Overall accuracy of CO₂/H₂O data from open-path eddy-covariance systems is modeled for data analysis. The model is further formulated into CO₂ and H₂O accuracy equations for uses. Based on atmospheric physics and bio-environment, both equations are used to evaluate accuracy of ecosystem CO₂/H₂O data and, as rationales, to assess field CO₂/H₂O zero and span procedures for the systems. The procedures are assessed for measurement improvement. An impractical H₂O span while cold is found unnecessary.

Based on the intercomparison of photoacoustic and cavity attenuation phase shift instruments, this paper has corrected and calibrated the data of recent field measurements. It showed good agreement and close correlation in the optical properties measured from different optical methods, and the scattering coefficient plays a crucial role as the bridge in constructing correlation between both instruments.

The Blue Nile Basin is of vital importance for the whole Nile Basin. The investigation of the impact of climate change on this basin is essential. The Blue Nile Basin annual and monthly temperatures were investigated. Spatial and temporal patterns of changes in extreme temperatures are investigated using 10 meteorological stations' data for the period 1950–2018. The investigation showed that climate change increased temperatures in the basin.

This paper describes GRUAN's strategy for a network-wide change of the operational radiosonde from Vaisala RS92 to RS41. GRUAN's main goal is to provide long-term data records that are free of inhomogeneities due to instrumental effects, which requires proper change management. The approach is to fully characterize differences between the two radiosonde types using laboratory tests, twin soundings, and ancillary data, as well as by drawing from the various fields of expertise available in GRUAN.

IZA is a high-mountain station located in Tenerife (Canary Islands, Spain, at 28.3º N, 16.5º W; 2373 m a.s.l.) and is a representative site of the subtropical North Atlantic free troposphere. It contributes with basic-BSRN radiation measurements, such as, global shortwave radiation, direct radiation, diffuse radiation and longwave downward radiation and extended-BSRN measurements, including ultraviolet ranges, shortwave upward radiation and longwave upward radiation.