the watchman Images of the Month - Focus on the Free State Latest vegetation conditions as deduced from SPOT VEGETATION data

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1 I N S T I T U T E F O R S O I L, C L I M A T E A N D W A T E R the watchman I S S U E S E P T E M B E R Latest vegetation conditions as deduced from SPOT VEGETATION data Rainfall for August 2007 Images of the Month - Focus on the Free State Drought Monitoring Considering the current vegetation conditions before the start of the summer rainfall season, we see lower vegetation activity dominant over the Free State Province. Early rainfall is needed for vegetation to recover, with temperatures set to rise. C O N T E N T S : Vegetation conditions 2 News from ISCW The strategic focus of the ARC- Institute for Soil, Climate and Water (ARC-ISCW) is increasing the productive efficiency of agroecosystems, ensuring sustainable use of natural agricultural resources, ensuring food security, reducing poverty and increasing wealth of people dependent on natural resource-based agriculture. The Institute, through its expertise, can assist not only the National Department of Agriculture but also the Provincial Departments of Agriculture in carrying out their responsibilities towards the Conservation of Agricultural Resources Act. (CARA). ARC-ISCW will be demonstrating its capabilities, technologies, experience, expertise and services to assist the Department of Agriculture and Provincial Departments of Agriculture in complying with agricultural and environmental legislation such as CARA and the SUAR Bill, the Agricultural Strategy and ASGISA objectives. This event is scheduled for September 2007 at Maselspoort in the Free State Province. A major objective of this event is to take cognizance of our clients requirements in a view of focused research and development. You are cordially invited to attend this event. Please contact our PRO, Mrs Adri Theron on / or send her an (adril@arc.agric.za) no later than 7 September Rainfall 4 Agrometeorology 6 Remote Sensing 7 CRID 8 Contact details 8 Active Fire Detection A devastating fire occurred in and along the Van Reenen pass on Monday, 27 August Dense smoke caused severe congestion on the N3 highway and people had to be evacuated from the area. The first active fires were detected with the MSG satellite at 10:15, with the peak of activity occurring around 13:30. Umlindi on AGIS A web-based system is currently being developed by the AGIS Development Centre called the Agro-Climate Information system. The system can be accessed through The data on this system is currently updated once a month, but regular updates, every ten days, will soon follow. The AGIS Development Centre is also developing a new online subscription system for the Umlindi Newsletter. This system will allow people to subscribe to the Newsletter online. Subscribers will be notified once the system is fully operational.

2 Vegetation Mapping The Normalised Difference Vegetation Index (NDVI) is computed from the equation: NDVI=(IR-R)/(IR+R) where: IR = Infrared reflectance & R = Red band NDVI images describe the vegetation activity. A decadal NDVI image shows the highest possible greenness values that have been measured during a 10-day period. Vegetated areas will generally yield high values because of their relatively high near infrared reflectance and low visible reflectance. For better interpretation and understanding of the NDVI images, a temporal image difference approach for change detection is used. to p. 3 Figure 1: Normal Vegetation conditions is prevailing over most regions of the country. Lower vegetation activity near Nelspruit is due to the wild fires at the end of last month. Lower vegetation activity can be seen in the northern region of the Kruger National Park, northeast Mpumalanga and along the coast in the Eastern Cape Province. Figure 2: Comparing current vegetation conditions with that of the same period last year indicates much lower vegetation activity throughout the country. This could be contributed to the very high summer and winter rainfall that occurred over large areas of the country in Little to no rain fell over the same areas in Vegetation Conditions Figure 1 Figure 2 P A G E 2 U M L I N D I

3 I S S U E 2 9 P A G E 3 Vegetation Mapping cont... (from p. 2) Figure 3 Figure 4 The Vegetation Productivity Indicator (VPI) is another method to assess the overall vegetation condition. The VPI was developed by C. Sannier and can be summarized as the probability distribution of the NDVI. Interpretation of map legend NDVI values range between 0 and 1. These values are incorporated in the legend of the difference maps, ranging from 1 (lower vegetation activity) to 1 (higher vegetation activity) with 0 indicating normal/the same vegetation activity or no significant difference between the images. Cumulative NDVI maps: Two cumulative NDVI datasets have been created for drought monitoring purposes: Winter - January to December. Summer - July to June Figure 3: Lower than normal vegetation activity can be seen over most of the country for the last three months. The winter rainfall region received good rainfall over the last three months and show anomalously high vegetation activity. Higher vegetation activity can be seen in Northern KwaZulu-Natal and in the central region of the country, from Kimberley towards Cradock and Port Elizabeth. Figure 4: Areas with higher than average vegetation productivity are highlighted in green, and areas with lower than average vegetation activity in red. The VPI compares well with the PASG (figure 3), showing the same trends in vegetation activity for August.

4 Rainfall P A G E 4 Overview: The month can overall be characterized by the warm weather that prevailed for long periods over the interior. Numerous cold fronts influenced the southwestern Cape resulting in above-normal rainfall over most of the winter rainfall area. However, the movement of the systems resulted in less rain eastward. A strong cold front and upper air trough caused heavy rain over the Western Cape on the 6 th. The upper air trough was responsible for thunderstorms over the central parts of the country. Around the middle of the month, some rain was also experienced over the northeastern parts, especially the escarpment, mainly due to a strong high pressure system to the southeast. Especially during the last few days of the month, temperatures soared and because of a northwesterly flow over the country, wild fires occurred frequently. Figure 5 U M L I N D I Figure 6

5 I S S U E 2 9 P A G E 5 Figures 5 & 6: Rain was mostly confined to the coastal areas and winter rainfall area of the country, especially the western part thereof. Some rainfall also occurred over the southeastern and northeastern interior. This represents above-normal rainfall over most of the winter rainfall area and isolated areas in the northeast and southeast. Most of the interior had less than 25% of the average rainfall for August. Figure 7 Figure 7: While the western parts of the winter rainfall area received significantly more rain than during last year, most of the southern parts received significantly less rain than during the same period last year. Figure 8: For the period April to August, the winter rainfall area received above normal rain while most of the summer rainfall area experienced below-normal rainfall. Small areas over the central parts of the country and the coastal areas of KwaZulu-Natal received above-normal rain during this period. Figure 8

6 P A G E 6 Agrometeorology Rainfall The AgroMet Division of ARC-ISCW conducts and implements research in the field of Agrometeorology and Agroclimatology October started with to promote sustainable utilization of the region s climate, soil and water scattered but mainly Spatial Products light thundershowers over Long-term the most of Climate the Surfaces summer - Rainfall rainfall areas. Between - Temperature the 3 rd and the 6 th - heavy Sunshine rain occurred Duration once - Frost again over the south-eastern - Heat Units parts of the country due to an upper Climate air cut-off Monitoring low pressure - Current system 10-daily over surfaces the - southern Comparisons parts. with previous years - Comparisons with the long term Isolated thunderstorms developed Crop Suitability over most of the - summer For various rainfall crops regions during the period Climate up to the Classification 18 th of the - month Köppen due Climate to weak Zones upper air instability over the central regions. By the end of the month, a quasistationary upper air trough to the west of the country was responsible for scattered to widespread thundershowers and rain over especially the central and eastern parts. Cold fronts during the first and last ten days of the Climate Database month caused rain over the winter rainfall area of the Western Cape. Stations - About 500 Automatic weather stations - About 130 Mechanical weather stations - Includes stations from the SAWS and other institutions Reports Various Indices - Hourly - Evapotranspiration - Daily - Chill Units - 10-daily - Heat Units - Monthly - Temperature Thresholds - Annually - Long-term - Wind Rose Disease Warnings Powdery Mildew Downy Mildew U M L I N D I Contact: Chris Kaempffer ARC-ISCW, Private Bag X79, Pretoria 0001 Tel: (012) Fax: (012)

7 I S S U E 2 9 Remote Sensing P A G E 7 Satellite Applications Disaster & Pest Management - Fire monitoring - Locust monitoring Agricultural Applications - Drought monitoring - Crop estimation - Rangeland monitoring Land Cover Applications - Land degradation assessment - Deforestation detection Biophysical Properties - Evapotranspiration - Soil moisture - Temperature mapping Forestry - Forest inventories Cloud - Boundaries, properties, formations and altitude Ocean - Colour, resources and surface temperatures Miscellaneous - Security and intelligence - Media and insurance - 3D modelling Aerial Applications Contact: Terry Newby ARC-ISCW, Private Bag X79, Pretoria 0001 Tel: (012) Fax: (012) terry@arc.agric.za Website: Image Interpretation - Vegetation mapping and monitoring - Degradation mapping - Alien vegetation Low-level Imaging - Precision farming Digital Image Processing - Geo-referencing - Image classification - Information extraction - 3D modelling

8 The Coarse Resolution Imagery Database (CRID) NOAA AVHRR The ARC-ISCW has an archive of daily NOAA AVHRR data dating from 1985 to This database includes all 5 bands as well as the Normalised Difference Vegetation Index (NDVI), Active Fire and Land Surface Temperature (LST) images. The NOAA data are used, for example, for crop production and grazing capacity estimation. MODIS MODIS data is distributed by the Land Processes Distributed Active Archive Center (LP DAAC), located at the U.S. Geological Survey's EROS Data Center. The MODIS sensor is more advanced than NOAA with regard to its high spatial (250 m 2 to 1 km 2 ) and spectral resolution. The ARC-ISCW has an archive of MODIS (version 4) data dating from 2000 to This database includes 16-day composites for NDVI, RED, BLUE, MIR and NIR bands and the Enhanced Vegetation Index (EVI). Other products include Nett Photosynthesis, Leaf Area Index, Active Fire data and Fraction of Photosynthetically Active Radiation data. The ARC-ISCW is in the process of acquiring the new (version 5) MODIS archive. VGT4AFRICA and GEOSUCCESS SPOT NDVI data is provided courtesy of the VEGETATION Programme and the VGT4AFRICA project. The European Commission jointly developed the VEGETA- TION Programme. The VGT4AFRICA project disseminates VEGETATION products in Africa through EUMETCast. ARC-ISCW has an archive of VEGETATION data dating from 1998 to the present. Other products distributed through VGT4AFRICA and GEO- SUCCESS include Net Primary Productivity, Normalised Difference Wetness Index and Dry Matter Productivity data. Meteosat Second Generation (MSG) The ARC-ISCW has an operational MSG receiving station. Data from April 2005 to the present have been archived. MSG produces data with a 15-minute temporal resolution for the entire African continent. Over South Africa the spatial resolution of the data is in the order of 3 km. The ARC-ISCW investigated the potential for the development of products for application in agriculture. NDVI, LST and cloud cover products were some of the initial products derived from the MSG SEVIRI data. Other products derived from MSG used weather station data, including air temperature, humidity and solar radiation. Institute for Soil, Climate and Water Private Bag X79, Pretoria 0001, South Africa 600 Belvedere Street, Arcadia, Pretoria, South Africa The operational Coarse Resolution Imagery Database (CRID) project of ARC-ISCW is funded by the National Department of Agriculture. Development of the monitoring system was made possible through LEAD funding from the Department of Science and Technology. For further information please contact the following: Johan Malherbe , Johan@arc.agric.za Brilliant Petja , Petja@arc.agric.za Adri Theron , iscwinfo@arc.agric.za To subscribe to the newsletter, please submit a request to: dawie@arc.agric.za What does Umlindi mean? UMLINDI is the Zulu word for the watchman. Dawie van Zyl Phone (Office) Phone (Lab) Fax: dawie@arc.agric.za Agro-Climate Information System - For 10-daily digital rainfall and NDVI maps