Satellite Remote Sensing of Permafrost

by Lindsay McCord

Using a new approach to measure the extent of permafrost (permanently frozen soil), researchers have confirmed consistent widespread decline in stable permafrost that coincides with regional climate warming. This model provides greater resolution for looking at the condition of permafrost on a regional scale, and combined with other models, allows us to understand how permafrost is reacting to rising temperatures. Permafrost occupies roughly a quarter of land area in the Northern Hemisphere, over 40% of which is vulnerable to melting according to the new model. Twenty percent of permafrost land area is at a moderate risk, while 23% is facing severe degradation risk. In addition, the study found that permafrosts in boreal forests are more vulnerable than the more northern tundra permafrost. The model further confirms significant increasing regional trends of permafrost melting in the past 30 years in response to climate warming. Continue reading

The Power of Green Space for Reducing Surface Temperature in Tel Aviv, Israel

by Dan McCabe

One key objective of sustainable urban planning is to limit the urban heat island (UHI) effect, the increased local temperature in highly built areas due to differences from the natural environment in the absorption and reflection of solar energy at the surface. Previous research has displayed the value of large urban parks in controlling temperature in cities, but less is known about the effect of smaller green spaces. In order to investigate how vegetation and construction levels impact UHI severity, Rotem-Mindali et al. (2015) used ten years of remotely sensed data from two NASA satellites to analyze the relationship between different land uses and land surface temperature (LST) in Tel Aviv, Israel. The authors compiled information on local LST and Normalized Difference Vegetation Index (NDVI), a measure of vegetation cover, and used it to search for a correlation between land use type and mean surface temperature for summer nights. In their analysis, they found an enormous difference of 13°C in mean temperature among different locations in Tel Aviv. There was a strong correlation between land use type and LST, with the most vegetated regions experiencing much lower average temperatures than highly built regions. Continue reading