Global maps of soil temperature

Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km2 resolution for 0–5 and 5–15 cm soil depth. These maps were created by calculating the difference (i.e. offset) between in situ soil temperature measurements, based on time series from over 1200 1-km2 pixels (summarized from 8519 unique temperature sensors) across all the world\u27s major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (−0.7 ± 2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications

Global maps of soil temperature

Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km² resolution for 0–5 and 5–15 cm soil depth. These maps were created by calculating the difference (i.e., offset) between in-situ soil temperature measurements, based on time series from over 1200 1-km² pixels (summarized from 8500 unique temperature sensors) across all the world’s major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (-0.7 ± 2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in-situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications

The FLUXNET2015 dataset and the ONEFlux processing pipeline for eddy covariance data

The FLUXNET2015 dataset provides ecosystem-scale data on CO2, water, and energy exchange between the biosphere and the atmosphere, and other meteorological and biological measurements, from 212 sites around the globe (over 1500 site-years, up to and including year 2014). These sites, independently managed and operated, voluntarily contributed their data to create global datasets. Data were quality controlled and processed using uniform methods, to improve consistency and intercomparability across sites. The dataset is already being used in a number of applications, including ecophysiology studies, remote sensing studies, and development of ecosystem and Earth system models. FLUXNET2015 includes derived-data products, such as gap-filled time series, ecosystem respiration and photosynthetic uptake estimates, estimation of uncertainties, and metadata about the measurements, presented for the first time in this paper. In addition, 206 of these sites are for the first time distributed under a Creative Commons (CC-BY 4.0) license. This paper details this enhanced dataset and the processing methods, now made available as open-source codes, making the dataset more accessible, transparent, and reproducible.Peer reviewe

Global maps of soil temperature.

Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km2 resolution for 0-5 and 5-15 cm soil depth. These maps were created by calculating the difference (i.e. offset) between in situ soil temperature measurements, based on time series from over 1200 1-km2 pixels (summarized from 8519 unique temperature sensors) across all the world's major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (-0.7 ± 2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications

Charakterisierung eines Mini-Lichtbogenbrenners (Characterization of a miniature arcjet heater)

Ein Raumfahrzeug wird beim atmosphärischen Eintritt hohen thermischen Lasten ausgesetzt und benötigt zum Schutz der Struktur ein zuverlässiges Thermalschutzsystem. Für den Entwicklungsprozess neuartiger Materialien für Thermalschutzsysteme ist die Kenntnis der unter den Hochtemperaturbedingungen auftretenden Prozesse wie Ablation oder Pyrolyse, von entscheidender Bedeutung. Im Rahmen der vorliegenden Arbeit wurde das Betriebsverhalten eines am Deutschen Zentrum für Luft- und Raumfahrt entwickelten miniaturisierten Lichtbogenbrenners für Materialtests charakterisiert. Als Kenngrößen für den Betrieb wurden die Strom-Spannungskennlinien für verschiedene Betriebsparameter erstellt und hieraus die Leistungscharakteristik ermittelt. Zudem wurden Druckmessungen zur Untersuchung der Strömungsprozesse der konvergentdivergenten Düse durchgeführt, die Messwerte wurden im Anschluss mit der theoretischen Düsenströmung verglichen. Die auf eine zu untersuchende Materialprobe wirkenden Wärmestromdichten wurden mittels Non-Integer-System-Identification ermittelt. Das Betriebsverhalten wurde sowohl für das bisherige Arbeitsgas Argon als auch für Stickstoff als mögliches Arbeitsgas charakterisiert. Hierbei konnte für die Strom-Spannungs-Kennlinien eine deutliche Abhängigkeit vom Massenstrom des Arbeitsgases und des Kathodenabstands gefunden werden. Für Materialtests wurde ein Betriebszustand mit Argon als Arbeitsgas festgelegt und ausführlich charakterisiert, bei einer Leistungseinkopplung von 2,6 kW konnten eine mittlere spezifische Enthalpie von 11,2 MJ/kg und eine mittlere Wärmestromdichte von 120 kW/m2 ermittelt werden. Beim Betrieb mit Stickstoff wurden bei einer eingekoppelten Leistung von 3,3 kW mit 82 kW/m2 deutlich niedrigere Wärmestromdichten ermittelt. Die Ergebnisse der Messungen werden im Kontext des atmosphärischen Eintritts betrachtet, hierbei erfolgt der Vergleich der Messdaten mit realen Flugtrajektorien. Mit dem charakterisierten Lichtbogenbrenner wurden Versuche mit Ablatormaterialien durchgeführt, das Materialverhalten während des Ablationsprozesses wurde hierbei während des Experiments mit in-situ-Röntgenbildgebung erfasst

Setup of flight experiment of transpiration cooled sharp edge fins on the sounding rocket HIFLIER1

The flight in hypersonic conditions implies important challenges for the vehicle development concerning the thermal protection of the external structures, especially in the case of sharp leading edges, where the short standoff distance of the forming shock waves typically determines severe aero-thermal loads. In the framework of the HIFLIER1 flight research experiment, the DLR Institute of Structures and Design, in collaboration with the High Enthalpy Flow Diagnostics Group at the University of Stuttgart, is responsible for setting up the so-called FinExII module of the sounding rocket, for flight testing of the transpiration cooling technology applied to porous ceramic matrix composite structures as a possible approach for thermal management of sharp leading edges in hypersonic regime. For this purpose, the module will house four fins, whose leading edge is made of an inhouse-developed porous C/C-SiC material, connected to a gas system feeding nitrogen for the transpiration cooling application. The present paper gives an overview of the module design, supported by efficient numerical modelling to estimate the effect of the transpiration cooling, and the pre-flight activities, including the fins manufacturing and pre-flight characterization as well as the rocket module setup

Recent Advancements in Design and Flight Testing of Thermal Protection Systems for Atmospheric Entry at DLR Insitute of Structure and Design

The future of space transportation systems for plane-tary exploration strongly relies on the development of efficient and reliable technologies for thermal protec-tion system (TPS), in order to broaden the capabilities in terms of non-desruptive entry and descent phase both in the atmosphere of the target planet and, for example, for the sample return to Earth. In this framework, data collected during sounding rocket flight experiments are of fundamental importance, both for compensating the deficits of ground experi-mental testing in duplicating a real flight environment and for providing valuable data for the definition and validation of reliable numerical tools. The German Aerospace Center (DLR) has taken part in the last years to several projects for the design and construction of sounding rockets and the opera-tion of flight experiments with the objective of demon-strating advanced technologies and materials for reus-able space transportation systems. In some of the previous flight experiments [1, 2, 3] the objective was to test the TPS for different critical parts in hypersonic conditions with Mach numbers up to 10; other upcom-ing programs [4, 5] focus on technologies for aerody-namic active control, propellant management, ap-proach and landing in subsonic up to supersonic flight with nominal Mach numbers up to maximum 5. After a general overview on these past and current missions, the present work will focus on the activities carried out for the two most recent flight experiments and the corresponding main achivements and meas-ured data obtained during the flight