modis winds applications to nwp/data assimilation studies; fairbanks, 10/08/2003 lars peter...

MODIS Winds Applications to NWP/Data Assimilation studies; Fairbanks, 10/08/2003

Lars Peter Riishojgaard

Yan-Qiu Zhu

Global Modeling and Assimilation Office

NASA Goddard Space Flight Center

Preparation for operational assimilation MODIS winds in the DAO


Overview

Data assimilation at Goddard and the JCSDA

Characteristics of the MODIS winds

Results from pre-operational testing

Summary and outlook


GMAO

New Office at Goddard, formed via a merger of the DAO and NSIPP (NASA Seasonal to Interannual Prediction Project)

Head of Office: Michele Rienecker Modeling

New model targeted for 04; based on fv dynamical core, but with NWP-tuned physics

Analysis Last PSAS-based system being frozen Next system will be based on GSI developed at EMC


MODIS winds pilot period assimilation experiments in the DAO

Control (all standard observations; no MODIS winds)

MODIS winds used “as is”; no filtering, no modification

Interactive height assignment with pmax=150 hPa

Interactive height assignment with pmax=75 hPa


Preparation for operational assimilation of MODIS winds

Extensive experimentation with near-real time winds provided by CIMSS starting 07/02/2002 with versions 1.3r6 and 1.4r1 of the fv-DAS

Main changes with respect to 1.2r5 (pilot period) Increased weight given to ITOVS Additional ITOVS data in polar areas Modified background error covariance

Main metrics Consistency of data delivery Quality of MODIS winds Contribution to forecast skill


MODIS experiments

I. Basic - MODIS winds used "as is"

II. Height adjustment - the heights of MODIS winds are adjusted by minimizing a cost function

III. Quality indicator-based selection; only MODIS winds with qi larger than 0.80 are used

IV. Retuned o; error for MODIS wind is tuned using maximum likelihood technique

V. “ECMWF filtering”: over land winds used above 400 hPa; over sea, IR winds above 700 hPa and WV winds above 550 hPa

VI. DAOTOVS exclusion: Interactive TOVS retrievals beyond 65S removed


Experimental results

Innovations (observation minus forecast residuals) RAOB heights and winds ITOVS heights MODIS winds

Impact Troposphere Stratosphere

Forecast skill


MODIS IR U, V innovations for NH control (solid), MODIS; Arctic


MODIS WV U, V innovations for NH control (solid), MODIS; Arctic


RAOB U, V innovations for control (solid), MODIS; Arctic


RAOB U, V innovations for control (solid), MODIS; SP


RAOB height innovations for control (solid), MODIS; Arctic region


RAOB height innovations for control (solid), MODIS; South Pole


ITOVS height innovations; Arctic region


ITOVS height innovations; Antarctic region


Mean analyzed 500 hPa geopotential heights for July, 2002, for MODIS I run; NH (top left) and SH (bottom left);

RHS shows difference fields (MODIS minus control).


NCEP mean anlyzed 500 hPa heights, July 2002, Anarctica


Control minus NCEP MODIS minus NCEP


Summary:

MODIS winds complement other observations at the highest latitudes; more so in the SH than in the NH due to the current data sparsity

Consistency of data delivery is acceptable Based on independent verification and

innovation statistics, the quality of the information is acceptable

Positive contribution to forecast skill, but not where one would expect it the most

Current version of fv-DAS is hostile to high-latitude wind information


Outlook

MODIS winds experiments with new GMAO assimilation system based on GSI (next-generation EMC analysis ) Impact Background error covariance Timeliness

MODIS winds from Aqua ECMWF verification if possible

modis winds applications to nwp/data assimilation studies; fairbanks, 10/08/2003 lars peter...

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