Ground-based Spectrometer Measurements Research Articles

Comparison of long-term trends and interannual variations of the NO₂ content in the atmosphere according to satellite (OMI) and ground-based spectrometric measurements at NDACC stations

Results of analysis of long-term trends and interannual variations of the NO₂ content in the atmosphere according to measurements with the Ozone Monitoring Instrument (OMI) aboard the EOS-Aura satellite in 2004–2020 are compared to the results of a similar analysis of the NO₂ content derived from independent spectrometric twilight NO₂ measurements by zenith-scattered solar radiation at stations of the Network for the Detection of Atmospheric Composition Change (NDACC)). According to both the data, seasonally dependent estimates of linear NO₂ trends and variations of the NO₂ content under the influence of the 11-year cycle of solar activity and large-scale circulation factors such as the Arctic and Antarctic Oscillations, variations in ocean surface temperature in the Niño 3.4 zone, and the quasi-biennial oscillation in zonal wind in the equatorial stratosphere have been obtained. In general, a good qualitative and, in some cases, quantitative correspondence between estimates of interannual variations of NO₂ has been obtained. For interannual variations of stratospheric NO₂, not a bad correspondence between estimates based on satellite and ground-based data has been obtained on average for all stations, but the correspondence between trend estimates is noticeably worse. The best correspondence between the analysis results has been obtained for Zvenigorod station. For stratospheric NO₂, it was noted in 80–90% of cases, and the correspondence for tropospheric NO₂ is practically 100%.

Development of Methods for Remote Monitoring of Leaf Diseases in Wheat Agrocenoses.

The development of remote methods for diagnosing the state of crops using spectral equipment for remote sensing of the Earth and original monitoring tools is the most promising solution to the problem of monitoring diseases of wheat agrocenoses. A research site was created on the experimental field of the Federal Research Center of Biological Plant Protection. Within the experimental field with a total area of 1 ha, test plots were allocated to create an artificial infectious background, and the corresponding control plots were treated with fungicides. The research methodology is based on the time synchronization of high-precision ground-based spectrometric measurements with satellite and unmanned remote surveys and the comparison of the obtained data with phytopathological field surveys. Our results show that the least-affected plants predominantly had lower reflectance values in the green, red, and red-edge spectral ranges and high values in the near-infrared range throughout the growing season. The most informative spectral ranges when using satellite images and multispectral cameras placed on UAVs are the red and IR ranges. At the same time, the high frequency of measurements is of key importance for determining the level of pathogenic background. We conclude that information acquisition density does not play as significant of a role as the repetition of measurements when carrying out ground-based spectrometry. The use of vegetation indices in assessing the dynamics of the spectral images of various survey systems allows us to bring them to similar values.

Identification of the Spectral Patterns of Cultivated Plants and Weeds: Hyperspectral Vegetation Indices

The accurate recognition of weeds on crops supports the spot application of herbicides, the high economic effect and reduction of pesticide pressure on agrocenoses. We consider the approach based on the quantitative spectral characteristics of plant objects to be the most appropriate for the development of methods for the spot application of herbicides. We made test plots with different species composition of cultivated and weed plants on the experimental fields of the scientific crop rotation of the Federal Research Center of Biological Plant Protection. These plants form the basis of the agrocenoses of Krasnodar Krai. Our primary subjects are sunflower crops (Helianthus annuus L.), corn (Zea mais L.) and soybean (Glycine max (L.)). Besides the test plots, pure and mixed backgrounds of weeds were identified, represented by the following species: ragweed (Ambrosia artemisiifolia L.), California-bur (Xanthium strumarium L.), red-root amaranth (Amaranthus retroflexus L.), white marrow (C. album L.) and field milk thistle (Sonchus arvensis L.). We used the Ocean Optics Maya 2000-Pro automated spectrometer to conduct high-precision ground-based spectrometric measurements of selected plants. We calculated the values of 15 generally accepted spectral index dependencies based on data processing from ground hyperspectral measurements of cultivated and weed plants. They aided in evaluating certain vegetation parameters. Factor analysis determined the relationship structure of variable values of hyperspectral vegetation indices into individual factor patterns. The analysis of variance assessed the information content of the indicators of index values within the limits of the selected factors. We concluded that most of the plant objects under consideration are characterized by the homogeneity of signs according to the values of the index indicators that make up the selected factors. However, in most of the cases, it is possible to identify different plant backgrounds, both by the values of individual vegetation indices and by generalized factorial coefficients. Our research results are important for the validation of remote aerospace observations using multispectral and hyperspectral instruments.

In-flight performance of the Multi-band Uncooled Radiometer Instrument (MURI) thermal sensor

NASA's Earth Science and Technology Office (ESTO) encourages and promotes new and innovative science technologies to improve how the Earth is observed from space. Through their Instrument Incubator Program (IIP), an uncooled multispectral thermal instrument was fabricated and flight-tested to demonstrate its potential utility to support future spaceborne missions. While uncooled systems offer the attractive advantage of eliminating the need for large and expensive cryocoolers, they naturally introduce challenges that must be overcome to achieve the fidelity observed in image data acquired by existing cooled spaceborne instruments.In this work, the Multi-band Uncooled Radiometer Instrument (MURI) system, designed and built by Leonardo DRS, is fabricated using custom microbolometer detector arrays also developed by Leonardo DRS. Potential issues associated with thermal imaging using microbolometers from a spaceborne platform are discussed and innovative engineering solutions to overcome these issues are highlighted. Details of three airborne campaigns designed to assess the fidelity of MURI image data, using Landsat 8's Thermal Infrared Sensor's (TIRS) radiometric & geometric requirements as a baseline, are presented. Results of these campaigns show that the as-built MURI system significantly outperforms these requirements, as compared to ground-based reference measurements. Sustainable Land Imaging (SLI) requirements indicate that a five-band instrument is desirable to improve future Landsat science while maintaining continuity with previous thermal instruments. Considering its multiband design, temperature/emissivity separation (TES) is applied to MURI flight data and compared to ground-based spectrometer measurements for several materials. Results of this study indicate that MURI's TES performance is in-line with existing spaceborne systems. When considered in conjunction with its radiometric fidelity, the MURI uncooled system represents an intriguing option for future space-based missions.

Model for selecting the Earth observation satellite systems by object recognition probability

Model for selecting the Earth observation satellite systems by object recognition probability

Hydrocarbon deposit mapping validation by the means of ground-based spectrometry, remote sensing and geophysical data

The probability estimation of oil and gas inside certain area is essential for decision making on the industrial exploitation of oil and gas bearing features. A quantitative assessment of the hydrocarbon contour mapping accuracy using ground-based spectrometric measurements, remote, geological and geophysical data requires a special validation procedure. Its purpose is to evaluate achieved accuracy and reliability as well as the conformance to specified requirements. The input data for validation of the hydrocarbon deposit contour by field spectrometry are the one points’ locations relative to the other contours detected by independent methods, such as remote, geological and geophysical. As the field spectrometry performed along spatial trace, the geometric drifts of other methods’ cross-points are estimated. The algorithm for the validation of hydrocarbon deposit contour mapping by field spectrometry, remote, geological and geophysical data is proposed in this paper. The algorithm was tested on over the Novotroitsky and East Rogintsy hydrocarbon deposits (Ukraine). Measurements along 14 spatial traces over the Novotroitsky’s deposit and 28 traces over the East Rogintsy’s one was carried out to perform validation. The average error probability was 0.28, which demonstrates an admissible reliability of hydrocarbon deposits contours’ mapping by field spectrometry data. The preliminary validation estimates engagement during the hydrocarbon deposits mapping provides the fact-based statistical consistency of the quantitative measurements received. In addition, it is possible to filter the outliers reasonable before final information product release, which will enhance the overall reliability.

Technique for Inverting Transmission Spectra to Measure Freon Concentration

We propose an approach to selecting the optimal parameters for solving the inverse problem for determining the total freon content (TC) from ground-based spectrometric measurements of solar radiation. The approach was developed for measurements at the St. Petersburg NDACC station using a Bruker FS125HR Fourier-transform interferometer and implemented as applied to measurements of the total content of the hydrochlorofluorocarbon R-22 (HCF2Cl). Based on the optimal set of parameters obtained, we retrieved the total R-22 content above the St. Petersburg station in the period 2009–2018 and obtained estimates of the measurement uncertainties: average systematic uncertainty 4.8%, random uncertainty 3.7% over the entire observational period. A preliminary estimate of the trend is 2.64 ± 0.22% per year.

Increase in the Stratospheric NO2 Content Derived from Results of Ground-Based Observations after the October 2003 Solar Proton Event

This paper reports on the first experimental evidence of the impact of a solar proton event on the stratospheric NO2 content derived from ground-based spectrometric measurements at middle and high latitudes of the Northern Hemisphere. In October 2003, a solar proton event caused an increase in the NO2 content in the upper stratosphere by 0.6 × 1015 cm–2, which accounted for about one-third of the increase in the column NO2 content. Solar proton events may be an essential factor for variability of the column NO2 content in the atmosphere of the high and middle latitudes.

Winter–spring anomalies in stratospheric O3 and NO2 contents over the Moscow region in 2010 and 2011

Using results of ground-based spectrometric measurements, we analyze the anomalies in the stratospheric contents of O3 and NO2 in the Moscow region related to the sudden stratospheric warming and associated distortion of the stratospheric circumpolar vortex in early February 2010 and to the latitudinal displacement of the vortex towards the European sector in late March 2011 before the final spring warming. In the former case, the O3 concentration increased up to 85% and the stratospheric column NO2 content increased twice; in the latter case, the O3 concentration decreased by a quarter and the NO2 content decreased twice in comparison with average values for the time periods preceding the onsets of the anomalies. Estimates of the statistical correlationship of the stratospheric O3 and NO2 contents with potential vorticity and geopotential have been obtained.

Seasonal features of quasi-biennial variations of NO2 stratospheric content derived from ground-based measurements

Seasonal and latitudinal distributions of amplitudes of quasi-biennial variations in total NO2 content (NO2 TC), total ozone content (TOC), and stratospheric temperature are obtained. NO2 TC data from ground-based spectrometric measurements within the Network for the Detection of Atmospheric Composition Change (NDACC), TOC data from satellite measurements, and stratospheric temperature data from ERA-Interim reanalysis are used for the analysis. The differences in the NO2 TC diurnal cycles are identified between the westerly and easterly phases of the quasi-biennial oscillations (QBO) of equatorial stratospheric wind. The QBO effects in the NO2 TC, TOC, and stratospheric temperature in the Northern (NH) and Southern (SH) hemispheres are most significant in the winter–spring periods, with essential differences between the NH and SH. The NO2 TC in the Antarctic is less for the westerly phase of the QBO than that for the easterly phase, and the NO2 TC quasi-biennial variations in the SH mid-latitudes are opposite of the variations in the Antarctic. In the NH, the winter values of the NO2 TC are generally less during the westerly QBO phase than during the easterly phase, whereas in spring, on the contrary, the values for the westerly QBO phase exceed those for the easterly phase. Along with NO2, the features of the quasi-biennial variations of TOC and stratospheric temperature are discussed. Possible mechanisms of the quasi-biennial variations of the analyzed parameters are considered for the different latitudinal zones.

Comparing data obtained from ground-based measurements of the total contents of O3, HNO3,HCl, and NO2 and from their numerical simulation

Chemistry climate models of the gas composition of the atmosphere make it possible to simulate both space and time variations in atmospheric trace-gas components (TGCs) and predict their changes. Both verification and improvement of such models on the basis of a comparison with experimental data are of great importance. Data obtained from the 2009–2012 ground-based spectrometric measurements of the total contents (TCs) of a number of TGCs (ozone, HNO3, HCl, and NO2) in the atmosphere over the St. Petersburg region (Petergof station, St. Petersburg State University) have been compared to analogous EMAC model data. Both daily and monthly means of their TCs for this period have been analyzed in detail. The seasonal dependences of the TCs of the gases under study are shown to be adequately reproduced by the EMAC model. At the same time, a number of disagreements (including systematic ones) have been revealed between model and measurement data. Thus, for example, the EMAC model underestimates the TCs of NO2, HCl, and HNO3, when compared to measurement data, on average, by 14, 22, and 35%, respectively. However, the TC of ozone is overestimated by the EMAC model (on average, by 12%) when compared to measurement data. In order to reveal the reasons for such disagreements between simulated and measured data on the TCs of TGCs, it is necessary to continue studies on comparisons of the contents of TGCs in different atmospheric layers.

Winter–spring anomalies in the stratospheric content of NO2 from ground-based measurement results

According to the results of ground-based spectrometric measurements, significant negative anomalies in the stratospheric content of NO2 were observed at a number of stations in the Northern Hemisphere during winter and spring 2011. These anomalies were accompanied by those in total ozone content (TOC) and stratospheric temperature and were caused by the transport of air masses from the region of the arctic ozone hole. The results of analysis of vertical NO2 profiles obtained at the Zvenigorod Scientific Station showed that a certain contribution to the 2011 negative anomalies of NO2 was made due to a denitrification of the polar stratosphere in the ozone-hole region. The relation between variations in the total content of NO2 and those in the TOC and temperature was analyzed for both the Northern and Southern hemispheres during winter–spring periods. It was found that this relation depends on the phase of the quasi-biennial oscillation in the stratospheric equatorial wind. Such a correlation usually intensifies if only the episodes of negative anomalies caused by the transport of stratospheric air masses from the ozone-hole region are taken into consideration.

Inferring hydroxyl layer peak heights from ground-based measurements of OH(6-2) band integrated emission rate at Longyearbyen (78° N, 16° E)

Abstract. Measurements of hydroxyl nightglow emissions over Longyearbyen (78° N, 16° E) recorded simultaneously by the SABER instrument onboard the TIMED satellite and a ground-based Ebert-Fastie spectrometer have been used to derive an empirical formula for the height of the OH layer as a function of the integrated emission rate (IER). Altitude profiles of the OH volume emission rate (VER) derived from SABER observations over a period of more than six years provided a relation between the height of the OH layer peak and the integrated emission rate following the procedure described by Liu and Shepherd (2006). An extended period of overlap of SABER and ground-based spectrometer measurements of OH(6-2) IER during the 2003–2004 winter season allowed us to express ground-based IER values in terms of their satellite equivalents. The combination of these two formulae provided a method for inferring an altitude of the OH emission layer over Longyearbyen from ground-based measurements alone. Such a method is required when SABER is in a southward looking yaw cycle. In the SABER data for the period 2002–2008, the peak altitude of the OH layer ranged from a minimum near 76 km to a maximum near 90 km. The uncertainty in the inferred altitude of the peak emission, which includes a contribution for atmospheric extinction, was estimated to be ±2.7 km and is comparable with the ±2.6 km value quoted for the nominal altitude (87 km) of the OH layer. Longer periods of overlap of satellite and ground-based measurements together with simultaneous on-site measurements of atmospheric extinction could reduce the uncertainty to approximately 2 km.

Latitudinal structure of variations and trends in stratospheric NO2

Using data from ground-based spectrometric measurements of stratospheric column nitrogen dioxide (NO2) within the Network for the Detection of Atmospheric Composition Change (NDACC), analyses are made of the diurnal and annual variations of NO2, the NO2 decrease relating to the Pinatubo eruption, the NO2 change during the 11-year cycle of solar activity (SA), and the linear trends in NO2. Latitudinal dependences of these variations and trends are revealed. In particular, the annual trend estimates of column NO2 are predominantly positive in the middle latitudes of the Southern Hemisphere (SH) whereas negative NO2 trends are observed in the middle Northern Hemisphere (NH) latitudes. Column NO2 content in the middle latitudes of the two hemispheres is generally larger during the SA minimum than during the SA maximum (negative sign of the SA effect).

Latitudinal dependence of variations in stratospheric NO2 content

Diurnal and annual variations in the NO2 total content (TC), the effect of its decrease owing to the products of the eruption of Mt. Pinatubo, its variations during an 11-year cycle of solar activity, and its linear trends are analyzed on the basis of data obtained from the ground-based spectrometric measurements of the NO2 TC in stratospheric vertical columns over the stations of the Network for the Detection of Atmospheric Composition Change. Latitudinal dependence of the indicated variations and trends is revealed. The annual estimates of the linear trends of the NO2 TC are found to be mostly positive for the middle and low latitudes of the Southern Hemisphere and negative for the middle and low latitudes of the Northern Hemisphere. The maximum values of the positive and negative trends amount to ∼10% per ten years. In the high and polar latitudes of both hemispheres, the annual trend estimates are statistically insignificant. Seasonal estimates of the trends may differ from their annual estimates. The trends and solar-activity effect in the NO2 TC, which were estimated by using the two-dimensional model SOCRATES, as well as the analytical estimates of a zonal mean trend of the NO2 TC, on the whole, significantly differ from the estimates obtained from the measurements.

Preparation of a Low-Cost Digital Camera System for Remote Sensing

Off-the-shelf consumer digital cameras are convenient and user-friendly. However, the use of these cameras in remote sensing is limited because convenient methods for concurrently determining visible and near-infrared (NIR) radiation using these cameras have not been developed. Two Nikon Coolpix 4300 digital cameras were evaluated in tandem to determine the effectiveness of a cross-camera calibration procedure that would allow concurrent use of an unmodified digital camera and a NIR-sensitive digital camera without preset shutter speeds or aperture settings. The NIR-sensitive camera was modified to detect NIR radiation by replacing the internal hot mirror with a Hoya RM72 filter. Each camera was calibrated at five exposure levels using a Gretag-Macbeth ColorCheckerTM reflectance panel, and raw camera brightness values were converted to relative reflectance by exposure compensation equations. The method was tested on a series of 26 diffuse reflectance targets, which also yielded the same exposure compensation relationships. The relationship between camera channel brightness and target reflectance was nonlinear within each exposure, but sensitivity was linear between exposures. The procedure was tested on 36 cotton plots (Gossypium hirsutum) in an irrigation study in 2006. Images obtained on eight dates during the season were corrected for exposure and converted to relative reflectance values. The normalized difference vegetation index (NDVI) values from the plots were then compared with ground-based spectrometer measurements of NDVI. Corrected camera-based NDVI values were closely correlated with the spectrometer NDVI values (r2 = 0.72), suggesting that the camera system can more consistently estimate crop reflectance characteristics if exposure compensation is applied.