Measurements Of Near-surface Air Temperature Research Articles

Interchangeability of multi-decade skin and surface air temperature trends over land in models

Satellite land surface temperature (Ts ) records have now reached 20+ year length, but their trends may differ from historical records built from in-situ measurements of near-surface air temperature (Tas ). In the ERA5 reanalysis, 60° S–60° N land Ts and Tas trends can differ by up to ±0.06 °C decade−1 over 20 years, depending on the period, or more on smaller spatial scales. Here I use 1979–1998 outputs from ACCESS1-0 climate model simulations with prescribed land Ts to understand changes in Ts and Tas . CO2’s effective radiative forcing causes adjustments that warm Tas relative to Ts . In ACCESS1-0, vegetation enhances the adjustments to CO2 over land. Meanwhile, feedbacks in ACCESS1-0 oppose the adjustments, resulting in small long-term net effects on global temperature estimates. In coupled simulations from other models, there is no agreement on whether Ts or Tas warms more and the most extreme case shows global long-term differences of just 5% between land Ts or land Tas trends. The results contrast with over-ocean behavior where adjustments and feedbacks reinforce each other, and drive larger long-term Tas warming relative to Ts across all models.

Measuring nocturnal near-surface urban heat island intensity in the small, mid-latitude city of Inverness, Scotland

ABSTRACT Few publications have considered the urban heat island (UHI) effect in small settlements. This paper, therefore, presents the findings of a UHI study conducted in the small, mid-latitude city of Inverness, Scotland (population: 63,220). The study aimed to provide an initial appraisal of the scale of UHI phenomena in Inverness and to understand the factors associated with its presence. Mobile vehicular traverses of a study transect were conducted on 30 dates during June, July & August 2019. Measurements of near-surface air temperature were recorded at 19 local climate zone observation points between 20:00 and 23:00 BST. Daily mean UHI intensity (UHII) during the study ranged from 0.7 to 3.5°C, with an overall mean UHII of 1.6°C. Land use characteristics impacted the UHII, with areas with higher fractions of impervious surface cover returning significantly higher air temperatures. UHII increased with the onset of sunset, and the highest UHII occurred on dates with up to 1–2 oktas of cloud cover, low relative humidity, and high cloud base height. The results align with previous studies and comparisons are drawn between Inverness and other settlements globally. Further research in Inverness is recommended to better understand UHI effects and influence national planning policy.

Utilização de sensoriamento remoto em análises de albedo e temperatura de superfície em Londrina - PR: contribuições para estudos de ilha de calor urbana

Este trabalho avaliou o albedo (αs) e a temperatura de superfície continental (Tsup) provenientes de sensoriamento remoto, e a temperatura do ar (Tar) medida in situ no intuito de caracterizar a Ilha de Calor Urbana (ICU) na cidade de Londrina (Paraná). Foram utilizados dados de αs e Tsup obtidos do sensor MODIS, e medições in situ de Tar realizadas entre junho e agosto de 2011 por sensores meteorológicos instalados em 13 locais na cidade. Os dados de αs e Tsup foram utilizados para calcular um índice de urbanização (IU) na região e posteriormente comparado com Tar. A análise dos dados de αs e Tsup foi consistente com as medições in situ, evidenciando sua aplicabilidade na avaliação espaço-temporal de fenômenos acoplados continente-atmosfera, tais como a ICU. A mancha urbana da cidade de Londrina apresentou valores de IU compreendido entre 18 e 20, bem maiores que as áreas mais vegetadas (14 - 16). Nesse sentido, o IU demonstrou-se ser uma metodologia útil para representar a evolução espaço-temporal de áreas urbanas, o que pode propiciar uma avaliação detalhada do impacto da mudança de cobertura de solo no clima local e regional. Além disso, os resultados indicam que dados obtidos via satélite podem auxiliar grandemente na quantificação da ICU, quando dados in situ estiverem indisponíveis.

A two-source time-integrated model for estimating surface fluxes using thermal infrared remote sensing

We present an operational two-source (soil+vegetation) model for evaluating the surface energy balance given measurements of the time rate of change in radiometric surface temperature (T RAD) during the morning hours. This model consists of a two-source surface component describing the relation. between T RAD and sensible heat flux, coupled with a time-integrated component connecting surface sensible heating with planetary boundary layer development. By tying together the time-dependent behavior of surface temperature and the temperature in the boundary layer with the flux of sensible heat from the surface to the atmosphere, the need for ancillary measurements of near-surface air temperature is eliminated. This is a significant benefit when TRAD is acquired remotely. Air temperature can be strongly coupled to local biophysical surface conditions and, if the surface air and brightness temperature measurements used by a model are not collocated, energy flux estimates can be significantly corrupted. Furthermore, because this model uses only temporal changes in radiometric temperatures rather than absolute temperatures, time-independent biases in T RAD , resulting from atmospheric effects or other sources, do not affect the estimated fluxes; only the time-varying component of corrections need be computed. The algorithm also decomposes the surface radiometric temperature into its soil and vegetation. contributions; thus the angular dependence of T RAD can be predicted from an observation of T RAD at a single view angle. This capability is critical to an accurate interpretation of off-nadir measurements from polar orbiting and geosynchronous satellites. The performance of this model has been evaluated in comparison with data collected during two large-scale field experiments: the first International Satellite Land Surface Climatology Project field experiment, conducted in and around the Konza Prairie in Kansas, and the Monsoon '90 experiment, conducted in the semiarid rangelands of the Walnut Gulch Watershed in southern Arizona. Both comparisons yielded uncertainties comparable to those achieved by models that do require air temperature as an input and to measurement errors typical of standard micrometeorological methods for flux estimation. A strategy for applying the two-source time-integrated model on a regional or continental scale is briefly outlined.