Forecast API variables

See the list below of variables available at MetOcean’s Forecast API, click here for the full technical list. The variables may vary according to the model solution available for a given region.

  • Wave direction mean - Mean wave direction of where the waves are coming from.

  • Wave direction peak - Spectral peak direction of the total sea state. The direction from which the most energetic waves are coming. The spectral peak is the most energetic wave in the total wave spectrum.

  • Wave period peak - A period is an interval of time, or the time-period of an oscillation. Also called peak wave period, is the period of the most energetic waves in the total wave spectrum at a specific location.

  • Wave period below-8s peak - Period of the most energetic waves within the wind wave component of a sea. Wind waves are waves on the ocean surface and are the high frequency portion of a bimodal wave frequency spectrum. A period is an interval of time, or the time-period of an oscillation. Wave period is the interval of time between repeated features on the waveform such as crests, troughs or upward passes through the mean level.

  • Wave period above-8s peak - Period of the most energetic waves within the swell wave component of a sea. Swell waves are waves on the ocean surface and are the low frequency portion of a bimodal wave frequency spectrum. A period is an interval of time, or the time-period of an oscillation. Wave period is the interval of time between repeated features on the waveform such as crests, troughs or upward passes through the mean level.

  • Wave direction below-8s peak - Spectral peak direction of the portion of a wave frequency spectrum where periods are below 8s. Direction from which the most energetic waves are coming in the wind wave component of a sea. Wind waves are waves on the ocean surface and are the high frequency portion of a bimodal wave frequency spectrum. The spectral peak is the most energetic wave in the wave spectrum partition.

  • Wave direction above-8s peak - Spectral peak direction of the portion of a wave frequency spectrum where periods are above 8s. Direction from which the most energetic waves are coming in the swell wave component of a sea. Swell waves are waves on the ocean surface and are the low frequency portion of a bimodal wave frequency spectrum. The spectral peak is the most energetic wave in the wave spectrum partition.

  • Wave height - Total significant wave height computed from the wave directional spectrum.

  • Wave height max - Maximum wave height (Hmax) is an estimate of the largest single wave that will occur in a particular sea state.

  • Wave height above-8s - Swell waves are waves on the ocean surface and are the low frequency portion of a bimodal wave frequency spectrum. Significant wave height is a statistic computed from wave measurements and corresponds to the average height of the highest one third of the waves, where the height is defined as the vertical distance from a wave trough to the following wave crest.

  • Wave height below-8s - Significant wave height of wind seas. It is computed from the portion of a wave frequency spectrum where periods are below 8s. Wind waves are waves on the ocean surface and are the high frequency portion of a bimodal wave frequency spectrum. Significant wave height is a statistic computed from wave measurements and corresponds to the average height of the highest one third of the waves, where the height is defined as the vertical distance from a wave trough to the following wave crest.

  • Wave direction directional-spread - Directional spread is the (one-sided) directional width within a given sub-domain of the wave directional spectrum, S(t,x,y,f,theta) where t is time, x and y are horizontal coordinates (such as longitude and latitude), f is frequency and theta is direction. For a given mean wave (beam) direction the quantity approximates half the root mean square width about the beam axis, as derived either directly from circular moments or via the Fourier components of the wave directional spectrum.

  • Wave period at-first-frequency mean - The wave directional spectrum can be written as a five dimensional function S(t,x,y,f,theta) where t is time, x and y are horizontal coordinates (such as longitude and latitude), f is frequency and theta is direction. S has the standard name sea_surface_wave_directional_variance_spectral_density. S can be integrated over direction to give S1= integral(S dtheta) and this quantity has the standard name sea_surface_wave_variance_spectral_density. Frequency moments, M(n) of S1 can then be calculated as follows; M(n) = integral(S1 f^n df), where f^n is f to the power of n. The first wave period, T(m1) is calculated as the ratio M(0)/M(1).

  • Wave period at-second-frequency mean - The wave directional spectrum can be written as a five dimensional function S(t,x,y,f,theta) where t is time, x and y are horizontal coordinates (such as longitude and latitude), f is frequency and theta is direction. S has the standard name sea_surface_wave_directional_variance_spectral_density. S can be integrated over direction to give S1= integral(S dtheta) and this quantity has the standard name sea_surface_wave_variance_spectral_density. Frequency moments, M(n) of S1 can then be calculated as follows; M(n) = integral(S1 f^n df), where f^n is f to the power of n. The second wave period, T(m2) is calculated as the square root of the ratio M(0)/M(2).

  • Current speed northward at-sea-surface - "Surface" means the lower boundary of the atmosphere. A velocity is a vector quantity. "Northward" indicates a vector component which is positive when directed northward (negative southward).

  • Current speed eastward at-sea-surface - “Surface" means the lower boundary of the atmosphere. A velocity is a vector quantity. "Eastward" indicates a vector component which is positive when directed eastward (negative westward).

  • Current speed northward. barotropic - Average current over the full water column / to the bottom of the sea. A velocity is a vector quantity. "Northward" indicates a vector component which is positive when directed northward (negative southward).

  • Current speed eastward barotropic - Average current over the full water column / to the bottom of the sea. A velocity is a vector quantity. "Eastward" indicates a vector component which is positive when directed eastward (negative westward).

  • Sea depth below sea surface - Vertical distance between the sea surface and the seabed as measured at a given point in space including the variance caused by tides and possibly waves.

  • Sea depth below sea level - "Depth_below_X" means the vertical distance below the named surface X. "Mean sea level" means the time mean of sea surface elevation at a given location over an arbitrary period sufficient to eliminate the tidal signals.

  • Sea temperature at surface - Sea surface temperature is usually abbreviated as "SST". It is the temperature of sea water near the surface (including the part under sea-ice, if any).

  • Wind speed eastward at 10m (or 100m) - Eastward wind speed vector component which is positive when directed eastward (negative westward). At 10 meters (or 100 meters) above ground level.

  • Wind speed northward at 10m (or 100m) - Northward wind speed vector component which is positive when directed northward (negative southward). At 10 meters (or 100 meters) above ground level.

  • Wind speed gust - The speed of wind gusts.

  • Precipitation flux - In accordance with common usage in geophysical disciplines, 'flux' implies per unit area, called 'flux density' in physics.

  • Radiation longwave flux downward - The surface called 'surface' means the lower boundary of the atmosphere. 'longwave' means longwave radiation. 'Downward' indicates a vector component which is positive when directed downward (negative upward). Net downward radiation is the difference between radiation from above (downwelling) and radiation from below (upwelling). In accordance with common usage in geophysical disciplines, 'flux' implies per unit area, called 'flux density' in physics.

  • Radiation shortwave flux downward - The surface called 'surface' means the lower boundary of the atmosphere. 'shortwave' means shortwave radiation. 'Downward' indicates a vector component which is positive when directed downward (negative upward). Net downward radiation is the difference between radiation from above (downwelling) and radiation from below (upwelling). In accordance with common usage in geophysical disciplines, 'flux' implies per unit area, called 'flux density' in physics.

  • Cloud cover - Total cloud cover in the atmosphere column. "Area fraction" is the fraction of a grid cell's horizontal area that has some characteristic of interest. It is evaluated as the area of interest divided by the grid cell area. It may be expressed as a fraction, a percentage, or any other dimensionless representation of a fraction. The cloud area fraction is for the whole atmosphere column, as seen from the surface or the top of the atmosphere.

  • Cloud base - A cloud base (or the base of the cloud) is the lowest altitude of the visible portion of a cloud. Cloud base refers to the base of the lowest cloud. Height is the vertical distance above the surface.

  • Air visibility - The visibility is the distance at which something can be seen.

  • Air humidity at 2m - Relative humidity 2 meters above ground level.

  • Air pressure at sea level - Air pressure at sea level is the quantity often abbreviated as MSLP or PMSL. Air pressure is the force per unit area which would be exerted when the moving gas molecules of which the air is composed strike a theoretical surface of any orientation. "Mean sea level" means the time mean of sea surface elevation at a given location over an arbitrary period sufficient to eliminate the tidal signals.

  • Air temperature at surface (or at 2m) - "Surface" means the lower boundary of the atmosphere. The surface temperature is the temperature at the interface, not the bulk temperature of the medium above or below. At 2 m, means 2 metres above ground level.

  • Air pressure at low cloud base - Air pressure at the base of the lowest cloud found in lower troposphere layer.

  • Air pressure at middle cloud base - Air pressure at the base of the lowest cloud found in middle troposphere layer.

  • Atmosphere convective potential energy - Integrated amount of work that the upward (positive) buoyancy force would perform on a given mass of air (called an air parcel) if it rose vertically through the entire atmosphere. Positive CAPE will cause the air parcel to rise, while negative CAPE will cause the air parcel to sink. Nonzero CAPE is an indicator of atmospheric instability in any given atmospheric sounding, a necessary condition for the development of cumulus and cumulonimbus clouds with attendant severe weather hazards.