A new airborne broadband radiometer system and an efficient method to correct thermal offsets

The instrumentation of the High Altitude and Long Range (HALO) research aircraft is extended by the new Broadband AirCrAft RaDiometer Instrumentation (BACARDI) to quantify the radiative energy budget. Two sets of pyranometers and pyrgeometers are mounted to measure upward and downward solar (0.3&ndash;3 &mu;m) and thermal-infrared (3&ndash;100 &mu;m) irradiances. The radiometers are installed in a passively ventilated fairing to reduce the effects of the dynamic environment, e.g., fast changes of altitude and temperature. The remaining thermal effects range up to 20 W m-2 for the pyranometers and 10 W m-2 for the pyrgeometers; they are corrected using an new efficient method that is introduced in this paper. Using data collected by BACARDI during a night flight, the thermal offsets are parameterized by the rate of change of the radiometer sensor temperatures. Applying the sensor temperatures instead of ambient air temperature for the parameterization provides a linear correction function (200&ndash;600 W m-2 K-1 s), that depends on the mounting position of the radiometer on HALO. Furthermore, BACARDI measurements from the EUREC4A (Elucidating the role of clouds-circulation coupling in climate) field campaign are analyzed to characterize the performance of the radiometers and to evaluate all corrections applied in the data processing. Vertical profiles of irradiance measurements up to 10 km altitude show that the thermal offset correction limits the bias due to temperature changes to values below 10 W m-2. Measurements with BACARDI during horizontal, circular flight patterns in cloud-free conditions demonstrate that the common geometric attitude correction of the solar downward irradiance provides reliable measurements in this typical flight sections of EUREC4A, even without active stabilization of the radiometer.</p

Cirrus clouds

Andrew J. Heymsfield, Martina Kramer, Anna Luebke, Phil Brown, Daniel J. Cziczo, Charmaine Franklin, Ulrike Lohmann, Greg McFarquhar, Zbigniew Ulanowski and Kristof Van Trich, American Meteorological Society , January 2017, this article has been published in final form at DOI: http://dx.doi.org/10.1175/AMSMONOGRAPHS-D-16-0010.1 Published by AMS Publications © 2017 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (http://www.ametsoc.org/PUBSCopyrightPolicy).The goal of this article is to synthesize information about what is now known about one of the three main types of clouds, cirrus, and to identify areas where more knowledge is needed. Cirrus clouds, composed of ice particles, form primarily in the upper troposphere, where temperatures are generally below -30°C. Satellite observations show that the maximum-occurrence frequency of cirrus is near the tropics, with a large latitudinal movement seasonally. In-situ measurements obtained over a wide range of cloud types, formation mechanisms, temperatures, and geographical locations indicate that the ice water content and particle size generally decrease with decreasing temperature, whereas the ice particle concentration is nearly constant or increase slightly with decreasing temperature. High ice concentrations, sometimes observed in strong updrafts , results from homogeneous nucleation. The satellite-based and in-situ measurements indicate that cirrus ice crystals typically depart from the simple, idealized geometry for smooth hexagonal shapes, indicating complexity and/or surface roughness. Their shapes significantly impact cirrus radiative properties and feedbacks to climate. Cirrus clouds, one of the most uncertain components of general circulation models (GCM), pose one of the greatest challenges in predicting the rate and geographical pattern of climate change. Improved measurements of the properties and size distributions and surface structure of small ice crystals — about 20 μm, and identifying the dominant ice nucleation process — heterogeneous versus homogeneous ice nucleation, under different cloud dynamical forcings, will lead to a better representation of their properties in GCM and in modeling their current and future effects on climate.Peer reviewe

25th annual computational neuroscience meeting: CNS-2016

The same neuron may play different functional roles in the neural circuits to which it belongs. For example, neurons in the Tritonia pedal ganglia may participate in variable phases of the swim motor rhythms [1]. While such neuronal functional variability is likely to play a major role the delivery of the functionality of neural systems, it is difficult to study it in most nervous systems. We work on the pyloric rhythm network of the crustacean stomatogastric ganglion (STG) [2]. Typically network models of the STG treat neurons of the same functional type as a single model neuron (e.g. PD neurons), assuming the same conductance parameters for these neurons and implying their synchronous firing [3, 4]. However, simultaneous recording of PD neurons shows differences between the timings of spikes of these neurons. This may indicate functional variability of these neurons. Here we modelled separately the two PD neurons of the STG in a multi-neuron model of the pyloric network. Our neuron models comply with known correlations between conductance parameters of ionic currents. Our results reproduce the experimental finding of increasing spike time distance between spikes originating from the two model PD neurons during their synchronised burst phase. The PD neuron with the larger calcium conductance generates its spikes before the other PD neuron. Larger potassium conductance values in the follower neuron imply longer delays between spikes, see Fig. 17.Neuromodulators change the conductance parameters of neurons and maintain the ratios of these parameters [5]. Our results show that such changes may shift the individual contribution of two PD neurons to the PD-phase of the pyloric rhythm altering their functionality within this rhythm. Our work paves the way towards an accessible experimental and computational framework for the analysis of the mechanisms and impact of functional variability of neurons within the neural circuits to which they belong

26th Annual Computational Neuroscience Meeting (CNS*2017): Part 3 - Meeting Abstracts - Antwerp, Belgium. 15–20 July 2017

This work was produced as part of the activities of FAPESP Research,\ud Disseminations and Innovation Center for Neuromathematics (grant\ud 2013/07699-0, S. Paulo Research Foundation). NLK is supported by a\ud FAPESP postdoctoral fellowship (grant 2016/03855-5). ACR is partially\ud supported by a CNPq fellowship (grant 306251/2014-0)

The relationship of ice water content to atmospheric and microphysical properties in cirrus clouds based on in situ measurements

Ice clouds are known to be major contributors to radiative forcing in the atmosphere, yet understanding and describing their microphysical properties remains challenging. The ice water content (IWC) of cirrus clouds is of particular interest because it can be directly related to a number of other radiatively important variables such as extinction and effective radius. This dissertation explores data obtained from numerous airborne research campaigns to elucidate the dominant factors that determine the IWC and crystal concentration (Ni) characterizing cirrus clouds. The first part of this study uses a new merged dataset to obtain a representation of the IWC-temperature relationship using probability distribution functions (PDFs), which allows for the variability of IWC within a temperature band to be visualized. The IWC-PDFs are observed to be bimodal over the whole cirrus temperature range. This bimodality is also found in Ni-PDFs and might be attributed to different cirrus formation mechanisms such as heterogeneous and homogeneous freezing. Next, two midlatitude datasets (MACPEX and MidCiX) with differing IWC and Ni distributions are used to explore how cloud formation processes contribute to the resulting cirrus characteristics. Starting with large-scale processes, a case study analysis demonstrates the link between synoptic-scale dynamics and the differences observed between the MACPEX and MidCiX datasets. However, that link is not always clear, indicating that additional information is required to explain it. This is particularly evident when considering the Ni observations from MACPEX, which appear unaffected by factors such as vertical velocity. This result is unexpected considering the relationship between vertical velocity and nucleation processes. The final component of this analysis explores the cirrus formation processes at the nucleation level, while continuing to examine why the data in MACPEX and MidCiX are different from each other. A comparison to model simulations reveals that heterogeneous nucleation and subsequent homogeneous nucleation suppression are responsible for the Ni distribution in MACPEX. Conversely, the MidCiX IWC and Ni datasets exhibit a compatibility with model results showing heterogeneous nucleation followed by a secondary homogeneous nucleation event. Thus, it is likely that the differences observed in MACPEX and MidCiX mostly stem from differences in ice nuclei concentrations

A Workshop on Remote Sensing of the Atmosphere in Anticipation of the EarthCARE Satellite Mission

International audienceThe German Earth Cloud, Aerosol, and Radiation Explorer (EarthCARE) community and the French Expecting EarthCARE Learning from the A-Train (EECLAT) community, both dedicated to the use of Earth observing satellites for research on clouds, aerosols, precipitation, and radiation, came together for a joint workshop1 in January 2018. Its purpose was to provide a venue to share expertise and to encourage future collaboration between the two communities. The workshop focused on the use of remote sensing instrumentation for atmospheric observations, with special attention paid to the National Aeronautics and Space Administration’s (NASA) A-Train constellation of Earth observing satellites and the upcoming joint EarthCARE satellite mission between the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA). Sixty-eight participants from French and German universities and research institutes attended. The majority of the workshop was dedicated to the presentation of recent research, and a final group discussion was held to identify the topic(s) that could serve as the basis for framing future science initiatives based on the anticipated outputs and strengths of EarthCARE