Microwave Temperature Profiler Research Articles

The Microwave Temperature and Humidity Profiler: Description and Preliminary Results.

This manuscript presents the Microwave Temperature and Humidity Profiler (MTHP), a dual-band spectroradiometer designed for measuring multi-incidence angle temperature and humidity atmospheric profiles from an aircraft platform. The MTHP bands are at 60 GHz for measuring the oxygen complex lines, therefore at this band, MTHP has a hyperspectral radiometer able to provide 2048 channels over an 8 GHz bandwidth, and 183 GHz for measuring water vapor, which only uses four channels since this absorption band's spectral richness is simpler. The MTHP builds upon the Microwave Temperature Profiler (MTP) with the inclusion of the hyperspectral radiometer. The instrument's design, components, and calibration methods are discussed in detail, with a focus on the three-point calibration scheme involving internal calibration loads and static air temperature readings. Preliminary results from the Technological Innovation into Iodine and GV aircraft Environmental Research (TI3GER) campaign are presented, showcasing the instrument's performance during flights across diverse geographical regions. The manuscript presents successful antenna temperature measurements at 60 GHz and 183 GHz. The hyperspectral measurements are compared with a simulated antenna temperature using the Atmospheric Radiative Transfer Simulator (ARTS) showing an agreement better than R2 > 0.88 for three of the flights analyzed. Additionally, the manuscript draws attention to potential Radio Frequency Interference (RFI) effects observed during a specific flight, underscoring the instrument's sensitivity to external interference. This is the first-ever airborne demonstration of a broadband and hyperspectral multi-incidence angle 60 GHz measurement. Future work on the MTHP could result in an improved spatial resolution of the atmospheric temperature vertical profile and, hence, help in estimating the Planetary Boundary Layer (PBL) with better accuracy. The MTHP and its hyperspectral multi-incidence angle at 60 GHz have the potential to be a valuable tool for investigating the PBL's role in atmospheric dynamics, offering insights into its impact on Earth's energy, water, and carbon cycles.

Observations of the urban boundary layer in a cold climate city

Cold environment supports a large diversity of local climates. Among them, urban climates in northern cities stand out for their pronounced warm temperature anomaly known as the Urban Heat Island (UHI). UHI in northern cities has been already studies through satellite images and in-situ observations in the urban canopy layer (UCL). Yet, the vertical structure of the urban atmospheric boundary layer (UBL) has not been studied there. This work presents new observations of UBL in Nadym – a sub-Arctic Siberian city. During several intensive observing periods we run simultaneous registration of urban and rural meteorological parameters with unmanned drones, a microwave temperature profiler and a dense network of ground-based sensors. The data analysis reveals details of UHI development in the UCL and UBL, and links together horizontal urban-rural canopy-layer temperature differences, boundary layer stability, and UHI vertical extent. We show that during strong temperature inversions, UBL is less stratified than its rural counterpart, but it still remains very thin and limited in height by a few tens of meters. The observations disclose that the ground-based (50 m – 100 m above ground) temperature inversion is one of the strongest control factors for UHI in cold climate conditions in winter.

Verification of vertical temperature profiles in the COSMO and ICON models with available observational data

This paper presents results of numerical estimates of vertical temperature profiles in the COSMO and ICON NWP models. Data from two vertical profilers, an MTP-5 microwave temperature profiler and a classic AVK-type radiosonde, are used for the estimates. Mean errors, correlation coefficients, and root-mean-square errors are calculated for different seasons. The simulation results are analysed depending on configurations of the horizontal resolution of the models and between the models. The estimates are plotted, and comparisons are made between the models using each of the measurement types: between different measurements for each model. The response to spatial variability in the measurements and model grid cells is assessed. Conclusions are formulated by comparing the quality of reproduction of the atmospheric boundary layer between the models and the model configurations. The findings provide useful information for the interpretation of modeling results by forecasters.

Microwave-assisted calcination of spodumene for efficient, low-cost and environmentally friendly extraction of lithium

To utilize the advantages of microwave-assisted calcination over conventional heating, this work studied the effect of microwave power on phase transformation and leachability of spodumene. X-ray diffraction (XRD) and scanning electron microscope (SEM) were utilized to characterize the phase transformation and structural changes of spodumene calcined by both microwave and conventional heating methods. Results showed that the effect of microwave power on both phase transformation and leachability of spodumene is significant. The optimum lithium recovery through the microwave calcination-acid roasting-leaching process reached 97% at 2.0 kW microwave power, comparable with that of conventional heating. Besides a more rapid, less energy-consuming, and free greenhouse-gas-emission calcination, microwave heating also resulted in lower recovery values of Fe, Na, and Ca in the leaching process, gaining an advantage in downstream purification processes. The microwave temperature profiles of spodumene, and characterization results confirmed that α-spodumene started to transfer into γ- and β-spodumene at around 900 °C.

Measurement characteristics of an airborne microwave temperature profiler (MTP)

Abstract. The microwave temperature profiler (MTP), an airborne passive microwave radiometer, measures radiances, recorded as counts and calibrated to brightness temperatures, in order to estimate temperature profiles around flight altitude. From these data, quantities such as potential temperature gradients and static stability, indicating the state of the atmosphere, can be derived and used to assess important dynamical processes (e.g., gravity waves or stability assessments). DLR has acquired a copy of the MTP from NASA–JPL, which was designed as a wing-canister instrument and is deployed on the German High Altitude LOng range research aircraft (HALO). For this instrument a thorough analysis of instrument characteristics has been made in order to correctly determine the accuracy and precision of MTP measurements. Using a laboratory setup, the frequency response function and antenna diagram of the instrument were carefully characterized. A cold chamber was used to simulate the changing in-flight conditions and to derive noise characteristics as well as reliable calibration parameters for brightness temperature calculations, which are compared to those calculated from campaign data. The MTP shows quite large changes in the instrument state, imposing considerable changes in calibration parameters over the course of a single measurement flight; using a built-in heated target for calibration may yield large errors in brightness temperatures due to a misinterpretation of the measured absolute temperature. Applying the corrections presented herein to the calibration parameter calculations, the measurement noise becomes the dominant source of uncertainty and it is possible to measure the brightness temperatures around flight level (closely related to the absolute temperature close to the instrument) with a precision of 0.38 K. Furthermore, radiative transfer simulations, using the Py4CAtS package in a pencil-beam approach, indicate that the altitude range of the sensitivity of the MTP instrument can be increased by applying a modified measurement strategy. This is the first time such an extensive characterization of an MTP instrument, including a thorough calibration strategy assessment, has been published. The presented results, relevant for the wing-canister design of the MTP instrument, are important when processing MTP data: knowledge of the relevant uncertainties and instrument characteristics is essential for retrieval setup and is mandatory to correctly identify and interpret significant atmospheric temperature fluctuations.

Study of surface-based temperature inversions in the city of Nadym (Western Siberia) with direct measurements and numerical simulation

Frequent surface-based inversions are persistent features of climate in the Arctic and, in particular, in its Russian part. Most favourable conditions for temperature inversion formation during the winter period in this region are observed. Surface-based inversions formed in cities are most interesting for research, because of their impact on people’s health. Besides, “urban” surface-based inversions differ from “rural” ones, because of interactions with the urban heat island (UHI). Actually, urban surface-based inversions in the Arctic are weakly understood due to poor meteo monitoring equipment of most Arctic regions and because the reanalysis resolution is too low for the cities. To estimate the frequency of surface-based inversions and spatial distributions in the city of Nadym (Western Siberia), measurements with gradient complexes during the period from 18.12.2018 to 15.10.2019 have been conducted, and a numerical experiment with a model Advanced Research WRF (ARW) has been performed for the coldest days of the period. In the research, first statistic microclimatic data of vertical temperature distributions in the city of Nadym have been obtained. Such model experiments are realized for that region, and the results obtained for the rural area are compared with microwave temperature profiler MTP-5 measurements.

Wind–Temperature Regime and Wind Turbulence in a Stable Boundary Layer of the Atmosphere: Case Study

The paper presents the results of probing the stable atmospheric boundary layer in the coastal zone of Lake Baikal with a coherent Doppler wind lidar and a microwave temperature profiler. Two-dimensional height–temporal distributions of the wind velocity vector components, temperature, and parameters characterizing atmospheric stability and wind turbulence were obtained. The parameters of the low-level jets and the atmospheric waves arising in the stable boundary layer were determined. It was shown that the stable atmospheric boundary layer has an inhomogeneous fine scale layered structure characterized by strong variations of the Richardson number Ri. Layers with large Richardson numbers alternate with layers where Ri is less than the critical value of the Richardson number Ricr = 0.25. The channels of decreased stability, where the conditions are close to neutral stratification 0 < Ri < 0.25, arise in the zone of the low-level jets. The wind turbulence in the central part of the observed jets, where Ri > Ricr, is weak, increases considerably to the periphery of jets, at heights where Ri < Ricr. The turbulence may intensify at the appearance of internal atmospheric waves.

Skills of Thunderstorm Prediction by Convective Indices over a Metropolitan Area: Comparison of Microwave and Radiosonde Data

In this work, we compare the values of 15 convective indices obtained from radiosonde and microwave temperature and water vapor profiles simultaneously measured over Nizhny Novgorod (56.2°N, 44°E) during 5 convective seasons of 2014–2018. A good or moderate correlation (with coefficients of ~0.7–0.85) is found for most indices. We assess the thunderstorm prediction skills with a lead time of 12 h for each radiosonde and microwave index. It is revealed that the effectiveness of thunderstorm prediction by microwave indices is much better than by radiosonde ones. Moreover, a good correlation between radiosonde and microwave values of a certain index does not necessarily correspond to similar prediction skills. Eight indices (Showalter Index, Maximum Unstable Convective Available Potential Energy (CAPE), Total Totals index, TQ index, Jefferson Index, S index, K index, and Thompson index) are regarded to be the best predictors from both the true skill statistics (TSS) maximum and Heidke skill score (HSS) maximum points of view. In the case of radiosonde data, the best indices are the Jefferson Index, K index, S index, and Thompson index. Only TSS and HSS maxima for these indices are close to the microwave ones, whereas the prediction skills of other radiosonde indices are essentially worse than in the case of microwave data. The analysis suggests that the main possible reason of this discrepancy is an unexpectedly low quality of radiosonde data.

A dataset of tracer concentrations and meteorological observations from the Bolzano Tracer EXperiment (BTEX) to characterize pollutant dispersion processes in an Alpine valley

Abstract. The paper describes the dataset of concentrations and related meteorological measurements collected during the field campaign of the Bolzano Tracer Experiment (BTEX). The experiment was performed to characterize the dispersion of pollutants emitted from a waste incinerator in the basin of the city of Bolzano, in the Italian Alps. As part of the experiment, two controlled releases of a passive gas tracer (sulfur hexafluoride, SF6) were performed through the stack of the incinerator on 14 February 2017 for two different time lags, starting, respectively, at 07:00 and 12:45 LST. Samples of ambient air were collected at target sites with vacuum-filled glass bottles and polyvinyl fluoride bags, and they were later analyzed by means of a mass spectrometer (detectability limit 30 pptv). Meteorological conditions were monitored by a network of 15 surface weather stations, 1 microwave temperature profiler, 1 sodar and 1 Doppler wind lidar. The dataset represents one of the few examples available in the literature concerning dispersion processes in a typical mountain valley environment, and it provides a useful benchmark for testing atmospheric dispersion models in complex terrain. The dataset described in this paper is available at https://doi.org/10.1594/PANGAEA.898761 (Falocchi et al., 2019).

Experimental and computational investigation of heat transfer in a microwave-assisted flow system

Microwave technology is gaining popularity as a tool for chemical process intensification and an alternative to conventional heating. However, in flow systems non-uniform temperature profiles are commonly encountered and hence methods to characterise and improve them are required. In this work, we studied the effects of various operational parameters - microwave power, inlet flow rate, tube orientation and pressure - on the electric field and temperature profiles of water flowing in a PTFE tube (2.4 mm internal diameter), placed in a commercial single-mode microwave applicator. A finite element model was developed to estimate the longitudinal temperature profiles and the absorbed microwave power, while in situ temperature monitoring was performed by a fibre optic probe placed at multiple locations inside the tube. The water temperature inside the tube increased by increasing the microwave power input and temperature profiles stabilised beyond 20 W, while the percentage absorbed microwave power showed the inverse trend. When changing the tube orientation or decreasing the inlet flow rate, microwave absorption decreased significantly. When the pressure was increased to 2.3 bara, water temperature increased by ∼20 °C. Results from this study provide valuable insights on achievable temperature profiles and energy efficiency of microwave-assisted flow synthesis systems.

Experience in the quadcopter-based meteorological observations in the atmospheric boundary layer

Recent developments of the unmanned aerial vehicles (UAVs) opens wide opportunities for their application for in-situ meteorological measurements in the atmospheric boundary layer (ABL). In this study we consider the experience of ABL measurements with a mass-market quadcopter DJI Phantom 4 Pro, equipped with temperature, humidity, pressure and infra-red surface temperature sensors. The quadcopter was used during a field experimental campaign in the northern Russia in winter for several types of measurements: hovering near the automatic weather station for a verification (1); vertical transects within the lowest 500 m in order to obtain the vertical temperature profiles and compare them with observations of the microwave temperature profiler MTP-5HE (2); horizontal transects over an unfreezing polynya (3). Additional verification was performed near the high meteorological mast in Obninsk. Listed experiments have shown that quadcopter-based system is a promising and usable tool for ABL measurements. However, its application requires a multi-step data processing framework, which is presented in this study.

Observations and modelling of downslope windstorm in Novorossiysk

We present a comprehensive study of the three-dimensional structure of the Novorossiysk bora, a severe downslope windstorm on the north-eastern coast of the Black Sea. The analysis is based on observational data obtained from the Russian Hydrometeorological Service, automatic weather stations, sodar system, microwave temperature profiler and 10-m mast. In addition, WRF-ARW simulations are performed to verify and complement the observations. The data permit us to investigate major features of the flow over mountain ridges during several bora episodes. The qualitative and quantitative characteristics of the Novorossiysk bora were compared with those of other downslope winds, such as the Adriatic bora, the Boulder windstorm, and the Alpine foehn.

Assessment of the atmospheric mixing layer height and its effects on pollutant dispersion.

The atmospheric mixing layer height (MLH) is an important parameter of the planetary boundary layer (PBL) because it affects the transportation and dispersion processes of pollutants emitted from different sources. This study investigated the relationship between the surface temperature inversion, elevated temperature inversion, and MLH within the PBL of the Kuwait by collecting and analyzing measurements of the temperature and the air quality of upper air during 2013. The upper air temperature and the MLH were derived using a microwave temperature profiler. Hourly concentrations of SO2, O3, particulate matter (PM10), NO2, CO, NO x , and non-methane hydrocarbons (NMHCs) in ambient air were measured by air quality monitoring stations. The collected data were used to estimate the hourly MLH for the transportation and dispersion of critical pollutants. The results showed that concentrations of SO2 and PM10 have direct correlation with MLH during the day, whereas they have the reverse relationship at night. Conversely, concentrations of CO, NMHCs, and NO x showed negative correlation with MLH during both day and night, whereas concentrations of O3 showed direct correlation with MLH during both day and night. In addition, the relationship between the PBL and concentrations of critical pollutants in residential areas was clarified. These findings indicate the influence of the MLH on SO2 and PM10 is much greater during the day than at night. The findings of the present study could help improve our understanding of the effects of MLH on air quality.

Characteristics of the lower 1000-m atmospheric layer in the area of the Leningrad NPP-2

The calculated aeroclimatic characteristics of the lower 1000-m atmospheric layer needed to study the conditions for the atmospheric diffusion of pollutants are considered. The measurements of temperature profiles with the MTP-5 microwave temperature profiler and the data of weather balloon observations on wind speed and wind direction from the special meteorological station located at the Leningrad NPP-2 (LNPP-2) construction site are used as initial data. The characteristics of the vertical distribution of temperature and wind obtained from the observations in the LNPP-2 construction area and at the Voeikovo upper-air network station are compared.

The Deep Propagating Gravity Wave Experiment (DEEPWAVE): An Airborne and Ground-Based Exploration of Gravity Wave Propagation and Effects from Their Sources throughout the Lower and Middle Atmosphere

Abstract The Deep Propagating Gravity Wave Experiment (DEEPWAVE) was designed to quantify gravity wave (GW) dynamics and effects from orographic and other sources to regions of dissipation at high altitudes. The core DEEPWAVE field phase took place from May through July 2014 using a comprehensive suite of airborne and ground-based instruments providing measurements from Earth’s surface to ∼100 km. Austral winter was chosen to observe deep GW propagation to high altitudes. DEEPWAVE was based on South Island, New Zealand, to provide access to the New Zealand and Tasmanian “hotspots” of GW activity and additional GW sources over the Southern Ocean and Tasman Sea. To observe GWs up to ∼100 km, DEEPWAVE utilized three new instruments built specifically for the National Science Foundation (NSF)/National Center for Atmospheric Research (NCAR) Gulfstream V (GV): a Rayleigh lidar, a sodium resonance lidar, and an advanced mesosphere temperature mapper. These measurements were supplemented by in situ probes, dropsondes, and a microwave temperature profiler on the GV and by in situ probes and a Doppler lidar aboard the German DLR Falcon. Extensive ground-based instrumentation and radiosondes were deployed on South Island, Tasmania, and Southern Ocean islands. Deep orographic GWs were a primary target but multiple flights also observed deep GWs arising from deep convection, jet streams, and frontal systems. Highlights include the following: 1) strong orographic GW forcing accompanying strong cross-mountain flows, 2) strong high-altitude responses even when orographic forcing was weak, 3) large-scale GWs at high altitudes arising from jet stream sources, and 4) significant flight-level energy fluxes and often very large momentum fluxes at high altitudes.

Ground-based microwave temperature profilers: Potential and experimental data

Calculated (potential) and experimental parameters (accuracy, vertical resolution, and calibration) of ground-based temperature profilers are analyzed. At the moment, single-channel scanning microwave profilers (MTP-5) are widely used for atmospheric boundary layer temperature profile measurements, and multifrequency microwave radiometers (MP-3000A, RPG-HATPRO, and MICRORADCOM) are used for tropospheric temperature profiling. Data of the MICRORADCOM profiler, which operated from January 1, 2014, to January 1, 2015, in Dolgoprudny, Moscow oblast, are considered in more detail.

The Effect of Pulsed Microwave Power on Transesterification of Chlorella sp. for Biodiesel Production

Pulsed microwave technique was employed for the production of biodiesel from Chlorellasp. via transesterification. Real-time microwave power and temperature profiles were used for the evaluation of efficiency of biodiesel production. The effect of power setting was determined in the range of 100–1000 W at the fixed reaction time (10 min) and temperature (60°C). In this work, the highest yield of biodiesel per unit energy consumption observed was 0.53% by weight of crude lipid per kilo joule at 250 W. From the results in this study, the efficiency of biodiesel production was correlated to the uniform pulse intensity and pulse frequency during the reaction process provided at the power setting of 250 W.

Наземные микроволновые температурные профилемеры: потенциал и реальность

Наземные микроволновые температурные профилемеры: потенциал и реальность

What can be measured by the temperature profiler

The ability of the ground-based microwave temperature profiler to retrieve the lapse rates in the lower part of the atmospheric boundary layer is verified by analyzing the long-term observation series. It is demonstrated that if the stratification of the whole boundary layer is either unstable or sufficiently homogeneous, measured and retrieved with a mast lapse rates are quite similar. If the stratification is stable, the retrieval algorithms require correction. Demonstrated is the potential for the more accurate retrieving of the temperature gradient over the surface layer by means of the angular scanning. This enables using the data of temperature profilers for estimating the boundary layer stability and the Monin-Obukhov scale.

Near‐monochromatic ducted gravity waves associated with a convective system close to the Pyrenees

Near‐monochromatic gravity waves (GWs) associated with a mesoscale convective system (MCS) were detected during the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) field campaign in Lannemezan (France) on 21 June 2011. These GWs are analyzed using available instrumental data (e.g. an array of microbarometers, a microwave system Humidity And Temperature PROfiler (HATPRO) and an ultra‐high‐frequency (UHF) wind profiler). Pressure oscillations of up to 0.5 hPa were recorded after a pronounced pressure drop of 1.4 hPa, identified as the MCS weak low. Wavelet analysis and evaluated wave parameters confirm the occurrence of such GWs (period ∼9 min, horizontal wavelength ∼7 km), which propagated from southwest to northeast, i.e. in the same direction of propagation as the MCS. Observational evidence suggests the downdraughts associated with the rear‐inflow jet at the weak low zone of the MCS as the most likely generator mechanism of the GWs. However, the complex orography and proximity of the Pyrenees to the field campaign could also play an important role. Wave propagation was possible through the ducting mechanism, favoured by the existence of a critical level in a wind‐sheared environment around 2000 m above ground level. Wave‐like motions related to the passage of the GWs were also observed in other atmospheric parameters close to the surface and within the lower troposphere. The effects of GWs on the surface fluxes have also been analyzed through Multi‐Resolution Flux Decomposition (MRFD) methods.