A Comparative Study of the Bidirectional Reflectance Distribution Function of Several Surfaces as a Mid-wave Infrared Diffuse Reflectance Standard

The Bi-Directional Reflectance Distribution Function (BRDF) has a well defined diffuse measurement standard in the ultraviolet, visible, and near infrared (NIR), Spectralon(trade name). It is predictable, stable, repeatable, and has low surface variation because it is a bulk scatterer. In the mid-wave IR (MWIR) and long-wave IR (LWIR), there is not such a well-defined standard. There are well-defined directional hemispherical reflectance (DHR) standards, but the process of integrating BRDF measurements into DHR for the purpose of calibration is problematic, at best. Direct BRDF measurement standards are needed. This study use current calibration techniques to ensure valid measurements and then systematically investigates the BRDF and its variation for eight potential MWIR diffuse BRDF standards. Diffuseness, repeatability, and reflectance are all considered as required parameters necessary for a di use MWIR BRDF standard. This document shows comparatively that Spectralon is an excellent candidate for a diffuse MWIR BRDF standard

Modelling the spatiotemporal change of canopy urban heat islands

This study models the spatiotemporal change of Birmingham’s urban heat island (UHI) using air temperature measurements made during the HiTemp project to study the atmospheric conditions over the city [1]. The study identifies the causative factors and their contributions to the formation of UHI, based on a number of data used to build 2.5 D model; land cover, land use, geometrical factors and shadow layers. The raw air temperature measurements were filtered, georeferenced and interpolated to create maps of temperature variations. The expected influencing parameters on the development of the UHI were derived and prepared for regression modelling. The results showed that the difference in temperature across Birmingham city through two years of ground measurements (June 2012 – June 2014) reached up to 13.53 °C. The UHI’s appeared daytime and night-time throughout the different seasons for approximately 56% of the total hours during the study period. However, the high intensity events happened during the calm and clear nights. Moreover, buildings’ shadow provided up to 2 °C reduction to the air temperature, while the wind speed and direction are responsible for the size and distribution of hot spots. The built up area contributed to increase the UHI, whereas, the other types of land cover and the geometrical parameters, contributed less

Growing season temperatures over the former Soviet Union

Analyses of daily mean temperatures during the growing season (days >5°C) from about 200 stations over the former Soviet Union indicate that little change has taken place in a number of growing-season-related variables during the last 110 years. We have considered the start (STR), end (END), duration (DUR), and the number of degree-days above 5°C (DD). Annual average temperatures in the region have warmed by about 1°C, but this increase has been confined to the October-to-April period. Time series of the variables at individual stations show that there is little correlation between the start and end dates of the growing season and between the duration and the number of degree-days in the season. Mean May-to-September temperatures at individual stations are shown to be highly correlated with the number of degree-days, implying that the average of an appropriate combination of monthly temperatures can be used as a proxy for the number of degree-days when daily data are not available. The low correlation between degree-day counts and growing season duration in time series at all the stations is surprising given the strong spatial dependence between the 1950–1989 averages of the variables at all the stations. The results have implications for studies concerned with the impacts on growing season temperatures of future climate change