Multi-Sensor Field Studies of Lightning and Implications for MTG-LI

Future geostationary satellite systems will offer a variety of improved observing capabilities which will be extremely useful for many applications like numerical weather forecasting, nowcasting of severe weather, climate research or hydrology. The planning for MTG (Meteosat Third Generation) includes an optical lightning imager (LI) as part of the payload. One requirement for a proper interpretation of these optical data is a better understanding of what components of a flash are to be seen from space and how these observations relate to ground based radio frequency observations. Therefore, the objectives of the present study concern the improvement of the understanding of the complex lightning process which then enables a proper interpretation of the optical data. For assessing the future performances and benefits of a geostationary lightning sensor this study takes advantage of the comprehensive lightning data sets obtained from the recent CHUVA field experiment performed in Brazil. (CHUVA - Cloud processes of tHe main precipitation systems in Brazil: A contribUtion to cloud resolVing modeling and to the GPM (GlobAl Precipitation Measurement)). During the rainy season of 2011-2012 a large number of ground based lightning detection systems was set up in the Sao Paulo area in Brazil. In the present study we look at the detailed radio frequency (RF) based observation from LINET (Lightning detection network operated by DLR, nowcast and USP) and observing strokes in the VLF/LF (very low and low frequency) range, the LMA (Lightning mapping array) from NASA observing RF sources in the VHF (very high frequency) range and the TRMM-LIS (Tropical Rainfall Measuring Mission-Lightning Imaging Sensor) optical space borne lightning imager. The LIS is used as a reference instrument for the future MTG-LI sensor as well as for the corresponding GLM sensor (Geostationary Lightning Mapper) on GOES-R. Thus it is possible to study the relations between the RF and optical signals from lightning in detail and to assess the performance of the future geostationary observations from a set of proxy satellite data generated from the ground based observations. In confirmation of previous studies, it was found that often a direct temporal coincidence of RF signals (LINET strokes) and optical pulses (LIS groups) exists. The short baseline configuration of LINET allowed to observe the strokes mapping the flash branches similar to LMA, but by locating the limited number of strong cloud strokes rather than a large number of weak source points from leader steps. An initial breakdown phase of vertically propagating sources can often be found in LINET and LMA data. The higher level LINET and LMA signals have higher probability to be optically detected. Lower level LINET and LMA signals are optically detected from above in case of missing high level precipitation as inferred from radar observations provided by USP. The new comprehensive data set allows for constructing proxy data for the future geostationary lightning mappers

Further evidence for CCN aerosol concentrations determining the height of warm rain and ice initiation in convective clouds over the Amazon basin

We have investigated how aerosols affect the height above cloud base of rain and ice hydrometeor Initiation and the subsequent vertical evolution of cloud droplet size and number concentrations in growing convective cumulus. For this purpose we used in situ data of hydrometeor size distributions measured with instruments mounted on HALO aircraft during the ACRIDICON CHUVA campaign over the Amazon during September 2014. The results show that the height of rain initiation by collision and coalescence processes is linearly correlated with the number concentration of droplets nucleated at cloud base

The Sao Paulo Lightning Mapping Array (SPLMA): Prospects to GOES-R GLM and CHUVA

This paper presents the characteristics and prospects of a Lightning Mapping Array to be deployed at the city of S o Paulo (SPLMA). This LMA network will provide CHUVA campaign with total lightning, lightning channel mapping and detailed information on the locations of cloud charge regions for the thunderstorms investigated during one of its IOP. The real-time availability of LMA observations will also contribute to and support improved weather situational awareness and mission execution. For GOES-R program it will form the basis of generating unique and valuable proxy data sets for both GLM and ABI sensors in support of several on-going research investigation

Perturbation evolution with a non-minimally coupled scalar field

We recently proposed a simple dilaton-derived quintessence model in which the scalar field was non-minimally coupled to cold dark matter, but not to `visible' matter. Such couplings can be attributed to the dilaton in the low energy limit of string theory, beyond tree level. In this paper we discuss the implications of such a model on structure formation, looking at its impact on matter perturbations and CMB anisotropies. We find that the model only deviates from $\Lambda$CDM and minimally coupled theories at late times, and is well fitted to current observational data. The signature left by the coupling, when it breaks degeneracy at late times, presents a valuable opportunity to constrain non-minimal couplings given the wealth of new observational data promised in the near future.Comment: Version appearing in Physical Review D. 10 pages, 9 figs. Comparison with SN1a and projected MAP results, and appendix adde

Current constraints on the dark energy equation of state

We combine complementary datasets from Cosmic Microwave Background (CMB) anisotropy measurements, high redshift supernovae (SN-Ia) observations and data from local cluster abundances and galaxy clustering (LSS) to constrain the dark energy equation of state parameterized by a constant pressure-to-density ratio $w_Q$. Under the assumption of flatness, we find $w_Q < -0.85$ at 68% c.l., providing no significant evidence for quintessential behaviour different from that of a cosmological constant. We then generalise our result to show that the constraints placed on a constant $w_{Q}$ can be safely extended to dynamical theories. We consider a variety of quintessential dynamical models based on inverse power law, exponential and oscillatory scaling potentials. We find that SN1a observations are `numbed' to dynamical shifts in the equation of state, making the prospect of reconstructing $w(z)$, a challenging one indeed.Comment: 6 pages, 6 figures. Version accepted for publication in PR

Does having a twin-brother make for a bigger brain?

Objective: Brain volume of boys is larger than that of girls by ∼10%. Prenatal exposure to testosterone has been suggested in the masculinization of the brain. For example, in litter-bearing mammals intrauterine position increases prenatal testosterone exposure through adjacent male fetuses, resulting in masculinization of brain morphology. Design: The influence of intrauterine presence of a male co-twin on masculinization of human brain volume was studied in 9-year old twins. Methods: Magnetic resonance imaging brain scans, current testosterone, and estradiol levels were acquired from four groups of dizygotic (DZ) twins: boys from same-sex twin-pairs (SSM), boys from opposite-sex twin-pairs (OSM), girls from opposite-sex twin-pairs (OSF), and girls from same-sex twin-pairs (SSF; n=119 individuals). Data on total brain, cerebellum, gray and white matter volumes were examined. Results: Irrespective of their own sex, children with a male co-twin as compared to children with a female co-twin had larger total brain (+2.5%) and cerebellum (+5.5%) volumes. SSM, purportedly exposed to the highest prenatal testosterone levels, were found to have the largest volumes, followed by OSM, OSF and SSF children. Birth weight partly explained the effect on brain volumes. Current testosterone and estradiol levels did not account for the volumetric brain differences. However, the effects observed in children did not replicate in adult twins. Conclusions: Our study indicates that sharing the uterus with a DZ twin brother increases total brain volume in 9-year olds. The effect may be transient and limited to a critical period in childhood. © 2009 European Society of Endocrinology

Early-universe constraints on a Primordial Scaling Field

In the past years 'quintessence' models have been considered which can produce the accelerated expansion in the universe suggested by recent astronomical observations. One of the key differences between quintessence and a cosmological constant is that the energy density in quintessence, $\Omega_\phi$, could be a significant fraction of the overall energy even in the early universe, while the cosmological constant will be dynamically relevant only at late times. We use standard Big Bang Nucleosynthesis and the observed abundances of primordial nuclides to put constraints on $\Omega_\phi$ at temperatures near $T \sim 1MeV$. We point out that current experimental data does not support the presence of such a field, providing the strong constraint $\Omega_\phi(MeV) < 0.045$ at $2\sigma$ C.L. and strengthening previous results. We also consider the effect a scaling field has on CMB anisotropies using the recent data from Boomerang and DASI, providing the CMB constraint $\Omega_\phi \le 0.39$ at $2\sigma$ during the radiation dominated epoch.Comment: 5 pages, 4 figures. The revised version includes the new Boomerang and DASI dat

Could supermassive black holes be quintessential primordial black holes?

There is growing observational evidence for a population of supermassive black holes (SMBHs) in galactic bulges. We examine in detail the conditions under which these black holes must have originated from primordial black holes (PBHs). We consider the merging and accretion history experienced by SMBHs to find that, whereas it is possible that they were formed by purely astrophysical processes, this is unlikely and most probably a populations of primordial progenitors is necessary. We identify the mass distribution and comoving density of this population and then propose a cosmological scenario producing PBHs with the right properties. Although this is not essential we consider PBHs produced at the end of a period of inflation with a blue spectrum of fluctuations. We constrain the value of the spectral tilt in order to obtain the required PBH comoving density. We then assume that PBHs grow by accreting quintessence showing that their mass scales like the horizon mass while the quintessence field itself is scaling. We find that if scaling is broken just before nucleosynthesis (as is the case with some attractive non-minimally coupled models) we obtain the appropriate PBH mass distribution. Hawking evaporation is negligible in most cases, but we also discuss situations in which the interplay of accretion and evaporation is relevant.Comment: 11 pages, 12 figure