Climate Change

A long-term trend in surface temperature is a key indicator of climate change. One limitation of satellite data for climate change studies is data longevity. Nevertheless, this can be partially minimized by the use of data from polar orbiters. LST from AVHRR has been available for nearly 20 years (since NOAA 14).

As mentioned before, NASA has been providing maps of average monthly land surface temperature in degrees Celsius as measured by MODIS on NASA's Terra satellite since the year 2000.

For climate change studies, analyzing anomalies is the best way to find out the trends. NASA also provides maps that compare daytime land surface temperatures in a particular day, week or month compared to the average conditions during a given period between 2001-2010. An example is shown in Figure 37, for August 2015, showing positive anomalies over central Europe.

Fig. 38: LST from the Terra satellite's MODIS instrument for August 2015 as provided by NASA. Places that are warmer than average are red, places that were near-normal are white, and places that are cooler than average are blue. Black means there is no data.

Source: (Images by Jesse Allen, NASA's Earth Observatory using data courtesy of the MODIS Land Group).

Long time series from geostationary satellites

Although they provide long data series, sensors onboard polar orbiter satellites such as AVHRR and MODIS, cannot provide information about the LST diurnal cycle, with only two passages per day.

The data from the sensors onboard the Meteosat First and Second Generation provide a daily LST cycle for over 30 years with 1 h temporal frequency and 5 km spatial resolution, provided that consistency between data from all Meteosat satellites is ensured. LSA SAF and CM SAF have developed a consistent single channel LST retrieval algorithm for all Meteosat sensors (since MVIRI on Meteosat 2-7 was equipped with a single thermal channel, a mono-channel algorithm is used). LST Meteosat Climate Data Record (CDR) will be released in 2017. For more information see Anke Tetzlaff's report from the 6th LSA SAF Workshop: 'Suitability of Meteosat satellite data for climatological LST retrieval'.