Atmospheric Temperature Measurements Research Articles

Detection of atmospheric temperature by using polarization high-spectral-resolution lidar.

In order to achieve high signal-to-noise ratio by using small laser energy and telescope aperture, we present a polarization filter in high-spectral-resolution lidar (HSRL) for the measurement of atmospheric temperature. Compared with the filter method in a traditional HSRL in which the intensity of the return signal is split into the different transmission channel of a discriminator, the advantage of this filter system is that the intensity of the return signal is fully utilized for each discriminator channel, and the return signal changes the polarization state of the light without loss of intensity when it is incident on the two Rayleigh channels. In addition, the daytime detection capability of HSRL is improved by using a polarization optical scheme to suppress the solar background light. The advantages of the polarization filter are proven by the theoretical calculations using the Stokes vector and a Mueller matrix. In detection experiments of atmospheric temperature, the detection height is 4 km at night and 2.5 km during the day by using the pulsed energy of 50 mJ and telescope diameter of 250 mm. The results are in good agreement with the data detected by radiosonde.

Atomic vapor filter revisited: a Cabannes scattering temperature/wind lidar at 770 nm.

Using an atomic/molecular vapor as an aerosol blocking filter for atmospheric temperature measurements with a Cabannes lidar is revisited. Different problems in previously used barium and iodine filters prevented them from delivering the 78 times signal advantage (8.8 times less uncertainty) over rotational Raman lidar. We conclude that, despite the sensitivity optimization in rotational Raman lidar, a proposed Cabannes lidar utilizing potassium vapor filters can have 6.1 times less temperature uncertainty. By tuning the laser frequency cyclically to above and below the potassium D1 transition, the lidar system can measure temperature and wind simultaneously.

Toward Non-Invasive Measurement of Atmospheric Temperature Using Vibro-Rotational Raman Spectra of Diatomic Gases

We demonstrate precise determination of atmospheric temperature using vibro-rotational Raman (VRR) spectra of molecular nitrogen and oxygen in the range of 292–293 K. We used a continuous wave fiber laser operating at 10 W near 532 nm as an excitation source in conjunction with a multi-pass cell. First, we show that the approximation that nitrogen and oxygen molecules behave like rigid rotors leads to erroneous derivations of temperature values from VRR spectra. Then, we account for molecular non-rigidity and compare four different methods for the determination of air temperature. Each method requires no temperature calibration. The first method involves fitting the intensity of individual lines within the same branch to their respective transition energies. We also infer temperature by taking ratios of two isolated VRR lines; first from two lines of the same branch, and then one line from the S-branch and one from the O-branch. Finally, we take ratios of groups of lines. Comparing these methods, we found that a precision up to 0.1 K is possible. In the case of O2, a comparison between the different methods show that the inferred temperature was self-consistent to within 1 K. The temperature inferred from N2 differed by as much as 3 K depending on which VRR branch was used. Here we discuss the advantages and disadvantages of each method. Our methods can be extended to the development of instrumentation capable of non-invasive monitoring of gas temperature with broad potential applications, for example, in laboratory, ground-based, or airborne remote sensing.

Temperature extraction from spacecraft density profiles in the presence of wave activity

In the absence of direct atmospheric temperature measurements, density data along spacecraft trajectories are often used to extract temperature profiles, a process that can fail in the presence of wave activity (Leclercq et al., 2020). Because spacecraft data are often not sufficient to uniquely characterize wave-like perturbations, we examine the difference between predicted and extracted temperature profiles based on linearized solutions to the wave equations and briefly discuss the relevance to wave activity in the upper atmospheres of Mars and Titan. We find that the extracted temperatures are significantly overestimated for the full range of acoustic gravity wave parameters but are somewhat underestimated for a range of internal gravity wave parameters, and the density amplitudes can serve as a proxy for the extracted temperature amplitudes when estimating the heating rates.

Denoising Atmospheric Temperature Measurements Taken by the Mars Science Laboratory on the Martian Surface

In the present article we analyze data from two temperature sensors of the Mars Science Laboratory, which has been active in Mars since August 2012. Temperature measurements received from the rover are noisy and must be processed and validated before being delivered to the scientific community. Currently, a simple Moving Average (MA) filter is used to perform signal denoising. The application of this basic method relies on the assumption that the noise is stationary and statistically independent from the underlying structure of the signal, an arguable assumption in this kind of harsh environment. In this paper, we analyze the application of two alternative methods to process the temperature sensor measurements: the Discrete Wavelet Transform (DWT) and the Hilbert-Huang Transform (HHT). We consider two different datasets, one belonging to the current Martian measurement campaigns, and the other to the Thermal Vacuum Tests. The processing of these datasets allows to separate the random noise from the interference created by other systems. The experiments show that the MA filter may provide useful results under given circumstances. However, the proposed methods allow a better fitting for all the realistic scenarios, while providing the possibility to identify and analyze other interesting signal features and artifacts that could be later studied and classified. The large amount of data to be processed makes computational efficiency an important requirement in this mission. Considering the computational cost and the filtering performance, we propose the method based on DWT as more suitable for this application.

Simultaneous measurement of atmospheric moisture and temperature in the presence of suspended particulates using ultrasonic technique

Simultaneous measurement of atmospheric moisture and temperature in the presence of airborne particulates over an extended region using a single sensor is very important for the prediction of fog in an open environment. Here, we have developed an ultrasonic technique to measure relative humidity and temperature of open-air containing suspended particulate matter in a controlled environment. We achieved an accuracy within ±0.9 K for a temperature range of 297–302 K, and within ±2.68% for relative humidity in the range of 60%–100%. We also characterized laboratory-generated fog using ultrasound and found our results to be in agreement with the conventional optical method. At higher concentrations, our technique appears to be a better means of characterizing atmospheric moisture content compared to light.

METER.AC: Live Open Access Atmospheric Monitoring Data for Bulgaria with High Spatiotemporal Resolution

Detailed atmospheric monitoring data are notoriously difficult to obtain for some geographic regions, while they are of paramount importance in scientific research, forecasting, emergency response, policy making, etc. We describe a continuously updated dataset, METER.AC, consisting of raw measurements of atmospheric pressure, temperature, relative humidity, particulate matter, and background radiation in about 100 locations in Bulgaria, as well as some derived values such as sea-level atmospheric pressure, dew/frost point, and hourly trends. The measurements are performed by low-power maintenance-free nodes with common hardware and software, which are specifically designed and optimized for this purpose. The time resolution of the measurements is 5 min. The short-term aim is to deploy at least one node per 100 km2, while uniformly covering altitudes between 0 and 3000 m asl with a special emphasis on remote mountainous areas. A full history of all raw measurements (non-aggregated in time and space) is publicly available, starting from September 2018. We describe the basic technical characteristics of our in-house developed equipment, data organization, and communication protocols as well as present some use case examples. The METER.AC network relies on the paradigm of the Internet of Things (IoT), by collecting data from various gauges. A guiding principle in this work is the provision of findable, accessible, interoperable, and reusable (FAIR) data. The dataset is in the public domain, and it provides resources and tools enabling citizen science development in the context of sustainable development.

К настройке алгоритма вычисления барометрической высоты летательного аппарата системой воздушных сигналов

Introduction. In conditions of increasing requirements for the accuracy of determining the altitude and speed parameters of aircraft, the task of tuning up the algorithmic support of their air signal systems (SHS) based on real flight data is quite relevant. Aim. Consider the task of assessing the real value of the temperature gradient along the height of the atmosphere for the purpose of operational adjustment of the standard algorithmic support of SHS. Materials and methods. The traditional approach is to use the numerical value of the temperature gradient, adopted for the international standard atmosphere (ISA). A feature of the proposed approach is that the temperature gradient in height is determined by current measurements of atmospheric pressure and temperature, and not height and temperature. Results. Adaptive and non-adaptive parametric identification algorithms are developed. An improved version of the adaptive algorithm is proposed, which ensures proper tuning of its filtering properties to a specific statistical situation. Algorithms were tested both according to the characteristics of the ISA using computer-generated random interference, and according to the results of real measurements known in the literature obtained using a meteorological rocket. The properties of adaptive and non-adaptive algorithms are compared. It is shown that repeated “running” of the same experimental data through an adaptive algorithm leads to almost the same accuracy of the gradient estimate, as when using a non-adaptive algorithm. Conclusion. The implementation of the algorithms improves the accuracy of determining the barometric altitude of the aircraft (AC), does not require any modernization of the hardware of the SHS, only some addition of the algorithmic support of the system is necessary. The adaptive algorithm is recommended for use in the case of a significant drift of atmospheric characteristics for the operational adjustment of the system.

Demonstration of a combined differential absorption and high spectral resolution lidar for profiling atmospheric temperature.

This work presents the first demonstration of atmospheric temperature measurement using the differential absorption lidar (DIAL) technique. While DIAL is routinely used to measure atmospheric gases such as ozone and water vapor, almost no success has been found in using DIAL to measure atmospheric temperature. Attempts to measure temperature using a well-mixed gas like oxygen (O2) have largely failed based on a need for quantitative ancillary measurements of water vapor and atmospheric aerosols. Here, a lidar is described and demonstrated that simultaneously measures O2 absorption, water vapor number density, and aerosol backscatter ratio. This combination of measurements allows for the first measurements of atmospheric temperature with useful accuracy. DIAL temperature measurements are presented to an altitude of 4 km with 225 m and 30 min resolution with accuracy better than 3K. DIAL temperature data is compared to a co-located Raman lidar system and radiosondes to evaluate the system's performance. Finally, an analysis of current performance characteristics is presented, which highlights pathways for future improvement of this proof-of-concept instrument.

Design of a high-spectral-resolution lidar for atmospheric temperature measurement down to the near ground.

In this paper, a high-spectral-resolution lidar (HSRL) for profiling atmospheric temperature from the ground to 10 km is proposed. A double Nd:YAG laser produces the transmitted laser at 532 nm. The backscattering lidar signal is passed through two different saturated iodine-vapor filters and thus obtains molecular scattering signals that can be employed to determine the temperature. A coaxial postposition transceiver is constructed with an off-axis aspheric reflective telescope (OART). The design of the transceiver and that of the OART are demonstrated. With this transceiver, the lidar blind zone where the overlap factor is zero can be reduced greatly, and accurate temperature measurement for full elevation can be achieved. The whole system is optimized with theoretical models based on geometrical optics and statistical error analyses. Monte Carlo simulations display the performance of the designed HSRL, showing that the all-day temperature retrieval error is better than 1.4 K from the ground to 10 km. The proposed HSRL is expected to provide more accurate atmospheric auxiliary parameters for the detection of aerosols' optical characteristics.

Verification of Fengyun-3D MWTS and MWHS Calibration Accuracy Using GPS Radio Occultation Data

The newly launched Fengyun-3D (FY-3D) satellite carries microwave temperature sounder (MWTS) and microwave humidity sounder (MWHS), providing the global atmospheric temperature and humidity measurements. It is important to assess the in orbit performance of MWTS and MWHS and understand their calibration accuracy before using them in numerical weather prediction and many other applications such as hurricane monitoring. This study aims at quantifying the biases of MWTS and MWHS observations relative to the simulations from the collocated Global Positioning System (GPS) radio occultation (RO) data. Using the collocated FY-3C Global Navigation Satellite System Occultation Sounder (GNOS) RO data under clear-sky conditions as inputs to Community Radiative Transfer Model (CRTM), brightness temperatures and viewing angles are simulated for the upper level sounding channels of MWTS and MWHS. In order to obtain O − B statistics under clear sky conditions, a cloud detection algorithm is developed by using the two MWTS channels with frequencies at 50.3 and 51.76 GHz and the two MWHS channels with frequencies centered at 89 and 150 GHz. The analysis shows that for the upper air sounding channels, the mean biases of the MWTS observations relative to the GPS RO simulations are negative for channels 5–9, with absolute values < 1 K, and positive for channels 4 and 10, with values < 0.5 K. For the MWHS observations, the mean biases in brightness temperature are negative for channels 2–6, with absolute values < 2.6 K and relatively small standard deviations. The mean biases are also negative for channels 11–13, with absolute values < 1.3 K, but with relatively large standard deviations. The biases of both MWTS and MWHS show scan-angle dependence and are asymmetrical across the scan line. The biases for the upper air MWTS and MWHS sounding channels are larger than those previously derived for the Advanced Technology Microwave Sounder.

Multirotor UAV-Based Platform for the Measurement of Atmospheric Turbulence: Validation and Signature Detection of Tip Vortices of Wind Turbine Blades

AbstractThe present study describes the development of a technique for the measurement of atmospheric turbulence and temperature at a point in space based on the integration of a fast-response multihole pressure probe and a thermocouple with an inertial measurement unit on a multirotor UAV-based platform. This allows for an accurate measurement of time series of the three components of the velocity vector and temperature at any point in space in which the UAV can fly within the limitations of its autonomy. The presented technique relies on an accurate correction of the three-component velocity vector measured by the pressure probe on the frame of reference of the UAV—noninertial—with the information provided by the inertial measurement unit. The study includes a validation of the technique against sonic anemometry and the measurement of the signature of tip vortices shed by the blades of a full-scale wind turbine as an example of its potential.

Measurement of atmospheric neutral wind and temperature from Fabry–Perot interferometer data using piloted deconvolution

Nonlinear regression techniques, when applied to sky exposures obtained using a Fabry-Perot interferometer (FPI), are able to recover atmospheric neutral wind and temperature through inversion of the resulting fringe pattern. Current inversion methods often account for temporal fluctuation of the etalon's optical path length (caused by temperature variation in the instrument housing, for example) by characterizing the system function using isolated exposures of a frequency-stabilized laser. Because these path length changes correspond directly to shifts in the fringe pattern, they can significantly increase the total wind velocity uncertainty between laser exposures. We propose an extension to current regression techniques allowing for characterization of the optical path length and measurement of neutral wind and temperature simultaneously, thus reducing the need for frequent isolated laser exposures. This is achieved by using the laser as a pilot signal that enters the aperture of the instrument during sky exposures. We show that the extension can lead to a lower variance estimator for velocity when the optical path length has a significant time-varying component. Additionally, several pragmatic physical configurations that would allow for construction of a piloted signal in a real system are tested and compared using an FPI installation at the Urbana Atmospheric Observatory.

Ground-based Observations of the Polar Region Space Environment at the Jang Bogo Station, Antarctica

Jang Bogo Station (JBS), the second Korean Antarctic research station, was established in Terra Nova Bay, Antarctica (74.62°S 164.22°E) in February 2014 in order to expand the Korea Polar Research Institute (KOPRI) research capabilities. One of the main research areas at JBS is space environmental research. The goal of the research is to better understand the general characteristics of the polar region ionosphere and thermosphere and their responses to solar wind and the magnetosphere. Ground-based observations at JBS for upper atmospheric wind and temperature measurements using the Fabry-Perot Interferometer (FPI) began in March 2014. Ionospheric radar (VIPIR) measurements have been collected since 2015 to monitor the state of the polar ionosphere for electron density height profiles, horizontal density gradients, and ion drifts. To investigate the magnetosphere and geomagnetic field variations, a search-coil magnetometer and vector magnetometer were installed in 2017 and 2018, respectively. Since JBS is positioned in an ideal location for auroral observations, we installed an auroral all-sky imager with a color sensor in January 2018 to study substorms as well as auroras. In addition to these observations, we are also operating a proton auroral imager, airglow imager, global positioning system total electron content (GPS TEC)/scintillation monitor, and neutron monitor in collaboration with other institutes. In this article, we briefly introduce the observational activities performed at JBS and the preliminary results of these observations.

A highly miniaturized satellite payload based on a spatial heterodyne spectrometer for atmospheric temperature measurements in the mesosphere and lower thermosphere

Abstract. A highly miniaturized limb sounder for the observation of the O2 A-band to derive temperatures in the mesosphere and lower thermosphere is presented. The instrument consists of a monolithic spatial heterodyne spectrometer (SHS), which is able to resolve the rotational structure of the R-branch of that band. The relative intensities of the emission lines follow a Boltzmann distribution and the ratio of the lines can be used to derive the kinetic temperature. The SHS operates at a Littrow wavelength of 761.8 nm and heterodynes a wavelength regime between 761.9 and 765.3 nm with a resolving power of about 8000 considering apodization effects. The size of the SHS is 38 × 38 × 27 mm3 and its acceptance angle is ±5∘. It has an etendue of 0.01 cm2 sr. Complemented by front optics with an acceptance angle of ±0.65∘ and detector optics, the entire optical system fits into a volume of about 1.5 L. This allows us to fly this instrument on a 3- or 6-unit CubeSat. The vertical field of view of the instrument is about 60 km at the Earth's limb when operated in a typical low Earth orbit. Integration times to obtain an entire altitude profile of nighttime temperatures are on the order of 1 min for a vertical resolution of 1.5 km and a random noise level of about 1.5 K. Daytime integration times are 1 order of magnitude shorter. This work presents the design parameters of the optics and a radiometric assessment of the instrument. Furthermore, it gives an overview of the required characterization and calibration steps. This includes the characterization of image distortions in the different parts of the optics, visibility, and phase determination as well as flat fielding.

Variation of meteorological parameters and its effect on refractive index of air over Lagos Nigeria

Variations of meteorological parameters affect the refractive index in the lower atmosphere. In this study, three years (2011-2013) results of measurements of Atmospheric pressure, Temperature, and Relative humidity from Davis Vantage pro2 automatic weather station installed at the ground surface at Lagos (6o 27' N, 5 12' E) Lagos State, were used to examine the effects of meteorological parameters on refractive index using International Telecommunication Union (ITU-R) model. The results show that average hourly variations of refractivity in the dry season is largely as a result of the variations of the wet component (humidity) while the average daily variations of surface radio refractivity in the rainy season is as a result of the variations of the dry (pressure) component of surface radio refractivity. Refractivity reveals seasonal variations with high values in the rainy season and low values in the dry season over the location. The seasonal variation of refractivity of the troposphere is a function of climatic condition while the hourly or diurnal variation of refractivity depends on local meteorology as observed from the results obtained from study location.Keywords: Refractivity, Temperature, Atmospheric pressure, Relative Humidity

Study of average seasonal variations of surface radio refractivity across some selected cities in Nigeria

The average seasonal variations of surface radio refractivity based on measurement of atmospheric pressure, temperature and relative humidity made across Yola (9 o 11' N, 12 o 30' E), Anyigba (7 o 45' N, 6 o 45' E), Lagos (6 o 27' N, 5 o 12' E), and Port-Harcourt (4 o 48'N, 7 o E) Nigeria, is reported. The measurement was made using wireless automatic weather station installed at the surface of each station under study. The study utilized three years of meteorological data measured from January 2010 to December 2013 to calculate the surface radio refractivity using empirical formula recommended by the International Telecommunication Union (ITU-R 453, 2012). The result shows that the average value of surface radio refractivity showed seasonal variations with high values during the rainy season and low values during the dry season with an increase in the value of surface radio refractivity of 242N units at Anyigba station to a maximum value of 384-N units at Lagos station. The result also shows that climatic condition is the force behind the seasonal variations of surface radio refractivity in all study stations. Keywords: Refractivity, Temperature, Atmospheric pressure, Relative Humidity

Analysis of moisture conditions in the lowland areas using high resolution spectral data from the Sentinel-2 satellite and the GIS tools

Research concerning agricultural drought issue mainly focuses on the methods based on long-term atmospheric data, temperature, precipitation and evaporation measurements. On the other hand, the scientific bibliography shows the possibilities of using spectral data for description the state of plants. The general availability and increasing resolution of the spectral and temporal data create a chance for monitoring and forecasting deficiencies of soil moisture based on spectral images. Paper presents the results of analysis of the moisture conditions in soil-plant environment in the lowland catchment area using the spectral data obtained from the Sentinel-2 European Space Agency satellite for period February-November 2016. These spectral data were used for the calculation the Normalized Differential Vegetation Index (NDVI) which provided information about moisture conditions in the soil-plant environment. Then, the values of NDVI index were compared with the data obtained from the field investigations. The analyses have showed the spatial and temporal variability of moisture conditions in the soil-plant environment determined on the background of the spectral indicators and the existence of some dependences between climatic and spectral indicators characterizing soil-plant environment.

Airborne demonstration of atmospheric oxygen optical depth measurements with an integrated path differential absorption lidar

We report on an airborne demonstration of atmospheric oxygen (O2) optical depth measurements with an Integrated Path Differential Absorption (IPDA) lidar using a fiber-based laser transmitter and photon counting detectors. Accurate atmospheric temperature and pressure measurements are needed for NASA’s Active Sensing of CO2 Emissions over Nights, Days and Seasons (ASCENDS) mission. Since O2 is uniformly mixed in the atmosphere, its spectrum can be used to estimate the dry mixing ratio of CO2. In its airborne configuration, the IPDA lidar uses an Erbium Doped Fiber amplifier, a frequency doubler and single photon counting detectors to measure O2 absorption at multiple wavelengths near 765 nm. This instrument was deployed in 2013 and 2014 aboard NASA’s DC-8 airborne laboratory as part of two campaigns to measure CO2 mixing ratios over a wide range of topography and weather conditions from altitudes ranging between 3 km and 13 km. In this paper we will review a summary of the results from our flights, discuss the errors that limit the precision and accuracy of the measurement and identify possible areas of improvement.

Water Vapor Radiometer: Measuring Instrument of Atmospheric Brightness Temperature

Results are presented for pilot studies of the error in measuring atmospheric brightness temperature at frequencies 20.7 and 31.4 GHz in the vicinity of water vapor emission lines. The accuracy of atmospheric brightness temperature measurements was evaluated using the water vapor radiometer at the Zelenchukskaya observatory. Measurements were made using the PNShI200 wide-aperture low-temperature noise generator, a working standard for the unit of equivalent noise temperature. The requirements for radiophysical characteristics and accuracy of reproduction of a unit of noise temperature were formulated for prospective reference wide-aperture low-temperature noise generators.