# Presentation: 521666

## NPOESS Altimeter OAT Change Requests - May 1, 2005

- Deploy the ALT instrument earlier than C–3 to avoid gap in altimetry measurements
- Change IORD orbital repeat period from 20 to 21 days

## Altimetry & NOAA Goals

- Coast Ocean Forecast System

- Real-Time Surface Currents

- ENSO Coupled-Model

- Hurricane Intensification

- Weather & Water • Commerce & Transportation • Climate Monitoring

- Global Sea Level Rise

## NPOESS Altimeter OAT recommendation 1

- Presently
- First altimeter instrument to be on **C3** satellite - 2013
- Change to
- First altimeter instrument to be deployed by 2010 - **C1, Free Flyer...**
- Jason-2 launch planned for April 2008 - design life is 3 years
- First year of NPOESS altimetry will be used for constructing a new MSS
- The first year of instrument functioning will not be available operationally
- Two impacts:  1) Potential for COMPLETE loss of functionality
- 2) Lack of overlap affects Global Sea Level Rise estimate

- Move altimeter deployment earlier than C3 satellite

**There is an expected data gap between Jason-2 and NPOESS-C3**

## {

| TOPEX |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| ERS-1 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| ERS-2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| GFO |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| Jason-1 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| ENVISAT |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| Jason-2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| NPOESS |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
|  | 91 | 92 | 93 | 94 | 95 | 96 | 97 | 98 | 99 | 00 | 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12 | 13 | 14 | 15 |

- Primary mission

- Projected extended mission

***As of May, 2005***

- NPOESS overlap required

- NPOESS altimeter data not operational (new mean sea surface required)

***Data gap***

## NPOESS Altimeter OAT recommendation 1

- Operational Impact
**DOD**
- Required mesoscale mapping capability for Navy acoustic applications continuously available (without data gaps) by moving the instrument off C3
- Note: a gap in altimeter coverage means an absolute loss of capability, not just a degradation
**DOC**
- Required ability to monitor climate change within 1 mm/yr specifications will be possible by moving instrument off C3

## NPOESS Altimeter OAT recommendation 1

- All systems  use atmospheric forcing from FNMOC/NOGAPS

- 1.0

- 1.6

- 2.5

- 4.0

-  0.6

-   0.4

-   0.3

- 24°N

- 22°N

- 20°N

- 18°N

- 16°N

- 24°N

- 22°N

- 20°N

- 18°N

- 16°N

- 26°N

- 26°N

- 56°E

- 58°E

- 60°E

- 62°E

- 56°E

- 58°E

- 60°E

- 62°E

- 56°E

- 58°E

- 60°E

- 62°E

**SeaWiFS ocean color**

**1/32° NLOM sea surface height (SSH) and surface currents**

- Gulf of
- Oman

- Arabian
- Peninsula

- Iran

**Altimeter data**
**assimilated**

**No assimilation**

- (in cm)

**Oct 3 2002**
**Operational NRL Layered Ocean Model (NLOM) with altimeter SSH data assimilation**

**  ****Oct 3 2002**
**No assimilation of altimeter data**

- Continuous altimeter data are essential input if models are to approximate nature

## NPOESS Altimeter OAT recommendation 1

- Error levels have peaks over 18 dB using climatology as the ocean environment
- Altimeter data lead to a reduction by a factor of 10 in acoustic transmission loss

- Satellite sampling

- Ocean model assimilation

- Acoustic propagation

## NPOESS Altimeter OAT recommendation 1

- Tide Gauge Calibration for
- non-overlapping Altimetry Missions

## NPOESS Altimeter OAT recommendation 1

- from
- Chambers, et al.
- UTCSR, 2004

- Without 2-3 Year Overlap with Jason-2
- NPOESS cannot satisfy 1 mm/yr GSLR requirement

## NPOESS Altimeter OAT recommendation 1

- Tropical Cyclone Heat Potential (TCHP) is the heat within the ocean available to increase the strength of a hurricane
- Cyclone strength is presently poorly predicted
- TCHP significantly improves intensity forecasts
- TCHP can be provided continuously by moving the altimeter off C3

- From
- Gustavo Goni
- NOAA/AOML

| hours | 24 | 36 | 48 | 72 | 96 | 120 |
| --- | --- | --- | --- | --- | --- | --- |
| % | 0 | 4 | 7 | 14 | 17 | 8 |

- Improvement to hurricane intensity forecast using TCHP

## NPOESS Altimeter OAT recommendation 1

- What is required?
- Accommodation study of the altimeter instrument on the C1 platform
- A study to insure that the repeat period change on the C1 satellite will not adversely affect the overall coverage of the constellation
- Shift funding profile for altimeter instrument forward in time
- Rough Order of Magnitude estimate
- 4 man-week’s work to ensure accommodation
- 1 man-week’s work to ensure coverage for other EDRs will be maintained
- Shifting funding profile

## NPOESS Altimeter OAT recommendation 2

- Change IORD to allow for a 21 day repeat period
- Change Orbit spec. from 17 to 21 day repeat period

- IORD EDR 4.1.6.6.7 Sea Surface Height / Topography
**Presently**
- Exact repeat period threshold <= **20** days
- Equatorial track spacing <= 165 km
**Change to**
- Exact repeat period threshold <= **21** days
- Equatorial track spacing <= 165 km

## NPOESS Altimeter OAT recommendation 2

- Operational Impact
**DOD**
- Required mesoscale mapping capability for Navy acoustic applications
- has improved space/time sampling with 21 day orbit.
**DOC**
- Tide aliasing errors for climate change applications reduced with
- 21 day orbit.

## NPOESS Altimeter OAT recommendation 2

- For a single altimeter, there is a trade-off between spatial and temporal sampling
- Additional satellites improve sampling resolution
- The sampling may be optimized to resolve mesoscale eddies
- Previous analyses of mesoscale time and space scales throughout the globe are indicated by the spread of colored dots
- The 21 day repeat period is a better trade-off than the 17 day repeat period

## NPOESS Altimeter OAT recommendation 2

**Reduction in error variance (cm****2****) between 21-day orbit and 17-day orbit**
**Positive values indicate smaller error variance in 21-day orbit**
**Mean reduction is 2.8 cm****2**

- Mesoscale mapping errors are reduced using the 21 day repeat sampling

- Expected interpolation error based on Navy operational MODAS system

## NPOESS Altimeter OAT recommendation 2

- Mapping errors using only TOPEX 10 day repeat (left) and using 3 altimeters (right)
- Improvement in observing SSH leads to reduction in Acoustic Transmission Loss errors
- Expected peak errors are reduced by 1 dB by reducing these mapping errors

- TOPEX only

- TOPEX, GFO, ERS2

## NPOESS Altimeter OAT recommendation 2

- Tidal Aliasing for Sun-Synchronous Orbits

- Alias Period (Days)

## NPOESS Altimeter OAT recommendation 2

- Tide alias frequencies depend on NPOESS repeat period
- Solar tide aliases appear as regional biases and impact sea level rise
- Good repeat periods for tide alias are evaluated by a performance index
- Improved performance occurs in the 21-24 day repeat band
- Changing to 21 day improves tide estimation for non-solar constituents

- from
- Chambers, et al.
- UTCSR, 2002

## NPOESS Altimeter OAT recommendation 2

- What is required?
- A study to insure that the repeat period change on the one satellite will not adversely affect the overall coverage of the constellation
- Rough Order of Magnitude estimate
- 1 week’s work to ensure coverage for other EDRs will be maintained

## POSEIDON 2 ACCOMODATION