Alert for Price Spikes (ALPS)
The Alert for Price Spikes (ALPS) layer shows the status of commodity prices in markets, highlighting the anomalous values in a four grade scale with increasing severity:
Normal - Stress - Crisis - Emergency
The assumption is that households will face economic challenges in accessing these markets because prices are too high compared to historical and seasonal trends.
The ALPS index is built using data in the VAM price monitoring database.
The ALPS methodology and source data can be found in the Economic Explorer section
of this website.
Rainfall
The 1-month rainfall anomaly layer shows cumulative seasonal rainfall as a percentage of the 20-year average every ten days. Values below 100% indicate drier
than average conditions, above 100% indicate wetter than average conditions. Variations between 90% and 110% are considered as having an inconsequential impact
for crops or pasture and these are represented in white. Otherwise, brown shades indicate below-average rainfall and blue shades indicate above-average seasonal rainfall.
Users can evaluate whether the season is becoming drier than average (blue shades turning lighter or brown shades getting darker) or wetter than average
(brown shades turning lighter or blue shades getting darker).
Rainfall data is derived from the Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS)
rainfall estimate,
produced by the Climate Hazards Group at the University of California, Santa Barbara.
The dataset spans 50°N-50°S latitude and all longitudes, starting in 1981 to the present day. CHIRPS incorporates satellite imagery with ground data
to create gridded rainfall time series at 0.05° resolution for trend analysis and seasonal drought monitoring.
CHIRPS is free to use and easily accessible at this link.
NDVI
The Normalized Difference Vegetation Index (NDVI) layer shows the recent vegetation development compared to the average.
Green shades show areas where vegetation cover is above average, whilst orange and brown shades identify areas where vegetation cover is below normal.
Users can evaluate whether vegetation cover is becoming sparser (lightening greens or darkening oranges) or denser (lightening oranges and darkening greens).
Values between 90% and 110% are considered as being within the range of normal variability.
The NDVI data in use is from the MODIS platforms Terra and Aqua, which provide global coverage since 2000 (Terra) and mid-2002 (Aqua) at roughly a resolution of 5km.
Outputs are produced every 8 days from data with an overlapping 16 day frequency.
The MODIS NDVI CMG data product was retrieved from Earthdata Search, courtesy of:
- NASA EOSDIS Land Processes Distributed Active Archive Center (LP DAAC)
- USGS/Earth Resources Observation and Science (EROS) Center
- Sioux Falls, South Dakota, USA.
Cadre Harmonisé/IPC
Developed by a global partnership, the Integrated Food Security Phase Classification (IPC) is a set of tools and procedures to classify food insecurity.
This evidence-based approach uses international standards that allow food security to be compared across countries and over time.
It is based on consensus-building processes by different actors and provide decision-makers with a rigorous analysis of food insecurity, along with broad objectives
for humanitarian response. It classifies the populations in different phases according to the severity of the situation.
For more information visit http://www.ipcinfo.org.
Population Density
Population data is provided by WorldPop. These are estimates of population density for 2020, derived from a variety of data sources. We use the continental "datasets", a mosaic of all WorldPop country level datasets resampled to 1km resolution, aggregated by VAM's administrative boundaries. National totals have been adjusted to match UN Population Division estimates for each time point. For the methodologies used to produce the estimates please see https://www.worldpop.org/methods.