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The NRC Atmospheric Research Aircraft
Abstract
The Flight Research Laboratory of the National Research Council of Canada has an active program of airborne atmospheric research that has been realized primarily in collaboration with other Canadian, as well as American, agencies. The current focus is on global change science, aircraft icing and airborne remote sensing system development. Over the past 50 years, research has been conducted on a diverse array of science and technology issues, driven by contemporary aerospace concerns and, more generally, national and societal needs of the day. The Laboratory's initial efforts in airborne atmospheric science started in 1953, and included work in helicopter icing, work in aircraft structural integrity under turbulent conditions, as well as studies to characterize atmospheric turbulence in general. Presently, projects in the realm of airborne atmospheric science have been organized around the Twin Otter and the Convair 580 aircraft. In recent years, these aircraft have been developed to support research efforts in aircraft icing (Convair 580), air quality and global change science (Twin Otter), as well as remote sensing of the atmosphere and the Earth (both the Convair 580 and the Twin Otter). A particular strength is the precise measurement of atmospheric motion - which, in turn, permits a well-regarded capability in airborne flux measurement (the measurement of the total vertical flow of a quantity of interest, i.e., water vapour or heat). This paper includes brief summaries of the flight envelopes and the instrumentation on-board the Twin Otter and Convair 580 when configured for atmospheric research. The variety and application of the data collected by these aircraft are demonstrated with examples from several recent experiments.
... (2) Penjelasan Undang-Undang Nomor 23 Tahun 1992 tentang Kesehatan telah mengamanatkan antara lain, setiap tempat kerja harus melaksanakan upaya kesehatan kerja, agar tidak terjadi gangguan kesehatan pada pekerja, keluarga, masyarakat dan lingkungan disekitarnya. (3) Berdasarkan data dari International Labour Organization (ILO), pada tahun 2018 mencatat angka kematian yang diakibatkan karena kecelakaan kerja dan Penyakit Akibat Kerja (PAK) sebanyak 2,5 juta kasus setiap tahun. Sedangkan data pada tahun 2019, disebutkan bahwa setiap 10 detik terdapat 1 tenaga kerja yang meninggal dunia akibat kecelakaan kerja dan 160 tenaga kerja mengalami sakit akibat kerja. ...
Standard operating procedure atau biasa disingkat SOP merupakan panduan untuk memastikan kegiatan operasional organisasi atau perusahaan berjalan dengan lancar. Penggunaan SOP dalam organisasi bertujuan untuk memastikan organisasi beroperasi secara konsisten, efektif, efisien, sistematis dan terkelola dengan baik, untuk menghasilkan produk yang memiliki mutu konsisten sesuai dengan standar yang telah ditetapkan. Penelitian ini bertujuan untuk mengetahui hubungan sikap pekerja terhadap penerapan standar operasional prosesur dengan kejadian penyakit akibat kerja dan produktivitas kerja pada pekerja di PT. Pelindo (Persero) Regional IV Cabang Makassar New Port Tahun 2022.Jenis penelitian ini menggunakan kuantitatif dengan rancangan cross sectional study. Teknik pengambilan sampel dengan menggunakan total sampling dengan jumlah 77 responden. Data diperoleh dengan menggunakan kuesioner. Data dianalisis dengan uji chi-square pada tingkat kepercayaan 95% (alpha=0.05). Dari hasil penelitian diperoleh bahwa tidak ada hubungan antara sikap pekerja terhadap penerapan Standar Operasional Prosedur (SOP) dengan kejadian Penyakit Akibat Kerja (PAK) diperoleh bahwa nilai p value=0.919>0.05 dan ada hubungan antara sikap pekerja terhadap penerapan Standar Operasional Prosedur (SOP) dengan produktivitas kerja yang sangat baik diperoleh bahwa nilai p value=0.001<0.05 di PT. Pelindo (Persero) Regional IV Cabang Makassar New Port Tahun 2022.Penelitian ini menyarankan agar pekerja lebih meningkatkan sikap patuh terhadap prosedur untuk menjaga kesehatan dan keselamatan diri, memberlakukan sistem hukuman bagi pekerja yang bekerja tidak sesuai dengan prosedur, karena bekerja sesuai dengan prosedur akan membuat pekerjaan lebih cepat dan singkat dalam mecapai target perusahaan.
... The data for this study were measured on board of the Twin Otter research aircraft (MacPherson et al., 2001) of the Canadian National Research Council (NRC) along a 115 km transect in May of 1994 as part of the BOREAS (Boreal Ecosystem -Atmosphere Study). The Twin Otter was equipped to measure fluctuations of wind, temperature, water vapor, CO2 and O3 at a frequency of 16 Hz (MacPherson, 1996). ...
During the late 1980s, it became obvious that the
energy balance at the earth’s surface could not be
closed with experimental data (Desjardins, 1985; Chahuneau
et al., 1989). The available energy, i.e. the sum
of the net radiation (-Qs*) and the ground heat flux (QG)
-Qs* - Qg = Qh + Qe , (1)
was found in most cases to be larger than the sum of
the turbulent fluxes of sensible (QH) and latent (QE)
heat. For example, Aubinet et al. (2000) conclude that
the energy balance tends to be more or less unclosed,
an indication that non-vertical or non-turbulent fluxes
need to be incorporated in the budget calculation, or
that there are substantial errors in other energy flux
terms which lead to an underestimation of available energy
fluxes. In a review of 11 published articles, the sum
of convective energy fluxes was found to be 89% of
available energy (Sakai et al., 2001). A general lack of
energy balance closure was also found in another
study about 20 FLUXNET sites (Wilson et al., 2002).
The mean imbalance was in the order of 20%.
Eddy covariance measurements are widely used to
study the atmosphere-biosphere exchange. However,
there are some issues that must be resolved. One of
them is that complete energy balance closure is usually
not achieved even during the daytime when measurement
conditions are usually favorable. We believe that
transport in eddies that cannot be captured by common
averaging times of 30 min to 60 min can explain a major
part of this systematic underestimation. We propose
applying spatial averaging over long enough distances
in order to minimize this underestimation. An advantage
of spatial averaging is that it can resolve quasistationary
circulations, which is almost impossible for
flux computations based on temporal averaging.
... The NRC Twin Otter is a research aircraft with a well established instrumentation platform for air quality research (e.g. Banic et al. 1996;Leaitch et al. 1996;MacPherson et al. 2001;Banic et al. 2003). In addition to the instrumentation list given here, it carries a full fast-response (1 s or less) package to determine meteorological parameters (temperature, dew point, vertical and horizontal winds, etc.) which are displayed in real-time to the flight crew. ...
National and international concern about the health effects and continued use of Pb, Cd, As and Hg as well as other metals has defined a need for improved estimates of the long-term risks to ecosystems and human health from metals released from mining, metallurgical and energy production activities. A research aircraft was used to determine the microphysical and chemical properties of airborne particulate metal emissions from the Nanticoke coal-fired power-generating station located on the north shore of Lake Erie, Ontario, and the Horne copper smelter at Rouyn-Noranda, Quebec. These properties are critical to the determi- nation of the deposition rates of the metals emitted, and hence the potential for these species to have impacts on local or distant ecosystems. An overview of the measurements made during the study is given. The size distributions of particles emitted from the stacks and observed within 5 km of the point of emission are briefly described. After dilution by ambient air, the concentration of particles smaller than 0.135 µm in diameter in the plumes is tens of thousands per cubic centimetre, far exceeding the concentrations found in ambient air. However, in the size range 0.135 to 3 µm diameter the plumes generally contribute about one to four times more particles than present in ambient air.
... The NRC Twin Otter aircraft is instrumented to measure the three components of atmospheric turbulence over a frequency range 0-16 Hz, as well as turbulent fluxes of momentum, sensible and latent heat, CO 2 and O 3 using the EC technique. Instrumentation and flux calculation procedures are described in detail in MacPherson et al. (2001). With a 10-Hz sampling rate, the aircraft platform has a spatial resolution on about 5.5 m, based on an averaged air-speed of 55 m s À1 . ...
... We also investigate the correlation between fluxes of different scalars for different scale classes to assess if the pragmatic approach of correcting EC tower measurements using the energy imbalance according to the Bowen ratio [e.g., Twine et al., 2000] and correcting CO 2 fluxes with the imbalance ratio is justified. [10] The data for this study were measured on board of the Twin Otter research aircraft [MacPherson et al., 2001] of the Canadian National Research Council (NRC) along a 115 km transect. Sixteen flights were conducted during the growing season from May to October of 1994 [Sellers et al., 1997]. ...
A wavelet analysis was applied to airborne flux measurements over a boreal ecosystem in Canada to investigate thermally induced mesoscale circulations and turbulent organized structures, which are according to large eddy simulation studies considered as one major reason for the energy balance closure problem. Fluxes of sensible heat, latent heat, carbon dioxide, and ozone were separated into a mesoscale and a small-scale turbulence part to quantify those flux contributions that cannot be captured with single-tower measurements. Mesoscale fluxes were comparable in magnitude to the energy balance residuals from ground-based tower measurements close to the flight track. A scale-dependent correlation analysis between the fluxes of different scalar quantities could not justify the common practice of correcting eddy covariance measurements of the sensible and the latent heat flux for the lack of energy balance closure according to the Bowen ratio or of correcting carbon dioxide fluxes according to the energy balance residual.
... Relevant observations were collected as part of the MAGS field campaign from end of May to the middle of July, 1999, covering the snow melt period and the early summer; grid flights were conducted on 10 different days. The operations of the Twin Otter research aircraft during this campaign are described by MacPherson et al. (2001), and preliminary results of the MAGS aircraft measurements presented by Brown-Mitic et al. (2001). The nine parallel lines of the grid flight were oriented in the east–west direction, and this pattern was flown first from south–east to north–west, and then in the reciprocal direction. ...
The objective of this study is to produce two-dimensional maps of the sensible and the latent heat fluxes from airborne measurements,
based on the analysis of a flight pattern, called grid flights. A footprint model with along-wind and cross-wind components
was used to project the measured fluxes onto the surface map. The method was applied to measurements over Arctic tundra during
the Mackenzie Area GEWEX (Global Energy and Water Cycle Experiment) Study (MAGS) 1999. The resulting flux estimates were computed
by integration of a wavelet transform, and corrected for long wavelength losses using information from 100km long regional
runs that were conducted close to the grid flights. The random flux error was estimated based on the flight length that is
represented in each map element, and a map resolution of 3×3km was chosen in order to keep the average random error of
the latent heat flux below 25%. The random error of the sensible heat flux was smaller by a factor of 1.4 on average. An analysis
of airborne flux measurements at different altitudes showed no significant increase of flux estimates for measurement heights
below 90m. Thus, the fluxes measured at heights between 48 and 64m were not corrected for vertical flux divergence. The
resulting flux maps provide quantitative two-dimensional estimates of the energy exchange between the surface and the atmosphere
during the snow melt period in an Arctic environment, which are well-suited for calibration and validation of numerical models.
... The NRC Twin Otter aircraft is instrumented to measure the three components of atmospheric turbulence over a frequency range 0-16 Hz, as well as turbulent fluxes of momentum, sensible and latent heat, CO 2 and O 3 using the EC technique. Instrumentation and flux calculation procedures are described in detail in MacPherson et al. (2001). With a 10-Hz sampling rate, the aircraft platform has a spatial resolution on about 5.5 m, based on an averaged air-speed of 55 m s À1 . ...
The importance of constraining the global budget of nitrous oxide (N2O) has been well established. The current global estimate of the contribution of N2O to total anthropogenic greenhouse gas emissions from agriculture is about 69%. Considerable progress has been made over the past few years in developing tools for quantifying the emissions from agricultural sources, at the local and field scale (i.e., chamber and tower-based measurements) as well as at the landscape and regional levels (i.e., aircraft-based measurement and modelling). However, aggregating these emissions over space and time remains a challenge because of the high degree of temporal and spatial variability. Emissions of N2O in temperate climate are largely event driven, e.g., in Eastern Canada, large emissions are observed right after snowmelt. The average emissions during the snowmelt period vary considerably, reflecting the influence of many controlling factors. Cumulative emissions reported here range from 0.05 kg N2O-N ha−1 in Western Canada to 1.26 kg N2O-N ha−1 in Eastern Canada, values that reflect differences in climatic zones and fertilizer management practices. This paper describes the tools for refining the global N2O budget and provides examples of measurements at various scales. Tower-based and aircraft measurement platforms provide good data for quantifying the variability associated with the measurements. Chamber-based methods lack the temporal and spatial resolution required to follow the event driven nature of N2O fluxes but provide valuable information for evaluating management practices. The model DeNitrification and DeComposition is an example of a technique to estimate N2O emissions when no data is available.
An artificial neural network (ANN) is presented for the purpose of estimating passive microwave (PMW) brightness temperatures over snow covered land in North America. The NASA Catchment Land Surface Model (Catchment) is used to define snowpack properties; the Catchment-based ANN is then trained with PMW measurements acquired by the Advanced Microwave Scanning Radiometer (AMSR-E). A comparison of ANN output against AMSR-E measurements not used during training activities as well as a comparison against independent PMW measurements collected during airborne surveys demonstrates the predictive skill of the ANN. When averaged over the study domain for the 9-year study period, computed statistics (relative to AMSR-E measurements not used during training) for multiple frequencies and polarizations yielded a near-zero bias, a root mean squared error less than 10 K, and a time series anomaly correlation coefficient of approximately 0.5. The ANN demonstrates skill during the accumulation phase when the snowpack is relatively dry as well as during the ablation phase when the snowpack is ripe and relatively wet. Overall, the results suggest the ANN could serve as a computationally efficient measurement operator for data assimilation at the continental scale.
Aircraft microwave radiometer measurements at 19 and 37 GHz were made over a 40 km2 agricultural area in southern Ontario on 16 and 23 May 2001 when the average soil moisture in the area was 28 and 40%, respectively. SSM/I satellite data and ground-based measurements of soil moisture were collected over the period 2 May to 25 July 2001. The emissivity of a water body (Lake Huron) calculated from the aircraft and satellite microwave radiometer measurements agreed with model calculations to within 0.02, except for the aircraft 37 GHz V channel. The 19 GHz emissivity measured by the SSM/I was higher than coincident aircraft measurements by 0.02 in moister soil conditions and 0.04 in drier conditions. Vegetation height increased from a maximum of 40 cm in hay fields in May to up to 200 cm in corn fields in July. There was a statistically significant relationship between soil moisture and 19 GHz H data for aircraft and SSM/I measurements in May. However, the standard error in the soil moisture estimate was 7%. Soil moisture seemed to have very little influence on 19 and 37 GHz emission during June and July. When the mean monthly emissivity for the May to July period was calculated from the SSM/I data, there was found to be no significant variation from month to month.
Airborne and satellite brightness temperature (TB) measurements were combined with intensive field observations of sub-Arctic tundra snow cover to develop the framework for a new tundra-specific passive microwave snow water equivalent (SWE) retrieval algorithm. The dense snowpack and high sub-grid lake fraction across the tundra mean that conventional brightness temperature difference approaches (such as the commonly used 37 GHz–19 GHz) are not appropriate across the sub-Arctic. Airborne radiometer measurements (with footprint dimensions of approximately 70 × 120 m) acquired across sub-Arctic Canada during three field campaigns during the 2008 winter season were utilized to illustrate a slope reversal in the 37 GHz TB versus SWE relationship. Scattering by the tundra snowpack drives a negative relationship until a threshold SWE value is reached near 130 mm at which point emission from the snowpack creates a positive but noisier relationship between 37 GHz TB and SWE.
Methane and nitrous oxide fluxes were measured at the field to landscape scale by combining tunable diode laser (TDL) technology with micrometeorological techniques. The three following micrometeorological measurement platform were used: (1) tower-based eddy covariance and flux-gradient techniques for measuring methane fluxes over the Canadian boreal forest and nitrous oxide over agricultural fields; (2) blimp-based nocturnal boundary layer (NBL) budget technique over agricultural areas for measuring nitrous oxide fluxes and (3) the NRC Twin Otter aircraft-based relaxed eddy accumulation (REA) to measure methane fluxes over the Canadian boreal forest. The techniques were applied using the TDL in situ (field applications) as well as in the laboratory (environmentally controlled conditions for very high resolution). The latter is accomplished by decoupling in situ air sample collection using PTFE bags from the actual air sample analysis using the TGA100. The application of the TDL to REA and NBL flux measurement is unique. Its versatility is illustrated using results obtained from experiments carried out at scales varying from field to farms to landscape. The results of these experiments clearly demonstrate the importance of knowing the variability of fluxes temporally and spatially to broach issues of scaling up to obtain fluxes representative of large areas.
This paper describes the development of an aerodynamic model identification technique on a transport aircraft with natural icing effects. The goal was to generate a six-degree-of-freedom flight dynamics model, which could be used to simulate the aircraft response to the effects of ice accretion. The National Research Council of Canada's aerodynamic model identification process was used to develop and validate the aircraft model in icing effects. The data used in the analysis were collected in two winter in-flight icing studies (Alliance Icing Research Studies 1.5 and 2.0) over the Mirabel airport near Montreal, Canada and surrounding regions in Ontario, Quebec and New York state. The aerodynamic effects of airframe icing were modelled based on the changes in stability and control characteristics of Canada's National Research Council Convair 580 airborne research aircraft. Despite the requirement to operate the airframe anti-icing system during the icing encounters, measurable degradation of aircraft stability and control derivatives occurred. This degradation was correlated to icing cloud microphysical data collected using wing-mounted probes. The combination of liquid water content, outside air temperature and true air speed parameters were found to be correlated to the aircraft degradation.
Microwave radiometers owned by the Meteorological Service of Canada (MSC) have been flown since 1996 on the National Research Council of Canada's Twin Otter aircraft in support of MSC remote sensing research. The airborne missions are part of a climate research program focussed on the development and validation of algorithms to retrieve information on cryospheric and other climate variables (e.g. soil moisture). The Twin Otter installation consists of 5 microwave radiometers at 1.4, 6.9, 19.35, 37, and 85.5 GHz frequencies, making it a unique combined low and high frequency package for passive microwave research. This paper provides an overview of the microwave radiometers, their installation and operation on the Twin Otter aircraft and a summary of the science investigations that have been conducted and are planned for the future.
New multiscale research datasets were acquired in central Saskatchewan, Canada during February 2003 to quantify the effect of spatially heterogeneous land cover and snowpack properties on passive microwave snow water equivalent (SWE) retrievals. Microwave brightness temperature data at various spatial resolutions were acquired from tower and airborne microwave radiometers, complemented by spaceborne Special Sensor Microwave/Imager (SSM/I) data for a 25×25 km study area centered on the Old Jack Pine tower in the Boreal Ecosystem Research and Monitoring Sites (BERMS). To best address scaling issues, the airborne data were acquired over an intensively spaced grid of north-south and east-west oriented flight lines. A coincident ground sampling program characterized in situ snow cover for all representative land cover types found in the study area. A suite of micrometeorological data from seven sites within the study area was acquired to aid interpretation of the passive microwave brightness temperatures. The in situ data were used to determine variability in SWE, snow depth, and density within and between forest stands and land cover types within the 25×25 km SSM/I grid cell. Statistically significant subgrid scale SWE variability in this mixed forest environment was controlled by variations in snow depth, not density. Spaceborne passive microwave SWE retrievals derived using the Meteorological Service of Canada land cover sensitive algorithm suite were near the center of the normally distributed in situ measurements, providing a reasonable estimate of the mean grid cell SWE. A realistic level of SWE variability was captured by the high-resolution airborne data, showing that passive microwave retrievals are capable of capturing stand-to-stand SWE variability if the imaging footprint is sufficiently small.
Several recent large-scale experiments in land-surface climatology have used the combination of aircraft- and tower-based flux measurements. Within these experiments, much effort has been made to assess the potential of aircraft to serve as extended observation platforms for the scaling up from local (tower-based) to regional estimates of surface-atmosphere exchange. Data collected as part of the California Ozone Deposition Experiment (CODE), during a one-month period of consistent day-to-day wind and radiation conditions, were particularly conducive to such a study. Aircraft-based flux estimates obtained at 30 and 60 m above two vineyard sites of approximately 9 km2 (site A, 6 km x 1.5 km and site B, 4.5 km x 2 krn) were compared to tower-based measurements made at 9.4 m above a section of site A. This paper shows that over the measuring period the sum of sensible and latent heat flux at 30 m, as measured with the aircraft-based system, was about 11 % less than that measured with a tower-based system at 9.4 m. It also shows that fluxes at 30 m were on the average about 10% larger than those at 60 m. It documents the flux variability of CO2, sensible and latent heat and ozone observed over relatively homogeneous surfaces. Although aircraft-tower comparisons must be interpreted with caution, due to the dissimilar surface areas sampled by the stationary and moving sensors located at different elevations, the consistent relationship obtained between these two sampling systems demonstrates the complementary nature of such measurements. It confirms that very repeatable measurements can be obtained with aircraft-based systems over distances as short as a few kilometers. It also demonstrates that compositing data for several runs and for several days !From aircraft- and tower-based measurements can provide diurnal patterns of fluxes of sensible and latent heat as well as CO2 and O3 on a regional scale.
Traditional techniques for the calibration of the aircraft-relative wind vector from flight maneuvers are discussed
with special regard to the effects of perturbations in the flow patterns around the aircraft body during periods
of significant accelerations and angular rates (rapidly varying motion). A procedure is developed that allows
both unbiased determination of steady-flight calibration parameters and explicit determination and characterization
of errors in measured flow quantities that result from flow perturbations induced during the rapidly
varying motion. This technique is applied to the case of air vector measurements from a five-hole pressure probe
mounted under the wing of a Convair 580 research aircraft operated by the Canadian National Research Council.
Results indicate that during pitching, yawing, and rolling maneuvers air data measurements at the pressure probe
contain substantial errors that are associated with adjustments of the oncoming airflow to the sudden wing
translations and rotations, as well as associated with variations in the strength and pattern of the along-wing
sidewash circulation. In addition, the fuselage-measured static pressure position error is strongly affected by
pressure pattern changes during strong longitudinal accelerations and, to a lesser extent, by lateral and normal
accelerations during pitching and yawing motions. Empirical corrections to the pressure probe and static pressure
measurements are derived to account for these effects, using multiple regression techniques. Under steady flight
conditions, these corrections are small, but during rapid maneuvers they reduce the peak-to-trough errors in the
derived earth-relative winds from 61.5 m s21 (uncorrected) to around 60.6 m s21 in the case of the horizontal
wind components, and 60.4 m s21 in the case of vertical wind components.
Regional estimates of fluxes of volatile organic compounds (VOCs) are required to improve our understanding of their role in the chemistry of the atmosphere. Flux measurements on such a scale can best be obtained using aircraft-based systems. These systems usually rely on the eddy covariance technique, which requires fast response gas sensors for flux measurement, but such sensors are not available for most organic compounds, therefore, the relaxed eddy-accumulation (REA) technique was selected. An aircraft-based REA sampling system was developed and used to measure isoprene emission over the boreal forest during the 1996 summer. Over a short period in July at the Boreal Ecosystem/Atmosphere Study (BOREAS) southern study area (SSA), the isoprene fluxes ranged from −0.06 to 1.79μgm-2s-1, with a mean of 0.59±0.34μgm-2s-1, while in August at the BOREAS northern study area (NSA) the isoprene fluxes ranged from 0.00 to 0.26μgm-2s-1, with a mean of 0.14±0.09μgm-2s-1. In the SSA, the isoprene fluxes over aspen ranged from 0.44 to 1.79μgm-2s-1, with a mean of 0.92±0.33μgm-2s-1, whereas over black spruce, isoprene fluxes ranged from −0.06 to 0.54μgm-2s-1, with a mean of 0.36±0.21μgm-2s-1. The isoprene fluxes were exponentially correlated with solar radiation and radiative surface temperature. High correlations between isoprene fluxes and the fluxes of CO2 and latent heat were also observed. Carbon lost through isoprene emissions was about 0.7 and 0.8% of the CO2 assimilation rate for aspen and black spruce, respectively. The results demonstrate that the aircraft-based relaxed eddy-accumulation technique is a promising approach for quantifying the atmosphere–surface exchange of VOCs on a regional scale.