QUESTION Q24/2 ICT AND CLIMATE CHANGE MONITORING OF CLIMATE CHANGE AND MICROWAVE SATELLITE REMOTE SENSING Satellite altimetry Passive remote sensing Earth Exploration Satellite frequencies
Monitoring of climate change Today, climatology relies increasingly on space technology. Earth observation delivers series of precise, global measurements matching the scale of planetary climate phenomena. Remote sensing is the acquisition of physical data without touch or contact. Focus on the usage of the electromagnetic spectrum and of Earth Observation satellites to monitor some aspects of climate change . Importance of the ITU-R Radio Regulations to protect the Earth Exploration Satellite frequencies. ITU-D SG2 Jean PLA 13 September 2011 Q24/2 ICT and climate change
SATELLITE ALTIMETRY Seventy- one per cent of the planet’s surface is covered by water : key parameter for understanding the forces behind changing weather patterns. Combining oceanic and atmospheric models accurate forecasts on both a short- and long-term basis. Coupling of oceanic and atmospheric models needed to take the mesoscale (medium- distance) dynamics of the oceans weather forecasting beyond two weeks. The oceans are also an important part of the process of climate change: rise in sea levels all over the world is widely recognized as potentially one of the most devastating consequences of global warming. ITU-D SG2 Jean PLA 13 September 2011 Q24/2 ICT and climate change
SATELLITE ALTIMETRY: Hydrology and Land The earliest altimetry missions were dedicated to studying the open ocean and some ice measurements. Every stretch of water (enclosed seas, lakes, rivers, flooding areas...) or even flat surfaces over lands can give valid data. Altimetry: global, homogeneous, repeated measurements (thus enabling systematic monitoring to be carried out over several years ), unhindered by clouds, night or even vegetation. Measured surface heights referenced to the same frame. T echnique is mainly optimized for the ocean (but although specific land re-tracking can be applied): measurements only at the nadir (i.e. just under below the satellite), with a rather narrow footprint -- and averaging everything in that footprint. Over non-ocean surfaces (wet or dry), the accuracy of the altimetry measurements can be degraded to by several centimetres or tens of centimetres, mainly because of the heterogeneity of the reflecting surface (a mix of water and emerged land surfaces). ITU-D SG2 Jean PLA 13 September 2011 Q24/2 ICT and climate change
SATELLITE ALTIMETRY JASON 1, 2 SATELLITES: CNES, NASA, NOAA and EUMETSAT Measurements: ● Distance between the Satellite and the sea ● wave height ● wind speeds Accuracy: Range to surface (cm, corrected) : 2.3 Radial orbit height (cm) : 1.0 Sea-surface height (cm) : 2.5 Wind speed (m/s) : 1.5 ITU-D SG2 Jean PLA 13 September 2011 Q24/2 ICT and climate change
SATELLITE ALTIMETRY Jason-1 satellite was launched on December 7, 2001. Jason-2 satellite was launched on June 20, 2008. Jason-3 in preparation Orbit : Altitude 1336 km, circular, non-sun-synchronous 66° inclination, global data coverage between 66°N and 66°S latitude 10-day repeat of ground track (±1-km accuracy) coverage of 95% of ice-free oceans every 10-days ITU-D SG2 Jean PLA 13 September 2011 Q24/2 ICT and climate change
SATELLITE ALTIMETRY TECHNOLOGY: Estimates of wind and waves from altimeter: analysis of the return from the sea surface: peak backscattered power and shape of the waveforms. Back scatter, σo, from the sea surface: sensitive to small scale surface roughness (short ocean waves). σo is the primary variable used in estimating wind speed. σo sensitive to much larger waves that are only related weakly to the local wind recent algorithms for wind speed also include the altimeter estimate of significant wave height. Significant wave height (SWH) can be estimated using the return pulse by large waves, since the radar signal can be reflected from both the troughs and peaks of waves. The sea surface height is usually estimated from the centre point of the leading edge. ITU-D SG2 Jean PLA 13 September 2011 Q24/2 ICT and climate change
MEAN SEA LEVEL RISE Global mean Sea Level rise is one of the consequences of global warming . Monitoring this level is an application of altimetry, and one of the main issue in Environmental sciences of the 21st century. It is quite difficult to separate the natural variability of the climate from the warming effects . The measurements of the mean sea levels are derived from a period of time of 19 years of satellite earth observation : such a period of time is short . In addition to that, it is necessary to indicate that human induced peturbation is added to the natural climate variability. Climate change signals can be detected only if they are greater than the background natural variability. Detecting global climate change is much more demanding than monitoring regional impacts. Need to have a stable environnment and time series must be stable and accurate. The rise of the sea level is mainly a consequence of past climatic events. The following figure shows that the rise is about 3,2 mm per year, roughly 5.8 cm within 19 years. ITU-D SG2 Jean PLA 13 September 2011 Q24/2 ICT and climate change
MEAN SEA LEVEL RISE ITU-D SG2 Jean PLA 13 September 2011 Q24/2 ICT and climate change
MAP OF SEA LEVELS VARIATION TRENDS SINCE 1992: REGIONAL TRENDS ITU-D SG2 Jean PLA 13 September 2011 Q24/2 ICT and climate change
MEAN SEA LEVEL AS SEEN BY OTHER TECHNIQUES ITU-D SG2 Jean PLA 13 September 2011 Q24/2 ICT and climate change
MEAN SEA LEVEL Since the beginning of the 1990s, altimetry is the main tool for continuous, precise and nearly-global mean sea level monitoring, with moreover regular measurements (every 10 or 35 days). However, other techniques existing a long time before, new ones have appeared that enable to validate altimetry results, and above all to better understand why mean sea level is varying. The longest sea level time series are provided by tide gauges (« Marégraphes »). Some of them (not many) measured the sea level for more than a century. However, they support the effects of the movements of continents, and are very unevenly distributed around the globe: necessarily close to shore, but many more, and the oldest in Europe and the United States ITU-D SG2 Jean PLA 13 September 2011 Q24/2 ICT and climate change
MEAN SEA LEVEL: TIDE GAUGES (« marégraphes ») ITU-D SG2 Jean PLA 13 September 2011 Q24/2 ICT and climate change
MEAN SEA LEVEL (MSL): VALIDATION Sources of error in the Error in the MSL calculation slope of MSL Orbit determination +/-0.15 mm/year Wet troposphere +/-0.30 mm/year Corrections from weather data fields +/-0.10 mm/year Altimetry parameters +/-0.10 mm/year Sea Surface Height bias model +/-0.25 mm/year Total error +/-0.6 mm/year Confidence interval= 90% ITU-D SG2 Jean PLA 13 September 2011 Q24/2 ICT and climate change
MSL VARIATIONS CAUSES water mass variations : water can be added to the ocean, either by increased rain over the ocean, or run-off from the rivers; glaciers melting can also add water Increased evaporation can also decrease the water mass (as well as glaciation, as it happened during last Ice age, when sea level was about 100 m below the nowadays level) temperature variations : water dilates when it warms, which leads to higher sea level. Among other things, it leads to sea level seasonal variations, and also year-to-year variations linked to climate events (e.g. El Niño ). salinity variations : the saltier the water, the denser it is; thus saltier water will have a lower level. Salinity variations can occur by fresh water addition (increased run- off, rain, or ice melting), which decreases salinity, or by increased evaporation, or by glaciation, which increase salinity. ocean circulation changes : changes in sea level can be due to changes in the ocean circulation. ITU-D SG2 Jean PLA 13 September 2011 Q24/2 ICT and climate change
WHAT IS MAKING THE OCEANS RISE? Thermal expansion 1.6 +/- 0.5 mm/yr Glaciers and ice caps 0.77 +/- 0.22 mm/yr Greenland ice sheet 0.21 +/- 0.07 mm/yr Antarctic ice sheet 0.21 +/- 0.35 mm/yr Sum 2.8 +/- 0.7 mm/yr Observed 3.2 +/- 0.6 mm/yr ITU-D SG2 Jean PLA 13 September 2011 Q24/2 ICT and climate change
El nino event http://www.aviso.oceanobs.com/en/newsstand/altimetry-and-doris-applications- in-videos/el-nino/index.html ITU-D SG2 Jean PLA 13 September 2011 Q24/2 ICT and climate change
Latest plot of El Nino situation in the Pacific ocean ITU-D SG2 Jean PLA 13 September 2011 Q24/2 ICT and climate change
Latest plot of El Nino situation: mean sea anomaly La Niña may be back again this year: temperatures in the Pacific are hinting at a continued pattern ITU-D SG2 Jean PLA 13 September 2011 Q24/2 ICT and climate change
Monitoring of the level of the East Africa’s Lakes in connection with El nino events Monitoring the rising of the lake levels in East Africa in late 1997: consequence of heavy rainfall caused by El Niño conditions over the Pacific on the watershed of these lakes. ITU-D SG2 Jean PLA 13 September 2011 Q24/2 ICT and climate change
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