Microwave radiometer

We will report on recent results and on the extension of the eastern Mediterranean Altimeter Calibration network-eMACnet, to an Aegean-wide network of coastal tide gauges equipped with GNSS receivers and offshore buoys near OSTM groundtracks (ACTION). In collaboration with the Nat. Tech. Univ. of Athens (NTUA), the Hellenic Navy Hydrographic Service (HNHS) and the Hellenic Center for Marine Research (HCMR), the original network is expanding to cover all of the Aegean area, from the northernmost site at THASOS to the southernmost one on GAVDOS. The south Aegean is already adequately covered from four tide gauge sites equipped with CORS GNSS: at M A N I -K A R A V O S T A S I o n s o u t h e r n Peloponnese, EMPORIO on the island of Chios, KASTELI on northern Crete and PALEKASTRO on the easternmost edge of Crete. Additional tide gauges and GNSS will now be deployed at KYMI-EVIA and NEA SKIONI, before the end of 2012, to densify the network in the mid-and northern Aegean. The primary purpose of the extended network is the absolute calibration and validation of altimetry missions through the continuous monitoring of sea level and tectonics at locations near the OSTM mean groundtrack. This Aegean-wide network samples at the moment the OSTM/Jason-2 tracks 18, 33, 94, 109, and 185, some of them in more than one location. It will support current and future altimeter missions JASON-2/3, ENVISAT, Cryosat-2, HY-2A, JASON-CS and SWOT, especially the latter, requiring calibration over an area rather than a single track. In discussions with HCMR we have also reached agreement for the future use of their open-sea buoys once we outfit them with CORS GNSS receivers. Furthermore, HNHS has a funded proposal to obtain new, state-of-the-art tide gauges with GNSS receivers to replace their old equipment throughout their Aegean network, and for two additional buoys (NOAA's DART II type) and equipment for open-sea environmental monitoring. The main thrust of the project at the moment is to connect the currently deployed equipment with the global grid so that the data can be collected and made available in near real-time (e.g. on GTS). Our facilities will contribute the collected data to many other projects in the area (CLIVAR, WMO initiatives, IOC, GCOS, GOOS, GGOS, etc.) and the European Tsunami Warning System (ETWS). We will present the latest results from the current network and the latest bias estimates for OSTM/Jason-2.

This study presents a comprehensive assessment of longwave radiation variability in the Arctic based on unique measurements collected at the North Pole drifting station SP-28 in 1987. The primary objective is to compare these historical observations with modern datasets from the Surface Heat Budget of the Arctic Ocean (SHEBA, 1997-1998) and the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC, 2019-2020) to evaluate long-term changes in the Arctic radiation regime. Continuous longwave radiation measurements were obtained using high-precision spectral pyrgeometers to identify Arctic haze. The results show that in 1987, Arctic haze layers enhanced the downward longwave flux by 15-20 W•m-2 and increased atmospheric emissivity. In contrast, MOSAiC observations reveal emissivity values that closely match aerosol-free model calculations, indicating a substantial decline in Arctic haze and the diminishment of radiatively significant aerosol layers. This shift is in alignment with the long-term reduction of global anthropogenic sulfur dioxide emissions across the Northern Hemisphere.

Abstract. TEMPERA is a new ground-based radiometer which measures in a frequency range from 51–57 GHz radiation emitted by the atmosphere. The instrument operates thermally stabilized inside a lab. With this instrument it is possible to measure temperature profiles from ground to about 50 km. This is the first ground-based instrument with the capability to retrieve temperature profiles simultaneously for the troposphere and stratosphere. The measurement is done with a filterbank in combination with a digital Fast-Fourier-Transform spectrometer. A hot load and a noise diode are used as stable calibration sources. The optics consist of an off-axis parabolic mirror to collect the sky radiation. Due to the Zeeman effect on the emission lines used, the maximum height for the temperature retrieval is about 50 km. The effect is apparent in the measured spectra. The performance of TEMPERA is validated by comparison with nearby radiosonde and satellite data from the Microwave Limb Sounder on...

The microwave radiometer TROWARA measures integrated water vapour (IWV) and integrated cloud liquid water (ILW) at Bern since 1994 with a time resolution of 7 s. In this study, we compare TROWARA measurements with a simulation of summer 2012 in Switzerland performed with the Weather Research and Forecasting (WRF) model. It is found that the WRF model agrees very well with TROWARA's IWV variations with a mean bias of only 0.7 mm. The ILW distribution of the WRF model, although similar in shape to TROWARA's distribution, overestimates the fraction of clear sky periods (83% compared to 60%).

Context. This paper provides an overview of the Low Frequency Instrument (LFI) programme within the ESA Planck mission. Aims. The LFI instrument has been developed to produce high precision maps of the microwave sky at frequencies in the 27÷77 GHz range, below the peak of the Cosmic Microwave Background (CMB) radiation spectrum. Methods. The scientific goals are described, ranging from

In this paper, I outline the work related to Finite Difference Time Domain (FDTD) method that was done in this semester. The ultimate goal of this work is to perform coupled electromagnetic thermal analysis of radiometer calibration targets. This report describes the preliminary work that was performed towards this end. Two dimensional Finite Difference Time Domain (FDTD) method was implemented in software along with Total Field / Scattered Field (TF /SF) formulation. The code was numerically validated by estimating the Radar Cross Section (RCS) of right circular metallic cylinder and comparing it with analytical result. The report also contain details of HFSS simulations of electromagnetic wave absorbing pyramids.

This article presents the FMPL-2 on board the FSS-Cat mission, the 2017 ESA Small Sentinel Satellite Challenge and overall Copernicus Masters Competition winner. FMPL-2 is a passive microwave instrument based on a software-defined radio that implements a conventional global navigation satellite system-Reflectometer and an L-band radiometer, occupying 1 U of a 6 U CubeSat. The article describes the FSSC at mission context, the payload design and implementation phases, the tests results in a controlled environment, and finally the calibration algorithms applied to the downloaded data in order to extract the appropriate geophysical parameters: sea-ice coverage, sea-ice thickness (SIT), and low-resolution soil moisture. This article covers the overall payload design, from a high-level block diagram down to singlecomponent specifications from both hardware and software points of view. The main block of the instrument is based on the combination of an FPGA, which virtualizes a dual-core ARM processor, where most of the calculus are performed, and a software-defined radio module, in charge of I/Q data demodulation. The article also explains the design and implementation of a signal conditioning board required for the correct operation and calibration of both instruments.

The alternative mechanism of the emergence of cosmic microwave background radiation (CMB), associated with the thermal radiation of primordial gas-dust clouds in the early Universe, is considered. The emergence of such clouds in the theory of infinite hierarchical nesting of matter is a natural stage in matter evolution. The mass, radius, and spatial concentration of typical primordial gas-dust clouds, the distance between neighboring clouds, and the power of CMB energy generation per unit volume and per nucleon of the early Universe were calculated. The masses and radii of these clouds correspond to the masses and radii of the observed Bok globules. The presented mechanism is consistent with the cluster model describing the appearance of angular multipoles in the CMB power spectrum. In addition to CMB radiation, cosmic infrared background (CIB) radiation and cosmic optical background (COB) radiation are also considered. According to the presented model, the sources of CIB are primordial protoplanetary clouds. As for the COB radiation, it is associated with the radiation of the first protostars. During evolution, each primordial cloud, with a mass of about 31 solar masses, first generates CMB radiation, and then CIB and COB radiations. Since protostars give rise to neutron stars, the concentration of primordial gas-dust clouds is also the concentration of observed neutron stars. In the course of the calculations, a new definition of the radiation intensity is used, which is based on the vector of the surface energy flux density and accounts for the angles of incidence of radiation on a flat receiver from all sides of the hemisphere. According to Poynting's theorem, the relationship between the intensity and energy density of black body radiation is derived from the concept of photons.

50-MHz band wind profiler radars are only means to measure vertical air velocity ( ) and reflectivity-weighted particle fall velocity ( ) simultaneously. Linear depolarization ratio ( ) measured by a polarization lidar is useful to know phase and sphericity of hydrometeors. The 50-MHz band wind profiling radar named as the Equatorial Atmosphere Radar (EAR) and the 532-nm polarization lidar installed at Sumatra, Indonesia (0.2°S, 100.32°E, 865 m MSL) measured stratiform precipitation on 8 and 16 December 2008. A case of weak stratiform rainfall on 8 December and that of active stratiform rainfall on 16 December 2008 showed a marked contract in , , and . 1. はじめに 層状性降水内の雪片は落下しながら凝結・併合等に より成長し、0 高度に達すると融解して雨滴とな る。層状性降水の上部に存在する上昇流は、昇華 等を通じ雲水量や降水粒子サイズを増大させる主 要な要因である。そのため、大気の鉛直風速( ) の高精度測定は層状性降水の理解に不可欠である。 降水粒子の落下速度は、層状性降水の持続時間を 決定する重要な要因である。レーダーの鉛直方向 ビームで観測される降水粒子散乱強度で重み付け された降水粒子の落下速度( )は、 と降水 粒子散乱強度で重み付けされた背景大気に対する 降水粒子の落下速度( )の和である。そのため、 背景大気に対する降水粒子落下速度の測定には、 と の測定値を同時に得る必要がある。 赤道大気レー...

Activities such as the design and optimization of satellite constellations for telecommunications, communication solutions engineering, or GEO/non-GEO satellite inter-system coexistence applications benefit from methods to compute changes in Earth station equivalent noise temperature, a product of the dynamic nature of link geometry and the propagation channel. This paper addresses said requirement. Starting with a review of the user terminal G/T and Earth station noise temperature, methods are developed to compute the change in noise temperature introduced by varying elevation angle and propagation channel conditions. These methods are useful for engineering analyses when the noise contributions from each component of the Earth station receive chain are not known, especially considering the increased impact of clouds and gasses on GEO and non-GEO links operating in frequencies of the Q, E, and W bands. Examples of use and benefits are provided, as well as considerations on the applicability and validity of the methods.

During 9 March–9 April 2004, the North Slope of Alaska Arctic Winter Radiometric Experiment was conducted at the Atmospheric Radiation Measurement Program’s (ARM) “Great White” field site near Barrow, Alaska. The major goals of the experiment were to compare microwave and millimeter wavelength radiometers and to develop forward models in radiative transfer, all with a focus on cold (temperature from 0° to −40°C) and dry [precipitable water vapor (PWV) < 0.5 cm] conditions. To supplement the remote sensors, several radiosonde packages were deployed: Vaisala RS90 launched at the ARM Duplex and at the Great White and Sippican VIZ-B2 operated by the NWS. In addition, eight dual-radiosonde launches were conducted at the Duplex with Vaisala RS90 and Sippican GPS Mark II, the latter one modified to include a chilled mirror humidity sensor. Temperature comparisons showed a nighttime bias between VIZ-B2 and RS90, which reached 3.5°C at 30 hPa. Relative humidity comparisons indicated bette...

Tropical cyclone (TC) intensity prediction is far more challenging than the corresponding TC track prediction. One of the reasons is the lack of understanding of the coupling relationships of the physical processes controlling TC intensification. Data mining provides potential tools for relationship exploration from the ever-increasing amount of TC data. The data mining tools and algorithms require process-related features from raw observational data such as the TC best track data, TRMM data for 3D rainfall and 2D surface information. The data mining tools and algorithms can search for hidden relationships among the underlying features by means of statistical and logical inferences. In this article, we describe the data, definitions of features from the data, tools for data exploration, and several important results.

Juno microwave radiometer (MWR) observations of Jupiter's midlatitudes reveal a strong correlation between brightness temperature contrasts and zonal winds, confirming that the banded structure extends throughout the troposphere. However, the microwave brightness gradient is observed to change sign with depth: the belts are microwave‐bright in the bar range and microwave‐dark in the bar range. The transition level (which we call the “jovicline”) is evident in the MWR 11.5 cm channel, which samples the 5–14 bar range when using the limb‐darkening at all emission angles. The transition is located between 4 and 10 bars, and implies that belts change with depth from being ‐depleted to ‐enriched, or from physically warm to physically cool, or more likely a combination of both. The change in character occurs near the statically stable layer associated with water condensation. The implications of the transition are discussed in terms of ammonia redistribution via meridional circulation...

The Juno spacecraft provides unique close‐up views of Jupiter underneath the synchrotron radiation belts while circling Jupiter in its 53‐day orbits. The microwave radiometer (MWR) onboard measures Jupiter thermal radiation at wavelengths between 1.37 and 50 cm, penetrating the atmosphere to a pressure of a few hundred bars and greater. The mission provides the first measurements of Jupiter's deep atmosphere, down to ~250 bars in pressure, constraining the vertical distributions of its kinetic temperature and constituents. As a result, vertical structure models of Jupiter's atmosphere may now be tested by comparison with MWR data. Taking into account the MWR beam patterns and observation geometries, we test several published Jupiter atmospheric models against MWR data. Our residual analysis confirms Li et al.'s (2017, https://doi.org/10.1002/2017GL073159) result that ammonia depletion persists down to 50–60 bars where ground‐based Very Large Array was not able to observe...

The Juno microwave radiometer measured the thermal emission from Jupiter's atmosphere from the cloud tops at about 1 bar to as deep as a hundred bars of pressure during its first flyby over Jupiter (PJ1). The nadir brightness temperatures show that the Equatorial Zone is likely to be an ideal adiabat, which allows a determination of the deep ammonia abundance in the range  ppm. The combination of Markov chain Monte Carlo method and Tikhonov regularization is studied to invert Jupiter's global ammonia distribution assuming a prescribed temperature profile. The result shows (1) that ammonia is depleted globally down to 50–60 bars except within a few degrees of the equator, (2) the North Equatorial Belt is more depleted in ammonia than elsewhere, and (3) the ammonia concentration shows a slight inversion starting from about 7 bars to 2 bars. These results are robust regardless of the choice of water abundance.

Finding observational evidence of land surface and atmosphere interactions is crucial for understanding the spatial and temporal evolution of the boundary layer, as well as for model evaluation, and in particular for large-eddy simulation (LES) models. In this study, the influence of a heterogeneous land surface on the spatial distribution of atmospheric water vapor is assessed. Ground-based remote sensing measurements from a scanning microwave radiometer (MWR) are used in a long-term study over 6 years to characterize spatial heterogeneities in integrated water vapor (IWV) during clear-sky conditions at the Jülich ObservatorY for Cloud Evolution (JOYCE). The resulting deviations from the mean of the scans reveal a season-and direction-dependent IWV that is visible throughout the day. Comparisons with a satellite-derived spatial IWV distribution show good agreement for a selection of satellite overpasses during convective situations but no clear seasonal signal. With the help of a land use type classification and information on the topography, the main types of regions with a positive IWV deviation were determined to be agricultural fields and nearby open pit mines. Negative deviations occurred mainly above elevated forests and urban areas. In addition, high-resolution large-eddy simulations (LESs) are used to investigate changes in the water vapor and cloud fields for an altered land use input.

Aerosol signatures observed by ceilometers are frequently used to derive mixing-layer height (MLH) which is an essential variable for air quality modelling. However, Doppler wind lidar measurements of vertical velocity can provide a more direct estimation of MLH via simple thresholding. A case study reveals difficulties in the aerosol-based MLH retrieval during transition times when the mixing layer builds up in the morning and when turbulence decays in the afternoon. The difficulties can be explained by the fact that the aerosol distribution is related to the history of the mixing process and aerosol characteristics are modified by humidification. The results of the case study are generalized by evaluating one year of joint measurements by a Vaisala CT25K and a HALO Photonics Streamline wind lidar. On average the aerosol-based retrieval gives higher MLH than the wind lidar with an overestimation of MLH by about 300 m (600 m) in the morning (late afternoon). Also, the daily aerosol-based maximum MLH is larger and occurs later during the day and the average morning growth rates are smaller than those derived from the vertical wind. In fair weather conditions classified by less than 4 octa cloud cover the mean diurnal cycle of cloud base height corresponds well to the mixing-layer height showing potential for a simplified MLH estimation.