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Conference paperGlassmeier F, Hoffmann F, Feingold G, et al., 2022,
Gaussian-process emulation for integrating data-driven aerosol-cloud physics from simulation, satellite, and ground-based data
<jats:p>&lt;p&gt;Data-driven quantification and parameterization of cloud physics in general, and of aerosol-cloud interactions in particular, rely on input data from observations or detailed simulations. These data sources have complementary limitations in terms of their spatial and temporal coverage and resolution; simulation data has the advantage of readily providing causality but cannot represent the full process complexity. In order to base data-driven approaches on comprehensive information, we therefore need ways to integrate different data sources.&amp;#160;&lt;/p&gt;&lt;p&gt;We discuss how the classical statistical technique of Gaussian-process emulation can be combined with specifically initialized ensembles of detailed cloud simulations (large-eddy simulations, LES) to provide a framework for evaluating data-driven descriptions of cloud characteristics and processes across different data sources. We specifically illustrate this approach for integrating LES and satellite data of aerosol-cloud interactions in subtropical stratocumulus cloud decks. We furthermore explore the extension of our framework to ground-based observations of Arctic mixed-phase clouds.&lt;/p&gt;&lt;p&gt;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -&lt;/p&gt;&lt;p&gt;&lt;strong&gt;References:&lt;/strong&gt;&lt;/p&gt;&lt;ul&gt;&lt;li&gt;Glassmeier, F., F. Hoffmann, J. S. Johnson, T. Yamaguchi, K. S. Carslaw and G. Feingold (2019): &amp;#8220;An emulator approach to stratocumulus susceptibility&amp;#8221;, Atmos. Chem. Phys., 19, 10191- 10203, doi: 10.5194/acp-19-10191-2019&lt;/li&gt;&lt;li&gt;Hoffmann, F., F. Glassmeier, T. Yamaguchi and G. Feingold (2020)
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Journal articleVasko IY, Mozer FS, Bale SD, et al., 2022,
Ion-Acoustic Waves in a Quasi-Perpendicular Earth's Bow Shock
, GEOPHYSICAL RESEARCH LETTERS, Vol: 49, ISSN: 0094-8276- Cite
- Citations: 23
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Journal articleBreul P, Ceppi P, Shepherd TG, 2022,
Relationship between southern hemispheric jet variability and forced response: the role of the stratosphere
, Weather and Climate Dynamics, Vol: 3, Pages: 645-658, ISSN: 2698-4016Climate models show a wide range of southern hemispheric jet responses to greenhouse gas forcing. One approach to constrain the future jet response is by utilising the fluctuation–dissipation theorem (FDT) which links the forced response to internal variability timescales, with the Southern Annular Mode (SAM) the most dominant mode of variability of the southern hemispheric jet. We show that interannual stratospheric variability approximately doubles the SAM timescale during austral summer in both re-analysis data and models from the Coupled Model Intercomparison Project, Phases 5 (CMIP5) and 6 (CMIP6). Using a simple barotropic model, we demonstrate how the enhanced SAM timescale subsequently leads to an overestimate of the forced jet response based on the FDT, and we introduce a method to correct for the stratospheric influence. This result helps to resolve a previously identified discrepancy between the seasonality of jet response and the internal variability timescale. However, even after accounting for this influence, the SAM timescale cannot explain inter-model differences in the forced jet shift across CMIP models during austral summer.
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Journal articleTasgaonkar P, Zade D, Ehsan S, et al., 2022,
Indoor heat measurement data from low-income households in rural and urban South Asia.
, Sci Data, Vol: 9Rising temperatures are causing distress across the world, and for those most vulnerable, it is a silent killer. Information about indoor air temperature in residential dwellings is of interest for a range of reasons, such as health, thermal comfort and coping practices. However, there have been only few studies that measure indoor heat exposure, and contrast these to outdoor temperatures in rural-urban areas, of which none are in South Asia. We aim to close this knowledge gap with our indoor and outdoor heat measurement dataset, covering five low-income sites in South Asia. Two sites are in rural areas (Maharashtra, India), while three sites focus on urban areas (Dhaka, Delhi and Faisalabad). Data are based on 206 indoor temperature data loggers and complemented by data from five outdoor automated weather stations. The data-set can be used to examine temperature and humidity variation in low-socioeconomic status households in rural and urban areas and to better understand factors aggravating heat stress. This is important to plan and implement actions for combating heat stress.
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Journal articleWang S, Toumi R, 2022,
An analytic model of the tropical cyclone outer size
, npj Climate and Atmospheric Science, Vol: 5, ISSN: 2397-3722There are simple conceptual models of tropical cyclone intensification and potential intensity. However, such a framework has been lacking to describe the evolution of the outer circulation. An analytic growth model of the tropical cyclone outer size is derived from the angular momentum equation. The growth model fits a full-physics idealized tropical cyclone simulation. The lifecycle composite of the best-track outer size growth shows a strong super-linear nature, which supports an exponential growth as predicted by the growth model. The climatology of outer size growth measured by the radius of gale-force wind in the North Atlantic and Eastern Pacific during the period 2004–2017, can be understood in terms of four growth factors of the model: the initial size, the growth duration, the mean growth latitude, and the mean top-of-boundary-layer effective local inflow angle. All four variables are significantly different between the two basins. The observed lifetime maximum size follows a lognormal distribution, which is in line with the law of the proportionate effect of this exponential growth model. The growth model fits the observed outer size well in global basins. The time constant of the exponential size growth is approximately equal to the product of the Coriolis parameter and the mean effective inflow angle above the boundary layer. Further sensitivity experiments with the growth model suggest that the interannual variability of the global lifetime maximum size is largely driven by the variation of growth duration.
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Journal articleJia H, Quaas J, Gryspeerdt E, et al., 2022,
Addressing the difficulties in quantifying droplet number response to aerosol from satellite observations
, Atmospheric Chemistry and Physics, Vol: 22, Pages: 7353-7372, ISSN: 1680-7316Aerosol–cloud interaction is the most uncertain component of the overall anthropogenic forcing of the climate, in which cloud droplet number concentration (Nd) sensitivity to aerosol (S) is a key term for the overall estimation. However, satellite-based estimates of S are especially challenging, mainly due to the difficulty in disentangling aerosol effects on Nd from possible confounders. By combining multiple satellite observations and reanalysis, this study investigates the impacts of (a) updraft, (b) precipitation, (c) retrieval errors, and (d) vertical co-location between aerosol and cloud on the assessment of S in the context of marine warm (liquid) clouds. Our analysis suggests that S increases remarkably with both cloud-base height and cloud geometric thickness (proxies for vertical velocity at cloud base), consistent with stronger aerosol–cloud interactions at larger updraft velocity for midlatitude and low-latitude clouds. In turn, introducing the confounding effect of aerosol–precipitation interaction can artificially amplify S by an estimated 21 %, highlighting the necessity of removing precipitating clouds from analyses of S. It is noted that the retrieval biases in aerosol and cloud appear to underestimate S, in which cloud fraction acts as a key modulator, making it practically difficult to balance the accuracies of aerosol–cloud retrievals at aggregate scales (e.g., 1 grid). Moreover, we show that using column-integrated sulfate mass concentration (SO4C) to approximate sulfate concentration at cloud base (SO4B) can result in a degradation of correlation with Nd, along with a nearly twofold enhancement of S, mostly attributed to the inability of SO4C to capture the full spatiotemporal variability of SO4B. These findings point to several potential ways forward to practically account for the major influential factors by means of satellite observations and reanalysis, aiming at optimal observational estimates of global radia
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Journal articleArcher M, Cottingham M, Hartinger M, et al., 2022,
Listening to the magnetosphere: How best to make ULF waves audible
, Frontiers in Astronomy and Space Sciences, Vol: 9, ISSN: 2296-987XObservations across the heliosphere typically rely on in situ spacecraft observations producing time-series data. While often this data is analysed visually, it lends itself more naturally to our sense of sound. The simplest method of converting oscillatory data into audible sound is audification—a one-to-one mapping of data samples to audio samples—which has the benefit that no information is lost, thus is a true representation of the original data. However, audification can make some magnetospheric ULF waves observations pass by too quickly for someone to realistically be able to listen to effectively. For this reason, we detail various existing audio time scale modification techniques developed for music, applying these to ULF wave observations by spacecraft and exploring how they affect the properties of the resulting audio. Through a public dialogue we arrive at recommendations for ULF wave researchers on rendering these waves audible and discuss the scientific and educational possibilities of these new methods.
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Journal articleShaylor M, Brindley H, Sellar A, 2022,
An evaluation of two decades of aerosol optical depth retrievals from MODIS over Australia
, Remote Sensing, Vol: 14, Pages: 1-23, ISSN: 2072-4292We present an evaluation of Aerosol Optical Depth (AOD) retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) over Australia covering the period 2001–2020. We focus on retrievals from the Deep Blue (DB) and Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithms, showing how these compare to one another in time and space. We further employ speciated AOD estimates from Copernicus Atmospheric Monitoring Service (CAMS) reanalyses to help diagnose aerosol types and hence sources. Considering Australia as a whole, monthly mean AODs show similar temporal behaviour, with a well-defined seasonal peak in the Austral summer. However, excepting periods of intense biomass burning activity, MAIAC values are systematically higher than their DB counterparts by, on average, 50%. Decomposing into seasonal maps, the patterns of behaviour show distinct differences, with DB showing a larger dynamic range in AOD, with markedly higher AODs (ΔAOD∼0.1) in northern and southeastern regions during Austral winter and summer. This is counter-balanced by typically smaller DB values across the Australian interior. Site level comparisons with all available level 2 AOD data from Australian Aerosol Robotic Network (AERONET) sites operational during the study period show that MAIAC tends to marginally outperform DB in terms of correlation (RMAIAC = 0.71, RDB = 0.65) and root-mean-square error (RMSEMAIAC = 0.065, RMSEDB = 0.072). To probe this behaviour further, we classify the sites according to the predominant surface type within a 25 km radius. This analysis shows that MAIAC’s advantage is retained across all surface types for R and all but one for RMSE. For this surface type (Bare, comprising just 1.2% of Australia) the performance of both algorithms is relatively poor, (RMAIAC = 0.403, RDB = 0.332).
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Journal articleBourouaine S, Perez JC, Raouafi NE, et al., 2022,
Features of Magnetic Field Switchbacks in Relation to the Local-field Geometry of Large-amplitude Alfvenic Oscillations: Wind and PSP Observations
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 932, ISSN: 2041-8205- Cite
- Citations: 7
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Journal articleHunt GJ, Provan G, Bradley TJ, et al., 2022,
The response of Saturn's dawn field-aligned currents to magnetospheric and ring current conditions during Cassini's proximal orbits: evidence for a Region 2 response at Saturn
, Journal of Geophysical Research: Space Physics, Vol: 127, Pages: 1-15, ISSN: 2169-9380Cassini's 2017 proximal orbits provided the opportunity to examine the auroral field-aligned currents in the northern hemisphere dawn sector in relation to wider magnetospheric conditions. We combine three recent studies to examine the response of the dawn region auroral field-aligned currents and the azimuthal ring currents to compressions and expansions of the Saturnian magnetosphere. For compressions of Saturn's magnetosphere resulting in tail reconnection, the currents within the downward current sheet, located equatorward of the main auroral oval, increases in strength with increasing total ring current and location of the peak downwards current moves inwards toward Saturn. While the inverse relation occurs during intervals of quiet or expanded magnetospheric conditions. During compression events there is an increase in the energetic particle intensities, in particular in the protons (35–506 keV), within the downward current region. This current system is akin to an Earth-like “region 2” field aligned current within Saturn's magnetosphere, with tail reconnection occurring when the magnetosphere is compressed resulting in a partial nightside ring current closed by a downward current near to dawn. Within the upward current sheet, mapping to Saturn's main auroral oval, both non-rotating subcorotating current and the rotating Planetary Period Oscillations (PPOs) currents flow. The upward current is strongly modulated by the PPOs but also increases in strength, with enhanced high-energy protons, during intervals of magnetospheric compressions and tail reconnection. We conclude that the enhanced plasma injected into the midnight-dawn sector during tail reconnection events results in an enhanced subcorotation current system.
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Journal articleMa B, Chen L, Wu D, et al., 2022,
Discrepancy between the Low-frequency Cutoffs of Type III Radio Bursts Based on Simultaneous Observations by WIND and PSP
, ASTROPHYSICAL JOURNAL LETTERS, Vol: 932, ISSN: 2041-8205- Cite
- Citations: 3
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Journal articleBadman ST, Brooks DH, Poirier N, et al., 2022,
Constraining Global Coronal Models with Multiple Independent Observables
, ASTROPHYSICAL JOURNAL, Vol: 932, ISSN: 0004-637X- Cite
- Citations: 22
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Journal articleAgiwal O, Masters A, Hunt G, et al., 2022,
The contribution of planetary period oscillations towards circulation and mass loss in Saturn’s magnetosphere
, Journal of Geophysical Research: Space Physics, Vol: 127, Pages: 1-17, ISSN: 2169-9380Magnetic reconnection is a process during which magnetic energy is released as kinetic energy. It is considered a crucial driver of energy transport and mass loss within Saturn's magnetosphere. On long-term timescales, is thought to be predominantly driven by the rapid rotation of equatorially mass-loaded flux tubes (i.e., the Vasyliunas cycle), but there is some non-negligible driving from the solar wind as well (i.e., the Dungey cycle). In this study, we investigate an atmospheric driven phenomenon that modulates Saturn's magnetosphere every ∼10.6–10.8 hr, known as planetary period oscillations (PPOs), as an additional driver of magnetic reconnection at Saturn. Using an empirical model of PPO dynamics and Cassini magnetic field and plasma measurements, we find that PPO-driven magnetic reconnection is likely to occur in Saturn's magnetosphere, however, the occurrence of the phenomenon depends on temporally variable characteristics of the PPO systems and spatial asymmetries within Saturn's equatorial magnetosphere. Thus, it is not expected to be an on-going process. On year-long timescales, we find that PPOs are expected to be on par with the Dungey Cycle in driving circulation within Saturn's magnetosphere. However, on ∼1–2 weeks-long timescales, under specific conditions where PPO-driven reconnection is expected to be active, this phenomenon can become more significant than the Vasyliunas cycle, and thus dominate circulation within Saturn's magnetosphere. On year-long timescales, this process is estimated to remove upwards of ∼20% of the mass loaded into the magnetosphere by Enceladus.
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Journal articleDumont V, Bowen TA, Roglans R, et al., 2022,
Do cities have a unique magnetic pulse?
, JOURNAL OF APPLIED PHYSICS, Vol: 131, ISSN: 0021-8979- Cite
- Citations: 4
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Journal articleGangopadhyay A, Sparks NJ, Toumi R, et al., 2022,
Risk assessment of wind droughts over India
, Current Science, Vol: 122, Pages: 1145-1153, ISSN: 0011-3891Wind power growth makes it essential to simulateweather variability and its impacts on the electricitygrid. Low-probability, high-impact weather events suchas a wind drought are important but difficult to identify based on limited historical datasets. A stochasticweather generator, Imperial College Weather Generator (IMAGE), is employed to identify extreme eventsthrough long-period simulations. IMAGE capturesmean, spatial correlation and seasonality in wind speedand estimates return periods of extreme wind eventsover India. Simulations show that when Rajasthan experiences wind drought, southern India continues tohave wind, and vice versa. Regional grid-scale winddroughts could be avoided if grids are strongly interconnected across the country.
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Journal articlePhan TD, Verniero JL, Larson D, et al., 2022,
Parker solar probe observations of solar wind energetic proton beams produced by magnetic reconnection in the near‐sun heliospheric current sheet
, Geophysical Research Letters, Vol: 49, ISSN: 0094-8276We report observations of reconnection exhausts in the Heliospheric Current Sheet (HCS) during Parker Solar Probe Encounters 08 and 07, at 16 Rs and 20 Rs, respectively. Heliospheric current sheet (HCS) reconnection accelerated protons to almost twice the solar wind speed and increased the proton core energy by a factor of ∼3, due to the Alfvén speed being comparable to the solar wind flow speed at these near-Sun distances. Furthermore, protons were energized to super-thermal energies. During E08, energized protons were found to have leaked out of the exhaust along separatrix field lines, appearing as field-aligned energetic proton beams in a broad region outside the HCS. Concurrent dropouts of strahl electrons, indicating disconnection from the Sun, provide further evidence for the HCS being the source of the beams. Around the HCS in E07, there were also proton beams but without electron strahl dropouts, indicating that their origin was not the local HCS reconnection exhaust.
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Journal articleSchwartz SJ, Goodrich KA, III LBW, et al., 2022,
Energy partition at collisionless supercritical quasiperpendicular shocks
<jats:p>Collisionless shocks in astrophysical plasmas are importantthermalizers, converting some of the incident flow energy into thermalenergy, and non-thermalizers, partitioning that energy in unequal waysto different particle species, sub-populations thereof, and fieldcomponents. This partition problem, or equivalently the shock equationof state, lies at the heart of shock physics. Here we employsystematically a framework to capture all the incident and downstreamenergy fluxes at two example traversals of the Earth's bow shock by theMagnetospheric Multiscale Mission. Here and traditionally such data hasto be augmented by information from other spacecraft, e.g., to providemore accurate measurements of the cold solar wind beam. With some careand fortuitous choices, the energy fluxes are constant, includinginstantaneous measurements through the shock layer. The dominantincident proton ram energy is converted primarily into downstream protonenthalpy flux, the majority of which is actually carried by a smallfraction of suprathermal protons. Fluctuations include both real andinstrumental effects. Separating these, resolving the solar wind beam,and other considerations point the way to a dedicated mission to solvethis energy partition problem across a full range of plasma and shockconditions.</jats:p>
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Conference paperDeca J, Stephenson P, Divin A, et al., 2022,
A Fully Kinetic Perspective on Weakly Active Comets: Symmetric versus Asymmetric Outgassing
, Publisher: Copernicus GmbH<jats:p>&lt;p&gt;For more than two years, ESA&amp;#8217;s Rosetta mission measured the complex and ever-evolving plasma environment surrounding comet 67P/Churyumov-Gerasimenko. In this work, we explore the structure and dynamics of the near-comet plasma environment at steady state, comparing directly the results of a spherically symmetric Haser model and an asymmetric outgassing profile based on the measurements from the ROSINA instrument onboard Rosetta during 67P&amp;#8217;s weakly outgassing stages. Using a fully kinetic semi-implicit particle-in-cell code, we are able to characterise (1) the various ion and electron populations and their interactions, and (2) the implications to the mass-loading process caused by taking into account asymmetric outgassing. Our model complements observations by providing a full 3D picture that is directly relevant to help interpret the measurements made by the Rosetta Plasma Consortium instruments. In addition, understanding such details better is key to help disentangle the physical drivers active in the plasma environment of comets visited by future exploration missions.&lt;/p&gt;</jats:p>
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Journal articleMurray-Watson RJ, Gryspeerdt E, 2022,
Stability-dependent increases in liquid water with droplet number in the Arctic
, Atmospheric Chemistry and Physics, Vol: 22, Pages: 5743-5756, ISSN: 1680-7316The effects of aerosols on cloud microphysical properties are a large source of uncertainty when assessing anthropogenic climate change. The aerosol–cloud relationship is particularly unclear in high-latitude polar regions due to a limited number of observations. Cloud liquid water path (LWP) is an important control on cloud radiative properties, particularly in the Arctic, where clouds play a central role in the surface energy budget. Therefore, understanding how aerosols may alter cloud LWP is important, especially as aerosol sources such as industry and shipping move further north in a warming Arctic.Using satellite data, this work investigates the effects of aerosols on liquid Arctic clouds over open ocean by considering the relationship between cloud droplet number concentration (Nd) and LWP, an important component of the aerosol–LWP relationship. The LWP response to Nd varies significantly across the region, with increases in LWP with Nd observed at very high latitudes in multiple satellite datasets, with this positive signal observed most strongly during the summer months. This result is in contrast to the negative response typically seen in global satellite studies and previous work on Arctic clouds showing little LWP response to aerosols.The lower tropospheric stability (LTS) was found to be an important control on the spatial variations in LWP response, strongly influencing the sign and magnitude of the Nd–LWP relationship, with increases in LWP in high-stability environments. The influence of humidity varied depending on the stability, with little impact at low LTS but a strong influence at high LTS. The mean Nd state does not dominate the LWP response, despite the non-linearities in the relationship. As the Nd–LWP sensitivity changed from positive to negative when moving from high- to low-LTS environments, this work shows evidence of a temperature-dependent aerosol indirect effect. Additionally, the LWP–LTS relationship chan
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Journal articleHellinger P, Montagud-Camps V, Franci L, et al., 2022,
Ion-scale Transition of Plasma Turbulence: Pressure-Strain Effect
, ASTROPHYSICAL JOURNAL, Vol: 930, ISSN: 0004-637X- Cite
- Citations: 7
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Journal articleNieves-Chinchilla T, Alzate N, Cremades H, et al., 2022,
Direct First Parker Solar Probe Observation of the Interaction of Two Successive Interplanetary Coronal Mass Ejections in 2020 November
, ASTROPHYSICAL JOURNAL, Vol: 930, ISSN: 0004-637X- Cite
- Citations: 17
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Journal articlePalmerio E, Lee CO, Mays ML, et al., 2022,
CMEs and SEPs During November-December 2020: A Challenge for Real-Time Space Weather Forecasting
, SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS, Vol: 20- Cite
- Citations: 22
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Journal articleAkbari H, Newman D, Fowler C, et al., 2022,
Micro-Scale Plasma Instabilities in the Interaction Region of the Solar Wind and the Martian Upper Atmosphere
, JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol: 127, ISSN: 2169-9380- Cite
- Citations: 1
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Journal articleBale SD, 2022,
Eugene N. Parker (1927-2022)
, SCIENCE, Vol: 376, Pages: 461-461, ISSN: 0036-8075- Cite
- Citations: 1
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Journal articleArcher M, Waters C, Dewan S, et al., 2022,
GC Insights: Space sector careers resources in the UK need a greater diversity of roles
, Geoscience Communication, Vol: 5, Pages: 119-123, ISSN: 2569-7110Educational research highlights that improved careers education is needed to increase participation in science, technology, engineering, and mathematics (STEM). Current UK careers resources concerning the space sector, however, are found to perhaps not best reflect the diversity of roles present and may in fact perpetuate misconceptions about the usefulness of science. We, therefore, compile a more diverse set of space-related jobs, which will be used in the development of a new space careers resource.
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Journal articleSalvi P, Ceppi P, Gregory JM, 2022,
Interpreting differences in radiative feedbacks from aerosols versus greenhouse gases
, Geophysical Research Letters, Vol: 49, Pages: 1-9, ISSN: 0094-8276Experiments with seven Coupled Model Intercomparison Project phase 6 models were used to assess the climate feedback parameter for net historical, historical greenhouse gas (GHG) and anthropogenic aerosol forcings. The net radiative feedback is found to be more amplifying (higher effective climate sensitivity) for aerosol than GHG forcing, and hence also less amplifying for net historical (GHG + aerosol) than GHG only. We demonstrate that this difference is consistent with their different latitudinal distributions. Historical aerosol forcing is most pronounced in northern extratropics, where the boundary layer is decoupled from the free troposphere, so the consequent temperature change is confined to low altitude and causes low-level cloud changes. This is caused by change in stability, which also affects upper-tropospheric clear-sky emission, affecting both shortwave and longwave radiative feedbacks. This response is a feature of extratropical forcing generally, regardless of its sign or hemisphere.
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Journal articleBrown ZL, Medvedev AS, Starichenko ED, et al., 2022,
Evidence for Gravity Waves in the Thermosphere of Saturn and Implications for Global Circulation
, GEOPHYSICAL RESEARCH LETTERS, Vol: 49, ISSN: 0094-8276- Cite
- Citations: 4
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Journal articleWarwick L, Brindley H, Di Roma A, et al., 2022,
Retrieval of tropospheric water vapour from airborne far-infrared measurements: a case study
, Journal of Geophysical Research: Atmospheres, Vol: 127, ISSN: 2169-897XWe describe studies undertaken in support of the Far-infrared Outgoing Radiation Understanding and Monitoring (FORUM) mission, ESA’s ninth Earth Explorer, designed to investigate whether airborne observations of far-infrared radiances can provide beneficial information on mid and upper tropospheric water vapour concentrations.Initially we perform a joint temperature and water vapour retrieval and show that the water vapour retrieval exploiting far-infrared measurements from the Tropospheric Airborne Fourier Transform Spectrometer (TAFTS) shows improvement over the a-priori Unified Model global forecast when compared to in situ dropsonde measurements. For this case the improvement is particularly noticeable in the mid-upper troposphere. Equivalent retrievals using mid-infrared radiances measured by the Airborne Research Interferometer Evaluation System (ARIES) show much reduced performance, with the degrees of freedom for signal (DFS), reduced by a factor of almost 2. Further sensitivity studies show that this advantage is decreased, but still present when the spectral resolution of the TAFTS measurements is reduced to match that of ARIES.The beneficial role of the far infrared for this case is further confirmed by performing water vapour only retrievals using ARIES and TAFTS individually, and then in combination. We find that the combined retrieval has a DFS value of 6.7 for water vapour, marginally larger than that obtained for the TAFTS retrieval and almost twice as large as that obtained for ARIES.These results provide observational support of theoretical studies highlighting the potential improvement that far-infrared observations could bring for the retrieval of tropospheric water vapour.
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Journal articleDimmock AP, Khotyaintsev YV, Lalti A, et al., 2022,
Analysis of multiscale structures at the quasi-perpendicular Venus bow shock Results from Solar Orbiter's first Venus flyby
, ASTRONOMY & ASTROPHYSICS, Vol: 660, ISSN: 0004-6361- Cite
- Citations: 3
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Journal articleRovithakis A, Grillakis MG, Seiradakis KD, et al., 2022,
Future climate change impact on wildfire danger over the Mediterranean: the case of Greece
, Environmental Research Letters, Vol: 17, ISSN: 1748-9326Recent studies have shown that temperature and precipitation in the Mediterranean are expected to change, contributing to longer and more intense summer droughts that even extend out of season. In connection to this, the frequency of forest fire occurrence and intensity will likely increase. In the present study, the changes in future fire danger conditions are assessed for the different regions of Greece using the Canadian fire weather index (FWI). Gridded future climate output as estimated from three regional climate models from the Coordinated Regional Downscaling Experiment are utilized. We use three representative concentration pathways (RCPs) consisting of an optimistic emissions scenario where emissions peak and decline beyond 2020 (RCP2.6), a middle-of-the-road scenario (RCP4.5) and a pessimistic scenario, in terms of mitigation where emissions continue to rise throughout the century (RCP8.5). Based on established critical fire FWI threshold values for Greece, the future change in days with critical fire danger were calculated for different areas of Greece domains. The results show that fire danger is expected to progressively increase in the future especially in the high-end climate change scenario with southern and eastern regions of Greece expected to have up to 40 additional days of high fire danger relative to the late 20th century, on average. Crete, the Aegean Islands, the Attica region, as well as parts of Peloponnese are predicted to experience a stronger increase in fire danger.
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