The role of experimental work in hydrological sciences – insights from a community survey

ABSTRACT

This opinion paper summarizes the results of an online survey on the role of experimental work in the hydrological sciences. The 20 survey questions covered various topics, such as advancements, needs, potentials and challenges in the hydrological sciences, and also touched on the issue of data sharing and data publication. A total of 336 hydrologists with both modelling and experimental backgrounds participated.     

Why and when it is useful to publish and share inconclusive results and failures: reply to “Reporting negative results to stimulate experimental hydrology”*

ABSTRACT

We thank van Emmerik et al. for their discussion of our opinion paper. We do not fully agree that publication of negative results will be very effective in promoting experimental hydrology. Instead, we think that experimental hydrology is considered to be more risky than modelling studies because of difficulties in publishing inconclusive results and the potential for failure.     

Incentives for field hydrology and data sharing: collaboration and compensation: reply to “A need for incentivizing field hydrology,especially in an era of open data”*

We thank Allen and Berghuijs for continuing the discussion on field hydrology and data sharing and discuss two incentives to promote data collection and sharing in hydrological sciences: a collaborative attitude and additional funding to make data publicly available.     

Microscale investigations of microbial communities in coastal surficial sediments

The upper millimeters of sediments are considered major locations of microbial colonization and activity. The goal of our study was to investigate variations of microbial communities in the uppermost sediment layers of the coastal Baltic Sea with emphasis on the complex interplay between microbiology and physico‐chemical sediment properties. We selected a high‐resolution methodological approach that combined the cryolanding sampling technique (spatial resolution of 250 μm) with microsensor‐, spectrophotometric and microscopic analyses. While the oxygen penetration depths in dark conditions ranged from 1.4 mm to 2.6 mm during the study period, this zone expanded by about 1 mm in light and could be divided into three micro‐horizons: (i) an upper zone with a high net O₂ production, (ii) an intermediate zone with increased O₂ consumption on account of light‐stimulated respiration and (iii) a lower zone with lower O₂ consumption. Time‐series experiments revealed a rapid response of the benthic microbial community to altered light intensities. In May and July, the net O₂ budget in the porewater of sediments was positive within 35 and 22 min after illumination, respectively, whereas in June O₂ production exceeded O₂ consumption after 112 min. The thickness of the O₂ production and O₂ consumption micro‐zones decreased from May to July coinciding with an increase in temperature. In May, sites of enhanced O₂ consumption were closely associated with subsurface maxima of microbial numbers and enzymatic activities indicating a tight coupling between photoautotrophic and heterotrophic processes between 1‐ and 2‐mm depth. In June and July, the microbial abundance and enzymatic activity hardly varied with depth. Spatial and temporal microheterogeneity of microbial distribution and activity in O₂ gradients was seen as a reflection of the complex interplay between microbiology and physico‐chemical sediment properties.     

Zur Problematik des Schichtstufenreliefs auf den Antillen

Zusammenfassung In Abhängigkeit von der Wechsellagerung wenig widerständiger und widerständiger, flach einfallender Schichten ist es sowohl auf den Großen als auch auf den Kleinen Antillen an verschiedenen Stellen zur Ausbildung eines Schichtstufenreliefs gekommen.Der Inselbogen der Antillen weist eine außerordentliche Variationsbreite ombrothermischer Klimate zwischen dem ariden und dem vollhumiden Bereich auf. Die Kleinräumigkeit der klimatischen Differenzierung ist ein weiteres Merkmal der Antillen. Auf kurze Entfernung vollzieht sich der Übergang von geringer zu großer Humidität.Die tektonisch-petrographischen Voraussetzungen einerseits und die klimatischen andererseits sind für ein Studium des Schichtstufenproblems somit besonders geeignet. Schichtstufen treten bei Lares-Utuado auf Puerto Rico im vollhumiden, auf Bonaire im ariden Bereich auf, und auf Barbados zieht die Schichtstufe des Korallenkalkes vom semiariden in den vollhumiden Bereich hinein.Die Untersuchung von Schichtstufen auf den Antillen erfolgt mit dem Ziel, die tektonische und klimatische Abhängigkeit des Formenschatzes zu klären und darüber hinaus festzustellen, inwieweit es sich beim heutigen Formenbild um Gegenwarts- bzw. Vorzeitformen handelt.

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Gently sloping layers of alternating resistent and less resistent strata are the precondition for the development of cuesta landscapes. These tectonic and petrographic preconditions are given in several localities of the Greater Antilles as well as of the Lesser Antilles. Besides that, the Antilles are characterized by an extremely broad variation of ombrothermic climates, and the transition from humid to arid conditions takes place within small distances.The Antilles therefore are well suited for the investigation of the climate's impact on landforms and geomorphological processes in cuesta-regions. The cuesta of Lares-Utuado in Puerto Rico, which is dealt with, is situated in an extremely humid region, that of the coral-limestone of Bonaire in an arid environment and that of Barbados' coral limestone in semihumid and humid areas. The analysis of these cuestas enables to get a better understanding of the differences of cuesta-landforms under the influence of different climatic conditions; moreover, it gives some hints in regard to changes of climate since the pleistocene period.

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Résumé Dépendant de l'alternance des couches dures et moins dures c'est un relief de cuestas qui s'est évolué dans certaines parties des îles des Grandes et des Petites Antilles.L'arc de ces îles montre une sucession de climats très variés allant du domaine aride jusqu'au climat humide. Les différences climatiques y se succèdent très rapide sur des distances assez courtes.D'une part ce sont les conditions tectoniques et pétrographiques, d'autre part les données climatiques qui sont favorables à une étude du problème des cuestas sur les îles des Antilles. Des cuestas s'observent près de Lares-Utuado sur l'île de Puerto Rico sous un climat humide, sur l'île de Bonaire dans le domaine aride, pendant que la cuesta du calcaire récifien sur l'île de Barbados s'étend du domaine semi-humide jusqu'au climat humide.Le but de l'analyse des cuestas sur les îles des Antilles est d'étudier l'influence de la tectonique et du climat sur le modèle et, en plus, d'étudier si le relief actuel est le résultat des procédés encore vivants ou déjà fossiles.

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Microstrain stability of Peninsular India 1864–1994

We report the results of the South Indian Strain Measuring Experiment (SISME) designed to determine whether strain related to microseismicity in the past century may have deformed the networks of the 19th century Great Trigonometrical Survey of India (GTS). More than a dozen GTS points were measured between Mangalore, Madras, and Kanyakumari in southernmost India using GPS geodesy to determine regional deformation. Detailed measurements were made near two of the original baselines of the survey to determine the reliability of dilatational strain data for the network. The regional measurements revealed negligible regional dilatational (+ 11.2 + 10 microstrain) and shear strain changes (0.66± 1.2μradians) in the southernmost 530 km of India. In addition to these measurements, we determined the rate of northward and eastward motion of a point in Bangalore (1991–1994) in the ITRF92 reference frame to be 39 ± 3.5 mm/year, and 51 ± 11 mm/year respectively. This is consistent with NUVEL-1A plate motion estimate for India. Simultaneous measurements to a point near Kathmandu reveal that the Indian plate and the Southern Himalaya are moving approximately in unison, placing an upper limit on the rate of creep processes beneath the lesser Himalaya of ≈6 mm/year, and suggesting relatively rigid behavior of the Indian plate north of Bangalore. The stability of the Indian plate is confirmed by the absence of significant changes in the lengths of the two baselines at Bangalore and Cape Comorin, which, within the limits of experimental error have not changed since 1869. The measurements place an upper limit for recent deformation in the southern peninsula, and hence a lower limit for the renewal time for intraplate earthquakes in the region of approximately 10,000 years, assuming shear failure strain of approximately 100 μradians. This, in turn, implies that recurrence intervals for Peninsular Earthquakes far exceed the length of the written historic record, suggesting that the characterisation of seismic recurrence intervals from historical studies is likely to be fruitless. In contrast, the SISME experiment demonstrates that the noise level of geodetic studies based on 19th century GTS data is less than 0.02 μstrain/year, providing considerable scope for delineating regions of anomalously high seismogenic strain, by GPS measurements at all available trig points of the 19th century GTS survey.     

人类活动对南极陆地生态系统的影响

由于科学考察活动日益频繁以及旅游业在南极地区的迅速开展 ,人类活动对南极陆地生态系统的影响在最近几十年内一直倍受国际社会的关注。在广泛收集国外有关资料的基础上 ,本文对人类活动引发的南极地区区域性的土壤与植被污染、野生动物受扰、外来物种引进、以及细菌性疾病侵入等方面进行了论述。同时 ,阐述了南极以外地区的人为污染源对南极环境的潜在威胁。最后 ,对“南极条约体系”与国际社会为保护南极环境所作出的不懈努力进行了简要介绍与评价。     

Radiometric observations of sea temperature at 2.65 GHZ over the chesapeake bay

The present work describes the various corrections necessary in order to deduce ocean surface temperature fromS-band microwave radiometer measurements and applies these results to a series of data obtained with a high absolute accuracy radiometer. Measurements made with a 2.65 GHz radiometer from an aircraft flown over the Chesapeake Bay area are presented and compared in detail with accurately obtained sea truth data. For the calm sea, it was found that the observed brightness temperature agreed well with that calculated from the known sea surface and atmospheric properties over a fairly wide range of surface salinity values (0.2 per mille to 25 per mille). For cases where the surface wind speeds are of the order of 7 to 15 knots, an excess brightness temperature was observed which is attributable to surface roughness and microscale surface disturbances. The excess brightness temperature dependence on wind speed was found to correlate to a certain extent with the rms wave slope dependence on wind speed.     

Rock-weathering by lichens in Antarctic: patterns and mechanisms

Saxicolous species of lichens are able to induce and accelerate weathering of their rock substrate, and effects of lichens on substrate can be attributed to both physical and chemical causes. This paper is focused on biotic weathering actions of epilithic and endolithic species on the different rock types (sandstones and volcanogenic rocks) in Antarctica. The patterns, mechanisms, processes and neoformations of rock-weathering resulting from lichen colonization are expounded in detail. Furthermore, it is pointed out that, for a better understanding of the impacts of lichens on environments, the studies on the rate of biotic weathering and the comprehensive involvement of the lichen effects on weathering of natural rocks remain to be carried out in Antarctica.