The GSI Capability to Assimilate TRMM and GPM Hydrometeor Retrievals in HWRF Ting-Chi Wu a, Milija Zupanski a, Louie Grasso a, Paula Brown b, Chris Kummerow ab, and John Knaff c a CIRA/CSU b Department of Atmospheric Science/CSU c NOAA/Center for Satellite Applications and Research 14th Technical Review Meeting & Science Workshop on Satellite Data Assimilation May 31-June 2, Monterey, California 1

Some Facts More than 90% of all observations used in global NWP systems come from satellite. However, limitations in NWP systems and computing resources prevents 95% of collected satellite data from being assimilated… Satellite instruments do not observe physical quantities such as temperature, wind, humidity, etc. – Satellite instruments measure radiation emitted from the surface and atmosphere of the Earth. – Radiance is related to T, Q, cloud variables, etc via radiative transfer equation (e.g. CRTM) Satellite data assimilation: radiance vs. retrievals 2

Hurricane WRF (HWRF) System HWRF 2014 (v3.6a) Operational Implementation GSI: Gridpoint Statistical Interpolation HWRF employs the hybrid GSI (3DVar+Ens) static + ensemble background error covariance WRF NMM core 3

HWRF Domain (v3.6a)  The inner-most domain does not assimilate the majority of the satellite observations.  Information contained in the hurricane core is important  Conventional observations are sparse over ocean Domain (Δx)sizeDA (Hybrid 20% static + 80% ensemble Δx=50km) Conv. Obs assimilated Sat. Radiance assimilated d01 (27 km)216 x 432Sort of Clear sky only ghost d02 (9km)106 x 204Yes (H: 300km/V:600 hPa)YesClear sky only ghost d03 (3km)198 x 354Yes (H: 150km/V:600 hPa)YesNone 4

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Hurricane GPROF Transformed into 2 vertically integrated quantities: integrated solid water content (SWC) in kg m -2 integrated liquid water content (LWC) in kg m -2 solid = ice + 1/2 of mixed-phase water liquid = cloud water + rain + 1/2 of mixed-phase water Hurricane GPROF incorporates HURDAT2 for TMI/GMI: instantaneous rainfall rate hydrometeor profiles : cloud water, rain, mixed-phase, and ice The latest Goddard PROFiling (GPROF v2014) retrieves precipitation rate and vertical profiles of hydrometeors from TMI and GMI, but contains little hurricane data. 6

How to Assimilate Them? Develop and implement new observation operators to assimilate integrated SWC and integrated LWC. Two possible approaches: 1. Add hydrometeor control variables (Future Work) 2. Extend the impact to the current set of control variables in operational HWRF-GSI that includes T (temperature), P s (surface pressure), and q (specific humidity). Assumption: All water vapor in excess of the saturation is immediately condensed out. The observation operators (h solid and h liquid ) are defined as a vertical integration of water vapor mixing ratio in excess of saturation with respect to ice and liquid. 7

Observation Operators : h solid and h liquid q v : water vapor mixing ratio q si : saturation mixing ratio wrt ice q sl : saturation mixing ratio wrt liquid ρ : air mass density; f(T,P,q v ) Δz: layer thickness k: model vertical index k 0 : level where T=T 0 =273.15K k mix : level where T=T mix =253.15K Saturation vapor pressure  h solid and h liquid = f(T, P, q v ) = f(T, P s, q) 8

Single Observation Experiment The analysis increment (analysis - background) from such an experiment experiment can be used to analysis background analysis increment examine the structure of the background error covariance P f Understand how the observation information is distributed spatially among different variables. Two experiments 1-OBSSOLID and 1-OBSLIQUID Place a single observation of integrated SWC/LWC with value of 0.5 kg m -2 to the east of storm center noHybrid DA (pure 3DVar) vs. Hybrid DA (Var+Ens) i.e. 100% static vs. 20% static + 80% flow-dependent 9

noHybrid (pure 3DVar) 1-OBSSOLID (top) 1-OBSLIQUID (bottom) 1-OBSICE: maximum increment at upper troposphere 1-OBSLIQUID: maximum increment near ground increase moisture and lower temperature —> reach saturation 10

Hybrid (3DVar+Ens) 1-OBSSOLID (top) 1-OBSLIQUID (bottom) larger increments comparing to the nohybrid experiments, and extend vertically through a significant portion of troposphere Both experiments act to intensify the storm, in different degrees 11

Real Case: Hurricane Leslie (2012) ExpsObs Assimilated in ghost d02 Obs Assimilated in ghost d03 ConventionalSatelliteConventionalSatellite CTLYesClear skyYesNone AddWCYesClear skyYesIntegrated SWC + LWC First cycle starts at 2012/08/30 18 UTC for both experiments Run two-consecutive cycles We will focus on analysis from the second cycle 12

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2 nd cycle 14

HWRF Forecast from 2 nd cycle 15

Forecast Rain Rates Synthetic Satellite Image TMI PR 16

Future Work Extend current work by assimilate ATMS all-sky radiances using the operational HWRF system. See item (1) on slide 7. 17

Analysis: In general, moister and cooler air in mid to lower tropospheric layers of the hurricane core are evident in AddWC analysis, suggesting a tendency toward reaching saturation by lowering temperature and increasing moisture. Forecast: no obvious improvement in track, intensity, and size forecast. Similar results Gonzalo Possible causes of the inconclusiveness : – the analysis used to initialize an HWRF forecast is unbalanced – the existence of model errors in HWRF that are not accounted for by GSI – the absence of hydrometeor variables in the list of operational GSI control variables. Thank You Summary 18