Microwave radiometer to retrieve temperature profiles from the surface to the stratopause

TEMPERA (TEMPERature RAdiometer) is a new ground-based radiometer which measures in a frequency range from 51–57 GHz radiation emitted by the atmosphere. 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 Aura satellite. In this paper we present the design and measurement method of the instrument followed by a description of the retrieval method, together with a validation of TEMPERA data over its first year, 2012.

Retrieval simulations of the vertical profiles of water vapour and other chemical species in the Martian atmosphere using PACS

Water vapour, despite being a minor constituent in the Martian atmosphere with its precipitable amount of less than 70 pr. μm, attracts considerable attention in the scientific community because of its potential importance for past life on Mars. The partial pressure of water vapour is highly variable because of its seasonal condensation onto the polar caps and exchange with a subsurface reservoir. It is also known to drive photochemical processes: photolysis of water produces H, OH, HO2 and some other odd hydrogen compounds, which in turn destroy ozone. Consequently, the abundance of water vapour is anti-correlated with ozone abundance. The Herschel Space Observatory provides for the first time the possibility to retrieve vertical water profiles in the Martian atmosphere. Herschel will contribute to this topic with its guaranteed-time key project called "Water and related chemistry in the solar system". Observations of Mars by Heterodyne Instrument for the Far Infrared (HIFI) and Photodetector Array Camera and Spectrometer (PACS) onboard Herschel are planned in the frame of the programme. HIFI with its high spectral resolution enables accurate observations of vertically resolved H2O and temperature profiles in the Martian atmosphere. Unlike HIFI, PACS is not capable of resolving the line-shape of molecular lines. However, our present study of PACS observations for the Martian atmosphere shows that the vertical sensitivity of the PACS observations can be improved by using multiple-line observations with different line opacities. We have investigated the possibility of retrieving vertical profiles of temperature and molecular abundances of minor species including H2O in the Martian atmosphere using PACS. In this paper, we report that PACS is able to provide water vapour vertical profiles for the Martian atmosphere and we present the expected spectra for future PACS observations. We also show that the spectral resolution does not allow the retrieval of several studied minor species, such as H2O2, HCl, NO, SO2, etc.

Temperature Prediction Model for Bone Drilling Based on Density Distribution and In Vivo Experiments for Minimally Invasive Robotic Cochlear Implantation

Surgical robots have been proposed ex vivo to drill precise holes in the temporal bone for minimally invasive cochlear implantation. The main risk of the procedure is damage of the facial nerve due to mechanical interaction or due to temperature elevation during the drilling process. To evaluate the thermal risk of the drilling process, a simplified model is proposed which aims to enable an assessment of risk posed to the facial nerve for a given set of constant process parameters for different mastoid bone densities. The model uses the bone density distribution along the drilling trajectory in the mastoid bone to calculate a time dependent heat production function at the tip of the drill bit. Using a time dependent moving point source Green's function, the heat equation can be solved at a certain point in space so that the resulting temperatures can be calculated over time. The model was calibrated and initially verified with in vivo temperature data. The data was collected in minimally invasive robotic drilling of 12 holes in four different sheep. The sheep were anesthetized and the temperature elevations were measured with a thermocouple which was inserted in a previously drilled hole next to the planned drilling trajectory. Bone density distributions were extracted from pre-operative CT data by averaging Hounsfield values over the drill bit diameter. Post-operative [Formula: see text]CT data was used to verify the drilling accuracy of the trajectories. The comparison of measured and calculated temperatures shows a very good match for both heating and cooling phases. The average prediction error of the maximum temperature was less than 0.7 °C and the average root mean square error was approximately 0.5 °C. To analyze potential thermal damage, the model was used to calculate temperature profiles and cumulative equivalent minutes at 43 °C at a minimal distance to the facial nerve. For the selected drilling parameters, temperature elevation profiles and cumulative equivalent minutes suggest that thermal elevation of this minimally invasive cochlear implantation surgery may pose a risk to the facial nerve, especially in sclerotic or high density mastoid bones. Optimized drilling parameters need to be evaluated and the model could be used for future risk evaluation.

LakeMIP Kivu: evaluating the representation of a large, deep tropical lake by a set of one-dimensional lake models

The African great lakes are of utmost importance for the local economy (fishing), as well as being essential to the survival of the local people. During the past decades, these lakes experienced fast changes in ecosystem structure and functioning, and their future evolution is a major concern. In this study, for the first time a set of one-dimensional lake models are evaluated for Lake Kivu (2.28°S; 28.98°E), East Africa. The unique limnology of this meromictic lake, with the importance of salinity and subsurface springs in a tropical high-altitude climate, presents a worthy challenge to the seven models involved in the Lake Model Intercomparison Project (LakeMIP). Meteorological observations from two automatic weather stations are used to drive the models, whereas a unique dataset, containing over 150 temperature profiles recorded since 2002, is used to assess the model’s performance. Simulations are performed over the freshwater layer only (60 m) and over the average lake depth (240 m), since salinity increases with depth below 60 m in Lake Kivu and some lake models do not account for the influence of salinity upon lake stratification. All models are able to reproduce the mixing seasonality in Lake Kivu, as well as the magnitude and seasonal cycle of the lake enthalpy change. Differences between the models can be ascribed to variations in the treatment of the radiative forcing and the computation of the turbulent heat fluxes. Fluctuations in wind velocity and solar radiation explain inter-annual variability of observed water column temperatures. The good agreement between the deep simulations and the observed meromictic stratification also shows that a subset of models is able to account for the salinity- and geothermal-induced effects upon deep-water stratification. Finally, based on the strengths and weaknesses discerned in this study, an informed choice of a one-dimensional lake model for a given research purpose becomes possible.

Understanding the performance of the FLake model over two African Great Lakes

The ability of the one-dimensional lake model FLake to represent the mixolimnion temperatures for tropical conditions was tested for three locations in East Africa: Lake Kivu and Lake Tanganyika's northern and southern basins. Meteorological observations from surrounding automatic weather stations were corrected and used to drive FLake, whereas a comprehensive set of water temperature profiles served to evaluate the model at each site. Careful forcing data correction and model configuration made it possible to reproduce the observed mixed layer seasonality at Lake Kivu and Lake Tanganyika (northern and southern basins), with correct representation of both the mixed layer depth and water temperatures. At Lake Kivu, mixolimnion temperatures predicted by FLake were found to be sensitive both to minimal variations in the external parameters and to small changes in the meteorological driving data, in particular wind velocity. In each case, small modifications may lead to a regime switch, from the correctly represented seasonal mixed layer deepening to either completely mixed or permanently stratified conditions from similar to 10 m downwards. In contrast, model temperatures were found to be robust close to the surface, with acceptable predictions of near-surface water temperatures even when the seasonal mixing regime is not reproduced. FLake can thus be a suitable tool to parameterise tropical lake water surface temperatures within atmospheric prediction models. Finally, FLake was used to attribute the seasonal mixing cycle at Lake Kivu to variations in the near-surface meteorological conditions. It was found that the annual mixing down to 60m during the main dry season is primarily due to enhanced lake evaporation and secondarily to the decreased incoming long wave radiation, both causing a significant heat loss from the lake surface and associated mixolimnion cooling.

Atmospheric Dynamics of Hot Exoplanets

The characterization of exoplanetary atmospheres has come of age in the last decade, as astronomical techniques now allow for albedos, chemical abundances, temperature profiles and maps, rotation periods and even wind speeds to be measured. Atmospheric dynamics sets the background state of density, temperature and velocity that determines or influences the spectral and temporal appearance of an exoplanetary atmosphere. Hot exoplanets are most amenable to these characterization techniques; in the present review, we focus on highly-irradiated, large exoplanets (the "hot Jupiters"), as astronomical data begin to confront theoretical questions. We summarize the basic atmospheric quantities inferred from the astronomical observations. We review the state of the art by addressing a series of current questions and look towards the future by considering a separate set of exploratory questions. Attaining the next level of understanding will require a concerted effort of constructing multi-faceted, multi-wavelength datasets for benchmark objects. Understanding clouds presents a formidable obstacle, as they introduce degeneracies into the interpretation of spectra, yet their properties and existence are directly influenced by atmospheric dynamics. Confronting general circulation models with these multi-faceted, multi-wavelength datasets will help us understand these and other degeneracies. The coming decade will witness a decisive confrontation of theory and simulation by the next generation of astronomical data.

Daily and seasonal thermal stresses in tilings: a field survey combined with numeric modeling

This study investigates thermally induced tensile stresses in ceramic tilings. Daily and seasonal thermal cycles, as well as, rare but extreme events, such as a hail-storm striking a heated terrace tiling, were studied in the field and by numerical modeling investigations. The field surveys delivered temperature– time diagrams and temperature profiles across tiling systems. These data were taken as input parameters for modeling the stress distribution in the tiling system in order to detect potential sites for material failure. Dependent on the thermal scenario (e.g., slow heating of the entire structure during morning and afternoon, or a rapid cooling of the tiles by a rain storm) the modeling indicates specific locations with high tensile stresses. Typically regions along the rim of the tiling field showed stresses, which can become critical with respect to the adhesion strength. Over the years, ongoing cycles of thermal expansion–contraction result in material fatigue promoting the propagation of cracks. However, the installation of flexible waterproofing membranes (applied between substrate and tile adhesive) represents an efficient technical innovation to reduce such crack propagation as confirmed by both numerical modeling results and microstructural studies on real systems.

Introduction to the Maïdo Lidar Calibration Campaign dedicated to the validation of upper air meteorological parameters

The first operations at the new High-altitude Maïdo Observatory at La Réunion began in 2013. The Maïdo Lidar Calibration Campaign (MALICCA) was organized there in April 2013 and has focused on the validation of the thermodynamic parameters (temperature, water vapor, and wind) measured with many instruments including the new very large lidar for water vapor and temperature profiles. The aim of this publication consists of providing an overview of the different instruments deployed during this campaign and their status, some of the targeted scientific questions and associated instrumental issues. Some specific detailed studies for some individual techniques were addressed elsewhere. This study shows that temperature profiles were obtained from the ground to the mesopause (80 km) thanks to the lidar and regular meteorological balloon-borne sondes with an overlap range showing good agreement. Water vapor is also monitored from the ground to the mesopause by using the Raman lidar and microwave techniques. Both techniques need to be pushed to their limit to reduce the missing range in the lower stratosphere. Total columns obtained from global positioning system or spectrometers are valuable for checking the calibration and ensuring vertical continuity. The lidar can also provide the vertical cloud structure that is a valuable complementary piece of information when investigating the water vapor cycle. Finally, wind vertical profiles, which were obtained from sondes, are now also retrieved at Maïdo from the newly implemented microwave technique and the lidar. Stable calibrations as well as a small-scale dynamical structure are required to monitor the thermodynamic state of the middle atmosphere, ensure validation of satellite sensors, study the transport of water vapor in the vicinity of the tropical tropopause and study their link with cirrus clouds and cyclones and the impact of small-scale dynamics (gravity waves) and their link with the mean state of the mesosphere.

Study of mineral dust entrainment in the planetary boundary layer by lidar depolarisation technique

Measurements on 27 June 2011 were performed over the Southern Iberian Peninsula at Granada EARLINET station, using active and passive remote sensing and airborne and surface in-situ data in order to study the entrainment processes between aerosols in the free troposphere and those in the planetary boundary layer (PBL). To this aim the temporal evolution of the lidar depolarisation, backscatter-related Angström exponent and potential temperature profiles were used in combination with the PBL contribution to the aerosol optical depth (AOD). Our results show that the mineral dust entrainment in the PBL was caused by the convective processes which ‘trapped’ the lofted mineral dust layer, distributing the mineral dust particles within the PBL. The temporal evolution of ground-based in-situ data evidenced the impact of this process at surface level. Finally, the amount of mineral dust in the atmospheric column available to be dispersed into the PBL was estimated by means of POLIPHON (Polarizing Lidar Photometer Networking). The dust mass concentration derived from POLIPHON was compared with the coarse-mode mass concentration retrieved with airborne in-situ measurements. Comparison shows differences below 50 µg/m³ (30% relative difference) indicating a relative good agreement between both techniques.

A new, fast and flexible radiative transfer method for Venus general circulation models

We present a new radiation scheme for the Oxford Planetary Unified Model System for Venus, suitable for the solar and thermal bands. This new and fast radiative parameterization uses a different approach in the two main radiative wavelength bands: solar radiation (0.1-5.5 mu m) and thermal radiation (1.7-260 mu m). The solar radiation calculation is based on the delta-Eddington approximation (two-stream-type) with an adding layer method. For the thermal radiation case, a code based on an absorptivity/emissivity formulation is used. The new radiative transfer formulation implemented is intended to be computationally light, to allow its incorporation in 3D global circulation models, but still allowing for the calculation of the effect of atmospheric conditions on radiative fluxes. This will allow us to investigate the dynamical-radiative-microphysical feedbacks. The model flexibility can be also used to explore the uncertainties in the Venus atmosphere such as the optical properties in the deep atmosphere or cloud amount. The results of radiative cooling and heating rates and the global-mean radiative-convective equilibrium temperature profiles for different atmospheric conditions are presented and discussed. This new scheme works in an atmospheric column and can be easily implemented in 3D Venus global circulation models. (C) 2014 Elsevier Ltd. All rights reserved.

Validation of MIPAS IMK/IAA temperature, water vapor, and ozone profiles with MOHAVE-2009 campaign measurements

MIPAS observations of temperature, water vapor, and ozone in October 2009 as derived with the scientific level-2 processor run by Karlsruhe Institute of Technology (KIT), Institute for Meteorology and Climate Research (IMK) and CSIC, Instituto de Astrofísica de Andalucía (IAA) and retrieved from version 4.67 level-1b data have been compared to co-located field campaign observations obtained during the MOHAVE-2009 campaign at the Table Mountain Facility near Pasadena, California in October 2009. The MIPAS measurements were validated regarding any potential biases of the profiles, and with respect to their precision estimates. The MOHAVE-2009 measurement campaign provided measurements of atmospheric profiles of temperature, water vapor/relative humidity, and ozone from the ground to the mesosphere by a suite of instruments including radiosondes, ozonesondes, frost point hygrometers, lidars, microwave radiometers and Fourier transform infra-red (FTIR) spectrometers. For MIPAS temperatures (version V4O_T_204), no significant bias was detected in the middle stratosphere; between 22 km and the tropopause MIPAS temperatures were found to be biased low by up to 2 K, while below the tropopause, they were found to be too high by the same amount. These findings confirm earlier comparisons of MIPAS temperatures to ECMWF data which revealed similar differences. Above 12 km up to 45 km, MIPAS water vapor (version V4O_H2O_203) is well within 10% of the data of all correlative instruments. The well-known dry bias of MIPAS water vapor above 50 km due to neglect of non-LTE effects in the current retrievals has been confirmed. Some instruments indicate that MIPAS water vapor might be biased high by 20 to 40% around 10 km (or 5 km below the tropopause), but a consistent picture from all comparisons could not be derived. MIPAS ozone (version V4O_O3_202) has a high bias of up to +0.9 ppmv around 37 km which is due to a non-identified continuum like radiance contribution. No further significant biases have been detected. Cross-comparison to co-located observations of other satellite instruments (Aura/MLS, ACE-FTS, AIRS) is provided as well.

Temperature and precipitation effects on δ13C depth profiles in SOM under temperate beech forests

Enrichment of 13C in SOM with soil depth is related to interacting processes influenced by temperature and precipitation. Our objectives were to derive climate effects on patterns of vertical δ13C values of soil organic matter (SOM) while minimizing the effect of confounding variables. We investigated vertical changes in δ13C values of SOM in 1-cm depth intervals in silvicultural mature beech (Fagus sylvatica L.) forest ecosystems in northern Rhineland-Palatinate across gradients of MAT (7.9 to 9.7 °C mean annual temperature) and MAP (607 to 1085 mm mean annual precipitation) in winter 2011. Forest stands (n = 10) were chosen based on data sets provided by the Rhineland-Palatinate Forest Administration so that variations in these gradients occurred while other environmental factors like physico-chemical soil properties, tree species, stand age, exposition and precipitation (for the temperature gradient) or temperature (for the precipitation gradient) did not differ among study sites. From litter down to the mineral soil at 10 cm depth, soil organic carbon (SOC) content decreased (47.5 ± SE 0.1% to 2.5 ± 0.1%) while the δ13C values increased (− 29.4 ± 0.1‰ to − 26.1 ± 0.1‰). Litter of sites under higher MAP/lower MAT had lower δ13C values which was in line with literature data on climate driven plant physiological process. To compare the dimension of the vertical 13C enrichment, δ13C values were regressed linearly against log-transformed carbon contents yielding absolute values of these slopes (beta). Beta values ranged between 0.6 and 4.5 (range of r from − 0.7 to − 1.0; p < 0.01). Due to an assumed decay continuum and similar variations of δ13C values in litter and in 10 cm depth, we conclude that effects on isotope composition in the Oi layer continue vertically and therefore, δ13C values in litter do not solely control beta values. Beta values decreased with increasing MAT (r = − 0.83; p < 0.05). Reduced soil moisture and therefore both, reduced microbial activity and reduced downward transport of microbial cycled DOM (=13C enriched) might be responsible for less pronounced δ13C depth profiles in case of high temperatures. Greater C:N ratios (lower degradability) of the litter under higher temperatures likely contributed to these depth trends. Beta values increased with increasing MAP (r = 0.73; p < 0.05). We found decreasing C:N ratios in the mineral soil that possibly indicates higher decomposition under higher precipitation. Exclusion of the organic layers from linear regressions indicated a stronger impact of MAP on the development of δ13C depth profiles. Our results confirm temperature and precipitation effects on δ13C depth profiles and indicate stronger 13C enrichment under lower MAT/higher MAP. Therefore, time series of vertical δ13C depth profiles might provide insights into climate change effects.