Bereket Lebassi Habtezion Ph.D. Candidate Department of Mechanical Engineering Santa Clara University Prof. Jorge Gonzalez Advisor Department of Mechanical Engineering City College Of New York Presented at Santa Clara University Dissertation defense on 9 June 2010.
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Ph.D. Candidate
Department of Mechanical Engineering
Santa Clara University
Prof. Jorge Gonzalez
Advisor
Department of Mechanical Engineering
City College Of New York
Presented at Santa Clara University
Dissertation defense
on
9 June 2010
From NASA RESEARCH NEWS (2006), group led by James Hansen, GISS, NYC
Chase et al. ‘00; Mintz ‘84; Zhang ‘97
Current Hypothesis: Observed Calif temp trends resulted from temperaturetrends in
pgradient) trends calculated from
SCU (Maurer 2007) statistically 10km downscaled 19502000 modeled JJA temps (0C) show total warming rates that decrease to coast (dots are Calif NCDC sites & boxes are study subareas)
Result 1: Lebassi et al. (2009) J. of Climate modeled JJA temps (
Observed 19702005 CA JJA maxTemp (0C/decade)trends in SFBA & SoCAB show concurrent:
> lowelev coastalcooling & > high elev & inlandwarming
> signif levels: solid circles >99% & open circles <90%)
Results 2: Same for SFBA & Central Valley modeled JJA temps (COOLING AREAS: MARIN LOWLANDS, MONTEREY, SANTA CLARA V., LIVERMORE V., WESTERN HALF OF SACRAMENTO V.
Results 3: Temp. trends for all of California modeled JJA temps (
Tmin (Curve b) increasing faster than Tmax (Curve c)
Result 4: Combined SFBA & SoCAB 19702005 summer trends modeled JJA temps (
(oC decade1) of Tmax (Curves c)
Inland Tmaxwarming sites
Coastal Tmaxcooling sites
(a)
(b)
(c)
(d)
Result 5: Average JJA 1.4deg ERA40reanalysis SLP trends (hPa/decade) at 11 LT for 19702005

+
+
Result 6: Trend in oceanland summer SLPgradient (hPa/decade) at 11 LT for 19702005
(hPa 100km1 decade1) at 11 LT at endpoints in previous slide
Results show: pgradient increases in both areas increased sea breeze
(a) Cooling Degree Day (CDD) trend: upward due to GHG warming
More energy for cooling
(b) Heating Degree Day (HDD) trend: downward due you to GHG warming
Less energy for heating
Modeling Effort (hPa/decade) at 11 LT for 19702005
Introduction to
Regional Atmospheric Modeling System (RAMS)
Km, h: eddy diffusivity coef. for momentum & heat.
Momentum eqs for u, v & w
(1)
(2)
(3)
Latent heat & RFD
Local ∆ = Advection + pgrad + Coriolis + Turbulent Diffusion
Thermodynamic Eq for iceliquid water potentialtemp
Water Species (nspecies, e.g. vapor, ice, snow, …)
Sources & sinks via phase changes
Pressure Eq (in terms of (hPa/decade) at 11 LT for 19702005π)
(4)
(5)
(6)
(7)
Exner function π, for pressure
Ideal Gas Law for density
Poisson eq for Tv
Vertical Diffusion Coef K (hPa/decade) at 11 LT for 19702005m,h,e via TKE (e)
Shear Production Buoyancy Molec Dissipation
Sm,h,e are f(Ri)
l is mixing length
Vertical Boundary Conditions (hPa/decade) at 11 LT for 19702005
Sfc BC for T(t): RAMS uses LEAF3 “big leaf” model to solve
sfc energy balance at each sfctype,
e.g., for allurban sfcs (no veg or evaporation)
Parametervalues (needed as input in previous Eq) solve
for different urban classes
where
α Albedo
ε Emissivity
FV Vegetation Fraction
HV Vegetation/building Height
Set up of solve
RAMS simulations of SoCAB Area
Selected past (196670) & present (20012005) solve simulationperiods: have similar PDO & tempvariations largescale variability effects are eliminated
Note: ENSO summerimpacts are mainly in winter in studyarea
Simulation Determination solve
ICs and Largescale BCs (FDDA) solve
Grid Configuration solve
staggered grid
resolution
>49 levels to 31 km
+ solve
+
+
+
ModelEvaluation with Run1 ( solve current met & LU) output:
June 110, 2002; averages of 12 SoCAB METAR sites
where: blue is obs & red is closest RAMS grid point
Mean wind speeds: both at 10m Mean temps: both at 2m
model =3.1 m/s vs. obs = 2.9 m/s model = 20.2oC vs. obs = 19.3oC
ModelEvaluation (cont.) solve
a
b
c
Temp and windresults from
Large scale BC inputs into RAMS solve
(next 5 slides)
H solve
H
L
L
Now
Past
+


+
N P
H solve
H
C
C
Now
Past
Present & Past 17LT JJAAve NCEP 1000hPa T(oC)N  P solve
N  P
+
+


Present minus Past 17LT JJAAve NCEP 1000hPa ΔT(oC)T(oC)
Now solve
Past
N P
T(oC)
12 LT solve
14 LT
16 LT
Acceleration case: N > P,
so NP is in their dir (onshore)
Retardation case: P > N,
so NP is in opposite dir (offshore)
N
P
N
NP
P
P
P
NP
where:
N = current windvector (red)
P = past windvector (black)
CP = current minus past (white)
14 LT solve
12 LT
16 LT
12 LT
14 LT
16 LT
U
T
12 LT
V
14 LT
16 LT
Past solve
Now
N  P
T(oC)
Now solve
Past
NP
URBANIZATION RESULT (one slide): solve
2002 JJA 12, 14 & 16 LT Run 1 (Urban) minus Run 3 (noUrban): Temp & U (1 barb = 0.5 m/s) differences (U minus no U)
12 LT
14 LT
16 LT
T (oC)
The effects of urbanization & GHG warming on summer sea breezes in the SoCAB were studied by
> RAMS mesomet modeled PBL winds & temps
> comparison of RAMS temps with observed nearsfc values
> increased seabreezes over the ocean & coastal plain, and thus
> seabreeze induced coastalcooling over the coastal plain (whose aerial extent & magnitude matched the observations)
> UHI and a
> reduced seabreeze penetration (due to the large urbanz0)
> Lower energyuse for cooling
> Lower heatstress levels
> Lower peak O3 concentrations
> Benefits for peaktemperature sensitive agriculture
From IPCC
> Scientific questions
> Extend observational data analysis to
> Additional RAMS modeling of
> Impactanalyses of
JOURNAL PUBLICATIONS solve