS observations and NCEP/NCAR reanalysisINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 13 2007Ernst Bedacht Abstract The paper inter-compares the total cloud cover over the World Ocean from marine visual observations assimilated in the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) and National Centers of Environmental Prediction/National Center of Atmospheric Research (NCEP-NCAR) reanalysis. The Intercomparison covers the period from 1948 to 2002. NCEP-NCAR reanalysis shows about 10% of fractional cloud cover smaller than the visual observations do. The largest differences are observed in the mid and sub-polar latitudes. In the tropics, NCEP-NCAR data show slightly higher cloud cover then ICOADS. These systematic differences are quite persistent through the year with somewhat stronger differences in summer. Comparison of the characteristics of inter-annual variability shows little consistency between visually observed total cloud cover and total cloudiness diagnosed by the reanalysis. Linear trends are primarily positive in the ICOADS cloud data, while in the NCEP-NCAR reanalysis they show downward trends in the tropics and upward tendencies in the mid and high latitudes. Analysis of the effect of sampling in ICOADS shows that sampling inhomogeneity cannot fully explain the disagreements observed. At the same time, the major climate variability patterns such as North Atlantic Oscillation (NAO) and El-Nino,Southern Oscillation (ENSO) are well captured in both ICOADS and NCEP-NCAR cloud cover data sets. Copyright © 2007 Royal Meteorological Society [source] Trends in storminess over the Netherlands, 1962,2002INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 10 2005A. Smits Abstract Trends in the annual number of independent wind events over the Netherlands are studied for the period 1962,2002. The events are selected out of 13 hourly 10 m wind speed records that are part of a high quality dataset of near-surface wind observations at Dutch meteorological stations. Comparisons are made with trends in independent wind events selected from geostrophic wind speed records and reanalysis data. The results for moderate wind events (that occur on average 10 times per year) and strong wind events (that occur on average twice a year) indicate a decrease in storminess over the Netherlands between 5 and 10%/decade. This result is inconsistent with National Centers for Environmental Prediction,National Center for Atmospheric Research or European Centre for Medium-Range Weather Forecasts reanalysis data, which suggest increased storminess during the same 41 year period. Possible explanations are given for the discrepancy between the trends in storminess based on station data and the trends in storminess based on reanalysis data. Evaluation of trends in geostrophic wind, both from station data and reanalysis data, and evaluation of trends in vector-averaged (upscaled) 10 m wind over the Netherlands point towards inhomogeneities in the reanalysis data as the main cause of the discrepancy. We conclude that it is likely that the decrease in storminess observed in Dutch station records of near-surface wind in the past four decades is closer to reality than the increase suggested by the reanalysis data. Copyright © 2005 Royal Meteorological Society. [source] The impact of non-stationarities in the climate system on the definition of ,a normal wind year': a case study from the BalticINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 6 2005S. C. Pryor Abstract Wind speeds over the Baltic significantly increased over the second half of the 20th century (C20th), with the majority of the increase being focused on the upper quartile of the wind speed distribution and in the southwest of the region. These changes have potentially profound implications for the wind energy resource. For example, based on the National Centers for Environmental Prediction,National Center for Atmospheric Research (NCEP,NCAR) reanalysis data it is shown that, owing to this non-stationarity, using the normalization period of 1987,98 to determine the wind resource (as in the Danish wind index) leads to overestimation of the wind energy index (and hence the wind energy resource) in western Denmark relative to 1958,2001 by approximately 10%. To address whether the increased prevalence of high wind speeds at the end of the C20th will be maintained in the future, we provide a first prognosis of annual wind indices from the HadCM3 coupled atmosphere,ocean general circulation model. The results suggest the 21st century (C21st) will be similar to the 1958,2001 period with respect to the wind energy density, but that the northeastern Baltic will exhibit slightly higher wind energy indices over the course of the C21st relative to the latter half of the C20th, whereas the southwest of the Baltic exhibits some evidence of declining wind indices towards the end of the C21st. These changes may indicate a tendency in HadCM3 towards more northerly tracking of mid-latitude cyclones in the future, possibly due to evolution of the North Atlantic oscillation. As a caveat to this finding, it should be noted that the NCEP,NCAR and European Centre for Medium-Range Weather Forecasts reanalysis data sets and HadCM3 simulations, although exhibiting commonalities during the period of overlap, differ quantitatively in terms of the spatial fields and empirical cumulative probability distributions at individual grid cells. Copyright © 2005 Royal Meteorological Society [source] Onset characteristics of the southwest monsoon over IndiaINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 2 2005P. V. S. Raju Abstract Dynamic and thermodynamic characteristics of the Asian summer monsoon during the onset phase over the Indian Peninsula (Kerala coast) and its variability are examined with reanalysis data sets. For this study, daily averaged (0000 and 1200 UTC) reanalysis data sets of National Centre for Environmental Prediction,National Centre for Atmospheric Research for the period 1948,99 are used. Based on 52 years of onset dates of the Indian summer monsoon, we categorized pre-onset, onset and post-onset periods (each averaged 5 days) to investigate the mean circulation characteristics and the large-scale energetics of the Asian summer monsoon. It is found that the strength of the low-level Somali jet and upper tropospheric tropical easterly jet increase rapidly during the time of evolution of the summer monsoon over India. Over the Bay of Bengal and the Arabian Sea, predominant changes are noticed in the large-scale balances of kinetic energy, heat and moisture from the pre-onset to the post-onset periods. Prior to the onset of the summer monsoon over India, a zone of flux convergence of heat and moisture is noticed over the eastern sector of the Bay of Bengal and this intensifies in the onset and post-onset periods. During onset of the monsoon over India, the horizontal flux convergence of heat and moisture, as well as diabatic heating, are enhanced over the Arabian Sea. These subsequently increase with the evolution and advancement of the monsoon over India. Further, the dynamics of the evolution processes (15 days before and 30 days after the onset date of the monsoon over Kerala for each annual cycle) are studied over various sectors, such as the Arabian Sea, Bay of Bengal and Indian Peninsula region. The study reveals that the low-level kinetic energy, vertically integrated generation of kinetic energy and net tropospheric moisture over Arabian Sea can be used as potential predictors for the prediction of the possible onset date of the summer monsoon over the Indian Peninsula. Copyright © 2005 Royal Meteorological Society [source] In search of zonal circulations in the equatorial Atlantic sector from the NCEP,NCAR reanalysisINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 1 2001Stefan Hastenrath Abstract The National Center for Environmental Prediction,National Center for Atmospheric Research (NCEP,NCAR) 1958,1997 upper-air dataset has been evaluated for evidence of equatorial zonal circulation cells over the Atlantic and adjacent continents. For January, April, July and October, maps are presented of mid-tropospheric vertical motion, upper-tropospheric divergent flow, and zonal,vertical cross-sections of vertical and divergent zonal motion and total zonal flow. In the boreal winter half-year, a centre of intense ascending motion and upper-tropospheric, mainly northward-directed outflow is located off the mouth of the Amazon. From this centre there is also some outflow into centres of upper-tropospheric convergence and subsidence over the equatorial eastern Pacific and eastern Atlantic, respectively. From January to April, the near-equatorial band of ascending motion shifts southward, and the upper-tropospheric convergence centre is displaced from the Equator into the South Atlantic. In the boreal summer half-year, the band of strongest ascending motion is displaced northward, and two separate centres of upper-tropospheric divergent outflow are found over northern hemispheric Africa and the Central American Seas. From these centres, the outflow is directed approximately southward into the southern hemisphere. The analysis points to the existence of an equatorial zonal circulation cell in the Atlantic sector confined to around January. Copyright © 2001 Royal Meteorological Society [source] Impact of horizontal model resolution and orography on the simulation of a western disturbance and its associated precipitationMETEOROLOGICAL APPLICATIONS, Issue 2 2004A. P. Dimri A nonhydrostatic version of Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR) Mesoscale Model (MM5) is used to study the effects of the horizontal model resolution and orography while simulating an active western disturbance (WD) that affected northwest India from 21 to 25 January 1999. Two numerical experiments are conducted with six combinations of two factors: horizontal model resolution and topography. National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysed data are used for the initial and boundary conditions. Simulation results indicate that the distribution and the rate of simulated precipitation due to a WD over northwest India is highly sensitive to the horizontal model resolution and topography. The model with finer resolution (30 km) is better able to estimate effects of mesoscale forcing on precipitation over the selected domain. The amount of precipitation simulated over the coarse domain is much less than the observed precipitation owing to the model's unrealistic representation of orographic effects and mesoscale forcing. Simulated terrain, vertical velocity, wind and streamline at different horizontal model resolutions are presented. The detailed structure and distribution of wind speed are simulated in the finer domain. Simulated vertical velocity and precipitation are less in the second experiment when a flat topography is used across the domain, which indicates that topography plays a significant role in modulating the WD. Sensitivity of the horizontal model resolution for precipitation is assessed and it is found that the finer domain of the model simulation gives better results. Copyright © 2004 Royal Meteorological Society. [source] The ERA-40 re-analysisTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 612 2005S. M. Uppala Abstract ERA-40 is a re-analysis of meteorological observations from September 1957 to August 2002 produced by the European Centre for Medium-Range Weather Forecasts (ECMWF) in collaboration with many institutions. The observing system changed considerably over this re-analysis period, with assimilable data provided by a succession of satellite-borne instruments from the 1970s onwards, supplemented by increasing numbers of observations from aircraft, ocean-buoys and other surface platforms, but with a declining number of radiosonde ascents since the late 1980s. The observations used in ERA-40 were accumulated from many sources. The first part of this paper describes the data acquisition and the principal changes in data type and coverage over the period. It also describes the data assimilation system used for ERA-40. This benefited from many of the changes introduced into operational forecasting since the mid-1990s, when the systems used for the 15-year ECMWF re-analysis (ERA-15) and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) re-analysis were implemented. Several of the improvements are discussed. General aspects of the production of the analyses are also summarized. A number of results indicative of the overall performance of the data assimilation system, and implicitly of the observing system, are presented and discussed. The comparison of background (short-range) forecasts and analyses with observations, the consistency of the global mass budget, the magnitude of differences between analysis and background fields and the accuracy of medium-range forecasts run from the ERA-40 analyses are illustrated. Several results demonstrate the marked improvement that was made to the observing system for the southern hemisphere in the 1970s, particularly towards the end of the decade. In contrast, the synoptic quality of the analysis for the northern hemisphere is sufficient to provide forecasts that remain skilful well into the medium range for all years. Two particular problems are also examined: excessive precipitation over tropical oceans and a too strong Brewer-Dobson circulation, both of which are pronounced in later years. Several other aspects of the quality of the re-analyses revealed by monitoring and validation studies are summarized. Expectations that the ,second-generation' ERA-40 re-analysis would provide products that are better than those from the firstgeneration ERA-15 and NCEP/NCAR re-analyses are found to have been met in most cases. © Royal Meteorological Society, 2005. The contributions of N. A. Rayner and R. W. Saunders are Crown copyright. [source] Data assimilation of high-density observations.THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 605 2005I: Impact on initial conditions for the MAP/SOP IOP2b Abstract An attempt is made to evaluate the impact of the data assimilation of high-frequency data on the initial conditions. The data assimilation of all the data available on the Mesoscale Alpine Program archive for a test case is performed using the objective analysis and the Variational Data Assimilation (Var) techniques. The objective analysis is performed using two different schemes: Cressman and multiquadric; 3D-Var is used for the variational analysis. The European Centre for Medium-Range Weather Forecasts analyses are used as first guess, and they are blended together with the observations to generate an improved set of mesoscale initial and boundary conditions for the Intensive Observing Period 2b (17,21 September 1999). A few experiments are performed using the initialization procedure of MM5, the mesoscale model from Penn State University/National Center for Atmospheric Research. The comparison between improved initial conditions and observations shows: (i) the assimilation of the surface and upper-air data has a large positive impact on the initial conditions depending on the technique used for the objective analysis; (ii) a large decrease of the error for the meridional component of the wind V at the initial time is found, if assimilation of three-hourly data is performed by objective analysis; (iii) a comparable improvement of the initial conditions with respect to the objective analysis is found if 3D-Var is used, but a large error is obtained for the V component of the wind. Copyright © 2005 Royal Meteorological Society [source] Data assimilation of high-density observations.THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 605 2005II: Impact on the forecast of the precipitation for the MAP/SOP IOP2b Abstract The impact of the data assimilation of high-density (space and time) data on the precipitation forecast is evaluated by improving the initial conditions of a mesoscale model. The high-frequency data allow for improving the three-hourly initial and boundary conditions as well. The data assimilation is performed using initial objective analysis (Cressman and multiquadric schemes) and 3D-Var. The MM5 (version 3) mesoscale model from Penn State University/National Center for Atmospheric Research is used to evaluate the impact of the improved initial and boundary conditions on the model simulations. The comparison of model results with observations shows: (i) the forecast of the precipitation at high resolution produces better results than those without data assimilation only if three-hourly data are assimilated by multiquadric; (ii) the mean error of the model rainfall largely decreases only if 3D-Var is used, but no comparable improvement in the spatial distribution of the precipitation is found; (iii) the improvement for the rainfall is not as good as it is for the initial conditions for all experiments. Moreover, the observations ingested by objective analysis modify both the amount and the timing of the precipitation on the Po valley. On the other hand, 3D-Var modifies only the amount of the precipitation, but both techniques barely recover large-model failure. Copyright © 2005 Royal Meteorological Society [source] Comparison of 850-hPa relative humidity between ERA-40 and NCEP/NCAR re-analyses: detection of suspicious data in ERA-40ATMOSPHERIC SCIENCE LETTERS, Issue 1 2009Aurélien Ben Daoud Abstract An exploratory study is performed on the 850-hPa relative humidity data (RH850) extracted from the Re-Analysis Project (ERA-40) and National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) re-analyses covering a domain centred on western Europe (60°W,60°E, 15°N,75°N). The largest deviations between the two data archives are observed over the North Atlantic Ocean. In addition, unrealistic values of RH850 are detected in the ERA-40 re-analysis at resolutions of both 2.5° and 1.125°. There is no strong correlation between RH850 provided by ERA-40 and observations from radio sounding stations, thus ruling out a straightforward correction of the detected anomalous values. Copyright © 2009 Royal Meteorological Society [source] Methods to adjust for the interference of N2O on ,13C and ,18O measurements of CO2 from soil mineralization,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2005D. Beheydt In this paper we present an overview of the present knowledge relating to methods that avoid interference of N2O on ,13C and ,18O measurements of CO2. The main focus of research to date has been on atmospheric samples. However, N2O is predominantly generated by soil processes. Isotope analyses related to soil trace gas emissions are often performed with continuous flow isotope ratio mass spectrometers, which do not necessarily have the high precision needed for atmospheric research. However, it was shown by using laboratory and field samples that a correction to obtain reliable ,13C and ,18O values is also required for a commercial continuous flow isotope ratio mass spectrometer. The capillary gas chromatography column of the original equipment was changed to a packed Porapak Q column. This adaptation resulted in an improved accuracy and precision of ,13C (standard deviationGhent: from 0.2 to 0.08,; standard deviationLincoln: from 0.2 to 0.13,) of CO2 for N2O/CO2 ratios up to 0.1. For ,18O there was an improvement for the standard deviation measured at Ghent University (0.13 to 0.08,) but not for the measurements at Lincoln University (0.08 to 0.23,). The benefits of using the packed Porapak Q column compared with the theoretical correction method meant that samples were not limited to small N2O concentrations, they did not require an extra N2O concentration measurement, and measurements were independent of the variable isotopic composition of N2O from soil. Copyright © 2005 John Wiley & Sons, Ltd. [source] | ||||||||||