Measurements Of Water Vapor Content Research Articles

Estimation of errors of the spectral method for measuring the concentration of water vapor and moisture reserves in the surface layer of the Earth’s atmosphere

A method for passive measurements of water vapor concentration in the atmosphere in the presence of solar radiation has been proposed and tested. The location of the measurements is the northeast of the Moscow region. When processing the results of measurements carried out on a single water absorption line, a coincidence of experimental data and data obtained from direct meteorological measurements with an error of no more than ~7.5 % was revealed. It was also found that on the water absorption line in the region of 1653 nm, the interfering factor is the nearby methane absorption line, which introduces a systematic error in the measurement results, and the results turn out to be underestimated. A possible reason is that the absorption cross section of methane molecules is ~4 orders of magnitude larger than that of water vapor molecules and light radiation is absorbed to a greater extent by methane, reducing the fraction of absorption of water vapor at a wavelength close to the methane absorption line. Compensatory corrections have been introduced to determine the concentration and moisture content in the atmospheric column with an accuracy of several percent at this wavelength. The proposed technique allows both long-term monitoring of concentration and moisture content in the atmosphere and obtaining operational information in real time. The results of the measurements performed are, on average, consistent with the results of measurements obtained using radiometers operating in the ultrahigh frequency range.

Droplet Growth or Evaporation Does Not Buffer the Variability in Supersaturation in Clean Clouds

Abstract Water vapor supersaturation in clouds is a random variable that drives activation and growth of cloud droplets. The Pi Convection–Cloud Chamber generates a turbulent cloud with a microphysical steady state that can be varied from clean to polluted by adjusting the aerosol injection rate. The supersaturation distribution and its moments, e.g., mean and variance, are investigated for varying cloud microphysical conditions. High-speed and collocated Eulerian measurements of temperature and water vapor concentration are combined to obtain the temporally resolved supersaturation distribution. This allows quantification of the contributions of variances and covariances between water vapor and temperature. Results are consistent with expectations for a convection chamber, with strong correlation between water vapor and temperature; departures from ideal behavior can be explained as resulting from dry regions on the warm boundary, analogous to entrainment. The saturation ratio distribution is measured under conditions that show monotonic increase of liquid water content and decrease of mean droplet diameter with increasing aerosol injection rate. The change in liquid water content is proportional to the change in water vapor concentration between no-cloud and cloudy conditions. Variability in the supersaturation remains even after cloud droplets are formed, and no significant buffering is observed. Results are interpreted in terms of a cloud microphysical Damköhler number (Da), under conditions corresponding to , i.e., the slow-microphysics regime. This implies that clouds with very clean regions, such that is satisfied, will experience supersaturation fluctuations without them being buffered by cloud droplet growth. Significance Statement The saturation ratio (humidity) in clouds controls the growth rate and formation of cloud droplets. When air in a turbulent cloud mixes, the humidity varies in space and time throughout the cloud. This is important because it means cloud droplets experience different growth histories, thereby resulting in broader size distributions. It is often assumed that growth and evaporation of cloud droplets buffers out some of the humidity variations. Measuring these variations has been difficult, especially in the field. The purpose of this study is to measure the saturation ratio distribution in clouds with a range of conditions. We measure the in-cloud saturation ratio using a convection cloud chamber with clean to polluted cloud properties. We found in clouds with low concentrations of droplets that the variations in the saturation ratio are not suppressed.

Dual-Pump Vibrational Coherent Anti-Stokes Raman Scattering System Developed for Simultaneous Temperature and Relative Nitrogen–Water Vapor Concentration Measurements

Simultaneous gas phase temperature and water vapor concentration measurement are important to understand reacting flows such as combustion or gas reforming processes. Here, coherent anti-Stokes Raman scattering (CARS) offers the possibility for non-intrusive measurements with a high temporal and spatial resolution. Therefore, this work demonstrates the simultaneous measurement of temperature and relative water vapor–nitrogen concentrations by using dual-pump vibrational coherent anti-Stokes Raman scattering (DPVCARS). A calibration procedure is developed for a temperature range of 473 K to 673 K and a water vapor concentration of 24% to 46% at ambient pressure. This setup is tested with 500 CARS single pulse spectra taken in a gas cell at a known temperature and concentration. Based on these results, information about precision and accuracy can be delivered.

Water vapor concentration measurements in high purity gases by means of comb assisted cavity ring down spectroscopy

Water vapor concentration measurements in high purity gases by means of comb assisted cavity ring down spectroscopy

A fast sensor for non-intrusive measurement of concentration and temperature in turbine exhaust

Accurate and rapid measurement of water vapor concentration and temperature in the exhaust of gas turbine engines is critical for monitoring their health and operational performance. To monitor the two parameters simultaneously, a non-intrusive sensor based on tunable diode laser absorption spectroscopy is developed using 8 laser beams targeting 3 transitions of water vapor. The sensor has in situ validated on a commercial auxiliary power unit. Seven parallel laser beams at 5000.2 cm−1 are 6.3 mm spaced at the plume boundary to characterize the edge effect between hot exhaust plume and cold surrounding flow. One beam, operating at the dual wavenumbers of 7185.6 cm−1 and 7444.4 cm−1 penetrates the plume through centerline to measure temperature via ratio thermometry. Then, this temperature information is used to obtain the concentration of water vapor. A temporal resolution of 4 ms is achieved for the 8-beam measurement, enabling high-speed and simultaneous quantification of the edge effects and the plume parameters. Results indicate water vapor concentration and temperature in the exhaust measured by the developed sensor are highly consistent with the traditional benchmarks, e.g., extractive sampling and thermocouples, with a difference of 0.02% and 3 °C, respectively. Enabled by its continuous millisecond-level measurements, the sensor, for the first time, reveals hidden engine behaviors and combustion dynamics that are unable to be observed by the traditional methods, thus facilitating next-generation real-time gas turbine engine control towards low emissions.

Measurements of Atmospheric Water Vapor by a 1.316 μm Optical Fiber Laser Heterodyne Radiometer

A passive optical fiber laser heterodyne radiometer prototype with a semiconductor laser near 1.316 μm as the local oscillator was built, parameters of the prototype have been optimized. Using the prototype, the water vapor concentration in the atmospheric column was measured with a spectral resolution of 0.009 cm−1 in late October and early November of 2020, the collection time was approximately 3 min, and the signal-to-noise ratio was better than 120. The water vapor column concentration and profiles were inversed based on the optimal estimation method. Compared with the measurement of the Fourier transform spectrometer (EM27/SUN) which was performed simultaneously, the inversion results deviated by less than 14%, and the variation trend of the water vapor concentration showed good consistency. It is demonstrated that the 1.316 μm optical fiber laser heterodyne radiometer possesses good stability and accuracy in the field measurement of atmospheric water vapor concentration.

Simultaneous measurement of H2O concentration and effective absorption optical path length under unknown optical path length condition based on a single spectral line

Quantitative gas measurement under the condition of unknown optical path length is a challenge in laser absorption spectroscopy technology field. In this paper, we proposed a tunable diode laser absorption spectroscopy line shape analysis (TDLAS-LSA) method for simultaneous measurement of water vapor concentration and effective optical path length (EOPL) under unknown optical path conditions. A single H2O absorption line near 1383.9 nm (7226.02 cm−1) was selected, and its line strength, self-broadening coefficient and temperature-dependence coefficient were measured experimentally to improve the HITRAN databases. The Lorentz broadening and line area were accurately extracted by Hartmann-Tran profile (HTP) fitting, and the gas concentration and EOPL were calculated based on the spectral line shape analysis method. Eight concentrations of water vapor in the range of 146 ppm ∼ 4.39% were measured experimentally, and the maximum average deviation between the TDLAS-LSA method and the commercial sensor was less than 7.1%. Comparing the EOPL with mechanical measurement, the maximum deviation of multiple measurements is less than 5.7%. The results showed that the TDLAS-LSA method can effectively perform gas sensing under unknown optical path conditions, and has great application potential in low-cost, in-situ and multi-parameter simultaneous measurement.

Supercontinuum lidar for industrial process analysis

Real-time monitoring of flue gas parameters in combustion processes is central to the optimization of the process efficiency and reduction of pollutants emission. We report simultaneous measurement of the average water vapor temperature and concentration over a 9 m distance in a full-scale industrial boiler by broadband lidar employing a custom supercontinuum source covering the wavelengths of ro-vibrational absorption of water molecules at 1.2 – 1.55 µm. The measured average temperature and concentration are in excellent agreement with reference measurements. We also take advantage of the backscattering from the aerosol particles present in the boiler to map the water vapor concentration profile in the boiler up to a distance of 2.7 m with a spatial resolution of 30 cm. Our results open novel perspectives for 3D profiling of temperature and gas concentration in industrial environments.

Performance of Earth Troposphere Calibration Measurements With the Advanced Water Vapor Radiometer for the Juno Gravity Science Investigation

AbstractThe performance of an atmospheric water vapor radio path delay measurement and correction is reported using observations of the Juno Spacecraft during gravity field mapping of Jupiter. The Juno Gravity Science instrument measures the Doppler shift on the radio signals between the Juno spacecraft and the Earth‐based observing stations of NASA's Deep Space Network (DSN) during times of closest approach to Jupiter in order to map Jupiter's gravity field. These Doppler measurements are affected by noise sources between the spacecraft and DSN which include charged particles plasma and Earth's troposphere. A pair of redundant Advanced Water Vapor Radiometers (AWVR) co‐located at the DSN's DSS‐25 antenna in Goldstone, CA measure the brightness temperatures at the 22.2, 23.8 and 31.4 GHz spectral lines for water vapor content in Earth's atmosphere. The measurements of water vapor content are reduced into a measurement of radio path delay, which provides high‐precision calibrations of tropospheric noise on the radio links. Analyses of AWVR measurements show that spacecraft tracking errors, after removing other measurable errors from charged particles, are reduced by 46% on average and by as much as 70%, depending on local weather conditions near the Goldstone site.

TDLAS measurements of temperature and water vapor concentration in a flameless MILD combustor

We performed non-intrusive tunable diode laser absorption spectroscopy measurements of the temperature (T) and water vapor concentration (X H2O) on a moderate or intense low-oxygen dilution combustion chamber. The combustor was operating in flameless mode by axially injecting fuel and air at high speeds through separate nozzles, thereby creating a recirculating flow of combusted gas. A pair of water vapor absorption lines near 7185.6 and 7444.36 cm−1 was used to acquire axial absorbance profiles along the height of the combustor. The axial profiles of T and X H2O were first derived using two-line thermometry measurements. Then the T profiles were estimated from each of the single absorption line measurements by assuming spatial uniformity of X H2O. Compared to a thermocouple temperature measured at the combustor outlet, the temperatures given by the two-line thermometry were under-estimated whereas the thermocouple temperature was in between the T range given by the single-line thermometry. Importantly, the measurement successfully revealed that the axial profiles of T and X H2O were mostly flat certainly due to the strong recirculation of the hot combustion gas; however, the different temperature values at a given height implied the existence of a radial temperature gradient in the combustor.

Temperature and concentration measurements in a high-pressure gasifier enabled by cepstral analysis of dual frequency comb spectroscopy

High-pressure gasification processes are important for conversion of solid materials into gaseous fuels and other chemicals. Laser absorption diagnostics are an important means to study these processes, but are challenging to implement due to the extreme temperatures and pressures present in the system. Here, we combine broadband high-resolution dual-comb spectroscopy with an advanced spectral absorption database and a new means for baseline-free absorption spectroscopy analysis to enable measurements of temperature and water vapor concentration in the core of an entrained flow gasifier operating at up to 1700 K and 15 bar. The dual-comb spectrometer measures the absorption of water vapor from 6800 to 7150 cm−1 with a point spacing of 0.0067 cm−1. The bandwidth is helpful for resolving the complex, congested absorption fingerprint of water vapor that is used to determine the species concentrations and temperature. We interpret the spectrum with absorption models based on a database measured under carefully controlled high-temperature conditions with the dual-comb spectrometer. The database includes the pressure broadening, shift, and temperature dependence of these parameters for water vapor in argon, which is the gasifier bath gas. Finally, fitting the absorption model to the data is enabled by modified free induction decay analysis, which is an approach for quantitatively obtaining species and temperature information without determining the baseline intensity of the spectrometer. The baseline-free approach is crucial to success in this environment, where there are no non-absorbing regions of the spectrum to anchor the normalization of the laser intensity as in traditional direct absorption spectroscopy. We demonstrate good agreement with temperatures measured on the reactor core via optical pyrometry, and show that water vapor concentrations in the reactor core did not reach the expected system set points during some experiments.

In-situ measurement of water-vapor in fire environments using a real-time tunable diode laser based system

A robust tunable diode laser absorption spectroscopy (TDLAS) based system is developed and deployed to make real-time water-vapor concentration measurements in quasi-controlled live-fire experiments conducted in firefighter training props. This system targets the 1392.5 nm (7181.15 cm−1) water-vapor absorption line while employing a multi-tier detection sensitivity scheme that allows for measurements at multiple locations in fire environment through varying smoke obscuration levels. Temperature-corrected absorbance values are compared to HITRAN simulations to quantify water-vapor concentration. Upon validation in laboratory setting, the impact of firefighter hose stream application on water-vapor concentration is studied. Comparative effects of training structures (metal, concrete and drywall-lined) and fuel-loads (pallet/straw, lightweight furnishings and pallet/straw/oriented-strand-board (OSB)) on water-vapor concentration are characterized. Despite small increase in water-vapor concentration due to suppression, the post-suppression concentrations are found to be comparable or lower than the corresponding maximum pre-suppression concentrations in all scenarios except the metal structure. Irrespective of the structure, highest temperature and water-vapor concentrations are measured with pallet/straw/OSB fuel-load. Under identical fuel-loads, the drywall structure scenarios generate highest water-vapor concentration. Peak water-vapor concentrations are measured post-suppression in typical training structures (near-floor and crawling levels), but prior to suppression in the structure/fuel package combination that simulated a typical residential fire scenario.

Research on laser water vapor concentration detection technology in the air-sea flux observation

In the observation of water vapor flux at air-sea interface, the collection frequency of water vapor concentration is more than 10 Hz. High-speed and high-precision measurement of water vapor concentration is an urgent problem to be solved in the observation of water vapor flux at air-sea interface. The ratio of the peak-peak value of second harmonic to the average value of first harmonic is used to measure water vapor concentration based on tunable diode laser absorption spectroscopy. The sensitivity of laser water vapor concentration detection equipment caused by marine salt fog and dust is reduced through precise optical design, and the water vapor concentration at the air-sea interface is calculated using a binary polynomial fitting algorithm. The response frequency of the laser water vapor concentration analyzer is 40 Hz. The water vapor concentration values from the laser water vapor concentration analyzer and LI-7500 CO2/H2O gas analyzer are collected synchronously in real time using LabVIEW software. The comparison results show that they have good consistency in the trend and response speed of water vapor concentration, and the measurement deviation of water vapor concentration is within ±1%. The experimental results show that it can meet the needs of high-speed, high-precision measurement of water vapor concentration in the air-sea interface water vapor flux observation.

Total Content of Water Vapor Over Yamal During the Warm Period of the Year

The spatial distribution of total water vapor content over the Yamal Peninsula and adjacent territories was analyzed using data of four-year-long measurements from the European Envisat satellite during warm periods of the year (June-August). Special attention was given to water vapor variations at the transition from little to abundant water-bearing areas of the underlying surface. It was found that for the five selected sites located in a dry tundra and in large water bodies the logarithmic rather than Gaussian form of the distribution functions of total water vapor content turned out to be typical according to the number of its measurements. Each function has at least two modes. The parameters of these modes were calculated and presented, and they are necessary for simulation of climatic conditions in the northern territories. Geometric mean values of total water vapor content over the Gulfs of Gydan and Baidaratsk, and especially over the Gulf of Ob, can be by a factor of 1.5 larger than those for the less water-abundant areas of tundra and have clear boundaries coincident with geographical contours of the water bodies. It is most likely that these boundaries exist at insignificant speeds of surface winds, which is indicative of weak turbulent mixing of the lower air layers. This conclusion is confirmed by results from processing published data of ground-based and satellite observations. For the five sites they were used to calculate and construct the wind roses for all five sections in the same time intervals when the satellite measurements of water vapor content were carried out. Wind rose analysis shows that the average velocity of predominantly N and NW winds on all the selected sites at a height of 10 m above the underlying surface are 5–6 m/s with a standard deviation of 1.5 m/s. Additional data are presented on the form of the distribution function of various parameters in other natural environments (water bodies and vegetation) which give support to what has been said above about water vapor.

High speed temperature, pressure, and water vapor concentration measurement in explosive fireballs using tunable diode laser absorption spectroscopy

Results from the design, development, and testing of a probe capable of making quantitative measurements of temperature, pressure, and water vapor concentration in near field explosive detonations are presented. This work extends established tunable diode laser absorption techniques to the field of explosive and energetic materials diagnostics with improved temporal resolution. Simultaneous measurement of temperature, pressure, and water vapor concentration were successfully measured at 30 kHz in a constant volume explosion at a standoff distance of 52 cm from 40 g of PBXN-5. Explosive testing was conducted in the 1.81 m3 blast chamber at the University of Illinois at Urbana-Champaign Energetic Materials Diagnostics Lab. Measured values compared very well to theoretical calculations for shocked air during the blast phase as well as late-time quasi static conditions. Data show a discrepancy between pressure and temperature equilibration times. This observation is attributed to comparatively slow mass diffusion of explosive products and thermal diffusion of heat relative to pressure equilibration through shock reflections.

A Coated Spherical Microresonator for Measurement of Water Vapor Concentration at PPM Levels in Very Low Humidity Environments

This paper presents a novel approach to measurements of low relative humidity (RH) values based on the whispering gallery modes (WGMs) effect in a small silica microsphere coated with a thin layer of Agarose hydrogel. The light from a narrow-linewidth tunable laser with a few GHz tuning range is launched into an adiabatic tapered fiber, which excites WGMs in the Agarose layer via evanescent coupling. Adsorption and desorption of water vapor by the Agarose layer in response to changes in ambient humidity lead to changes in the layer's refractive index, which in turn leads to a spectral shift of the WGM resonances. We experimentally demonstrate the WGMs spectral shift over a range of RH values from 1%RH to 25%RH. The proposed sensor displays linear response and is capable of measurement of low concentrations of water vapor (corresponding to about 11.7 ± 0.32 ppm water molecules in air). In addition, the proposed sensor offers the advantages of a very small form factor and good repeatability. Detailed studies of the sensor stability, cross sensitivity to temperature, response times, and hysteresis are also presented.

Measurement of Water Vapor Concentration in Narrow Channel of PEFC Using Fiber-Optic Sensor Based on Laser Absorption Spectroscopy

To achieve high performance and long-term operation of polymer electrolyte fuel cell (PEFC), it is essential to understand and control water transports in operating fuel cell. In the previous studies, water distributions along flow channels were investigated using micro gas chromatograph (mGC) [1-2]. Although GC method enables to analyze water vapor concentration with high accuracy, it takes a long time (at least two minutes) to collect a gas sample and identify a species. On the other hand, several researchers have applied tunable diode laser absorption spectroscopy (TDLAS) technique to gas analysis in PEFCs [3-4]. TDLAS is one of the high-sensitive absorption spectroscopy techniques which measure the absorbance of a species and identify its concentration using infrared diode laser. Since laser beam is directly injected into gas channel of PEFC, in-situ monitoring of water vapor concentration can be performed on operational fuel cells with a high time resolution of millisecond. The authors have now developed a fiber-optic gas sensor based on TDLAS to apply it to the measurement of water vapor concentration in flow channels of working PEFCs. The introduction of small-size fiber-optic sensors enables in-situ laser diagnostics within millimeter-scale narrow channels. In this study, a transmission/reception integrated fiber-optic probe is newly developed to detect absorption spectra of water in gas channels of PEFCs. This novel probe is compactly composed of one light-projecting fiber and six receiving fibers, which are coaxially arranged. Since multiple output signals detected by using six photodiodes are synthesized, the optical fringe noise in them can be effectively canceled. Even if the fringe noise tends to be generated inside narrow channels, the high-resolution absorption spectra with better S/N ratio can be obtained by the signal synthesizing. Furthermore, the TDLAS system with the above-mentioned fiber-optic probe is constructed as shown in Fig. 1, and the concentration measurement of water vapor was tentatively attempted using a simulated flow cell. In this system, the triangular-wave laser beam modulated at the high frequency of 10 kHz is emitted from a DFB laser diode (wavelength: 1392 nm) and injected into the straight gas flow channel (30 mm length, 1.5 mm width, 1.5 mm depth) of the simulated cell through the fiber-optic probe. Some reflected lights from the gas channel are detected at six photodiodes and converted to the electric signals. Subsequently, the synthesized output signal is transmitted to a lock-in amplifier and the high-sensitive harmonic spectra are obtained by phase-sensitive detection. The method to quantify the water vapor concentration in the channel from the measured spectrum data is also proposed. The simulated flow cell is fabricated by stainless steel plates. The humidified oxygen is fed into the gas channel at the flow rate of 200 mL/min. Fig. 2 presents the second-harmonic (2f) spectra of water obtained from the TDLAS measurement in the simulated flow cell at 70 deg. C. The mole fraction of water vapor is changed from 0.3 to 25.7%. The vertical axis shows the intensity of 2f signal, and the horizontal axis shows the wavelength. At the low water concentration of 0.3-8.9 mol%, the peak-valley height of 2f absorption spectrum increases with an increase in water concentration. On the other hand, when the concentration of water vapor is higher than 14.3 mol%, the peak-valley height of 2f signal gradually decreases with increasing water mole fraction. Since the relationship between the water mole fraction and the peak-valley height of 2f spectrum is not monotonous, the water concentration cannot be quantitatively estimated only by the 2f spectrum data. The authors propose the improved method for the accurate and effective quantification of water vapor concentration with the use of 2f and 4f absorption spectra. As a result of the spectral analysis, it was found that the peak-valley ratio of 2f and 4f spectra exponentially increases with water mole fraction. The water vapor concentration can be estimated from the 2f/4f peak-valley ratio. In addition, it was revealed that the measurement accuracy of water vapor mole fraction is less than 0.5% at 70 deg. C. These results suggest that the fiber-optic TDLAS sensor has the ability to accurately monitor in-situ water transports within narrow channels of actual fuel cells.

Water vapor concentration measurements using TDALS with wavelength modulation spectroscopy at varying pressures

PurposeAs measurement results of optical gas sensors are constantly affected by the pressure of a target gas, approaches must be taken to modify the results. The purpose of this paper is to compare the traditional measurement method with the new measurement system. At the same time, measurement results of the two systems under different pressures are presented for comparison of the detection performance.Design/methodology/approachA theoretical model of line shape function and its impact on the measured results is presented, which is based on direct absorption and wavelength modulation spectroscopy (WMS) for gas concentration detection under different pressures. Methods of linear fitting and result modification have been illustrated and compared. A new testing system with the result modification method used for water vapor concentration detection under different pressures between 1 and 7 atm is applied. With an additional pressure sensor placed in the gas cell and calibration performed, relationships between the amplitude of the second harmonic and concentration of the target gas under different pressures can be obtained.FindingsAmplitude detection can be used for concentration detection regardless of the change in pressure for the method of direct absorption. Although, WMS with second harmonic detection is not enough. Two methods are presented and compared with WMS under different pressures. Moreover, the result modification method shows better performance as computation is significantly reduced.Originality/valueThe comparison between linear fitting and the result modification method with WMS under different pressures is firstly presented. At the same time, a new testing system with better performance for water vapor concentration detection under different pressures is presented as well.

THE NASA AIRBORNE TROPICAL TROPOPAUSE EXPERIMENT: High-Altitude Aircraft Measurements in the Tropical Western Pacific.

Abstract The February–March 2014 deployment of the National Aeronautics and Space Administration (NASA) Airborne Tropical Tropopause Experiment (ATTREX) provided unique in situ measurements in the western Pacific tropical tropopause layer (TTL). Six flights were conducted from Guam with the long-range, high-altitude, unmanned Global Hawk aircraft. The ATTREX Global Hawk payload provided measurements of water vapor, meteorological conditions, cloud properties, tracer and chemical radical concentrations, and radiative fluxes. The campaign was partially coincident with the Convective Transport of Active Species in the Tropics (CONTRAST) and the Coordinated Airborne Studies in the Tropics (CAST) airborne campaigns based in Guam using lower-altitude aircraft (see companion articles in this issue). The ATTREX dataset is being used for investigations of TTL cloud, transport, dynamical, and chemical processes, as well as for evaluation and improvement of global-model representations of TTL processes. The ATTREX data are publicly available online (at https://espoarchive.nasa.gov/).

Measurement of the parameters of non-stationary gas flows by diode laser absorption spectroscopy in case of high temperature and high pressure

Experimental version of diode laser absorption spectrometer (DLAS) for contactless measurements of temperature and water vapor concentration in supersonic gas flows is developed. The spectrometer can be used for the measurements of temperature up to 2500 K and total pressure up to 3 atm. The technique is based on the registration of the transient absorption spectra of a target molecules and fitting of the experimental spectra by the simulated ones constructed using the spectroscopic databases. The temperature is inferred from the ratio of the intensities of the absorption lines with different low energy levels. In gas media with the above parameters the absorption lines are broadened which demands the use of two diode lasers (DL) working in different spectral ranges. The software for selection of the optimal line combinations was developed. The combination of two strong lines in the spectral ranges 1.39 μ and 1.34 μ was selected as the optimal one. The efficiency of the developed technique was exemplified in the first set of the experiments in conditions of real propulsion in Zhukovsky Central Aerohydrodynamic Institute (TsAGI) for the temperatures within (500-2200) К range and total pressure up to 3 atm.