Showing papers in "Atmosphere-ocean in 2013"
TL;DR: The Canadian Centre for Climate Modelling and Analysis (CCCma) developed the fourth generation of the Canadian Atmospheric Global Climate Model (CanAM4) as discussed by the authors, which includes substantially modified physical parameterizations compared to its predecessor.
Abstract: The Canadian Centre for Climate Modelling and Analysis (CCCma) has developed the fourth generation of the Canadian Atmospheric Global Climate Model (CanAM4). The new model includes substantially modified physical parameterizations compared to its predecessor. In particular, the treatment of clouds, cloud radiative effects, and precipitation has been modified. Aerosol direct and indirect effects are calculated based on a bulk aerosol scheme. Simulation results for present-day global climate are analyzed, with a focus on cloud radiative effects and precipitation. Good overall agreement is found between climatological mean short- and longwave cloud radiative effects and observations from the Clouds and Earth's Radiant Energy System (CERES) experiment. An analysis of the responses of cloud radiative effects to variations in climate will be presented in a companion paper. [Traduit par la redaction] Le Centre canadien de la modelisation et de l'analyse climatique (CCmaC) a mis au point la quatrieme generation d...
329 citations
TL;DR: The Columbia Basin Climate Change Scenarios Project (CBCCSP) as mentioned in this paper is a comprehensive hydrologic database to support climate change planning, impacts assessment, and adaptation in the Pacific Northwest (PNW) by a diverse user community with varying technical capacity over a wide range of spatial scales.
Abstract: The Columbia Basin Climate Change Scenarios Project (CBCCSP) was conceived as a comprehensive hydrologic database to support climate change planning, impacts assessment, and adaptation in the Pacific Northwest (PNW) by a diverse user community with varying technical capacity over a wide range of spatial scales. The study has constructed a state-of-the-art, end-to-end data processing sequence from “raw” climate model output to a suite of hydrologic modelling products that are served to the user community from a web-accessible database. A calibrated 1/16 degree latitude-longitude resolution implementation of the VIC hydrologic model over the Columbia River basin was used to produce historical simulations and 77 future hydrologic projections associated with three different statistical downscaling methods and three future time periods (2020s, 2040s, and 2080s). Key products from the study include summary data for about 300 river locations in the PNW and monthly Geographic Information System products for 21 hy...
133 citations
TL;DR: In this paper, a 3D-Var approach is used to assimilate various types of observations, such as passive microwave satellite data and manually derived ice charts from the Canadian Ice Service (CIS).
Abstract: This paper describes a new regional ice analysis system developed at Environment Canada. It is primarily designed to satisfy the requirements for planning of marine transportation and other marine operations in ice-infested waters around North America, including Canada's two Arctic Metareas; regional sea-ice model initialization; and the needs of regional numerical weather prediction models. A three-dimensional variational approach (3D-Var) is used to assimilate various types of observations. In this first version, only analyses of ice concentration are produced at approximately 5 km resolution using a 6 h persistence forecast from the previous analysis as the background state. The assimilated observations are sea-ice concentrations from two sources of passive microwave satellite data, Advanced Microwave Scanning Radiometer-Earth observing system (AMSR-E) and Special Sensor Microwave/Imager (SSM/I), and manually derived ice charts from the Canadian Ice Service (CIS). Objective verification scores computed...
58 citations
TL;DR: The first thorough examination of oxygen concentrations in Canadian waters of the Pacific Ocean reveals several patterns in space and time as mentioned in this paper, such as sub-surface concentrations of oxygen tend to be lower in shelf waters than in deep-sea waters on the same isopycnal and lower in southern waters of continental shelf than farther north.
Abstract: The first thorough examination of oxygen concentrations in Canadian waters of the Pacific Ocean reveals several patterns in space and time. Sub-surface concentrations of oxygen tend to be lower in shelf waters than in deep-sea waters on the same isopycnal and lower in southern waters of the continental shelf than farther north. The lowest near-bottom concentration was 0.7 ml L−1 (31 μmol kg−1) in mid-shelf waters in summer off southwest Vancouver Island in the Juan de Fuca Eddy region. Oxygen concentration there declined at a rate of 0.019 ml L−1 y−1 (0.83 μmol kg−1 y−1) from 1979 to 2011. This decline is attributed mainly to changes in oxygen concentrations on the same density surfaces, rather than to changes in the depth of constant-density surfaces. A numerical simulation of ocean currents and nutrient concentrations in and surrounding the Juan de Fuca Eddy in summer reveals persistent upwelling into the centre of this eddy and slow bottom currents within the eddy. Upwelled water at bottom of the Juan ...
50 citations
TL;DR: In this paper, the authors tested the ecological resilience and engineering resilience of dams and reservoir management in seven sub-basins of the Columbia River from 1950 to 2011 and found that annual snowmelt runoff peaks in five of seven headwater basins shifted to a few days earlier than predicted.
Abstract: Large river basins transfer the water signal from the atmosphere to the ocean. Climate change is widely expected to alter streamflow and potentially disrupt water management systems. We tested the ecological resilience—capacity of headwater ecosystems to sustain streamflow under climate change—and the engineering resilience—capacity of dam and reservoir management to overprint a climate change signal—in seven sub-basins of the Columbia River from 1950 to 2011. Sub-basins had a headwater gauge above dams with a long-term streamflow record and a nearby climate station with a long-term record of air temperature and precipitation, as well as matching long-term streamflow records at gauges downstream of dams. Trends were fitted to daily data for maximum and minimum temperature, precipitation, and streamflow over the period of record (mostly 1950–2011). Consistent with predicted streamflow response to climate warming, annual snowmelt runoff peaks in five of seven headwater basins shifted to a few days earlier o...
28 citations
TL;DR: In this paper, the impacts of large-scale modes of climate variability on the annual cycle of terrestrial hydrometeorology in the Canadian Columbia River basin were assessed with the aim of updating our current understanding and identifying opportunities for climate-informed, early-season water supply forecasting.
Abstract: The impacts of large-scale modes of climate variability on the annual cycle of terrestrial hydrometeorology in the Canadian Columbia River basin were assessed with the aim of updating our current understanding and identifying opportunities for climate-informed, early-season water supply forecasting. Composite analyses of streamflow from seven Water Survey of Canada gauging stations conditional on El Nino–Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), Pacific/North American pattern (PNA), Arctic Oscillation (AO), and North Pacific Gyre Oscillation (NPGO) states revealed that hydrological impacts of a climate mode could be manifested through changes in the annual runoff volume and/or changes in seasonal runoff patterns. Responses were generally non-linear. Considering ENSO and the PDO, for instance, streamflow anomalies associated with their warm phases contrast with those associated with their cool phases; however, the warm phases tend to produce more consistent streamflow responses than t...
26 citations
TL;DR: In this paper, a reanalysis of trends in water properties around the Gulf of Alaska is presented, and it is shown that though trends have changed, the essential story that was told 15 years ago has not changed in any meaningful way.
Abstract: This paper presents a reanalysis of trends in water properties around the Gulf of Alaska. The datasets used are the lighthouse time series and the Line-P time series augmented with data from the Argo global float array. It is shown that though trends have changed, the essential story that was told 15 years ago has not changed in any meaningful way. Sea-surface temperatures are rising over a large part of the Gulf of Alaska, and sea-surface salinities are declining. Both of these lead to a decrease in surface density. We show that the temperature change extends deep into the Gulf of Alaska, and the freshening trend extends to a depth of about 100 db. Potential energy in the water column is decreasing, and the result of the decreasing potential energy and the increasing stratification implies a decrease in mid-winter mixed layer depths. RESUME [Traduit par la redaction] Cet article presente une reanalyse des tendances des proprietes de l'eau dans le golfe d'Alaska. Les ensembles de donnees utilises sont les...
24 citations
TL;DR: In this article, the authors investigated water resource vulnerability in the US portion of the Columbia River basin (CRB) using multiple indicators representing water supply, water demand, and water quality.
Abstract: We investigated water resource vulnerability in the US portion of the Columbia River basin (CRB) using multiple indicators representing water supply, water demand, and water quality. Based on the US county scale, spatial analysis was conducted using various biophysical and socio-economic indicators that control water vulnerability. Water supply vulnerability and water demand vulnerability exhibited a similar spatial clustering of hotspots in areas where agricultural lands and variability of precipitation were high but dam storage capacity was low. The hotspots of water quality vulnerability were clustered around the main stem of the Columbia River where major population and agricultural centres are located. This multiple equal weight indicator approach confirmed that different drivers were associated with different vulnerability maps in the sub-basins of the CRB. Water quality variables are more important than water supply and water demand variables in the Willamette River basin, whereas water supply and ...
23 citations
TL;DR: In this article, a 20-member ensemble made up of seven global climate models (GCMs) run under three emissions scenarios (A1B, A2, and B1) for three future periods (2020s, 2050s, and 2080s) downscaled using Bias Corrected Spatial Disaggregation and simulated via the spatially distributed Variable Infiltration Capacity (VIC) model.
Abstract: The Canadian portion of the Columbia River basin, or Upper Columbia River basin (UCRB), which is made up of the sub-basins of the Columbia and Kootenay rivers, has a hydrologic regime dominated by snow and glacier melt that makes it particularly susceptible to climate change. To investigate the influence of climate change on the water balance and streamflow of the UCRB, simulations are made for a 20-member ensemble made up of seven global climate models (GCMs) run under three emissions scenarios (A1B, A2, and B1 (with one exception)) for three future periods (2020s, 2050s, and 2080s) downscaled using Bias Corrected Spatial Disaggregation and simulated via the spatially distributed Variable Infiltration Capacity (VIC) model. To maximize the utility of the VIC model, a process-based distributed model, it is calibrated to 24 sub-basins. Snow water equivalent (SWE) decreases at lower elevations primarily in the southern portion of the UCRB and increases progressively at high elevations in the north from the 2...
23 citations
TL;DR: In this article, meteorological and mass balance data collected on the Illecillewaet Glacier were used to develop and constrain a distributed model for glacier melt, based on temperature and absorbed solar radiation.
Abstract: This study characterizes the meteorological parameters influencing glacier runoff and quantifies recent glacier contributions to streamflow in the Illecillewaet River basin, British Columbia. The Illecillewaet is a glacierized catchment that feeds the Columbia River, with terrain, glacial cover, and topographic relief that are typical of Columbia River headwaters basins in southwestern Canada. Meteorological and mass balance data collected on Illecillewaet Glacier are used to develop and constrain a distributed model for glacier melt, based on temperature and absorbed solar radiation. The melt model is applied to all of the glaciers in the Illecillewaet River basin for the summers of 2009 to 2011. Modelled glacier runoff for the three years has an average value of 112 ± 12 × 106 m3, approximately 10% of Illecillewaet River yields for 2009 to 2011. Glaciers contributed 25% to August flows for the three years. On average, 66% of modelled glacial discharge is derived from the seasonal snowpack, with the rema...
22 citations
TL;DR: In this article, simultaneous enhancements of aerosol optical depth and total columns of carbon monoxide (CO), hydrogen cyanide (HCN), and ethane (C2H6) were observed at the Polar Environment Atmospheric Research Laboratory (PEARL, 80.05°N, −86.42°W, 0.61 km above sea level, Eureka, Nunavut, Canada).
Abstract: In August 2010, simultaneous enhancements of aerosol optical depth and total columns of carbon monoxide (CO), hydrogen cyanide (HCN), and ethane (C2H6) were observed at the Polar Environment Atmospheric Research Laboratory (PEARL, 80.05°N, −86.42°W, 0.61 km above sea level, Eureka, Nunavut, Canada). Moderate Resolution Imaging Spectroradiometer (MODIS) hot spots, Ozone Monitoring Instrument (OMI) aerosol index maps, and Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) back-trajectories were used to attribute these enhancements to an intense boreal fire event occurring in Russia. A ground-based Fourier Transform InfraRed (FTIR) spectrometer at PEARL provided vertically integrated measurements of trace gases transported in smoke plumes. We derived HCN and C2H6 equivalent emission ratios with respect to CO of 0.0054 ± 0.0022 and 0.0108 ± 0.0036, respectively, and converted them into equivalent emission factors of 0.66 ± 0.27 g kg−1 and 1.47 ± 0.50 g kg−1 (in grams of gas per kilogram of dry ...
TL;DR: In this article, the authors investigated sea-ice influx events into the Prince Gustaf Adolf Sea during the 2010 mobile-ice season and derived from RADARSAT imagery using the Canadian Ice Service Automated Sea Ice Tracking System (CIS-ASITS) and validated using data from two CIS satellite-tracked beacons.
Abstract: One of the routes for thick, multi-year sea ice (MYI) exiting the Arctic Ocean is through the Queen Elizabeth Islands (QEI) in the Canadian Arctic. Quantifying the volume of MYI that passes through the QEI and the associated transit times is important for assessing changes in Arctic-wide MYI amount. It is also important because MYI eventually invades the Northwest Passage and affects Arctic shipping. One of the main gateways through which Arctic sea ice enters the QEI is the Prince Gustaf Adolf Sea. In this study, sea-ice influx events into the Prince Gustaf Adolf Sea during the 2010 mobile-ice season were investigated. Sea-ice motion was derived from RADARSAT imagery using the Canadian Ice Service-Automated Sea Ice Tracking System (CIS-ASITS) and validated using data from two CIS satellite-tracked beacons. Ice motion results indicate that major ice influxes through the Prince Gustaf Adolf Sea occur as a series of wind-driven pulses and that ice drift rates are approximately 1–2% of the wind speed. During...
TL;DR: In this paper, the authors used the NCEP Global Ocean Data Assimilation System (GODAS) to compare the current variations in the equatorial Pacific between two types of El Nino.
Abstract: Outputs based on the National Centers for Environmental Prediction (NCEP) Global Ocean Data Assimilation System (GODAS) are adopted to contrast the current variations in the equatorial Pacific between two types of El Nino. The model fully resolves the equatorial currents. We found that the central Pacific El Nino (CP-El Nino) corresponds well with previous El Nino studies in that both the eastward Equatorial Undercurrent (EUC) and westward South Equatorial Current (SEC) weaken. On the other hand, the eastern Pacific El Nino (EP-El Nino) displays a distinct circulation pattern. The North Equatorial Countercurrent (NECC) strengthens in the developing phase and persists into the peak of the warm event, whereas the northern branch of the SEC (SECn) also intensifies during the mature phase and lasts for about six months. The South Equatorial Countercurrent (SECC) strengthens during the decaying phase of the EP-El Nino. The shifting of the wind stress curl associated with the thermocline variability is chiefly ...
TL;DR: In this article, the authors focus on two physical processes for waves in shallow waters off the Mackenzie Delta: bottom friction and depth-induced breaking terms, and use field observations of winds and waves, the state-of-the-art Simulating Waves Nearshore (SWAN) model, and reanalysis wind and wave data.
Abstract: This study focuses on two physical processes for waves in shallow waters off the Mackenzie Delta: bottom friction and depth-induced breaking terms. We use field observations of winds and waves, the state-of-the-art Simulating Waves Nearshore (SWAN) model, and reanalysis wind and wave data. The two field observation periods are an August 2008 field experiment, during which in situ field data were collected, and an Arctic storm when data were recorded by buoy measurements from 4 to 6 August 1991. Wind and wave development processes are analyzed during these two periods with comparisons to observed winds and waves. Our analyses show that bottom friction is the main shallow water physical process during the August 2008 field experiment, whereas depth-induced breaking is the dominant shallow water physical process during the 4–6 August 1991 storm, in conjunction with the effects of bottom friction. The SWAN wave model is used to investigate the shallow water physical processes during these two observation peri...
TL;DR: In this article, a high-resolution Canadian lightning climatology is presented, which can be used to assess lightning occurrence and risk for many applications including protection measures for buildings and other stru...
Abstract: A high-resolution Canadian lightning climatology is presented. Generating the high-resolution flash density climatology from a relatively short observation period (approximately 10 years) of the Canadian Lightning Detection Network can be challenging because of the natural variations in the lightning frequency. To address this, an objective methodology was developed with the intended purpose of reducing random variations while still retaining the real spatially significant local variations in the cloud-to-ground lightning flash densities. This technique is applied to the annual 1 km lightning flash density values across most of Canada (south of 60°–70°N) to generate a high-resolution lightning climatology. Lightning flash density maps for selected areas are presented that demonstrate typical patterns resulting from the optimizing methodology. This high-resolution climatology can be used to assess lightning occurrence and risk for many applications including protection measures for buildings and other stru...
TL;DR: In this article, the authors conduct a retrospective study of ozone formation in the Lower Fraser Valley (LFV), using numerical models, observations, and emission inventories in order to understand relationships between reductions in local precursor emissions and episodic ozone concentrations.
Abstract: We conduct a retrospective study of ozone formation in the Lower Fraser Valley (LFV), using numerical models, observations, and emission inventories in order to understand relationships between reductions in local precursor emissions and episodic ozone concentrations. Because there appears to be little or no impact from precursor emissions upwind of the LFV during ozone episodes and because background concentrations of ozone and its precursors are generally from the North Pacific Ocean and quite low, summertime ozone formation in the LFV is mostly caused by local emissions. The observed change in behaviour of ozone formation must, therefore, arise from reductions in local precursor emissions. We exploit the observed changing precursor emission–ozone concentration relationship to perform a dynamical model evaluation. Complicating the analyses are an observed shift in the population patterns within the valley over the last 25 years and a small but documented change in the tropospheric background concentrati...
TL;DR: Results of the verified experiments show that the statistical reliability of ALADIN-LAEF improves when clustering is applied, but no clear improvement can be seen in the skill of LAMEPS, as none of the clustering strategies outperforms any other.
Abstract: One of the main challenges for a skilful Limited Area Model Ensemble Prediction System (LAMEPS) is the generation of appropriate initial perturbations. In most operational LAMEPSs, the initial perturbations are provided by a global Ensemble Prediction System (EPS). Molteni et al. (2001) proposed clustering analysis as an objective selection criterion to choose a member from the global European Centre for Medium-range Weather Forecasts (ECMWF)-EPS model as initial perturbations in LAMEPS. In this article, another strategy for using the clustering method is investigated which ensures that initial perturbations are centred on the control analysis. The main purpose of this article is to study the benefit of cluster analysis and to validate the effect of different clustering strategies on the performance of a 17-member LAMEPS. The system used in this study is the operational Aire Limitee Adaptation Dynamique Developpement InterNational-Limited-Area Ensemble Forecasting (ALADIN-LAEF) model. Three experiments we...
TL;DR: In this paper, a time series of radiometric soundings over Amundsen Gulf in Canada's western maritime Arctic were used to establish the general shape of heat flux convergence (heat accumulation) profiles attributable to mesoscale sensible heat flux from the unconsolidated sea-ice surface.
Abstract: Hourly temperature profile sequences from a time series of radiometric soundings over Amundsen Gulf in Canada's western maritime Arctic were used to establish the general shape of heat flux convergence (heat accumulation) profiles attributable to mesoscale sensible heat flux from the unconsolidated sea-ice surface. This sensible heat flux signature profile was then used to identify 520 similar heat flux convergence profiles in the January–April 2008 period. Only hours with clear skies were included to eliminate heat flux convergence resulting from enhanced downwelling longwave radiation, which often accompanies cloud cover, and heating caused by the phase change of water. The median heat flux convergence profile attributed to sensible heat flux decreased logarithmically with height. The sensible heat flux ranged from near 0 to 183 W m−2; the median was 11.4 W m−2; the average was 21.1 W m−2; the mode was 0.1 W m−2. These sensible heat flux estimates are reliable because they are based on the fundamental p...
TL;DR: The first regional analysis of projected changes in extremes for the Canadian Columbia Basin is presented in this article, which makes use of an ensemble of eight Regional Climate Model simulations from the North American Regional Climate Change Assessment Program.
Abstract: A brief summary of the first regional analysis of projected changes in extremes for the Canadian Columbia Basin is presented. The study makes use of an ensemble of eight Regional Climate Model simulations from the North American Regional Climate Change Assessment Program. First, the regional models’ historical simulations are compared with their coarse-scale driving data as well as with gridded observations. This analysis indicates that the regional models generally improve upon their coarse-resolution forcing, particularly for precipitation. By the middle of the twenty-first century, annual mean temperature in the basin is projected to increase by 1.8°C to 2.7°C compared with the past (1971–2000). A 1% to 9% increase in annual total precipitation is projected. These projections are compared with a wider range of projected changes from a larger ensemble of coarse-scale global climate models. The projected changes to extremes that accompany these changes in mean conditions are considerable. Warm days in su...
TL;DR: In this article, a logarithmic relationship was found between downwelling longwave radiation and atmospheric-column water vapour expressed as precipitable water or mean vapour pressure.
Abstract: Measurements of downwelling longwave radiation and atmospheric-column variables (precipitable water, mean vapour pressure, and mean temperature) derived from microwave radiometric profiles were collected over a composite year at various locations in the Beaufort Sea–Amundsen Gulf region of the Canadian Arctic. Cloud cover was specified by a temporal fractional cloud cover derived from ceilometer measurements. A logarithmic relationship was found between downwelling longwave radiation and atmospheric-column water vapour expressed as precipitable water or mean vapour pressure. This relationship explained about 84% of the variance with a standard error of around 9%. Downwelling longwave radiation was not as well correlated with mean atmospheric temperature. The parameterization of downwelling longwave radiation as a function of atmospheric-column variables, which can be analyzed more accurately than surface variables in data sparse regions, may contribute to improved climate modelling of the western maritime...
TL;DR: In this article, two sets of daily reanalysis data from the National Centers for Environmental Prediction reanalysis version 1 (NCEP-I) and the European Centre for Medium-Range Weather Forecasts 40-year Reanalysis data (ERA-40) were used to calculate the atmospheric diabatic heating effects of the Tibetan Plateau and adjacent regions with an inverse algorithm.
Abstract: Because of a lack of sufficient observations over the Tibetan Plateau (TP), the measurement of the strength of the thermal effects of the TP is a challenging issue, yet of crucial importance for climate research. In this study, two sets of daily reanalysis data (1979–2001) from the National Centers for Environmental Prediction reanalysis version 1 (NCEP-I) and the European Centre for Medium-Range Weather Forecasts 40-year Reanalysis data (ERA-40) are used to calculate the atmospheric diabatic heating effects of the TP and the adjacent regions with an inverse algorithm. The observational data obtained from the recent atmospheric experiments over the TP are applied to verify and evaluate the results from NCEP-I and ERA-40 reanalysis data, respectively. It is found that the ERA-40 results are closer to the observations in terms of the structure and seasonal variation of the vertical profile of the diabatic heating over the TP. The horizontal distributions of the apparent heat source are quite reasonable over...
TL;DR: In this paper, the authors used the Canadian Regional Climate Model (CRCM) to dynamically downscale outputs from the third generation Coupled Global Climate Model for the Gulf of St Lawrence and related coastal areas.
Abstract: This study explores the problem of dynamical downscaling global climate model (GCM) simulations to finer resolution and compares the results with present climate reanalysis data. We use the Canadian Regional Climate Model (CRCM) to dynamically downscale outputs from the third generation Coupled Global Climate Model (CGCM3) for the Gulf of St. Lawrence and related coastal areas. The integration was performed for the 1970–99 tri-decadal period. Three methodologies were used: (DM-1) sea surface temperature (SST) fields and other fields from CGCM3 were used as drivers of the CRCM, (DM-2) CGCM3 SSTs were adjusted based on North American Regional Reanalysis (NARR) data to correct SST climate biases over the ocean, and (DM-3) CGCM3 SSTs were adjusted based on NARR data (as in (DM-2)) and longwave radiation was adjusted to remove biases in the CRCM's land surface temperature. The DM-1 methodology, using SSTs from CGCM3, gives surface temperature estimates that are too cold in summer and too warm in winter and und...
TL;DR: In this paper, the authors investigate the change in the second-order moment of the ENSO before and after a change point detected by a Bayesian change point analysis using both the ARMA-GARCH error model and the GARCH model.
Abstract: The El Nino–Southern Oscillation (ENSO) is by far the most energetic climate signal Any change in ENSO characteristics will have serious consequences for the global climate system This work suggests a different view at the change in ENSO volatility in addition to change in its descriptive statistics The volatility or the conditional variance of ENSO is tested and modelled using both the Autoregressive Moving Average–Generalized Autoregressive Conditional Heteroscedasticity (ARMA-GARCH) error model and the GARCH model, to investigate the change in the short-run and long-run persistency of the second-order moment of ENSO before and after a change point detected by a Bayesian change point analysis Nonparametric tests revealed a significant change in descriptive statistical characteristics such as the mean, the (unconditional) variance, and the probability distribution of ENSO after a change point in 1975 An Engle's test did not show heteroscedasticity in the random process (residuals) of the Sou
TL;DR: In this paper, the authors investigate several facets of the natural carbon cycle of the past 8000 years related to ocean circulation patterns and ice shelf configuration using the University of Victoria Earth System Climate Model (v. 2.9), which includes a representation of the climate system with dynamic vegetation and an interactive carbon cycle.
Abstract: The mechanisms behind the 20 ppm pre-industrial rise in atmospheric CO2 since 6000 BC have been the focus of considerable debate in recent years. Some studies suggest that natural processes, such as a decline in global forests, calcite compensation, and warming ocean temperatures, can explain the increase in CO2. Others have argued that, because the CO2 increase did not occur during previous interglacial periods, it is an indication of an early human influence on the climate. In this paper, we investigate several facets of the natural carbon cycle of the past 8000 years related to ocean circulation patterns and ice shelf configuration using the University of Victoria Earth System Climate Model (v. 2.9), which includes a representation of the climate system with dynamic vegetation and an interactive carbon cycle. The fully simulated earth system for various freely evolving atmospheric carbon scenarios since 6000 BC failed to recreate the observed rise in CO2 and consistently produced a decline in CO2 throu...
TL;DR: The reliability of the data products from the European Centre for Medium-range Weather Forecasts fields mapped to CloudSat profiles (ECMWF-aux) and the Cloud Geometrical Profile from combined Cloud Profiling Radar (CPR) and Cloud Aerosol and Lidar Infrared Pathfinder Satellite Observations (CALIPSO) (GeoProf-lidar) was determined in a polar marine environment by comparing the satellite products with data from ship-based instrumentation as discussed by the authors.
Abstract: The reliability of the data products from the European Centre for Medium-range Weather Forecasts fields mapped to CloudSat profiles (ECMWF-aux) and the Cloud Geometrical Profile from combined Cloud Profiling Radar (CPR) and Cloud Aerosol and Lidar Infrared Pathfinder Satellite Observations (CALIPSO) (GeoProf-lidar) was determined in a polar marine environment by comparing the satellite products with data from ship-based instrumentation. Simultaneous microwave radiometer profiler (MWRP) measurements were compared with CloudSat's ECMWF-aux temperature and absolute humidity profiles from the surface to 10 km. Cloud-base heights from the ceilometer and radiometer were compared with the GeoProf-lidar cloud-base heights which are derived from a combination of CloudSat and CALIPSO data. Temperatures from ECMWF-aux were generally warmer than those measured by the MWRP during all seasons (negative bias). The root mean square (RMS) differences for temperature were greater than one standard deviation of the MWRP and...
TL;DR: A mechanistic exploration of how ozone formation in the Lower Fraser Valley (LFV) has changed over a 20-year (1985-2005) retrospective period was performed using numerical models, observations, and emissions data from four key episodes selected from the 20 year period as discussed by the authors.
Abstract: A mechanistic exploration of how ozone formation in the Lower Fraser Valley (LFV) has changed over a 20-year (1985–2005) retrospective period was performed using numerical models, observations, and emissions data from four key episodes selected from the 20-year period. The motivation for this study was the observed differences in trends in summertime episodic ozone concentrations recorded at various monitoring stations within the valley; stations in the western part of the valley have generally shown a noticeable reduction in episodic ozone concentrations whereas stations in the eastern part of the valley have shown little or no improvement in their maximum 8-hour averaged ozone concentrations. Concurrent with these air quality changes, there has been a well-documented reduction in ozone precursor emissions along with an observed shift in the population patterns within the valley over the 20-year period. Ozone formation for four episodes, encompassing the different meteorological regimes that occur during...
TL;DR: The National Drought Model (NDM) as discussed by the authors is an amalgamation of the atmospheric component of the original Palmer Drought and Versatile Soil Moisture Budget (VSMB) models.
Abstract: The National Drought Model (NDM) is an amalgamation of the atmospheric component of the original Palmer Drought and Versatile Soil Moisture Budget (VSMB) models. The NDM uses locally derived coefficients from the station or gridded climate data to calculate a calibration factor for comparing locations in time and space. A modular approach is used to model major processes such as evapotranspiration, biometeorological time, snowmelt, and the cascading of soil moisture down to the root zone. The modular approach allows modifications to be made to specific sections without making structural changes to the entire model or the data inputs. The NDM is an operational tool, integrating data from the climate, soil, and plant sciences to monitor agroclimatic risks such as drought and excess moisture. In this paper, the capacity of the NDM to monitor extreme agroclimatic risks, such as drought and flooding of agricultural soils, was assessed. Using the Palmer Drought Severity Index component of the NDM, the m...
TL;DR: In this article, the authors defined the warming period as the interval between the dates of the temperature minimum and the temperature maximum, and used the 40-year reanalysis dataset from the European Center for Medium-range Weather Forecasts (ERA40) and the European Centre Hamburg Model (ECHAM5) simulations to investigate the global distribution of the length and mid-point of the warm period for the present climate (1958-2001) and under global warming (Intergovernmental Panel on Climate Change, Fourth Assessment Report, Special Report o...
Abstract: The mechanism of climate change involves not only an increase in surface temperature but also an adjustment of the global seasons through changes in the timing of the annual temperature cycle. By locating the temperature extrema in monthly temperature records using Lagrangian interpolation in regions where a single maximum and minimum occurs, we define the warming period as the interval between the dates of the temperature minimum and the temperature maximum. The length and mid-point of the warming period are objective measures which can be computed from reanalysis data and from climate model predictions. We have used the 40-year reanalysis dataset from the European Centre for Medium-range Weather Forecasts (ERA40) and the European Centre Hamburg Model (ECHAM5) simulations to investigate the global distribution of the length and mid-point of the warming period for the present climate (1958–2001) and under global warming (Intergovernmental Panel on Climate Change, Fourth Assessment Report, Special Report o...
TL;DR: In this article, the relationship between cloud-to-ground (CG) lightning and convective precipitation across Canada is examined, and a database of coincident 6-hourly rain-gauge and lightning data, constructed from 64 weather stations spanning Canada's ecozones, from April to October 1999 to 2003, was used to calculate rainfall yields (defined as the ratio of the total volume of precipitation to the total CG flash count, in units of kilograms per flash (kg−1)).
Abstract: The relationship between cloud-to-ground (CG) lightning and convective precipitation across Canada is examined. A database of coincident 6-hourly rain-gauge and lightning data, constructed from 64 weather stations spanning Canada's ecozones, from April to October 1999 to 2003, was used to calculate rainfall yields (defined as the ratio of the total volume of precipitation to the total CG flash count, in units of kilograms per flash (kg fl−1)). Warm season rain yields have been found to vary between 1.06 × 108 kg fl−1 and 21.8 × 108 kg fl−1 over the ecozones of eastern Canada and between 1.05 × 108 kg fl−1 and 41.5 × 108 kg fl−1 over western ecozones. The rainfall yields derived from station data were used to predict convective precipitation in 2004 and 2010. Overall, the warm season correlation coefficients between predicted and gauge-measured precipitation were 0.65 and 0.77 for 2004 and 2010, respectively, and 0.71 for both years combined. Regional differences reflecting the complexity of convective act...
TL;DR: In this article, the authors used radiometric vapour density (absolute humidity) profiles over the unconsolidated sea-ice surface of Amundsen Gulf in Canada's western maritime Arctic and the moisture continuity equation to determine hourly latent heat flux convergence and divergence profiles from January to April 2008.
Abstract: Microwave radiometric vapour density (absolute humidity) profiles over the unconsolidated sea-ice surface of Amundsen Gulf in Canada's western maritime Arctic and the moisture continuity equation were used to determine hourly latent heat flux convergence and divergence profiles from January to April 2008. Only hours with clear skies were included to eliminate moistening or drying as a result of the phase change of water. For 273 hours, latent heat flux convergence in the lower atmospheric boundary layer (ABL) was attributed to mesoscale upward latent heat flux at the surface; for 318 hours, latent heat flux divergence in the lower ABL was attributed to downward latent heat flux. The frequency distribution of latent heat flux values, determined by the integral profile method, was approximately normal; flux values ranged from −29.9 to +28.5 W m−2; the median was −0.4; the mean was −0.3, and the mode was +0.4 W m−2. It was concluded that, at the mesoscale, latent heat flux is a minor component of the surface...