Evaluation of HYCOM Upper Ocean Mixing Parameterizations S. Daniel Jacob 1, Lynn K. Shay 2, George R. Halliwell 2 and David Le Vine 3 1 GEST, UMBC/ NASA GSFC, Greenbelt, MD MPO, RSMAS, University of Miami, Miami, FL NASA GSFC, Greenbelt, MD A. Wallcraft (NRL Stennis), M. Powell (NOAA HRD), O. M. Smedstad Partial Funding from NOAA Joint Hurricane Testbed, NSF US Weather Research Program

Upper Ocean Mixing and Hurricane Intensity Based on Observational Analysis (Jacob et al., JPO 2000) –Entrainment is the dominant mechanism in the mixed layer cooling. –Mixed layer heat and mass budgets strongly depend upon the entrainment scheme used. Numerical Modeling (Jacob and Shay, JPO, 2003): –Measured and simulated quantities based on different hypothesis are used to compute entrainment mixing. –Bulk schemes in using MICOM

MOVIE 1 Gaspar KT PRT DDF

GILBERT UPPER OCEAN RESPONSE EXPERIMENT Shay et al. JGR 1992

MODEL-DATA COMPARISON ALL STORM WAKE1 WAKE2

OBJECTIVES Mixing Schemes Hybrid Coordinate Ocean Model Evaluate higher order turbulence closure schemes for hurricane forcing based on the data acquired during the three storms Precipitation Effects TRMM measurements Large rain-rates of more than 15 mm/hr have been observed. Mixing effects Heat Fluxes

Data Resources Data were acquired in 2002 as part of the NSF USWRP in two additional storms Isidore and Lili in the Caribbean and Gulf of Mexico Region. Overall, number of profiles available for comparison include: 339 Temperature Profiles from AXBTs, AXCPs and AXCTDs 178 Current Profiles from AXCPs 134 Salinity Profiles from AXCTD Other data includes Aircraft acquired atmospheric forcing data for specifying boundary layer forcing 1988 year day 200 data for model initialization for Gilbert

Hurricane Gilbert Case Configuration –Domain: Gulf of Mexico –Resolution: 0.07 –20/22/50 Levels/ Layers –Closed Boundaries Initial Conditions –Quiescent and Realistic –No Precip vs Precip for Quiescent conditions

TEMPERATURE-SALINITY DIAGRAM

WIND FIELD STRUCTURE 16 SEP 88 06UTC

Hycom Q Movie Gaspar MY2.5 KPP PWP

2 R max

TEMPERATURE-SALINITY DIAGRAM Case E Case E GCW Case C Case Q

1988 Yearday 200 to 258 with COADS climatological forcing with KT scheme Center position is accurate within 0.3°, Strength consistent with data MICOMHYCOM

KPP PWP MYGISS

PRECIP STRUCTURE 16 SEP 88 06UTC mm/day

OCEAN RESPONSE at 06 UTC, 16 SEP 1988 KPP NO PRECIP KPP WITH PRECIP KPP MLTMLS

ΔOCEAN RESPONSE at 06 UTC, 16 SEP 1988 ΔMLT KPPPWP MY2.5GISS

ΔOCEAN RESPONSE at 06 UTC, 16 SEP 1988 ΔMLS KPPPWP MY2.5GISS

2 R max No PrecipPrecip

2 R max PWP

WIND FIELD STRUCTURE 22 SEP 02 12UTC

KPP GISS

SUMMARY HYCOM simulations also show a strong oceanic ML budget dependence on the entrainment closure scheme in the directly forced region. – Implications for storm intensity. Initial comparisons with data indicates better performance of KPP and MY2.5 for the Gilbert case. Comparisons will be performed with 50 levels/layers and also in Isidore and Lili cases. The PWP scheme simulates coolest and most saline mixed layer without precipitation. Due to the stabilizing effect of precipitation, mixed layer cooling is reduced by ~0.5° C when rainfall is added. A freshening of 0.25 PSU is seen in simulations with added precipitation. This counteracts mixing of more saline water from below.

Vertical Structure (KPP)