Clarifying the role of radiative mechanisms in the spatio-temporal changes of land surface temperature across the Horn of Africa

Temesgen Alemayehu Abera*, Janne Heiskanen, Petri Pellikka, Miina Rautiainen, Eduardo Eiji Maeda

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

8 Citations (Scopus)
125 Downloads (Pure)

Abstract

Vegetation plays an important role in the climate system. The extent to which vegetation impacts climate through its structure and function varies across space and time, and it is also affected by land cover changes. In areas with both multiple growing periods and significant land cover changes, such as the Horn of Africa, identifying vegetation influence on land surface temperature (LST) through radiative changes needs further investigation. In this study, we used a 13-year time series (2001 - 2013) of remotely sensed environmental data to estimate the contribution of radiative mechanism to LST change due to growing season albedo dynamics and land cover conversion. Our results revealed that in taller woody vegetation (forest and savanna), albedo increases during the growing period by up to 0.04 compared with the non-growing period, while it decreases in shorter vegetation (grassland and shrubland) by up to 0.03. The warming impact due to a decrease in albedo during the growing period in shorter vegetation is counteracted by a considerable increase in evapotranspiration, leading to net cooling. Analysis of land cover change impact on albedo showed a regional annual average instantaneous surface radiative forcing of -0.03 +/- 0.02 W m(-2). The land cover transitions from forest to cropland, and savanna to grassland, displayed the largest mean albedo increase across all seasons, causing an average instantaneous surface radiative forcing of -2.6 W m(-2) and -1.5 W m(-2) and a decrease in mean LST of 0.12 K and 0.09 K, all in dry period (December, January, February), respectively. Despite the albedo cooling effect in these conversions, an average net warming of 1.3 K and 0.23 K was observed under the dominant influence of non-radiative mechanisms. These results show that the impact of radiative mechanism was small, highlighting the importance of non-radiative processes in understanding the climatic impacts of land cover changes, as well as in delineating effective mitigation strategies.

Original languageEnglish
Pages (from-to)210-224
Number of pages15
JournalRemote Sensing of Environment
Volume221
DOIs
Publication statusPublished - 1 Feb 2019
MoE publication typeA1 Journal article-refereed

Keywords

  • Albedo
  • Growing period
  • Land cover change
  • Radiative forcing
  • Land surface temperature
  • MODIS
  • CLIMATE-CHANGE
  • COVER CHANGES
  • EAST-AFRICA
  • BARE SOIL
  • ALBEDO
  • VEGETATION
  • FEEDBACKS
  • IMPACTS
  • DEFORESTATION
  • PRODUCTS

Projects

Cite this