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38 terms

Agroclimatology

A field in the interdisciplinary science of agrometeorology, in which principles of climatology are applied to agricultural production systems. Its origins relate to climate’s foremost role in plant and animal production.

Agroecology

The study of agricultural ecosystems and their components as they function within themselves and in the context of the landscapes that contain them.

Anomaly

Something that deviates from what is standard, normal, or expected. There are different types of anomalies:

• Difference from average: This is the actual observation minus the long-term average. Difference from average is useful for quantifying deficits and surpluses in the same units as the original observation. 0 = no difference; positive means above average; negative means below average.

• Percent of average: This is the actual observation divided by the long-term average, and multiplied by 100 (to convert to percent). Percent of average is useful for quantifying deficits and surpluses in a relative manner. 100 = same as average; >100 means above average, <100 means below average.

• Standardized anomaly: This is the difference from average divided by the standard deviation. Seasonal forecast maps may present the standardized anomaly. The Standardized Precipitation Index (SPI, a commonly used drought measure) uses a standardized anomaly.

Atmospheric circulation

The flow, or movement, of a fluid (e.g., liquid or gas) in or through a given area or volume.

Climate

Average weather over a long period of time: the composite or generally prevailing weather conditions of a region, throughout the year, averaged over a series of years.

Climate mode

A description of one aspect of the way Earth’s climate behaves. Identifiable characteristics include variations in temperature, precipitation, and wind speed/direction. An example of a climate mode is the El Niño Southern Oscillation (ENSO).

Climatology

The study of climate, scientifically defined as weather conditions averaged over a long period of time. However, when we say we expect climatology in terms of forecasts, these are not simply average conditions, but include the range of variability in rainfall quantity, spatial distribution, and temporal distribution that are historically possible for a region.

Coefficient of variation (CV)

The standard deviation divided by the mean. This measure puts the variability in a context of the average rainfall. Areas with large variability relative to the mean represent locations especially vulnerable to seasonal variation. Coefficient of variation is a useful statistic for comparing the degree of variation from one data series, or one location, to another, even if the means differ.

Corn

Also, Maize

Maize is the plant and corn is the kernel or grain, but corn can refer to kernels of different plants, not just maize. In some countries, including North America, maize and corn are used interchangeably, but this is not the case in most parts of the world. In general, we use maize when referring to the crop.

Crop phrenology

Crop phenology is the study of periodic plant lifecycle events and how these are influenced by seasonal and interannual variations in climate, as well as habitat factors (such as elevation).

Crop tours

A tool used to assess conditions in designated areas to help gauge the impact on food security and strengthen FEWS NET assumptions about the upcoming seasons.

Dekad

Ten-day period, usually referring to a period of rainfall, starting on the first day of the month. Every month is composed of exactly three dekads. The last dekad of the month comprises days 21 through the end of the month, and can contain 8 to 11 days.

Dipole

Two opposing patterns in space.

Drought

A drought is a period of below-average precipitation in a given region, resulting in prolonged shortages in the water supply, whether atmospheric, surface water or ground water. This document, however, makes a distinction between a single failed rainy season and consecutive failed rainy seasons; the latter is referred to as a drought.

Dynamical forecasts

Dynamical models use laws of physics and observed conditions to estimate future conditions.

Ensemble forecast

An ensemble forecast is either a collection of model runs (using the same model) started from slightly different initial conditions, or a collection of model runs using different models. This tests the strength of forecasts; if ensembles give similar results (a convergence of evidence), then we have confidence in the forecast.

Forecast skill

Skill is measured by calculating the difference between a model forecast and observed conditions. An acceptable threshold of skill is chosen by a person responsible for running a model. The threshold for skill is subjective. Model runs exceeding the defined threshold of skill are considered to have skill and are therefore reliable for predicting the climate.

Groundnuts

A variety of legumes that produce seeds on the ground. Peanuts are a type of groundnut.

Indian Ocean Dipole (IOD)

An irregular oscillation of sea surface temperatures and related atmospheric circulation in the Indian Ocean.

Inter-tropical convergenze zone (ITCZ)

The point at which air from both hemispheres comes together. When air comes together at the ITCZ, it is forced to rise, which results in clouds and precipitation. The ITCZ moves north and south with the seasons, and is the primary cause of weather/climate and rainfall over the tropics.

Inter-tropical front (ITF)

The leading edge of the ITCZ. The rainfall associated with the ITCZ is always equator-ward of the ITF.

Long-cycle crops

Crops that mature in greater than 90 days, such as sorghum and corn. 

Meridional

In meteorology, a flow, average, or functional variation taken in a direction that is parallel to a line of longitude, along a meridian, northerly or southerly.

Monsoon

A thermally driven wind arising from differential heating between a land mass and the adjacent ocean that reverses its direction seasonally.

Normalized Difference Vegetation Index (NDVI)

A vegetation index commonly used as an indicator of drought. NDVI is a measure of vegetation greenness calculated by a normalized ratio between red and near infrared (NIR) radiation. Healthy, photosynthetic vegetation reflect NIR radiation and absorb red light in the visible spectrum.

Oscillation

In meteorology, oscillation is a shift in the position of high and low pressure systems, usually in the same place. These are often described using an index (often a single number that represents the distribution of temperature and pressure over a wide area, usually over the oceans, such as the El Niño-Southern Oscillation, North Atlantic Oscillation, or Pacific Decadal Oscillation).

Probabilistic forecast

Identifying the likelihood of a specific event. Probabilistic forecasts capture the likelihood of rainfall being in a given tercile of the historical distribution. It allows the forecaster to identify shifts in the likelihood of events based on certain conditions.

Rain

Also, Precipitation

Rain is water that falls in drops condensed from vapor in the atmosphere. Refer to this as precipitation, rather than rain.

Rainfall

The amount of precipitation, usually measured by depth in millimeters.

Rains

An area’s rainy season.

Remote sensing

The collection of data on an object or area using sensors that can be handheld or mounted aboard drones, airplanes, or most commonly, satellite systems. Sensors on satellites orbit around Earth to observe climate, vegetation, and rainfall dynamics. Sensors detect and classify objects on land and oceans and in the atmosphere by receiving signals (for example, electromagnetic radiation reflected from Earth). Remotely sensed data are useful for assessing crop conditions and drought severity, among a range of other climatic and phenological factors.

Resources utilization

Minimal degradation of resources (e.g. soil, forests, water a) in agricultural production and processing.

Short-cycle crops

Crops that mature generally in 90 days or less, such as wheat, barley, and teff.

Spatial variability

Changes in climate across a landscape.

Statistical forecast

Statistical forecasts use previously derived mathematical relationships between two or more variables to produce an estimate of one of those variables given knowledge of the other variables.

Teleconnections

The concept of interrelated climate conditions that cross long distances.

Temperature gradient

A temperature gradient (e.g., sea surface temperature) is a quantity that describes in which direction and at what rate the temperature changes the most rapidly around a particular location. The temperature gradient is expressed in units of degrees (on a particular temperature scale) per unit length.

Temporal variability

Changes in climate over time. Temporal variability indicates changes in values over time and can include changes in the mean (i.e., trend) or the range. Changes between years are referred to as inter-annual variability, and changes within a season are intra-annual variability.