Operational Oceanography Requirements

Table 2.3 from Le Traon et al. (2006) summarises weather, climate and operational oceanography requirements for sea surface temperature.

In order to meet the key requirements for SST no single sensor is adequate. To remedy this, GHRSST-PP has established an internationally accepted approach to blending SST data from different sources that complement each other (see previous section). For this to work effectively, there must be an assemblage of four distinct types of satellite SST missions in place at any time, as defined in Table 2.4 (from Le Traon et al. 2006).

Table 2.3 User requirements for SST provision

Application area Temperature Spatial resolution Revisit time Priority accuracy (K) (km)

1. Weather prediction 0.2-0.5 10-50 6-12 h High

2. Climate monitoring 0.1 20-50 8 day High

3. Ocean forecasting 0.2 1-10 6-12 h High

Table 2.4 Minimum assemblage of missions required to meet the need for operational SST

SST mission type

Radiometer

Nadir

Swath width

Coverage/

wavebands

resolution

revisit

A.

Two polar orbiting

3 thermal IR

~1 km

~2,500 km

Day and night

meteorological satellites

(3.7, 11,

global

with infra-red radiometers.

12 ^m), 1

coverage

Generates the basic global

near-IR, 1 Vis

by each

coverage

satellite

B.

Polar orbiting dual-view

3 thermal IR

~1 km

~500 km

Earth cover

radiometer. SST accuracy

(3.7, 11,

age in ~4

approaching 0.1 K, used as

12 ^m), 1

days

reference standard for other

near-IR, 1

types

Vis, each

with dual

view

C.

Polar orbiting microwave

Requires chan

~50 km

~1,500 km

Earth cover-

radiometer optimised for

nels at ~7 and

(25 km

age in 2

SST retrieval. Coarse reso-

~11 GHz

pixels)

days

lution coverage of cloudy

regions

D.

Infra-red radiometers on

3 thermal IR

2-4 km

Earth disk

Sample

geostationary platforms.

(3.7, 11,

from

interval

Spaced around the Earth

12 ^m), 1

36,000 km

<30 min

near-IR, 1 Vis

altitude

The priority expressed by the international SST community, through GHRSST, is to continue to provide a type B (ATSR class) sensor. Its on-board calibration system and especially its dual-view methodology allow AATSR to deliver the highest achievable absolute accuracy of SST, robustly independent of factors such as stratospheric aerosols from major volcanic eruptions or tropospheric dust, which cause significant biases in other infra-red sensors. Because its absolute calibration (for dual view) is better than 0.2 K it is used for bias correction of the other data sources before assimilation into models or analyses. A type C sensor (microwave) is also required beyond AMSR-E on Aqua.

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