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ABC of Altimetry: SSH, SLA, ADT, MSS, MDT

The altimeter measures the ‘Altimeter Range’ which is the distance between the center of mass of satellite to the surface of the Earth (see Figure below). This allows computing the ‘Sea Surface Height’ (SSH) which is the height of the sea surface above the reference ellipsoid. The ‘Satellite Altitude’ refers to the distance of the center of mass of the satellite above a reference point. The reference point will usually be either on the reference ellipsoid or the center of the Earth.
SSH = Satellite Altitude - Altimeter Range – Corrections

The ‘Corrections’ due to environmental conditions need to be applied in order to retrieve the correct ‘Sea Surface Height’. 

The Mean Sea Surface (MSS_N) is the temporal mean of the SSH over a period N. It is a mean surface above the ellipsoid of reference and it includes the Geoid.
MSS_N=<SSH>_N

The Sea Level Anomaly (SLA_N) is the anomaly of the signal around the time-mean component. It is deduced from the SSH and MSS_N :
SLA_N = SSH – MSS_N

The Mean Dynamic Topography (MDT_N) is the temporal mean of the SSH above the Geoid over a period N.
MDT_N = MSS_N – Geoid

The Absolute Dynamic Topography (ADT) is the instantaneous height above the Geoid. The geoid is a gravity equipotential surface that would correspond with the ocean surface if ocean was at rest (i.e. with no currents under only the gravity field). Then, when the ocean is also influenced by wind, differential heating and precipitation and other sources of energy, the ocean surface moves from the geoid. Thus, the departure from the geoid (MDT) provides information on the mean effect on SSH from ocean dynamics.
The ADT is the sum of the SLA_N and MDT_N:
ADT= SLA_N + MDT_N = SSH - MSS_N + MDT_N

The reference period N considered can be changed as described in Pujol et al. (2018). Currently it is 1993-2012.

The Mean profile is the mean of altimeter measurements along the satellite's tracks. It can be used as reference for computing SLA for the same satellite. It is an along-track data (not distributed)
The MSL (Mean Sea Level) is a trend (a number of mm/year), often given with respect to time as a curve.

Reference:
Pujol, M.-I., Schaeffer, P., Faugère, Y., Raynal, M., Dibarboure, G., & Picot, N. (2018). Gauging the improvement of recent mean sea surface models: A new approach for identifying and quantifying their errors. Journal of Geophysical Research: Oceans, 123. https://doi.org/10.1029/2017JC013503 .

Category: Altimetry

/

ABC of Altimetry: SSH, SLA, ADT, MSS, MDT

The altimeter measures the ‘Altimeter Range’ which is the distance between the center of mass of satellite to the surface of the Earth (see Figure below). This allows computing the ‘Sea Surface Height’ (SSH) which is the height of the sea surface above the reference ellipsoid. The ‘Satellite Altitude’ refers to the distance of the center of mass of the satellite above a reference point. The reference point will usually be either on the reference ellipsoid or the center of the Earth.
SSH = Satellite Altitude - Altimeter Range – Corrections

The ‘Corrections’ due to environmental conditions need to be applied in order to retrieve the correct ‘Sea Surface Height’. 

The Mean Sea Surface (MSS_N) is the temporal mean of the SSH over a period N. It is a mean surface above the ellipsoid of reference and it includes the Geoid.
MSS_N=<SSH>_N

The Sea Level Anomaly (SLA_N) is the anomaly of the signal around the time-mean component. It is deduced from the SSH and MSS_N :
SLA_N = SSH – MSS_N

The Mean Dynamic Topography (MDT_N) is the temporal mean of the SSH above the Geoid over a period N.
MDT_N = MSS_N – Geoid

The Absolute Dynamic Topography (ADT) is the instantaneous height above the Geoid. The geoid is a gravity equipotential surface that would correspond with the ocean surface if ocean was at rest (i.e. with no currents under only the gravity field). Then, when the ocean is also influenced by wind, differential heating and precipitation and other sources of energy, the ocean surface moves from the geoid. Thus, the departure from the geoid (MDT) provides information on the mean effect on SSH from ocean dynamics.
The ADT is the sum of the SLA_N and MDT_N:
ADT= SLA_N + MDT_N = SSH - MSS_N + MDT_N

The reference period N considered can be changed as described in Pujol et al. (2018). Currently it is 1993-2012.

The Mean profile is the mean of altimeter measurements along the satellite's tracks. It can be used as reference for computing SLA for the same satellite. It is an along-track data (not distributed)
The MSL (Mean Sea Level) is a trend (a number of mm/year), often given with respect to time as a curve.

Reference:
Pujol, M.-I., Schaeffer, P., Faugère, Y., Raynal, M., Dibarboure, G., & Picot, N. (2018). Gauging the improvement of recent mean sea surface models: A new approach for identifying and quantifying their errors. Journal of Geophysical Research: Oceans, 123. https://doi.org/10.1029/2017JC013503 .

Category: Altimetry

/

ABC of Altimetry: SSH, SLA, ADT, MSS, MDT

The altimeter measures the ‘Altimeter Range’ which is the distance between the center of mass of satellite to the surface of the Earth (see Figure below). This allows computing the ‘Sea Surface Height’ (SSH) which is the height of the sea surface above the reference ellipsoid. The ‘Satellite Altitude’ refers to the distance of the center of mass of the satellite above a reference point. The reference point will usually be either on the reference ellipsoid or the center of the Earth.
SSH = Satellite Altitude - Altimeter Range – Corrections

The ‘Corrections’ due to environmental conditions need to be applied in order to retrieve the correct ‘Sea Surface Height’. 

The Mean Sea Surface (MSS_N) is the temporal mean of the SSH over a period N. It is a mean surface above the ellipsoid of reference and it includes the Geoid.
MSS_N=<SSH>_N

The Sea Level Anomaly (SLA_N) is the anomaly of the signal around the time-mean component. It is deduced from the SSH and MSS_N :
SLA_N = SSH – MSS_N

The Mean Dynamic Topography (MDT_N) is the temporal mean of the SSH above the Geoid over a period N.
MDT_N = MSS_N – Geoid

The Absolute Dynamic Topography (ADT) is the instantaneous height above the Geoid. The geoid is a gravity equipotential surface that would correspond with the ocean surface if ocean was at rest (i.e. with no currents under only the gravity field). Then, when the ocean is also influenced by wind, differential heating and precipitation and other sources of energy, the ocean surface moves from the geoid. Thus, the departure from the geoid (MDT) provides information on the mean effect on SSH from ocean dynamics.
The ADT is the sum of the SLA_N and MDT_N:
ADT= SLA_N + MDT_N = SSH - MSS_N + MDT_N

The reference period N considered can be changed as described in Pujol et al. (2018). Currently it is 1993-2012.

The Mean profile is the mean of altimeter measurements along the satellite's tracks. It can be used as reference for computing SLA for the same satellite. It is an along-track data (not distributed)
The MSL (Mean Sea Level) is a trend (a number of mm/year), often given with respect to time as a curve.

Reference:
Pujol, M.-I., Schaeffer, P., Faugère, Y., Raynal, M., Dibarboure, G., & Picot, N. (2018). Gauging the improvement of recent mean sea surface models: A new approach for identifying and quantifying their errors. Journal of Geophysical Research: Oceans, 123. https://doi.org/10.1029/2017JC013503 .

Category: Altimetry

/

ABC of Altimetry: SSH, SLA, ADT, MSS, MDT

The altimeter measures the ‘Altimeter Range’ which is the distance between the center of mass of satellite to the surface of the Earth (see Figure below). This allows computing the ‘Sea Surface Height’ (SSH) which is the height of the sea surface above the reference ellipsoid. The ‘Satellite Altitude’ refers to the distance of the center of mass of the satellite above a reference point. The reference point will usually be either on the reference ellipsoid or the center of the Earth.
SSH = Satellite Altitude - Altimeter Range – Corrections

The ‘Corrections’ due to environmental conditions need to be applied in order to retrieve the correct ‘Sea Surface Height’. 

The Mean Sea Surface (MSS_N) is the temporal mean of the SSH over a period N. It is a mean surface above the ellipsoid of reference and it includes the Geoid.
MSS_N=<SSH>_N

The Sea Level Anomaly (SLA_N) is the anomaly of the signal around the time-mean component. It is deduced from the SSH and MSS_N :
SLA_N = SSH – MSS_N

The Mean Dynamic Topography (MDT_N) is the temporal mean of the SSH above the Geoid over a period N.
MDT_N = MSS_N – Geoid

The Absolute Dynamic Topography (ADT) is the instantaneous height above the Geoid. The geoid is a gravity equipotential surface that would correspond with the ocean surface if ocean was at rest (i.e. with no currents under only the gravity field). Then, when the ocean is also influenced by wind, differential heating and precipitation and other sources of energy, the ocean surface moves from the geoid. Thus, the departure from the geoid (MDT) provides information on the mean effect on SSH from ocean dynamics.
The ADT is the sum of the SLA_N and MDT_N:
ADT= SLA_N + MDT_N = SSH - MSS_N + MDT_N

The reference period N considered can be changed as described in Pujol et al. (2018). Currently it is 1993-2012.

The Mean profile is the mean of altimeter measurements along the satellite's tracks. It can be used as reference for computing SLA for the same satellite. It is an along-track data (not distributed)
The MSL (Mean Sea Level) is a trend (a number of mm/year), often given with respect to time as a curve.

Reference:
Pujol, M.-I., Schaeffer, P., Faugère, Y., Raynal, M., Dibarboure, G., & Picot, N. (2018). Gauging the improvement of recent mean sea surface models: A new approach for identifying and quantifying their errors. Journal of Geophysical Research: Oceans, 123. https://doi.org/10.1029/2017JC013503 .

Category: Altimetry

/

ABC of Altimetry: SSH, SLA, ADT, MSS, MDT

The altimeter measures the ‘Altimeter Range’ which is the distance between the center of mass of satellite to the surface of the Earth (see Figure below). This allows computing the ‘Sea Surface Height’ (SSH) which is the height of the sea surface above the reference ellipsoid. The ‘Satellite Altitude’ refers to the distance of the center of mass of the satellite above a reference point. The reference point will usually be either on the reference ellipsoid or the center of the Earth.
SSH = Satellite Altitude - Altimeter Range – Corrections

The ‘Corrections’ due to environmental conditions need to be applied in order to retrieve the correct ‘Sea Surface Height’. 

The Mean Sea Surface (MSS_N) is the temporal mean of the SSH over a period N. It is a mean surface above the ellipsoid of reference and it includes the Geoid.
MSS_N=<SSH>_N

The Sea Level Anomaly (SLA_N) is the anomaly of the signal around the time-mean component. It is deduced from the SSH and MSS_N :
SLA_N = SSH – MSS_N

The Mean Dynamic Topography (MDT_N) is the temporal mean of the SSH above the Geoid over a period N.
MDT_N = MSS_N – Geoid

The Absolute Dynamic Topography (ADT) is the instantaneous height above the Geoid. The geoid is a gravity equipotential surface that would correspond with the ocean surface if ocean was at rest (i.e. with no currents under only the gravity field). Then, when the ocean is also influenced by wind, differential heating and precipitation and other sources of energy, the ocean surface moves from the geoid. Thus, the departure from the geoid (MDT) provides information on the mean effect on SSH from ocean dynamics.
The ADT is the sum of the SLA_N and MDT_N:
ADT= SLA_N + MDT_N = SSH - MSS_N + MDT_N

The reference period N considered can be changed as described in Pujol et al. (2018). Currently it is 1993-2012.

The Mean profile is the mean of altimeter measurements along the satellite's tracks. It can be used as reference for computing SLA for the same satellite. It is an along-track data (not distributed)
The MSL (Mean Sea Level) is a trend (a number of mm/year), often given with respect to time as a curve.

Reference:
Pujol, M.-I., Schaeffer, P., Faugère, Y., Raynal, M., Dibarboure, G., & Picot, N. (2018). Gauging the improvement of recent mean sea surface models: A new approach for identifying and quantifying their errors. Journal of Geophysical Research: Oceans, 123. https://doi.org/10.1029/2017JC013503 .

Category: Altimetry