Climate

Frequency and trends of whether parameters over a long time.
Keywords: climate, temperature, humidity, rainfall, precipitations, evapotranspiration, whether forcasting, meteorology, Köppen climate classification, climate risk management.

 Rainfall Monitoring by Region for the African Continent: Eastern Africa 4 December 2008 Maps on monthly total rainfall amount (in millimeters) and monthly rainfall percentage of normals 1961-1990 (in percentage) from August 2004 to October 2008 are available here for download for Eastern Africa. Rainfall data are also available in GeoNetwork for the whole African continent and the following Regions : Northern Africa, Western Africa, and Southern Africa. [more]
Rainfall Monitoring for the African Continent 4 December 2008 Maps on monthly total rainfall amount (in millimeters) and monthly rainfall percentage of normals 1961-1990 (in percentage) are available here for download from August 2004 to October 2008 for the African continent. Rainfall data are also available in GeoNetwork for the following Regions: Northern Africa, Western Africa, Eastern Africa and Southern Africa.An interpolation method (Kriging) is applied to input data. [more]
Global Negative Trend in RUE-adjusted NDVI (1981-2003) 22 October 2008 Land degradation means a loss of net primary productivity but a decrease in productivity is not necessarily land degradation. To distinguish between declining productivity caused by land degradation and decline due to other factors, it is necessary to eliminate false alarms arising from climatic variability and changes in land use and management. Rainfall variability has been taken into account by using both rain-use efficiency(RUE) and RESTREND. [more]
Global Positive Trend of RUE-Adjusted NDVI (1981-2003) 22 October 2008 Land improvement, or bright spots, is preliminarily identified by 1) a positive trend in sum NDVI for those areas where NDVI does not depend on rainfall and 2) for areas where NDVI is correlated with rainfall, a positive trend in rain-use efficiency. [more]
Global Positive Trend of Climate-Adjusted NDVI (1981-2003) 22 October 2008 Land improvement, or bright spots, is identified by combination of: 1) a positive trend in sum NDVI for those areas where NDVI does not depend on rainfall; 2) for areas where NDVI is correlated with rainfall, a positive trend in rain-use efficiency; and 3) a positive trend in energy-use efficiency, i.e., climate-adjusted NDVI. [more]
Global Correlation Between Annual Sum NDVI And Annual Rainfall 1981-2003 22 October 2008 In Global assessment of land degradation and improvement, rainfall variability is taken into account in two ways: by adjustment of NDVI/NPP for rain - use efficiency, and by calculation of residual trends of departures of observed NDVI from values predicted by the rainfall-NDVI relationship (RESTREND). [more]
Global Pattern, Trends and Confidence Levels of NDVI Coefficient of Variation (1981-2003) 22 October 2008 Coefficient of variation (CoV) can be used to compare the amount of variation in different sets of sample data. NDVI CoV images were generated by computing for each pixel the standard deviation of the set of individual NDVI values and dividing this by the mean of these values. It is recommended that the maps should be considered in the field investigation - in particular the land use change during the study period (1981- 2003). [more]
Global Pattern, Trends and Confidence Levels of NDVI Standard Deviation (1981-2003) 22 October 2008 NDVI standard deviation is the root mean square deviation of the NDVI time series values (annual) from their arithmetic mean. It is recommended that the maps should be considered in the field investigation - in particular the land use change during the study period (1981-2003). [more]
Global NPP Loss In The Degrading Areas (1981-2003) 22 October 2008 Land degradation means a loss of net primary productivity (NPP). To provide a more tangible measure of land degradation that may be subjected to economic analysis, the GIMMS data are translated to NPP using MODIS (moderate resolution imaging spectroradiometer) NPP data (Running and others 2004) for the overlapping period 2000-2003; this translation is approximate. A pixel-based NPP loss is estimated for the degrading areas identified by RUE-adjusted NDVI. [more]
Global Residual Trend of Sum NDVI (RESTREND) 1981-2003 22 October 2008 There is a significant negative correlation between RUE and rainfall and RUE fluctuates wildly from year to year so that RUE, used in isolation, says as much about rainfall variability as about land degradation. To avoid the correlations between RUE and rainfall, and to distinguish land degradation from the effects of rainfall variability, Wessels and others (2007) suggest the alternative use of Residual Trends (RESTREND). [more]
Global Change in Rain-Use Efficiency 1981-2003 22 October 2008 Rain-use efficiency (RUE) is considered to make allowance for the effect of fluctuations in rainfall on biomass productivity. RUE may fluctuate dramatically in the short term - often, there is a sharp decline in RUE in a wet year and we assume that the vegetation, whether cultivated or semi-natural, cannot make immediate use of the additional rain. However, where rainfall is the main limiting factor on biomass productivity, we judge that the long-term trend of RUE is a good indicator of land degradation or improvement (Houerou 1984, 1988, 1989; Snyman 1998; Illius and O'Connor 1999; O'Connor and others 2001). [more]
Global Pattern, Trends and Confidence Levels of Annual Sum NDVI (1981-2003) 22 October 2008 The Normalized Difference Vegetation Index data from July 1981 to December 2003 are produced by the Global Inventory Modelling and Mapping Studies (GIMMS) group from measurements made by the AVHRR radiometer on board US National Oceanic and Atmospheric Administration satellites. The fortnightly images at 8km-spatial resolution are corrected for calibration, view geometry, volcanic aerosols, and other effects not related to vegetation cover (Tucker and others 2004). [more]
Global Change In Net Primary Productivity (1981-2003) 22 October 2008 Land degradation is defined as a long-term decline in ecosystem function and measured in terms of net primary productivity(NPP). Long-term NPP measurement is not available; the remotely-sensed normalized difference vegetation index (NDVI) is used as a proxy; its deviation from the norm may serve as an indicator of land degradation and improvement if other factors that may be responsible (climate, soil, terrain and land use) are accounted for. NDVI is a ratio measuring of photosynthetically active green biomass. The higher the NDVI, the more living green biomass can be found. [more]
World maps of climatological net primary production of biomass, NPP 4 August 2006 The new versions of the global maps of net primary production (NPP) are based on the most recent gridded data sets of temperature and precipitation. The maps show NPP for the period 1951 to 2000 based on datasets from CRU and GPCP VASClimO. High resolution maps of NPP (5minx5min) as GeoTiffs are available here for download. [more]
Koeppen's Climate Classification 3 June 2006 The new globally gridded Koeppen climatologies are based on climatological observations (temperature and precipitations) rasterized to grids of 0.5 x 0.5 degrees. They cover 4 different periods and are based on 3 different precipitation datasets. This leads to a total number of 12 rasterized Koeppen climatologies. [more]
Global map of monthly reference evapotranspiration - 10 arc minutes 1 January 2004 Grid with estimated reference evapotranspiration per month with a spatial resolution of 10 arc minutes. The dataset contains mean monthly values for global land areas, excluding Antarctica, for the period 1961-1990. The dataset has been prepared according to the FAO Penman - Monteith method with limited climatic data as described in FAO Irrigation and Drainage Paper 56. The dataset consists of 12 ASCII-grids with mean monthly data in mm/day * 10, and one ASCII-grid with yearly data in mm/year. [more]
Global length of growing periods 1 May 2000 A general characterization of moisture conditions is achieved through the concept of length of growing period (LGP), i.e. the period during the year when both moisture availability and temperature are conducive to crop growth. Thus, in a formal sense, LGP refers to the number of days within the period of temperatures above 5°C when moisture conditions are considered adequate. [more]
Global temperature growing periods 1 May 2000 The Food and Agriculture Organization of the United Nations (FAO) with the collaboration of the International Institute for Applied Systems Analysis (IIASA), has developed a system that enables rational land-use planning on the basis of an inventory of land resources and evaluation of biophysical limitations and potentials. This is referred to as the Agro-ecological Zones (AEZ) methodology. [more]
Global thermal climates 1 May 2000 The thermal climates represent major latitudinal climatic zones. They were obtained through classifying monthly temperatures corrected to sea level (with an assumed lapse rate: 0.55°C/100m). The latitudinal thermal climates distinguished in global AEZ are the following: tropics, subtropics with summer rainfall, subtropics with winter rainfall, temperate, boreal and polar/arctic. The temperate and boreal belts have been further subdivided according to continentality into three classes, namely: oceanic, sub-continental and continental.Data derived from analysis over 37 years. [more]

last updated:  Tuesday, March 17, 2009