WINETECH Technical Yearbook 2020

Using thermal satellite land surface temperature to supplement weather station temperatures in the Western Cape (PART 2)

LAND SURFACE TEMPERATURE ANOMALY Land surface temperature is how hot or cold the ground feels to the touch. An anomaly is when something is different fromaverage. The land surface temperature anomalymap below, left for December 2019 shows how that month’s average temperature was different from the average temperature for all Decembers between 2001 and 2010. Highlighting where earth’s surface was warmer or cooler in the daytime than the average from 2001-2010. Warmer than average (red), areas near-normal (white) and places cooler than average (blue). (Sources: Image – NASA; Data – MODIS Satellite, https://neo.sci.gsfc.nasa.gov.)

This study focused on integrating climate and thermal satellite remote sensing data to assess the reaction of the grapevine to a changing environment. SATELLITES PROVIDING ADDITIONAL INFORMATION Climate in the Western Cape is dynamic due to the variation of topography, prox- imity to the ocean and the sea breeze effect. The current meteorological network is not a dependable source in terms of distribu- tion and consistency of data accuracy due to factors such as financial constraints, vandalism of some stations, out-dated equipment and lack of efficient monitoring of stations. The weather station network in the Western Cape has degraded signifi- cantly over the past 10 years, with almost half the stations lost around the year 1998. There is an urgent need for more weath- er stations in the complex terrain of the Western Cape, but also to find an alterna- tive temperature resource to supplement

current weather station networks. The application of traditional geospatial inter- polation methods in dynamic terrains re- main challenging and difficult to optimise and the accuracy will be highly dependent on station network inputs. The use of land surface temperature (LST) maps from satellites have been used as alternative resource supplement weather station (WS) temperatures in areas of complex terrain. The availability of continuous climate and weather data at an applicable spatial and temporal level is also crucial to support studies on grapevine phenology, growth and ripening models. This can be achieved by in- tegrating existing weather station networks and remote sensing resources. The study aimed to evaluate the use of satellite LST to supplement WS temperature to aid adap- tion strategies. One of the most important potential applications of the LST retrieved from satellite data is to validate and improve the global meteorological model prediction.

MAY 2020

TARA SOUTHEY: Centre for Geographical Analysis, Department of Geography and Environmental Studies, Stellenbosch University, Stellenbosch KEYWORDS: Climate, terrain, remote sensing, innovation

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