# Presentation: 472956

## Use of RARS data in the U.K. Met Office

- Dick Francis   Met Office, UK

*2008 Satellite Direct Readout Conference, Miami, 8-12 December 2008*

**Notes:**
RARS = Regional ATOVS Retransmission System

## Contents

- This presentation covers the following areas:
- Introduction to the Regional ATOVS Retransmission Service (RARS)
- RARS as a WMO coordinated global activity
- Use of RARS data in Numerical Weather Prediction (NWP)
- The future for RARS

## Introduction to RARS

## From EARS to RARS

- EARS proved very successful and very popular with EUMETSAT users (and not just for NWP limited area modeling applications which was the original motivation)
- So it was natural to consider extending the EARS ‘model’ to other geographical regions and to other data types
- This required the engagement and commitment of other organizations and a coordination role

**Notes:**
Initially “EARS” stood for EUMETSAT ATOVS Retransmission System but, when other data types were introduced, EARS became re-defined as EUMETSAT Advanced Retransmission System. The specific ATOVS service is now normally referred to as EARS-ATOVS.

## RARS as a WMO coordinated global activity

## WMO RARS Project

- WMO took an initiative in 2004 to promote the establishment of RARS on a global basis and to coordinate developments
- The top level objective of the initiative is to deliver ATOVS data from at least **90% of global coverage with a timeliness of no more than 30 minutes**
- A RARS Implementation Group has been established
- The WMO Space Programme maintains RARS Project web pages at ...
- 	http://www.wmo.int/pages/prog/sat/RARS.html

## RARS Implementation

- Two regional networks developed, similar to EARS
- Asia Pacific RARS co-ordinated by Australia (BoM) and Japan (JMA)
- South American RARS co-ordinated by Brazil (INPE) and Argentina (CONAE)
- Data distribution is primarily via GTS and broadcast services like EUMETCast (also via FTP over the Internet)
- The RARS Implementation Group focuses on:
- Increasing coverage
- Adopting common standards and practices (and ensuring consistency with WIGOS & WIS)
- Monitoring performance

**Notes:**
It is via the RARS Implementation Group (RARS-IP) that compliance with WMO coding standards and agreed naming conventions is addressed.

## Actual coverage – summer 2008

- EARS-ATOVS

- S. American RARS

- Asia-Pacific RARS

**Notes:**
The coverage analysis is based on a single NOAA spacecraft and uses a maximum instrument zenith angle of 48.33°, corresponding to the AMSU-A instrument.
The colour coding indicates the percentage of the actual satellite passes over a given geographical region, i.e. swaths, that can be received by the proposed station network. A figure of 100% (mauve) indicates that every time the region is in the field of view of the instrument then the image data will be received by the network. A figure of 50% (green) indicates that, on average, every second pass covering the region will be received. So, in summary, areas coloured other than 100% (mauve) can be scanned by over-passing satellites but  the data are not received by the HRPT station (due to the low elevation of the satellite).

## Planned coverage – end 2008

- EARS-ATOVS

- S. American RARS

- Asia-Pacific RARS

**Notes:**
The new contributing HRPT station in the Indian Ocean is Reunion and it forms part of the EARS-ATOVS service.

## Potential coverage – end 2009

- EARS-ATOVS

- S. American RARS

- Asia-Pacific RARS

**Notes:**
Additional coverage is foreseen for north eastern Russia.

## RARS monitoring

- U.K. Met Office routinely monitors RARS data for coverage, consistency and quality
- RARS files are received from BoM, INPE and CONAE via FTP, and from EUMETSAT via EUMETCast
- Data are monitored for consistency by comparing with independently acquired global data
- For each pass, RARS vs. global differences are measured as soon as global data are available (delay 2-3 hours)
- Warnings are generated if mean or standard deviation for AMSU/MHS channels exceed agreed thresholds
- Warnings and daily summaries are emailed to RARS operators

**Notes:**
U.K. Met Office, through its role as lead institute of the NWP SAF, also supplies the ATOVS and AVHRR Processing Package (AAPP) software which is used to pre-process and format the data at the various data collection sites.

## Web based

**Web based**
**monitoring**
**plots**

## Sun Apr 27 2008
Passes processed in last 24 hours
---------------------------------

Asia-Pacific RARS
=================
                          Totals                                Warnings         
Station | NOAA-15  NOAA-16  NOAA-17  NOAA-18 | NOAA-15  NOAA-16  NOAA-17  NOAA-18
------- | -------  -------  -------  ------- | -------- -------  -------  -------
 mel    |    5        3        5        6    |     0      [1]       0        0
 pth    |    4        3        5        4    |     0       0        0        0
 dar    |    3        0        4        5    |    [1]      0        0        0
 tvl    |    3        0        1        4    |    [1]      0        0        0 
 kiy    |    0        0        5        5    |     0       0        0        0
 syo    |    3        0        3        5    |     0       0       [1]       0
 seo    |    0        0        2        3    |     0       0        0        0
 pek    |    0        6        6        6    |     0       0        0        0
 sgp    |    3        4        4        3    |     0      [2]       0        0
 kel    |    4        0        4        5    |    [1]      0       [1]       0
 hkg    |    2        2        3        0    |     0       0        0        0
------------------------------------------------------------------------------------------

South American RARS
===================
                          Totals                                Warnings         
Station | NOAA-15  NOAA-16  NOAA-17  NOAA-18 | NOAA-15  NOAA-16  NOAA-17  NOAA-18
------- | -------  -------  -------  ------- | -------- -------  -------  -------
 cpt    |    0        0        0        2    |     0       0        0        0
 inm    |    0        0        0        4    |     0       0        0       [1]
 cba    |    0        0        0        4    |     0       0        0        0
 etc    |    1        0        4        4    |     0       0        0        0
------------------------------------------------------------------------------------------

EARS-ATOVS
==========
                          Totals                                Warnings         
Station | NOAA-15  NOAA-16  NOAA-17  NOAA-18 | NOAA-15  NOAA-16  NOAA-17  NOAA-18
------- | -------  -------  -------  ------- | -------- -------  -------  -------
 gan    |    6        0        6        6    |    [1]      0        0        0
 sva    |    7        6       14       14    |    [1]      0        0        0
 mas    |    4        4        4        4    |     0       0        0        0
 kan    |   11        8       10        6    |    [2]      0        0        0
 edm    |    9        0        8       10    |    [3]      0        0        0
 ath    |    2        0        4        3    |     0       0        0        0
 wal    |    4        4        4        4    |     0       0        0        0
 gil    |    6        4        9        7    |     0       0        0        0
 mon    |    0        0        3        4    |     0       0        0        0
 lan    |    6        0        6        6    |     0       0        0        0

**Passes processed in last 24 hours**
**---------------------------------**
**Asia-Pacific RARS**
**=================**
**                          ****Totals ****                               ****Warnings****         **
**Station | NOAA-15  NOAA-16  NOAA-17  NOAA-18 | NOAA-15  NOAA-16  NOAA-17  NOAA-18**
**------- | -------  -------  -------  ------- | -------- -------  -------  -------**
** ****mel    |    5        3        5        6    |     0      ****[1]****       0        0**
** ****pth    |    4        3        5        4    |     0       0        0        0**
** ****dar    |    3        0        4        5    |    ****[1]****      0        0        0**
** ****tvl    |    3        0        1        4    |    ****[1]****      0        0        0 **
** ****kiy    |    0        0        5        5    |     0       0        0        0**
** ****syo    |    3        0        3        5    |     0       0       ****[1]****       0**
** ****seo    |    0        0        2        3    |     0       0        0        0**
** ****pek    |    0        6        6        6    |     0       0        0        0**
** ****sgp    |    3        4        4        3    |     0      ****[2]****       0        0**
** ****kel    |    4        0        4        5    |    ****[1]****      0       ****[1]****       0**
** ****hkg    |    2        2        3        0    |     0       0        0        0**
**------------------------------------------------------------------------------------------**
**South American RARS**
**===================**
**                          ****Totals ****                               ****Warnings****         **
**Station | NOAA-15  NOAA-16  NOAA-17  NOAA-18 | NOAA-15  NOAA-16  NOAA-17  NOAA-18**
**------- | -------  -------  -------  ------- | -------- -------  -------  -------**
** ****cpt    |    0        0        0        2    |     0       0        0        0**
** ****inm    |    0        0        0        4    |     0       0        0       ****[1]**
** ****cba    |    0        0        0        4    |     0       0        0        0**
** ****etc    |    1        0        4        4    |     0       0        0        0**
**------------------------------------------------------------------------------------------**
**EARS-ATOVS**
**==========**
**                          ****Totals ****                               ****Warnings****         **
**Station | NOAA-15  NOAA-16  NOAA-17  NOAA-18 | NOAA-15  NOAA-16  NOAA-17  NOAA-18**
**------- | -------  -------  -------  ------- | -------- -------  -------  -------**
** ****gan    |    6        0        6        6    |    ****[1]****      0        0        0**
** ****sva    |    7        6       14       14    |    ****[1]****      0        0        0**
** ****mas    |    4        4        4        4    |     0       0        0        0**
** ****kan    |   11        8       10        6    |    ****[2]****      0        0        0**
** ****edm    |    9        0        8       10    |    ****[3]****      0        0        0**
** ****ath    |    2        0        4        3    |     0       0        0        0**
** ****wal    |    4        4        4        4    |     0       0        0        0**
** ****gil    |    6        4        9        7    |     0       0        0        0**
** ****mon    |    0        0        3        4    |     0       0        0        0**
** ****lan    |    6        0        6        6    |     0       0        0        0**

**Daily summary**
**emailed to**
**RARS operators**

## Use of RARS data in Numerical Weather Prediction (NWP)

## Sounder data are critical for NWP

- Radiances from sounding instruments such as ATOVS are assimilated into all NWP models
- The impact of satellite data on model performance is greater than all the other observation types combined
- The assimilation (of ever increasing volumes) of satellite data now is a major driver for the need for super computer power
- The greatest impact is in the analysis and forecasts of the Southern Hemisphere where conventional observations are most sparse
- Model runs assimilate all observations available by specific cut-off times (U.K. global model cut-off is currently 2 hours 45 minutes and will decrease in future)

**Notes:**
This is just general background information putting the RARS issue into the general context of the use of data from sounding instruments

## Benefits from RARS

- The original motivation for EARS was for use of ATOVS in regional models with stringent requirements for timeliness of observations
- But RARS also provides extra sounding data for *global* model forecast runs (without RARS up to 30% of global ATOVS data would miss the cut-off time)
- In addition RARS provides increased resilience in the event of loss of global data via normal mechanisms
- RARS is a data stream independent from the global allows better QC and identification of instrument problems

**Notes:**
The figure of 30% (ATOVS data received after the model cut-off time) is very variable.

## Improved data coverage using RARS

- _Key_
**Green**: global ATOVS making assimilation cut-off (165 minutes)
**Blue**: as Green + RARS
**Red**: All global ATOVS regardless of arrival time

**Notes:**
A control was run for a month (mid Dec 2007 to mid Jan 2008) in which the ATOVS data used came from the global dataset alone. Other observations were used as normal. Two experiments were then performed: ‘RARS’ in which ATOVS from the RARS network was also included and ‘All ATOVSG’ in which all the global dataset was used regardless of the arrival time. For the RARS experiment forecast impacts of the pressure at mean sea level were small (up to 1.5%), but generally positive. If all the ATOVS data missing the cut off could arrive in time then the benefit is much larger (up to 3.5 %). However this includes MetOp which currently does not disseminate data via HRPT.

## Impact of RARS on forecasts of surface pressure

**Notes:**
A control was run for a month (mid Dec 2007 to mid Jan 2008) in which the ATOVS data used came from the global dataset alone. Other observations were used as normal. Two experiments were then performed: ‘RARS’ in which ATOVS from the RARS network was also included and ‘All ATOVSG’ in which all the global dataset was used regardless of the arrival time. For the RARS experiment forecast impacts of the pressure at mean sea level were small (up to 1.5%), but generally positive. If all the ATOVS data missing the cut off could arrive in time then the benefit is much larger (up to 3.5 %). However this includes MetOp which currently does not disseminate data via HRPT.

Note that the apparent negative impact of RARS at T+120 should be treated with the same level of caution as would a positive impact at this forecast range. [In any case, this phenomenon is no longer visible]. The ‘error bars’ increase significantly as we approach these timescales and any inaccuracies (e.g. calibration) in the observations could be exaggerated.

## Regions of potentially largest impact for RARS

- RMS difference of 500 hPa height between main run analyses: all
- global ATOVS minus global ATOVS arriving before cut-off (2hr 45min)

- Mid-troposphere analysis

**Notes:**
The RMS difference between the All ATOVSG experiment and the control highlights the areas in which the late ATOVS data adjusts the analysis. It suggests that optimal locations for RARS ground stations include the North Pacific and the Southern Ocean.

## The future for RARS

## Need for continuity

- Use of RARS data has a positive impact on NWP performance = absence of RARS data will degrade performance. Continuous improvement to NWP is a key target for all modeling centres.
- Even with ever-increasing super computer power, the introduction of finer resolution NWP models will always mean that observation cut-off times are a serious constraint

## New satellites & new instruments

- A need to secure continuation of RARS
- RARS data will be required from NOAA-N Prime (launch Feb 2009), Metop-B (2011) and Metop-C (2014)
- RARS data will be strongly desired from NPP (Dec 2010) and NPOESS-C1 (2013)
- Requirement diminishes for NPOESS-C2 and later (2016) as the “SafetyNet” system for fast delivery of global NPOESS data will be operational
- Applicability of RARS to other instrument data
- We can draw benefit from the experiences of EARS-IASI service
- Inclusion of ATMS and CrIS data from NPP and beyond is highly desirable and is seen as a natural extension to the concept
- Increase use of DVB-S dissemination (e.g. EUMETCast and FengYunCast) for data types that won’t fit on GTS (e.g. CrIS)

## Thank you for listening