# Presentation: 376967

## Jordan C. Alpert,	NOAA/NWS/EMC	jordan.alpert@noaa.govKrishna V. Kumar,  NOAA/NWS/NCO Yukuan Song, NWS/OST/SEC											16th Conf. NWP J9.2  12/09//03

**where the nation’s climate and weather services begin**

- Jordan C. Alpert,	NOAA/NWS/EMC	_[jordan](mailto:jordan.alpert@noaa.gov)__[.alpert@noaa.](mailto:jordan.alpert@noaa.gov)__[gov](mailto:jordan.alpert@noaa.gov)_Krishna V. Kumar,  NOAA/NWS/NCO Yukuan Song, NWS/OST/SEC											16th Conf. NWP J9.2  12/09//03

## NEXRAD WSR-88D RADARS

*WSR-88D raw radar radial wind represent a rich source of high resolution observations. *

*First task is obtaining quality returns from the radars at a *
*central site for model ingest **(Alpert et al., 2003).*

## NEXRAD WSR-88D RADARS (continued) 

- 158 operational NEXRAD Doppler radar systems deployed throughout the United States.
- These observations warn people about dangerous weather and its location.
- The doppler radars provide high resolution estimated radial velocity data in addition to reflectivity.
- The resolution of the radar radial wind is  1/4 km by 1 degree of azimuth with vertical structure information from 16 tilt angles.
*Seven hundred million observations:  4 X 200 km X 150 radars X 360 deg X 16 tilts per radar scan, every ~8 minutes or  >0.1 T reports/day.*

**Notes:**
If it has not happened yet let this be the among early casual (offhand) use of Terabyte (T) as a unit.

## What is a Superob and why do we need it.

- Assimilation of Radar observations for initialization of weather forecast models (Purser, et al., 2000) involve processing each datum with repetitive interpolations from the analysis grid to its location and back again.
- The NCEP Operational Meso-Eta at 12 km obtains initial conditions form the Eta Data Assimilation System, a 3-dimensional variational analysis of conventional and non-conventional observations.
-       *There is a significant degree of redundant information in the radar radial wind observations.*

*To improve our assimilation of observations for weather *
*forecast models, meso-scale (small scale) phenomena need *
*to be defined in the initial condition of  the model.*

## What is a Superob and why do we need it.  (continued)

- Computer resources and storage expended on mutually redundant data could be better spent on improving other aspects of an assimilation system (Purser, et al., 2000)
- It is desirable to compress the data and use the highest precision to minimize degradation of the information content and minimize the band width to transmit the data to a central site.

*  **Redundant observations impose a computation burden:*

*The term for a surrogate datum which replaces several *
*partially redundant actual data is a “super observation” *
*or “SUPEROB”.*

**Notes:**
NASA and NOAA have fast lines between them!

## Level 3 vs Level 2.5 super-ob radial wind data

- Super-obs have been applied to operational analysis at NCEP from the NEXRAD Information Dissemination Service (NIDS), which we call Level 3 data having 4 bits of precision for each radar radial wind return.
- We designate the super-ob created by utilizing all the precision at each radar as Level 2.5 and transmit the report with 16 bits of precision according to the following table.
- We compare these 2 data sets and a “No radar” case using the Eta Data Assimilation System (EDAS) analysis and Meso-Eta forecast model in operational configuration with resolution of 12 km.

## Adaptable Parameters for the Level 2.5 Superob Product

- Time Window	    60 minutes    	[5-90 min]
- Cell Range Size	    5 km		[1-10 km ]
- Cell Azimuth Size	    6 degrees		[2-12 deg]
- Maximum Range	    100 km		[60-230 km]
- Minimum Number
- of  points required      50 unitless 	[20-200]

## Experimental results of the Level 2.5 Super-ob

- The EDAS is started 12-h before initial condition time on 28OCT2003, assimilating all conventional and non-conventional observations.
- A 3-h window of radar radial wind observations was used  (1 1⁄2 hours on either side of 12Z) to gather the radar winds.
- A system for checking duplicate reports and quality control in terms of a gross check based on the standard deviation within the super-ob is in place.
- The location of precipitation is shown from a 12-h forecast past the initial time since radial wind returns are increased in areas which have precipitation along the northern US.  Note the region of convection along the coast.

## Eta 12-h forecast MSLP (hPa) and Accumulated precipitation rate verifying 29OCT 2003 00Z.

**Eta 12-h forecast MSLP (hPa) and Accumulated precipitation rate verifying 29OCT 2003 00Z.**

**Notes:**
Animation ON the Slide

## Fig 2.  Difference in the analysis (00) of wind magnitude between the level 2.5 and level 3 super-ob are shown in the color fill contours and the arrows show the vector difference of the wind fields at 700 hPa

***Fig 2.  Difference in the analysis (00) of wind magnitude between the level 2.5 and level 3 super-ob are shown in the color fill contours and the arrows show the vector difference of the wind fields at 700 hPa***

**Notes:**
Animation ON the Slide

##  Fig 3.  Difference in the analysis (00) of wind magnitude between the level 3 and No radial wind are shown in the color fill contours and the arrows show the vector difference of the wind fields at 700 hPa. 

** *****Fig 3.  Difference in the analysis (00) of wind magnitude between the level 3 and No radial wind are shown in the color fill contours and the arrows show the vector difference of the wind fields at 700 hPa.***** **

**Notes:**
Animation ON the Slide

## Fig 4.  Difference in the Eta forecasts at 36-h of wind magnitude between the level 2.5 and level 3 super-ob are shown in the color fill contours and the arrows show the vector difference of the wind fields at 700 hPa 

***Fig 4.  Difference in the Eta forecasts at 36-h of wind magnitude between the level 2.5 and level 3 super-ob are shown in the color fill contours and the arrows show the vector difference of the wind fields at 700 hPa***** **

**Notes:**
Animation ON the Slide

## Fig 5.  Difference in the Eta foreasts at 36-h of wind magnitude between the level 3 and No radial wind are shown in the color fill contours and the arrows show the vector difference of the wind fields at 700 hPa. 

***Fig 5.  Difference in the Eta foreasts at 36-h of wind magnitude between the level 3 and No radial wind are shown in the color fill contours and the arrows show the vector difference of the wind fields at 700 hPa.***** **

## For the analysis generated winds from the Radar Radial Wind reports, the number of analysis wind increments greater (magnitude) than the conventional analyzed wind for all locations.

*For the analysis generated winds from the Radar Radial Wind reports, the number of analysis wind increments greater (magnitude) than the conventional analyzed wind for all locations**.*

- There is only one direction where the regular wind will be identical to the radial wind otherwise, we can not uniquely compose the radial winds into regular wind vectors.  However, the EDAS uses the information of how the regular wind increments are related to the radial winds to make an optimal decision of how the observed radial wind projects onto the regular winds.* *

## Summary

- The level 2.5 radar radial wind super-ob product, composed at each WSR88D radar site, are received at NCEP and used in the EDAS analysis with other remotely sensed and conventional observations, providing a high resolution wind component.
- In addition to experiments run with and without the presence of the radial winds, we compare with the level 3 radar feed and no radar data present for one period and a 36-h meso-Eta forecast.
- The results show that the level 2.5 super-ob provides a larger number of suitable super-obs compared with the level 3 data and provides high resolution wind differences that are “drawn” for in the variational analysis.
- Experiments to test accuracy in the high resolution forecasts including verification to rain gauge observations are underway.
- Location of plots and pre-print.  _[http://wwwt.emc.ncep.noaa.gov/gmb/wd23ja/research/radar/](http://wwwt.emc.ncep.noaa.gov/gmb/wd23ja/research/radar/)_
- http://wwwt.emc.ncep.noaa.gov/gmb/wd23ja/presentations