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-km <sup>2</sup> 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-km <sup>2</sup> 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

The SBRC-190 a cryogenic multiplexer for moderate-background FIR astronomy

The SBRC 190, a cryogenic multiplexer developed for far-infrared (FIR) photoconductor detectors operating at moderate backgrounds, is described. The circuit is based on the 32-channel CRC 696 CMOS device used on SIRTF. For applications such as encountered on SOFIA or Herschel, the new device permits higher backgrounds, a wider range of backgrounds, faster sampling, and enhanced synchronization of sampling with chopping. A relationship between sampling efficiency and noise requirements needed to achieve background-limited instrument (BLIP) performance is derived. Major design differences relative to the CRC 696 which have been incorporated in the SBRC 190 are: (a) an AC coupled, capacitive feedback transimpedance unit cell, to minimize input offset effects, thereby enabling low detector biases, (b) selectable feedback capacitors to enable operation over a wide range of backgrounds, and (c) clamp and sample & hold output circuits to improve sampling efficiency, which is a concern at the relatively high readout rates required. The paper emphasizes requirements for use on SOFIA, and touches on the design, expected performance, and fabrication of the new multiplexer